contrib/bind9/doc/arm/Bv9ARM.ch06.html

   1 <!--
   2  - Copyright (C) 2004-2015 Internet Systems Consortium, Inc. ("ISC")
   3  - Copyright (C) 2000-2003 Internet Software Consortium.
   4  -
   5  - Permission to use, copy, modify, and/or distribute this software for any
   6  - purpose with or without fee is hereby granted, provided that the above
   7  - copyright notice and this permission notice appear in all copies.
   8  -
   9  - THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
  10  - REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
  11  - AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
  12  - INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
  13  - LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
  14  - OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
  15  - PERFORMANCE OF THIS SOFTWARE.
  16 -->
  17 <html>
  18 <head>
  19 <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
  20 <title>Chapter 6. BIND 9 Configuration Reference</title>
  21 <meta name="generator" content="DocBook XSL Stylesheets V1.78.1">
  22 <link rel="home" href="Bv9ARM.html" title="BIND 9 Administrator Reference Manual">
  23 <link rel="up" href="Bv9ARM.html" title="BIND 9 Administrator Reference Manual">
  24 <link rel="prev" href="Bv9ARM.ch05.html" title="Chapter 5. The BIND 9 Lightweight Resolver">
  25 <link rel="next" href="Bv9ARM.ch07.html" title="Chapter 7. BIND 9 Security Considerations">
  26 </head>
  27 <body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF">
  28 <div class="navheader">
  29 <table width="100%" summary="Navigation header">
  30 <tr><th colspan="3" align="center">Chapter 6. <acronym class="acronym">BIND</acronym> 9 Configuration Reference</th></tr>
  31 <tr>
  32 <td width="20%" align="left">
  33 <a accesskey="p" href="Bv9ARM.ch05.html">Prev</a> </td>
  34 <th width="60%" align="center"> </th>
  35 <td width="20%" align="right"> <a accesskey="n" href="Bv9ARM.ch07.html">Next</a>
  36 </td>
  37 </tr>
  38 </table>
  39 <hr>
  40 </div>
  41 <div class="chapter">
  42 <div class="titlepage"><div><div><h1 class="title">
  43 <a name="Bv9ARM.ch06"></a>Chapter 6. <acronym class="acronym">BIND</acronym> 9 Configuration Reference</h1></div></div></div>
  44 <div class="toc">
  45 <p><b>Table of Contents</b></p>
  46 <dl class="toc">
  47 <dt><span class="section"><a href="Bv9ARM.ch06.html#configuration_file_elements">Configuration File Elements</a></span></dt>
  48 <dd><dl>
  49 <dt><span class="section"><a href="Bv9ARM.ch06.html#address_match_lists">Address Match Lists</a></span></dt>
  50 <dt><span class="section"><a href="Bv9ARM.ch06.html#comment_syntax">Comment Syntax</a></span></dt>
  51 </dl></dd>
  52 <dt><span class="section"><a href="Bv9ARM.ch06.html#Configuration_File_Grammar">Configuration File Grammar</a></span></dt>
  53 <dd><dl>
  54 <dt><span class="section"><a href="Bv9ARM.ch06.html#acl_grammar"><span class="command"><strong>acl</strong></span> Statement Grammar</a></span></dt>
  55 <dt><span class="section"><a href="Bv9ARM.ch06.html#acl"><span class="command"><strong>acl</strong></span> Statement Definition and
  56           Usage</a></span></dt>
  57 <dt><span class="section"><a href="Bv9ARM.ch06.html#controls_grammar"><span class="command"><strong>controls</strong></span> Statement Grammar</a></span></dt>
  58 <dt><span class="section"><a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage"><span class="command"><strong>controls</strong></span> Statement Definition and
  59           Usage</a></span></dt>
  60 <dt><span class="section"><a href="Bv9ARM.ch06.html#include_grammar"><span class="command"><strong>include</strong></span> Statement Grammar</a></span></dt>
  61 <dt><span class="section"><a href="Bv9ARM.ch06.html#include_statement"><span class="command"><strong>include</strong></span> Statement Definition and Usage</a></span></dt>
  62 <dt><span class="section"><a href="Bv9ARM.ch06.html#key_grammar"><span class="command"><strong>key</strong></span> Statement Grammar</a></span></dt>
  63 <dt><span class="section"><a href="Bv9ARM.ch06.html#key_statement"><span class="command"><strong>key</strong></span> Statement Definition and Usage</a></span></dt>
  64 <dt><span class="section"><a href="Bv9ARM.ch06.html#logging_grammar"><span class="command"><strong>logging</strong></span> Statement Grammar</a></span></dt>
  65 <dt><span class="section"><a href="Bv9ARM.ch06.html#logging_statement"><span class="command"><strong>logging</strong></span> Statement Definition and Usage</a></span></dt>
  66 <dt><span class="section"><a href="Bv9ARM.ch06.html#lwres_grammar"><span class="command"><strong>lwres</strong></span> Statement Grammar</a></span></dt>
  67 <dt><span class="section"><a href="Bv9ARM.ch06.html#lwres_statement"><span class="command"><strong>lwres</strong></span> Statement Definition and Usage</a></span></dt>
  68 <dt><span class="section"><a href="Bv9ARM.ch06.html#masters_grammar"><span class="command"><strong>masters</strong></span> Statement Grammar</a></span></dt>
  69 <dt><span class="section"><a href="Bv9ARM.ch06.html#masters_statement"><span class="command"><strong>masters</strong></span> Statement Definition and
  70           Usage</a></span></dt>
  71 <dt><span class="section"><a href="Bv9ARM.ch06.html#options_grammar"><span class="command"><strong>options</strong></span> Statement Grammar</a></span></dt>
  72 <dt><span class="section"><a href="Bv9ARM.ch06.html#options"><span class="command"><strong>options</strong></span> Statement Definition and
  73           Usage</a></span></dt>
  74 <dt><span class="section"><a href="Bv9ARM.ch06.html#server_statement_grammar"><span class="command"><strong>server</strong></span> Statement Grammar</a></span></dt>
  75 <dt><span class="section"><a href="Bv9ARM.ch06.html#server_statement_definition_and_usage"><span class="command"><strong>server</strong></span> Statement Definition and
  76             Usage</a></span></dt>
  77 <dt><span class="section"><a href="Bv9ARM.ch06.html#statschannels"><span class="command"><strong>statistics-channels</strong></span> Statement Grammar</a></span></dt>
  78 <dt><span class="section"><a href="Bv9ARM.ch06.html#statistics_channels"><span class="command"><strong>statistics-channels</strong></span> Statement Definition and
  79             Usage</a></span></dt>
  80 <dt><span class="section"><a href="Bv9ARM.ch06.html#trusted-keys"><span class="command"><strong>trusted-keys</strong></span> Statement Grammar</a></span></dt>
  81 <dt><span class="section"><a href="Bv9ARM.ch06.html#trusted_keys"><span class="command"><strong>trusted-keys</strong></span> Statement Definition
  82             and Usage</a></span></dt>
  83 <dt><span class="section"><a href="Bv9ARM.ch06.html#managed_keys"><span class="command"><strong>managed-keys</strong></span> Statement Grammar</a></span></dt>
  84 <dt><span class="section"><a href="Bv9ARM.ch06.html#managed-keys"><span class="command"><strong>managed-keys</strong></span> Statement Definition
  85             and Usage</a></span></dt>
  86 <dt><span class="section"><a href="Bv9ARM.ch06.html#view_statement_grammar"><span class="command"><strong>view</strong></span> Statement Grammar</a></span></dt>
  87 <dt><span class="section"><a href="Bv9ARM.ch06.html#view_statement"><span class="command"><strong>view</strong></span> Statement Definition and Usage</a></span></dt>
  88 <dt><span class="section"><a href="Bv9ARM.ch06.html#zone_statement_grammar"><span class="command"><strong>zone</strong></span>
  89             Statement Grammar</a></span></dt>
  90 <dt><span class="section"><a href="Bv9ARM.ch06.html#zone_statement"><span class="command"><strong>zone</strong></span> Statement Definition and Usage</a></span></dt>
  91 </dl></dd>
  92 <dt><span class="section"><a href="Bv9ARM.ch06.html#zone_file">Zone File</a></span></dt>
  93 <dd><dl>
  94 <dt><span class="section"><a href="Bv9ARM.ch06.html#types_of_resource_records_and_when_to_use_them">Types of Resource Records and When to Use Them</a></span></dt>
  95 <dt><span class="section"><a href="Bv9ARM.ch06.html#mx_records">Discussion of MX Records</a></span></dt>
  96 <dt><span class="section"><a href="Bv9ARM.ch06.html#Setting_TTLs">Setting TTLs</a></span></dt>
  97 <dt><span class="section"><a href="Bv9ARM.ch06.html#ipv4_reverse">Inverse Mapping in IPv4</a></span></dt>
  98 <dt><span class="section"><a href="Bv9ARM.ch06.html#zone_directives">Other Zone File Directives</a></span></dt>
  99 <dt><span class="section"><a href="Bv9ARM.ch06.html#generate_directive"><acronym class="acronym">BIND</acronym> Master File Extension: the  <span class="command"><strong>$GENERATE</strong></span> Directive</a></span></dt>
 100 <dt><span class="section"><a href="Bv9ARM.ch06.html#zonefile_format">Additional File Formats</a></span></dt>
 101 </dl></dd>
 102 <dt><span class="section"><a href="Bv9ARM.ch06.html#statistics">BIND9 Statistics</a></span></dt>
 103 <dd><dl>
 104 <dt><span class="section"><a href="Bv9ARM.ch06.html#statsfile">The Statistics File</a></span></dt>
 105 <dt><span class="section"><a href="Bv9ARM.ch06.html#statistics_counters">Statistics Counters</a></span></dt>
 106 </dl></dd>
 107 </dl>
 108 </div>
 109 <p>
 110       <acronym class="acronym">BIND</acronym> 9 configuration is broadly similar
 111       to <acronym class="acronym">BIND</acronym> 8; however, there are a few new
 112       areas
 113       of configuration, such as views. <acronym class="acronym">BIND</acronym>
 114       8 configuration files should work with few alterations in <acronym class="acronym">BIND</acronym>
 115       9, although more complex configurations should be reviewed to check
 116       if they can be more efficiently implemented using the new features
 117       found in <acronym class="acronym">BIND</acronym> 9.
 118     </p>
 119 <p>
 120       <acronym class="acronym">BIND</acronym> 4 configuration files can be
 121       converted to the new format
 122       using the shell script
 123       <code class="filename">contrib/named-bootconf/named-bootconf.sh</code>.
 124     </p>
 125 <div class="section">
 126 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
 127 <a name="configuration_file_elements"></a>Configuration File Elements</h2></div></div></div>
 128 <p>
 129         Following is a list of elements used throughout the <acronym class="acronym">BIND</acronym> configuration
 130         file documentation:
 131       </p>
 132 <div class="informaltable"><table border="1">
 133 <colgroup>
 134 <col width="1.855in" class="1">
 135 <col width="3.770in" class="2">
 136 </colgroup>
 137 <tbody>
 138 <tr>
 139 <td>
 140                 <p>
 141                   <code class="varname">acl_name</code>
 142                 </p>
 143               </td>
 144 <td>
 145                 <p>
 146                   The name of an <code class="varname">address_match_list</code> as
 147                   defined by the <span class="command"><strong>acl</strong></span> statement.
 148                 </p>
 149               </td>
 150 </tr>
 151 <tr>
 152 <td>
 153                 <p>
 154                   <code class="varname">address_match_list</code>
 155                 </p>
 156               </td>
 157 <td>
 158                 <p>
 159                   A list of one or more
 160                   <code class="varname">ip_addr</code>,
 161                   <code class="varname">ip_prefix</code>, <code class="varname">key_id</code>,
 162                   or <code class="varname">acl_name</code> elements, see
 163                   <a class="xref" href="Bv9ARM.ch06.html#address_match_lists" title="Address Match Lists">the section called &#8220;Address Match Lists&#8221;</a>.
 164                 </p>
 165               </td>
 166 </tr>
 167 <tr>
 168 <td>
 169                 <p>
 170                   <code class="varname">masters_list</code>
 171                 </p>
 172               </td>
 173 <td>
 174                 <p>
 175                   A named list of one or more <code class="varname">ip_addr</code>
 176                   with optional <code class="varname">key_id</code> and/or
 177                   <code class="varname">ip_port</code>.
 178                   A <code class="varname">masters_list</code> may include other
 179                   <code class="varname">masters_lists</code>.
 180                 </p>
 181               </td>
 182 </tr>
 183 <tr>
 184 <td>
 185                 <p>
 186                   <code class="varname">domain_name</code>
 187                 </p>
 188               </td>
 189 <td>
 190                 <p>
 191                   A quoted string which will be used as
 192                   a DNS name, for example "<code class="literal">my.test.domain</code>".
 193                 </p>
 194               </td>
 195 </tr>
 196 <tr>
 197 <td>
 198                 <p>
 199                   <code class="varname">namelist</code>
 200                 </p>
 201               </td>
 202 <td>
 203                 <p>
 204                   A list of one or more <code class="varname">domain_name</code>
 205                   elements.
 206                 </p>
 207               </td>
 208 </tr>
 209 <tr>
 210 <td>
 211                 <p>
 212                   <code class="varname">dotted_decimal</code>
 213                 </p>
 214               </td>
 215 <td>
 216                 <p>
 217                   One to four integers valued 0 through
 218                   255 separated by dots (`.'), such as <span class="command"><strong>123</strong></span>,
 219                   <span class="command"><strong>45.67</strong></span> or <span class="command"><strong>89.123.45.67</strong></span>.
 220                 </p>
 221               </td>
 222 </tr>
 223 <tr>
 224 <td>
 225                 <p>
 226                   <code class="varname">ip4_addr</code>
 227                 </p>
 228               </td>
 229 <td>
 230                 <p>
 231                   An IPv4 address with exactly four elements
 232                   in <code class="varname">dotted_decimal</code> notation.
 233                 </p>
 234               </td>
 235 </tr>
 236 <tr>
 237 <td>
 238                 <p>
 239                   <code class="varname">ip6_addr</code>
 240                 </p>
 241               </td>
 242 <td>
 243                 <p>
 244                   An IPv6 address, such as <span class="command"><strong>2001:db8::1234</strong></span>.
 245                   IPv6 scoped addresses that have ambiguity on their
 246                   scope zones must be disambiguated by an appropriate
 247                   zone ID with the percent character (`%') as
 248                   delimiter.  It is strongly recommended to use
 249                   string zone names rather than numeric identifiers,
 250                   in order to be robust against system configuration
 251                   changes.  However, since there is no standard
 252                   mapping for such names and identifier values,
 253                   currently only interface names as link identifiers
 254                   are supported, assuming one-to-one mapping between
 255                   interfaces and links.  For example, a link-local
 256                   address <span class="command"><strong>fe80::1</strong></span> on the link
 257                   attached to the interface <span class="command"><strong>ne0</strong></span>
 258                   can be specified as <span class="command"><strong>fe80::1%ne0</strong></span>.
 259                   Note that on most systems link-local addresses
 260                   always have the ambiguity, and need to be
 261                   disambiguated.
 262                 </p>
 263               </td>
 264 </tr>
 265 <tr>
 266 <td>
 267                 <p>
 268                   <code class="varname">ip_addr</code>
 269                 </p>
 270               </td>
 271 <td>
 272                 <p>
 273                   An <code class="varname">ip4_addr</code> or <code class="varname">ip6_addr</code>.
 274                 </p>
 275               </td>
 276 </tr>
 277 <tr>
 278 <td>
 279                 <p>
 280                   <code class="varname">ip_port</code>
 281                 </p>
 282               </td>
 283 <td>
 284                 <p>
 285                   An IP port <code class="varname">number</code>.
 286                   The <code class="varname">number</code> is limited to 0
 287                   through 65535, with values
 288                   below 1024 typically restricted to use by processes running
 289                   as root.
 290                   In some cases, an asterisk (`*') character can be used as a
 291                   placeholder to
 292                   select a random high-numbered port.
 293                 </p>
 294               </td>
 295 </tr>
 296 <tr>
 297 <td>
 298                 <p>
 299                   <code class="varname">ip_prefix</code>
 300                 </p>
 301               </td>
 302 <td>
 303                 <p>
 304                   An IP network specified as an <code class="varname">ip_addr</code>,
 305                   followed by a slash (`/') and then the number of bits in the
 306                   netmask.
 307                   Trailing zeros in a <code class="varname">ip_addr</code>
 308                   may omitted.
 309                   For example, <span class="command"><strong>127/8</strong></span> is the
 310                   network <span class="command"><strong>127.0.0.0</strong></span> with
 311                   netmask <span class="command"><strong>255.0.0.0</strong></span> and <span class="command"><strong>1.2.3.0/28</strong></span> is
 312                   network <span class="command"><strong>1.2.3.0</strong></span> with netmask <span class="command"><strong>255.255.255.240</strong></span>.
 313                 </p>
 314                 <p>
 315                   When specifying a prefix involving a IPv6 scoped address
 316                   the scope may be omitted.  In that case the prefix will
 317                   match packets from any scope.
 318                 </p>
 319               </td>
 320 </tr>
 321 <tr>
 322 <td>
 323                 <p>
 324                   <code class="varname">key_id</code>
 325                 </p>
 326               </td>
 327 <td>
 328                 <p>
 329                   A <code class="varname">domain_name</code> representing
 330                   the name of a shared key, to be used for transaction
 331                   security.
 332                 </p>
 333               </td>
 334 </tr>
 335 <tr>
 336 <td>
 337                 <p>
 338                   <code class="varname">key_list</code>
 339                 </p>
 340               </td>
 341 <td>
 342                 <p>
 343                   A list of one or more
 344                   <code class="varname">key_id</code>s,
 345                   separated by semicolons and ending with a semicolon.
 346                 </p>
 347               </td>
 348 </tr>
 349 <tr>
 350 <td>
 351                 <p>
 352                   <code class="varname">number</code>
 353                 </p>
 354               </td>
 355 <td>
 356                 <p>
 357                   A non-negative 32-bit integer
 358                   (i.e., a number between 0 and 4294967295, inclusive).
 359                   Its acceptable value might further
 360                   be limited by the context in which it is used.
 361                 </p>
 362               </td>
 363 </tr>
 364 <tr>
 365 <td>
 366                 <p>
 367                   <code class="varname">path_name</code>
 368                 </p>
 369               </td>
 370 <td>
 371                 <p>
 372                   A quoted string which will be used as
 373                   a pathname, such as <code class="filename">zones/master/my.test.domain</code>.
 374                 </p>
 375               </td>
 376 </tr>
 377 <tr>
 378 <td>
 379                 <p>
 380                   <code class="varname">port_list</code>
 381                 </p>
 382               </td>
 383 <td>
 384                 <p>
 385                   A list of an <code class="varname">ip_port</code> or a port
 386                   range.
 387                   A port range is specified in the form of
 388                   <strong class="userinput"><code>range</code></strong> followed by
 389                   two <code class="varname">ip_port</code>s,
 390                   <code class="varname">port_low</code> and
 391                   <code class="varname">port_high</code>, which represents
 392                   port numbers from <code class="varname">port_low</code> through
 393                   <code class="varname">port_high</code>, inclusive.
 394                   <code class="varname">port_low</code> must not be larger than
 395                   <code class="varname">port_high</code>.
 396                   For example,
 397                   <strong class="userinput"><code>range 1024 65535</code></strong> represents
 398                   ports from 1024 through 65535.
 399                   In either case an asterisk (`*') character is not
 400                   allowed as a valid <code class="varname">ip_port</code>.
 401                 </p>
 402               </td>
 403 </tr>
 404 <tr>
 405 <td>
 406                 <p>
 407                   <code class="varname">size_spec</code>
 408                 </p>
 409               </td>
 410 <td>
 411                 <p>
 412                   A 64-bit unsigned integer, or the keywords
 413                   <strong class="userinput"><code>unlimited</code></strong> or
 414                   <strong class="userinput"><code>default</code></strong>.
 415                 </p>
 416                 <p>
 417                   Integers may take values
 418                   0 &lt;= value &lt;= 18446744073709551615, though
 419                   certain parameters
 420                   (such as <span class="command"><strong>max-journal-size</strong></span>) may
 421                   use a more limited range within these extremes.
 422                   In most cases, setting a value to 0 does not
 423                   literally mean zero; it means "undefined" or
 424                   "as big as possible", depending on the context.
 425                   See the explanations of particular parameters
 426                   that use <code class="varname">size_spec</code>
 427                   for details on how they interpret its use.
 428                 </p>
 429                 <p>
 430                   Numeric values can optionally be followed by a
 431                   scaling factor:
 432                   <strong class="userinput"><code>K</code></strong> or <strong class="userinput"><code>k</code></strong>
 433                   for kilobytes,
 434                   <strong class="userinput"><code>M</code></strong> or <strong class="userinput"><code>m</code></strong>
 435                   for megabytes, and
 436                   <strong class="userinput"><code>G</code></strong> or <strong class="userinput"><code>g</code></strong>
 437                   for gigabytes, which scale by 1024, 1024*1024, and
 438                   1024*1024*1024 respectively.
 439                 </p>
 440                 <p>
 441                   <code class="varname">unlimited</code> generally means
 442                   "as big as possible", though in certain contexts,
 443                   (including <code class="option">max-cache-size</code>), it may
 444                   mean the largest possible 32-bit unsigned integer
 445                   (0xffffffff); this distinction can be important when
 446                   dealing with larger quantities.
 447                   <code class="varname">unlimited</code> is usually the best way
 448                   to safely set a very large number.
 449                 </p>
 450                 <p>
 451                   <code class="varname">default</code>
 452                   uses the limit that was in force when the server was started.
 453                 </p>
 454               </td>
 455 </tr>
 456 <tr>
 457 <td>
 458                 <p>
 459                   <code class="varname">yes_or_no</code>
 460                 </p>
 461               </td>
 462 <td>
 463                 <p>
 464                   Either <strong class="userinput"><code>yes</code></strong> or <strong class="userinput"><code>no</code></strong>.
 465                   The words <strong class="userinput"><code>true</code></strong> and <strong class="userinput"><code>false</code></strong> are
 466                   also accepted, as are the numbers <strong class="userinput"><code>1</code></strong>
 467                   and <strong class="userinput"><code>0</code></strong>.
 468                 </p>
 469               </td>
 470 </tr>
 471 <tr>
 472 <td>
 473                 <p>
 474                   <code class="varname">dialup_option</code>
 475                 </p>
 476               </td>
 477 <td>
 478                 <p>
 479                   One of <strong class="userinput"><code>yes</code></strong>,
 480                   <strong class="userinput"><code>no</code></strong>, <strong class="userinput"><code>notify</code></strong>,
 481                   <strong class="userinput"><code>notify-passive</code></strong>, <strong class="userinput"><code>refresh</code></strong> or
 482                   <strong class="userinput"><code>passive</code></strong>.
 483                   When used in a zone, <strong class="userinput"><code>notify-passive</code></strong>,
 484                   <strong class="userinput"><code>refresh</code></strong>, and <strong class="userinput"><code>passive</code></strong>
 485                   are restricted to slave and stub zones.
 486                 </p>
 487               </td>
 488 </tr>
 489 </tbody>
 490 </table></div>
 491 <div class="section">
 492 <div class="titlepage"><div><div><h3 class="title">
 493 <a name="address_match_lists"></a>Address Match Lists</h3></div></div></div>
 494 <div class="section">
 495 <div class="titlepage"><div><div><h4 class="title">
 496 <a name="id-1.7.4.4.2"></a>Syntax</h4></div></div></div>
 497 <pre class="programlisting"><code class="varname">address_match_list</code> = address_match_list_element ;
 498   [<span class="optional"> address_match_list_element; ... </span>]
 499 <code class="varname">address_match_list_element</code> = [<span class="optional"> ! </span>] (ip_address [<span class="optional">/length</span>] |
 500    key key_id | acl_name | { address_match_list } )
 501 </pre>
 502 </div>
 503 <div class="section">
 504 <div class="titlepage"><div><div><h4 class="title">
 505 <a name="id-1.7.4.4.3"></a>Definition and Usage</h4></div></div></div>
 506 <p>
 507             Address match lists are primarily used to determine access
 508             control for various server operations. They are also used in
 509             the <span class="command"><strong>listen-on</strong></span> and <span class="command"><strong>sortlist</strong></span>
 510             statements. The elements which constitute an address match
 511             list can be any of the following:
 512           </p>
 513 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
 514 <li class="listitem">an IP address (IPv4 or IPv6)</li>
 515 <li class="listitem">an IP prefix (in `/' notation)</li>
 516 <li class="listitem">
 517                 a key ID, as defined by the <span class="command"><strong>key</strong></span>
 518                 statement
 519               </li>
 520 <li class="listitem">the name of an address match list defined with
 521                 the <span class="command"><strong>acl</strong></span> statement
 522               </li>
 523 <li class="listitem">a nested address match list enclosed in braces</li>
 524 </ul></div>
 525 <p>
 526             Elements can be negated with a leading exclamation mark (`!'),
 527             and the match list names "any", "none", "localhost", and
 528             "localnets" are predefined. More information on those names
 529             can be found in the description of the acl statement.
 530           </p>
 531 <p>
 532             The addition of the key clause made the name of this syntactic
 533             element something of a misnomer, since security keys can be used
 534             to validate access without regard to a host or network address.
 535             Nonetheless, the term "address match list" is still used
 536             throughout the documentation.
 537           </p>
 538 <p>
 539             When a given IP address or prefix is compared to an address
 540             match list, the comparison takes place in approximately O(1)
 541             time.  However, key comparisons require that the list of keys
 542             be traversed until a matching key is found, and therefore may
 543             be somewhat slower.
 544           </p>
 545 <p>
 546             The interpretation of a match depends on whether the list is being
 547             used for access control, defining <span class="command"><strong>listen-on</strong></span> ports, or in a
 548             <span class="command"><strong>sortlist</strong></span>, and whether the element was negated.
 549           </p>
 550 <p>
 551             When used as an access control list, a non-negated match
 552             allows access and a negated match denies access. If
 553             there is no match, access is denied. The clauses
 554             <span class="command"><strong>allow-notify</strong></span>,
 555             <span class="command"><strong>allow-recursion</strong></span>,
 556             <span class="command"><strong>allow-recursion-on</strong></span>,
 557             <span class="command"><strong>allow-query</strong></span>,
 558             <span class="command"><strong>allow-query-on</strong></span>,
 559             <span class="command"><strong>allow-query-cache</strong></span>,
 560             <span class="command"><strong>allow-query-cache-on</strong></span>,
 561             <span class="command"><strong>allow-transfer</strong></span>,
 562             <span class="command"><strong>allow-update</strong></span>,
 563             <span class="command"><strong>allow-update-forwarding</strong></span>, and
 564             <span class="command"><strong>blackhole</strong></span> all use address match
 565             lists.  Similarly, the <span class="command"><strong>listen-on</strong></span> option will cause the
 566             server to refuse queries on any of the machine's
 567             addresses which do not match the list.
 568           </p>
 569 <p>
 570             Order of insertion is significant.  If more than one element
 571             in an ACL is found to match a given IP address or prefix,
 572             preference will be given to the one that came
 573             <span class="emphasis"><em>first</em></span> in the ACL definition.
 574             Because of this first-match behavior, an element that
 575             defines a subset of another element in the list should
 576             come before the broader element, regardless of whether
 577             either is negated. For example, in
 578             <span class="command"><strong>1.2.3/24; ! 1.2.3.13;</strong></span>
 579             the 1.2.3.13 element is completely useless because the
 580             algorithm will match any lookup for 1.2.3.13 to the 1.2.3/24
 581             element.  Using <span class="command"><strong>! 1.2.3.13; 1.2.3/24</strong></span> fixes
 582             that problem by having 1.2.3.13 blocked by the negation, but
 583             all other 1.2.3.* hosts fall through.
 584           </p>
 585 </div>
 586 </div>
 587 <div class="section">
 588 <div class="titlepage"><div><div><h3 class="title">
 589 <a name="comment_syntax"></a>Comment Syntax</h3></div></div></div>
 590 <p>
 591           The <acronym class="acronym">BIND</acronym> 9 comment syntax allows for
 592           comments to appear
 593           anywhere that whitespace may appear in a <acronym class="acronym">BIND</acronym> configuration
 594           file. To appeal to programmers of all kinds, they can be written
 595           in the C, C++, or shell/perl style.
 596         </p>
 597 <div class="section">
 598 <div class="titlepage"><div><div><h4 class="title">
 599 <a name="id-1.7.4.5.3"></a>Syntax</h4></div></div></div>
 600 <p>
 601             </p>
 602 <pre class="programlisting">/* This is a <acronym class="acronym">BIND</acronym> comment as in C */</pre>
 603 <p>
 604             </p>
 605 <pre class="programlisting">// This is a <acronym class="acronym">BIND</acronym> comment as in C++</pre>
 606 <p>
 607             </p>
 608 <pre class="programlisting"># This is a <acronym class="acronym">BIND</acronym> comment as in common UNIX shells
 609 # and perl</pre>
 610 <p>
 611           </p>
 612 </div>
 613 <div class="section">
 614 <div class="titlepage"><div><div><h4 class="title">
 615 <a name="id-1.7.4.5.4"></a>Definition and Usage</h4></div></div></div>
 616 <p>
 617             Comments may appear anywhere that whitespace may appear in
 618             a <acronym class="acronym">BIND</acronym> configuration file.
 619           </p>
 620 <p>
 621             C-style comments start with the two characters /* (slash,
 622             star) and end with */ (star, slash). Because they are completely
 623             delimited with these characters, they can be used to comment only
 624             a portion of a line or to span multiple lines.
 625           </p>
 626 <p>
 627             C-style comments cannot be nested. For example, the following
 628             is not valid because the entire comment ends with the first */:
 629           </p>
 630 <p>
 631
 632 </p>
 633 <pre class="programlisting">/* This is the start of a comment.
 634    This is still part of the comment.
 635 /* This is an incorrect attempt at nesting a comment. */
 636    This is no longer in any comment. */
 637 </pre>
 638 <p>
 639
 640           </p>
 641 <p>
 642             C++-style comments start with the two characters // (slash,
 643             slash) and continue to the end of the physical line. They cannot
 644             be continued across multiple physical lines; to have one logical
 645             comment span multiple lines, each line must use the // pair.
 646             For example:
 647           </p>
 648 <p>
 649
 650 </p>
 651 <pre class="programlisting">// This is the start of a comment.  The next line
 652 // is a new comment, even though it is logically
 653 // part of the previous comment.
 654 </pre>
 655 <p>
 656
 657           </p>
 658 <p>
 659             Shell-style (or perl-style, if you prefer) comments start
 660             with the character <code class="literal">#</code> (number sign)
 661             and continue to the end of the
 662             physical line, as in C++ comments.
 663             For example:
 664           </p>
 665 <p>
 666
 667 </p>
 668 <pre class="programlisting"># This is the start of a comment.  The next line
 669 # is a new comment, even though it is logically
 670 # part of the previous comment.
 671 </pre>
 672 <p>
 673
 674           </p>
 675 <div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
 676 <h3 class="title">Warning</h3>
 677 <p>
 678               You cannot use the semicolon (`;') character
 679               to start a comment such as you would in a zone file. The
 680               semicolon indicates the end of a configuration
 681               statement.
 682             </p>
 683 </div>
 684 </div>
 685 </div>
 686 </div>
 687 <div class="section">
 688 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
 689 <a name="Configuration_File_Grammar"></a>Configuration File Grammar</h2></div></div></div>
 690 <p>
 691         A <acronym class="acronym">BIND</acronym> 9 configuration consists of
 692         statements and comments.
 693         Statements end with a semicolon. Statements and comments are the
 694         only elements that can appear without enclosing braces. Many
 695         statements contain a block of sub-statements, which are also
 696         terminated with a semicolon.
 697       </p>
 698 <p>
 699         The following statements are supported:
 700       </p>
 701 <div class="informaltable"><table border="1">
 702 <colgroup>
 703 <col width="1.336in" class="1">
 704 <col width="3.778in" class="2">
 705 </colgroup>
 706 <tbody>
 707 <tr>
 708 <td>
 709                 <p><span class="command"><strong>acl</strong></span></p>
 710               </td>
 711 <td>
 712                 <p>
 713                   defines a named IP address
 714                   matching list, for access control and other uses.
 715                 </p>
 716               </td>
 717 </tr>
 718 <tr>
 719 <td>
 720                 <p><span class="command"><strong>controls</strong></span></p>
 721               </td>
 722 <td>
 723                 <p>
 724                   declares control channels to be used
 725                   by the <span class="command"><strong>rndc</strong></span> utility.
 726                 </p>
 727               </td>
 728 </tr>
 729 <tr>
 730 <td>
 731                 <p><span class="command"><strong>include</strong></span></p>
 732               </td>
 733 <td>
 734                 <p>
 735                   includes a file.
 736                 </p>
 737               </td>
 738 </tr>
 739 <tr>
 740 <td>
 741                 <p><span class="command"><strong>key</strong></span></p>
 742               </td>
 743 <td>
 744                 <p>
 745                   specifies key information for use in
 746                   authentication and authorization using TSIG.
 747                 </p>
 748               </td>
 749 </tr>
 750 <tr>
 751 <td>
 752                 <p><span class="command"><strong>logging</strong></span></p>
 753               </td>
 754 <td>
 755                 <p>
 756                   specifies what the server logs, and where
 757                   the log messages are sent.
 758                 </p>
 759               </td>
 760 </tr>
 761 <tr>
 762 <td>
 763                 <p><span class="command"><strong>lwres</strong></span></p>
 764               </td>
 765 <td>
 766                 <p>
 767                   configures <span class="command"><strong>named</strong></span> to
 768                   also act as a light-weight resolver daemon (<span class="command"><strong>lwresd</strong></span>).
 769                 </p>
 770               </td>
 771 </tr>
 772 <tr>
 773 <td>
 774                 <p><span class="command"><strong>masters</strong></span></p>
 775               </td>
 776 <td>
 777                 <p>
 778                   defines a named masters list for
 779                   inclusion in stub and slave zones'
 780                   <span class="command"><strong>masters</strong></span> or
 781                   <span class="command"><strong>also-notify</strong></span> lists.
 782                 </p>
 783               </td>
 784 </tr>
 785 <tr>
 786 <td>
 787                 <p><span class="command"><strong>options</strong></span></p>
 788               </td>
 789 <td>
 790                 <p>
 791                   controls global server configuration
 792                   options and sets defaults for other statements.
 793                 </p>
 794               </td>
 795 </tr>
 796 <tr>
 797 <td>
 798                 <p><span class="command"><strong>server</strong></span></p>
 799               </td>
 800 <td>
 801                 <p>
 802                   sets certain configuration options on
 803                   a per-server basis.
 804                 </p>
 805               </td>
 806 </tr>
 807 <tr>
 808 <td>
 809                 <p><span class="command"><strong>statistics-channels</strong></span></p>
 810               </td>
 811 <td>
 812                 <p>
 813                   declares communication channels to get access to
 814                   <span class="command"><strong>named</strong></span> statistics.
 815                 </p>
 816               </td>
 817 </tr>
 818 <tr>
 819 <td>
 820                 <p><span class="command"><strong>trusted-keys</strong></span></p>
 821               </td>
 822 <td>
 823                 <p>
 824                   defines trusted DNSSEC keys.
 825                 </p>
 826               </td>
 827 </tr>
 828 <tr>
 829 <td>
 830                 <p><span class="command"><strong>managed-keys</strong></span></p>
 831               </td>
 832 <td>
 833                 <p>
 834                   lists DNSSEC keys to be kept up to date
 835                   using RFC 5011 trust anchor maintenance.
 836                 </p>
 837               </td>
 838 </tr>
 839 <tr>
 840 <td>
 841                 <p><span class="command"><strong>view</strong></span></p>
 842               </td>
 843 <td>
 844                 <p>
 845                   defines a view.
 846                 </p>
 847               </td>
 848 </tr>
 849 <tr>
 850 <td>
 851                 <p><span class="command"><strong>zone</strong></span></p>
 852               </td>
 853 <td>
 854                 <p>
 855                   defines a zone.
 856                 </p>
 857               </td>
 858 </tr>
 859 </tbody>
 860 </table></div>
 861 <p>
 862         The <span class="command"><strong>logging</strong></span> and
 863         <span class="command"><strong>options</strong></span> statements may only occur once
 864         per
 865         configuration.
 866       </p>
 867 <div class="section">
 868 <div class="titlepage"><div><div><h3 class="title">
 869 <a name="acl_grammar"></a><span class="command"><strong>acl</strong></span> Statement Grammar</h3></div></div></div>
 870 <pre class="programlisting"><span class="command"><strong>acl</strong></span> acl-name {
 871     address_match_list
 872 };
 873 </pre>
 874 </div>
 875 <div class="section">
 876 <div class="titlepage"><div><div><h3 class="title">
 877 <a name="acl"></a><span class="command"><strong>acl</strong></span> Statement Definition and
 878           Usage</h3></div></div></div>
 879 <p>
 880           The <span class="command"><strong>acl</strong></span> statement assigns a symbolic
 881           name to an address match list. It gets its name from a primary
 882           use of address match lists: Access Control Lists (ACLs).
 883         </p>
 884 <p>
 885           The following ACLs are built-in:
 886         </p>
 887 <div class="informaltable"><table border="1">
 888 <colgroup>
 889 <col width="1.130in" class="1">
 890 <col width="4.000in" class="2">
 891 </colgroup>
 892 <tbody>
 893 <tr>
 894 <td>
 895                   <p><span class="command"><strong>any</strong></span></p>
 896                 </td>
 897 <td>
 898                   <p>
 899                     Matches all hosts.
 900                   </p>
 901                 </td>
 902 </tr>
 903 <tr>
 904 <td>
 905                   <p><span class="command"><strong>none</strong></span></p>
 906                 </td>
 907 <td>
 908                   <p>
 909                     Matches no hosts.
 910                   </p>
 911                 </td>
 912 </tr>
 913 <tr>
 914 <td>
 915                   <p><span class="command"><strong>localhost</strong></span></p>
 916                 </td>
 917 <td>
 918                   <p>
 919                     Matches the IPv4 and IPv6 addresses of all network
 920                     interfaces on the system.  When addresses are
 921                     added or removed, the <span class="command"><strong>localhost</strong></span>
 922                     ACL element is updated to reflect the changes.
 923                   </p>
 924                 </td>
 925 </tr>
 926 <tr>
 927 <td>
 928                   <p><span class="command"><strong>localnets</strong></span></p>
 929                 </td>
 930 <td>
 931                   <p>
 932                     Matches any host on an IPv4 or IPv6 network
 933                     for which the system has an interface.
 934                     When addresses are added or removed,
 935                     the <span class="command"><strong>localnets</strong></span>
 936                     ACL element is updated to reflect the changes.
 937                     Some systems do not provide a way to determine the prefix
 938                     lengths of
 939                     local IPv6 addresses.
 940                     In such a case, <span class="command"><strong>localnets</strong></span>
 941                     only matches the local
 942                     IPv6 addresses, just like <span class="command"><strong>localhost</strong></span>.
 943                   </p>
 944                 </td>
 945 </tr>
 946 </tbody>
 947 </table></div>
 948 </div>
 949 <div class="section">
 950 <div class="titlepage"><div><div><h3 class="title">
 951 <a name="controls_grammar"></a><span class="command"><strong>controls</strong></span> Statement Grammar</h3></div></div></div>
 952 <pre class="programlisting"><span class="command"><strong>controls</strong></span> {
 953    [ inet ( ip_addr | * ) [ port ip_port ]
 954                 allow { <em class="replaceable"><code> address_match_list </code></em> }
 955                 keys { <em class="replaceable"><code>key_list</code></em> }; ]
 956    [ inet ...; ]
 957    [ unix <em class="replaceable"><code>path</code></em> perm <em class="replaceable"><code>number</code></em> owner <em class="replaceable"><code>number</code></em> group <em class="replaceable"><code>number</code></em>
 958      keys { <em class="replaceable"><code>key_list</code></em> }; ]
 959    [ unix ...; ]
 960 };
 961 </pre>
 962 </div>
 963 <div class="section">
 964 <div class="titlepage"><div><div><h3 class="title">
 965 <a name="controls_statement_definition_and_usage"></a><span class="command"><strong>controls</strong></span> Statement Definition and
 966           Usage</h3></div></div></div>
 967 <p>
 968           The <span class="command"><strong>controls</strong></span> statement declares control
 969           channels to be used by system administrators to control the
 970           operation of the name server. These control channels are
 971           used by the <span class="command"><strong>rndc</strong></span> utility to send
 972           commands to and retrieve non-DNS results from a name server.
 973         </p>
 974 <p>
 975           An <span class="command"><strong>inet</strong></span> control channel is a TCP socket
 976           listening at the specified <span class="command"><strong>ip_port</strong></span> on the
 977           specified <span class="command"><strong>ip_addr</strong></span>, which can be an IPv4 or IPv6
 978           address.  An <span class="command"><strong>ip_addr</strong></span> of <code class="literal">*</code> (asterisk) is
 979           interpreted as the IPv4 wildcard address; connections will be
 980           accepted on any of the system's IPv4 addresses.
 981           To listen on the IPv6 wildcard address,
 982           use an <span class="command"><strong>ip_addr</strong></span> of <code class="literal">::</code>.
 983           If you will only use <span class="command"><strong>rndc</strong></span> on the local host,
 984           using the loopback address (<code class="literal">127.0.0.1</code>
 985           or <code class="literal">::1</code>) is recommended for maximum security.
 986         </p>
 987 <p>
 988           If no port is specified, port 953 is used. The asterisk
 989           "<code class="literal">*</code>" cannot be used for <span class="command"><strong>ip_port</strong></span>.
 990         </p>
 991 <p>
 992           The ability to issue commands over the control channel is
 993           restricted by the <span class="command"><strong>allow</strong></span> and
 994           <span class="command"><strong>keys</strong></span> clauses.
 995           Connections to the control channel are permitted based on the
 996           <span class="command"><strong>address_match_list</strong></span>.  This is for simple
 997           IP address based filtering only; any <span class="command"><strong>key_id</strong></span>
 998           elements of the <span class="command"><strong>address_match_list</strong></span>
 999           are ignored.
1000         </p>
1001 <p>
1002           A <span class="command"><strong>unix</strong></span> control channel is a UNIX domain
1003           socket listening at the specified path in the file system.
1004           Access to the socket is specified by the <span class="command"><strong>perm</strong></span>,
1005           <span class="command"><strong>owner</strong></span> and <span class="command"><strong>group</strong></span> clauses.
1006           Note on some platforms (SunOS and Solaris) the permissions
1007           (<span class="command"><strong>perm</strong></span>) are applied to the parent directory
1008           as the permissions on the socket itself are ignored.
1009         </p>
1010 <p>
1011           The primary authorization mechanism of the command
1012           channel is the <span class="command"><strong>key_list</strong></span>, which
1013           contains a list of <span class="command"><strong>key_id</strong></span>s.
1014           Each <span class="command"><strong>key_id</strong></span> in the <span class="command"><strong>key_list</strong></span>
1015           is authorized to execute commands over the control channel.
1016           See <a class="xref" href="Bv9ARM.ch03.html#rndc">Remote Name Daemon Control application</a> in <a class="xref" href="Bv9ARM.ch03.html#admin_tools" title="Administrative Tools">the section called &#8220;Administrative Tools&#8221;</a>)
1017           for information about configuring keys in <span class="command"><strong>rndc</strong></span>.
1018         </p>
1019 <p>
1020           If no <span class="command"><strong>controls</strong></span> statement is present,
1021           <span class="command"><strong>named</strong></span> will set up a default
1022           control channel listening on the loopback address 127.0.0.1
1023           and its IPv6 counterpart ::1.
1024           In this case, and also when the <span class="command"><strong>controls</strong></span> statement
1025           is present but does not have a <span class="command"><strong>keys</strong></span> clause,
1026           <span class="command"><strong>named</strong></span> will attempt to load the command channel key
1027           from the file <code class="filename">rndc.key</code> in
1028           <code class="filename">/etc</code> (or whatever <code class="varname">sysconfdir</code>
1029           was specified as when <acronym class="acronym">BIND</acronym> was built).
1030           To create a <code class="filename">rndc.key</code> file, run
1031           <strong class="userinput"><code>rndc-confgen -a</code></strong>.
1032         </p>
1033 <p>
1034           The <code class="filename">rndc.key</code> feature was created to
1035           ease the transition of systems from <acronym class="acronym">BIND</acronym> 8,
1036           which did not have digital signatures on its command channel
1037           messages and thus did not have a <span class="command"><strong>keys</strong></span> clause.
1038
1039           It makes it possible to use an existing <acronym class="acronym">BIND</acronym> 8
1040           configuration file in <acronym class="acronym">BIND</acronym> 9 unchanged,
1041           and still have <span class="command"><strong>rndc</strong></span> work the same way
1042           <span class="command"><strong>ndc</strong></span> worked in BIND 8, simply by executing the
1043           command <strong class="userinput"><code>rndc-confgen -a</code></strong> after BIND 9 is
1044           installed.
1045         </p>
1046 <p>
1047           Since the <code class="filename">rndc.key</code> feature
1048           is only intended to allow the backward-compatible usage of
1049           <acronym class="acronym">BIND</acronym> 8 configuration files, this
1050           feature does not
1051           have a high degree of configurability.  You cannot easily change
1052           the key name or the size of the secret, so you should make a
1053           <code class="filename">rndc.conf</code> with your own key if you
1054           wish to change
1055           those things.  The <code class="filename">rndc.key</code> file
1056           also has its
1057           permissions set such that only the owner of the file (the user that
1058           <span class="command"><strong>named</strong></span> is running as) can access it.
1059           If you
1060           desire greater flexibility in allowing other users to access
1061           <span class="command"><strong>rndc</strong></span> commands, then you need to create
1062           a
1063           <code class="filename">rndc.conf</code> file and make it group
1064           readable by a group
1065           that contains the users who should have access.
1066         </p>
1067 <p>
1068           To disable the command channel, use an empty
1069           <span class="command"><strong>controls</strong></span> statement:
1070           <span class="command"><strong>controls { };</strong></span>.
1071         </p>
1072 </div>
1073 <div class="section">
1074 <div class="titlepage"><div><div><h3 class="title">
1075 <a name="include_grammar"></a><span class="command"><strong>include</strong></span> Statement Grammar</h3></div></div></div>
1076 <pre class="programlisting"><span class="command"><strong>include</strong></span> <em class="replaceable"><code>filename</code></em>;</pre>
1077 </div>
1078 <div class="section">
1079 <div class="titlepage"><div><div><h3 class="title">
1080 <a name="include_statement"></a><span class="command"><strong>include</strong></span> Statement Definition and Usage</h3></div></div></div>
1081 <p>
1082           The <span class="command"><strong>include</strong></span> statement inserts the
1083           specified file at the point where the <span class="command"><strong>include</strong></span>
1084           statement is encountered. The <span class="command"><strong>include</strong></span>
1085                 statement facilitates the administration of configuration
1086           files
1087           by permitting the reading or writing of some things but not
1088           others. For example, the statement could include private keys
1089           that are readable only by the name server.
1090         </p>
1091 </div>
1092 <div class="section">
1093 <div class="titlepage"><div><div><h3 class="title">
1094 <a name="key_grammar"></a><span class="command"><strong>key</strong></span> Statement Grammar</h3></div></div></div>
1095 <pre class="programlisting"><span class="command"><strong>key</strong></span> <em class="replaceable"><code>key_id</code></em> {
1096     algorithm <em class="replaceable"><code>algorithm_id</code></em>;
1097     secret <em class="replaceable"><code>secret_string</code></em>;
1098 };
1099 </pre>
1100 </div>
1101 <div class="section">
1102 <div class="titlepage"><div><div><h3 class="title">
1103 <a name="key_statement"></a><span class="command"><strong>key</strong></span> Statement Definition and Usage</h3></div></div></div>
1104 <p>
1105           The <span class="command"><strong>key</strong></span> statement defines a shared
1106           secret key for use with TSIG (see <a class="xref" href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
1107           or the command channel
1108           (see <a class="xref" href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and Usage">the section called &#8220;<span class="command"><strong>controls</strong></span> Statement Definition and
1109           Usage&#8221;</a>).
1110         </p>
1111 <p>
1112           The <span class="command"><strong>key</strong></span> statement can occur at the
1113           top level
1114           of the configuration file or inside a <span class="command"><strong>view</strong></span>
1115           statement.  Keys defined in top-level <span class="command"><strong>key</strong></span>
1116           statements can be used in all views.  Keys intended for use in
1117           a <span class="command"><strong>controls</strong></span> statement
1118           (see <a class="xref" href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and Usage">the section called &#8220;<span class="command"><strong>controls</strong></span> Statement Definition and
1119           Usage&#8221;</a>)
1120           must be defined at the top level.
1121         </p>
1122 <p>
1123           The <em class="replaceable"><code>key_id</code></em>, also known as the
1124           key name, is a domain name uniquely identifying the key. It can
1125           be used in a <span class="command"><strong>server</strong></span>
1126           statement to cause requests sent to that
1127           server to be signed with this key, or in address match lists to
1128           verify that incoming requests have been signed with a key
1129           matching this name, algorithm, and secret.
1130         </p>
1131 <p>
1132           The <em class="replaceable"><code>algorithm_id</code></em> is a string
1133           that specifies a security/authentication algorithm.  Named
1134           supports <code class="literal">hmac-md5</code>,
1135           <code class="literal">hmac-sha1</code>, <code class="literal">hmac-sha224</code>,
1136           <code class="literal">hmac-sha256</code>, <code class="literal">hmac-sha384</code>
1137           and <code class="literal">hmac-sha512</code> TSIG authentication.
1138           Truncated hashes are supported by appending the minimum
1139           number of required bits preceded by a dash, e.g.
1140           <code class="literal">hmac-sha1-80</code>.  The
1141           <em class="replaceable"><code>secret_string</code></em> is the secret
1142           to be used by the algorithm, and is treated as a base-64
1143           encoded string.
1144         </p>
1145 </div>
1146 <div class="section">
1147 <div class="titlepage"><div><div><h3 class="title">
1148 <a name="logging_grammar"></a><span class="command"><strong>logging</strong></span> Statement Grammar</h3></div></div></div>
1149 <pre class="programlisting"><span class="command"><strong>logging</strong></span> {
1150    [ <span class="command"><strong>channel</strong></span> <em class="replaceable"><code>channel_name</code></em> {
1151      ( <span class="command"><strong>file</strong></span> <em class="replaceable"><code>path_name</code></em>
1152          [ <span class="command"><strong>versions</strong></span> ( <em class="replaceable"><code>number</code></em> | <span class="command"><strong>unlimited</strong></span> ) ]
1153          [ <span class="command"><strong>size</strong></span> <em class="replaceable"><code>size_spec</code></em> ]
1154        | <span class="command"><strong>syslog</strong></span> <em class="replaceable"><code>syslog_facility</code></em>
1155        | <span class="command"><strong>stderr</strong></span>
1156        | <span class="command"><strong>null</strong></span> );
1157      [ <span class="command"><strong>severity</strong></span> (<code class="option">critical</code> | <code class="option">error</code> | <code class="option">warning</code> | <code class="option">notice</code> |
1158                  <code class="option">info</code> | <code class="option">debug</code> [ <em class="replaceable"><code>level</code></em> ] | <code class="option">dynamic</code> ); ]
1159      [ <span class="command"><strong>print-category</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1160      [ <span class="command"><strong>print-severity</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1161      [ <span class="command"><strong>print-time</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1162    }; ]
1163    [ <span class="command"><strong>category</strong></span> <em class="replaceable"><code>category_name</code></em> {
1164      <em class="replaceable"><code>channel_name</code></em> ; [ <em class="replaceable"><code>channel_name</code></em> ; ... ]
1165    }; ]
1166    ...
1167 };
1168 </pre>
1169 </div>
1170 <div class="section">
1171 <div class="titlepage"><div><div><h3 class="title">
1172 <a name="logging_statement"></a><span class="command"><strong>logging</strong></span> Statement Definition and Usage</h3></div></div></div>
1173 <p>
1174           The <span class="command"><strong>logging</strong></span> statement configures a
1175           wide
1176           variety of logging options for the name server. Its <span class="command"><strong>channel</strong></span> phrase
1177           associates output methods, format options and severity levels with
1178           a name that can then be used with the <span class="command"><strong>category</strong></span> phrase
1179           to select how various classes of messages are logged.
1180         </p>
1181 <p>
1182           Only one <span class="command"><strong>logging</strong></span> statement is used to
1183           define
1184           as many channels and categories as are wanted. If there is no <span class="command"><strong>logging</strong></span> statement,
1185           the logging configuration will be:
1186         </p>
1187 <pre class="programlisting">logging {
1188      category default { default_syslog; default_debug; };
1189      category unmatched { null; };
1190 };
1191 </pre>
1192 <p>
1193           In <acronym class="acronym">BIND</acronym> 9, the logging configuration
1194           is only established when
1195           the entire configuration file has been parsed.  In <acronym class="acronym">BIND</acronym> 8, it was
1196           established as soon as the <span class="command"><strong>logging</strong></span>
1197           statement
1198           was parsed. When the server is starting up, all logging messages
1199           regarding syntax errors in the configuration file go to the default
1200           channels, or to standard error if the "<code class="option">-g</code>" option
1201           was specified.
1202         </p>
1203 <div class="section">
1204 <div class="titlepage"><div><div><h4 class="title">
1205 <a name="channel"></a>The <span class="command"><strong>channel</strong></span> Phrase</h4></div></div></div>
1206 <p>
1207             All log output goes to one or more <span class="emphasis"><em>channels</em></span>;
1208             you can make as many of them as you want.
1209           </p>
1210 <p>
1211             Every channel definition must include a destination clause that
1212             says whether messages selected for the channel go to a file, to a
1213             particular syslog facility, to the standard error stream, or are
1214             discarded. It can optionally also limit the message severity level
1215             that will be accepted by the channel (the default is
1216             <span class="command"><strong>info</strong></span>), and whether to include a
1217             <span class="command"><strong>named</strong></span>-generated time stamp, the
1218             category name
1219             and/or severity level (the default is not to include any).
1220           </p>
1221 <p>
1222             The <span class="command"><strong>null</strong></span> destination clause
1223             causes all messages sent to the channel to be discarded;
1224             in that case, other options for the channel are meaningless.
1225           </p>
1226 <p>
1227             The <span class="command"><strong>file</strong></span> destination clause directs
1228             the channel
1229             to a disk file.  It can include limitations
1230             both on how large the file is allowed to become, and how many
1231             versions
1232             of the file will be saved each time the file is opened.
1233           </p>
1234 <p>
1235             If you use the <span class="command"><strong>versions</strong></span> log file
1236             option, then
1237             <span class="command"><strong>named</strong></span> will retain that many backup
1238             versions of the file by
1239             renaming them when opening.  For example, if you choose to keep
1240             three old versions
1241             of the file <code class="filename">lamers.log</code>, then just
1242             before it is opened
1243             <code class="filename">lamers.log.1</code> is renamed to
1244             <code class="filename">lamers.log.2</code>, <code class="filename">lamers.log.0</code> is renamed
1245             to <code class="filename">lamers.log.1</code>, and <code class="filename">lamers.log</code> is
1246             renamed to <code class="filename">lamers.log.0</code>.
1247             You can say <span class="command"><strong>versions unlimited</strong></span> to
1248             not limit
1249             the number of versions.
1250             If a <span class="command"><strong>size</strong></span> option is associated with
1251             the log file,
1252             then renaming is only done when the file being opened exceeds the
1253             indicated size.  No backup versions are kept by default; any
1254             existing
1255             log file is simply appended.
1256           </p>
1257 <p>
1258             The <span class="command"><strong>size</strong></span> option for files is used
1259             to limit log
1260             growth. If the file ever exceeds the size, then <span class="command"><strong>named</strong></span> will
1261             stop writing to the file unless it has a <span class="command"><strong>versions</strong></span> option
1262             associated with it.  If backup versions are kept, the files are
1263             rolled as
1264             described above and a new one begun.  If there is no
1265             <span class="command"><strong>versions</strong></span> option, no more data will
1266             be written to the log
1267             until some out-of-band mechanism removes or truncates the log to
1268             less than the
1269             maximum size.  The default behavior is not to limit the size of
1270             the
1271             file.
1272           </p>
1273 <p>
1274             Example usage of the <span class="command"><strong>size</strong></span> and
1275             <span class="command"><strong>versions</strong></span> options:
1276           </p>
1277 <pre class="programlisting">channel an_example_channel {
1278     file "example.log" versions 3 size 20m;
1279     print-time yes;
1280     print-category yes;
1281 };
1282 </pre>
1283 <p>
1284             The <span class="command"><strong>syslog</strong></span> destination clause
1285             directs the
1286             channel to the system log.  Its argument is a
1287             syslog facility as described in the <span class="command"><strong>syslog</strong></span> man
1288             page. Known facilities are <span class="command"><strong>kern</strong></span>, <span class="command"><strong>user</strong></span>,
1289             <span class="command"><strong>mail</strong></span>, <span class="command"><strong>daemon</strong></span>, <span class="command"><strong>auth</strong></span>,
1290             <span class="command"><strong>syslog</strong></span>, <span class="command"><strong>lpr</strong></span>, <span class="command"><strong>news</strong></span>,
1291             <span class="command"><strong>uucp</strong></span>, <span class="command"><strong>cron</strong></span>, <span class="command"><strong>authpriv</strong></span>,
1292             <span class="command"><strong>ftp</strong></span>, <span class="command"><strong>local0</strong></span>, <span class="command"><strong>local1</strong></span>,
1293             <span class="command"><strong>local2</strong></span>, <span class="command"><strong>local3</strong></span>, <span class="command"><strong>local4</strong></span>,
1294             <span class="command"><strong>local5</strong></span>, <span class="command"><strong>local6</strong></span> and
1295             <span class="command"><strong>local7</strong></span>, however not all facilities
1296             are supported on
1297             all operating systems.
1298             How <span class="command"><strong>syslog</strong></span> will handle messages
1299             sent to
1300             this facility is described in the <span class="command"><strong>syslog.conf</strong></span> man
1301             page. If you have a system which uses a very old version of <span class="command"><strong>syslog</strong></span> that
1302             only uses two arguments to the <span class="command"><strong>openlog()</strong></span> function,
1303             then this clause is silently ignored.
1304           </p>
1305 <p>
1306             On Windows machines syslog messages are directed to the EventViewer.
1307           </p>
1308 <p>
1309             The <span class="command"><strong>severity</strong></span> clause works like <span class="command"><strong>syslog</strong></span>'s
1310             "priorities", except that they can also be used if you are writing
1311             straight to a file rather than using <span class="command"><strong>syslog</strong></span>.
1312             Messages which are not at least of the severity level given will
1313             not be selected for the channel; messages of higher severity
1314             levels
1315             will be accepted.
1316           </p>
1317 <p>
1318             If you are using <span class="command"><strong>syslog</strong></span>, then the <span class="command"><strong>syslog.conf</strong></span> priorities
1319             will also determine what eventually passes through. For example,
1320             defining a channel facility and severity as <span class="command"><strong>daemon</strong></span> and <span class="command"><strong>debug</strong></span> but
1321             only logging <span class="command"><strong>daemon.warning</strong></span> via <span class="command"><strong>syslog.conf</strong></span> will
1322             cause messages of severity <span class="command"><strong>info</strong></span> and
1323             <span class="command"><strong>notice</strong></span> to
1324             be dropped. If the situation were reversed, with <span class="command"><strong>named</strong></span> writing
1325             messages of only <span class="command"><strong>warning</strong></span> or higher,
1326             then <span class="command"><strong>syslogd</strong></span> would
1327             print all messages it received from the channel.
1328           </p>
1329 <p>
1330             The <span class="command"><strong>stderr</strong></span> destination clause
1331             directs the
1332             channel to the server's standard error stream.  This is intended
1333             for
1334             use when the server is running as a foreground process, for
1335             example
1336             when debugging a configuration.
1337           </p>
1338 <p>
1339             The server can supply extensive debugging information when
1340             it is in debugging mode. If the server's global debug level is
1341             greater
1342             than zero, then debugging mode will be active. The global debug
1343             level is set either by starting the <span class="command"><strong>named</strong></span> server
1344             with the <code class="option">-d</code> flag followed by a positive integer,
1345             or by running <span class="command"><strong>rndc trace</strong></span>.
1346             The global debug level
1347             can be set to zero, and debugging mode turned off, by running <span class="command"><strong>rndc
1348 notrace</strong></span>. All debugging messages in the server have a debug
1349             level, and higher debug levels give more detailed output. Channels
1350             that specify a specific debug severity, for example:
1351           </p>
1352 <pre class="programlisting">channel specific_debug_level {
1353     file "foo";
1354     severity debug 3;
1355 };
1356 </pre>
1357 <p>
1358             will get debugging output of level 3 or less any time the
1359             server is in debugging mode, regardless of the global debugging
1360             level. Channels with <span class="command"><strong>dynamic</strong></span>
1361             severity use the
1362             server's global debug level to determine what messages to print.
1363           </p>
1364 <p>
1365             If <span class="command"><strong>print-time</strong></span> has been turned on,
1366             then
1367             the date and time will be logged. <span class="command"><strong>print-time</strong></span> may
1368             be specified for a <span class="command"><strong>syslog</strong></span> channel,
1369             but is usually
1370             pointless since <span class="command"><strong>syslog</strong></span> also logs
1371             the date and
1372             time. If <span class="command"><strong>print-category</strong></span> is
1373             requested, then the
1374             category of the message will be logged as well. Finally, if <span class="command"><strong>print-severity</strong></span> is
1375             on, then the severity level of the message will be logged. The <span class="command"><strong>print-</strong></span> options may
1376             be used in any combination, and will always be printed in the
1377             following
1378             order: time, category, severity. Here is an example where all
1379             three <span class="command"><strong>print-</strong></span> options
1380             are on:
1381           </p>
1382 <p>
1383             <code class="computeroutput">28-Feb-2000 15:05:32.863 general: notice: running</code>
1384           </p>
1385 <p>
1386             There are four predefined channels that are used for
1387             <span class="command"><strong>named</strong></span>'s default logging as follows.
1388             How they are
1389             used is described in <a class="xref" href="Bv9ARM.ch06.html#the_category_phrase" title="The category Phrase">the section called &#8220;The <span class="command"><strong>category</strong></span> Phrase&#8221;</a>.
1390           </p>
1391 <pre class="programlisting">channel default_syslog {
1392     // send to syslog's daemon facility
1393     syslog daemon;
1394     // only send priority info and higher
1395     severity info;
1396
1397 channel default_debug {
1398     // write to named.run in the working directory
1399     // Note: stderr is used instead of "named.run" if
1400     // the server is started with the '-f' option.
1401     file "named.run";
1402     // log at the server's current debug level
1403     severity dynamic;
1404 };
1405
1406 channel default_stderr {
1407     // writes to stderr
1408     stderr;
1409     // only send priority info and higher
1410     severity info;
1411 };
1412
1413 channel null {
1414    // toss anything sent to this channel
1415    null;
1416 };
1417 </pre>
1418 <p>
1419             The <span class="command"><strong>default_debug</strong></span> channel has the
1420             special
1421             property that it only produces output when the server's debug
1422             level is
1423             nonzero.  It normally writes to a file called <code class="filename">named.run</code>
1424             in the server's working directory.
1425           </p>
1426 <p>
1427             For security reasons, when the "<code class="option">-u</code>"
1428             command line option is used, the <code class="filename">named.run</code> file
1429             is created only after <span class="command"><strong>named</strong></span> has
1430             changed to the
1431             new UID, and any debug output generated while <span class="command"><strong>named</strong></span> is
1432             starting up and still running as root is discarded.  If you need
1433             to capture this output, you must run the server with the "<code class="option">-g</code>"
1434             option and redirect standard error to a file.
1435           </p>
1436 <p>
1437             Once a channel is defined, it cannot be redefined. Thus you
1438             cannot alter the built-in channels directly, but you can modify
1439             the default logging by pointing categories at channels you have
1440             defined.
1441           </p>
1442 </div>
1443 <div class="section">
1444 <div class="titlepage"><div><div><h4 class="title">
1445 <a name="the_category_phrase"></a>The <span class="command"><strong>category</strong></span> Phrase</h4></div></div></div>
1446 <p>
1447             There are many categories, so you can send the logs you want
1448             to see wherever you want, without seeing logs you don't want. If
1449             you don't specify a list of channels for a category, then log
1450             messages
1451             in that category will be sent to the <span class="command"><strong>default</strong></span> category
1452             instead. If you don't specify a default category, the following
1453             "default default" is used:
1454           </p>
1455 <pre class="programlisting">category default { default_syslog; default_debug; };
1456 </pre>
1457 <p>
1458             As an example, let's say you want to log security events to
1459             a file, but you also want keep the default logging behavior. You'd
1460             specify the following:
1461           </p>
1462 <pre class="programlisting">channel my_security_channel {
1463     file "my_security_file";
1464     severity info;
1465 };
1466 category security {
1467     my_security_channel;
1468     default_syslog;
1469     default_debug;
1470 };</pre>
1471 <p>
1472             To discard all messages in a category, specify the <span class="command"><strong>null</strong></span> channel:
1473           </p>
1474 <pre class="programlisting">category xfer-out { null; };
1475 category notify { null; };
1476 </pre>
1477 <p>
1478             Following are the available categories and brief descriptions
1479             of the types of log information they contain. More
1480             categories may be added in future <acronym class="acronym">BIND</acronym> releases.
1481           </p>
1482 <div class="informaltable"><table border="1">
1483 <colgroup>
1484 <col width="1.150in" class="1">
1485 <col width="3.350in" class="2">
1486 </colgroup>
1487 <tbody>
1488 <tr>
1489 <td>
1490           <p><span class="command"><strong>client</strong></span></p>
1491         </td>
1492 <td>
1493           <p>
1494             Processing of client requests.
1495           </p>
1496         </td>
1497 </tr>
1498 <tr>
1499 <td>
1500           <p><span class="command"><strong>cname</strong></span></p>
1501         </td>
1502 <td>
1503           <p>
1504             Logs nameservers that are skipped due to them being
1505             a CNAME rather than A / AAAA records.
1506           </p>
1507         </td>
1508 </tr>
1509 <tr>
1510 <td>
1511           <p><span class="command"><strong>config</strong></span></p>
1512         </td>
1513 <td>
1514           <p>
1515             Configuration file parsing and processing.
1516           </p>
1517         </td>
1518 </tr>
1519 <tr>
1520 <td>
1521           <p><span class="command"><strong>database</strong></span></p>
1522         </td>
1523 <td>
1524           <p>
1525             Messages relating to the databases used
1526             internally by the name server to store zone and cache
1527             data.
1528           </p>
1529         </td>
1530 </tr>
1531 <tr>
1532 <td>
1533           <p><span class="command"><strong>default</strong></span></p>
1534         </td>
1535 <td>
1536           <p>
1537             The default category defines the logging
1538             options for those categories where no specific
1539             configuration has been
1540             defined.
1541           </p>
1542         </td>
1543 </tr>
1544 <tr>
1545 <td>
1546           <p><span class="command"><strong>delegation-only</strong></span></p>
1547         </td>
1548 <td>
1549           <p>
1550             Delegation only.  Logs queries that have been
1551             forced to NXDOMAIN as the result of a
1552             delegation-only zone or a
1553             <span class="command"><strong>delegation-only</strong></span> in a
1554             forward, hint or stub zone declaration.
1555           </p>
1556         </td>
1557 </tr>
1558 <tr>
1559 <td>
1560           <p><span class="command"><strong>dispatch</strong></span></p>
1561         </td>
1562 <td>
1563           <p>
1564             Dispatching of incoming packets to the
1565             server modules where they are to be processed.
1566           </p>
1567         </td>
1568 </tr>
1569 <tr>
1570 <td>
1571           <p><span class="command"><strong>dnssec</strong></span></p>
1572         </td>
1573 <td>
1574           <p>
1575             DNSSEC and TSIG protocol processing.
1576           </p>
1577         </td>
1578 </tr>
1579 <tr>
1580 <td>
1581           <p><span class="command"><strong>edns-disabled</strong></span></p>
1582         </td>
1583 <td>
1584           <p>
1585             Log queries that have been forced to use plain
1586             DNS due to timeouts.  This is often due to
1587             the remote servers not being RFC 1034 compliant
1588             (not always returning FORMERR or similar to
1589             EDNS queries and other extensions to the DNS
1590             when they are not understood).  In other words, this is
1591             targeted at servers that fail to respond to
1592             DNS queries that they don't understand.
1593           </p>
1594           <p>
1595             Note: the log message can also be due to
1596             packet loss.  Before reporting servers for
1597             non-RFC 1034 compliance they should be re-tested
1598             to determine the nature of the non-compliance.
1599             This testing should prevent or reduce the
1600             number of false-positive reports.
1601           </p>
1602           <p>
1603             Note: eventually <span class="command"><strong>named</strong></span> will have to stop
1604             treating such timeouts as due to RFC 1034 non
1605             compliance and start treating it as plain
1606             packet loss.  Falsely classifying packet
1607             loss as due to RFC 1034 non compliance impacts
1608             on DNSSEC validation which requires EDNS for
1609             the DNSSEC records to be returned.
1610           </p>
1611         </td>
1612 </tr>
1613 <tr>
1614 <td>
1615           <p><span class="command"><strong>general</strong></span></p>
1616         </td>
1617 <td>
1618           <p>
1619             The catch-all. Many things still aren't
1620             classified into categories, and they all end up here.
1621           </p>
1622         </td>
1623 </tr>
1624 <tr>
1625 <td>
1626           <p><span class="command"><strong>lame-servers</strong></span></p>
1627         </td>
1628 <td>
1629           <p>
1630             Lame servers.  These are misconfigurations
1631             in remote servers, discovered by BIND 9 when trying to
1632             query those servers during resolution.
1633           </p>
1634         </td>
1635 </tr>
1636 <tr>
1637 <td>
1638           <p><span class="command"><strong>network</strong></span></p>
1639         </td>
1640 <td>
1641           <p>
1642             Network operations.
1643           </p>
1644         </td>
1645 </tr>
1646 <tr>
1647 <td>
1648           <p><span class="command"><strong>notify</strong></span></p>
1649         </td>
1650 <td>
1651           <p>
1652             The NOTIFY protocol.
1653           </p>
1654         </td>
1655 </tr>
1656 <tr>
1657 <td>
1658           <p><span class="command"><strong>queries</strong></span></p>
1659         </td>
1660 <td>
1661           <p>
1662             Specify where queries should be logged to.
1663           </p>
1664           <p>
1665             At startup, specifying the category <span class="command"><strong>queries</strong></span> will also
1666             enable query logging unless <span class="command"><strong>querylog</strong></span> option has been
1667             specified.
1668           </p>
1669
1670           <p>
1671             The query log entry reports the client's IP
1672             address and port number, and the query name,
1673             class and type.  Next it reports whether the
1674             Recursion Desired flag was set (+ if set, -
1675             if not set), if the query was signed (S),
1676             EDNS was in use (E), if TCP was used (T), if
1677             DO (DNSSEC Ok) was set (D), or if CD (Checking
1678             Disabled) was set (C).  After this the
1679             destination address the query was sent to is
1680             reported.
1681           </p>
1682
1683           <p>
1684             <code class="computeroutput">client 127.0.0.1#62536 (www.example.com): query: www.example.com IN AAAA +SE</code>
1685           </p>
1686           <p>
1687             <code class="computeroutput">client ::1#62537 (www.example.net): query: www.example.net IN AAAA -SE</code>
1688           </p>
1689           <p>
1690             (The first part of this log message, showing the
1691             client address/port number and query name, is
1692             repeated in all subsequent log messages related
1693             to the same query.)
1694           </p>
1695         </td>
1696 </tr>
1697 <tr>
1698 <td>
1699           <p><span class="command"><strong>query-errors</strong></span></p>
1700         </td>
1701 <td>
1702           <p>
1703             Information about queries that resulted in some
1704             failure.
1705           </p>
1706         </td>
1707 </tr>
1708 <tr>
1709 <td>
1710           <p><span class="command"><strong>rate-limit</strong></span></p>
1711         </td>
1712 <td>
1713           <p>
1714             (Only available when <acronym class="acronym">BIND</acronym> 9 is
1715             configured with the <strong class="userinput"><code>--enable-rrl</code></strong>
1716             option at compile time.)
1717           </p>
1718           <p>
1719             The start, periodic, and final notices of the
1720             rate limiting of a stream of responses are logged at
1721             <span class="command"><strong>info</strong></span> severity in this category.
1722             These messages include a hash value of the domain name
1723             of the response and the name itself,
1724             except when there is insufficient memory to record
1725             the name for the final notice
1726             The final notice is normally delayed until about one
1727             minute after rate limit stops.
1728             A lack of memory can hurry the final notice,
1729             in which case it starts with an asterisk (*).
1730             Various internal events are logged at debug 1 level
1731             and higher.
1732           </p>
1733           <p>
1734             Rate limiting of individual requests
1735             is logged in the <span class="command"><strong>query-errors</strong></span> category.
1736           </p>
1737         </td>
1738 </tr>
1739 <tr>
1740 <td>
1741           <p><span class="command"><strong>resolver</strong></span></p>
1742         </td>
1743 <td>
1744           <p>
1745             DNS resolution, such as the recursive
1746             lookups performed on behalf of clients by a caching name
1747             server.
1748           </p>
1749         </td>
1750 </tr>
1751 <tr>
1752 <td>
1753           <p><span class="command"><strong>rpz</strong></span></p>
1754         </td>
1755 <td>
1756           <p>
1757             Information about errors in response policy zone files,
1758             rewritten responses, and at the highest
1759             <span class="command"><strong>debug</strong></span> levels, mere rewriting
1760             attempts.
1761           </p>
1762         </td>
1763 </tr>
1764 <tr>
1765 <td>
1766           <p><span class="command"><strong>security</strong></span></p>
1767         </td>
1768 <td>
1769           <p>
1770             Approval and denial of requests.
1771           </p>
1772         </td>
1773 </tr>
1774 <tr>
1775 <td>
1776           <p><span class="command"><strong>spill</strong></span></p>
1777         </td>
1778 <td>
1779           <p>
1780             Logs queries that have been terminated, either by dropping
1781             or responding with SERVFAIL, as a result of a fetchlimit
1782             quota being exceeded.
1783           </p>
1784         </td>
1785 </tr>
1786 <tr>
1787 <td>
1788           <p><span class="command"><strong>unmatched</strong></span></p>
1789         </td>
1790 <td>
1791           <p>
1792             Messages that <span class="command"><strong>named</strong></span> was unable to determine the
1793             class of or for which there was no matching <span class="command"><strong>view</strong></span>.
1794             A one line summary is also logged to the <span class="command"><strong>client</strong></span> category.
1795             This category is best sent to a file or stderr, by
1796             default it is sent to
1797             the <span class="command"><strong>null</strong></span> channel.
1798           </p>
1799         </td>
1800 </tr>
1801 <tr>
1802 <td>
1803           <p><span class="command"><strong>update</strong></span></p>
1804         </td>
1805 <td>
1806           <p>
1807             Dynamic updates.
1808           </p>
1809         </td>
1810 </tr>
1811 <tr>
1812 <td>
1813           <p><span class="command"><strong>update-security</strong></span></p>
1814         </td>
1815 <td>
1816           <p>
1817             Approval and denial of update requests.
1818           </p>
1819         </td>
1820 </tr>
1821 <tr>
1822 <td>
1823           <p><span class="command"><strong>xfer-in</strong></span></p>
1824         </td>
1825 <td>
1826           <p>
1827             Zone transfers the server is receiving.
1828           </p>
1829         </td>
1830 </tr>
1831 <tr>
1832 <td>
1833           <p><span class="command"><strong>xfer-out</strong></span></p>
1834         </td>
1835 <td>
1836           <p>
1837             Zone transfers the server is sending.
1838           </p>
1839         </td>
1840 </tr>
1841 </tbody>
1842 </table></div>
1843 </div>
1844 <div class="section">
1845 <div class="titlepage"><div><div><h4 class="title">
1846 <a name="query_errors"></a>The <span class="command"><strong>query-errors</strong></span> Category</h4></div></div></div>
1847 <p>
1848             The <span class="command"><strong>query-errors</strong></span> category is
1849             specifically intended for debugging purposes: To identify
1850             why and how specific queries result in responses which
1851             indicate an error.
1852             Messages of this category are therefore only logged
1853             with <span class="command"><strong>debug</strong></span> levels.
1854           </p>
1855 <p>
1856             At the debug levels of 1 or higher, each response with the
1857             rcode of SERVFAIL is logged as follows:
1858           </p>
1859 <p>
1860             <code class="computeroutput">client 127.0.0.1#61502: query failed (SERVFAIL) for www.example.com/IN/AAAA at query.c:3880</code>
1861           </p>
1862 <p>
1863             This means an error resulting in SERVFAIL was
1864             detected at line 3880 of source file
1865             <code class="filename">query.c</code>.
1866             Log messages of this level will particularly
1867             help identify the cause of SERVFAIL for an
1868             authoritative server.
1869           </p>
1870 <p>
1871             At the debug levels of 2 or higher, detailed context
1872             information of recursive resolutions that resulted in
1873             SERVFAIL is logged.
1874             The log message will look like as follows:
1875           </p>
1876 <p>
1877
1878             </p>
1879 <pre class="programlisting">
1880 fetch completed at resolver.c:2970 for www.example.com/A
1881 in 30.000183: timed out/success [domain:example.com,
1882 referral:2,restart:7,qrysent:8,timeout:5,lame:0,neterr:0,
1883 badresp:1,adberr:0,findfail:0,valfail:0]
1884             </pre>
1885 <p>
1886           </p>
1887 <p>
1888             The first part before the colon shows that a recursive
1889             resolution for AAAA records of www.example.com completed
1890             in 30.000183 seconds and the final result that led to the
1891             SERVFAIL was determined at line 2970 of source file
1892             <code class="filename">resolver.c</code>.
1893           </p>
1894 <p>
1895             The following part shows the detected final result and the
1896             latest result of DNSSEC validation.
1897             The latter is always success when no validation attempt
1898             is made.
1899             In this example, this query resulted in SERVFAIL probably
1900             because all name servers are down or unreachable, leading
1901             to a timeout in 30 seconds.
1902             DNSSEC validation was probably not attempted.
1903           </p>
1904 <p>
1905             The last part enclosed in square brackets shows statistics
1906             information collected for this particular resolution
1907             attempt.
1908             The <code class="varname">domain</code> field shows the deepest zone
1909             that the resolver reached;
1910             it is the zone where the error was finally detected.
1911             The meaning of the other fields is summarized in the
1912             following table.
1913           </p>
1914 <div class="informaltable"><table border="1">
1915 <colgroup>
1916 <col width="1.150in" class="1">
1917 <col width="3.350in" class="2">
1918 </colgroup>
1919 <tbody>
1920 <tr>
1921 <td>
1922                     <p><code class="varname">referral</code></p>
1923                   </td>
1924 <td>
1925                     <p>
1926                       The number of referrals the resolver received
1927                       throughout the resolution process.
1928                       In the above example this is 2, which are most
1929                       likely com and example.com.
1930                     </p>
1931                   </td>
1932 </tr>
1933 <tr>
1934 <td>
1935                     <p><code class="varname">restart</code></p>
1936                   </td>
1937 <td>
1938                     <p>
1939                       The number of cycles that the resolver tried
1940                       remote servers at the <code class="varname">domain</code>
1941                       zone.
1942                       In each cycle the resolver sends one query
1943                       (possibly resending it, depending on the response)
1944                       to each known name server of
1945                       the <code class="varname">domain</code> zone.
1946                     </p>
1947                   </td>
1948 </tr>
1949 <tr>
1950 <td>
1951                     <p><code class="varname">qrysent</code></p>
1952                   </td>
1953 <td>
1954                     <p>
1955                       The number of queries the resolver sent at the
1956                       <code class="varname">domain</code> zone.
1957                     </p>
1958                   </td>
1959 </tr>
1960 <tr>
1961 <td>
1962                     <p><code class="varname">timeout</code></p>
1963                   </td>
1964 <td>
1965                     <p>
1966                       The number of timeouts since the resolver
1967                       received the last response.
1968                     </p>
1969                   </td>
1970 </tr>
1971 <tr>
1972 <td>
1973                     <p><code class="varname">lame</code></p>
1974                   </td>
1975 <td>
1976                     <p>
1977                       The number of lame servers the resolver detected
1978                       at the <code class="varname">domain</code> zone.
1979                       A server is detected to be lame either by an
1980                       invalid response or as a result of lookup in
1981                       BIND9's address database (ADB), where lame
1982                       servers are cached.
1983                     </p>
1984                   </td>
1985 </tr>
1986 <tr>
1987 <td>
1988                     <p><code class="varname">neterr</code></p>
1989                   </td>
1990 <td>
1991                     <p>
1992                       The number of erroneous results that the
1993                       resolver encountered in sending queries
1994                       at the <code class="varname">domain</code> zone.
1995                       One common case is the remote server is
1996                       unreachable and the resolver receives an ICMP
1997                       unreachable error message.
1998                     </p>
1999                   </td>
2000 </tr>
2001 <tr>
2002 <td>
2003                     <p><code class="varname">badresp</code></p>
2004                   </td>
2005 <td>
2006                     <p>
2007                       The number of unexpected responses (other than
2008                       <code class="varname">lame</code>) to queries sent by the
2009                       resolver at the <code class="varname">domain</code> zone.
2010                     </p>
2011                   </td>
2012 </tr>
2013 <tr>
2014 <td>
2015                     <p><code class="varname">adberr</code></p>
2016                   </td>
2017 <td>
2018                     <p>
2019                       Failures in finding remote server addresses
2020                       of the <code class="varname">domain</code> zone in the ADB.
2021                       One common case of this is that the remote
2022                       server's name does not have any address records.
2023                     </p>
2024                   </td>
2025 </tr>
2026 <tr>
2027 <td>
2028                     <p><code class="varname">findfail</code></p>
2029                   </td>
2030 <td>
2031                     <p>
2032                       Failures of resolving remote server addresses.
2033                       This is a total number of failures throughout
2034                       the resolution process.
2035                     </p>
2036                   </td>
2037 </tr>
2038 <tr>
2039 <td>
2040                     <p><code class="varname">valfail</code></p>
2041                   </td>
2042 <td>
2043                     <p>
2044                       Failures of DNSSEC validation.
2045                       Validation failures are counted throughout
2046                       the resolution process (not limited to
2047                       the <code class="varname">domain</code> zone), but should
2048                       only happen in <code class="varname">domain</code>.
2049                     </p>
2050                   </td>
2051 </tr>
2052 </tbody>
2053 </table></div>
2054 <p>
2055             At the debug levels of 3 or higher, the same messages
2056             as those at the debug 1 level are logged for other errors
2057             than SERVFAIL.
2058             Note that negative responses such as NXDOMAIN are not
2059             regarded as errors here.
2060           </p>
2061 <p>
2062             At the debug levels of 4 or higher, the same messages
2063             as those at the debug 2 level are logged for other errors
2064             than SERVFAIL.
2065             Unlike the above case of level 3, messages are logged for
2066             negative responses.
2067             This is because any unexpected results can be difficult to
2068             debug in the recursion case.
2069           </p>
2070 </div>
2071 </div>
2072 <div class="section">
2073 <div class="titlepage"><div><div><h3 class="title">
2074 <a name="lwres_grammar"></a><span class="command"><strong>lwres</strong></span> Statement Grammar</h3></div></div></div>
2075 <p>
2076            This is the grammar of the <span class="command"><strong>lwres</strong></span>
2077           statement in the <code class="filename">named.conf</code> file:
2078         </p>
2079 <pre class="programlisting"><span class="command"><strong>lwres</strong></span> {
2080     [<span class="optional"> listen-on { <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ;
2081                 [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; ... </span>] }; </span>]
2082     [<span class="optional"> view <em class="replaceable"><code>view_name</code></em>; </span>]
2083     [<span class="optional"> search { <em class="replaceable"><code>domain_name</code></em> ; [<span class="optional"> <em class="replaceable"><code>domain_name</code></em> ; ... </span>] }; </span>]
2084     [<span class="optional"> ndots <em class="replaceable"><code>number</code></em>; </span>]
2085 };
2086 </pre>
2087 </div>
2088 <div class="section">
2089 <div class="titlepage"><div><div><h3 class="title">
2090 <a name="lwres_statement"></a><span class="command"><strong>lwres</strong></span> Statement Definition and Usage</h3></div></div></div>
2091 <p>
2092           The <span class="command"><strong>lwres</strong></span> statement configures the
2093           name
2094           server to also act as a lightweight resolver server. (See
2095           <a class="xref" href="Bv9ARM.ch05.html#lwresd" title="Running a Resolver Daemon">the section called &#8220;Running a Resolver Daemon&#8221;</a>.)  There may be multiple
2096           <span class="command"><strong>lwres</strong></span> statements configuring
2097           lightweight resolver servers with different properties.
2098         </p>
2099 <p>
2100           The <span class="command"><strong>listen-on</strong></span> statement specifies a
2101           list of
2102           IPv4 addresses (and ports) that this instance of a lightweight
2103           resolver daemon
2104           should accept requests on.  If no port is specified, port 921 is
2105           used.
2106           If this statement is omitted, requests will be accepted on
2107           127.0.0.1,
2108           port 921.
2109         </p>
2110 <p>
2111           The <span class="command"><strong>view</strong></span> statement binds this
2112           instance of a
2113           lightweight resolver daemon to a view in the DNS namespace, so that
2114           the
2115           response will be constructed in the same manner as a normal DNS
2116           query
2117           matching this view.  If this statement is omitted, the default view
2118           is
2119           used, and if there is no default view, an error is triggered.
2120         </p>
2121 <p>
2122           The <span class="command"><strong>search</strong></span> statement is equivalent to
2123           the
2124           <span class="command"><strong>search</strong></span> statement in
2125           <code class="filename">/etc/resolv.conf</code>.  It provides a
2126           list of domains
2127           which are appended to relative names in queries.
2128         </p>
2129 <p>
2130           The <span class="command"><strong>ndots</strong></span> statement is equivalent to
2131           the
2132           <span class="command"><strong>ndots</strong></span> statement in
2133           <code class="filename">/etc/resolv.conf</code>.  It indicates the
2134           minimum
2135           number of dots in a relative domain name that should result in an
2136           exact match lookup before search path elements are appended.
2137         </p>
2138 </div>
2139 <div class="section">
2140 <div class="titlepage"><div><div><h3 class="title">
2141 <a name="masters_grammar"></a><span class="command"><strong>masters</strong></span> Statement Grammar</h3></div></div></div>
2142 <pre class="programlisting">
2143 <span class="command"><strong>masters</strong></span> <em class="replaceable"><code>name</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] { ( <em class="replaceable"><code>masters_list</code></em> |
2144       <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] };
2145 </pre>
2146 </div>
2147 <div class="section">
2148 <div class="titlepage"><div><div><h3 class="title">
2149 <a name="masters_statement"></a><span class="command"><strong>masters</strong></span> Statement Definition and
2150           Usage</h3></div></div></div>
2151 <p><span class="command"><strong>masters</strong></span>
2152           lists allow for a common set of masters to be easily used by
2153           multiple stub and slave zones in their <span class="command"><strong>masters</strong></span>
2154           or <span class="command"><strong>also-notify</strong></span> lists.
2155         </p>
2156 </div>
2157 <div class="section">
2158 <div class="titlepage"><div><div><h3 class="title">
2159 <a name="options_grammar"></a><span class="command"><strong>options</strong></span> Statement Grammar</h3></div></div></div>
2160 <p>
2161           This is the grammar of the <span class="command"><strong>options</strong></span>
2162           statement in the <code class="filename">named.conf</code> file:
2163         </p>
2164 <pre class="programlisting"><span class="command"><strong>options</strong></span> {
2165     [<span class="optional"> attach-cache <em class="replaceable"><code>cache_name</code></em>; </span>]
2166     [<span class="optional"> version <em class="replaceable"><code>version_string</code></em>; </span>]
2167     [<span class="optional"> hostname <em class="replaceable"><code>hostname_string</code></em>; </span>]
2168     [<span class="optional"> server-id <em class="replaceable"><code>server_id_string</code></em>; </span>]
2169     [<span class="optional"> directory <em class="replaceable"><code>path_name</code></em>; </span>]
2170     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2171     [<span class="optional"> managed-keys-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2172     [<span class="optional"> named-xfer <em class="replaceable"><code>path_name</code></em>; </span>]
2173     [<span class="optional"> tkey-gssapi-keytab <em class="replaceable"><code>path_name</code></em>; </span>]
2174     [<span class="optional"> tkey-gssapi-credential <em class="replaceable"><code>principal</code></em>; </span>]
2175     [<span class="optional"> tkey-domain <em class="replaceable"><code>domainname</code></em>; </span>]
2176     [<span class="optional"> tkey-dhkey <em class="replaceable"><code>key_name</code></em> <em class="replaceable"><code>key_tag</code></em>; </span>]
2177     [<span class="optional"> cache-file <em class="replaceable"><code>path_name</code></em>; </span>]
2178     [<span class="optional"> dump-file <em class="replaceable"><code>path_name</code></em>; </span>]
2179     [<span class="optional"> bindkeys-file <em class="replaceable"><code>path_name</code></em>; </span>]
2180     [<span class="optional"> secroots-file <em class="replaceable"><code>path_name</code></em>; </span>]
2181     [<span class="optional"> session-keyfile <em class="replaceable"><code>path_name</code></em>; </span>]
2182     [<span class="optional"> session-keyname <em class="replaceable"><code>key_name</code></em>; </span>]
2183     [<span class="optional"> session-keyalg <em class="replaceable"><code>algorithm_id</code></em>; </span>]
2184     [<span class="optional"> memstatistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2185     [<span class="optional"> memstatistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2186     [<span class="optional"> pid-file <em class="replaceable"><code>path_name</code></em>; </span>]
2187     [<span class="optional"> recursing-file <em class="replaceable"><code>path_name</code></em>; </span>]
2188     [<span class="optional"> statistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2189     [<span class="optional"> zone-statistics <em class="replaceable"><code>full</code></em> | <em class="replaceable"><code>terse</code></em> | <em class="replaceable"><code>none</code></em>; </span>]
2190     [<span class="optional"> auth-nxdomain <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2191     [<span class="optional"> deallocate-on-exit <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2192     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em>; </span>]
2193     [<span class="optional"> fake-iquery <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2194     [<span class="optional"> fetch-glue <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2195     [<span class="optional"> flush-zones-on-shutdown <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2196     [<span class="optional"> has-old-clients <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2197     [<span class="optional"> host-statistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2198     [<span class="optional"> host-statistics-max <em class="replaceable"><code>number</code></em>; </span>]
2199     [<span class="optional"> minimal-responses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2200     [<span class="optional"> multiple-cnames <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2201     [<span class="optional"> notify <em class="replaceable"><code>yes_or_no</code></em> | <em class="replaceable"><code>explicit</code></em> | <em class="replaceable"><code>master-only</code></em>; </span>]
2202     [<span class="optional"> recursion <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2203     [<span class="optional"> request-nsid <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2204     [<span class="optional"> rfc2308-type1 <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2205     [<span class="optional"> use-id-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2206     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2207     [<span class="optional"> ixfr-from-differences (<em class="replaceable"><code>yes_or_no</code></em> | <code class="constant">master</code> | <code class="constant">slave</code>); </span>]
2208     [<span class="optional"> auto-dnssec <code class="constant">allow</code>|<code class="constant">maintain</code>|<code class="constant">off</code>; </span>]
2209     [<span class="optional"> dnssec-enable <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2210     [<span class="optional"> dnssec-validation (<em class="replaceable"><code>yes_or_no</code></em> | <code class="constant">auto</code>); </span>]
2211     [<span class="optional"> dnssec-lookaside ( <em class="replaceable"><code>auto</code></em> |
2212                         <em class="replaceable"><code>no</code></em> |
2213                         <em class="replaceable"><code>domain</code></em> trust-anchor <em class="replaceable"><code>domain</code></em> ); </span>]
2214     [<span class="optional"> dnssec-must-be-secure <em class="replaceable"><code>domain yes_or_no</code></em>; </span>]
2215     [<span class="optional"> dnssec-accept-expired <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2216     [<span class="optional"> forward ( <em class="replaceable"><code>only</code></em> | <em class="replaceable"><code>first</code></em> ); </span>]
2217     [<span class="optional"> forwarders { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; ... </span>] }; </span>]
2218     [<span class="optional"> dual-stack-servers [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] {
2219         ( <em class="replaceable"><code>domain_name</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] |
2220           <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ) ;
2221         ... }; </span>]
2222     [<span class="optional"> check-names ( <em class="replaceable"><code>master</code></em> | <em class="replaceable"><code>slave</code></em> | <em class="replaceable"><code>response</code></em> )
2223         ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2224     [<span class="optional"> check-dup-records ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2225     [<span class="optional"> check-mx ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2226     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2227     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2228     [<span class="optional"> check-mx-cname ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2229     [<span class="optional"> check-srv-cname ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2230     [<span class="optional"> check-sibling <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2231     [<span class="optional"> check-spf ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2232     [<span class="optional"> allow-new-zones { <em class="replaceable"><code>yes_or_no</code></em> }; </span>]
2233     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2234     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2235     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2236     [<span class="optional"> allow-query-cache { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2237     [<span class="optional"> allow-query-cache-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2238     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2239     [<span class="optional"> allow-recursion { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2240     [<span class="optional"> allow-recursion-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2241     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2242     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2243     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2244     [<span class="optional"> dnssec-update-mode ( <em class="replaceable"><code>maintain</code></em> | <em class="replaceable"><code>no-resign</code></em> ); </span>]
2245     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2246     [<span class="optional"> dnssec-loadkeys-interval <em class="replaceable"><code>number</code></em>; </span>]
2247     [<span class="optional"> dnssec-secure-to-insecure <em class="replaceable"><code>yes_or_no</code></em> ;</span>]
2248     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2249     [<span class="optional"> allow-v6-synthesis { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2250     [<span class="optional"> blackhole { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2251     [<span class="optional"> no-case-compress { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2252     [<span class="optional"> use-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2253     [<span class="optional"> avoid-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2254     [<span class="optional"> use-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2255     [<span class="optional"> avoid-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2256     [<span class="optional"> listen-on [<span class="optional"> port <em class="replaceable"><code>ip_port</code></em> </span>] { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2257     [<span class="optional"> listen-on-v6 [<span class="optional"> port <em class="replaceable"><code>ip_port</code></em> </span>] { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2258     [<span class="optional"> query-source ( ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2259         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
2260         [<span class="optional"> address ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2261         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
2262     [<span class="optional"> query-source-v6 ( ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2263         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
2264         [<span class="optional"> address ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2265         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
2266     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2267     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
2268     [<span class="optional"> queryport-pool-updateinterval <em class="replaceable"><code>number</code></em>; </span>]
2269     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em>; </span>]
2270     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em>; </span>]
2271     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em>; </span>]
2272     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em>; </span>]
2273     [<span class="optional"> reserved-sockets <em class="replaceable"><code>number</code></em>; </span>]
2274     [<span class="optional"> recursive-clients <em class="replaceable"><code>number</code></em>; </span>]
2275     [<span class="optional"> tcp-clients <em class="replaceable"><code>number</code></em>; </span>]
2276     [<span class="optional"> clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2277     [<span class="optional"> max-clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2278     [<span class="optional"> fetches-per-server <em class="replaceable"><code>number</code></em> [<span class="optional"><em class="replaceable"><code>(drop | fail)</code></em></span>]; </span>]
2279     [<span class="optional"> fetch-quota-params <em class="replaceable"><code>number fixedpoint fixedpoint fixedpoint</code></em> ; </span>]
2280     [<span class="optional"> fetches-per-zone <em class="replaceable"><code>number</code></em> [<span class="optional"><em class="replaceable"><code>(drop | fail)</code></em></span>]; </span>]
2281     [<span class="optional"> serial-query-rate <em class="replaceable"><code>number</code></em>; </span>]
2282     [<span class="optional"> serial-queries <em class="replaceable"><code>number</code></em>; </span>]
2283     [<span class="optional"> tcp-listen-queue <em class="replaceable"><code>number</code></em>; </span>]
2284     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em>; </span>]
2285     [<span class="optional"> transfers-in  <em class="replaceable"><code>number</code></em>; </span>]
2286     [<span class="optional"> transfers-out <em class="replaceable"><code>number</code></em>; </span>]
2287     [<span class="optional"> transfers-per-ns <em class="replaceable"><code>number</code></em>; </span>]
2288     [<span class="optional"> transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
2289     [<span class="optional"> transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
2290     [<span class="optional"> alt-transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
2291     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
2292                              [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
2293     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2294     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
2295     [<span class="optional"> notify-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
2296     [<span class="optional"> notify-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
2297     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2298     [<span class="optional"> also-notify [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] { ( <em class="replaceable"><code>masters_list</code></em> | <em class="replaceable"><code>ip_addr</code></em>
2299                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
2300                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
2301     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em>; </span>]
2302     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
2303     [<span class="optional"> coresize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2304     [<span class="optional"> datasize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2305     [<span class="optional"> files <em class="replaceable"><code>size_spec</code></em> ; </span>]
2306     [<span class="optional"> stacksize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2307     [<span class="optional"> cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2308     [<span class="optional"> heartbeat-interval <em class="replaceable"><code>number</code></em>; </span>]
2309     [<span class="optional"> interface-interval <em class="replaceable"><code>number</code></em>; </span>]
2310     [<span class="optional"> statistics-interval <em class="replaceable"><code>number</code></em>; </span>]
2311     [<span class="optional"> topology { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2312     [<span class="optional"> sortlist { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2313     [<span class="optional"> rrset-order { <em class="replaceable"><code>order_spec</code></em> ; [<span class="optional"> <em class="replaceable"><code>order_spec</code></em> ; ... </span>] </span>] };
2314     [<span class="optional"> lame-ttl <em class="replaceable"><code>number</code></em>; </span>]
2315     [<span class="optional"> max-ncache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2316     [<span class="optional"> max-cache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2317     [<span class="optional"> serial-update-method <code class="constant">increment</code>|<code class="constant">unixtime</code>|<code class="constant">date</code>; </span>]
2318     [<span class="optional"> sig-validity-interval <em class="replaceable"><code>number</code></em> [<span class="optional"><em class="replaceable"><code>number</code></em></span>] ; </span>]
2319     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
2320     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
2321     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
2322     [<span class="optional"> min-roots <em class="replaceable"><code>number</code></em>; </span>]
2323     [<span class="optional"> use-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2324     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2325     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2326     [<span class="optional"> treat-cr-as-space <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2327     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2328     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2329     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2330     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2331     [<span class="optional"> port <em class="replaceable"><code>ip_port</code></em>; </span>]
2332     [<span class="optional"> additional-from-auth <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2333     [<span class="optional"> additional-from-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2334     [<span class="optional"> random-device <em class="replaceable"><code>path_name</code></em> ; </span>]
2335     [<span class="optional"> max-cache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2336     [<span class="optional"> match-mapped-addresses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2337     [<span class="optional"> filter-aaaa-on-v4 ( <em class="replaceable"><code>yes_or_no</code></em> | <em class="replaceable"><code>break-dnssec</code></em> ); </span>]
2338     [<span class="optional"> filter-aaaa { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2339     [<span class="optional"> dns64 <em class="replaceable"><code>ipv6-prefix</code></em> {
2340         [<span class="optional"> clients { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2341         [<span class="optional"> mapped { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2342         [<span class="optional"> exclude { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2343         [<span class="optional"> suffix <em class="replaceable"><code>IPv6-address</code></em>; </span>]
2344         [<span class="optional"> recursive-only <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2345         [<span class="optional"> break-dnssec <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2346     }; </span>];
2347     [<span class="optional"> dns64-server <em class="replaceable"><code>name</code></em> </span>]
2348     [<span class="optional"> dns64-contact <em class="replaceable"><code>name</code></em> </span>]
2349     [<span class="optional"> preferred-glue ( <em class="replaceable"><code>A</code></em> | <em class="replaceable"><code>AAAA</code></em> | <em class="replaceable"><code>NONE</code></em> ); </span>]
2350     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2351     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2352     [<span class="optional"> max-rsa-exponent-size <em class="replaceable"><code>number</code></em>; </span>]
2353     [<span class="optional"> root-delegation-only [<span class="optional"> exclude { <em class="replaceable"><code>namelist</code></em> } </span>] ; </span>]
2354     [<span class="optional"> querylog <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2355     [<span class="optional"> disable-algorithms <em class="replaceable"><code>domain</code></em> { <em class="replaceable"><code>algorithm</code></em>;
2356                                 [<span class="optional"> <em class="replaceable"><code>algorithm</code></em>; </span>] }; </span>]
2357     [<span class="optional"> acache-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2358     [<span class="optional"> acache-cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2359     [<span class="optional"> max-acache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2360     [<span class="optional"> max-recursion-depth <em class="replaceable"><code>number</code></em> ; </span>]
2361     [<span class="optional"> max-recursion-queries <em class="replaceable"><code>number</code></em> ; </span>]
2362     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
2363     [<span class="optional"> empty-server <em class="replaceable"><code>name</code></em> ; </span>]
2364     [<span class="optional"> empty-contact <em class="replaceable"><code>name</code></em> ; </span>]
2365     [<span class="optional"> empty-zones-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2366     [<span class="optional"> disable-empty-zone <em class="replaceable"><code>zone_name</code></em> ; </span>]
2367     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2368     [<span class="optional"> zero-no-soa-ttl-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2369     [<span class="optional"> resolver-query-timeout <em class="replaceable"><code>number</code></em> ; </span>]
2370     [<span class="optional"> deny-answer-addresses { <em class="replaceable"><code>address_match_list</code></em> } [<span class="optional"> except-from { <em class="replaceable"><code>namelist</code></em> } </span>];</span>]
2371     [<span class="optional"> deny-answer-aliases { <em class="replaceable"><code>namelist</code></em> } [<span class="optional"> except-from { <em class="replaceable"><code>namelist</code></em> } </span>];</span>]
2372     [<span class="optional"> rate-limit {
2373         [<span class="optional"> responses-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2374         [<span class="optional"> referrals-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2375         [<span class="optional"> nodata-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2376         [<span class="optional"> nxdomains-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2377         [<span class="optional"> errors-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2378         [<span class="optional"> all-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2379         [<span class="optional"> window <em class="replaceable"><code>number</code></em> ; </span>]
2380         [<span class="optional"> log-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2381         [<span class="optional"> qps-scale <em class="replaceable"><code>number</code></em> ; </span>]
2382         [<span class="optional"> ipv4-prefix-length <em class="replaceable"><code>number</code></em> ; </span>]
2383         [<span class="optional"> ipv6-prefix-length <em class="replaceable"><code>number</code></em> ; </span>]
2384         [<span class="optional"> slip <em class="replaceable"><code>number</code></em> ; </span>]
2385         [<span class="optional"> exempt-clients  { <em class="replaceable"><code>address_match_list</code></em> } ; </span>]
2386         [<span class="optional"> max-table-size <em class="replaceable"><code>number</code></em> ; </span>]
2387         [<span class="optional"> min-table-size <em class="replaceable"><code>number</code></em> ; </span>]
2388     } ; </span>]
2389     [<span class="optional"> response-policy {
2390         zone <em class="replaceable"><code>zone_name</code></em>
2391         [<span class="optional"> policy <em class="replaceable"><code>(given | disabled | passthru |
2392                   nxdomain | nodata | cname domain</code></em>) </span>]
2393         ; [<span class="optional">...</span>]
2394     } [<span class="optional"> recursive-only <em class="replaceable"><code>yes_or_no</code></em> </span>]
2395       [<span class="optional"> max-policy-ttl <em class="replaceable"><code>number</code></em> </span>]
2396       [<span class="optional"> break-dnssec <em class="replaceable"><code>yes_or_no</code></em> </span>]
2397       [<span class="optional"> min-ns-dots <em class="replaceable"><code>number</code></em> </span>]
2398     ; </span>]
2399 };
2400 </pre>
2401 </div>
2402 <div class="section">
2403 <div class="titlepage"><div><div><h3 class="title">
2404 <a name="options"></a><span class="command"><strong>options</strong></span> Statement Definition and
2405           Usage</h3></div></div></div>
2406 <p>
2407           The <span class="command"><strong>options</strong></span> statement sets up global
2408           options
2409           to be used by <acronym class="acronym">BIND</acronym>. This statement
2410           may appear only
2411           once in a configuration file. If there is no <span class="command"><strong>options</strong></span>
2412           statement, an options block with each option set to its default will
2413           be used.
2414         </p>
2415 <div class="variablelist"><dl class="variablelist">
2416 <dt><span class="term"><span class="command"><strong>attach-cache</strong></span></span></dt>
2417 <dd>
2418 <p>
2419                   Allows multiple views to share a single cache
2420                   database.
2421                   Each view has its own cache database by default, but
2422                   if multiple views have the same operational policy
2423                   for name resolution and caching, those views can
2424                   share a single cache to save memory and possibly
2425                   improve resolution efficiency by using this option.
2426                 </p>
2427 <p>
2428                   The <span class="command"><strong>attach-cache</strong></span> option
2429                   may also be specified in <span class="command"><strong>view</strong></span>
2430                   statements, in which case it overrides the
2431                   global <span class="command"><strong>attach-cache</strong></span> option.
2432                 </p>
2433 <p>
2434                   The <em class="replaceable"><code>cache_name</code></em> specifies
2435                   the cache to be shared.
2436                   When the <span class="command"><strong>named</strong></span> server configures
2437                   views which are supposed to share a cache, it
2438                   creates a cache with the specified name for the
2439                   first view of these sharing views.
2440                   The rest of the views will simply refer to the
2441                   already created cache.
2442                 </p>
2443 <p>
2444                   One common configuration to share a cache would be to
2445                   allow all views to share a single cache.
2446                   This can be done by specifying
2447                   the <span class="command"><strong>attach-cache</strong></span> as a global
2448                   option with an arbitrary name.
2449                 </p>
2450 <p>
2451                   Another possible operation is to allow a subset of
2452                   all views to share a cache while the others to
2453                   retain their own caches.
2454                   For example, if there are three views A, B, and C,
2455                   and only A and B should share a cache, specify the
2456                   <span class="command"><strong>attach-cache</strong></span> option as a view A (or
2457                   B)'s option, referring to the other view name:
2458                 </p>
2459 <pre class="programlisting">
2460   view "A" {
2461     // this view has its own cache
2462     ...
2463   };
2464   view "B" {
2465     // this view refers to A's cache
2466     attach-cache "A";
2467   };
2468   view "C" {
2469     // this view has its own cache
2470     ...
2471   };
2472 </pre>
2473 <p>
2474                   Views that share a cache must have the same policy
2475                   on configurable parameters that may affect caching.
2476                   The current implementation requires the following
2477                   configurable options be consistent among these
2478                   views:
2479                   <span class="command"><strong>check-names</strong></span>,
2480                   <span class="command"><strong>cleaning-interval</strong></span>,
2481                   <span class="command"><strong>dnssec-accept-expired</strong></span>,
2482                   <span class="command"><strong>dnssec-validation</strong></span>,
2483                   <span class="command"><strong>max-cache-ttl</strong></span>,
2484                   <span class="command"><strong>max-ncache-ttl</strong></span>,
2485                   <span class="command"><strong>max-cache-size</strong></span>, and
2486                   <span class="command"><strong>zero-no-soa-ttl</strong></span>.
2487                 </p>
2488 <p>
2489                   Note that there may be other parameters that may
2490                   cause confusion if they are inconsistent for
2491                   different views that share a single cache.
2492                   For example, if these views define different sets of
2493                   forwarders that can return different answers for the
2494                   same question, sharing the answer does not make
2495                   sense or could even be harmful.
2496                   It is administrator's responsibility to ensure
2497                   configuration differences in different views do
2498                   not cause disruption with a shared cache.
2499                 </p>
2500 </dd>
2501 <dt><span class="term"><span class="command"><strong>directory</strong></span></span></dt>
2502 <dd><p>
2503                 The working directory of the server.
2504                 Any non-absolute pathnames in the configuration file will be
2505                 taken
2506                 as relative to this directory. The default location for most
2507                 server
2508                 output files (e.g. <code class="filename">named.run</code>)
2509                 is this directory.
2510                 If a directory is not specified, the working directory
2511                 defaults to `<code class="filename">.</code>', the directory from
2512                 which the server
2513                 was started. The directory specified should be an absolute
2514                 path.
2515               </p></dd>
2516 <dt><span class="term"><span class="command"><strong>key-directory</strong></span></span></dt>
2517 <dd><p>
2518                 When performing dynamic update of secure zones, the
2519                 directory where the public and private DNSSEC key files
2520                 should be found, if different than the current working
2521                 directory.  (Note that this option has no effect on the
2522                 paths for files containing non-DNSSEC keys such as
2523                 <code class="filename">bind.keys</code>,
2524                 <code class="filename">rndc.key</code> or
2525                 <code class="filename">session.key</code>.)
2526               </p></dd>
2527 <dt><span class="term"><span class="command"><strong>managed-keys-directory</strong></span></span></dt>
2528 <dd>
2529 <p>
2530                 Specifies the directory in which to store the files that
2531                 track managed DNSSEC keys.  By default, this is the working
2532                 directory.
2533               </p>
2534 <p>
2535                 If <span class="command"><strong>named</strong></span> is not configured to use views,
2536                 then managed keys for the server will be tracked in a single
2537                 file called <code class="filename">managed-keys.bind</code>.
2538                 Otherwise, managed keys will be tracked in separate files,
2539                 one file per view; each file name will be the SHA256 hash
2540                 of the view name, followed by the extension
2541                 <code class="filename">.mkeys</code>.
2542               </p>
2543 </dd>
2544 <dt><span class="term"><span class="command"><strong>named-xfer</strong></span></span></dt>
2545 <dd><p>
2546                 <span class="emphasis"><em>This option is obsolete.</em></span> It
2547                 was used in <acronym class="acronym">BIND</acronym> 8 to specify
2548                 the pathname to the <span class="command"><strong>named-xfer</strong></span>
2549                 program.  In <acronym class="acronym">BIND</acronym> 9, no separate
2550                 <span class="command"><strong>named-xfer</strong></span> program is needed;
2551                 its functionality is built into the name server.
2552               </p></dd>
2553 <dt><span class="term"><span class="command"><strong>tkey-gssapi-keytab</strong></span></span></dt>
2554 <dd><p>
2555                 The KRB5 keytab file to use for GSS-TSIG updates. If
2556                 this option is set and tkey-gssapi-credential is not
2557                 set, then updates will be allowed with any key
2558                 matching a principal in the specified keytab.
2559               </p></dd>
2560 <dt><span class="term"><span class="command"><strong>tkey-gssapi-credential</strong></span></span></dt>
2561 <dd><p>
2562                 The security credential with which the server should
2563                 authenticate keys requested by the GSS-TSIG protocol.
2564                 Currently only Kerberos 5 authentication is available
2565                 and the credential is a Kerberos principal which the
2566                 server can acquire through the default system key
2567                 file, normally <code class="filename">/etc/krb5.keytab</code>.
2568                 The location keytab file can be overridden using the
2569                 tkey-gssapi-keytab option. Normally this principal is
2570                 of the form "<strong class="userinput"><code>DNS/</code></strong><code class="varname">server.domain</code>".
2571                 To use GSS-TSIG, <span class="command"><strong>tkey-domain</strong></span> must
2572                 also be set if a specific keytab is not set with
2573                 tkey-gssapi-keytab.
2574               </p></dd>
2575 <dt><span class="term"><span class="command"><strong>tkey-domain</strong></span></span></dt>
2576 <dd><p>
2577                 The domain appended to the names of all shared keys
2578                 generated with <span class="command"><strong>TKEY</strong></span>.  When a
2579                 client requests a <span class="command"><strong>TKEY</strong></span> exchange,
2580                 it may or may not specify the desired name for the
2581                 key. If present, the name of the shared key will
2582                 be <code class="varname">client specified part</code> +
2583                 <code class="varname">tkey-domain</code>.  Otherwise, the
2584                 name of the shared key will be <code class="varname">random hex
2585                 digits</code> + <code class="varname">tkey-domain</code>.
2586                 In most cases, the <span class="command"><strong>domainname</strong></span>
2587                 should be the server's domain name, or an otherwise
2588                 non-existent subdomain like
2589                 "_tkey.<code class="varname">domainname</code>".  If you are
2590                 using GSS-TSIG, this variable must be defined, unless
2591                 you specify a specific keytab using tkey-gssapi-keytab.
2592               </p></dd>
2593 <dt><span class="term"><span class="command"><strong>tkey-dhkey</strong></span></span></dt>
2594 <dd><p>
2595                 The Diffie-Hellman key used by the server
2596                 to generate shared keys with clients using the Diffie-Hellman
2597                 mode
2598                 of <span class="command"><strong>TKEY</strong></span>. The server must be
2599                 able to load the
2600                 public and private keys from files in the working directory.
2601                 In
2602                 most cases, the keyname should be the server's host name.
2603               </p></dd>
2604 <dt><span class="term"><span class="command"><strong>cache-file</strong></span></span></dt>
2605 <dd><p>
2606                 This is for testing only.  Do not use.
2607               </p></dd>
2608 <dt><span class="term"><span class="command"><strong>dump-file</strong></span></span></dt>
2609 <dd><p>
2610                 The pathname of the file the server dumps
2611                 the database to when instructed to do so with
2612                 <span class="command"><strong>rndc dumpdb</strong></span>.
2613                 If not specified, the default is <code class="filename">named_dump.db</code>.
2614               </p></dd>
2615 <dt><span class="term"><span class="command"><strong>memstatistics-file</strong></span></span></dt>
2616 <dd><p>
2617                 The pathname of the file the server writes memory
2618                 usage statistics to on exit. If not specified,
2619                 the default is <code class="filename">named.memstats</code>.
2620               </p></dd>
2621 <dt><span class="term"><span class="command"><strong>pid-file</strong></span></span></dt>
2622 <dd><p>
2623                 The pathname of the file the server writes its process ID
2624                 in. If not specified, the default is
2625                 <code class="filename">/var/run/named/named.pid</code>.
2626                 The PID file is used by programs that want to send signals to
2627                 the running
2628                 name server. Specifying <span class="command"><strong>pid-file none</strong></span> disables the
2629                 use of a PID file &#8212; no file will be written and any
2630                 existing one will be removed.  Note that <span class="command"><strong>none</strong></span>
2631                 is a keyword, not a filename, and therefore is not enclosed
2632                 in
2633                 double quotes.
2634               </p></dd>
2635 <dt><span class="term"><span class="command"><strong>recursing-file</strong></span></span></dt>
2636 <dd><p>
2637                 The pathname of the file the server dumps
2638                 the queries that are currently recursing when instructed
2639                 to do so with <span class="command"><strong>rndc recursing</strong></span>.
2640                 If not specified, the default is <code class="filename">named.recursing</code>.
2641               </p></dd>
2642 <dt><span class="term"><span class="command"><strong>statistics-file</strong></span></span></dt>
2643 <dd><p>
2644                 The pathname of the file the server appends statistics
2645                 to when instructed to do so using <span class="command"><strong>rndc stats</strong></span>.
2646                 If not specified, the default is <code class="filename">named.stats</code> in the
2647                 server's current directory.  The format of the file is
2648                 described
2649                 in <a class="xref" href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
2650               </p></dd>
2651 <dt><span class="term"><span class="command"><strong>bindkeys-file</strong></span></span></dt>
2652 <dd><p>
2653                 The pathname of a file to override the built-in trusted
2654                 keys provided by <span class="command"><strong>named</strong></span>.
2655                 See the discussion of <span class="command"><strong>dnssec-lookaside</strong></span>
2656                 and <span class="command"><strong>dnssec-validation</strong></span> for details.
2657                 If not specified, the default is
2658                 <code class="filename">/etc/bind.keys</code>.
2659               </p></dd>
2660 <dt><span class="term"><span class="command"><strong>secroots-file</strong></span></span></dt>
2661 <dd><p>
2662                 The pathname of the file the server dumps
2663                 security roots to when instructed to do so with
2664                 <span class="command"><strong>rndc secroots</strong></span>.
2665                 If not specified, the default is
2666                 <code class="filename">named.secroots</code>.
2667               </p></dd>
2668 <dt><span class="term"><span class="command"><strong>session-keyfile</strong></span></span></dt>
2669 <dd><p>
2670                 The pathname of the file into which to write a TSIG
2671                 session key generated by <span class="command"><strong>named</strong></span> for use by
2672                 <span class="command"><strong>nsupdate -l</strong></span>.  If not specified, the
2673                 default is <code class="filename">/var/run/named/session.key</code>.
2674                 (See <a class="xref" href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>, and in
2675                 particular the discussion of the
2676                 <span class="command"><strong>update-policy</strong></span> statement's
2677                 <strong class="userinput"><code>local</code></strong> option for more
2678                 information about this feature.)
2679               </p></dd>
2680 <dt><span class="term"><span class="command"><strong>session-keyname</strong></span></span></dt>
2681 <dd><p>
2682                 The key name to use for the TSIG session key.
2683                 If not specified, the default is "local-ddns".
2684               </p></dd>
2685 <dt><span class="term"><span class="command"><strong>session-keyalg</strong></span></span></dt>
2686 <dd><p>
2687                 The algorithm to use for the TSIG session key.
2688                 Valid values are hmac-sha1, hmac-sha224, hmac-sha256,
2689                 hmac-sha384, hmac-sha512 and hmac-md5.  If not
2690                 specified, the default is hmac-sha256.
2691               </p></dd>
2692 <dt><span class="term"><span class="command"><strong>port</strong></span></span></dt>
2693 <dd><p>
2694                 The UDP/TCP port number the server uses for
2695                 receiving and sending DNS protocol traffic.
2696                 The default is 53.  This option is mainly intended for server
2697                 testing;
2698                 a server using a port other than 53 will not be able to
2699                 communicate with
2700                 the global DNS.
2701               </p></dd>
2702 <dt><span class="term"><span class="command"><strong>random-device</strong></span></span></dt>
2703 <dd><p>
2704                 The source of entropy to be used by the server.  Entropy is
2705                 primarily needed
2706                 for DNSSEC operations, such as TKEY transactions and dynamic
2707                 update of signed
2708                 zones.  This options specifies the device (or file) from which
2709                 to read
2710                 entropy.  If this is a file, operations requiring entropy will
2711                 fail when the
2712                 file has been exhausted.  If not specified, the default value
2713                 is
2714                 <code class="filename">/dev/random</code>
2715                 (or equivalent) when present, and none otherwise.  The
2716                 <span class="command"><strong>random-device</strong></span> option takes
2717                 effect during
2718                 the initial configuration load at server startup time and
2719                 is ignored on subsequent reloads.
2720               </p></dd>
2721 <dt><span class="term"><span class="command"><strong>preferred-glue</strong></span></span></dt>
2722 <dd><p>
2723                 If specified, the listed type (A or AAAA) will be emitted
2724                 before other glue
2725                 in the additional section of a query response.
2726                 The default is to prefer A records when responding
2727                 to queries that arrived via IPv4 and AAAA when
2728                 responding to queries that arrived via IPv6.
2729               </p></dd>
2730 <dt>
2731 <a name="root_delegation_only"></a><span class="term"><span class="command"><strong>root-delegation-only</strong></span></span>
2732 </dt>
2733 <dd>
2734 <p>
2735                 Turn on enforcement of delegation-only in TLDs
2736                 (top level domains) and root zones with an optional
2737                 exclude list.
2738               </p>
2739 <p>
2740                 DS queries are expected to be made to and be answered by
2741                 delegation only zones.  Such queries and responses are
2742                 treated as an exception to delegation-only processing
2743                 and are not converted to NXDOMAIN responses provided
2744                 a CNAME is not discovered at the query name.
2745               </p>
2746 <p>
2747                 If a delegation only zone server also serves a child
2748                 zone it is not always possible to determine whether
2749                 an answer comes from the delegation only zone or the
2750                 child zone.  SOA NS and DNSKEY records are apex
2751                 only records and a matching response that contains
2752                 these records or DS is treated as coming from a
2753                 child zone.  RRSIG records are also examined to see
2754                 if they are signed by a child zone or not.  The
2755                 authority section is also examined to see if there
2756                 is evidence that the answer is from the child zone.
2757                 Answers that are determined to be from a child zone
2758                 are not converted to NXDOMAIN responses.  Despite
2759                 all these checks there is still a possibility of
2760                 false negatives when a child zone is being served.
2761               </p>
2762 <p>
2763                 Similarly false positives can arise from empty nodes
2764                 (no records at the name) in the delegation only zone
2765                 when the query type is not ANY.
2766               </p>
2767 <p>
2768                 Note some TLDs are not delegation only (e.g. "DE", "LV",
2769                 "US" and "MUSEUM").  This list is not exhaustive.
2770               </p>
2771 <pre class="programlisting">
2772 options {
2773         root-delegation-only exclude { "de"; "lv"; "us"; "museum"; };
2774 };
2775 </pre>
2776 </dd>
2777 <dt><span class="term"><span class="command"><strong>disable-algorithms</strong></span></span></dt>
2778 <dd><p>
2779                 Disable the specified DNSSEC algorithms at and below the
2780                 specified name.
2781                 Multiple <span class="command"><strong>disable-algorithms</strong></span>
2782                 statements are allowed.
2783                 Only the most specific will be applied.
2784               </p></dd>
2785 <dt><span class="term"><span class="command"><strong>dnssec-lookaside</strong></span></span></dt>
2786 <dd>
2787 <p>
2788                 When set, <span class="command"><strong>dnssec-lookaside</strong></span> provides the
2789                 validator with an alternate method to validate DNSKEY
2790                 records at the top of a zone.  When a DNSKEY is at or
2791                 below a domain specified by the deepest
2792                 <span class="command"><strong>dnssec-lookaside</strong></span>, and the normal DNSSEC
2793                 validation has left the key untrusted, the trust-anchor
2794                 will be appended to the key name and a DLV record will be
2795                 looked up to see if it can validate the key.  If the DLV
2796                 record validates a DNSKEY (similarly to the way a DS
2797                 record does) the DNSKEY RRset is deemed to be trusted.
2798               </p>
2799 <p>
2800                 If <span class="command"><strong>dnssec-lookaside</strong></span> is set to
2801                 <strong class="userinput"><code>auto</code></strong>, then built-in default
2802                 values for the DLV domain and trust anchor will be
2803                 used, along with a built-in key for validation.
2804               </p>
2805 <p>
2806                 If <span class="command"><strong>dnssec-lookaside</strong></span> is set to
2807                 <strong class="userinput"><code>no</code></strong>, then dnssec-lookaside
2808                 is not used.
2809               </p>
2810 <p>
2811                 The default DLV key is stored in the file
2812                 <code class="filename">bind.keys</code>;
2813                 <span class="command"><strong>named</strong></span> will load that key at
2814                 startup if <span class="command"><strong>dnssec-lookaside</strong></span> is set to
2815                 <code class="constant">auto</code>.  A copy of the file is
2816                 installed along with <acronym class="acronym">BIND</acronym> 9, and is
2817                 current as of the release date.  If the DLV key expires, a
2818                 new copy of <code class="filename">bind.keys</code> can be downloaded
2819                 from <a class="link" href="https://www.isc.org/solutions/dlv/" target="_top">https://www.isc.org/solutions/dlv/</a>.
2820               </p>
2821 <p>
2822                 (To prevent problems if <code class="filename">bind.keys</code> is
2823                 not found, the current key is also compiled in to
2824                 <span class="command"><strong>named</strong></span>.  Relying on this is not
2825                 recommended, however, as it requires <span class="command"><strong>named</strong></span>
2826                 to be recompiled with a new key when the DLV key expires.)
2827               </p>
2828 <p>
2829                 NOTE: <span class="command"><strong>named</strong></span> only loads certain specific
2830                 keys from <code class="filename">bind.keys</code>:  those for the
2831                 DLV zone and for the DNS root zone.  The file cannot be
2832                 used to store keys for other zones.
2833               </p>
2834 </dd>
2835 <dt><span class="term"><span class="command"><strong>dnssec-must-be-secure</strong></span></span></dt>
2836 <dd><p>
2837                 Specify hierarchies which must be or may not be secure
2838                 (signed and validated).  If <strong class="userinput"><code>yes</code></strong>,
2839                 then <span class="command"><strong>named</strong></span> will only accept answers if
2840                 they are secure.  If <strong class="userinput"><code>no</code></strong>, then normal
2841                 DNSSEC validation applies allowing for insecure answers to
2842                 be accepted.  The specified domain must be under a
2843                 <span class="command"><strong>trusted-keys</strong></span> or
2844                 <span class="command"><strong>managed-keys</strong></span> statement, or
2845                 <span class="command"><strong>dnssec-lookaside</strong></span> must be active.
2846               </p></dd>
2847 <dt><span class="term"><span class="command"><strong>dns64</strong></span></span></dt>
2848 <dd>
2849 <p>
2850                 This directive instructs <span class="command"><strong>named</strong></span> to
2851                 return mapped IPv4 addresses to AAAA queries when
2852                 there are no AAAA records.  It is intended to be
2853                 used in conjunction with a NAT64.  Each
2854                 <span class="command"><strong>dns64</strong></span> defines one DNS64 prefix.
2855                 Multiple DNS64 prefixes can be defined.
2856               </p>
2857 <p>
2858                 Compatible IPv6 prefixes have lengths of 32, 40, 48, 56,
2859                 64 and 96 as per RFC 6052.
2860               </p>
2861 <p>
2862                 Additionally a reverse IP6.ARPA zone will be created for
2863                 the prefix to provide a mapping from the IP6.ARPA names
2864                 to the corresponding IN-ADDR.ARPA names using synthesized
2865                 CNAMEs.  <span class="command"><strong>dns64-server</strong></span> and
2866                 <span class="command"><strong>dns64-contact</strong></span> can be used to specify
2867                 the name of the server and contact for the zones. These
2868                 are settable at the view / options level.  These are
2869                 not settable on a per-prefix basis.
2870               </p>
2871 <p>
2872                 Each <span class="command"><strong>dns64</strong></span> supports an optional
2873                 <span class="command"><strong>clients</strong></span> ACL that determines which
2874                 clients are affected by this directive.  If not defined,
2875                 it defaults to <strong class="userinput"><code>any;</code></strong>.
2876               </p>
2877 <p>
2878                 Each <span class="command"><strong>dns64</strong></span> supports an optional
2879                 <span class="command"><strong>mapped</strong></span> ACL that selects which
2880                 IPv4 addresses are to be mapped in the corresponding
2881                 A RRset.  If not defined it defaults to
2882                 <strong class="userinput"><code>any;</code></strong>.
2883               </p>
2884 <p>
2885                 Normally, DNS64 won't apply to a domain name that
2886                 owns one or more AAAA records; these records will
2887                 simply be returned.  The optional
2888                 <span class="command"><strong>exclude</strong></span> ACL allows specification
2889                 of a list of IPv6 addresses that will be ignored
2890                 if they appear in a domain name's AAAA records, and
2891                 DNS64 will be applied to any A records the domain
2892                 name owns.  If not defined, <span class="command"><strong>exclude</strong></span>
2893                 defaults to none.
2894               </p>
2895 <p>
2896                 A optional <span class="command"><strong>suffix</strong></span> can also
2897                 be defined to set the bits trailing the mapped
2898                 IPv4 address bits.  By default these bits are
2899                 set to <strong class="userinput"><code>::</code></strong>.  The bits
2900                 matching the prefix and mapped IPv4 address
2901                 must be zero.
2902               </p>
2903 <p>
2904                 If <span class="command"><strong>recursive-only</strong></span> is set to
2905                 <span class="command"><strong>yes</strong></span> the DNS64 synthesis will
2906                 only happen for recursive queries.  The default
2907                 is <span class="command"><strong>no</strong></span>.
2908               </p>
2909 <p>
2910                 If <span class="command"><strong>break-dnssec</strong></span> is set to
2911                 <span class="command"><strong>yes</strong></span> the DNS64 synthesis will
2912                 happen even if the result, if validated, would
2913                 cause a DNSSEC validation failure.  If this option
2914                 is set to <span class="command"><strong>no</strong></span> (the default), the DO
2915                 is set on the incoming query, and there are RRSIGs on
2916                 the applicable records, then synthesis will not happen.
2917               </p>
2918 <pre class="programlisting">
2919         acl rfc1918 { 10/8; 192.168/16; 172.16/12; };
2920
2921         dns64 64:FF9B::/96 {
2922                 clients { any; };
2923                 mapped { !rfc1918; any; };
2924                 exclude { 64:FF9B::/96; ::ffff:0000:0000/96; };
2925                 suffix ::;
2926         };
2927 </pre>
2928 </dd>
2929 <dt><span class="term"><span class="command"><strong>dnssec-loadkeys-interval</strong></span></span></dt>
2930 <dd><p>
2931                   When a zone is configured with <span class="command"><strong>auto-dnssec
2932                   maintain;</strong></span> its key repository must be checked
2933                   periodically to see if any new keys have been added
2934                   or any existing keys' timing metadata has been updated
2935                   (see <a class="xref" href="man.dnssec-keygen.html" title="dnssec-keygen"><span class="refentrytitle"><span class="application">dnssec-keygen</span></span>(8)</a> and
2936                   <a class="xref" href="man.dnssec-settime.html" title="dnssec-settime"><span class="refentrytitle"><span class="application">dnssec-settime</span></span>(8)</a>).  The
2937                   <span class="command"><strong>dnssec-loadkeys-interval</strong></span> option
2938                   sets the frequency of automatic repository checks, in
2939                   minutes.  The default is <code class="literal">60</code> (1 hour),
2940                   the minimum is <code class="literal">1</code> (1 minute), and the
2941                   maximum is <code class="literal">1440</code> (24 hours); any higher
2942                   value is silently reduced.
2943                 </p></dd>
2944 <dt><span class="term"><span class="command"><strong>dnssec-update-mode</strong></span></span></dt>
2945 <dd>
2946 <p>
2947                   If this option is set to its default value of
2948                   <code class="literal">maintain</code> in a zone of type
2949                   <code class="literal">master</code> which is DNSSEC-signed
2950                   and configured to allow dynamic updates (see
2951                   <a class="xref" href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>), and
2952                   if <span class="command"><strong>named</strong></span> has access to the
2953                   private signing key(s) for the zone, then
2954                   <span class="command"><strong>named</strong></span> will automatically sign all new
2955                   or changed records and maintain signatures for the zone
2956                   by regenerating RRSIG records whenever they approach
2957                   their expiration date.
2958                 </p>
2959 <p>
2960                   If the option is changed to <code class="literal">no-resign</code>,
2961                   then <span class="command"><strong>named</strong></span> will sign all new or
2962                   changed records, but scheduled maintenance of
2963                   signatures is disabled.
2964                 </p>
2965 <p>
2966                   With either of these settings, <span class="command"><strong>named</strong></span>
2967                   will reject updates to a DNSSEC-signed zone when the
2968                   signing keys are inactive or unavailable to
2969                   <span class="command"><strong>named</strong></span>.  (A planned third option,
2970                   <code class="literal">external</code>, will disable all automatic
2971                   signing and allow DNSSEC data to be submitted into a zone
2972                   via dynamic update; this is not yet implemented.)
2973                 </p>
2974 </dd>
2975 <dt><span class="term"><span class="command"><strong>serial-update-method</strong></span></span></dt>
2976 <dd>
2977 <p>
2978                 Zones configured for dynamic DNS may use this
2979                 option to set the update method that will be used for
2980                 the zone serial number in the SOA record.
2981               </p>
2982 <p>
2983                 With the default setting of
2984                 <span class="command"><strong>serial-update-method increment;</strong></span>, the
2985                 SOA serial number will be incremented by one each time
2986                 the zone is updated.
2987               </p>
2988 <p>
2989                 When set to
2990                 <span class="command"><strong>serial-update-method unixtime;</strong></span>, the
2991                 SOA serial number will be set to the number of seconds
2992                 since the UNIX epoch, unless the serial number is
2993                 already greater than or equal to that value, in which
2994                 case it is simply incremented by one.
2995               </p>
2996 </dd>
2997 <dt><span class="term"><span class="command"><strong>zone-statistics</strong></span></span></dt>
2998 <dd>
2999 <p>
3000                 If <strong class="userinput"><code>full</code></strong>, the server will collect
3001                 statistical data on all zones (unless specifically
3002                 turned off on a per-zone basis by specifying
3003                 <span class="command"><strong>zone-statistics terse</strong></span> or
3004                 <span class="command"><strong>zone-statistics none</strong></span>
3005                 in the <span class="command"><strong>zone</strong></span> statement).
3006                 The default is <strong class="userinput"><code>terse</code></strong>, providing
3007                 minimal statistics on zones (including name and
3008                 current serial number, but not query type
3009                 counters).
3010               </p>
3011 <p>
3012                 These statistics may be accessed via the
3013                 <span class="command"><strong>statistics-channel</strong></span> or
3014                 using <span class="command"><strong>rndc stats</strong></span>, which
3015                 will dump them to the file listed
3016                 in the <span class="command"><strong>statistics-file</strong></span>.  See
3017                 also <a class="xref" href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
3018               </p>
3019 <p>
3020                 For backward compatibility with earlier versions
3021                 of BIND 9, the <span class="command"><strong>zone-statistics</strong></span>
3022                 option can also accept <strong class="userinput"><code>yes</code></strong>
3023                 or <strong class="userinput"><code>no</code></strong>, which have the same
3024                 effect as <strong class="userinput"><code>full</code></strong> and
3025                 <strong class="userinput"><code>terse</code></strong>, respectively.
3026               </p>
3027 </dd>
3028 </dl></div>
3029 <div class="section">
3030 <div class="titlepage"><div><div><h4 class="title">
3031 <a name="boolean_options"></a>Boolean Options</h4></div></div></div>
3032 <div class="variablelist"><dl class="variablelist">
3033 <dt><span class="term"><span class="command"><strong>allow-new-zones</strong></span></span></dt>
3034 <dd><p>
3035                   If <strong class="userinput"><code>yes</code></strong>, then zones can be
3036                   added at runtime via <span class="command"><strong>rndc addzone</strong></span>
3037                   or deleted via <span class="command"><strong>rndc delzone</strong></span>.
3038                   The default is <strong class="userinput"><code>no</code></strong>.
3039                 </p></dd>
3040 <dt><span class="term"><span class="command"><strong>auth-nxdomain</strong></span></span></dt>
3041 <dd><p>
3042                   If <strong class="userinput"><code>yes</code></strong>, then the <span class="command"><strong>AA</strong></span> bit
3043                   is always set on NXDOMAIN responses, even if the server is
3044                   not actually
3045                   authoritative. The default is <strong class="userinput"><code>no</code></strong>;
3046                   this is
3047                   a change from <acronym class="acronym">BIND</acronym> 8. If you
3048                   are using very old DNS software, you
3049                   may need to set it to <strong class="userinput"><code>yes</code></strong>.
3050                 </p></dd>
3051 <dt><span class="term"><span class="command"><strong>deallocate-on-exit</strong></span></span></dt>
3052 <dd><p>
3053                   This option was used in <acronym class="acronym">BIND</acronym>
3054                   8 to enable checking
3055                   for memory leaks on exit. <acronym class="acronym">BIND</acronym> 9 ignores the option and always performs
3056                   the checks.
3057                 </p></dd>
3058 <dt><span class="term"><span class="command"><strong>memstatistics</strong></span></span></dt>
3059 <dd><p>
3060                   Write memory statistics to the file specified by
3061                   <span class="command"><strong>memstatistics-file</strong></span> at exit.
3062                   The default is <strong class="userinput"><code>no</code></strong> unless
3063                   '-m record' is specified on the command line in
3064                   which case it is <strong class="userinput"><code>yes</code></strong>.
3065                 </p></dd>
3066 <dt><span class="term"><span class="command"><strong>dialup</strong></span></span></dt>
3067 <dd>
3068 <p>
3069                   If <strong class="userinput"><code>yes</code></strong>, then the
3070                   server treats all zones as if they are doing zone transfers
3071                   across
3072                   a dial-on-demand dialup link, which can be brought up by
3073                   traffic
3074                   originating from this server. This has different effects
3075                   according
3076                   to zone type and concentrates the zone maintenance so that
3077                   it all
3078                   happens in a short interval, once every <span class="command"><strong>heartbeat-interval</strong></span> and
3079                   hopefully during the one call. It also suppresses some of
3080                   the normal
3081                   zone maintenance traffic. The default is <strong class="userinput"><code>no</code></strong>.
3082                 </p>
3083 <p>
3084                   The <span class="command"><strong>dialup</strong></span> option
3085                   may also be specified in the <span class="command"><strong>view</strong></span> and
3086                   <span class="command"><strong>zone</strong></span> statements,
3087                   in which case it overrides the global <span class="command"><strong>dialup</strong></span>
3088                   option.
3089                 </p>
3090 <p>
3091                   If the zone is a master zone, then the server will send out a
3092                   NOTIFY
3093                   request to all the slaves (default). This should trigger the
3094                   zone serial
3095                   number check in the slave (providing it supports NOTIFY)
3096                   allowing the slave
3097                   to verify the zone while the connection is active.
3098                   The set of servers to which NOTIFY is sent can be controlled
3099                   by
3100                   <span class="command"><strong>notify</strong></span> and <span class="command"><strong>also-notify</strong></span>.
3101                 </p>
3102 <p>
3103                   If the
3104                   zone is a slave or stub zone, then the server will suppress
3105                   the regular
3106                   "zone up to date" (refresh) queries and only perform them
3107                   when the
3108                   <span class="command"><strong>heartbeat-interval</strong></span> expires in
3109                   addition to sending
3110                   NOTIFY requests.
3111                 </p>
3112 <p>
3113                   Finer control can be achieved by using
3114                   <strong class="userinput"><code>notify</code></strong> which only sends NOTIFY
3115                   messages,
3116                   <strong class="userinput"><code>notify-passive</code></strong> which sends NOTIFY
3117                   messages and
3118                   suppresses the normal refresh queries, <strong class="userinput"><code>refresh</code></strong>
3119                   which suppresses normal refresh processing and sends refresh
3120                   queries
3121                   when the <span class="command"><strong>heartbeat-interval</strong></span>
3122                   expires, and
3123                   <strong class="userinput"><code>passive</code></strong> which just disables normal
3124                   refresh
3125                   processing.
3126                 </p>
3127 <div class="informaltable"><table border="1">
3128 <colgroup>
3129 <col width="1.150in" class="1">
3130 <col width="1.150in" class="2">
3131 <col width="1.150in" class="3">
3132 <col width="1.150in" class="4">
3133 </colgroup>
3134 <tbody>
3135 <tr>
3136 <td>
3137                           <p>
3138                             dialup mode
3139                           </p>
3140                         </td>
3141 <td>
3142                           <p>
3143                             normal refresh
3144                           </p>
3145                         </td>
3146 <td>
3147                           <p>
3148                             heart-beat refresh
3149                           </p>
3150                         </td>
3151 <td>
3152                           <p>
3153                             heart-beat notify
3154                           </p>
3155                         </td>
3156 </tr>
3157 <tr>
3158 <td>
3159                           <p><span class="command"><strong>no</strong></span> (default)</p>
3160                         </td>
3161 <td>
3162                           <p>
3163                             yes
3164                           </p>
3165                         </td>
3166 <td>
3167                           <p>
3168                             no
3169                           </p>
3170                         </td>
3171 <td>
3172                           <p>
3173                             no
3174                           </p>
3175                         </td>
3176 </tr>
3177 <tr>
3178 <td>
3179                           <p><span class="command"><strong>yes</strong></span></p>
3180                         </td>
3181 <td>
3182                           <p>
3183                             no
3184                           </p>
3185                         </td>
3186 <td>
3187                           <p>
3188                             yes
3189                           </p>
3190                         </td>
3191 <td>
3192                           <p>
3193                             yes
3194                           </p>
3195                         </td>
3196 </tr>
3197 <tr>
3198 <td>
3199                           <p><span class="command"><strong>notify</strong></span></p>
3200                         </td>
3201 <td>
3202                           <p>
3203                             yes
3204                           </p>
3205                         </td>
3206 <td>
3207                           <p>
3208                             no
3209                           </p>
3210                         </td>
3211 <td>
3212                           <p>
3213                             yes
3214                           </p>
3215                         </td>
3216 </tr>
3217 <tr>
3218 <td>
3219                           <p><span class="command"><strong>refresh</strong></span></p>
3220                         </td>
3221 <td>
3222                           <p>
3223                             no
3224                           </p>
3225                         </td>
3226 <td>
3227                           <p>
3228                             yes
3229                           </p>
3230                         </td>
3231 <td>
3232                           <p>
3233                             no
3234                           </p>
3235                         </td>
3236 </tr>
3237 <tr>
3238 <td>
3239                           <p><span class="command"><strong>passive</strong></span></p>
3240                         </td>
3241 <td>
3242                           <p>
3243                             no
3244                           </p>
3245                         </td>
3246 <td>
3247                           <p>
3248                             no
3249                           </p>
3250                         </td>
3251 <td>
3252                           <p>
3253                             no
3254                           </p>
3255                         </td>
3256 </tr>
3257 <tr>
3258 <td>
3259                           <p><span class="command"><strong>notify-passive</strong></span></p>
3260                         </td>
3261 <td>
3262                           <p>
3263                             no
3264                           </p>
3265                         </td>
3266 <td>
3267                           <p>
3268                             no
3269                           </p>
3270                         </td>
3271 <td>
3272                           <p>
3273                             yes
3274                           </p>
3275                         </td>
3276 </tr>
3277 </tbody>
3278 </table></div>
3279 <p>
3280                   Note that normal NOTIFY processing is not affected by
3281                   <span class="command"><strong>dialup</strong></span>.
3282                 </p>
3283 </dd>
3284 <dt><span class="term"><span class="command"><strong>fake-iquery</strong></span></span></dt>
3285 <dd><p>
3286                   In <acronym class="acronym">BIND</acronym> 8, this option
3287                   enabled simulating the obsolete DNS query type
3288                   IQUERY. <acronym class="acronym">BIND</acronym> 9 never does
3289                   IQUERY simulation.
3290                 </p></dd>
3291 <dt><span class="term"><span class="command"><strong>fetch-glue</strong></span></span></dt>
3292 <dd><p>
3293                   This option is obsolete.
3294                   In BIND 8, <strong class="userinput"><code>fetch-glue yes</code></strong>
3295                   caused the server to attempt to fetch glue resource records
3296                   it
3297                   didn't have when constructing the additional
3298                   data section of a response.  This is now considered a bad
3299                   idea
3300                   and BIND 9 never does it.
3301                 </p></dd>
3302 <dt><span class="term"><span class="command"><strong>flush-zones-on-shutdown</strong></span></span></dt>
3303 <dd><p>
3304                   When the nameserver exits due receiving SIGTERM,
3305                   flush or do not flush any pending zone writes.  The default
3306                   is
3307                   <span class="command"><strong>flush-zones-on-shutdown</strong></span> <strong class="userinput"><code>no</code></strong>.
3308                 </p></dd>
3309 <dt><span class="term"><span class="command"><strong>has-old-clients</strong></span></span></dt>
3310 <dd><p>
3311                   This option was incorrectly implemented
3312                   in <acronym class="acronym">BIND</acronym> 8, and is ignored by <acronym class="acronym">BIND</acronym> 9.
3313                   To achieve the intended effect
3314                   of
3315                   <span class="command"><strong>has-old-clients</strong></span> <strong class="userinput"><code>yes</code></strong>, specify
3316                   the two separate options <span class="command"><strong>auth-nxdomain</strong></span> <strong class="userinput"><code>yes</code></strong>
3317                   and <span class="command"><strong>rfc2308-type1</strong></span> <strong class="userinput"><code>no</code></strong> instead.
3318                 </p></dd>
3319 <dt><span class="term"><span class="command"><strong>host-statistics</strong></span></span></dt>
3320 <dd><p>
3321                   In BIND 8, this enables keeping of
3322                   statistics for every host that the name server interacts
3323                   with.
3324                   Not implemented in BIND 9.
3325                 </p></dd>
3326 <dt><span class="term"><span class="command"><strong>maintain-ixfr-base</strong></span></span></dt>
3327 <dd><p>
3328                   <span class="emphasis"><em>This option is obsolete</em></span>.
3329                   It was used in <acronym class="acronym">BIND</acronym> 8 to
3330                   determine whether a transaction log was
3331                   kept for Incremental Zone Transfer. <acronym class="acronym">BIND</acronym> 9 maintains a transaction
3332                   log whenever possible.  If you need to disable outgoing
3333                   incremental zone
3334                   transfers, use <span class="command"><strong>provide-ixfr</strong></span> <strong class="userinput"><code>no</code></strong>.
3335                 </p></dd>
3336 <dt><span class="term"><span class="command"><strong>minimal-responses</strong></span></span></dt>
3337 <dd><p>
3338                   If <strong class="userinput"><code>yes</code></strong>, then when generating
3339                   responses the server will only add records to the authority
3340                   and additional data sections when they are required (e.g.
3341                   delegations, negative responses).  This may improve the
3342                   performance of the server.
3343                   The default is <strong class="userinput"><code>no</code></strong>.
3344                 </p></dd>
3345 <dt><span class="term"><span class="command"><strong>multiple-cnames</strong></span></span></dt>
3346 <dd><p>
3347                   This option was used in <acronym class="acronym">BIND</acronym> 8 to allow
3348                   a domain name to have multiple CNAME records in violation of
3349                   the DNS standards.  <acronym class="acronym">BIND</acronym> 9.2 onwards
3350                   always strictly enforces the CNAME rules both in master
3351                   files and dynamic updates.
3352                 </p></dd>
3353 <dt><span class="term"><span class="command"><strong>notify</strong></span></span></dt>
3354 <dd>
3355 <p>
3356                   If <strong class="userinput"><code>yes</code></strong> (the default),
3357                   DNS NOTIFY messages are sent when a zone the server is
3358                   authoritative for
3359                   changes, see <a class="xref" href="Bv9ARM.ch04.html#notify" title="Notify">the section called &#8220;Notify&#8221;</a>.  The messages are
3360                   sent to the
3361                   servers listed in the zone's NS records (except the master
3362                   server identified
3363                   in the SOA MNAME field), and to any servers listed in the
3364                   <span class="command"><strong>also-notify</strong></span> option.
3365                 </p>
3366 <p>
3367                   If <strong class="userinput"><code>master-only</code></strong>, notifies are only
3368                   sent
3369                   for master zones.
3370                   If <strong class="userinput"><code>explicit</code></strong>, notifies are sent only
3371                   to
3372                   servers explicitly listed using <span class="command"><strong>also-notify</strong></span>.
3373                   If <strong class="userinput"><code>no</code></strong>, no notifies are sent.
3374                 </p>
3375 <p>
3376                   The <span class="command"><strong>notify</strong></span> option may also be
3377                   specified in the <span class="command"><strong>zone</strong></span>
3378                   statement,
3379                   in which case it overrides the <span class="command"><strong>options notify</strong></span> statement.
3380                   It would only be necessary to turn off this option if it
3381                   caused slaves
3382                   to crash.
3383                 </p>
3384 </dd>
3385 <dt><span class="term"><span class="command"><strong>notify-to-soa</strong></span></span></dt>
3386 <dd><p>
3387                   If <strong class="userinput"><code>yes</code></strong> do not check the nameservers
3388                   in the NS RRset against the SOA MNAME.  Normally a NOTIFY
3389                   message is not sent to the SOA MNAME (SOA ORIGIN) as it is
3390                   supposed to contain the name of the ultimate master.
3391                   Sometimes, however, a slave is listed as the SOA MNAME in
3392                   hidden master configurations and in that case you would
3393                   want the ultimate master to still send NOTIFY messages to
3394                   all the nameservers listed in the NS RRset.
3395                 </p></dd>
3396 <dt><span class="term"><span class="command"><strong>recursion</strong></span></span></dt>
3397 <dd><p>
3398                   If <strong class="userinput"><code>yes</code></strong>, and a
3399                   DNS query requests recursion, then the server will attempt
3400                   to do
3401                   all the work required to answer the query. If recursion is
3402                   off
3403                   and the server does not already know the answer, it will
3404                   return a
3405                   referral response. The default is
3406                   <strong class="userinput"><code>yes</code></strong>.
3407                   Note that setting <span class="command"><strong>recursion no</strong></span> does not prevent
3408                   clients from getting data from the server's cache; it only
3409                   prevents new data from being cached as an effect of client
3410                   queries.
3411                   Caching may still occur as an effect the server's internal
3412                   operation, such as NOTIFY address lookups.
3413                 </p></dd>
3414 <dt><span class="term"><span class="command"><strong>request-nsid</strong></span></span></dt>
3415 <dd><p>
3416                   If <strong class="userinput"><code>yes</code></strong>, then an empty EDNS(0)
3417                   NSID (Name Server Identifier) option is sent with all
3418                   queries to authoritative name servers during iterative
3419                   resolution. If the authoritative server returns an NSID
3420                   option in its response, then its contents are logged in
3421                   the <span class="command"><strong>resolver</strong></span> category at level
3422                   <span class="command"><strong>info</strong></span>.
3423                   The default is <strong class="userinput"><code>no</code></strong>.
3424                 </p></dd>
3425 <dt><span class="term"><span class="command"><strong>rfc2308-type1</strong></span></span></dt>
3426 <dd>
3427 <p>
3428                   Setting this to <strong class="userinput"><code>yes</code></strong> will
3429                   cause the server to send NS records along with the SOA
3430                   record for negative
3431                   answers. The default is <strong class="userinput"><code>no</code></strong>.
3432                 </p>
3433 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3434 <h3 class="title">Note</h3>
3435 <p>
3436                     Not yet implemented in <acronym class="acronym">BIND</acronym>
3437                     9.
3438                   </p>
3439 </div>
3440 </dd>
3441 <dt><span class="term"><span class="command"><strong>use-id-pool</strong></span></span></dt>
3442 <dd><p>
3443                   <span class="emphasis"><em>This option is obsolete</em></span>.
3444                   <acronym class="acronym">BIND</acronym> 9 always allocates query
3445                   IDs from a pool.
3446                 </p></dd>
3447 <dt><span class="term"><span class="command"><strong>use-ixfr</strong></span></span></dt>
3448 <dd><p>
3449                   <span class="emphasis"><em>This option is obsolete</em></span>.
3450                   If you need to disable IXFR to a particular server or
3451                   servers, see
3452                   the information on the <span class="command"><strong>provide-ixfr</strong></span> option
3453                   in <a class="xref" href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and Usage">the section called &#8220;<span class="command"><strong>server</strong></span> Statement Definition and
3454             Usage&#8221;</a>.
3455                   See also
3456                   <a class="xref" href="Bv9ARM.ch04.html#incremental_zone_transfers" title="Incremental Zone Transfers (IXFR)">the section called &#8220;Incremental Zone Transfers (IXFR)&#8221;</a>.
3457                 </p></dd>
3458 <dt><span class="term"><span class="command"><strong>provide-ixfr</strong></span></span></dt>
3459 <dd><p>
3460                   See the description of
3461                   <span class="command"><strong>provide-ixfr</strong></span> in
3462                   <a class="xref" href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and Usage">the section called &#8220;<span class="command"><strong>server</strong></span> Statement Definition and
3463             Usage&#8221;</a>.
3464                 </p></dd>
3465 <dt><span class="term"><span class="command"><strong>request-ixfr</strong></span></span></dt>
3466 <dd><p>
3467                   See the description of
3468                   <span class="command"><strong>request-ixfr</strong></span> in
3469                   <a class="xref" href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and Usage">the section called &#8220;<span class="command"><strong>server</strong></span> Statement Definition and
3470             Usage&#8221;</a>.
3471                 </p></dd>
3472 <dt><span class="term"><span class="command"><strong>treat-cr-as-space</strong></span></span></dt>
3473 <dd><p>
3474                   This option was used in <acronym class="acronym">BIND</acronym>
3475                   8 to make
3476                   the server treat carriage return ("<span class="command"><strong>\r</strong></span>") characters the same way
3477                   as a space or tab character,
3478                   to facilitate loading of zone files on a UNIX system that
3479                   were generated
3480                   on an NT or DOS machine. In <acronym class="acronym">BIND</acronym> 9, both UNIX "<span class="command"><strong>\n</strong></span>"
3481                   and NT/DOS "<span class="command"><strong>\r\n</strong></span>" newlines
3482                   are always accepted,
3483                   and the option is ignored.
3484                 </p></dd>
3485 <dt>
3486 <span class="term"><span class="command"><strong>additional-from-auth</strong></span>, </span><span class="term"><span class="command"><strong>additional-from-cache</strong></span></span>
3487 </dt>
3488 <dd>
3489 <p>
3490                   These options control the behavior of an authoritative
3491                   server when
3492                   answering queries which have additional data, or when
3493                   following CNAME
3494                   and DNAME chains.
3495                 </p>
3496 <p>
3497                   When both of these options are set to <strong class="userinput"><code>yes</code></strong>
3498                   (the default) and a
3499                   query is being answered from authoritative data (a zone
3500                   configured into the server), the additional data section of
3501                   the
3502                   reply will be filled in using data from other authoritative
3503                   zones
3504                   and from the cache.  In some situations this is undesirable,
3505                   such
3506                   as when there is concern over the correctness of the cache,
3507                   or
3508                   in servers where slave zones may be added and modified by
3509                   untrusted third parties.  Also, avoiding
3510                   the search for this additional data will speed up server
3511                   operations
3512                   at the possible expense of additional queries to resolve
3513                   what would
3514                   otherwise be provided in the additional section.
3515                 </p>
3516 <p>
3517                   For example, if a query asks for an MX record for host <code class="literal">foo.example.com</code>,
3518                   and the record found is "<code class="literal">MX 10 mail.example.net</code>", normally the address
3519                   records (A and AAAA) for <code class="literal">mail.example.net</code> will be provided as well,
3520                   if known, even though they are not in the example.com zone.
3521                   Setting these options to <span class="command"><strong>no</strong></span>
3522                   disables this behavior and makes
3523                   the server only search for additional data in the zone it
3524                   answers from.
3525                 </p>
3526 <p>
3527                   These options are intended for use in authoritative-only
3528                   servers, or in authoritative-only views.  Attempts to set
3529                   them to <span class="command"><strong>no</strong></span> without also
3530                   specifying
3531                   <span class="command"><strong>recursion no</strong></span> will cause the
3532                   server to
3533                   ignore the options and log a warning message.
3534                 </p>
3535 <p>
3536                   Specifying <span class="command"><strong>additional-from-cache no</strong></span> actually
3537                   disables the use of the cache not only for additional data
3538                   lookups
3539                   but also when looking up the answer.  This is usually the
3540                   desired
3541                   behavior in an authoritative-only server where the
3542                   correctness of
3543                   the cached data is an issue.
3544                 </p>
3545 <p>
3546                   When a name server is non-recursively queried for a name
3547                   that is not
3548                   below the apex of any served zone, it normally answers with
3549                   an
3550                   "upwards referral" to the root servers or the servers of
3551                   some other
3552                   known parent of the query name.  Since the data in an
3553                   upwards referral
3554                   comes from the cache, the server will not be able to provide
3555                   upwards
3556                   referrals when <span class="command"><strong>additional-from-cache no</strong></span>
3557                   has been specified.  Instead, it will respond to such
3558                   queries
3559                   with REFUSED.  This should not cause any problems since
3560                   upwards referrals are not required for the resolution
3561                   process.
3562                 </p>
3563 </dd>
3564 <dt><span class="term"><span class="command"><strong>match-mapped-addresses</strong></span></span></dt>
3565 <dd>
3566 <p>
3567                   If <strong class="userinput"><code>yes</code></strong>, then an
3568                   IPv4-mapped IPv6 address will match any address match
3569                   list entries that match the corresponding IPv4 address.
3570                 </p>
3571 <p>
3572                   This option was introduced to work around a kernel quirk
3573                   in some operating systems that causes IPv4 TCP
3574                   connections, such as zone transfers, to be accepted on an
3575                   IPv6 socket using mapped addresses.  This caused address
3576                   match lists designed for IPv4 to fail to match.  However,
3577                   <span class="command"><strong>named</strong></span> now solves this problem
3578                   internally.  The use of this option is discouraged.
3579                 </p>
3580 </dd>
3581 <dt><span class="term"><span class="command"><strong>filter-aaaa-on-v4</strong></span></span></dt>
3582 <dd>
3583 <p>
3584                   This option is only available when
3585                   <acronym class="acronym">BIND</acronym> 9 is compiled with the
3586                   <strong class="userinput"><code>--enable-filter-aaaa</code></strong> option on the
3587                   "configure" command line.  It is intended to help the
3588                   transition from IPv4 to IPv6 by not giving IPv6 addresses
3589                   to DNS clients unless they have connections to the IPv6
3590                   Internet.  This is not recommended unless absolutely
3591                   necessary.  The default is <strong class="userinput"><code>no</code></strong>.
3592                   The <span class="command"><strong>filter-aaaa-on-v4</strong></span> option
3593                   may also be specified in <span class="command"><strong>view</strong></span> statements
3594                   to override the global <span class="command"><strong>filter-aaaa-on-v4</strong></span>
3595                   option.
3596                 </p>
3597 <p>
3598                   If <strong class="userinput"><code>yes</code></strong>,
3599                   the DNS client is at an IPv4 address, in <span class="command"><strong>filter-aaaa</strong></span>,
3600                   and if the response does not include DNSSEC signatures,
3601                   then all AAAA records are deleted from the response.
3602                   This filtering applies to all responses and not only
3603                   authoritative responses.
3604                 </p>
3605 <p>
3606                   If <strong class="userinput"><code>break-dnssec</code></strong>,
3607                   then AAAA records are deleted even when dnssec is enabled.
3608                   As suggested by the name, this makes the response not verify,
3609                   because the DNSSEC protocol is designed detect deletions.
3610                 </p>
3611 <p>
3612                   This mechanism can erroneously cause other servers to
3613                   not give AAAA records to their clients.
3614                   A recursing server with both IPv6 and IPv4 network connections
3615                   that queries an authoritative server using this mechanism
3616                   via IPv4 will be denied AAAA records even if its client is
3617                   using IPv6.
3618                 </p>
3619 <p>
3620                   This mechanism is applied to authoritative as well as
3621                   non-authoritative records.
3622                   A client using IPv4 that is not allowed recursion can
3623                   erroneously be given AAAA records because the server is not
3624                   allowed to check for A records.
3625                 </p>
3626 <p>
3627                   Some AAAA records are given to IPv4 clients in glue records.
3628                   IPv4 clients that are servers can then erroneously
3629                   answer requests for AAAA records received via IPv4.
3630                 </p>
3631 </dd>
3632 <dt><span class="term"><span class="command"><strong>ixfr-from-differences</strong></span></span></dt>
3633 <dd>
3634 <p>
3635                   When <strong class="userinput"><code>yes</code></strong> and the server loads a new
3636                   version of a master zone from its zone file or receives a
3637                   new version of a slave file via zone transfer, it will
3638                   compare the new version to the previous one and calculate
3639                   a set of differences.  The differences are then logged in
3640                   the zone's journal file such that the changes can be
3641                   transmitted to downstream slaves as an incremental zone
3642                   transfer.
3643                 </p>
3644 <p>
3645                   By allowing incremental zone transfers to be used for
3646                   non-dynamic zones, this option saves bandwidth at the
3647                   expense of increased CPU and memory consumption at the
3648                   master.
3649                   In particular, if the new version of a zone is completely
3650                   different from the previous one, the set of differences
3651                   will be of a size comparable to the combined size of the
3652                   old and new zone version, and the server will need to
3653                   temporarily allocate memory to hold this complete
3654                   difference set.
3655                 </p>
3656 <p><span class="command"><strong>ixfr-from-differences</strong></span>
3657                   also accepts <span class="command"><strong>master</strong></span> and
3658                   <span class="command"><strong>slave</strong></span> at the view and options
3659                   levels which causes
3660                   <span class="command"><strong>ixfr-from-differences</strong></span> to be enabled for
3661                   all <span class="command"><strong>master</strong></span> or
3662                   <span class="command"><strong>slave</strong></span> zones respectively.
3663                   It is off by default.
3664                 </p>
3665 </dd>
3666 <dt><span class="term"><span class="command"><strong>multi-master</strong></span></span></dt>
3667 <dd><p>
3668                   This should be set when you have multiple masters for a zone
3669                   and the
3670                   addresses refer to different machines.  If <strong class="userinput"><code>yes</code></strong>, <span class="command"><strong>named</strong></span> will
3671                   not log
3672                   when the serial number on the master is less than what <span class="command"><strong>named</strong></span>
3673                   currently
3674                   has.  The default is <strong class="userinput"><code>no</code></strong>.
3675                 </p></dd>
3676 <dt><span class="term"><span class="command"><strong>auto-dnssec</strong></span></span></dt>
3677 <dd>
3678 <p>
3679                   Zones configured for dynamic DNS may use this
3680                   option to allow varying levels of automatic DNSSEC key
3681                   management. There are three possible settings:
3682                 </p>
3683 <p>
3684                   <span class="command"><strong>auto-dnssec allow;</strong></span> permits
3685                   keys to be updated and the zone fully re-signed
3686                   whenever the user issues the command <span class="command"><strong>rndc sign
3687                   <em class="replaceable"><code>zonename</code></em></strong></span>.
3688                 </p>
3689 <p>
3690                   <span class="command"><strong>auto-dnssec maintain;</strong></span> includes the
3691                   above, but also automatically adjusts the zone's DNSSEC
3692                   keys on schedule, according to the keys' timing metadata
3693                   (see <a class="xref" href="man.dnssec-keygen.html" title="dnssec-keygen"><span class="refentrytitle"><span class="application">dnssec-keygen</span></span>(8)</a> and
3694                   <a class="xref" href="man.dnssec-settime.html" title="dnssec-settime"><span class="refentrytitle"><span class="application">dnssec-settime</span></span>(8)</a>).  The command
3695                   <span class="command"><strong>rndc sign
3696                   <em class="replaceable"><code>zonename</code></em></strong></span> causes
3697                   <span class="command"><strong>named</strong></span> to load keys from the key
3698                   repository and sign the zone with all keys that are
3699                   active.
3700                   <span class="command"><strong>rndc loadkeys
3701                   <em class="replaceable"><code>zonename</code></em></strong></span> causes
3702                   <span class="command"><strong>named</strong></span> to load keys from the key
3703                   repository and schedule key maintenance events to occur
3704                   in the future, but it does not sign the full zone
3705                   immediately.  Note: once keys have been loaded for a
3706                   zone the first time, the repository will be searched
3707                   for changes periodically, regardless of whether
3708                   <span class="command"><strong>rndc loadkeys</strong></span> is used.  The recheck
3709                   interval is defined by
3710                   <span class="command"><strong>dnssec-loadkeys-interval</strong></span>.)
3711                 </p>
3712 <p>
3713                   The default setting is <span class="command"><strong>auto-dnssec off</strong></span>.
3714                 </p>
3715 </dd>
3716 <dt><span class="term"><span class="command"><strong>dnssec-enable</strong></span></span></dt>
3717 <dd><p>
3718                   This indicates whether DNSSEC-related resource
3719                   records are to be returned by <span class="command"><strong>named</strong></span>.
3720                   If set to <strong class="userinput"><code>no</code></strong>,
3721                   <span class="command"><strong>named</strong></span> will not return DNSSEC-related
3722                   resource records unless specifically queried for.
3723                   The default is <strong class="userinput"><code>yes</code></strong>.
3724                 </p></dd>
3725 <dt><span class="term"><span class="command"><strong>dnssec-validation</strong></span></span></dt>
3726 <dd>
3727 <p>
3728                   Enable DNSSEC validation in <span class="command"><strong>named</strong></span>.
3729                   Note <span class="command"><strong>dnssec-enable</strong></span> also needs to be
3730                   set to <strong class="userinput"><code>yes</code></strong> to be effective.
3731                   If set to <strong class="userinput"><code>no</code></strong>, DNSSEC validation
3732                   is disabled.  If set to <strong class="userinput"><code>auto</code></strong>,
3733                   DNSSEC validation is enabled, and a default
3734                   trust-anchor for the DNS root zone is used.  If set to
3735                   <strong class="userinput"><code>yes</code></strong>, DNSSEC validation is enabled,
3736                   but a trust anchor must be manually configured using
3737                   a <span class="command"><strong>trusted-keys</strong></span> or
3738                   <span class="command"><strong>managed-keys</strong></span> statement.  The default
3739                   is <strong class="userinput"><code>yes</code></strong>.
3740                 </p>
3741 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3742 <h3 class="title">Note</h3>
3743 <p>
3744                     Whenever the resolver sends out queries to an
3745                     EDNS-compliant server, it always sets the DO bit
3746                     indicating it can support DNSSEC responses even if
3747                     <span class="command"><strong>dnssec-validation</strong></span> is off.
3748                   </p>
3749 </div>
3750 </dd>
3751 <dt><span class="term"><span class="command"><strong>dnssec-accept-expired</strong></span></span></dt>
3752 <dd><p>
3753                   Accept expired signatures when verifying DNSSEC signatures.
3754                   The default is <strong class="userinput"><code>no</code></strong>.
3755                   Setting this option to <strong class="userinput"><code>yes</code></strong>
3756                   leaves <span class="command"><strong>named</strong></span> vulnerable to
3757                   replay attacks.
3758                 </p></dd>
3759 <dt><span class="term"><span class="command"><strong>querylog</strong></span></span></dt>
3760 <dd><p>
3761                   Specify whether query logging should be started when <span class="command"><strong>named</strong></span>
3762                   starts.
3763                   If <span class="command"><strong>querylog</strong></span> is not specified,
3764                   then the query logging
3765                   is determined by the presence of the logging category <span class="command"><strong>queries</strong></span>.
3766                 </p></dd>
3767 <dt><span class="term"><span class="command"><strong>check-names</strong></span></span></dt>
3768 <dd>
3769 <p>
3770                   This option is used to restrict the character set and syntax
3771                   of
3772                   certain domain names in master files and/or DNS responses
3773                   received
3774                   from the network.  The default varies according to usage
3775                   area.  For
3776                   <span class="command"><strong>master</strong></span> zones the default is <span class="command"><strong>fail</strong></span>.
3777                   For <span class="command"><strong>slave</strong></span> zones the default
3778                   is <span class="command"><strong>warn</strong></span>.
3779                   For answers received from the network (<span class="command"><strong>response</strong></span>)
3780                   the default is <span class="command"><strong>ignore</strong></span>.
3781                 </p>
3782 <p>
3783                   The rules for legal hostnames and mail domains are derived
3784                   from RFC 952 and RFC 821 as modified by RFC 1123.
3785                 </p>
3786 <p><span class="command"><strong>check-names</strong></span>
3787                   applies to the owner names of A, AAAA and MX records.
3788                   It also applies to the domain names in the RDATA of NS, SOA,
3789                   MX, and SRV records.
3790                   It also applies to the RDATA of PTR records where the owner
3791                   name indicated that it is a reverse lookup of a hostname
3792                   (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, or IP6.INT).
3793                 </p>
3794 </dd>
3795 <dt><span class="term"><span class="command"><strong>check-dup-records</strong></span></span></dt>
3796 <dd><p>
3797                   Check master zones for records that are treated as different
3798                   by DNSSEC but are semantically equal in plain DNS.  The
3799                   default is to <span class="command"><strong>warn</strong></span>.  Other possible
3800                   values are <span class="command"><strong>fail</strong></span> and
3801                   <span class="command"><strong>ignore</strong></span>.
3802                 </p></dd>
3803 <dt><span class="term"><span class="command"><strong>check-mx</strong></span></span></dt>
3804 <dd><p>
3805                   Check whether the MX record appears to refer to a IP address.
3806                   The default is to <span class="command"><strong>warn</strong></span>.  Other possible
3807                   values are <span class="command"><strong>fail</strong></span> and
3808                   <span class="command"><strong>ignore</strong></span>.
3809                 </p></dd>
3810 <dt><span class="term"><span class="command"><strong>check-wildcard</strong></span></span></dt>
3811 <dd><p>
3812                   This option is used to check for non-terminal wildcards.
3813                   The use of non-terminal wildcards is almost always as a
3814                   result of a failure
3815                   to understand the wildcard matching algorithm (RFC 1034).
3816                   This option
3817                   affects master zones.  The default (<span class="command"><strong>yes</strong></span>) is to check
3818                   for non-terminal wildcards and issue a warning.
3819                 </p></dd>
3820 <dt><span class="term"><span class="command"><strong>check-integrity</strong></span></span></dt>
3821 <dd>
3822 <p>
3823                   Perform post load zone integrity checks on master
3824                   zones.  This checks that MX and SRV records refer
3825                   to address (A or AAAA) records and that glue
3826                   address records exist for delegated zones.  For
3827                   MX and SRV records only in-zone hostnames are
3828                   checked (for out-of-zone hostnames use
3829                   <span class="command"><strong>named-checkzone</strong></span>).
3830                   For NS records only names below top of zone are
3831                   checked (for out-of-zone names and glue consistency
3832                   checks use <span class="command"><strong>named-checkzone</strong></span>).
3833                   The default is <span class="command"><strong>yes</strong></span>.
3834                 </p>
3835 <p>
3836                   The use of the SPF record for publishing Sender
3837                   Policy Framework is deprecated as the migration
3838                   from using TXT records to SPF records was abandoned.
3839                   Enabling this option also checks that a TXT Sender
3840                   Policy Framework record exists (starts with "v=spf1")
3841                   if there is an SPF record. Warnings are emitted if the
3842                   TXT record does not exist and can be suppressed with
3843                   <span class="command"><strong>check-spf</strong></span>.
3844                 </p>
3845 </dd>
3846 <dt><span class="term"><span class="command"><strong>check-mx-cname</strong></span></span></dt>
3847 <dd><p>
3848                   If <span class="command"><strong>check-integrity</strong></span> is set then
3849                   fail, warn or ignore MX records that refer
3850                   to CNAMES.  The default is to <span class="command"><strong>warn</strong></span>.
3851                 </p></dd>
3852 <dt><span class="term"><span class="command"><strong>check-srv-cname</strong></span></span></dt>
3853 <dd><p>
3854                   If <span class="command"><strong>check-integrity</strong></span> is set then
3855                   fail, warn or ignore SRV records that refer
3856                   to CNAMES.  The default is to <span class="command"><strong>warn</strong></span>.
3857                 </p></dd>
3858 <dt><span class="term"><span class="command"><strong>check-sibling</strong></span></span></dt>
3859 <dd><p>
3860                   When performing integrity checks, also check that
3861                   sibling glue exists.  The default is <span class="command"><strong>yes</strong></span>.
3862                 </p></dd>
3863 <dt><span class="term"><span class="command"><strong>check-spf</strong></span></span></dt>
3864 <dd><p>
3865                   If <span class="command"><strong>check-integrity</strong></span> is set then
3866                   check that there is a TXT Sender Policy Framework
3867                   record present (starts with "v=spf1") if there is an
3868                   SPF record present. The default is
3869                   <span class="command"><strong>warn</strong></span>.
3870                 </p></dd>
3871 <dt><span class="term"><span class="command"><strong>zero-no-soa-ttl</strong></span></span></dt>
3872 <dd><p>
3873                   When returning authoritative negative responses to
3874                   SOA queries set the TTL of the SOA record returned in
3875                   the authority section to zero.
3876                   The default is <span class="command"><strong>yes</strong></span>.
3877                 </p></dd>
3878 <dt><span class="term"><span class="command"><strong>zero-no-soa-ttl-cache</strong></span></span></dt>
3879 <dd><p>
3880                   When caching a negative response to a SOA query
3881                   set the TTL to zero.
3882                   The default is <span class="command"><strong>no</strong></span>.
3883                 </p></dd>
3884 <dt><span class="term"><span class="command"><strong>update-check-ksk</strong></span></span></dt>
3885 <dd>
3886 <p>
3887                   When set to the default value of <code class="literal">yes</code>,
3888                   check the KSK bit in each key to determine how the key
3889                   should be used when generating RRSIGs for a secure zone.
3890                 </p>
3891 <p>
3892                   Ordinarily, zone-signing keys (that is, keys without the
3893                   KSK bit set) are used to sign the entire zone, while
3894                   key-signing keys (keys with the KSK bit set) are only
3895                   used to sign the DNSKEY RRset at the zone apex.
3896                   However, if this option is set to <code class="literal">no</code>,
3897                   then the KSK bit is ignored; KSKs are treated as if they
3898                   were ZSKs and are used to sign the entire zone.  This is
3899                   similar to the <span class="command"><strong>dnssec-signzone -z</strong></span>
3900                   command line option.
3901                 </p>
3902 <p>
3903                   When this option is set to <code class="literal">yes</code>, there
3904                   must be at least two active keys for every algorithm
3905                   represented in the DNSKEY RRset: at least one KSK and one
3906                   ZSK per algorithm.  If there is any algorithm for which
3907                   this requirement is not met, this option will be ignored
3908                   for that algorithm.
3909                 </p>
3910 </dd>
3911 <dt><span class="term"><span class="command"><strong>dnssec-dnskey-kskonly</strong></span></span></dt>
3912 <dd>
3913 <p>
3914                   When this option and <span class="command"><strong>update-check-ksk</strong></span>
3915                   are both set to <code class="literal">yes</code>, only key-signing
3916                   keys (that is, keys with the KSK bit set) will be used
3917                   to sign the DNSKEY RRset at the zone apex.  Zone-signing
3918                   keys (keys without the KSK bit set) will be used to sign
3919                   the remainder of the zone, but not the DNSKEY RRset.
3920                   This is similar to the
3921                   <span class="command"><strong>dnssec-signzone -x</strong></span> command line option.
3922                 </p>
3923 <p>
3924                   The default is <span class="command"><strong>no</strong></span>.  If
3925                   <span class="command"><strong>update-check-ksk</strong></span> is set to
3926                   <code class="literal">no</code>, this option is ignored.
3927                 </p>
3928 </dd>
3929 <dt><span class="term"><span class="command"><strong>try-tcp-refresh</strong></span></span></dt>
3930 <dd><p>
3931                   Try to refresh the zone using TCP if UDP queries fail.
3932                   For BIND 8 compatibility, the default is
3933                   <span class="command"><strong>yes</strong></span>.
3934                 </p></dd>
3935 <dt><span class="term"><span class="command"><strong>dnssec-secure-to-insecure</strong></span></span></dt>
3936 <dd>
3937 <p>
3938                   Allow a dynamic zone to transition from secure to
3939                   insecure (i.e., signed to unsigned) by deleting all
3940                   of the DNSKEY records.  The default is <span class="command"><strong>no</strong></span>.
3941                   If set to <span class="command"><strong>yes</strong></span>, and if the DNSKEY RRset
3942                   at the zone apex is deleted, all RRSIG and NSEC records
3943                   will be removed from the zone as well.
3944                 </p>
3945 <p>
3946                   If the zone uses NSEC3, then it is also necessary to
3947                   delete the NSEC3PARAM RRset from the zone apex; this will
3948                   cause the removal of all corresponding NSEC3 records.
3949                   (It is expected that this requirement will be eliminated
3950                   in a future release.)
3951                 </p>
3952 <p>
3953                   Note that if a zone has been configured with
3954                   <span class="command"><strong>auto-dnssec maintain</strong></span> and the
3955                   private keys remain accessible in the key repository,
3956                   then the zone will be automatically signed again the
3957                   next time <span class="command"><strong>named</strong></span> is started.
3958                 </p>
3959 </dd>
3960 </dl></div>
3961 </div>
3962 <div class="section">
3963 <div class="titlepage"><div><div><h4 class="title">
3964 <a name="forwarding"></a>Forwarding</h4></div></div></div>
3965 <p>
3966             The forwarding facility can be used to create a large site-wide
3967             cache on a few servers, reducing traffic over links to external
3968             name servers. It can also be used to allow queries by servers that
3969             do not have direct access to the Internet, but wish to look up
3970             exterior
3971             names anyway. Forwarding occurs only on those queries for which
3972             the server is not authoritative and does not have the answer in
3973             its cache.
3974           </p>
3975 <div class="variablelist"><dl class="variablelist">
3976 <dt><span class="term"><span class="command"><strong>forward</strong></span></span></dt>
3977 <dd><p>
3978                   This option is only meaningful if the
3979                   forwarders list is not empty. A value of <code class="varname">first</code>,
3980                   the default, causes the server to query the forwarders
3981                   first &#8212; and
3982                   if that doesn't answer the question, the server will then
3983                   look for
3984                   the answer itself. If <code class="varname">only</code> is
3985                   specified, the
3986                   server will only query the forwarders.
3987                 </p></dd>
3988 <dt><span class="term"><span class="command"><strong>forwarders</strong></span></span></dt>
3989 <dd><p>
3990                   Specifies the IP addresses to be used
3991                   for forwarding. The default is the empty list (no
3992                   forwarding).
3993                 </p></dd>
3994 </dl></div>
3995 <p>
3996             Forwarding can also be configured on a per-domain basis, allowing
3997             for the global forwarding options to be overridden in a variety
3998             of ways. You can set particular domains to use different
3999             forwarders,
4000             or have a different <span class="command"><strong>forward only/first</strong></span> behavior,
4001             or not forward at all, see <a class="xref" href="Bv9ARM.ch06.html#zone_statement_grammar" title="zone Statement Grammar">the section called &#8220;<span class="command"><strong>zone</strong></span>
4002             Statement Grammar&#8221;</a>.
4003           </p>
4004 </div>
4005 <div class="section">
4006 <div class="titlepage"><div><div><h4 class="title">
4007 <a name="dual_stack"></a>Dual-stack Servers</h4></div></div></div>
4008 <p>
4009             Dual-stack servers are used as servers of last resort to work
4010             around
4011             problems in reachability due the lack of support for either IPv4
4012             or IPv6
4013             on the host machine.
4014           </p>
4015 <div class="variablelist"><dl class="variablelist">
4016 <dt><span class="term"><span class="command"><strong>dual-stack-servers</strong></span></span></dt>
4017 <dd><p>
4018                   Specifies host names or addresses of machines with access to
4019                   both IPv4 and IPv6 transports. If a hostname is used, the
4020                   server must be able
4021                   to resolve the name using only the transport it has.  If the
4022                   machine is dual
4023                   stacked, then the <span class="command"><strong>dual-stack-servers</strong></span> have no effect unless
4024                   access to a transport has been disabled on the command line
4025                   (e.g. <span class="command"><strong>named -4</strong></span>).
4026                 </p></dd>
4027 </dl></div>
4028 </div>
4029 <div class="section">
4030 <div class="titlepage"><div><div><h4 class="title">
4031 <a name="access_control"></a>Access Control</h4></div></div></div>
4032 <p>
4033             Access to the server can be restricted based on the IP address
4034             of the requesting system. See <a class="xref" href="Bv9ARM.ch06.html#address_match_lists" title="Address Match Lists">the section called &#8220;Address Match Lists&#8221;</a> for
4035             details on how to specify IP address lists.
4036           </p>
4037 <div class="variablelist"><dl class="variablelist">
4038 <dt><span class="term"><span class="command"><strong>allow-notify</strong></span></span></dt>
4039 <dd><p>
4040                   Specifies which hosts are allowed to
4041                   notify this server, a slave, of zone changes in addition
4042                   to the zone masters.
4043                   <span class="command"><strong>allow-notify</strong></span> may also be
4044                   specified in the
4045                   <span class="command"><strong>zone</strong></span> statement, in which case
4046                   it overrides the
4047                   <span class="command"><strong>options allow-notify</strong></span>
4048                   statement.  It is only meaningful
4049                   for a slave zone.  If not specified, the default is to
4050                   process notify messages
4051                   only from a zone's master.
4052                 </p></dd>
4053 <dt><span class="term"><span class="command"><strong>allow-query</strong></span></span></dt>
4054 <dd>
4055 <p>
4056                   Specifies which hosts are allowed to ask ordinary
4057                   DNS questions. <span class="command"><strong>allow-query</strong></span> may
4058                   also be specified in the <span class="command"><strong>zone</strong></span>
4059                   statement, in which case it overrides the
4060                   <span class="command"><strong>options allow-query</strong></span> statement.
4061                   If not specified, the default is to allow queries
4062                   from all hosts.
4063                 </p>
4064 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4065 <h3 class="title">Note</h3>
4066 <p>
4067                     <span class="command"><strong>allow-query-cache</strong></span> is now
4068                     used to specify access to the cache.
4069                   </p>
4070 </div>
4071 </dd>
4072 <dt><span class="term"><span class="command"><strong>allow-query-on</strong></span></span></dt>
4073 <dd>
4074 <p>
4075                   Specifies which local addresses can accept ordinary
4076                   DNS questions. This makes it possible, for instance,
4077                   to allow queries on internal-facing interfaces but
4078                   disallow them on external-facing ones, without
4079                   necessarily knowing the internal network's addresses.
4080                 </p>
4081 <p>
4082                   Note that <span class="command"><strong>allow-query-on</strong></span> is only
4083                   checked for queries that are permitted by
4084                   <span class="command"><strong>allow-query</strong></span>.  A query must be
4085                   allowed by both ACLs, or it will be refused.
4086                 </p>
4087 <p>
4088                   <span class="command"><strong>allow-query-on</strong></span> may
4089                   also be specified in the <span class="command"><strong>zone</strong></span>
4090                   statement, in which case it overrides the
4091                   <span class="command"><strong>options allow-query-on</strong></span> statement.
4092                 </p>
4093 <p>
4094                   If not specified, the default is to allow queries
4095                   on all addresses.
4096                 </p>
4097 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4098 <h3 class="title">Note</h3>
4099 <p>
4100                     <span class="command"><strong>allow-query-cache</strong></span> is
4101                     used to specify access to the cache.
4102                   </p>
4103 </div>
4104 </dd>
4105 <dt><span class="term"><span class="command"><strong>allow-query-cache</strong></span></span></dt>
4106 <dd><p>
4107                   Specifies which hosts are allowed to get answers
4108                   from the cache.  If <span class="command"><strong>allow-query-cache</strong></span>
4109                   is not set then <span class="command"><strong>allow-recursion</strong></span>
4110                   is used if set, otherwise <span class="command"><strong>allow-query</strong></span>
4111                   is used if set unless <span class="command"><strong>recursion no;</strong></span> is
4112                   set in which case <span class="command"><strong>none;</strong></span> is used,
4113                   otherwise the default (<span class="command"><strong>localnets;</strong></span>
4114                   <span class="command"><strong>localhost;</strong></span>) is used.
4115                 </p></dd>
4116 <dt><span class="term"><span class="command"><strong>allow-query-cache-on</strong></span></span></dt>
4117 <dd><p>
4118                   Specifies which local addresses can give answers
4119                   from the cache.  If not specified, the default is
4120                   to allow cache queries on any address,
4121                   <span class="command"><strong>localnets</strong></span> and
4122                   <span class="command"><strong>localhost</strong></span>.
4123                 </p></dd>
4124 <dt><span class="term"><span class="command"><strong>allow-recursion</strong></span></span></dt>
4125 <dd><p>
4126                   Specifies which hosts are allowed to make recursive
4127                   queries through this server. If
4128                   <span class="command"><strong>allow-recursion</strong></span> is not set
4129                   then <span class="command"><strong>allow-query-cache</strong></span> is
4130                   used if set, otherwise <span class="command"><strong>allow-query</strong></span>
4131                   is used if set, otherwise the default
4132                   (<span class="command"><strong>localnets;</strong></span>
4133                   <span class="command"><strong>localhost;</strong></span>) is used.
4134                 </p></dd>
4135 <dt><span class="term"><span class="command"><strong>allow-recursion-on</strong></span></span></dt>
4136 <dd><p>
4137                   Specifies which local addresses can accept recursive
4138                   queries.  If not specified, the default is to allow
4139                   recursive queries on all addresses.
4140                 </p></dd>
4141 <dt><span class="term"><span class="command"><strong>allow-update</strong></span></span></dt>
4142 <dd><p>
4143                   Specifies which hosts are allowed to
4144                   submit Dynamic DNS updates for master zones. The default is
4145                   to deny
4146                   updates from all hosts.  Note that allowing updates based
4147                   on the requestor's IP address is insecure; see
4148                   <a class="xref" href="Bv9ARM.ch07.html#dynamic_update_security" title="Dynamic Update Security">the section called &#8220;Dynamic Update Security&#8221;</a> for details.
4149                 </p></dd>
4150 <dt><span class="term"><span class="command"><strong>allow-update-forwarding</strong></span></span></dt>
4151 <dd>
4152 <p>
4153                   Specifies which hosts are allowed to
4154                   submit Dynamic DNS updates to slave zones to be forwarded to
4155                   the
4156                   master.  The default is <strong class="userinput"><code>{ none; }</code></strong>,
4157                   which
4158                   means that no update forwarding will be performed.  To
4159                   enable
4160                   update forwarding, specify
4161                   <strong class="userinput"><code>allow-update-forwarding { any; };</code></strong>.
4162                   Specifying values other than <strong class="userinput"><code>{ none; }</code></strong> or
4163                   <strong class="userinput"><code>{ any; }</code></strong> is usually
4164                   counterproductive, since
4165                   the responsibility for update access control should rest
4166                   with the
4167                   master server, not the slaves.
4168                 </p>
4169 <p>
4170                   Note that enabling the update forwarding feature on a slave
4171                   server
4172                   may expose master servers relying on insecure IP address
4173                   based
4174                   access control to attacks; see <a class="xref" href="Bv9ARM.ch07.html#dynamic_update_security" title="Dynamic Update Security">the section called &#8220;Dynamic Update Security&#8221;</a>
4175                   for more details.
4176                 </p>
4177 </dd>
4178 <dt><span class="term"><span class="command"><strong>allow-v6-synthesis</strong></span></span></dt>
4179 <dd><p>
4180                   This option was introduced for the smooth transition from
4181                   AAAA
4182                   to A6 and from "nibble labels" to binary labels.
4183                   However, since both A6 and binary labels were then
4184                   deprecated,
4185                   this option was also deprecated.
4186                   It is now ignored with some warning messages.
4187                 </p></dd>
4188 <dt><span class="term"><span class="command"><strong>allow-transfer</strong></span></span></dt>
4189 <dd><p>
4190                   Specifies which hosts are allowed to
4191                   receive zone transfers from the server. <span class="command"><strong>allow-transfer</strong></span> may
4192                   also be specified in the <span class="command"><strong>zone</strong></span>
4193                   statement, in which
4194                   case it overrides the <span class="command"><strong>options allow-transfer</strong></span> statement.
4195                   If not specified, the default is to allow transfers to all
4196                   hosts.
4197                 </p></dd>
4198 <dt><span class="term"><span class="command"><strong>blackhole</strong></span></span></dt>
4199 <dd><p>
4200                   Specifies a list of addresses that the
4201                   server will not accept queries from or use to resolve a
4202                   query. Queries
4203                   from these addresses will not be responded to. The default
4204                   is <strong class="userinput"><code>none</code></strong>.
4205                 </p></dd>
4206 <dt><span class="term"><span class="command"><strong>filter-aaaa</strong></span></span></dt>
4207 <dd><p>
4208                   Specifies a list of addresses to which
4209                   <span class="command"><strong>filter-aaaa-on-v4</strong></span>
4210                   is applies.  The default is <strong class="userinput"><code>any</code></strong>.
4211                 </p></dd>
4212 <dt><span class="term"><span class="command"><strong>no-case-compress</strong></span></span></dt>
4213 <dd>
4214 <p>
4215                   Specifies a list of addresses which require responses
4216                   to use case-insensitive compression.  This ACL can be
4217                   used when <span class="command"><strong>named</strong></span> needs to work with
4218                   clients that do not comply with the requirement in RFC
4219                   1034 to use case-insensitive name comparisons when
4220                   checking for matching domain names.
4221                 </p>
4222 <p>
4223                   If left undefined, the ACL defaults to
4224                   <span class="command"><strong>none</strong></span>: case-insensitive compression
4225                   will be used for all clients.  If the ACL is defined and
4226                   matches a client, then case will be ignored when
4227                   compressing domain names in DNS responses sent to that
4228                   client.
4229                 </p>
4230 <p>
4231                   This can result in slightly smaller responses: if
4232                   a response contains the names "example.com" and
4233                   "example.COM", case-insensitive compression would treat
4234                   the second one as a duplicate.  It also ensures
4235                   that the case of the query name exactly matches the
4236                   case of the owner names of returned records, rather
4237                   than matching the case of the records entered in
4238                   the zone file.  This allows responses to exactly
4239                   match the query, which is required by some clients
4240                   due to incorrect use of case-sensitive comparisons.
4241                 </p>
4242 <p>
4243                   Case-insensitive compression is <span class="emphasis"><em>always</em></span>
4244                   used in AXFR and IXFR responses, regardless of whether
4245                   the client matches this ACL.
4246                 </p>
4247 <p>
4248                   There are circumstances in which <span class="command"><strong>named</strong></span>
4249                   will not preserve the case of owner names of records:
4250                   if a zone file defines records of different types with
4251                   the same name, but the capitalization of the name is
4252                   different (e.g., "www.example.com/A" and
4253                   "WWW.EXAMPLE.COM/AAAA"), then all responses for that
4254                   name will use the <span class="emphasis"><em>first</em></span> version
4255                   of the name that was used in the zone file.  This
4256                   limitation may be addressed in a future release.  However,
4257                   domain names specified in the rdata of resource records
4258                   (i.e., records of type NS, MX, CNAME, etc) will always
4259                   have their case preserved unless the client matches this
4260                   ACL.
4261                 </p>
4262 </dd>
4263 <dt><span class="term"><span class="command"><strong>resolver-query-timeout</strong></span></span></dt>
4264 <dd><p>
4265                   The amount of time the resolver will spend attempting
4266                   to resolve a recursive query before failing.  The default
4267                   and minimum is <code class="literal">10</code> and the maximum is
4268                   <code class="literal">30</code>.  Setting it to <code class="literal">0</code>
4269                   will result in the default being used.
4270                 </p></dd>
4271 </dl></div>
4272 </div>
4273 <div class="section">
4274 <div class="titlepage"><div><div><h4 class="title">
4275 <a name="interfaces"></a>Interfaces</h4></div></div></div>
4276 <p>
4277             The interfaces and ports that the server will answer queries
4278             from may be specified using the <span class="command"><strong>listen-on</strong></span> option. <span class="command"><strong>listen-on</strong></span> takes
4279             an optional port and an <code class="varname">address_match_list</code>
4280             of IPv4 addresses.  (IPv6 addresses are ignored, with a
4281             logged warning.)
4282             The server will listen on all interfaces allowed by the address
4283             match list. If a port is not specified, port 53 will be used.
4284           </p>
4285 <p>
4286             Multiple <span class="command"><strong>listen-on</strong></span> statements are
4287             allowed.
4288             For example,
4289           </p>
4290 <pre class="programlisting">listen-on { 5.6.7.8; };
4291 listen-on port 1234 { !1.2.3.4; 1.2/16; };
4292 </pre>
4293 <p>
4294             will enable the name server on port 53 for the IP address
4295             5.6.7.8, and on port 1234 of an address on the machine in net
4296             1.2 that is not 1.2.3.4.
4297           </p>
4298 <p>
4299             If no <span class="command"><strong>listen-on</strong></span> is specified, the
4300             server will listen on port 53 on all IPv4 interfaces.
4301           </p>
4302 <p>
4303             The <span class="command"><strong>listen-on-v6</strong></span> option is used to
4304             specify the interfaces and the ports on which the server will
4305             listen
4306             for incoming queries sent using IPv6.
4307           </p>
4308 <p>
4309             When </p>
4310 <pre class="programlisting">{ any; }</pre>
4311 <p> is
4312             specified
4313             as the <code class="varname">address_match_list</code> for the
4314             <span class="command"><strong>listen-on-v6</strong></span> option,
4315             the server does not bind a separate socket to each IPv6 interface
4316             address as it does for IPv4 if the operating system has enough API
4317             support for IPv6 (specifically if it conforms to RFC 3493 and RFC
4318             3542).
4319             Instead, it listens on the IPv6 wildcard address.
4320             If the system only has incomplete API support for IPv6, however,
4321             the behavior is the same as that for IPv4.
4322           </p>
4323 <p>
4324             A list of particular IPv6 addresses can also be specified, in
4325             which case
4326             the server listens on a separate socket for each specified
4327             address,
4328             regardless of whether the desired API is supported by the system.
4329             IPv4 addresses specified in <span class="command"><strong>listen-on-v6</strong></span>
4330             will be ignored, with a logged warning.
4331           </p>
4332 <p>
4333             Multiple <span class="command"><strong>listen-on-v6</strong></span> options can
4334             be used.
4335             For example,
4336           </p>
4337 <pre class="programlisting">listen-on-v6 { any; };
4338 listen-on-v6 port 1234 { !2001:db8::/32; any; };
4339 </pre>
4340 <p>
4341             will enable the name server on port 53 for any IPv6 addresses
4342             (with a single wildcard socket),
4343             and on port 1234 of IPv6 addresses that is not in the prefix
4344             2001:db8::/32 (with separate sockets for each matched address.)
4345           </p>
4346 <p>
4347             To make the server not listen on any IPv6 address, use
4348           </p>
4349 <pre class="programlisting">listen-on-v6 { none; };
4350 </pre>
4351 <p>
4352             If no <span class="command"><strong>listen-on-v6</strong></span> option is
4353             specified, the server will not listen on any IPv6 address
4354             unless <span class="command"><strong>-6</strong></span> is specified when <span class="command"><strong>named</strong></span> is
4355             invoked.  If <span class="command"><strong>-6</strong></span> is specified then
4356             <span class="command"><strong>named</strong></span> will listen on port 53 on all IPv6 interfaces by default.
4357           </p>
4358 </div>
4359 <div class="section">
4360 <div class="titlepage"><div><div><h4 class="title">
4361 <a name="query_address"></a>Query Address</h4></div></div></div>
4362 <p>
4363             If the server doesn't know the answer to a question, it will
4364             query other name servers. <span class="command"><strong>query-source</strong></span> specifies
4365             the address and port used for such queries. For queries sent over
4366             IPv6, there is a separate <span class="command"><strong>query-source-v6</strong></span> option.
4367             If <span class="command"><strong>address</strong></span> is <span class="command"><strong>*</strong></span> (asterisk) or is omitted,
4368             a wildcard IP address (<span class="command"><strong>INADDR_ANY</strong></span>)
4369             will be used.
4370           </p>
4371 <p>
4372             If <span class="command"><strong>port</strong></span> is <span class="command"><strong>*</strong></span> or is omitted,
4373             a random port number from a pre-configured
4374             range is picked up and will be used for each query.
4375             The port range(s) is that specified in
4376             the <span class="command"><strong>use-v4-udp-ports</strong></span> (for IPv4)
4377             and <span class="command"><strong>use-v6-udp-ports</strong></span> (for IPv6)
4378             options, excluding the ranges specified in
4379             the <span class="command"><strong>avoid-v4-udp-ports</strong></span>
4380             and <span class="command"><strong>avoid-v6-udp-ports</strong></span> options, respectively.
4381           </p>
4382 <p>
4383             The defaults of the <span class="command"><strong>query-source</strong></span> and
4384             <span class="command"><strong>query-source-v6</strong></span> options
4385             are:
4386           </p>
4387 <pre class="programlisting">query-source address * port *;
4388 query-source-v6 address * port *;
4389 </pre>
4390 <p>
4391             If <span class="command"><strong>use-v4-udp-ports</strong></span> or
4392             <span class="command"><strong>use-v6-udp-ports</strong></span> is unspecified,
4393             <span class="command"><strong>named</strong></span> will check if the operating
4394             system provides a programming interface to retrieve the
4395             system's default range for ephemeral ports.
4396             If such an interface is available,
4397             <span class="command"><strong>named</strong></span> will use the corresponding system
4398             default range; otherwise, it will use its own defaults:
4399          </p>
4400 <pre class="programlisting">use-v4-udp-ports { range 1024 65535; };
4401 use-v6-udp-ports { range 1024 65535; };
4402 </pre>
4403 <p>
4404             Note: make sure the ranges be sufficiently large for
4405             security.  A desirable size depends on various parameters,
4406             but we generally recommend it contain at least 16384 ports
4407             (14 bits of entropy).
4408             Note also that the system's default range when used may be
4409             too small for this purpose, and that the range may even be
4410             changed while <span class="command"><strong>named</strong></span> is running; the new
4411             range will automatically be applied when <span class="command"><strong>named</strong></span>
4412             is reloaded.
4413             It is encouraged to
4414             configure <span class="command"><strong>use-v4-udp-ports</strong></span> and
4415             <span class="command"><strong>use-v6-udp-ports</strong></span> explicitly so that the
4416             ranges are sufficiently large and are reasonably
4417             independent from the ranges used by other applications.
4418           </p>
4419 <p>
4420             Note: the operational configuration
4421             where <span class="command"><strong>named</strong></span> runs may prohibit the use
4422             of some ports.  For example, UNIX systems will not allow
4423             <span class="command"><strong>named</strong></span> running without a root privilege
4424             to use ports less than 1024.
4425             If such ports are included in the specified (or detected)
4426             set of query ports, the corresponding query attempts will
4427             fail, resulting in resolution failures or delay.
4428             It is therefore important to configure the set of ports
4429             that can be safely used in the expected operational environment.
4430           </p>
4431 <p>
4432             The defaults of the <span class="command"><strong>avoid-v4-udp-ports</strong></span> and
4433             <span class="command"><strong>avoid-v6-udp-ports</strong></span> options
4434             are:
4435           </p>
4436 <pre class="programlisting">avoid-v4-udp-ports {};
4437 avoid-v6-udp-ports {};
4438 </pre>
4439 <p>
4440             Note: BIND 9.5.0 introduced
4441             the <span class="command"><strong>use-queryport-pool</strong></span>
4442             option to support a pool of such random ports, but this
4443             option is now obsolete because reusing the same ports in
4444             the pool may not be sufficiently secure.
4445             For the same reason, it is generally strongly discouraged to
4446             specify a particular port for the
4447             <span class="command"><strong>query-source</strong></span> or
4448             <span class="command"><strong>query-source-v6</strong></span> options;
4449             it implicitly disables the use of randomized port numbers.
4450           </p>
4451 <div class="variablelist"><dl class="variablelist">
4452 <dt><span class="term"><span class="command"><strong>use-queryport-pool</strong></span></span></dt>
4453 <dd><p>
4454                   This option is obsolete.
4455                 </p></dd>
4456 <dt><span class="term"><span class="command"><strong>queryport-pool-ports</strong></span></span></dt>
4457 <dd><p>
4458                   This option is obsolete.
4459                 </p></dd>
4460 <dt><span class="term"><span class="command"><strong>queryport-pool-updateinterval</strong></span></span></dt>
4461 <dd><p>
4462                   This option is obsolete.
4463                 </p></dd>
4464 </dl></div>
4465 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4466 <h3 class="title">Note</h3>
4467 <p>
4468               The address specified in the <span class="command"><strong>query-source</strong></span> option
4469               is used for both UDP and TCP queries, but the port applies only
4470               to UDP queries.  TCP queries always use a random
4471               unprivileged port.
4472             </p>
4473 </div>
4474 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4475 <h3 class="title">Note</h3>
4476 <p>
4477               Solaris 2.5.1 and earlier does not support setting the source
4478               address for TCP sockets.
4479             </p>
4480 </div>
4481 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4482 <h3 class="title">Note</h3>
4483 <p>
4484               See also <span class="command"><strong>transfer-source</strong></span> and
4485               <span class="command"><strong>notify-source</strong></span>.
4486             </p>
4487 </div>
4488 </div>
4489 <div class="section">
4490 <div class="titlepage"><div><div><h4 class="title">
4491 <a name="zone_transfers"></a>Zone Transfers</h4></div></div></div>
4492 <p>
4493             <acronym class="acronym">BIND</acronym> has mechanisms in place to
4494             facilitate zone transfers
4495             and set limits on the amount of load that transfers place on the
4496             system. The following options apply to zone transfers.
4497           </p>
4498 <div class="variablelist"><dl class="variablelist">
4499 <dt><span class="term"><span class="command"><strong>also-notify</strong></span></span></dt>
4500 <dd>
4501 <p>
4502                   Defines a global list of IP addresses of name servers
4503                   that are also sent NOTIFY messages whenever a fresh copy of
4504                   the
4505                   zone is loaded, in addition to the servers listed in the
4506                   zone's NS records.
4507                   This helps to ensure that copies of the zones will
4508                   quickly converge on stealth servers.
4509                   Optionally, a port may be specified with each
4510                   <span class="command"><strong>also-notify</strong></span> address to send
4511                   the notify messages to a port other than the
4512                   default of 53.
4513                   An optional TSIG key can also be specified with each
4514                   address to cause the notify messages to be signed; this
4515                   can be useful when sending notifies to multiple views.
4516                   In place of explicit addresses, one or more named
4517                   <span class="command"><strong>masters</strong></span> lists can be used.
4518                 </p>
4519 <p>
4520                   If an <span class="command"><strong>also-notify</strong></span> list
4521                   is given in a <span class="command"><strong>zone</strong></span> statement,
4522                   it will override
4523                   the <span class="command"><strong>options also-notify</strong></span>
4524                   statement. When a <span class="command"><strong>zone notify</strong></span>
4525                   statement
4526                   is set to <span class="command"><strong>no</strong></span>, the IP
4527                   addresses in the global <span class="command"><strong>also-notify</strong></span> list will
4528                   not be sent NOTIFY messages for that zone. The default is
4529                   the empty
4530                   list (no global notification list).
4531                 </p>
4532 </dd>
4533 <dt><span class="term"><span class="command"><strong>max-transfer-time-in</strong></span></span></dt>
4534 <dd><p>
4535                   Inbound zone transfers running longer than
4536                   this many minutes will be terminated. The default is 120
4537                   minutes
4538                   (2 hours).  The maximum value is 28 days (40320 minutes).
4539                 </p></dd>
4540 <dt><span class="term"><span class="command"><strong>max-transfer-idle-in</strong></span></span></dt>
4541 <dd><p>
4542                   Inbound zone transfers making no progress
4543                   in this many minutes will be terminated. The default is 60
4544                   minutes
4545                   (1 hour).  The maximum value is 28 days (40320 minutes).
4546                 </p></dd>
4547 <dt><span class="term"><span class="command"><strong>max-transfer-time-out</strong></span></span></dt>
4548 <dd><p>
4549                   Outbound zone transfers running longer than
4550                   this many minutes will be terminated. The default is 120
4551                   minutes
4552                   (2 hours).  The maximum value is 28 days (40320 minutes).
4553                 </p></dd>
4554 <dt><span class="term"><span class="command"><strong>max-transfer-idle-out</strong></span></span></dt>
4555 <dd><p>
4556                   Outbound zone transfers making no progress
4557                   in this many minutes will be terminated.  The default is 60
4558                   minutes (1
4559                   hour).  The maximum value is 28 days (40320 minutes).
4560                 </p></dd>
4561 <dt><span class="term"><span class="command"><strong>serial-query-rate</strong></span></span></dt>
4562 <dd>
4563 <p>
4564                   Slave servers will periodically query master
4565                   servers to find out if zone serial numbers have
4566                   changed. Each such query uses a minute amount of
4567                   the slave server's network bandwidth.  To limit
4568                   the amount of bandwidth used, BIND 9 limits the
4569                   rate at which queries are sent.  The value of the
4570                   <span class="command"><strong>serial-query-rate</strong></span> option, an
4571                   integer, is the maximum number of queries sent
4572                   per second.  The default is 20 per second.
4573                   The lowest possible rate is one per second; when set
4574                   to zero, it will be silently raised to one.
4575                 </p>
4576 <p>
4577                   In addition to controlling the rate SOA refresh
4578                   queries are issued at,
4579                   <span class="command"><strong>serial-query-rate</strong></span> also controls
4580                   the rate at which NOTIFY messages are sent from
4581                   both master and slave zones.
4582                 </p>
4583 </dd>
4584 <dt><span class="term"><span class="command"><strong>serial-queries</strong></span></span></dt>
4585 <dd><p>
4586                   In BIND 8, the <span class="command"><strong>serial-queries</strong></span>
4587                   option
4588                   set the maximum number of concurrent serial number queries
4589                   allowed to be outstanding at any given time.
4590                   BIND 9 does not limit the number of outstanding
4591                   serial queries and ignores the <span class="command"><strong>serial-queries</strong></span> option.
4592                   Instead, it limits the rate at which the queries are sent
4593                   as defined using the <span class="command"><strong>serial-query-rate</strong></span> option.
4594                 </p></dd>
4595 <dt><span class="term"><span class="command"><strong>transfer-format</strong></span></span></dt>
4596 <dd><p>
4597                   Zone transfers can be sent using two different formats,
4598                   <span class="command"><strong>one-answer</strong></span> and
4599                   <span class="command"><strong>many-answers</strong></span>.
4600                   The <span class="command"><strong>transfer-format</strong></span> option is used
4601                   on the master server to determine which format it sends.
4602                   <span class="command"><strong>one-answer</strong></span> uses one DNS message per
4603                   resource record transferred.
4604                   <span class="command"><strong>many-answers</strong></span> packs as many resource
4605                   records as possible into a message.
4606                   <span class="command"><strong>many-answers</strong></span> is more efficient, but is
4607                   only supported by relatively new slave servers,
4608                   such as <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
4609                   8.x and <acronym class="acronym">BIND</acronym> 4.9.5 onwards.
4610                   The <span class="command"><strong>many-answers</strong></span> format is also supported by
4611                   recent Microsoft Windows nameservers.
4612                   The default is <span class="command"><strong>many-answers</strong></span>.
4613                   <span class="command"><strong>transfer-format</strong></span> may be overridden on a
4614                   per-server basis by using the <span class="command"><strong>server</strong></span>
4615                   statement.
4616                 </p></dd>
4617 <dt><span class="term"><span class="command"><strong>transfers-in</strong></span></span></dt>
4618 <dd><p>
4619                   The maximum number of inbound zone transfers
4620                   that can be running concurrently. The default value is <code class="literal">10</code>.
4621                   Increasing <span class="command"><strong>transfers-in</strong></span> may
4622                   speed up the convergence
4623                   of slave zones, but it also may increase the load on the
4624                   local system.
4625                 </p></dd>
4626 <dt><span class="term"><span class="command"><strong>transfers-out</strong></span></span></dt>
4627 <dd><p>
4628                   The maximum number of outbound zone transfers
4629                   that can be running concurrently. Zone transfer requests in
4630                   excess
4631                   of the limit will be refused. The default value is <code class="literal">10</code>.
4632                 </p></dd>
4633 <dt><span class="term"><span class="command"><strong>transfers-per-ns</strong></span></span></dt>
4634 <dd><p>
4635                   The maximum number of inbound zone transfers
4636                   that can be concurrently transferring from a given remote
4637                   name server.
4638                   The default value is <code class="literal">2</code>.
4639                   Increasing <span class="command"><strong>transfers-per-ns</strong></span>
4640                   may
4641                   speed up the convergence of slave zones, but it also may
4642                   increase
4643                   the load on the remote name server. <span class="command"><strong>transfers-per-ns</strong></span> may
4644                   be overridden on a per-server basis by using the <span class="command"><strong>transfers</strong></span> phrase
4645                   of the <span class="command"><strong>server</strong></span> statement.
4646                 </p></dd>
4647 <dt><span class="term"><span class="command"><strong>transfer-source</strong></span></span></dt>
4648 <dd>
4649 <p><span class="command"><strong>transfer-source</strong></span>
4650                   determines which local address will be bound to IPv4
4651                   TCP connections used to fetch zones transferred
4652                   inbound by the server.  It also determines the
4653                   source IPv4 address, and optionally the UDP port,
4654                   used for the refresh queries and forwarded dynamic
4655                   updates.  If not set, it defaults to a system
4656                   controlled value which will usually be the address
4657                   of the interface "closest to" the remote end. This
4658                   address must appear in the remote end's
4659                   <span class="command"><strong>allow-transfer</strong></span> option for the
4660                   zone being transferred, if one is specified. This
4661                   statement sets the
4662                   <span class="command"><strong>transfer-source</strong></span> for all zones,
4663                   but can be overridden on a per-view or per-zone
4664                   basis by including a
4665                   <span class="command"><strong>transfer-source</strong></span> statement within
4666                   the <span class="command"><strong>view</strong></span> or
4667                   <span class="command"><strong>zone</strong></span> block in the configuration
4668                   file.
4669                 </p>
4670 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4671 <h3 class="title">Note</h3>
4672 <p>
4673                     Solaris 2.5.1 and earlier does not support setting the
4674                     source address for TCP sockets.
4675                   </p>
4676 </div>
4677 </dd>
4678 <dt><span class="term"><span class="command"><strong>transfer-source-v6</strong></span></span></dt>
4679 <dd><p>
4680                   The same as <span class="command"><strong>transfer-source</strong></span>,
4681                   except zone transfers are performed using IPv6.
4682                 </p></dd>
4683 <dt><span class="term"><span class="command"><strong>alt-transfer-source</strong></span></span></dt>
4684 <dd>
4685 <p>
4686                   An alternate transfer source if the one listed in
4687                   <span class="command"><strong>transfer-source</strong></span> fails and
4688                   <span class="command"><strong>use-alt-transfer-source</strong></span> is
4689                   set.
4690                 </p>
4691 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4692 <h3 class="title">Note</h3>
4693 <p>
4694                   If you do not wish the alternate transfer source
4695                   to be used, you should set
4696                   <span class="command"><strong>use-alt-transfer-source</strong></span>
4697                   appropriately and you should not depend upon
4698                   getting an answer back to the first refresh
4699                   query.
4700                 </p>
4701 </div>
4702 </dd>
4703 <dt><span class="term"><span class="command"><strong>alt-transfer-source-v6</strong></span></span></dt>
4704 <dd><p>
4705                   An alternate transfer source if the one listed in
4706                   <span class="command"><strong>transfer-source-v6</strong></span> fails and
4707                   <span class="command"><strong>use-alt-transfer-source</strong></span> is
4708                   set.
4709                 </p></dd>
4710 <dt><span class="term"><span class="command"><strong>use-alt-transfer-source</strong></span></span></dt>
4711 <dd><p>
4712                   Use the alternate transfer sources or not.  If views are
4713                   specified this defaults to <span class="command"><strong>no</strong></span>
4714                   otherwise it defaults to
4715                   <span class="command"><strong>yes</strong></span> (for BIND 8
4716                   compatibility).
4717                 </p></dd>
4718 <dt><span class="term"><span class="command"><strong>notify-source</strong></span></span></dt>
4719 <dd>
4720 <p><span class="command"><strong>notify-source</strong></span>
4721                   determines which local source address, and
4722                   optionally UDP port, will be used to send NOTIFY
4723                   messages.  This address must appear in the slave
4724                   server's <span class="command"><strong>masters</strong></span> zone clause or
4725                   in an <span class="command"><strong>allow-notify</strong></span> clause.  This
4726                   statement sets the <span class="command"><strong>notify-source</strong></span>
4727                   for all zones, but can be overridden on a per-zone or
4728                   per-view basis by including a
4729                   <span class="command"><strong>notify-source</strong></span> statement within
4730                   the <span class="command"><strong>zone</strong></span> or
4731                   <span class="command"><strong>view</strong></span> block in the configuration
4732                   file.
4733                 </p>
4734 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4735 <h3 class="title">Note</h3>
4736 <p>
4737                     Solaris 2.5.1 and earlier does not support setting the
4738                     source address for TCP sockets.
4739                   </p>
4740 </div>
4741 </dd>
4742 <dt><span class="term"><span class="command"><strong>notify-source-v6</strong></span></span></dt>
4743 <dd><p>
4744                   Like <span class="command"><strong>notify-source</strong></span>,
4745                   but applies to notify messages sent to IPv6 addresses.
4746                 </p></dd>
4747 </dl></div>
4748 </div>
4749 <div class="section">
4750 <div class="titlepage"><div><div><h4 class="title">
4751 <a name="port_lists"></a>UDP Port Lists</h4></div></div></div>
4752 <p>
4753             <span class="command"><strong>use-v4-udp-ports</strong></span>,
4754             <span class="command"><strong>avoid-v4-udp-ports</strong></span>,
4755             <span class="command"><strong>use-v6-udp-ports</strong></span>, and
4756             <span class="command"><strong>avoid-v6-udp-ports</strong></span>
4757             specify a list of IPv4 and IPv6 UDP ports that will be
4758             used or not used as source ports for UDP messages.
4759             See <a class="xref" href="Bv9ARM.ch06.html#query_address" title="Query Address">the section called &#8220;Query Address&#8221;</a> about how the
4760             available ports are determined.
4761             For example, with the following configuration
4762           </p>
4763 <pre class="programlisting">
4764 use-v6-udp-ports { range 32768 65535; };
4765 avoid-v6-udp-ports { 40000; range 50000 60000; };
4766 </pre>
4767 <p>
4768              UDP ports of IPv6 messages sent
4769              from <span class="command"><strong>named</strong></span> will be in one
4770              of the following ranges: 32768 to 39999, 40001 to 49999,
4771              and 60001 to 65535.
4772            </p>
4773 <p>
4774              <span class="command"><strong>avoid-v4-udp-ports</strong></span> and
4775              <span class="command"><strong>avoid-v6-udp-ports</strong></span> can be used
4776              to prevent <span class="command"><strong>named</strong></span> from choosing as its random source port a
4777              port that is blocked by your firewall or a port that is
4778              used by other applications;
4779              if a query went out with a source port blocked by a
4780              firewall, the
4781              answer would not get by the firewall and the name server would
4782              have to query again.
4783              Note: the desired range can also be represented only with
4784              <span class="command"><strong>use-v4-udp-ports</strong></span> and
4785              <span class="command"><strong>use-v6-udp-ports</strong></span>, and the
4786              <span class="command"><strong>avoid-</strong></span> options are redundant in that
4787              sense; they are provided for backward compatibility and
4788              to possibly simplify the port specification.
4789            </p>
4790 </div>
4791 <div class="section">
4792 <div class="titlepage"><div><div><h4 class="title">
4793 <a name="resource_limits"></a>Operating System Resource Limits</h4></div></div></div>
4794 <p>
4795             The server's usage of many system resources can be limited.
4796             Scaled values are allowed when specifying resource limits.  For
4797             example, <span class="command"><strong>1G</strong></span> can be used instead of
4798             <span class="command"><strong>1073741824</strong></span> to specify a limit of
4799             one
4800             gigabyte. <span class="command"><strong>unlimited</strong></span> requests
4801             unlimited use, or the
4802             maximum available amount. <span class="command"><strong>default</strong></span>
4803             uses the limit
4804             that was in force when the server was started. See the description
4805             of <span class="command"><strong>size_spec</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#configuration_file_elements" title="Configuration File Elements">the section called &#8220;Configuration File Elements&#8221;</a>.
4806           </p>
4807 <p>
4808             The following options set operating system resource limits for
4809             the name server process.  Some operating systems don't support
4810             some or
4811             any of the limits. On such systems, a warning will be issued if
4812             the
4813             unsupported limit is used.
4814           </p>
4815 <div class="variablelist"><dl class="variablelist">
4816 <dt><span class="term"><span class="command"><strong>coresize</strong></span></span></dt>
4817 <dd><p>
4818                   The maximum size of a core dump. The default
4819                   is <code class="literal">default</code>.
4820                 </p></dd>
4821 <dt><span class="term"><span class="command"><strong>datasize</strong></span></span></dt>
4822 <dd><p>
4823                   The maximum amount of data memory the server
4824                   may use. The default is <code class="literal">default</code>.
4825                   This is a hard limit on server memory usage.
4826                   If the server attempts to allocate memory in excess of this
4827                   limit, the allocation will fail, which may in turn leave
4828                   the server unable to perform DNS service.  Therefore,
4829                   this option is rarely useful as a way of limiting the
4830                   amount of memory used by the server, but it can be used
4831                   to raise an operating system data size limit that is
4832                   too small by default.  If you wish to limit the amount
4833                   of memory used by the server, use the
4834                   <span class="command"><strong>max-cache-size</strong></span> and
4835                   <span class="command"><strong>recursive-clients</strong></span>
4836                   options instead.
4837                 </p></dd>
4838 <dt><span class="term"><span class="command"><strong>files</strong></span></span></dt>
4839 <dd><p>
4840                   The maximum number of files the server
4841                   may have open concurrently. The default is <code class="literal">unlimited</code>.
4842                 </p></dd>
4843 <dt><span class="term"><span class="command"><strong>stacksize</strong></span></span></dt>
4844 <dd><p>
4845                   The maximum amount of stack memory the server
4846                   may use. The default is <code class="literal">default</code>.
4847                 </p></dd>
4848 </dl></div>
4849 </div>
4850 <div class="section">
4851 <div class="titlepage"><div><div><h4 class="title">
4852 <a name="server_resource_limits"></a>Server  Resource Limits</h4></div></div></div>
4853 <p>
4854             The following options set limits on the server's
4855             resource consumption that are enforced internally by the
4856             server rather than the operating system.
4857           </p>
4858 <div class="variablelist"><dl class="variablelist">
4859 <dt><span class="term"><span class="command"><strong>max-ixfr-log-size</strong></span></span></dt>
4860 <dd><p>
4861                   This option is obsolete; it is accepted
4862                   and ignored for BIND 8 compatibility.  The option
4863                   <span class="command"><strong>max-journal-size</strong></span> performs a
4864                   similar function in BIND 9.
4865                 </p></dd>
4866 <dt><span class="term"><span class="command"><strong>max-journal-size</strong></span></span></dt>
4867 <dd><p>
4868                   Sets a maximum size for each journal file
4869                   (see <a class="xref" href="Bv9ARM.ch04.html#journal" title="The journal file">the section called &#8220;The journal file&#8221;</a>).  When the journal file
4870                   approaches
4871                   the specified size, some of the oldest transactions in the
4872                   journal
4873                   will be automatically removed.  The largest permitted
4874                   value is 2 gigabytes. The default is
4875                   <code class="literal">unlimited</code>, which also
4876                   means 2 gigabytes.
4877                   This may also be set on a per-zone basis.
4878                 </p></dd>
4879 <dt><span class="term"><span class="command"><strong>host-statistics-max</strong></span></span></dt>
4880 <dd><p>
4881                   In BIND 8, specifies the maximum number of host statistics
4882                   entries to be kept.
4883                   Not implemented in BIND 9.
4884                 </p></dd>
4885 <dt><span class="term"><span class="command"><strong>recursive-clients</strong></span></span></dt>
4886 <dd>
4887 <p>
4888                   The maximum number ("hard quota") of simultaneous
4889                   recursive lookups the server will perform on behalf
4890                   of clients.  The default is
4891                   <code class="literal">1000</code>.  Because each recursing
4892                   client uses a fair
4893                   bit of memory (on the order of 20 kilobytes), the
4894                   value of the
4895                   <span class="command"><strong>recursive-clients</strong></span> option may
4896                   have to be decreased on hosts with limited memory.
4897                 </p>
4898 <p>
4899                   <code class="option">recursive-clients</code> defines a "hard
4900                   quota" limit for pending recursive clients: when more
4901                   clients than this are pending, new incoming requests
4902                   will not be accepted, and for each incoming request
4903                   a previous pending request will also be dropped.
4904                 </p>
4905 <p>
4906                   A "soft quota" is also set.  When this lower
4907                   quota is exceeded, incoming requests are accepted, but
4908                   for each one, a pending request will be dropped.
4909                   If <code class="option">recursive-clients</code> is greater than
4910                   1000, the soft quota is set to
4911                   <code class="option">recursive-clients</code> minus 100;
4912                   otherwise it is set to 90% of
4913                   <code class="option">recursive-clients</code>.
4914                 </p>
4915 </dd>
4916 <dt><span class="term"><span class="command"><strong>tcp-clients</strong></span></span></dt>
4917 <dd><p>
4918                   The maximum number of simultaneous client TCP
4919                   connections that the server will accept.
4920                   The default is <code class="literal">100</code>.
4921                 </p></dd>
4922 <dt>
4923 <a name="clients-per-query"></a><span class="term"><a name="cpq_term"></a><span class="command"><strong>clients-per-query</strong></span>, </span><span class="term"><span class="command"><strong>max-clients-per-query</strong></span></span>
4924 </dt>
4925 <dd>
4926 <p>These set the
4927                   initial value (minimum) and maximum number of recursive
4928                   simultaneous clients for any given query
4929                   (&lt;qname,qtype,qclass&gt;) that the server will accept
4930                   before dropping additional clients.  <span class="command"><strong>named</strong></span> will attempt to
4931                   self tune this value and changes will be logged.  The
4932                   default values are 10 and 100.
4933                 </p>
4934 <p>
4935                   This value should reflect how many queries come in for
4936                   a given name in the time it takes to resolve that name.
4937                   If the number of queries exceed this value, <span class="command"><strong>named</strong></span> will
4938                   assume that it is dealing with a non-responsive zone
4939                   and will drop additional queries.  If it gets a response
4940                   after dropping queries, it will raise the estimate.  The
4941                   estimate will then be lowered in 20 minutes if it has
4942                   remained unchanged.
4943                 </p>
4944 <p>
4945                   If <span class="command"><strong>clients-per-query</strong></span> is set to zero,
4946                   then there is no limit on the number of clients per query
4947                   and no queries will be dropped.
4948                 </p>
4949 <p>
4950                   If <span class="command"><strong>max-clients-per-query</strong></span> is set to zero,
4951                   then there is no upper bound other than imposed by
4952                   <span class="command"><strong>recursive-clients</strong></span>.
4953                 </p>
4954 </dd>
4955 <dt>
4956 <a name="fetches-per-zone"></a><span class="term"><span class="command"><strong>fetches-per-zone</strong></span></span>
4957 </dt>
4958 <dd>
4959 <p>
4960                   The maximum number of simultaneous iterative
4961                   queries to any one domain that the server will
4962                   permit before blocking new queries for data
4963                   in or beneath that zone.
4964                   This value should reflect how many fetches would
4965                   normally be sent to any one zone in the time it
4966                   would take to resolve them.  It should be smaller
4967                   than <code class="option">recursive-clients</code>.
4968                 </p>
4969 <p>
4970                   When many clients simultaneously query for the
4971                   same name and type, the clients will all be attached
4972                   to the same fetch, up to the
4973                   <code class="option">max-clients-per-query</code> limit,
4974                   and only one iterative query will be sent.
4975                   However, when clients are simultaneously
4976                   querying for <span class="emphasis"><em>different</em></span> names
4977                   or types, multiple queries will be sent and
4978                   <code class="option">max-clients-per-query</code> is not
4979                   effective as a limit.
4980                 </p>
4981 <p>
4982                   Optionally, this value may be followed by the keyword
4983                   <code class="literal">drop</code> or <code class="literal">fail</code>,
4984                   indicating whether queries which exceed the fetch
4985                   quota for a zone will be dropped with no response,
4986                   or answered with SERVFAIL.  The default is
4987                   <code class="literal">drop</code>.
4988                 </p>
4989 <p>
4990                   If <span class="command"><strong>fetches-per-zone</strong></span> is set to zero,
4991                   then there is no limit on the number of fetches per query
4992                   and no queries will be dropped.  The default is zero.
4993                 </p>
4994 <p>
4995                   The current list of active fetches can be dumped by
4996                   running <span class="command"><strong>rndc recursing</strong></span>.  The list
4997                   includes the number of active fetches for each
4998                   domain and the number of queries that have been
4999                   passed or dropped as a result of the
5000                   <code class="option">fetches-per-zone</code> limit.  (Note:
5001                   these counters are not cumulative over time; whenever
5002                   the number of active fetches for a domain drops to
5003                   zero, the counter for that domain is deleted, and the
5004                   next time a fetch is sent to that domain, it is
5005                   recreated with the counters set to zero.)
5006                 </p>
5007 <p>
5008                   (Note: This option is only available when BIND is
5009                   built with <span class="command"><strong>configure --enable-fetchlimit</strong></span>.)
5010                 </p>
5011 </dd>
5012 <dt>
5013 <a name="fetches-per-server"></a><span class="term"><span class="command"><strong>fetches-per-server</strong></span></span>
5014 </dt>
5015 <dd>
5016 <p>
5017                   The maximum number of simultaneous iterative
5018                   queries that the server will allow to be sent to
5019                   a single upstream name server before blocking
5020                   additional queries.
5021                   This value should reflect how many fetches would
5022                   normally be sent to any one server in the time it
5023                   would take to resolve them.  It should be smaller
5024                   than <code class="option">recursive-clients</code>.
5025                 </p>
5026 <p>
5027                   Optionally, this value may be followed by the keyword
5028                   <code class="literal">drop</code> or <code class="literal">fail</code>,
5029                   indicating whether queries will be dropped with no
5030                   response, or answered with SERVFAIL, when all of the
5031                   servers authoritative for a zone are found to have
5032                   exceeded the per-server quota.  The default is
5033                   <code class="literal">fail</code>.
5034                 </p>
5035 <p>
5036                   If <span class="command"><strong>fetches-per-server</strong></span> is set to zero,
5037                   then there is no limit on the number of fetches per query
5038                   and no queries will be dropped.  The default is zero.
5039                 </p>
5040 <p>
5041                   The <span class="command"><strong>fetches-per-server</strong></span> quota is
5042                   dynamically adjusted in response to detected
5043                   congestion. As queries are sent to a server
5044                   and are either answered or time out, an
5045                   exponentially weighted moving average is calculated
5046                   of the ratio of timeouts to responses.  If the
5047                   current average timeout ratio rises above a "high"
5048                   threshold, then <span class="command"><strong>fetches-per-server</strong></span>
5049                   is reduced for that server.  If the timeout ratio
5050                   drops below a "low" threshold, then
5051                   <span class="command"><strong>fetches-per-server</strong></span> is increased.
5052                   The <span class="command"><strong>fetch-quota-params</strong></span> options
5053                   can be used to adjust the parameters for this
5054                   calculation.
5055                 </p>
5056 <p>
5057                   (Note: This option is only available when BIND is
5058                   built with <span class="command"><strong>configure --enable-fetchlimit</strong></span>.)
5059                 </p>
5060 </dd>
5061 <dt><span class="term"><span class="command"><strong>fetch-quota-params</strong></span></span></dt>
5062 <dd>
5063 <p>
5064                   Sets the parameters to use for dynamic resizing of
5065                   the <code class="option">fetches-per-server</code> quota in
5066                   response to detected congestion.
5067                 </p>
5068 <p>
5069                   The first argument is an integer value indicating
5070                   how frequently to recalculate the moving average
5071                   of the ratio of timeouts to responses for each
5072                   server.  The default is 100, meaning we recalculate
5073                   the average ratio after every 100 queries have either
5074                   been answered or timed out.
5075                 </p>
5076 <p>
5077                   The remaining three arguments represent the "low"
5078                   threshold (defaulting to a timeout ratio of 0.1),
5079                   the "high" threshold (defaulting to a timeout
5080                   ratio of 0.3), and the discount rate for
5081                   the moving average (defaulting to 0.7).
5082                   A higher discount rate causes recent events to
5083                   weigh more heavily when calculating the moving
5084                   average; a lower discount rate causes past
5085                   events to weigh more heavily, smoothing out
5086                   short-term blips in the timeout ratio.
5087                   These arguments are all fixed-point numbers with
5088                   precision of 1/100: at most two places after
5089                   the decimal point are significant.
5090                 </p>
5091 <p>
5092                   (Note: This option is only available when BIND is
5093                   built with <span class="command"><strong>configure --enable-fetchlimit</strong></span>.)
5094                 </p>
5095 </dd>
5096 <dt><span class="term"><span class="command"><strong>reserved-sockets</strong></span></span></dt>
5097 <dd>
5098 <p>
5099                   The number of file descriptors reserved for TCP, stdio,
5100                   etc.  This needs to be big enough to cover the number of
5101                   interfaces <span class="command"><strong>named</strong></span> listens on, <span class="command"><strong>tcp-clients</strong></span> as well as
5102                   to provide room for outgoing TCP queries and incoming zone
5103                   transfers.  The default is <code class="literal">512</code>.
5104                   The minimum value is <code class="literal">128</code> and the
5105                   maximum value is <code class="literal">128</code> less than
5106                   maxsockets (-S).  This option may be removed in the future.
5107                 </p>
5108 <p>
5109                   This option has little effect on Windows.
5110                 </p>
5111 </dd>
5112 <dt><span class="term"><span class="command"><strong>max-cache-size</strong></span></span></dt>
5113 <dd><p>
5114                   The maximum amount of memory to use for the
5115                   server's cache, in bytes.
5116                   When the amount of data in the cache
5117                   reaches this limit, the server will cause records to expire
5118                   prematurely based on an LRU based strategy so that
5119                   the limit is not exceeded.
5120                   A value of 0 is special, meaning that
5121                   records are purged from the cache only when their
5122                   TTLs expire.
5123                   Another special keyword <strong class="userinput"><code>unlimited</code></strong>
5124                   means the maximum value of 32-bit unsigned integers
5125                   (0xffffffff), which may not have the same effect as
5126                   0 on machines that support more than 32 bits of
5127                   memory space.
5128                   Any positive values less than 2MB will be ignored reset
5129                   to 2MB.
5130                   In a server with multiple views, the limit applies
5131                   separately to the cache of each view.
5132                   The default is 0.
5133                 </p></dd>
5134 <dt><span class="term"><span class="command"><strong>tcp-listen-queue</strong></span></span></dt>
5135 <dd><p>
5136                   The listen queue depth.  The default and minimum is 10.
5137                   If the kernel supports the accept filter "dataready" this
5138                   also controls how
5139                   many TCP connections that will be queued in kernel space
5140                   waiting for
5141                   some data before being passed to accept.  Nonzero values
5142                   less than 10 will be silently raised. A value of 0 may also
5143                   be used; on most platforms this sets the listen queue
5144                   length to a system-defined default value.
5145                 </p></dd>
5146 </dl></div>
5147 </div>
5148 <div class="section">
5149 <div class="titlepage"><div><div><h4 class="title">
5150 <a name="intervals"></a>Periodic Task Intervals</h4></div></div></div>
5151 <div class="variablelist"><dl class="variablelist">
5152 <dt><span class="term"><span class="command"><strong>cleaning-interval</strong></span></span></dt>
5153 <dd><p>
5154                   This interval is effectively obsolete.  Previously,
5155                   the server would remove expired resource records
5156                   from the cache every <span class="command"><strong>cleaning-interval</strong></span> minutes.
5157                   <acronym class="acronym">BIND</acronym> 9 now manages cache
5158                   memory in a more sophisticated manner and does not
5159                   rely on the periodic cleaning any more.
5160                   Specifying this option therefore has no effect on
5161                   the server's behavior.
5162                 </p></dd>
5163 <dt><span class="term"><span class="command"><strong>heartbeat-interval</strong></span></span></dt>
5164 <dd><p>
5165                   The server will perform zone maintenance tasks
5166                   for all zones marked as <span class="command"><strong>dialup</strong></span> whenever this
5167                   interval expires. The default is 60 minutes. Reasonable
5168                   values are up
5169                   to 1 day (1440 minutes).  The maximum value is 28 days
5170                   (40320 minutes).
5171                   If set to 0, no zone maintenance for these zones will occur.
5172                 </p></dd>
5173 <dt><span class="term"><span class="command"><strong>interface-interval</strong></span></span></dt>
5174 <dd><p>
5175                   The server will scan the network interface list
5176                   every <span class="command"><strong>interface-interval</strong></span>
5177                   minutes. The default
5178                   is 60 minutes. The maximum value is 28 days (40320 minutes).
5179                   If set to 0, interface scanning will only occur when
5180                   the configuration file is  loaded. After the scan, the
5181                   server will
5182                   begin listening for queries on any newly discovered
5183                   interfaces (provided they are allowed by the
5184                   <span class="command"><strong>listen-on</strong></span> configuration), and
5185                   will
5186                   stop listening on interfaces that have gone away.
5187                 </p></dd>
5188 <dt><span class="term"><span class="command"><strong>statistics-interval</strong></span></span></dt>
5189 <dd>
5190 <p>
5191                   Name server statistics will be logged
5192                   every <span class="command"><strong>statistics-interval</strong></span>
5193                   minutes. The default is
5194                   60. The maximum value is 28 days (40320 minutes).
5195                   If set to 0, no statistics will be logged.
5196                   </p>
5197 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5198 <h3 class="title">Note</h3>
5199 <p>
5200                     Not yet implemented in
5201                     <acronym class="acronym">BIND</acronym> 9.
5202                   </p>
5203 </div>
5204 </dd>
5205 </dl></div>
5206 </div>
5207 <div class="section">
5208 <div class="titlepage"><div><div><h4 class="title">
5209 <a name="topology"></a>Topology</h4></div></div></div>
5210 <p>
5211             All other things being equal, when the server chooses a name
5212             server
5213             to query from a list of name servers, it prefers the one that is
5214             topologically closest to itself. The <span class="command"><strong>topology</strong></span> statement
5215             takes an <span class="command"><strong>address_match_list</strong></span> and
5216             interprets it
5217             in a special way. Each top-level list element is assigned a
5218             distance.
5219             Non-negated elements get a distance based on their position in the
5220             list, where the closer the match is to the start of the list, the
5221             shorter the distance is between it and the server. A negated match
5222             will be assigned the maximum distance from the server. If there
5223             is no match, the address will get a distance which is further than
5224             any non-negated list element, and closer than any negated element.
5225             For example,
5226           </p>
5227 <pre class="programlisting">topology {
5228     10/8;
5229     !1.2.3/24;
5230     { 1.2/16; 3/8; };
5231 };</pre>
5232 <p>
5233             will prefer servers on network 10 the most, followed by hosts
5234             on network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the
5235             exception of hosts on network 1.2.3 (netmask 255.255.255.0), which
5236             is preferred least of all.
5237           </p>
5238 <p>
5239             The default topology is
5240           </p>
5241 <pre class="programlisting">    topology { localhost; localnets; };
5242 </pre>
5243 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5244 <h3 class="title">Note</h3>
5245 <p>
5246               The <span class="command"><strong>topology</strong></span> option
5247               is not implemented in <acronym class="acronym">BIND</acronym> 9.
5248             </p>
5249 </div>
5250 </div>
5251 <div class="section">
5252 <div class="titlepage"><div><div><h4 class="title">
5253 <a name="the_sortlist_statement"></a>The <span class="command"><strong>sortlist</strong></span> Statement</h4></div></div></div>
5254 <p>
5255             The response to a DNS query may consist of multiple resource
5256             records (RRs) forming a resource records set (RRset).
5257             The name server will normally return the
5258             RRs within the RRset in an indeterminate order
5259             (but see the <span class="command"><strong>rrset-order</strong></span>
5260             statement in <a class="xref" href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">the section called &#8220;RRset Ordering&#8221;</a>).
5261             The client resolver code should rearrange the RRs as appropriate,
5262             that is, using any addresses on the local net in preference to
5263             other addresses.
5264             However, not all resolvers can do this or are correctly
5265             configured.
5266             When a client is using a local server, the sorting can be performed
5267             in the server, based on the client's address. This only requires
5268             configuring the name servers, not all the clients.
5269           </p>
5270 <p>
5271             The <span class="command"><strong>sortlist</strong></span> statement (see below)
5272             takes
5273             an <span class="command"><strong>address_match_list</strong></span> and
5274             interprets it even
5275             more specifically than the <span class="command"><strong>topology</strong></span>
5276             statement
5277             does (<a class="xref" href="Bv9ARM.ch06.html#topology" title="Topology">the section called &#8220;Topology&#8221;</a>).
5278             Each top level statement in the <span class="command"><strong>sortlist</strong></span> must
5279             itself be an explicit <span class="command"><strong>address_match_list</strong></span> with
5280             one or two elements. The first element (which may be an IP
5281             address,
5282             an IP prefix, an ACL name or a nested <span class="command"><strong>address_match_list</strong></span>)
5283             of each top level list is checked against the source address of
5284             the query until a match is found.
5285           </p>
5286 <p>
5287             Once the source address of the query has been matched, if
5288             the top level statement contains only one element, the actual
5289             primitive
5290             element that matched the source address is used to select the
5291             address
5292             in the response to move to the beginning of the response. If the
5293             statement is a list of two elements, then the second element is
5294             treated the same as the <span class="command"><strong>address_match_list</strong></span> in
5295             a <span class="command"><strong>topology</strong></span> statement. Each top
5296             level element
5297             is assigned a distance and the address in the response with the
5298             minimum
5299             distance is moved to the beginning of the response.
5300           </p>
5301 <p>
5302             In the following example, any queries received from any of
5303             the addresses of the host itself will get responses preferring
5304             addresses
5305             on any of the locally connected networks. Next most preferred are
5306             addresses
5307             on the 192.168.1/24 network, and after that either the
5308             192.168.2/24
5309             or
5310             192.168.3/24 network with no preference shown between these two
5311             networks. Queries received from a host on the 192.168.1/24 network
5312             will prefer other addresses on that network to the 192.168.2/24
5313             and
5314             192.168.3/24 networks. Queries received from a host on the
5315             192.168.4/24
5316             or the 192.168.5/24 network will only prefer other addresses on
5317             their directly connected networks.
5318           </p>
5319 <pre class="programlisting">sortlist {
5320     // IF the local host
5321     // THEN first fit on the following nets
5322     { localhost;
5323         { localnets;
5324             192.168.1/24;
5325             { 192.168.2/24; 192.168.3/24; }; }; };
5326     // IF on class C 192.168.1 THEN use .1, or .2 or .3
5327     { 192.168.1/24;
5328         { 192.168.1/24;
5329             { 192.168.2/24; 192.168.3/24; }; }; };
5330     // IF on class C 192.168.2 THEN use .2, or .1 or .3
5331     { 192.168.2/24;
5332         { 192.168.2/24;
5333             { 192.168.1/24; 192.168.3/24; }; }; };
5334     // IF on class C 192.168.3 THEN use .3, or .1 or .2
5335     { 192.168.3/24;
5336         { 192.168.3/24;
5337             { 192.168.1/24; 192.168.2/24; }; }; };
5338     // IF .4 or .5 THEN prefer that net
5339     { { 192.168.4/24; 192.168.5/24; };
5340     };
5341 };</pre>
5342 <p>
5343             The following example will give reasonable behavior for the
5344             local host and hosts on directly connected networks. It is similar
5345             to the behavior of the address sort in <acronym class="acronym">BIND</acronym> 4.9.x. Responses sent
5346             to queries from the local host will favor any of the directly
5347             connected
5348             networks. Responses sent to queries from any other hosts on a
5349             directly
5350             connected network will prefer addresses on that same network.
5351             Responses
5352             to other queries will not be sorted.
5353           </p>
5354 <pre class="programlisting">sortlist {
5355            { localhost; localnets; };
5356            { localnets; };
5357 };
5358 </pre>
5359 </div>
5360 <div class="section">
5361 <div class="titlepage"><div><div><h4 class="title">
5362 <a name="rrset_ordering"></a>RRset Ordering</h4></div></div></div>
5363 <p>
5364             When multiple records are returned in an answer it may be
5365             useful to configure the order of the records placed into the
5366             response.
5367             The <span class="command"><strong>rrset-order</strong></span> statement permits
5368             configuration
5369             of the ordering of the records in a multiple record response.
5370             See also the <span class="command"><strong>sortlist</strong></span> statement,
5371             <a class="xref" href="Bv9ARM.ch06.html#the_sortlist_statement" title="The sortlist Statement">the section called &#8220;The <span class="command"><strong>sortlist</strong></span> Statement&#8221;</a>.
5372           </p>
5373 <p>
5374             An <span class="command"><strong>order_spec</strong></span> is defined as
5375             follows:
5376           </p>
5377 <p>
5378             [<span class="optional">class <em class="replaceable"><code>class_name</code></em></span>]
5379             [<span class="optional">type <em class="replaceable"><code>type_name</code></em></span>]
5380             [<span class="optional">name <em class="replaceable"><code>"domain_name"</code></em></span>]
5381             order <em class="replaceable"><code>ordering</code></em>
5382           </p>
5383 <p>
5384             If no class is specified, the default is <span class="command"><strong>ANY</strong></span>.
5385             If no type is specified, the default is <span class="command"><strong>ANY</strong></span>.
5386             If no name is specified, the default is "<span class="command"><strong>*</strong></span>" (asterisk).
5387           </p>
5388 <p>
5389             The legal values for <span class="command"><strong>ordering</strong></span> are:
5390           </p>
5391 <div class="informaltable"><table border="1">
5392 <colgroup>
5393 <col width="0.750in" class="1">
5394 <col width="3.750in" class="2">
5395 </colgroup>
5396 <tbody>
5397 <tr>
5398 <td>
5399                     <p><span class="command"><strong>fixed</strong></span></p>
5400                   </td>
5401 <td>
5402                     <p>
5403                       Records are returned in the order they
5404                       are defined in the zone file.
5405                     </p>
5406                   </td>
5407 </tr>
5408 <tr>
5409 <td>
5410                     <p><span class="command"><strong>random</strong></span></p>
5411                   </td>
5412 <td>
5413                     <p>
5414                       Records are returned in some random order.
5415                     </p>
5416                   </td>
5417 </tr>
5418 <tr>
5419 <td>
5420                     <p><span class="command"><strong>cyclic</strong></span></p>
5421                   </td>
5422 <td>
5423                     <p>
5424                       Records are returned in a cyclic round-robin order.
5425                     </p>
5426                     <p>
5427                       If <acronym class="acronym">BIND</acronym> is configured with the
5428                       "--enable-fixed-rrset" option at compile time, then
5429                       the initial ordering of the RRset will match the
5430                       one specified in the zone file.
5431                     </p>
5432                   </td>
5433 </tr>
5434 </tbody>
5435 </table></div>
5436 <p>
5437             For example:
5438           </p>
5439 <pre class="programlisting">rrset-order {
5440    class IN type A name "host.example.com" order random;
5441    order cyclic;
5442 };
5443 </pre>
5444 <p>
5445             will cause any responses for type A records in class IN that
5446             have "<code class="literal">host.example.com</code>" as a
5447             suffix, to always be returned
5448             in random order. All other records are returned in cyclic order.
5449           </p>
5450 <p>
5451             If multiple <span class="command"><strong>rrset-order</strong></span> statements
5452             appear, they are not combined &#8212; the last one applies.
5453           </p>
5454 <p>
5455             By default, all records are returned in random order.
5456           </p>
5457 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5458 <h3 class="title">Note</h3>
5459 <p>
5460               In this release of <acronym class="acronym">BIND</acronym> 9, the
5461               <span class="command"><strong>rrset-order</strong></span> statement does not support
5462               "fixed" ordering by default.  Fixed ordering can be enabled
5463               at compile time by specifying "--enable-fixed-rrset" on
5464               the "configure" command line.
5465             </p>
5466 </div>
5467 </div>
5468 <div class="section">
5469 <div class="titlepage"><div><div><h4 class="title">
5470 <a name="tuning"></a>Tuning</h4></div></div></div>
5471 <div class="variablelist"><dl class="variablelist">
5472 <dt><span class="term"><span class="command"><strong>lame-ttl</strong></span></span></dt>
5473 <dd>
5474 <p>
5475                   Sets the number of seconds to cache a
5476                   lame server indication. 0 disables caching. (This is
5477                   <span class="bold"><strong>NOT</strong></span> recommended.)
5478                   The default is <code class="literal">600</code> (10 minutes) and the
5479                   maximum value is
5480                   <code class="literal">1800</code> (30 minutes).
5481                 </p>
5482 <p>
5483                   Lame-ttl also controls the amount of time DNSSEC
5484                   validation failures are cached.  There is a minimum
5485                   of 30 seconds applied to bad cache entries if the
5486                   lame-ttl is set to less than 30 seconds.
5487                 </p>
5488 </dd>
5489 <dt><span class="term"><span class="command"><strong>max-ncache-ttl</strong></span></span></dt>
5490 <dd><p>
5491                   To reduce network traffic and increase performance,
5492                   the server stores negative answers. <span class="command"><strong>max-ncache-ttl</strong></span> is
5493                   used to set a maximum retention time for these answers in
5494                   the server
5495                   in seconds. The default
5496                   <span class="command"><strong>max-ncache-ttl</strong></span> is <code class="literal">10800</code> seconds (3 hours).
5497                   <span class="command"><strong>max-ncache-ttl</strong></span> cannot exceed
5498                   7 days and will
5499                   be silently truncated to 7 days if set to a greater value.
5500                 </p></dd>
5501 <dt><span class="term"><span class="command"><strong>max-cache-ttl</strong></span></span></dt>
5502 <dd><p>
5503                   Sets the maximum time for which the server will
5504                   cache ordinary (positive) answers. The default is
5505                   one week (7 days).
5506                   A value of zero may cause all queries to return
5507                   SERVFAIL, because of lost caches of intermediate
5508                   RRsets (such as NS and glue AAAA/A records) in the
5509                   resolution process.
5510                 </p></dd>
5511 <dt><span class="term"><span class="command"><strong>min-roots</strong></span></span></dt>
5512 <dd>
5513 <p>
5514                   The minimum number of root servers that
5515                   is required for a request for the root servers to be
5516                   accepted. The default
5517                   is <strong class="userinput"><code>2</code></strong>.
5518                 </p>
5519 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5520 <h3 class="title">Note</h3>
5521 <p>
5522                     Not implemented in <acronym class="acronym">BIND</acronym> 9.
5523                   </p>
5524 </div>
5525 </dd>
5526 <dt><span class="term"><span class="command"><strong>sig-validity-interval</strong></span></span></dt>
5527 <dd>
5528 <p>
5529                   Specifies the number of days into the future when
5530                   DNSSEC signatures automatically generated as a
5531                   result of dynamic updates (<a class="xref" href="Bv9ARM.ch04.html#dynamic_update" title="Dynamic Update">the section called &#8220;Dynamic Update&#8221;</a>) will expire.  There
5532                   is an optional second field which specifies how
5533                   long before expiry that the signatures will be
5534                   regenerated.  If not specified, the signatures will
5535                   be regenerated at 1/4 of base interval.  The second
5536                   field is specified in days if the base interval is
5537                   greater than 7 days otherwise it is specified in hours.
5538                   The default base interval is <code class="literal">30</code> days
5539                   giving a re-signing interval of 7 1/2 days.  The maximum
5540                   values are 10 years (3660 days).
5541                 </p>
5542 <p>
5543                   The signature inception time is unconditionally
5544                   set to one hour before the current time to allow
5545                   for a limited amount of clock skew.
5546                 </p>
5547 <p>
5548                   The <span class="command"><strong>sig-validity-interval</strong></span>
5549                   should be, at least, several multiples of the SOA
5550                   expire interval to allow for reasonable interaction
5551                   between the various timer and expiry dates.
5552                 </p>
5553 </dd>
5554 <dt><span class="term"><span class="command"><strong>sig-signing-nodes</strong></span></span></dt>
5555 <dd><p>
5556                   Specify the maximum number of nodes to be
5557                   examined in each quantum when signing a zone with
5558                   a new DNSKEY. The default is
5559                   <code class="literal">100</code>.
5560                 </p></dd>
5561 <dt><span class="term"><span class="command"><strong>sig-signing-signatures</strong></span></span></dt>
5562 <dd><p>
5563                   Specify a threshold number of signatures that
5564                   will terminate processing a quantum when signing
5565                   a zone with a new DNSKEY.  The default is
5566                   <code class="literal">10</code>.
5567                 </p></dd>
5568 <dt><span class="term"><span class="command"><strong>sig-signing-type</strong></span></span></dt>
5569 <dd>
5570 <p>
5571                   Specify a private RDATA type to be used when generating
5572                   signing state records.  The default is
5573                   <code class="literal">65534</code>.
5574                 </p>
5575 <p>
5576                   It is expected that this parameter may be removed
5577                   in a future version once there is a standard type.
5578                 </p>
5579 <p>
5580                   Signing state records are used to internally by
5581                   <span class="command"><strong>named</strong></span> to track the current state of
5582                   a zone-signing process, i.e., whether it is still active
5583                   or has been completed.  The records can be inspected
5584                   using the command
5585                   <span class="command"><strong>rndc signing -list <em class="replaceable"><code>zone</code></em></strong></span>.
5586                   Once <span class="command"><strong>named</strong></span> has finished signing
5587                   a zone with a particular key, the signing state
5588                   record associated with that key can be removed from
5589                   the zone by running
5590                   <span class="command"><strong>rndc signing -clear <em class="replaceable"><code>keyid/algorithm</code></em> <em class="replaceable"><code>zone</code></em></strong></span>.
5591                   To clear all of the completed signing state
5592                   records for a zone, use
5593                   <span class="command"><strong>rndc signing -clear all <em class="replaceable"><code>zone</code></em></strong></span>.
5594                 </p>
5595 </dd>
5596 <dt>
5597 <span class="term"><span class="command"><strong>min-refresh-time</strong></span>, </span><span class="term"><span class="command"><strong>max-refresh-time</strong></span>, </span><span class="term"><span class="command"><strong>min-retry-time</strong></span>, </span><span class="term"><span class="command"><strong>max-retry-time</strong></span></span>
5598 </dt>
5599 <dd>
5600 <p>
5601                   These options control the server's behavior on refreshing a
5602                   zone
5603                   (querying for SOA changes) or retrying failed transfers.
5604                   Usually the SOA values for the zone are used, but these
5605                   values
5606                   are set by the master, giving slave server administrators
5607                   little
5608                   control over their contents.
5609                 </p>
5610 <p>
5611                   These options allow the administrator to set a minimum and
5612                   maximum
5613                   refresh and retry time either per-zone, per-view, or
5614                   globally.
5615                   These options are valid for slave and stub zones,
5616                   and clamp the SOA refresh and retry times to the specified
5617                   values.
5618                 </p>
5619 <p>
5620                   The following defaults apply.
5621                   <span class="command"><strong>min-refresh-time</strong></span> 300 seconds,
5622                   <span class="command"><strong>max-refresh-time</strong></span> 2419200 seconds
5623                   (4 weeks), <span class="command"><strong>min-retry-time</strong></span> 500 seconds,
5624                   and <span class="command"><strong>max-retry-time</strong></span> 1209600 seconds
5625                   (2 weeks).
5626                 </p>
5627 </dd>
5628 <dt><span class="term"><span class="command"><strong>edns-udp-size</strong></span></span></dt>
5629 <dd>
5630 <p>
5631                   Sets the advertised EDNS UDP buffer size in bytes
5632                   to control the size of packets received.
5633                   Valid values are 512 to 4096 (values outside this range
5634                   will be silently adjusted).  The default value
5635                   is 4096.  The usual reason for setting
5636                   <span class="command"><strong>edns-udp-size</strong></span> to a non-default
5637                   value is to get UDP answers to pass through broken
5638                   firewalls that block fragmented packets and/or
5639                   block UDP packets that are greater than 512 bytes.
5640                 </p>
5641 <p>
5642                   <span class="command"><strong>named</strong></span> will fallback to using 512 bytes
5643                   if it get a series of timeout at the initial value.  512
5644                   bytes is not being offered to encourage sites to fix their
5645                   firewalls.  Small EDNS UDP sizes will result in the
5646                   excessive use of TCP.
5647                 </p>
5648 </dd>
5649 <dt><span class="term"><span class="command"><strong>max-udp-size</strong></span></span></dt>
5650 <dd>
5651 <p>
5652                   Sets the maximum EDNS UDP message size
5653                   <span class="command"><strong>named</strong></span> will send in bytes.
5654                   Valid values are 512 to 4096 (values outside this
5655                   range will be silently adjusted).  The default
5656                   value is 4096.  The usual reason for setting
5657                   <span class="command"><strong>max-udp-size</strong></span> to a non-default
5658                   value is to get UDP answers to pass through broken
5659                   firewalls that block fragmented packets and/or
5660                   block UDP packets that are greater than 512 bytes.
5661                   This is independent of the advertised receive
5662                   buffer (<span class="command"><strong>edns-udp-size</strong></span>).
5663                 </p>
5664 <p>
5665                   Setting this to a low value will encourage additional
5666                   TCP traffic to the nameserver.
5667                 </p>
5668 </dd>
5669 <dt><span class="term"><span class="command"><strong>masterfile-format</strong></span></span></dt>
5670 <dd>
5671 <p>Specifies
5672                   the file format of zone files (see
5673                   <a class="xref" href="Bv9ARM.ch06.html#zonefile_format" title="Additional File Formats">the section called &#8220;Additional File Formats&#8221;</a>).
5674                   The default value is <code class="constant">text</code>, which is the
5675                   standard textual representation, except for slave zones,
5676                   in which the default value is <code class="constant">raw</code>.
5677                   Files in other formats than <code class="constant">text</code> are
5678                   typically expected to be generated by the
5679                   <span class="command"><strong>named-compilezone</strong></span> tool, or dumped by
5680                   <span class="command"><strong>named</strong></span>.
5681                 </p>
5682 <p>
5683                   Note that when a zone file in a different format than
5684                   <code class="constant">text</code> is loaded, <span class="command"><strong>named</strong></span>
5685                   may omit some of the checks which would be performed for a
5686                   file in the <code class="constant">text</code> format.  In particular,
5687                   <span class="command"><strong>check-names</strong></span> checks do not apply
5688                   for the <code class="constant">raw</code> format.  This means
5689                   a zone file in the <code class="constant">raw</code> format
5690                   must be generated with the same check level as that
5691                   specified in the <span class="command"><strong>named</strong></span> configuration
5692                   file.  This statement sets the
5693                   <span class="command"><strong>masterfile-format</strong></span> for all zones,
5694                   but can be overridden on a per-zone or per-view basis
5695                   by including a <span class="command"><strong>masterfile-format</strong></span>
5696                   statement within the <span class="command"><strong>zone</strong></span> or
5697                   <span class="command"><strong>view</strong></span> block in the configuration
5698                   file.
5699                 </p>
5700 </dd>
5701 <dt>
5702 <a name="max-recursion-depth"></a><span class="term"><span class="command"><strong>max-recursion-depth</strong></span></span>
5703 </dt>
5704 <dd><p>
5705                   Sets the maximum number of levels of recursion
5706                   that are permitted at any one time while servicing
5707                   a recursive query. Resolving a name may require
5708                   looking up a name server address, which in turn
5709                   requires resolving another name, etc; if the number
5710                   of indirections exceeds this value, the recursive
5711                   query is terminated and returns SERVFAIL.  The
5712                   default is 7.
5713                 </p></dd>
5714 <dt>
5715 <a name="max-recursion-queries"></a><span class="term"><span class="command"><strong>max-recursion-queries</strong></span></span>
5716 </dt>
5717 <dd><p>
5718                   Sets the maximum number of iterative queries that
5719                   may be sent while servicing a recursive query.
5720                   If more queries are sent, the recursive query
5721                   is terminated and returns SERVFAIL. Queries to
5722                   look up top level comains such as "com" and "net"
5723                   and the DNS root zone are exempt from this limitation.
5724                   The default is 75.
5725                 </p></dd>
5726 <dt><span class="term"><span class="command"><strong>notify-delay</strong></span></span></dt>
5727 <dd>
5728 <p>
5729                   The delay, in seconds, between sending sets of notify
5730                   messages for a zone.  The default is five (5) seconds.
5731                 </p>
5732 <p>
5733                   The overall rate that NOTIFY messages are sent for all
5734                   zones is controlled by <span class="command"><strong>serial-query-rate</strong></span>.
5735                 </p>
5736 </dd>
5737 <dt><span class="term"><span class="command"><strong>max-rsa-exponent-size</strong></span></span></dt>
5738 <dd><p>
5739                   The maximum RSA exponent size, in bits, that will
5740                   be accepted when validating.  Valid values are 35
5741                   to 4096 bits.  The default zero (0) is also accepted
5742                   and is equivalent to 4096.
5743                 </p></dd>
5744 </dl></div>
5745 </div>
5746 <div class="section">
5747 <div class="titlepage"><div><div><h4 class="title">
5748 <a name="builtin"></a>Built-in server information zones</h4></div></div></div>
5749 <p>
5750             The server provides some helpful diagnostic information
5751             through a number of built-in zones under the
5752             pseudo-top-level-domain <code class="literal">bind</code> in the
5753             <span class="command"><strong>CHAOS</strong></span> class.  These zones are part
5754             of a
5755             built-in view (see <a class="xref" href="Bv9ARM.ch06.html#view_statement_grammar" title="view Statement Grammar">the section called &#8220;<span class="command"><strong>view</strong></span> Statement Grammar&#8221;</a>) of
5756             class
5757             <span class="command"><strong>CHAOS</strong></span> which is separate from the
5758             default view of class <span class="command"><strong>IN</strong></span>. Most global
5759             configuration options (<span class="command"><strong>allow-query</strong></span>,
5760             etc) will apply to this view, but some are locally
5761             overridden: <span class="command"><strong>notify</strong></span>,
5762             <span class="command"><strong>recursion</strong></span> and
5763             <span class="command"><strong>allow-new-zones</strong></span> are
5764             always set to <strong class="userinput"><code>no</code></strong>.
5765           </p>
5766 <p>
5767             If you need to disable these zones, use the options
5768             below, or hide the built-in <span class="command"><strong>CHAOS</strong></span>
5769             view by
5770             defining an explicit view of class <span class="command"><strong>CHAOS</strong></span>
5771             that matches all clients.
5772           </p>
5773 <div class="variablelist"><dl class="variablelist">
5774 <dt><span class="term"><span class="command"><strong>version</strong></span></span></dt>
5775 <dd><p>
5776                   The version the server should report
5777                   via a query of the name <code class="literal">version.bind</code>
5778                   with type <span class="command"><strong>TXT</strong></span>, class <span class="command"><strong>CHAOS</strong></span>.
5779                   The default is the real version number of this server.
5780                   Specifying <span class="command"><strong>version none</strong></span>
5781                   disables processing of the queries.
5782                 </p></dd>
5783 <dt><span class="term"><span class="command"><strong>hostname</strong></span></span></dt>
5784 <dd><p>
5785                   The hostname the server should report via a query of
5786                   the name <code class="filename">hostname.bind</code>
5787                   with type <span class="command"><strong>TXT</strong></span>, class <span class="command"><strong>CHAOS</strong></span>.
5788                   This defaults to the hostname of the machine hosting the
5789                   name server as
5790                   found by the gethostname() function.  The primary purpose of such queries
5791                   is to
5792                   identify which of a group of anycast servers is actually
5793                   answering your queries.  Specifying <span class="command"><strong>hostname none;</strong></span>
5794                   disables processing of the queries.
5795                 </p></dd>
5796 <dt><span class="term"><span class="command"><strong>server-id</strong></span></span></dt>
5797 <dd><p>
5798                   The ID the server should report when receiving a Name
5799                   Server Identifier (NSID) query, or a query of the name
5800                   <code class="filename">ID.SERVER</code> with type
5801                   <span class="command"><strong>TXT</strong></span>, class <span class="command"><strong>CHAOS</strong></span>.
5802                   The primary purpose of such queries is to
5803                   identify which of a group of anycast servers is actually
5804                   answering your queries.  Specifying <span class="command"><strong>server-id none;</strong></span>
5805                   disables processing of the queries.
5806                   Specifying <span class="command"><strong>server-id hostname;</strong></span> will cause <span class="command"><strong>named</strong></span> to
5807                   use the hostname as found by the gethostname() function.
5808                   The default <span class="command"><strong>server-id</strong></span> is <span class="command"><strong>none</strong></span>.
5809                 </p></dd>
5810 </dl></div>
5811 </div>
5812 <div class="section">
5813 <div class="titlepage"><div><div><h4 class="title">
5814 <a name="empty"></a>Built-in Empty Zones</h4></div></div></div>
5815 <p>
5816             Named has some built-in empty zones (SOA and NS records only).
5817             These are for zones that should normally be answered locally
5818             and which queries should not be sent to the Internet's root
5819             servers.  The official servers which cover these namespaces
5820             return NXDOMAIN responses to these queries.  In particular,
5821             these cover the reverse namespaces for addresses from
5822             RFC 1918, RFC 4193, RFC 5737 and RFC 6598.  They also include the
5823             reverse namespace for IPv6 local address (locally assigned),
5824             IPv6 link local addresses, the IPv6 loopback address and the
5825             IPv6 unknown address.
5826           </p>
5827 <p>
5828             Named will attempt to determine if a built-in zone already exists
5829             or is active (covered by a forward-only forwarding declaration)
5830             and will not create an empty zone in that case.
5831           </p>
5832 <p>
5833             The current list of empty zones is:
5834             </p>
5835 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
5836 <li class="listitem">10.IN-ADDR.ARPA</li>
5837 <li class="listitem">16.172.IN-ADDR.ARPA</li>
5838 <li class="listitem">17.172.IN-ADDR.ARPA</li>
5839 <li class="listitem">18.172.IN-ADDR.ARPA</li>
5840 <li class="listitem">19.172.IN-ADDR.ARPA</li>
5841 <li class="listitem">20.172.IN-ADDR.ARPA</li>
5842 <li class="listitem">21.172.IN-ADDR.ARPA</li>
5843 <li class="listitem">22.172.IN-ADDR.ARPA</li>
5844 <li class="listitem">23.172.IN-ADDR.ARPA</li>
5845 <li class="listitem">24.172.IN-ADDR.ARPA</li>
5846 <li class="listitem">25.172.IN-ADDR.ARPA</li>
5847 <li class="listitem">26.172.IN-ADDR.ARPA</li>
5848 <li class="listitem">27.172.IN-ADDR.ARPA</li>
5849 <li class="listitem">28.172.IN-ADDR.ARPA</li>
5850 <li class="listitem">29.172.IN-ADDR.ARPA</li>
5851 <li class="listitem">30.172.IN-ADDR.ARPA</li>
5852 <li class="listitem">31.172.IN-ADDR.ARPA</li>
5853 <li class="listitem">168.192.IN-ADDR.ARPA</li>
5854 <li class="listitem">64.100.IN-ADDR.ARPA</li>
5855 <li class="listitem">65.100.IN-ADDR.ARPA</li>
5856 <li class="listitem">66.100.IN-ADDR.ARPA</li>
5857 <li class="listitem">67.100.IN-ADDR.ARPA</li>
5858 <li class="listitem">68.100.IN-ADDR.ARPA</li>
5859 <li class="listitem">69.100.IN-ADDR.ARPA</li>
5860 <li class="listitem">70.100.IN-ADDR.ARPA</li>
5861 <li class="listitem">71.100.IN-ADDR.ARPA</li>
5862 <li class="listitem">72.100.IN-ADDR.ARPA</li>
5863 <li class="listitem">73.100.IN-ADDR.ARPA</li>
5864 <li class="listitem">74.100.IN-ADDR.ARPA</li>
5865 <li class="listitem">75.100.IN-ADDR.ARPA</li>
5866 <li class="listitem">76.100.IN-ADDR.ARPA</li>
5867 <li class="listitem">77.100.IN-ADDR.ARPA</li>
5868 <li class="listitem">78.100.IN-ADDR.ARPA</li>
5869 <li class="listitem">79.100.IN-ADDR.ARPA</li>
5870 <li class="listitem">80.100.IN-ADDR.ARPA</li>
5871 <li class="listitem">81.100.IN-ADDR.ARPA</li>
5872 <li class="listitem">82.100.IN-ADDR.ARPA</li>
5873 <li class="listitem">83.100.IN-ADDR.ARPA</li>
5874 <li class="listitem">84.100.IN-ADDR.ARPA</li>
5875 <li class="listitem">85.100.IN-ADDR.ARPA</li>
5876 <li class="listitem">86.100.IN-ADDR.ARPA</li>
5877 <li class="listitem">87.100.IN-ADDR.ARPA</li>
5878 <li class="listitem">88.100.IN-ADDR.ARPA</li>
5879 <li class="listitem">89.100.IN-ADDR.ARPA</li>
5880 <li class="listitem">90.100.IN-ADDR.ARPA</li>
5881 <li class="listitem">91.100.IN-ADDR.ARPA</li>
5882 <li class="listitem">92.100.IN-ADDR.ARPA</li>
5883 <li class="listitem">93.100.IN-ADDR.ARPA</li>
5884 <li class="listitem">94.100.IN-ADDR.ARPA</li>
5885 <li class="listitem">95.100.IN-ADDR.ARPA</li>
5886 <li class="listitem">96.100.IN-ADDR.ARPA</li>
5887 <li class="listitem">97.100.IN-ADDR.ARPA</li>
5888 <li class="listitem">98.100.IN-ADDR.ARPA</li>
5889 <li class="listitem">99.100.IN-ADDR.ARPA</li>
5890 <li class="listitem">100.100.IN-ADDR.ARPA</li>
5891 <li class="listitem">101.100.IN-ADDR.ARPA</li>
5892 <li class="listitem">102.100.IN-ADDR.ARPA</li>
5893 <li class="listitem">103.100.IN-ADDR.ARPA</li>
5894 <li class="listitem">104.100.IN-ADDR.ARPA</li>
5895 <li class="listitem">105.100.IN-ADDR.ARPA</li>
5896 <li class="listitem">106.100.IN-ADDR.ARPA</li>
5897 <li class="listitem">107.100.IN-ADDR.ARPA</li>
5898 <li class="listitem">108.100.IN-ADDR.ARPA</li>
5899 <li class="listitem">109.100.IN-ADDR.ARPA</li>
5900 <li class="listitem">110.100.IN-ADDR.ARPA</li>
5901 <li class="listitem">111.100.IN-ADDR.ARPA</li>
5902 <li class="listitem">112.100.IN-ADDR.ARPA</li>
5903 <li class="listitem">113.100.IN-ADDR.ARPA</li>
5904 <li class="listitem">114.100.IN-ADDR.ARPA</li>
5905 <li class="listitem">115.100.IN-ADDR.ARPA</li>
5906 <li class="listitem">116.100.IN-ADDR.ARPA</li>
5907 <li class="listitem">117.100.IN-ADDR.ARPA</li>
5908 <li class="listitem">118.100.IN-ADDR.ARPA</li>
5909 <li class="listitem">119.100.IN-ADDR.ARPA</li>
5910 <li class="listitem">120.100.IN-ADDR.ARPA</li>
5911 <li class="listitem">121.100.IN-ADDR.ARPA</li>
5912 <li class="listitem">122.100.IN-ADDR.ARPA</li>
5913 <li class="listitem">123.100.IN-ADDR.ARPA</li>
5914 <li class="listitem">124.100.IN-ADDR.ARPA</li>
5915 <li class="listitem">125.100.IN-ADDR.ARPA</li>
5916 <li class="listitem">126.100.IN-ADDR.ARPA</li>
5917 <li class="listitem">127.100.IN-ADDR.ARPA</li>
5918 <li class="listitem">0.IN-ADDR.ARPA</li>
5919 <li class="listitem">127.IN-ADDR.ARPA</li>
5920 <li class="listitem">254.169.IN-ADDR.ARPA</li>
5921 <li class="listitem">2.0.192.IN-ADDR.ARPA</li>
5922 <li class="listitem">100.51.198.IN-ADDR.ARPA</li>
5923 <li class="listitem">113.0.203.IN-ADDR.ARPA</li>
5924 <li class="listitem">255.255.255.255.IN-ADDR.ARPA</li>
5925 <li class="listitem">0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA</li>
5926 <li class="listitem">1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.IP6.ARPA</li>
5927 <li class="listitem">8.B.D.0.1.0.0.2.IP6.ARPA</li>
5928 <li class="listitem">D.F.IP6.ARPA</li>
5929 <li class="listitem">8.E.F.IP6.ARPA</li>
5930 <li class="listitem">9.E.F.IP6.ARPA</li>
5931 <li class="listitem">A.E.F.IP6.ARPA</li>
5932 <li class="listitem">B.E.F.IP6.ARPA</li>
5933 </ul></div>
5934 <p>
5935           </p>
5936 <p>
5937             Empty zones are settable at the view level and only apply to
5938             views of class IN.  Disabled empty zones are only inherited
5939             from options if there are no disabled empty zones specified
5940             at the view level.  To override the options list of disabled
5941             zones, you can disable the root zone at the view level, for example:
5942 </p>
5943 <pre class="programlisting">
5944             disable-empty-zone ".";
5945 </pre>
5946 <p>
5947           </p>
5948 <p>
5949             If you are using the address ranges covered here, you should
5950             already have reverse zones covering the addresses you use.
5951             In practice this appears to not be the case with many queries
5952             being made to the infrastructure servers for names in these
5953             spaces.  So many in fact that sacrificial servers were needed
5954             to be deployed to channel the query load away from the
5955             infrastructure servers.
5956           </p>
5957 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5958 <h3 class="title">Note</h3>
5959 <p>
5960             The real parent servers for these zones should disable all
5961             empty zone under the parent zone they serve.  For the real
5962             root servers, this is all built-in empty zones.  This will
5963             enable them to return referrals to deeper in the tree.
5964           </p>
5965 </div>
5966 <div class="variablelist"><dl class="variablelist">
5967 <dt><span class="term"><span class="command"><strong>empty-server</strong></span></span></dt>
5968 <dd><p>
5969                   Specify what server name will appear in the returned
5970                   SOA record for empty zones.  If none is specified, then
5971                   the zone's name will be used.
5972                 </p></dd>
5973 <dt><span class="term"><span class="command"><strong>empty-contact</strong></span></span></dt>
5974 <dd><p>
5975                   Specify what contact name will appear in the returned
5976                   SOA record for empty zones.  If none is specified, then
5977                   "." will be used.
5978                 </p></dd>
5979 <dt><span class="term"><span class="command"><strong>empty-zones-enable</strong></span></span></dt>
5980 <dd><p>
5981                   Enable or disable all empty zones.  By default, they
5982                   are enabled.
5983                 </p></dd>
5984 <dt><span class="term"><span class="command"><strong>disable-empty-zone</strong></span></span></dt>
5985 <dd><p>
5986                   Disable individual empty zones.  By default, none are
5987                   disabled.  This option can be specified multiple times.
5988                 </p></dd>
5989 </dl></div>
5990 </div>
5991 <div class="section">
5992 <div class="titlepage"><div><div><h4 class="title">
5993 <a name="acache"></a>Additional Section Caching</h4></div></div></div>
5994 <p>
5995             The additional section cache, also called <span class="command"><strong>acache</strong></span>,
5996             is an internal cache to improve the response performance of BIND 9.
5997             When additional section caching is enabled, BIND 9 will
5998             cache an internal short-cut to the additional section content for
5999             each answer RR.
6000             Note that <span class="command"><strong>acache</strong></span> is an internal caching
6001             mechanism of BIND 9, and is not related to the DNS caching
6002             server function.
6003           </p>
6004 <p>
6005             Additional section caching does not change the
6006             response content (except the RRsets ordering of the additional
6007             section, see below), but can improve the response performance
6008             significantly.
6009             It is particularly effective when BIND 9 acts as an authoritative
6010             server for a zone that has many delegations with many glue RRs.
6011           </p>
6012 <p>
6013             In order to obtain the maximum performance improvement
6014             from additional section caching, setting
6015             <span class="command"><strong>additional-from-cache</strong></span>
6016             to <span class="command"><strong>no</strong></span> is recommended, since the current
6017             implementation of <span class="command"><strong>acache</strong></span>
6018             does not short-cut of additional section information from the
6019             DNS cache data.
6020           </p>
6021 <p>
6022             One obvious disadvantage of <span class="command"><strong>acache</strong></span> is
6023             that it requires much more
6024             memory for the internal cached data.
6025             Thus, if the response performance does not matter and memory
6026             consumption is much more critical, the
6027             <span class="command"><strong>acache</strong></span> mechanism can be
6028             disabled by setting <span class="command"><strong>acache-enable</strong></span> to
6029             <span class="command"><strong>no</strong></span>.
6030             It is also possible to specify the upper limit of memory
6031             consumption
6032             for acache by using <span class="command"><strong>max-acache-size</strong></span>.
6033           </p>
6034 <p>
6035             Additional section caching also has a minor effect on the
6036             RRset ordering in the additional section.
6037             Without <span class="command"><strong>acache</strong></span>,
6038             <span class="command"><strong>cyclic</strong></span> order is effective for the additional
6039             section as well as the answer and authority sections.
6040             However, additional section caching fixes the ordering when it
6041             first caches an RRset for the additional section, and the same
6042             ordering will be kept in succeeding responses, regardless of the
6043             setting of <span class="command"><strong>rrset-order</strong></span>.
6044             The effect of this should be minor, however, since an
6045             RRset in the additional section
6046             typically only contains a small number of RRs (and in many cases
6047             it only contains a single RR), in which case the
6048             ordering does not matter much.
6049           </p>
6050 <p>
6051             The following is a summary of options related to
6052             <span class="command"><strong>acache</strong></span>.
6053           </p>
6054 <div class="variablelist"><dl class="variablelist">
6055 <dt><span class="term"><span class="command"><strong>acache-enable</strong></span></span></dt>
6056 <dd><p>
6057                   If <span class="command"><strong>yes</strong></span>, additional section caching is
6058                   enabled.  The default value is <span class="command"><strong>no</strong></span>.
6059                 </p></dd>
6060 <dt><span class="term"><span class="command"><strong>acache-cleaning-interval</strong></span></span></dt>
6061 <dd><p>
6062                   The server will remove stale cache entries, based on an LRU
6063                   based
6064                   algorithm, every <span class="command"><strong>acache-cleaning-interval</strong></span> minutes.
6065                   The default is 60 minutes.
6066                   If set to 0, no periodic cleaning will occur.
6067                 </p></dd>
6068 <dt><span class="term"><span class="command"><strong>max-acache-size</strong></span></span></dt>
6069 <dd><p>
6070                   The maximum amount of memory in bytes to use for the server's acache.
6071                   When the amount of data in the acache reaches this limit,
6072                   the server
6073                   will clean more aggressively so that the limit is not
6074                   exceeded.
6075                   In a server with multiple views, the limit applies
6076                   separately to the
6077                   acache of each view.
6078                   The default is <code class="literal">16M</code>.
6079                 </p></dd>
6080 </dl></div>
6081 </div>
6082 <div class="section">
6083 <div class="titlepage"><div><div><h4 class="title">
6084 <a name="content_filtering"></a>Content Filtering</h4></div></div></div>
6085 <p>
6086             <acronym class="acronym">BIND</acronym> 9 provides the ability to filter
6087             out DNS responses from external DNS servers containing
6088             certain types of data in the answer section.
6089             Specifically, it can reject address (A or AAAA) records if
6090             the corresponding IPv4 or IPv6 addresses match the given
6091             <code class="varname">address_match_list</code> of the
6092             <span class="command"><strong>deny-answer-addresses</strong></span> option.
6093             It can also reject CNAME or DNAME records if the "alias"
6094             name (i.e., the CNAME alias or the substituted query name
6095             due to DNAME) matches the
6096             given <code class="varname">namelist</code> of the
6097             <span class="command"><strong>deny-answer-aliases</strong></span> option, where
6098             "match" means the alias name is a subdomain of one of
6099             the <code class="varname">name_list</code> elements.
6100             If the optional <code class="varname">namelist</code> is specified
6101             with <span class="command"><strong>except-from</strong></span>, records whose query name
6102             matches the list will be accepted regardless of the filter
6103             setting.
6104             Likewise, if the alias name is a subdomain of the
6105             corresponding zone, the <span class="command"><strong>deny-answer-aliases</strong></span>
6106             filter will not apply;
6107             for example, even if "example.com" is specified for
6108             <span class="command"><strong>deny-answer-aliases</strong></span>,
6109           </p>
6110 <pre class="programlisting">www.example.com. CNAME xxx.example.com.</pre>
6111 <p>
6112             returned by an "example.com" server will be accepted.
6113           </p>
6114 <p>
6115             In the <code class="varname">address_match_list</code> of the
6116             <span class="command"><strong>deny-answer-addresses</strong></span> option, only
6117             <code class="varname">ip_addr</code>
6118             and <code class="varname">ip_prefix</code>
6119             are meaningful;
6120             any <code class="varname">key_id</code> will be silently ignored.
6121           </p>
6122 <p>
6123             If a response message is rejected due to the filtering,
6124             the entire message is discarded without being cached, and
6125             a SERVFAIL error will be returned to the client.
6126           </p>
6127 <p>
6128             This filtering is intended to prevent "DNS rebinding attacks," in
6129             which an attacker, in response to a query for a domain name the
6130             attacker controls, returns an IP address within your own network or
6131             an alias name within your own domain.
6132             A naive web browser or script could then serve as an
6133             unintended proxy, allowing the attacker
6134             to get access to an internal node of your local network
6135             that couldn't be externally accessed otherwise.
6136             See the paper available at
6137             <a class="link" href="http://portal.acm.org/citation.cfm?id=1315245.1315298" target="_top">
6138             http://portal.acm.org/citation.cfm?id=1315245.1315298
6139             </a>
6140             for more details about the attacks.
6141           </p>
6142 <p>
6143             For example, if you own a domain named "example.net" and
6144             your internal network uses an IPv4 prefix 192.0.2.0/24,
6145             you might specify the following rules:
6146           </p>
6147 <pre class="programlisting">deny-answer-addresses { 192.0.2.0/24; } except-from { "example.net"; };
6148 deny-answer-aliases { "example.net"; };
6149 </pre>
6150 <p>
6151             If an external attacker lets a web browser in your local
6152             network look up an IPv4 address of "attacker.example.com",
6153             the attacker's DNS server would return a response like this:
6154           </p>
6155 <pre class="programlisting">attacker.example.com. A 192.0.2.1</pre>
6156 <p>
6157             in the answer section.
6158             Since the rdata of this record (the IPv4 address) matches
6159             the specified prefix 192.0.2.0/24, this response will be
6160             ignored.
6161           </p>
6162 <p>
6163             On the other hand, if the browser looks up a legitimate
6164             internal web server "www.example.net" and the
6165             following response is returned to
6166             the <acronym class="acronym">BIND</acronym> 9 server
6167           </p>
6168 <pre class="programlisting">www.example.net. A 192.0.2.2</pre>
6169 <p>
6170             it will be accepted since the owner name "www.example.net"
6171             matches the <span class="command"><strong>except-from</strong></span> element,
6172             "example.net".
6173           </p>
6174 <p>
6175             Note that this is not really an attack on the DNS per se.
6176             In fact, there is nothing wrong for an "external" name to
6177             be mapped to your "internal" IP address or domain name
6178             from the DNS point of view.
6179             It might actually be provided for a legitimate purpose,
6180             such as for debugging.
6181             As long as the mapping is provided by the correct owner,
6182             it is not possible or does not make sense to detect
6183             whether the intent of the mapping is legitimate or not
6184             within the DNS.
6185             The "rebinding" attack must primarily be protected at the
6186             application that uses the DNS.
6187             For a large site, however, it may be difficult to protect
6188             all possible applications at once.
6189             This filtering feature is provided only to help such an
6190             operational environment;
6191             it is generally discouraged to turn it on unless you are
6192             very sure you have no other choice and the attack is a
6193             real threat for your applications.
6194           </p>
6195 <p>
6196             Care should be particularly taken if you want to use this
6197             option for addresses within 127.0.0.0/8.
6198             These addresses are obviously "internal", but many
6199             applications conventionally rely on a DNS mapping from
6200             some name to such an address.
6201             Filtering out DNS records containing this address
6202             spuriously can break such applications.
6203           </p>
6204 </div>
6205 <div class="section">
6206 <div class="titlepage"><div><div><h4 class="title">
6207 <a name="rpz"></a>Response Policy Zone (RPZ) Rewriting</h4></div></div></div>
6208 <p>
6209             <acronym class="acronym">BIND</acronym> 9 includes a limited
6210             mechanism to modify DNS responses for requests
6211             analogous to email anti-spam DNS blacklists.
6212             Responses can be changed to deny the existence of domains (NXDOMAIN),
6213             deny the existence of IP addresses for domains (NODATA),
6214             or contain other IP addresses or data.
6215           </p>
6216 <p>
6217             Response policy zones are named in the
6218             <span class="command"><strong>response-policy</strong></span> option for the view or among the
6219             global options if there is no response-policy option for the view.
6220             RPZs are ordinary DNS zones containing RRsets
6221             that can be queried normally if allowed.
6222             It is usually best to restrict those queries with something like
6223             <span class="command"><strong>allow-query { localhost; };</strong></span>.
6224           </p>
6225 <p>
6226             Four policy triggers are encoded in RPZ records, QNAME, IP, NSIP,
6227             and NSDNAME.
6228             QNAME RPZ records triggered by query names of requests and targets
6229             of CNAME records resolved to generate the response.
6230             The owner name of a QNAME RPZ record is the query name relativized
6231             to the RPZ.
6232           </p>
6233 <p>
6234             The second kind of RPZ trigger is an IP address in an A and AAAA
6235             record in the ANSWER section of a response.
6236             IP address triggers are encoded in records that have owner names
6237             that are subdomains of <strong class="userinput"><code>rpz-ip</code></strong> relativized
6238             to the RPZ origin name and encode an IP address or address block.
6239             IPv4 trigger addresses are represented as
6240             <strong class="userinput"><code>prefixlength.B4.B3.B2.B1.rpz-ip</code></strong>.
6241             The prefix length must be between 1 and 32.
6242             All four bytes, B4, B3, B2, and B1, must be present.
6243             B4 is the decimal value of the least significant byte of the
6244             IPv4 address as in IN-ADDR.ARPA.
6245             IPv6 addresses are encoded in a format similar to the standard
6246             IPv6 text representation,
6247             <strong class="userinput"><code>prefixlength.W8.W7.W6.W5.W4.W3.W2.W1.rpz-ip</code></strong>.
6248             Each of W8,...,W1 is a one to four digit hexadecimal number
6249             representing 16 bits of the IPv6 address as in the standard text
6250             representation of IPv6 addresses, but reversed as in IN-ADDR.ARPA.
6251             All 8 words must be present except when consecutive
6252             zero words are replaced with <strong class="userinput"><code>.zz.</code></strong>
6253             analogous to double colons (::) in standard IPv6 text encodings.
6254             The prefix length must be between 1 and 128.
6255           </p>
6256 <p>
6257             NSDNAME triggers match names of authoritative servers
6258             for the query name, a parent of the query name, a CNAME for
6259             query name, or a parent of a CNAME.
6260             They are encoded as subdomains of
6261             <strong class="userinput"><code>rpz-nsdomain</code></strong> relativized
6262             to the RPZ origin name.
6263             NSIP triggers match IP addresses in A and
6264             AAAA RRsets for domains that can be checked against NSDNAME
6265             policy records.
6266             NSIP triggers are encoded like IP triggers except as subdomains of
6267             <strong class="userinput"><code>rpz-nsip</code></strong>.
6268             NSDNAME and NSIP triggers are checked only for names with at
6269             least <span class="command"><strong>min-ns-dots</strong></span> dots.
6270             The default value of <span class="command"><strong>min-ns-dots</strong></span> is 1 to
6271             exclude top level domains.
6272           </p>
6273 <p>
6274             The query response is checked against all RPZs, so
6275             two or more policy records can be triggered by a response.
6276             Because DNS responses can be rewritten according to at most one
6277             policy record, a single record encoding an action (other than
6278             <span class="command"><strong>DISABLED</strong></span> actions) must be chosen.
6279             Triggers or the records that encode them are chosen in
6280             the following order:
6281             </p>
6282 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
6283 <li class="listitem">Choose the triggered record in the zone that appears
6284                 first in the response-policy option.
6285               </li>
6286 <li class="listitem">Prefer QNAME to IP to NSDNAME to NSIP triggers
6287                 in a single zone.
6288               </li>
6289 <li class="listitem">Among NSDNAME triggers, prefer the
6290                 trigger that matches the smallest name under the DNSSEC ordering.
6291               </li>
6292 <li class="listitem">Among IP or NSIP triggers, prefer the trigger
6293                 with the longest prefix.
6294               </li>
6295 <li class="listitem">Among triggers with the same prefix length,
6296                 prefer the IP or NSIP trigger that matches
6297                 the smallest IP address.
6298               </li>
6299 </ul></div>
6300 <p>
6301           </p>
6302 <p>
6303             When the processing of a response is restarted to resolve
6304             DNAME or CNAME records and a policy record set has
6305             not been triggered,
6306             all RPZs are again consulted for the DNAME or CNAME names
6307             and addresses.
6308           </p>
6309 <p>
6310             RPZ record sets are sets of any types of DNS record except
6311             DNAME or DNSSEC that encode actions or responses to queries.
6312             </p>
6313 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
6314 <li class="listitem">The <span class="command"><strong>NXDOMAIN</strong></span> response is encoded
6315                 by a CNAME whose target is the root domain (.)
6316               </li>
6317 <li class="listitem">A CNAME whose target is the wildcard top-level
6318                 domain (*.) specifies the <span class="command"><strong>NODATA</strong></span> action,
6319                 which rewrites the response to NODATA or ANCOUNT=1.
6320               </li>
6321 <li class="listitem">The <span class="command"><strong>Local Data</strong></span> action is
6322                 represented by a set ordinary DNS records that are used
6323                 to answer queries.  Queries for record types not the
6324                 set are answered with NODATA.
6325
6326                 A special form of local data is a CNAME whose target is a
6327                 wildcard such as *.example.com.
6328                 It is used as if were an ordinary CNAME after the astrisk (*)
6329                 has been replaced with the query name.
6330                 The purpose for this special form is query logging in the
6331                 walled garden's authority DNS server.
6332               </li>
6333 <li class="listitem">The <span class="command"><strong>PASSTHRU</strong></span> policy is specified
6334                 by a CNAME whose target is <span class="command"><strong>rpz-passthru.</strong></span>
6335                 It causes the response to not be rewritten
6336                 and is most often used to "poke holes" in policies for
6337                 CIDR blocks.
6338                 (A CNAME whose target is the variable part of its owner name
6339                 is an obsolete specification of the PASSTHRU policy.)
6340               </li>
6341 </ul></div>
6342 <p>
6343           </p>
6344 <p>
6345             The actions specified in an RPZ can be overridden with a
6346             <span class="command"><strong>policy</strong></span> clause in the
6347             <span class="command"><strong>response-policy</strong></span> option.
6348             An organization using an RPZ provided by another organization might
6349             use this mechanism to redirect domains to its own walled garden.
6350             </p>
6351 <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
6352 <li class="listitem">
6353 <span class="command"><strong>GIVEN</strong></span> says "do not override but
6354                 perform the action specified in the zone."
6355               </li>
6356 <li class="listitem">
6357 <span class="command"><strong>DISABLED</strong></span> causes policy records to do
6358                 nothing but log what they might have done.
6359                 The response to the DNS query will be written according to
6360                 any triggered policy records that are not disabled.
6361                 Disabled policy zones should appear first,
6362                 because they will often not be logged
6363                 if a higher precedence trigger is found first.
6364               </li>
6365 <li class="listitem">
6366 <span class="command"><strong>PASSTHRU</strong></span> causes all policy records
6367                 to act as if they were CNAME records with targets the variable
6368                 part of their owner name.  They protect the response from
6369                 being changed.
6370               </li>
6371 <li class="listitem">
6372 <span class="command"><strong>NXDOMAIN</strong></span> causes all RPZ records
6373                 to specify NXDOMAIN policies.
6374               </li>
6375 <li class="listitem">
6376 <span class="command"><strong>NODATA</strong></span> overrides with the
6377                 NODATA policy
6378               </li>
6379 <li class="listitem">
6380 <span class="command"><strong>CNAME domain</strong></span> causes all RPZ
6381                 policy records to act as if they were "cname domain" records.
6382               </li>
6383 </ul></div>
6384 <p>
6385           </p>
6386 <p>
6387             By default, the actions encoded in an RPZ are applied
6388             only to queries that ask for recursion (RD=1).
6389             That default can be changed for a single RPZ or all RPZs in a view
6390             with a <span class="command"><strong>recursive-only no</strong></span> clause.
6391             This feature is useful for serving the same zone files
6392             both inside and outside an RFC 1918 cloud and using RPZ to
6393             delete answers that would otherwise contain RFC 1918 values
6394             on the externally visible name server or view.
6395           </p>
6396 <p>
6397             Also by default, RPZ actions are applied only to DNS requests that
6398             either do not request DNSSEC metadata (DO=0) or when no DNSSEC
6399             records are available for request name in the original zone (not
6400             the response policy zone).
6401             This default can be changed for all RPZs in a view with a
6402             <span class="command"><strong>break-dnssec yes</strong></span> clause.
6403             In that case, RPZ actions are applied regardless of DNSSEC.
6404             The name of the clause option reflects the fact that results
6405             rewritten by RPZ actions cannot verify.
6406           </p>
6407 <p>
6408             The TTL of a record modified by RPZ policies is set from the
6409             TTL of the relevant record in policy zone.  It is then limited
6410             to a maximum value.
6411             The <span class="command"><strong>max-policy-ttl</strong></span> clause changes that
6412             maximum from its default of 5.
6413           </p>
6414 <p>
6415             For example, you might use this option statement
6416           </p>
6417 <pre class="programlisting">    response-policy { zone "badlist"; };</pre>
6418 <p>
6419             and this zone statement
6420           </p>
6421 <pre class="programlisting">    zone "badlist" {type master; file "master/badlist"; allow-query {none;}; };</pre>
6422 <p>
6423             with this zone file
6424           </p>
6425 <pre class="programlisting">$TTL 1H
6426 @                       SOA LOCALHOST. named-mgr.example.com (1 1h 15m 30d 2h)
6427                         NS  LOCALHOST.
6428
6429 ; QNAME policy records.  There are no periods (.) after the owner names.
6430 nxdomain.domain.com     CNAME   .               ; NXDOMAIN policy
6431 nodata.domain.com       CNAME   *.              ; NODATA policy
6432 bad.domain.com          A       10.0.0.1        ; redirect to a walled garden
6433                         AAAA    2001:2::1
6434
6435 ; do not rewrite (PASSTHRU) OK.DOMAIN.COM
6436 ok.domain.com           CNAME   rpz-passthru.
6437
6438 bzone.domain.com        CNAME   garden.example.com.
6439
6440 ; redirect x.bzone.domain.com to x.bzone.domain.com.garden.example.com
6441 *.bzone.domain.com      CNAME   *.garden.example.com.
6442
6443
6444 ; IP policy records that rewrite all answers for 127/8 except 127.0.0.1
6445 8.0.0.0.127.rpz-ip      CNAME   .
6446 32.1.0.0.127.rpz-ip     CNAME   rpz-passthru.
6447
6448 ; NSDNAME and NSIP policy records
6449 ns.domain.com.rpz-nsdname   CNAME   .
6450 48.zz.2.2001.rpz-nsip       CNAME   .
6451 </pre>
6452 <p>
6453             RPZ can affect server performance.
6454             Each configured response policy zone requires the server to
6455             perform one to four additional database lookups before a
6456             query can be answered.
6457             For example, a DNS server with four policy zones, each with all
6458             four kinds of response triggers, QNAME, IP, NSIP, and
6459             NSDNAME, requires a total of 17 times as many database
6460             lookups as a similar DNS server with no response policy zones.
6461             A <acronym class="acronym">BIND9</acronym> server with adequate memory and one
6462             response policy zone with QNAME and IP triggers might achieve a
6463             maximum queries-per-second rate about 20% lower.
6464             A server with four response policy zones with QNAME and IP
6465             triggers might have a maximum QPS rate about 50% lower.
6466           </p>
6467 <p>
6468             Responses rewritten by RPZ are counted in the
6469             <span class="command"><strong>RPZRewrites</strong></span> statistics.
6470           </p>
6471 </div>
6472 <div class="section">
6473 <div class="titlepage"><div><div><h4 class="title">
6474 <a name="rrl"></a>Response Rate Limiting</h4></div></div></div>
6475 <p>
6476             This feature is only available when <acronym class="acronym">BIND</acronym> 9
6477             is compiled with the <strong class="userinput"><code>--enable-rrl</code></strong>
6478             option on the "configure" command line.
6479           </p>
6480 <p>
6481             Excessive almost identical UDP <span class="emphasis"><em>responses</em></span>
6482             can be controlled by configuring a
6483             <span class="command"><strong>rate-limit</strong></span> clause in an
6484             <span class="command"><strong>options</strong></span> or <span class="command"><strong>view</strong></span> statement.
6485             This mechanism keeps authoritative BIND 9 from being used
6486             in amplifying reflection denial of service (DoS) attacks.
6487             Short truncated (TC=1) responses can be sent to provide
6488             rate-limited responses to legitimate clients within
6489             a range of forged, attacked IP addresses.
6490             Legitimate clients react to dropped or truncated response
6491             by retrying with UDP or with TCP respectively.
6492           </p>
6493 <p>
6494             This mechanism is intended for authoritative DNS servers.
6495             It can be used on recursive servers but can slow
6496             applications such as SMTP servers (mail receivers) and
6497             HTTP clients (web browsers) that repeatedly request the
6498             same domains.
6499             When possible, closing "open" recursive servers is better.
6500           </p>
6501 <p>
6502             Response rate limiting uses a "credit" or "token bucket" scheme.
6503             Each combination of identical response and client
6504             has a conceptual account that earns a specified number
6505             of credits every second.
6506             A prospective response debits its account by one.
6507             Responses are dropped or truncated
6508             while the account is negative.
6509             Responses are tracked within a rolling window of time
6510             which defaults to 15 seconds, but can be configured with
6511             the <span class="command"><strong>window</strong></span> option to any value from
6512             1 to 3600 seconds (1 hour).
6513             The account cannot become more positive than
6514             the per-second limit
6515             or more negative than <span class="command"><strong>window</strong></span>
6516             times the per-second limit.
6517             When the specified number of credits for a class of
6518             responses is set to 0, those responses are not rate limited.
6519           </p>
6520 <p>
6521             The notions of "identical response" and "DNS client"
6522             for rate limiting are not simplistic.
6523             All responses to an address block are counted as if to a
6524             single client.
6525             The prefix lengths of addresses blocks are
6526             specified with <span class="command"><strong>ipv4-prefix-length</strong></span> (default 24)
6527             and <span class="command"><strong>ipv6-prefix-length</strong></span> (default 56).
6528           </p>
6529 <p>
6530             All non-empty responses for a valid domain name (qname)
6531             and record type (qtype) are identical and have a limit specified
6532             with <span class="command"><strong>responses-per-second</strong></span>
6533             (default 0 or no limit).
6534             All empty (NODATA) responses for a valid domain,
6535             regardless of query type, are identical.
6536             Responses in the NODATA class are limited by
6537             <span class="command"><strong>nodata-per-second</strong></span>
6538             (default <span class="command"><strong>responses-per-second</strong></span>).
6539             Requests for any and all undefined subdomains of a given
6540             valid domain result in NXDOMAIN errors, and are identical
6541             regardless of query type.
6542             They are limited by <span class="command"><strong>nxdomain-per-second</strong></span>
6543             (default <span class="command"><strong>responses-per-second</strong></span>).
6544             This controls some attacks using random names, but
6545             can be relaxed or turned off (set to 0)
6546             on servers that expect many legitimate
6547             NXDOMAIN responses, such as from anti-spam blacklists.
6548             Referrals or delegations to the server of a given
6549             domain are identical and are limited by
6550             <span class="command"><strong>referrals-per-second</strong></span>
6551             (default <span class="command"><strong>responses-per-second</strong></span>).
6552           </p>
6553 <p>
6554             Responses generated from local wildcards are counted and limited
6555             as if they were for the parent domain name.
6556             This controls flooding using random.wild.example.com.
6557           </p>
6558 <p>
6559             All requests that result in DNS errors other
6560             than NXDOMAIN, such as SERVFAIL and FORMERR, are identical
6561             regardless of requested name (qname) or record type (qtype).
6562             This controls attacks using invalid requests or distant,
6563             broken authoritative servers.
6564             By default the limit on errors is the same as the
6565             <span class="command"><strong>responses-per-second</strong></span> value,
6566             but it can be set separately with
6567             <span class="command"><strong>errors-per-second</strong></span>.
6568           </p>
6569 <p>
6570             Many attacks using DNS involve UDP requests with forged source
6571             addresses.
6572             Rate limiting prevents the use of BIND 9 to flood a network
6573             with responses to requests with forged source addresses,
6574             but could let a third party block responses to legitimate requests.
6575             There is a mechanism that can answer some legitimate
6576             requests from a client whose address is being forged in a flood.
6577             Setting <span class="command"><strong>slip</strong></span> to 2 (its default) causes every
6578             other UDP request to be answered with a small truncated (TC=1)
6579             response.
6580             The small size and reduced frequency, and so lack of
6581             amplification, of "slipped" responses make them unattractive
6582             for reflection DoS attacks.
6583             <span class="command"><strong>slip</strong></span> must be between 0 and 10.
6584             A value of 0 does not "slip":
6585             no truncated responses are sent due to rate limiting,
6586             all responses are dropped.
6587             A value of 1 causes every response to slip;
6588             values between 2 and 10 cause every n'th response to slip.
6589             Some error responses including REFUSED and SERVFAIL
6590             cannot be replaced with truncated responses and are instead
6591             leaked at the <span class="command"><strong>slip</strong></span> rate.
6592           </p>
6593 <p>
6594             (NOTE: Dropped responses from an authoritative server may
6595             reduce the difficulty of a third party successfully forging
6596             a response to a recursive resolver. The best security
6597             against forged responses is for authoritative operators
6598             to sign their zones using DNSSEC and for resolver operators
6599             to validate the responses. When this is not an option,
6600             operators who are more concerned with response integrity
6601             than with flood mitigation may consider setting
6602             <span class="command"><strong>slip</strong></span> to 1, causing all rate-limited
6603             responses to be truncated rather than dropped.  This reduces
6604             the effectiveness of rate-limiting against reflection attacks.)
6605           </p>
6606 <p>
6607             When the approximate query per second rate exceeds
6608             the <span class="command"><strong>qps-scale</strong></span> value,
6609             then the <span class="command"><strong>responses-per-second</strong></span>,
6610             <span class="command"><strong>errors-per-second</strong></span>,
6611             <span class="command"><strong>nxdomains-per-second</strong></span> and
6612             <span class="command"><strong>all-per-second</strong></span> values are reduced by the
6613             ratio of the current rate to the <span class="command"><strong>qps-scale</strong></span> value.
6614             This feature can tighten defenses during attacks.
6615             For example, with
6616             <span class="command"><strong>qps-scale 250; responses-per-second 20;</strong></span> and
6617             a total query rate of 1000 queries/second for all queries from
6618             all DNS clients including via TCP,
6619             then the effective responses/second limit changes to
6620             (250/1000)*20 or 5.
6621             Responses sent via TCP are not limited
6622             but are counted to compute the query per second rate.
6623           </p>
6624 <p>
6625             Communities of DNS clients can be given their own parameters or no
6626             rate limiting by putting
6627             <span class="command"><strong>rate-limit</strong></span> statements in <span class="command"><strong>view</strong></span>
6628             statements instead of the global <span class="command"><strong>option</strong></span>
6629             statement.
6630             A <span class="command"><strong>rate-limit</strong></span> statement in a view replaces,
6631             rather than supplementing, a <span class="command"><strong>rate-limit</strong></span>
6632             statement among the main options.
6633             DNS clients within a view can be exempted from rate limits
6634             with the <span class="command"><strong>exempt-clients</strong></span> clause.
6635           </p>
6636 <p>
6637             UDP responses of all kinds can be limited with the
6638             <span class="command"><strong>all-per-second</strong></span> phrase.
6639             This rate limiting is unlike the rate limiting provided by
6640             <span class="command"><strong>responses-per-second</strong></span>,
6641             <span class="command"><strong>errors-per-second</strong></span>, and
6642             <span class="command"><strong>nxdomains-per-second</strong></span> on a DNS server
6643             which are often invisible to the victim of a DNS reflection attack.
6644             Unless the forged requests of the attack are the same as the
6645             legitimate requests of the victim, the victim's requests are
6646             not affected.
6647             Responses affected by an <span class="command"><strong>all-per-second</strong></span> limit
6648             are always dropped; the <span class="command"><strong>slip</strong></span> value has no
6649             effect.
6650             An <span class="command"><strong>all-per-second</strong></span> limit should be
6651             at least 4 times as large as the other limits,
6652             because single DNS clients often send bursts of legitimate
6653             requests.
6654             For example, the receipt of a single mail message can prompt
6655             requests from an SMTP server for NS, PTR, A, and AAAA records
6656             as the incoming SMTP/TCP/IP connection is considered.
6657             The SMTP server can need additional NS, A, AAAA, MX, TXT, and SPF
6658             records as it considers the STMP <span class="command"><strong>Mail From</strong></span>
6659             command.
6660             Web browsers often repeatedly resolve the same names that
6661             are repeated in HTML &lt;IMG&gt; tags in a page.
6662             <span class="command"><strong>All-per-second</strong></span> is similar to the
6663             rate limiting offered by firewalls but often inferior.
6664             Attacks that justify ignoring the
6665             contents of DNS responses are likely to be attacks on the
6666             DNS server itself.
6667             They usually should be discarded before the DNS server
6668             spends resources making TCP connections or parsing DNS requests,
6669             but that rate limiting must be done before the
6670             DNS server sees the requests.
6671           </p>
6672 <p>
6673             The maximum size of the table used to track requests and
6674             rate limit responses is set with <span class="command"><strong>max-table-size</strong></span>.
6675             Each entry in the table is between 40 and 80 bytes.
6676             The table needs approximately as many entries as the number
6677             of requests received per second.
6678             The default is 20,000.
6679             To reduce the cold start of growing the table,
6680             <span class="command"><strong>min-table-size</strong></span> (default 500)
6681             can set the minimum table size.
6682             Enable <span class="command"><strong>rate-limit</strong></span> category logging to monitor
6683             expansions of the table and inform
6684             choices for the initial and maximum table size.
6685           </p>
6686 <p>
6687             Use <span class="command"><strong>log-only yes</strong></span> to test rate limiting parameters
6688             without actually dropping any requests.
6689           </p>
6690 <p>
6691             Responses dropped by rate limits are included in the
6692             <span class="command"><strong>RateDropped</strong></span> and <span class="command"><strong>QryDropped</strong></span>
6693             statistics.
6694             Responses that truncated by rate limits are included in
6695             <span class="command"><strong>RateSlipped</strong></span> and <span class="command"><strong>RespTruncated</strong></span>.
6696           </p>
6697 </div>
6698 </div>
6699 <div class="section">
6700 <div class="titlepage"><div><div><h3 class="title">
6701 <a name="server_statement_grammar"></a><span class="command"><strong>server</strong></span> Statement Grammar</h3></div></div></div>
6702 <pre class="programlisting"><span class="command"><strong>server</strong></span> <em class="replaceable"><code>ip_addr[/prefixlen]</code></em> {
6703     [<span class="optional"> bogus <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6704     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6705     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6706     [<span class="optional"> request-nsid <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6707     [<span class="optional"> edns <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6708     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
6709     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
6710     [<span class="optional"> transfers <em class="replaceable"><code>number</code></em> ; </span>]
6711     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em> ; ]</span>]
6712     [<span class="optional"> keys { <em class="replaceable"><code>key_id</code></em> }; </span>]
6713     [<span class="optional"> transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6714     [<span class="optional"> transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6715     [<span class="optional"> notify-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6716     [<span class="optional"> notify-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6717     [<span class="optional"> query-source [<span class="optional"> address ( <em class="replaceable"><code>ip_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
6718                   [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]; </span>]
6719     [<span class="optional"> query-source-v6 [<span class="optional"> address ( <em class="replaceable"><code>ip_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
6720                      [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]; </span>]
6721     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6722     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
6723     [<span class="optional"> queryport-pool-updateinterval <em class="replaceable"><code>number</code></em>; </span>]
6724 };
6725 </pre>
6726 </div>
6727 <div class="section">
6728 <div class="titlepage"><div><div><h3 class="title">
6729 <a name="server_statement_definition_and_usage"></a><span class="command"><strong>server</strong></span> Statement Definition and
6730             Usage</h3></div></div></div>
6731 <p>
6732             The <span class="command"><strong>server</strong></span> statement defines
6733             characteristics
6734             to be associated with a remote name server.  If a prefix length is
6735             specified, then a range of servers is covered.  Only the most
6736             specific
6737             server clause applies regardless of the order in
6738             <code class="filename">named.conf</code>.
6739           </p>
6740 <p>
6741             The <span class="command"><strong>server</strong></span> statement can occur at
6742             the top level of the
6743             configuration file or inside a <span class="command"><strong>view</strong></span>
6744             statement.
6745             If a <span class="command"><strong>view</strong></span> statement contains
6746             one or more <span class="command"><strong>server</strong></span> statements, only
6747             those
6748             apply to the view and any top-level ones are ignored.
6749             If a view contains no <span class="command"><strong>server</strong></span>
6750             statements,
6751             any top-level <span class="command"><strong>server</strong></span> statements are
6752             used as
6753             defaults.
6754           </p>
6755 <p>
6756             If you discover that a remote server is giving out bad data,
6757             marking it as bogus will prevent further queries to it. The
6758             default
6759             value of <span class="command"><strong>bogus</strong></span> is <span class="command"><strong>no</strong></span>.
6760           </p>
6761 <p>
6762             The <span class="command"><strong>provide-ixfr</strong></span> clause determines
6763             whether
6764             the local server, acting as master, will respond with an
6765             incremental
6766             zone transfer when the given remote server, a slave, requests it.
6767             If set to <span class="command"><strong>yes</strong></span>, incremental transfer
6768             will be provided
6769             whenever possible. If set to <span class="command"><strong>no</strong></span>,
6770             all transfers
6771             to the remote server will be non-incremental. If not set, the
6772             value
6773             of the <span class="command"><strong>provide-ixfr</strong></span> option in the
6774             view or
6775             global options block is used as a default.
6776           </p>
6777 <p>
6778             The <span class="command"><strong>request-ixfr</strong></span> clause determines
6779             whether
6780             the local server, acting as a slave, will request incremental zone
6781             transfers from the given remote server, a master. If not set, the
6782             value of the <span class="command"><strong>request-ixfr</strong></span> option in
6783             the view or global options block is used as a default. It may
6784             also be set in the zone block and, if set there, it will
6785             override the global or view setting for that zone.
6786           </p>
6787 <p>
6788             IXFR requests to servers that do not support IXFR will
6789             automatically
6790             fall back to AXFR.  Therefore, there is no need to manually list
6791             which servers support IXFR and which ones do not; the global
6792             default
6793             of <span class="command"><strong>yes</strong></span> should always work.
6794             The purpose of the <span class="command"><strong>provide-ixfr</strong></span> and
6795             <span class="command"><strong>request-ixfr</strong></span> clauses is
6796             to make it possible to disable the use of IXFR even when both
6797             master
6798             and slave claim to support it, for example if one of the servers
6799             is buggy and crashes or corrupts data when IXFR is used.
6800           </p>
6801 <p>
6802             The <span class="command"><strong>edns</strong></span> clause determines whether
6803             the local server will attempt to use EDNS when communicating
6804             with the remote server.  The default is <span class="command"><strong>yes</strong></span>.
6805           </p>
6806 <p>
6807             The <span class="command"><strong>edns-udp-size</strong></span> option sets the EDNS UDP size
6808             that is advertised by <span class="command"><strong>named</strong></span> when querying the remote server.
6809             Valid values are 512 to 4096 bytes (values outside this range will be
6810             silently adjusted).  This option is useful when you wish to
6811             advertises a different value to this server than the value you
6812             advertise globally, for example, when there is a firewall at the
6813             remote site that is blocking large replies.
6814           </p>
6815 <p>
6816             The <span class="command"><strong>max-udp-size</strong></span> option sets the
6817             maximum EDNS UDP message size <span class="command"><strong>named</strong></span> will send.  Valid
6818             values are 512 to 4096 bytes (values outside this range will
6819             be silently adjusted).  This option is useful when you
6820             know that there is a firewall that is blocking large
6821             replies from <span class="command"><strong>named</strong></span>.
6822           </p>
6823 <p>
6824             The server supports two zone transfer methods. The first, <span class="command"><strong>one-answer</strong></span>,
6825             uses one DNS message per resource record transferred. <span class="command"><strong>many-answers</strong></span> packs
6826             as many resource records as possible into a message. <span class="command"><strong>many-answers</strong></span> is
6827             more efficient, but is only known to be understood by <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
6828             8.x, and patched versions of <acronym class="acronym">BIND</acronym>
6829             4.9.5. You can specify which method
6830             to use for a server with the <span class="command"><strong>transfer-format</strong></span> option.
6831             If <span class="command"><strong>transfer-format</strong></span> is not
6832             specified, the <span class="command"><strong>transfer-format</strong></span>
6833             specified
6834             by the <span class="command"><strong>options</strong></span> statement will be
6835             used.
6836           </p>
6837 <p><span class="command"><strong>transfers</strong></span>
6838             is used to limit the number of concurrent inbound zone
6839             transfers from the specified server. If no
6840             <span class="command"><strong>transfers</strong></span> clause is specified, the
6841             limit is set according to the
6842             <span class="command"><strong>transfers-per-ns</strong></span> option.
6843           </p>
6844 <p>
6845             The <span class="command"><strong>keys</strong></span> clause identifies a
6846             <span class="command"><strong>key_id</strong></span> defined by the <span class="command"><strong>key</strong></span> statement,
6847             to be used for transaction security (TSIG, <a class="xref" href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
6848             when talking to the remote server.
6849             When a request is sent to the remote server, a request signature
6850             will be generated using the key specified here and appended to the
6851             message. A request originating from the remote server is not
6852             required
6853             to be signed by this key.
6854           </p>
6855 <p>
6856             Only a single key per server is currently supported.
6857           </p>
6858 <p>
6859             The <span class="command"><strong>transfer-source</strong></span> and
6860             <span class="command"><strong>transfer-source-v6</strong></span> clauses specify
6861             the IPv4 and IPv6 source
6862             address to be used for zone transfer with the remote server,
6863             respectively.
6864             For an IPv4 remote server, only <span class="command"><strong>transfer-source</strong></span> can
6865             be specified.
6866             Similarly, for an IPv6 remote server, only
6867             <span class="command"><strong>transfer-source-v6</strong></span> can be
6868             specified.
6869             For more details, see the description of
6870             <span class="command"><strong>transfer-source</strong></span> and
6871             <span class="command"><strong>transfer-source-v6</strong></span> in
6872             <a class="xref" href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
6873           </p>
6874 <p>
6875             The <span class="command"><strong>notify-source</strong></span> and
6876             <span class="command"><strong>notify-source-v6</strong></span> clauses specify the
6877             IPv4 and IPv6 source address to be used for notify
6878             messages sent to remote servers, respectively.  For an
6879             IPv4 remote server, only <span class="command"><strong>notify-source</strong></span>
6880             can be specified.  Similarly, for an IPv6 remote server,
6881             only <span class="command"><strong>notify-source-v6</strong></span> can be specified.
6882           </p>
6883 <p>
6884             The <span class="command"><strong>query-source</strong></span> and
6885             <span class="command"><strong>query-source-v6</strong></span> clauses specify the
6886             IPv4 and IPv6 source address to be used for queries
6887             sent to remote servers, respectively.  For an IPv4
6888             remote server, only <span class="command"><strong>query-source</strong></span> can
6889             be specified.  Similarly, for an IPv6 remote server,
6890             only <span class="command"><strong>query-source-v6</strong></span> can be specified.
6891           </p>
6892 <p>
6893             The <span class="command"><strong>request-nsid</strong></span> clause determines
6894             whether the local server will add a NSID EDNS option
6895             to requests sent to the server.  This overrides
6896             <span class="command"><strong>request-nsid</strong></span> set at the view or
6897             option level.
6898           </p>
6899 </div>
6900 <div class="section">
6901 <div class="titlepage"><div><div><h3 class="title">
6902 <a name="statschannels"></a><span class="command"><strong>statistics-channels</strong></span> Statement Grammar</h3></div></div></div>
6903 <pre class="programlisting"><span class="command"><strong>statistics-channels</strong></span> {
6904    [ inet ( ip_addr | * ) [ port ip_port ]
6905    [ allow { <em class="replaceable"><code> address_match_list </code></em> } ]; ]
6906    [ inet ...; ]
6907 };
6908 </pre>
6909 </div>
6910 <div class="section">
6911 <div class="titlepage"><div><div><h3 class="title">
6912 <a name="statistics_channels"></a><span class="command"><strong>statistics-channels</strong></span> Statement Definition and
6913             Usage</h3></div></div></div>
6914 <p>
6915           The <span class="command"><strong>statistics-channels</strong></span> statement
6916           declares communication channels to be used by system
6917           administrators to get access to statistics information of
6918           the name server.
6919         </p>
6920 <p>
6921           This statement intends to be flexible to support multiple
6922           communication protocols in the future, but currently only
6923           HTTP access is supported.
6924           It requires that BIND 9 be compiled with libxml2;
6925           the <span class="command"><strong>statistics-channels</strong></span> statement is
6926           still accepted even if it is built without the library,
6927           but any HTTP access will fail with an error.
6928         </p>
6929 <p>
6930           An <span class="command"><strong>inet</strong></span> control channel is a TCP socket
6931           listening at the specified <span class="command"><strong>ip_port</strong></span> on the
6932           specified <span class="command"><strong>ip_addr</strong></span>, which can be an IPv4 or IPv6
6933           address.  An <span class="command"><strong>ip_addr</strong></span> of <code class="literal">*</code> (asterisk) is
6934           interpreted as the IPv4 wildcard address; connections will be
6935           accepted on any of the system's IPv4 addresses.
6936           To listen on the IPv6 wildcard address,
6937           use an <span class="command"><strong>ip_addr</strong></span> of <code class="literal">::</code>.
6938         </p>
6939 <p>
6940           If no port is specified, port 80 is used for HTTP channels.
6941           The asterisk "<code class="literal">*</code>" cannot be used for
6942           <span class="command"><strong>ip_port</strong></span>.
6943         </p>
6944 <p>
6945           The attempt of opening a statistics channel is
6946           restricted by the optional <span class="command"><strong>allow</strong></span> clause.
6947           Connections to the statistics channel are permitted based on the
6948           <span class="command"><strong>address_match_list</strong></span>.
6949           If no <span class="command"><strong>allow</strong></span> clause is present,
6950           <span class="command"><strong>named</strong></span> accepts connection
6951           attempts from any address; since the statistics may
6952           contain sensitive internal information, it is highly
6953           recommended to restrict the source of connection requests
6954           appropriately.
6955         </p>
6956 <p>
6957           If no <span class="command"><strong>statistics-channels</strong></span> statement is present,
6958           <span class="command"><strong>named</strong></span> will not open any communication channels.
6959         </p>
6960 <p>
6961           If the statistics channel is configured to listen on 127.0.0.1
6962           port 8888, then the statistics are accessible in XML format at
6963           <a class="link" href="http://127.0.0.1:8888/" target="_top">http://127.0.0.1:8888/</a> or
6964           <a class="link" href="http://127.0.0.1:8888/xml" target="_top">http://127.0.0.1:8888/xml</a>. A CSS file is
6965           included which can format the XML statistics into tables
6966           when viewed with a stylesheet-capable browser.  When
6967           <acronym class="acronym">BIND</acronym> 9 is configured with --enable-newstats,
6968           a new XML schema is used (version 3) which adds additional
6969           zone statistics and uses a flatter tree for more efficient
6970           parsing.  The stylesheet included uses the Google Charts API
6971           to render data into into charts and graphs when using a
6972           javascript-capable browser.
6973         </p>
6974 <p>
6975           Applications that depend on a particular XML schema
6976           can request
6977           <a class="link" href="http://127.0.0.1:8888/xml/v2" target="_top">http://127.0.0.1:8888/xml/v2</a> for version 2
6978           of the statistics XML schema or
6979           <a class="link" href="http://127.0.0.1:8888/xml/v3" target="_top">http://127.0.0.1:8888/xml/v3</a> for version 3.
6980           If the requested schema is supported by the server, then
6981           it will respond; if not, it will return a "page not found"
6982           error.
6983         </p>
6984 </div>
6985 <div class="section">
6986 <div class="titlepage"><div><div><h3 class="title">
6987 <a name="trusted-keys"></a><span class="command"><strong>trusted-keys</strong></span> Statement Grammar</h3></div></div></div>
6988 <pre class="programlisting"><span class="command"><strong>trusted-keys</strong></span> {
6989     <em class="replaceable"><code>string</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ;
6990     [<span class="optional"> <em class="replaceable"><code>string</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ; [<span class="optional">...</span>]</span>]
6991 };
6992 </pre>
6993 </div>
6994 <div class="section">
6995 <div class="titlepage"><div><div><h3 class="title">
6996 <a name="trusted_keys"></a><span class="command"><strong>trusted-keys</strong></span> Statement Definition
6997             and Usage</h3></div></div></div>
6998 <p>
6999             The <span class="command"><strong>trusted-keys</strong></span> statement defines
7000             DNSSEC security roots. DNSSEC is described in <a class="xref" href="Bv9ARM.ch04.html#DNSSEC" title="DNSSEC">the section called &#8220;DNSSEC&#8221;</a>. A security root is defined when the
7001             public key for a non-authoritative zone is known, but
7002             cannot be securely obtained through DNS, either because
7003             it is the DNS root zone or because its parent zone is
7004             unsigned.  Once a key has been configured as a trusted
7005             key, it is treated as if it had been validated and
7006             proven secure. The resolver attempts DNSSEC validation
7007             on all DNS data in subdomains of a security root.
7008           </p>
7009 <p>
7010             All keys (and corresponding zones) listed in
7011             <span class="command"><strong>trusted-keys</strong></span> are deemed to exist regardless
7012             of what parent zones say.  Similarly for all keys listed in
7013             <span class="command"><strong>trusted-keys</strong></span> only those keys are
7014             used to validate the DNSKEY RRset.  The parent's DS RRset
7015             will not be used.
7016           </p>
7017 <p>
7018             The <span class="command"><strong>trusted-keys</strong></span> statement can contain
7019             multiple key entries, each consisting of the key's
7020             domain name, flags, protocol, algorithm, and the Base-64
7021             representation of the key data.
7022             Spaces, tabs, newlines and carriage returns are ignored
7023             in the key data, so the configuration may be split up into
7024             multiple lines.
7025           </p>
7026 <p>
7027             <span class="command"><strong>trusted-keys</strong></span> may be set at the top level
7028             of <code class="filename">named.conf</code> or within a view.  If it is
7029             set in both places, they are additive: keys defined at the top
7030             level are inherited by all views, but keys defined in a view
7031             are only used within that view.
7032           </p>
7033 </div>
7034 <div class="section">
7035 <div class="titlepage"><div><div><h3 class="title">
7036 <a name="managed_keys"></a><span class="command"><strong>managed-keys</strong></span> Statement Grammar</h3></div></div></div>
7037 <pre class="programlisting"><span class="command"><strong>managed-keys</strong></span> {
7038     <em class="replaceable"><code>name</code></em> initial-key <em class="replaceable"><code>flags</code></em> <em class="replaceable"><code>protocol</code></em> <em class="replaceable"><code>algorithm</code></em> <em class="replaceable"><code>key-data</code></em> ;
7039     [<span class="optional"> <em class="replaceable"><code>name</code></em> initial-key <em class="replaceable"><code>flags</code></em> <em class="replaceable"><code>protocol</code></em> <em class="replaceable"><code>algorithm</code></em> <em class="replaceable"><code>key-data</code></em> ; [<span class="optional">...</span>]</span>]
7040 };
7041 </pre>
7042 </div>
7043 <div class="section">
7044 <div class="titlepage"><div><div><h3 class="title">
7045 <a name="managed-keys"></a><span class="command"><strong>managed-keys</strong></span> Statement Definition
7046             and Usage</h3></div></div></div>
7047 <p>
7048             The <span class="command"><strong>managed-keys</strong></span> statement, like
7049             <span class="command"><strong>trusted-keys</strong></span>, defines DNSSEC
7050             security roots.  The difference is that
7051             <span class="command"><strong>managed-keys</strong></span> can be kept up to date
7052             automatically, without intervention from the resolver
7053             operator.
7054           </p>
7055 <p>
7056             Suppose, for example, that a zone's key-signing
7057             key was compromised, and the zone owner had to revoke and
7058             replace the key.  A resolver which had the old key in a
7059             <span class="command"><strong>trusted-keys</strong></span> statement would be
7060             unable to validate this zone any longer; it would
7061             reply with a SERVFAIL response code.  This would
7062             continue until the resolver operator had updated the
7063             <span class="command"><strong>trusted-keys</strong></span> statement with the new key.
7064           </p>
7065 <p>
7066             If, however, the zone were listed in a
7067             <span class="command"><strong>managed-keys</strong></span> statement instead, then the
7068             zone owner could add a "stand-by" key to the zone in advance.
7069             <span class="command"><strong>named</strong></span> would store the stand-by key, and
7070             when the original key was revoked, <span class="command"><strong>named</strong></span>
7071             would be able to transition smoothly to the new key.  It would
7072             also recognize that the old key had been revoked, and cease
7073             using that key to validate answers, minimizing the damage that
7074             the compromised key could do.
7075           </p>
7076 <p>
7077             A <span class="command"><strong>managed-keys</strong></span> statement contains a list of
7078             the keys to be managed, along with information about how the
7079             keys are to be initialized for the first time.  The only
7080             initialization method currently supported (as of
7081             <acronym class="acronym">BIND</acronym> 9.7.0) is <code class="literal">initial-key</code>.
7082             This means the <span class="command"><strong>managed-keys</strong></span> statement must
7083             contain a copy of the initializing key.  (Future releases may
7084             allow keys to be initialized by other methods, eliminating this
7085             requirement.)
7086           </p>
7087 <p>
7088             Consequently, a <span class="command"><strong>managed-keys</strong></span> statement
7089             appears similar to a <span class="command"><strong>trusted-keys</strong></span>, differing
7090             in the presence of the second field, containing the keyword
7091             <code class="literal">initial-key</code>.  The difference is, whereas the
7092             keys listed in a <span class="command"><strong>trusted-keys</strong></span> continue to be
7093             trusted until they are removed from
7094             <code class="filename">named.conf</code>, an initializing key listed
7095             in a <span class="command"><strong>managed-keys</strong></span> statement is only trusted
7096             <span class="emphasis"><em>once</em></span>: for as long as it takes to load the
7097             managed key database and start the RFC 5011 key maintenance
7098             process.
7099           </p>
7100 <p>
7101             The first time <span class="command"><strong>named</strong></span> runs with a managed key
7102             configured in <code class="filename">named.conf</code>, it fetches the
7103             DNSKEY RRset directly from the zone apex, and validates it
7104             using the key specified in the <span class="command"><strong>managed-keys</strong></span>
7105             statement.  If the DNSKEY RRset is validly signed, then it is
7106             used as the basis for a new managed keys database.
7107           </p>
7108 <p>
7109             From that point on, whenever <span class="command"><strong>named</strong></span> runs, it
7110             sees the <span class="command"><strong>managed-keys</strong></span> statement, checks to
7111             make sure RFC 5011 key maintenance has already been initialized
7112             for the specified domain, and if so, it simply moves on.  The
7113             key specified in the <span class="command"><strong>managed-keys</strong></span> is not
7114             used to validate answers; it has been superseded by the key or
7115             keys stored in the managed keys database.
7116           </p>
7117 <p>
7118             The next time <span class="command"><strong>named</strong></span> runs after a name
7119             has been <span class="emphasis"><em>removed</em></span> from the
7120             <span class="command"><strong>managed-keys</strong></span> statement, the corresponding
7121             zone will be removed from the managed keys database,
7122             and RFC 5011 key maintenance will no longer be used for that
7123             domain.
7124           </p>
7125 <p>
7126             <span class="command"><strong>named</strong></span> only maintains a single managed keys
7127             database; consequently, unlike <span class="command"><strong>trusted-keys</strong></span>,
7128             <span class="command"><strong>managed-keys</strong></span> may only be set at the top
7129             level of <code class="filename">named.conf</code>, not within a view.
7130           </p>
7131 <p>
7132             In the current implementation, the managed keys database is
7133             stored as a master-format zone file called
7134             <code class="filename">managed-keys.bind</code>.  When the key database
7135             is changed, the zone is updated.  As with any other dynamic
7136             zone, changes will be written into a journal file,
7137             <code class="filename">managed-keys.bind.jnl</code>.  They are committed
7138             to the master file as soon as possible afterward; in the case
7139             of the managed key database, this will usually occur within 30
7140             seconds.  So, whenever <span class="command"><strong>named</strong></span> is using
7141             automatic key maintenance, those two files can be expected to
7142             exist in the working directory.  (For this reason among others,
7143             the working directory should be always be writable by
7144             <span class="command"><strong>named</strong></span>.)
7145           </p>
7146 <p>
7147             If the <span class="command"><strong>dnssec-validation</strong></span> option is
7148             set to <strong class="userinput"><code>auto</code></strong>, <span class="command"><strong>named</strong></span>
7149             will automatically initialize a managed key for the
7150             root zone.  Similarly, if the <span class="command"><strong>dnssec-lookaside</strong></span>
7151             option is set to <strong class="userinput"><code>auto</code></strong>,
7152             <span class="command"><strong>named</strong></span> will automatically initialize
7153             a managed key for the zone <code class="literal">dlv.isc.org</code>.
7154             In both cases, the key that is used to initialize the key
7155             maintenance process is built into <span class="command"><strong>named</strong></span>,
7156             and can be overridden from <span class="command"><strong>bindkeys-file</strong></span>.
7157           </p>
7158 </div>
7159 <div class="section">
7160 <div class="titlepage"><div><div><h3 class="title">
7161 <a name="view_statement_grammar"></a><span class="command"><strong>view</strong></span> Statement Grammar</h3></div></div></div>
7162 <pre class="programlisting"><span class="command"><strong>view</strong></span> <em class="replaceable"><code>view_name</code></em>
7163       [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7164       match-clients { <em class="replaceable"><code>address_match_list</code></em> };
7165       match-destinations { <em class="replaceable"><code>address_match_list</code></em> };
7166       match-recursive-only <em class="replaceable"><code>yes_or_no</code></em> ;
7167       [<span class="optional"> <em class="replaceable"><code>view_option</code></em>; ...</span>]
7168       [<span class="optional"> <em class="replaceable"><code>zone_statement</code></em>; ...</span>]
7169 };
7170 </pre>
7171 </div>
7172 <div class="section">
7173 <div class="titlepage"><div><div><h3 class="title">
7174 <a name="view_statement"></a><span class="command"><strong>view</strong></span> Statement Definition and Usage</h3></div></div></div>
7175 <p>
7176             The <span class="command"><strong>view</strong></span> statement is a powerful
7177             feature
7178             of <acronym class="acronym">BIND</acronym> 9 that lets a name server
7179             answer a DNS query differently
7180             depending on who is asking. It is particularly useful for
7181             implementing
7182             split DNS setups without having to run multiple servers.
7183           </p>
7184 <p>
7185             Each <span class="command"><strong>view</strong></span> statement defines a view
7186             of the
7187             DNS namespace that will be seen by a subset of clients.  A client
7188             matches
7189             a view if its source IP address matches the
7190             <code class="varname">address_match_list</code> of the view's
7191             <span class="command"><strong>match-clients</strong></span> clause and its
7192             destination IP address matches
7193             the <code class="varname">address_match_list</code> of the
7194             view's
7195             <span class="command"><strong>match-destinations</strong></span> clause.  If not
7196             specified, both
7197             <span class="command"><strong>match-clients</strong></span> and <span class="command"><strong>match-destinations</strong></span>
7198             default to matching all addresses.  In addition to checking IP
7199             addresses
7200             <span class="command"><strong>match-clients</strong></span> and <span class="command"><strong>match-destinations</strong></span>
7201             can also take <span class="command"><strong>keys</strong></span> which provide an
7202             mechanism for the
7203             client to select the view.  A view can also be specified
7204             as <span class="command"><strong>match-recursive-only</strong></span>, which
7205             means that only recursive
7206             requests from matching clients will match that view.
7207             The order of the <span class="command"><strong>view</strong></span> statements is
7208             significant &#8212;
7209             a client request will be resolved in the context of the first
7210             <span class="command"><strong>view</strong></span> that it matches.
7211           </p>
7212 <p>
7213             Zones defined within a <span class="command"><strong>view</strong></span>
7214             statement will
7215             only be accessible to clients that match the <span class="command"><strong>view</strong></span>.
7216             By defining a zone of the same name in multiple views, different
7217             zone data can be given to different clients, for example,
7218             "internal"
7219             and "external" clients in a split DNS setup.
7220           </p>
7221 <p>
7222             Many of the options given in the <span class="command"><strong>options</strong></span> statement
7223             can also be used within a <span class="command"><strong>view</strong></span>
7224             statement, and then
7225             apply only when resolving queries with that view.  When no
7226             view-specific
7227             value is given, the value in the <span class="command"><strong>options</strong></span> statement
7228             is used as a default.  Also, zone options can have default values
7229             specified
7230             in the <span class="command"><strong>view</strong></span> statement; these
7231             view-specific defaults
7232             take precedence over those in the <span class="command"><strong>options</strong></span> statement.
7233           </p>
7234 <p>
7235             Views are class specific.  If no class is given, class IN
7236             is assumed.  Note that all non-IN views must contain a hint zone,
7237             since only the IN class has compiled-in default hints.
7238           </p>
7239 <p>
7240             If there are no <span class="command"><strong>view</strong></span> statements in
7241             the config
7242             file, a default view that matches any client is automatically
7243             created
7244             in class IN. Any <span class="command"><strong>zone</strong></span> statements
7245             specified on
7246             the top level of the configuration file are considered to be part
7247             of
7248             this default view, and the <span class="command"><strong>options</strong></span>
7249             statement will
7250             apply to the default view. If any explicit <span class="command"><strong>view</strong></span>
7251             statements are present, all <span class="command"><strong>zone</strong></span>
7252             statements must
7253             occur inside <span class="command"><strong>view</strong></span> statements.
7254           </p>
7255 <p>
7256             Here is an example of a typical split DNS setup implemented
7257             using <span class="command"><strong>view</strong></span> statements:
7258           </p>
7259 <pre class="programlisting">view "internal" {
7260       // This should match our internal networks.
7261       match-clients { 10.0.0.0/8; };
7262
7263       // Provide recursive service to internal
7264       // clients only.
7265       recursion yes;
7266
7267       // Provide a complete view of the example.com
7268       // zone including addresses of internal hosts.
7269       zone "example.com" {
7270             type master;
7271             file "example-internal.db";
7272       };
7273 };
7274
7275 view "external" {
7276       // Match all clients not matched by the
7277       // previous view.
7278       match-clients { any; };
7279
7280       // Refuse recursive service to external clients.
7281       recursion no;
7282
7283       // Provide a restricted view of the example.com
7284       // zone containing only publicly accessible hosts.
7285       zone "example.com" {
7286            type master;
7287            file "example-external.db";
7288       };
7289 };
7290 </pre>
7291 </div>
7292 <div class="section">
7293 <div class="titlepage"><div><div><h3 class="title">
7294 <a name="zone_statement_grammar"></a><span class="command"><strong>zone</strong></span>
7295             Statement Grammar</h3></div></div></div>
7296 <pre class="programlisting"><span class="command"><strong>zone</strong></span> <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7297     type master;
7298     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7299     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7300     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7301     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7302     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7303     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7304     [<span class="optional"> dnssec-loadkeys-interval <em class="replaceable"><code>number</code></em>; </span>]
7305     [<span class="optional"> update-policy <em class="replaceable"><code>local</code></em> | { <em class="replaceable"><code>update_policy_rule</code></em> [<span class="optional">...</span>] }; </span>]
7306     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
7307     [<span class="optional"> check-mx (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
7308     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7309     [<span class="optional"> check-spf ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
7310     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7311     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
7312     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
7313     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
7314     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
7315     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
7316     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
7317     [<span class="optional"> forwarders { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; ... </span>] }; </span>]
7318     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
7319     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7320     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
7321     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7322     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7323     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
7324     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
7325     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
7326     [<span class="optional"> notify <em class="replaceable"><code>yes_or_no</code></em> | <em class="replaceable"><code>explicit</code></em> | <em class="replaceable"><code>master-only</code></em> ; </span>]
7327     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
7328     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7329     [<span class="optional"> pubkey <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ; </span>]
7330     [<span class="optional"> notify-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7331     [<span class="optional"> notify-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7332     [<span class="optional"> zone-statistics <em class="replaceable"><code>full</code></em> | <em class="replaceable"><code>terse</code></em> | <em class="replaceable"><code>none</code></em>; </span>]
7333     [<span class="optional"> sig-validity-interval <em class="replaceable"><code>number</code></em> [<span class="optional"><em class="replaceable"><code>number</code></em></span>] ; </span>]
7334     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
7335     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
7336     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
7337     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
7338     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7339     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7340     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7341     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7342     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
7343     [<span class="optional"> auto-dnssec <code class="constant">allow</code>|<code class="constant">maintain</code>|<code class="constant">off</code>; </span>]
7344     [<span class="optional"> inline-signing <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7345     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7346     [<span class="optional"> serial-update-method <code class="constant">increment</code>|<code class="constant">unixtime</code>; </span>]
7347 };
7348
7349 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7350     type slave;
7351     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7352     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7353     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7354     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7355     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7356     [<span class="optional"> dnssec-update-mode ( <em class="replaceable"><code>maintain</code></em> | <em class="replaceable"><code>no-resign</code></em> ); </span>]
7357     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7358     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7359     [<span class="optional"> dnssec-loadkeys-interval <em class="replaceable"><code>number</code></em>; </span>]
7360     [<span class="optional"> dnssec-secure-to-insecure <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7361     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7362     [<span class="optional"> also-notify [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] { ( <em class="replaceable"><code>masters_list</code></em> | <em class="replaceable"><code>ip_addr</code></em>
7363                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
7364                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
7365     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
7366     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
7367     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
7368     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
7369     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
7370     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
7371     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
7372     [<span class="optional"> forwarders { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; ... </span>] }; </span>]
7373     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
7374     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7375     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
7376     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7377     [<span class="optional"> masters [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] { ( <em class="replaceable"><code>masters_list</code></em> | <em class="replaceable"><code>ip_addr</code></em>
7378                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
7379                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
7380     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
7381     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
7382     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
7383     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
7384     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
7385     [<span class="optional"> notify <em class="replaceable"><code>yes_or_no</code></em> | <em class="replaceable"><code>explicit</code></em> | <em class="replaceable"><code>master-only</code></em> ; </span>]
7386     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
7387     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7388     [<span class="optional"> pubkey <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ; </span>]
7389     [<span class="optional"> transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7390     [<span class="optional"> transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7391     [<span class="optional"> alt-transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7392     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
7393                              [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7394     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7395     [<span class="optional"> notify-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7396     [<span class="optional"> notify-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7397     [<span class="optional"> zone-statistics <em class="replaceable"><code>full</code></em> | <em class="replaceable"><code>terse</code></em> | <em class="replaceable"><code>none</code></em>; </span>]
7398     [<span class="optional"> sig-validity-interval <em class="replaceable"><code>number</code></em> [<span class="optional"><em class="replaceable"><code>number</code></em></span>] ; </span>]
7399     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
7400     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
7401     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
7402     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
7403     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7404     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7405     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7406     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7407     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
7408     [<span class="optional"> auto-dnssec <code class="constant">allow</code>|<code class="constant">maintain</code>|<code class="constant">off</code>; </span>]
7409     [<span class="optional"> inline-signing <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7410     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7411     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7412 };
7413
7414 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7415     type hint;
7416     file <em class="replaceable"><code>string</code></em> ;
7417     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7418     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>] // Not Implemented.
7419 };
7420
7421 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7422     type stub;
7423     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7424     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7425     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
7426     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
7427     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7428     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
7429     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
7430     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
7431     [<span class="optional"> forwarders { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; ... </span>] }; </span>]
7432     [<span class="optional"> masters [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] { ( <em class="replaceable"><code>masters_list</code></em> | <em class="replaceable"><code>ip_addr</code></em>
7433                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
7434                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
7435     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
7436     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
7437     [<span class="optional"> pubkey <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>number</code></em> <em class="replaceable"><code>string</code></em> ; </span>]
7438     [<span class="optional"> transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7439     [<span class="optional"> transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
7440                          [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7441     [<span class="optional"> alt-transfer-source (<em class="replaceable"><code>ip4_addr</code></em> | <code class="constant">*</code>) [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7442     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
7443                             [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7444     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7445     [<span class="optional"> zone-statistics <em class="replaceable"><code>full</code></em> | <em class="replaceable"><code>terse</code></em> | <em class="replaceable"><code>none</code></em>; </span>]
7446     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
7447     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7448     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7449     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7450     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7451     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7452 };
7453
7454 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7455     type static-stub;
7456     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7457     [<span class="optional"> server-addresses { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> ; ... </span>] }; </span>]
7458     [<span class="optional"> server-names { [<span class="optional"> <em class="replaceable"><code>namelist</code></em> </span>] }; </span>]
7459     [<span class="optional"> zone-statistics <em class="replaceable"><code>full</code></em> | <em class="replaceable"><code>terse</code></em> | <em class="replaceable"><code>none</code></em>; </span>]
7460 };
7461
7462 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7463     type forward;
7464     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
7465     [<span class="optional"> forwarders { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; ... </span>] }; </span>]
7466     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7467 };
7468
7469 zone <em class="replaceable"><code>"."</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7470     type redirect;
7471     file <em class="replaceable"><code>string</code></em> ;
7472     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
7473     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7474 };
7475
7476 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7477     type delegation-only;
7478 };
7479
7480 </pre>
7481 </div>
7482 <div class="section">
7483 <div class="titlepage"><div><div><h3 class="title">
7484 <a name="zone_statement"></a><span class="command"><strong>zone</strong></span> Statement Definition and Usage</h3></div></div></div>
7485 <div class="section">
7486 <div class="titlepage"><div><div><h4 class="title">
7487 <a name="zone_types"></a>Zone Types</h4></div></div></div>
7488 <p>
7489               The <span class="command"><strong>type</strong></span> keyword is required
7490               for the <span class="command"><strong>zone</strong></span> configuration. Its
7491               acceptable values include: <code class="varname">delegation-only</code>,
7492               <code class="varname">forward</code>, <code class="varname">hint</code>,
7493               <code class="varname">master</code>, <code class="varname">redirect</code>,
7494               <code class="varname">slave</code>, <code class="varname">static-stub</code>,
7495               and <code class="varname">stub</code>.
7496             </p>
7497 <div class="informaltable"><table border="1">
7498 <colgroup>
7499 <col class="1">
7500 <col width="4.017in" class="2">
7501 </colgroup>
7502 <tbody>
7503 <tr>
7504 <td>
7505                       <p>
7506                         <code class="varname">master</code>
7507                       </p>
7508                     </td>
7509 <td>
7510                       <p>
7511                         The server has a master copy of the data
7512                         for the zone and will be able to provide authoritative
7513                         answers for
7514                         it.
7515                       </p>
7516                     </td>
7517 </tr>
7518 <tr>
7519 <td>
7520                       <p>
7521                         <code class="varname">slave</code>
7522                       </p>
7523                     </td>
7524 <td>
7525                       <p>
7526                         A slave zone is a replica of a master
7527                         zone. The <span class="command"><strong>masters</strong></span> list
7528                         specifies one or more IP addresses
7529                         of master servers that the slave contacts to update
7530                         its copy of the zone.
7531                         Masters list elements can also be names of other
7532                         masters lists.
7533                         By default, transfers are made from port 53 on the
7534                         servers; this can
7535                         be changed for all servers by specifying a port number
7536                         before the
7537                         list of IP addresses, or on a per-server basis after
7538                         the IP address.
7539                         Authentication to the master can also be done with
7540                         per-server TSIG keys.
7541                         If a file is specified, then the
7542                         replica will be written to this file whenever the zone
7543                         is changed,
7544                         and reloaded from this file on a server restart. Use
7545                         of a file is
7546                         recommended, since it often speeds server startup and
7547                         eliminates
7548                         a needless waste of bandwidth. Note that for large
7549                         numbers (in the
7550                         tens or hundreds of thousands) of zones per server, it
7551                         is best to
7552                         use a two-level naming scheme for zone filenames. For
7553                         example,
7554                         a slave server for the zone <code class="literal">example.com</code> might place
7555                         the zone contents into a file called
7556                         <code class="filename">ex/example.com</code> where <code class="filename">ex/</code> is
7557                         just the first two letters of the zone name. (Most
7558                         operating systems
7559                         behave very slowly if you put 100000 files into
7560                         a single directory.)
7561                       </p>
7562                     </td>
7563 </tr>
7564 <tr>
7565 <td>
7566                       <p>
7567                         <code class="varname">stub</code>
7568                       </p>
7569                     </td>
7570 <td>
7571                       <p>
7572                         A stub zone is similar to a slave zone,
7573                         except that it replicates only the NS records of a
7574                         master zone instead
7575                         of the entire zone. Stub zones are not a standard part
7576                         of the DNS;
7577                         they are a feature specific to the <acronym class="acronym">BIND</acronym> implementation.
7578                       </p>
7579
7580                       <p>
7581                         Stub zones can be used to eliminate the need for glue
7582                         NS record
7583                         in a parent zone at the expense of maintaining a stub
7584                         zone entry and
7585                         a set of name server addresses in <code class="filename">named.conf</code>.
7586                         This usage is not recommended for new configurations,
7587                         and BIND 9
7588                         supports it only in a limited way.
7589                         In <acronym class="acronym">BIND</acronym> 4/8, zone
7590                         transfers of a parent zone
7591                         included the NS records from stub children of that
7592                         zone. This meant
7593                         that, in some cases, users could get away with
7594                         configuring child stubs
7595                         only in the master server for the parent zone. <acronym class="acronym">BIND</acronym>
7596                         9 never mixes together zone data from different zones
7597                         in this
7598                         way. Therefore, if a <acronym class="acronym">BIND</acronym> 9 master serving a parent
7599                         zone has child stub zones configured, all the slave
7600                         servers for the
7601                         parent zone also need to have the same child stub
7602                         zones
7603                         configured.
7604                       </p>
7605
7606                       <p>
7607                         Stub zones can also be used as a way of forcing the
7608                         resolution
7609                         of a given domain to use a particular set of
7610                         authoritative servers.
7611                         For example, the caching name servers on a private
7612                         network using
7613                         RFC1918 addressing may be configured with stub zones
7614                         for
7615                         <code class="literal">10.in-addr.arpa</code>
7616                         to use a set of internal name servers as the
7617                         authoritative
7618                         servers for that domain.
7619                       </p>
7620                     </td>
7621 </tr>
7622 <tr>
7623 <td>
7624                       <p>
7625                         <code class="varname">static-stub</code>
7626                       </p>
7627                     </td>
7628 <td>
7629                       <p>
7630                         A static-stub zone is similar to a stub zone
7631                         with the following exceptions:
7632                         the zone data is statically configured, rather
7633                         than transferred from a master server;
7634                         when recursion is necessary for a query that
7635                         matches a static-stub zone, the locally
7636                         configured data (nameserver names and glue addresses)
7637                         is always used even if different authoritative
7638                         information is cached.
7639                       </p>
7640                       <p>
7641                         Zone data is configured via the
7642                         <span class="command"><strong>server-addresses</strong></span> and
7643                         <span class="command"><strong>server-names</strong></span> zone options.
7644                       </p>
7645                       <p>
7646                         The zone data is maintained in the form of NS
7647                         and (if necessary) glue A or AAAA RRs
7648                         internally, which can be seen by dumping zone
7649                         databases by <span class="command"><strong>rndc dumpdb -all</strong></span>.
7650                         The configured RRs are considered local configuration
7651                         parameters rather than public data.
7652                         Non recursive queries (i.e., those with the RD
7653                         bit off) to a static-stub zone are therefore
7654                         prohibited and will be responded with REFUSED.
7655                       </p>
7656                       <p>
7657                         Since the data is statically configured, no
7658                         zone maintenance action takes place for a static-stub
7659                         zone.
7660                         For example, there is no periodic refresh
7661                         attempt, and an incoming notify message
7662                         will be rejected with an rcode of NOTAUTH.
7663                       </p>
7664                       <p>
7665                         Each static-stub zone is configured with
7666                         internally generated NS and (if necessary)
7667                         glue A or AAAA RRs
7668                       </p>
7669                     </td>
7670 </tr>
7671 <tr>
7672 <td>
7673                       <p>
7674                         <code class="varname">forward</code>
7675                       </p>
7676                     </td>
7677 <td>
7678                       <p>
7679                         A "forward zone" is a way to configure
7680                         forwarding on a per-domain basis.  A <span class="command"><strong>zone</strong></span> statement
7681                         of type <span class="command"><strong>forward</strong></span> can
7682                         contain a <span class="command"><strong>forward</strong></span>
7683                         and/or <span class="command"><strong>forwarders</strong></span>
7684                         statement,
7685                         which will apply to queries within the domain given by
7686                         the zone
7687                         name. If no <span class="command"><strong>forwarders</strong></span>
7688                         statement is present or
7689                         an empty list for <span class="command"><strong>forwarders</strong></span> is given, then no
7690                         forwarding will be done for the domain, canceling the
7691                         effects of
7692                         any forwarders in the <span class="command"><strong>options</strong></span> statement. Thus
7693                         if you want to use this type of zone to change the
7694                         behavior of the
7695                         global <span class="command"><strong>forward</strong></span> option
7696                         (that is, "forward first"
7697                         to, then "forward only", or vice versa, but want to
7698                         use the same
7699                         servers as set globally) you need to re-specify the
7700                         global forwarders.
7701                       </p>
7702                     </td>
7703 </tr>
7704 <tr>
7705 <td>
7706                       <p>
7707                         <code class="varname">hint</code>
7708                       </p>
7709                     </td>
7710 <td>
7711                       <p>
7712                         The initial set of root name servers is
7713                         specified using a "hint zone". When the server starts
7714                         up, it uses
7715                         the root hints to find a root name server and get the
7716                         most recent
7717                         list of root name servers. If no hint zone is
7718                         specified for class
7719                         IN, the server uses a compiled-in default set of root
7720                         servers hints.
7721                         Classes other than IN have no built-in defaults hints.
7722                       </p>
7723                     </td>
7724 </tr>
7725 <tr>
7726 <td>
7727                       <p>
7728                         <code class="varname">redirect</code>
7729                       </p>
7730                     </td>
7731 <td>
7732                       <p>
7733                         Redirect zones are used to provide answers to
7734                         queries when normal resolution would result in
7735                         NXDOMAIN being returned.
7736                         Only one redirect zone is supported
7737                         per view.  <span class="command"><strong>allow-query</strong></span> can be
7738                         used to restrict which clients see these answers.
7739                       </p>
7740                       <p>
7741                         If the client has requested DNSSEC records (DO=1) and
7742                         the NXDOMAIN response is signed then no substitution
7743                         will occur.
7744                       </p>
7745                       <p>
7746                         To redirect all NXDOMAIN responses to
7747                         100.100.100.2 and
7748                         2001:ffff:ffff::100.100.100.2, one would
7749                         configure a type redirect zone named ".",
7750                         with the zone file containing wildcard records
7751                         that point to the desired addresses:
7752                         <code class="literal">"*. IN A 100.100.100.2"</code>
7753                         and
7754                         <code class="literal">"*. IN AAAA 2001:ffff:ffff::100.100.100.2"</code>.
7755                       </p>
7756                       <p>
7757                         To redirect all Spanish names (under .ES) one
7758                         would use similar entries but with the names
7759                         "*.ES." instead of "*.".  To redirect all
7760                         commercial Spanish names (under COM.ES) one
7761                         would use wildcard entries called "*.COM.ES.".
7762                       </p>
7763                       <p>
7764                         Note that the redirect zone supports all
7765                         possible types; it is not limited to A and
7766                         AAAA records.
7767                       </p>
7768                       <p>
7769                         Because redirect zones are not referenced
7770                         directly by name, they are not kept in the
7771                         zone lookup table with normal master and slave
7772                         zones. Consequently, it is not currently possible
7773                         to use
7774                         <span class="command"><strong>rndc reload
7775                                 <em class="replaceable"><code>zonename</code></em></strong></span>
7776                         to reload a redirect zone.  However, when using
7777                         <span class="command"><strong>rndc reload</strong></span> without specifying
7778                         a zone name, redirect zones will be reloaded along
7779                         with other zones.
7780                       </p>
7781                     </td>
7782 </tr>
7783 <tr>
7784 <td>
7785                       <p>
7786                         <code class="varname">delegation-only</code>
7787                       </p>
7788                     </td>
7789 <td>
7790                       <p>
7791                         This is used to enforce the delegation-only
7792                         status of infrastructure zones (e.g. COM,
7793                         NET, ORG).  Any answer that is received
7794                         without an explicit or implicit delegation
7795                         in the authority section will be treated
7796                         as NXDOMAIN.  This does not apply to the
7797                         zone apex.  This should not be applied to
7798                         leaf zones.
7799                       </p>
7800                       <p>
7801                         <code class="varname">delegation-only</code> has no
7802                         effect on answers received from forwarders.
7803                       </p>
7804                       <p>
7805                         See caveats in <a class="xref" href="Bv9ARM.ch06.html#root_delegation_only"><span class="command"><strong>root-delegation-only</strong></span></a>.
7806                       </p>
7807                     </td>
7808 </tr>
7809 </tbody>
7810 </table></div>
7811 </div>
7812 <div class="section">
7813 <div class="titlepage"><div><div><h4 class="title">
7814 <a name="class"></a>Class</h4></div></div></div>
7815 <p>
7816               The zone's name may optionally be followed by a class. If
7817               a class is not specified, class <code class="literal">IN</code> (for <code class="varname">Internet</code>),
7818               is assumed. This is correct for the vast majority of cases.
7819             </p>
7820 <p>
7821               The <code class="literal">hesiod</code> class is
7822               named for an information service from MIT's Project Athena. It
7823               is
7824               used to share information about various systems databases, such
7825               as users, groups, printers and so on. The keyword
7826               <code class="literal">HS</code> is
7827               a synonym for hesiod.
7828             </p>
7829 <p>
7830               Another MIT development is Chaosnet, a LAN protocol created
7831               in the mid-1970s. Zone data for it can be specified with the <code class="literal">CHAOS</code> class.
7832             </p>
7833 </div>
7834 <div class="section">
7835 <div class="titlepage"><div><div><h4 class="title">
7836 <a name="zone_options"></a>Zone Options</h4></div></div></div>
7837 <div class="variablelist"><dl class="variablelist">
7838 <dt><span class="term"><span class="command"><strong>allow-notify</strong></span></span></dt>
7839 <dd><p>
7840                     See the description of
7841                     <span class="command"><strong>allow-notify</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
7842                   </p></dd>
7843 <dt><span class="term"><span class="command"><strong>allow-query</strong></span></span></dt>
7844 <dd><p>
7845                     See the description of
7846                     <span class="command"><strong>allow-query</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
7847                   </p></dd>
7848 <dt><span class="term"><span class="command"><strong>allow-query-on</strong></span></span></dt>
7849 <dd><p>
7850                     See the description of
7851                     <span class="command"><strong>allow-query-on</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
7852                   </p></dd>
7853 <dt><span class="term"><span class="command"><strong>allow-transfer</strong></span></span></dt>
7854 <dd><p>
7855                     See the description of <span class="command"><strong>allow-transfer</strong></span>
7856                     in <a class="xref" href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
7857                   </p></dd>
7858 <dt><span class="term"><span class="command"><strong>allow-update</strong></span></span></dt>
7859 <dd><p>
7860                     See the description of <span class="command"><strong>allow-update</strong></span>
7861                     in <a class="xref" href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
7862                   </p></dd>
7863 <dt><span class="term"><span class="command"><strong>update-policy</strong></span></span></dt>
7864 <dd><p>
7865                     Specifies a "Simple Secure Update" policy. See
7866                     <a class="xref" href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>.
7867                   </p></dd>
7868 <dt><span class="term"><span class="command"><strong>allow-update-forwarding</strong></span></span></dt>
7869 <dd><p>
7870                     See the description of <span class="command"><strong>allow-update-forwarding</strong></span>
7871                     in <a class="xref" href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
7872                   </p></dd>
7873 <dt><span class="term"><span class="command"><strong>also-notify</strong></span></span></dt>
7874 <dd><p>
7875                     Only meaningful if <span class="command"><strong>notify</strong></span>
7876                     is
7877                     active for this zone. The set of machines that will
7878                     receive a
7879                     <code class="literal">DNS NOTIFY</code> message
7880                     for this zone is made up of all the listed name servers
7881                     (other than
7882                     the primary master) for the zone plus any IP addresses
7883                     specified
7884                     with <span class="command"><strong>also-notify</strong></span>. A port
7885                     may be specified
7886                     with each <span class="command"><strong>also-notify</strong></span>
7887                     address to send the notify
7888                     messages to a port other than the default of 53.
7889                     A TSIG key may also be specified to cause the
7890                     <code class="literal">NOTIFY</code> to be signed by the
7891                     given key.
7892                     <span class="command"><strong>also-notify</strong></span> is not
7893                     meaningful for stub zones.
7894                     The default is the empty list.
7895                   </p></dd>
7896 <dt><span class="term"><span class="command"><strong>check-names</strong></span></span></dt>
7897 <dd><p>
7898                     This option is used to restrict the character set and
7899                     syntax of
7900                     certain domain names in master files and/or DNS responses
7901                     received from the
7902                     network.  The default varies according to zone type.  For <span class="command"><strong>master</strong></span> zones the default is <span class="command"><strong>fail</strong></span>.  For <span class="command"><strong>slave</strong></span>
7903                     zones the default is <span class="command"><strong>warn</strong></span>.
7904                     It is not implemented for <span class="command"><strong>hint</strong></span> zones.
7905                   </p></dd>
7906 <dt><span class="term"><span class="command"><strong>check-mx</strong></span></span></dt>
7907 <dd><p>
7908                     See the description of
7909                     <span class="command"><strong>check-mx</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7910                   </p></dd>
7911 <dt><span class="term"><span class="command"><strong>check-spf</strong></span></span></dt>
7912 <dd><p>
7913                     See the description of
7914                     <span class="command"><strong>check-spf</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7915                   </p></dd>
7916 <dt><span class="term"><span class="command"><strong>check-wildcard</strong></span></span></dt>
7917 <dd><p>
7918                     See the description of
7919                     <span class="command"><strong>check-wildcard</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7920                   </p></dd>
7921 <dt><span class="term"><span class="command"><strong>check-integrity</strong></span></span></dt>
7922 <dd><p>
7923                     See the description of
7924                     <span class="command"><strong>check-integrity</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7925                   </p></dd>
7926 <dt><span class="term"><span class="command"><strong>check-sibling</strong></span></span></dt>
7927 <dd><p>
7928                     See the description of
7929                     <span class="command"><strong>check-sibling</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7930                   </p></dd>
7931 <dt><span class="term"><span class="command"><strong>zero-no-soa-ttl</strong></span></span></dt>
7932 <dd><p>
7933                     See the description of
7934                     <span class="command"><strong>zero-no-soa-ttl</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7935                   </p></dd>
7936 <dt><span class="term"><span class="command"><strong>update-check-ksk</strong></span></span></dt>
7937 <dd><p>
7938                     See the description of
7939                     <span class="command"><strong>update-check-ksk</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7940                   </p></dd>
7941 <dt><span class="term"><span class="command"><strong>dnssec-loadkeys-interval</strong></span></span></dt>
7942 <dd><p>
7943                     See the description of
7944                     <span class="command"><strong>dnssec-loadkeys-interval</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#options" title="options Statement Definition and Usage">the section called &#8220;<span class="command"><strong>options</strong></span> Statement Definition and
7945           Usage&#8221;</a>.
7946                   </p></dd>
7947 <dt><span class="term"><span class="command"><strong>dnssec-update-mode</strong></span></span></dt>
7948 <dd><p>
7949                     See the description of
7950                     <span class="command"><strong>dnssec-update-mode</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#options" title="options Statement Definition and Usage">the section called &#8220;<span class="command"><strong>options</strong></span> Statement Definition and
7951           Usage&#8221;</a>.
7952                   </p></dd>
7953 <dt><span class="term"><span class="command"><strong>dnssec-dnskey-kskonly</strong></span></span></dt>
7954 <dd><p>
7955                     See the description of
7956                     <span class="command"><strong>dnssec-dnskey-kskonly</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7957                   </p></dd>
7958 <dt><span class="term"><span class="command"><strong>try-tcp-refresh</strong></span></span></dt>
7959 <dd><p>
7960                     See the description of
7961                     <span class="command"><strong>try-tcp-refresh</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7962                   </p></dd>
7963 <dt><span class="term"><span class="command"><strong>database</strong></span></span></dt>
7964 <dd>
7965 <p>
7966                     Specify the type of database to be used for storing the
7967                     zone data.  The string following the <span class="command"><strong>database</strong></span> keyword
7968                     is interpreted as a list of whitespace-delimited words.
7969                     The first word
7970                     identifies the database type, and any subsequent words are
7971                     passed
7972                     as arguments to the database to be interpreted in a way
7973                     specific
7974                     to the database type.
7975                   </p>
7976 <p>
7977                     The default is <strong class="userinput"><code>"rbt"</code></strong>, BIND 9's
7978                     native in-memory
7979                     red-black-tree database.  This database does not take
7980                     arguments.
7981                   </p>
7982 <p>
7983                     Other values are possible if additional database drivers
7984                     have been linked into the server.  Some sample drivers are
7985                     included
7986                     with the distribution but none are linked in by default.
7987                   </p>
7988 </dd>
7989 <dt><span class="term"><span class="command"><strong>dialup</strong></span></span></dt>
7990 <dd><p>
7991                     See the description of
7992                     <span class="command"><strong>dialup</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7993                   </p></dd>
7994 <dt><span class="term"><span class="command"><strong>delegation-only</strong></span></span></dt>
7995 <dd>
7996 <p>
7997                     The flag only applies to forward, hint and stub
7998                     zones.  If set to <strong class="userinput"><code>yes</code></strong>,
7999                     then the zone will also be treated as if it is
8000                     also a delegation-only type zone.
8001                   </p>
8002 <p>
8003                     See caveats in <a class="xref" href="Bv9ARM.ch06.html#root_delegation_only"><span class="command"><strong>root-delegation-only</strong></span></a>.
8004                   </p>
8005 </dd>
8006 <dt><span class="term"><span class="command"><strong>forward</strong></span></span></dt>
8007 <dd><p>
8008                     Only meaningful if the zone has a forwarders
8009                     list. The <span class="command"><strong>only</strong></span> value causes
8010                     the lookup to fail
8011                     after trying the forwarders and getting no answer, while <span class="command"><strong>first</strong></span> would
8012                     allow a normal lookup to be tried.
8013                   </p></dd>
8014 <dt><span class="term"><span class="command"><strong>forwarders</strong></span></span></dt>
8015 <dd><p>
8016                     Used to override the list of global forwarders.
8017                     If it is not specified in a zone of type <span class="command"><strong>forward</strong></span>,
8018                     no forwarding is done for the zone and the global options are
8019                     not used.
8020                   </p></dd>
8021 <dt><span class="term"><span class="command"><strong>ixfr-base</strong></span></span></dt>
8022 <dd><p>
8023                     Was used in <acronym class="acronym">BIND</acronym> 8 to
8024                     specify the name
8025                     of the transaction log (journal) file for dynamic update
8026                     and IXFR.
8027                     <acronym class="acronym">BIND</acronym> 9 ignores the option
8028                     and constructs the name of the journal
8029                     file by appending "<code class="filename">.jnl</code>"
8030                     to the name of the
8031                     zone file.
8032                   </p></dd>
8033 <dt><span class="term"><span class="command"><strong>ixfr-tmp-file</strong></span></span></dt>
8034 <dd><p>
8035                     Was an undocumented option in <acronym class="acronym">BIND</acronym> 8.
8036                     Ignored in <acronym class="acronym">BIND</acronym> 9.
8037                   </p></dd>
8038 <dt><span class="term"><span class="command"><strong>journal</strong></span></span></dt>
8039 <dd><p>
8040                     Allow the default journal's filename to be overridden.
8041                     The default is the zone's filename with "<code class="filename">.jnl</code>" appended.
8042                     This is applicable to <span class="command"><strong>master</strong></span> and <span class="command"><strong>slave</strong></span> zones.
8043                   </p></dd>
8044 <dt><span class="term"><span class="command"><strong>max-journal-size</strong></span></span></dt>
8045 <dd><p>
8046                     See the description of
8047                     <span class="command"><strong>max-journal-size</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#server_resource_limits" title="Server Resource Limits">the section called &#8220;Server  Resource Limits&#8221;</a>.
8048                   </p></dd>
8049 <dt><span class="term"><span class="command"><strong>max-transfer-time-in</strong></span></span></dt>
8050 <dd><p>
8051                     See the description of
8052                     <span class="command"><strong>max-transfer-time-in</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8053                   </p></dd>
8054 <dt><span class="term"><span class="command"><strong>max-transfer-idle-in</strong></span></span></dt>
8055 <dd><p>
8056                     See the description of
8057                     <span class="command"><strong>max-transfer-idle-in</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8058                   </p></dd>
8059 <dt><span class="term"><span class="command"><strong>max-transfer-time-out</strong></span></span></dt>
8060 <dd><p>
8061                     See the description of
8062                     <span class="command"><strong>max-transfer-time-out</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8063                   </p></dd>
8064 <dt><span class="term"><span class="command"><strong>max-transfer-idle-out</strong></span></span></dt>
8065 <dd><p>
8066                     See the description of
8067                     <span class="command"><strong>max-transfer-idle-out</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8068                   </p></dd>
8069 <dt><span class="term"><span class="command"><strong>notify</strong></span></span></dt>
8070 <dd><p>
8071                     See the description of
8072                     <span class="command"><strong>notify</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8073                   </p></dd>
8074 <dt><span class="term"><span class="command"><strong>notify-delay</strong></span></span></dt>
8075 <dd><p>
8076                     See the description of
8077                     <span class="command"><strong>notify-delay</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8078                   </p></dd>
8079 <dt><span class="term"><span class="command"><strong>notify-to-soa</strong></span></span></dt>
8080 <dd><p>
8081                     See the description of
8082                     <span class="command"><strong>notify-to-soa</strong></span> in
8083                     <a class="xref" href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8084                   </p></dd>
8085 <dt><span class="term"><span class="command"><strong>pubkey</strong></span></span></dt>
8086 <dd><p>
8087                     In <acronym class="acronym">BIND</acronym> 8, this option was
8088                     intended for specifying
8089                     a public zone key for verification of signatures in DNSSEC
8090                     signed
8091                     zones when they are loaded from disk. <acronym class="acronym">BIND</acronym> 9 does not verify signatures
8092                     on load and ignores the option.
8093                   </p></dd>
8094 <dt><span class="term"><span class="command"><strong>zone-statistics</strong></span></span></dt>
8095 <dd><p>
8096                     See the description of
8097                     <span class="command"><strong>zone-statistics</strong></span> in
8098                     <a class="xref" href="Bv9ARM.ch06.html#options" title="options Statement Definition and Usage">the section called &#8220;<span class="command"><strong>options</strong></span> Statement Definition and
8099           Usage&#8221;</a>.
8100                   </p></dd>
8101 <dt><span class="term"><span class="command"><strong>server-addresses</strong></span></span></dt>
8102 <dd>
8103 <p>
8104                     Only meaningful for static-stub zones.
8105                     This is a list of IP addresses to which queries
8106                     should be sent in recursive resolution for the
8107                     zone.
8108                     A non empty list for this option will internally
8109                     configure the apex NS RR with associated glue A or
8110                     AAAA RRs.
8111                   </p>
8112 <p>
8113                     For example, if "example.com" is configured as a
8114                     static-stub zone with 192.0.2.1 and 2001:db8::1234
8115                     in a <span class="command"><strong>server-addresses</strong></span> option,
8116                     the following RRs will be internally configured.
8117                   </p>
8118 <pre class="programlisting">example.com. NS example.com.
8119 example.com. A 192.0.2.1
8120 example.com. AAAA 2001:db8::1234</pre>
8121 <p>
8122                     These records are internally used to resolve
8123                     names under the static-stub zone.
8124                     For instance, if the server receives a query for
8125                     "www.example.com" with the RD bit on, the server
8126                     will initiate recursive resolution and send
8127                     queries to 192.0.2.1 and/or 2001:db8::1234.
8128                   </p>
8129 </dd>
8130 <dt><span class="term"><span class="command"><strong>server-names</strong></span></span></dt>
8131 <dd>
8132 <p>
8133                     Only meaningful for static-stub zones.
8134                     This is a list of domain names of nameservers that
8135                     act as authoritative servers of the static-stub
8136                     zone.
8137                     These names will be resolved to IP addresses when
8138                     <span class="command"><strong>named</strong></span> needs to send queries to
8139                     these servers.
8140                     To make this supplemental resolution successful,
8141                     these names must not be a subdomain of the origin
8142                     name of static-stub zone.
8143                     That is, when "example.net" is the origin of a
8144                     static-stub zone, "ns.example" and
8145                     "master.example.com" can be specified in the
8146                     <span class="command"><strong>server-names</strong></span> option, but
8147                     "ns.example.net" cannot, and will be rejected by
8148                     the configuration parser.
8149                   </p>
8150 <p>
8151                     A non empty list for this option will internally
8152                     configure the apex NS RR with the specified names.
8153                     For example, if "example.com" is configured as a
8154                     static-stub zone with "ns1.example.net" and
8155                     "ns2.example.net"
8156                     in a <span class="command"><strong>server-names</strong></span> option,
8157                     the following RRs will be internally configured.
8158                   </p>
8159 <pre class="programlisting">example.com. NS ns1.example.net.
8160 example.com. NS ns2.example.net.
8161 </pre>
8162 <p>
8163                     These records are internally used to resolve
8164                     names under the static-stub zone.
8165                     For instance, if the server receives a query for
8166                     "www.example.com" with the RD bit on, the server
8167                     initiate recursive resolution,
8168                     resolve "ns1.example.net" and/or
8169                     "ns2.example.net" to IP addresses, and then send
8170                     queries to (one or more of) these addresses.
8171                   </p>
8172 </dd>
8173 <dt><span class="term"><span class="command"><strong>sig-validity-interval</strong></span></span></dt>
8174 <dd><p>
8175                     See the description of
8176                     <span class="command"><strong>sig-validity-interval</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8177                   </p></dd>
8178 <dt><span class="term"><span class="command"><strong>sig-signing-nodes</strong></span></span></dt>
8179 <dd><p>
8180                     See the description of
8181                     <span class="command"><strong>sig-signing-nodes</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8182                   </p></dd>
8183 <dt><span class="term"><span class="command"><strong>sig-signing-signatures</strong></span></span></dt>
8184 <dd><p>
8185                     See the description of
8186                     <span class="command"><strong>sig-signing-signatures</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8187                   </p></dd>
8188 <dt><span class="term"><span class="command"><strong>sig-signing-type</strong></span></span></dt>
8189 <dd><p>
8190                     See the description of
8191                     <span class="command"><strong>sig-signing-type</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8192                   </p></dd>
8193 <dt><span class="term"><span class="command"><strong>transfer-source</strong></span></span></dt>
8194 <dd><p>
8195                     See the description of
8196                     <span class="command"><strong>transfer-source</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8197                   </p></dd>
8198 <dt><span class="term"><span class="command"><strong>transfer-source-v6</strong></span></span></dt>
8199 <dd><p>
8200                     See the description of
8201                     <span class="command"><strong>transfer-source-v6</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8202                   </p></dd>
8203 <dt><span class="term"><span class="command"><strong>alt-transfer-source</strong></span></span></dt>
8204 <dd><p>
8205                     See the description of
8206                     <span class="command"><strong>alt-transfer-source</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8207                   </p></dd>
8208 <dt><span class="term"><span class="command"><strong>alt-transfer-source-v6</strong></span></span></dt>
8209 <dd><p>
8210                     See the description of
8211                     <span class="command"><strong>alt-transfer-source-v6</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8212                   </p></dd>
8213 <dt><span class="term"><span class="command"><strong>use-alt-transfer-source</strong></span></span></dt>
8214 <dd><p>
8215                     See the description of
8216                     <span class="command"><strong>use-alt-transfer-source</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8217                   </p></dd>
8218 <dt><span class="term"><span class="command"><strong>notify-source</strong></span></span></dt>
8219 <dd><p>
8220                     See the description of
8221                     <span class="command"><strong>notify-source</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8222                   </p></dd>
8223 <dt><span class="term"><span class="command"><strong>notify-source-v6</strong></span></span></dt>
8224 <dd><p>
8225                     See the description of
8226                     <span class="command"><strong>notify-source-v6</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
8227                   </p></dd>
8228 <dt>
8229 <span class="term"><span class="command"><strong>min-refresh-time</strong></span>, </span><span class="term"><span class="command"><strong>max-refresh-time</strong></span>, </span><span class="term"><span class="command"><strong>min-retry-time</strong></span>, </span><span class="term"><span class="command"><strong>max-retry-time</strong></span></span>
8230 </dt>
8231 <dd><p>
8232                     See the description in <a class="xref" href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8233                   </p></dd>
8234 <dt><span class="term"><span class="command"><strong>ixfr-from-differences</strong></span></span></dt>
8235 <dd><p>
8236                     See the description of
8237                     <span class="command"><strong>ixfr-from-differences</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8238                     (Note that the <span class="command"><strong>ixfr-from-differences</strong></span>
8239                     <strong class="userinput"><code>master</code></strong> and
8240                     <strong class="userinput"><code>slave</code></strong> choices are not
8241                     available at the zone level.)
8242                   </p></dd>
8243 <dt><span class="term"><span class="command"><strong>key-directory</strong></span></span></dt>
8244 <dd><p>
8245                     See the description of
8246                     <span class="command"><strong>key-directory</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#options" title="options Statement Definition and Usage">the section called &#8220;<span class="command"><strong>options</strong></span> Statement Definition and
8247           Usage&#8221;</a>.
8248                   </p></dd>
8249 <dt><span class="term"><span class="command"><strong>auto-dnssec</strong></span></span></dt>
8250 <dd><p>
8251                     See the description of
8252                     <span class="command"><strong>auto-dnssec</strong></span> in
8253                     <a class="xref" href="Bv9ARM.ch06.html#options" title="options Statement Definition and Usage">the section called &#8220;<span class="command"><strong>options</strong></span> Statement Definition and
8254           Usage&#8221;</a>.
8255                   </p></dd>
8256 <dt><span class="term"><span class="command"><strong>serial-update-method</strong></span></span></dt>
8257 <dd><p>
8258                     See the description of
8259                     <span class="command"><strong>serial-update-method</strong></span> in
8260                     <a class="xref" href="Bv9ARM.ch06.html#options" title="options Statement Definition and Usage">the section called &#8220;<span class="command"><strong>options</strong></span> Statement Definition and
8261           Usage&#8221;</a>.
8262                   </p></dd>
8263 <dt><span class="term"><span class="command"><strong>inline-signing</strong></span></span></dt>
8264 <dd><p>
8265                     If <code class="literal">yes</code>, this enables
8266                     "bump in the wire" signing of a zone, where a
8267                     unsigned zone is transferred in or loaded from
8268                     disk and a signed version of the zone is served,
8269                     with possibly, a different serial number.  This
8270                     behaviour is disabled by default.
8271                   </p></dd>
8272 <dt><span class="term"><span class="command"><strong>multi-master</strong></span></span></dt>
8273 <dd><p>
8274                     See the description of <span class="command"><strong>multi-master</strong></span> in
8275                     <a class="xref" href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8276                   </p></dd>
8277 <dt><span class="term"><span class="command"><strong>masterfile-format</strong></span></span></dt>
8278 <dd><p>
8279                     See the description of <span class="command"><strong>masterfile-format</strong></span>
8280                     in <a class="xref" href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8281                   </p></dd>
8282 <dt><span class="term"><span class="command"><strong>dnssec-secure-to-insecure</strong></span></span></dt>
8283 <dd><p>
8284                     See the description of
8285                     <span class="command"><strong>dnssec-secure-to-insecure</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8286                   </p></dd>
8287 </dl></div>
8288 </div>
8289 <div class="section">
8290 <div class="titlepage"><div><div><h4 class="title">
8291 <a name="dynamic_update_policies"></a>Dynamic Update Policies</h4></div></div></div>
8292 <p><acronym class="acronym">BIND</acronym> 9 supports two alternative
8293               methods of granting clients the right to perform
8294               dynamic updates to a zone, configured by the
8295               <span class="command"><strong>allow-update</strong></span> and
8296               <span class="command"><strong>update-policy</strong></span> option, respectively.
8297             </p>
8298 <p>
8299               The <span class="command"><strong>allow-update</strong></span> clause works the
8300               same way as in previous versions of <acronym class="acronym">BIND</acronym>.
8301               It grants given clients the permission to update any
8302               record of any name in the zone.
8303             </p>
8304 <p>
8305               The <span class="command"><strong>update-policy</strong></span> clause
8306               allows more fine-grained control over what updates are
8307               allowed.  A set of rules is specified, where each rule
8308               either grants or denies permissions for one or more
8309               names to be updated by one or more identities.  If
8310               the dynamic update request message is signed (that is,
8311               it includes either a TSIG or SIG(0) record), the
8312               identity of the signer can be determined.
8313             </p>
8314 <p>
8315               Rules are specified in the <span class="command"><strong>update-policy</strong></span>
8316               zone option, and are only meaningful for master zones.
8317               When the <span class="command"><strong>update-policy</strong></span> statement
8318               is present, it is a configuration error for the
8319               <span class="command"><strong>allow-update</strong></span> statement to be
8320               present.  The <span class="command"><strong>update-policy</strong></span> statement
8321               only examines the signer of a message; the source
8322               address is not relevant.
8323             </p>
8324 <p>
8325               There is a pre-defined <span class="command"><strong>update-policy</strong></span>
8326               rule which can be switched on with the command
8327               <span class="command"><strong>update-policy local;</strong></span>.
8328               Switching on this rule in a zone causes
8329               <span class="command"><strong>named</strong></span> to generate a TSIG session
8330               key and place it in a file, and to allow that key
8331               to update the zone.  (By default, the file is
8332               <code class="filename">/var/run/named/session.key</code>, the key
8333               name is "local-ddns" and the key algorithm is HMAC-SHA256,
8334               but these values are configurable with the
8335               <span class="command"><strong>session-keyfile</strong></span>,
8336               <span class="command"><strong>session-keyname</strong></span> and
8337               <span class="command"><strong>session-keyalg</strong></span> options, respectively).
8338             </p>
8339 <p>
8340               A client running on the local system, and with appropriate
8341               permissions, may read that file and use the key to sign update
8342               requests.  The zone's update policy will be set to allow that
8343               key to change any record within the zone.  Assuming the
8344               key name is "local-ddns", this policy is equivalent to:
8345             </p>
8346 <pre class="programlisting">update-policy { grant local-ddns zonesub any; };
8347             </pre>
8348 <p>
8349               The command <span class="command"><strong>nsupdate -l</strong></span> sends update
8350               requests to localhost, and signs them using the session key.
8351             </p>
8352 <p>
8353               Other rule definitions look like this:
8354             </p>
8355 <pre class="programlisting">
8356 ( <span class="command"><strong>grant</strong></span> | <span class="command"><strong>deny</strong></span> ) <em class="replaceable"><code>identity</code></em> <em class="replaceable"><code>nametype</code></em> [<span class="optional"> <em class="replaceable"><code>name</code></em> </span>] [<span class="optional"> <em class="replaceable"><code>types</code></em> </span>]
8357 </pre>
8358 <p>
8359               Each rule grants or denies privileges.  Once a message has
8360               successfully matched a rule, the operation is immediately
8361               granted or denied and no further rules are examined.  A rule
8362               is matched when the signer matches the identity field, the
8363               name matches the name field in accordance with the nametype
8364               field, and the type matches the types specified in the type
8365               field.
8366             </p>
8367 <p>
8368               No signer is required for <em class="replaceable"><code>tcp-self</code></em>
8369               or <em class="replaceable"><code>6to4-self</code></em> however the standard
8370               reverse mapping / prefix conversion must match the identity
8371               field.
8372             </p>
8373 <p>
8374               The identity field specifies a name or a wildcard
8375               name.  Normally, this is the name of the TSIG or
8376               SIG(0) key used to sign the update request.  When a
8377               TKEY exchange has been used to create a shared secret,
8378               the identity of the shared secret is the same as the
8379               identity of the key used to authenticate the TKEY
8380               exchange.  TKEY is also the negotiation method used
8381               by GSS-TSIG, which establishes an identity that is
8382               the Kerberos principal of the client, such as
8383               <strong class="userinput"><code>"user@host.domain"</code></strong>.  When the
8384               <em class="replaceable"><code>identity</code></em> field specifies
8385               a wildcard name, it is subject to DNS wildcard
8386               expansion, so the rule will apply to multiple identities.
8387               The <em class="replaceable"><code>identity</code></em> field must
8388               contain a fully-qualified domain name.
8389             </p>
8390 <p>
8391               For nametypes <code class="varname">krb5-self</code>,
8392               <code class="varname">ms-self</code>, <code class="varname">krb5-subdomain</code>,
8393               and <code class="varname">ms-subdomain</code> the
8394               <em class="replaceable"><code>identity</code></em> field specifies
8395               the Windows or Kerberos realm of the machine belongs to.
8396             </p>
8397 <p>
8398               The <em class="replaceable"><code>nametype</code></em> field has 13
8399               values:
8400               <code class="varname">name</code>, <code class="varname">subdomain</code>,
8401               <code class="varname">wildcard</code>, <code class="varname">self</code>,
8402               <code class="varname">selfsub</code>, <code class="varname">selfwild</code>,
8403               <code class="varname">krb5-self</code>, <code class="varname">ms-self</code>,
8404               <code class="varname">krb5-subdomain</code>,
8405               <code class="varname">ms-subdomain</code>,
8406               <code class="varname">tcp-self</code>, <code class="varname">6to4-self</code>,
8407               <code class="varname">zonesub</code>, and <code class="varname">external</code>.
8408             </p>
8409 <div class="informaltable"><table border="1">
8410 <colgroup>
8411 <col width="0.819in" class="1">
8412 <col width="3.681in" class="2">
8413 </colgroup>
8414 <tbody>
8415 <tr>
8416 <td>
8417                       <p>
8418                         <code class="varname">name</code>
8419                       </p>
8420                     </td>
8421 <td>
8422                       <p>
8423                         Exact-match semantics.  This rule matches
8424                         when the name being updated is identical
8425                         to the contents of the
8426                         <em class="replaceable"><code>name</code></em> field.
8427                       </p>
8428                     </td>
8429 </tr>
8430 <tr>
8431 <td>
8432                       <p>
8433                         <code class="varname">subdomain</code>
8434                       </p>
8435                     </td>
8436 <td>
8437                       <p>
8438                         This rule matches when the name being updated
8439                         is a subdomain of, or identical to, the
8440                         contents of the <em class="replaceable"><code>name</code></em>
8441                         field.
8442                       </p>
8443                     </td>
8444 </tr>
8445 <tr>
8446 <td>
8447                       <p>
8448                         <code class="varname">zonesub</code>
8449                       </p>
8450                     </td>
8451 <td>
8452                       <p>
8453                         This rule is similar to subdomain, except that
8454                         it matches when the name being updated is a
8455                         subdomain of the zone in which the
8456                         <span class="command"><strong>update-policy</strong></span> statement
8457                         appears.  This obviates the need to type the zone
8458                         name twice, and enables the use of a standard
8459                         <span class="command"><strong>update-policy</strong></span> statement in
8460                         multiple zones without modification.
8461                       </p>
8462                       <p>
8463                         When this rule is used, the
8464                         <em class="replaceable"><code>name</code></em> field is omitted.
8465                       </p>
8466                     </td>
8467 </tr>
8468 <tr>
8469 <td>
8470                       <p>
8471                         <code class="varname">wildcard</code>
8472                       </p>
8473                     </td>
8474 <td>
8475                       <p>
8476                         The <em class="replaceable"><code>name</code></em> field
8477                         is subject to DNS wildcard expansion, and
8478                         this rule matches when the name being updated
8479                         is a valid expansion of the wildcard.
8480                       </p>
8481                     </td>
8482 </tr>
8483 <tr>
8484 <td>
8485                       <p>
8486                         <code class="varname">self</code>
8487                       </p>
8488                     </td>
8489 <td>
8490                       <p>
8491                         This rule matches when the name being updated
8492                         matches the contents of the
8493                         <em class="replaceable"><code>identity</code></em> field.
8494                         The <em class="replaceable"><code>name</code></em> field
8495                         is ignored, but should be the same as the
8496                         <em class="replaceable"><code>identity</code></em> field.
8497                         The <code class="varname">self</code> nametype is
8498                         most useful when allowing using one key per
8499                         name to update, where the key has the same
8500                         name as the name to be updated.  The
8501                         <em class="replaceable"><code>identity</code></em> would
8502                         be specified as <code class="constant">*</code> (an asterisk) in
8503                         this case.
8504                       </p>
8505                     </td>
8506 </tr>
8507 <tr>
8508 <td>
8509                       <p>
8510                         <code class="varname">selfsub</code>
8511                       </p>
8512                     </td>
8513 <td>
8514                       <p>
8515                         This rule is similar to <code class="varname">self</code>
8516                         except that subdomains of <code class="varname">self</code>
8517                         can also be updated.
8518                       </p>
8519                     </td>
8520 </tr>
8521 <tr>
8522 <td>
8523                       <p>
8524                         <code class="varname">selfwild</code>
8525                       </p>
8526                     </td>
8527 <td>
8528                       <p>
8529                         This rule is similar to <code class="varname">self</code>
8530                         except that only subdomains of
8531                         <code class="varname">self</code> can be updated.
8532                       </p>
8533                     </td>
8534 </tr>
8535 <tr>
8536 <td>
8537                       <p>
8538                         <code class="varname">ms-self</code>
8539                       </p>
8540                     </td>
8541 <td>
8542                       <p>
8543                         This rule takes a Windows machine principal
8544                         (machine$@REALM) for machine in REALM and
8545                         and converts it machine.realm allowing the machine
8546                         to update machine.realm.  The REALM to be matched
8547                         is specified in the <em class="replaceable"><code>identity</code></em>
8548                         field.
8549                       </p>
8550                     </td>
8551 </tr>
8552 <tr>
8553 <td>
8554                       <p>
8555                         <code class="varname">ms-subdomain</code>
8556                       </p>
8557                     </td>
8558 <td>
8559                       <p>
8560                         This rule takes a Windows machine principal
8561                         (machine$@REALM) for machine in REALM and
8562                         converts it to machine.realm allowing the machine
8563                         to update subdomains of machine.realm.  The REALM
8564                         to be matched is specified in the
8565                         <em class="replaceable"><code>identity</code></em> field.
8566                       </p>
8567                     </td>
8568 </tr>
8569 <tr>
8570 <td>
8571                       <p>
8572                         <code class="varname">krb5-self</code>
8573                       </p>
8574                     </td>
8575 <td>
8576                       <p>
8577                         This rule takes a Kerberos machine principal
8578                         (host/machine@REALM) for machine in REALM and
8579                         and converts it machine.realm allowing the machine
8580                         to update machine.realm.  The REALM to be matched
8581                         is specified in the <em class="replaceable"><code>identity</code></em>
8582                         field.
8583                       </p>
8584                     </td>
8585 </tr>
8586 <tr>
8587 <td>
8588                       <p>
8589                         <code class="varname">krb5-subdomain</code>
8590                       </p>
8591                     </td>
8592 <td>
8593                       <p>
8594                         This rule takes a Kerberos machine principal
8595                         (host/machine@REALM) for machine in REALM and
8596                         converts it to machine.realm allowing the machine
8597                         to update subdomains of machine.realm.  The REALM
8598                         to be matched is specified in the
8599                         <em class="replaceable"><code>identity</code></em> field.
8600                       </p>
8601                     </td>
8602 </tr>
8603 <tr>
8604 <td>
8605                       <p>
8606                         <code class="varname">tcp-self</code>
8607                       </p>
8608                     </td>
8609 <td>
8610                       <p>
8611                         Allow updates that have been sent via TCP and
8612                         for which the standard mapping from the initiating
8613                         IP address into the IN-ADDR.ARPA and IP6.ARPA
8614                         namespaces match the name to be updated.
8615                       </p>
8616                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
8617 <h3 class="title">Note</h3>
8618                         It is theoretically possible to spoof these TCP
8619                         sessions.
8620                       </div>
8621                     </td>
8622 </tr>
8623 <tr>
8624 <td>
8625                       <p>
8626                         <code class="varname">6to4-self</code>
8627                       </p>
8628                     </td>
8629 <td>
8630                       <p>
8631                         Allow the 6to4 prefix to be update by any TCP
8632                         connection from the 6to4 network or from the
8633                         corresponding IPv4 address.  This is intended
8634                         to allow NS or DNAME RRsets to be added to the
8635                         reverse tree.
8636                       </p>
8637                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
8638 <h3 class="title">Note</h3>
8639                         It is theoretically possible to spoof these TCP
8640                         sessions.
8641                       </div>
8642                     </td>
8643 </tr>
8644 <tr>
8645 <td>
8646                       <p>
8647                         <code class="varname">external</code>
8648                       </p>
8649                     </td>
8650 <td>
8651                       <p>
8652                         This rule allows <span class="command"><strong>named</strong></span>
8653                         to defer the decision of whether to allow a
8654                         given update to an external daemon.
8655                       </p>
8656                       <p>
8657                         The method of communicating with the daemon is
8658                         specified in the <em class="replaceable"><code>identity</code></em>
8659                         field, the format of which is
8660                         "<code class="constant">local:</code><em class="replaceable"><code>path</code></em>",
8661                         where <em class="replaceable"><code>path</code></em> is the location
8662                         of a UNIX-domain socket.  (Currently, "local" is the
8663                         only supported mechanism.)
8664                       </p>
8665                       <p>
8666                         Requests to the external daemon are sent over the
8667                         UNIX-domain socket as datagrams with the following
8668                         format:
8669                       </p>
8670                       <pre class="programlisting">
8671    Protocol version number (4 bytes, network byte order, currently 1)
8672    Request length (4 bytes, network byte order)
8673    Signer (null-terminated string)
8674    Name (null-terminated string)
8675    TCP source address (null-terminated string)
8676    Rdata type (null-terminated string)
8677    Key (null-terminated string)
8678    TKEY token length (4 bytes, network byte order)
8679    TKEY token (remainder of packet)</pre>
8680                       <p>
8681                         The daemon replies with a four-byte value in
8682                         network byte order, containing either 0 or 1; 0
8683                         indicates that the specified update is not
8684                         permitted, and 1 indicates that it is.
8685                       </p>
8686                     </td>
8687 </tr>
8688 </tbody>
8689 </table></div>
8690 <p>
8691               In all cases, the <em class="replaceable"><code>name</code></em>
8692               field must specify a fully-qualified domain name.
8693             </p>
8694 <p>
8695               If no types are explicitly specified, this rule matches
8696               all types except RRSIG, NS, SOA, NSEC and NSEC3. Types
8697               may be specified by name, including "ANY" (ANY matches
8698               all types except NSEC and NSEC3, which can never be
8699               updated).  Note that when an attempt is made to delete
8700               all records associated with a name, the rules are
8701               checked for each existing record type.
8702             </p>
8703 </div>
8704 </div>
8705 </div>
8706 <div class="section">
8707 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
8708 <a name="zone_file"></a>Zone File</h2></div></div></div>
8709 <div class="section">
8710 <div class="titlepage"><div><div><h3 class="title">
8711 <a name="types_of_resource_records_and_when_to_use_them"></a>Types of Resource Records and When to Use Them</h3></div></div></div>
8712 <p>
8713             This section, largely borrowed from RFC 1034, describes the
8714             concept of a Resource Record (RR) and explains when each is used.
8715             Since the publication of RFC 1034, several new RRs have been
8716             identified
8717             and implemented in the DNS. These are also included.
8718           </p>
8719 <div class="section">
8720 <div class="titlepage"><div><div><h4 class="title">
8721 <a name="id-1.7.6.2.3"></a>Resource Records</h4></div></div></div>
8722 <p>
8723               A domain name identifies a node.  Each node has a set of
8724               resource information, which may be empty.  The set of resource
8725               information associated with a particular name is composed of
8726               separate RRs. The order of RRs in a set is not significant and
8727               need not be preserved by name servers, resolvers, or other
8728               parts of the DNS. However, sorting of multiple RRs is
8729               permitted for optimization purposes, for example, to specify
8730               that a particular nearby server be tried first. See <a class="xref" href="Bv9ARM.ch06.html#the_sortlist_statement" title="The sortlist Statement">the section called &#8220;The <span class="command"><strong>sortlist</strong></span> Statement&#8221;</a> and <a class="xref" href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">the section called &#8220;RRset Ordering&#8221;</a>.
8731             </p>
8732 <p>
8733               The components of a Resource Record are:
8734             </p>
8735 <div class="informaltable"><table border="1">
8736 <colgroup>
8737 <col width="1.000in" class="1">
8738 <col width="3.500in" class="2">
8739 </colgroup>
8740 <tbody>
8741 <tr>
8742 <td>
8743                       <p>
8744                         owner name
8745                       </p>
8746                     </td>
8747 <td>
8748                       <p>
8749                         The domain name where the RR is found.
8750                       </p>
8751                     </td>
8752 </tr>
8753 <tr>
8754 <td>
8755                       <p>
8756                         type
8757                       </p>
8758                     </td>
8759 <td>
8760                       <p>
8761                         An encoded 16-bit value that specifies
8762                         the type of the resource record.
8763                       </p>
8764                     </td>
8765 </tr>
8766 <tr>
8767 <td>
8768                       <p>
8769                         TTL
8770                       </p>
8771                     </td>
8772 <td>
8773                       <p>
8774                         The time-to-live of the RR. This field
8775                         is a 32-bit integer in units of seconds, and is
8776                         primarily used by
8777                         resolvers when they cache RRs. The TTL describes how
8778                         long a RR can
8779                         be cached before it should be discarded.
8780                       </p>
8781                     </td>
8782 </tr>
8783 <tr>
8784 <td>
8785                       <p>
8786                         class
8787                       </p>
8788                     </td>
8789 <td>
8790                       <p>
8791                         An encoded 16-bit value that identifies
8792                         a protocol family or instance of a protocol.
8793                       </p>
8794                     </td>
8795 </tr>
8796 <tr>
8797 <td>
8798                       <p>
8799                         RDATA
8800                       </p>
8801                     </td>
8802 <td>
8803                       <p>
8804                         The resource data.  The format of the
8805                         data is type (and sometimes class) specific.
8806                       </p>
8807                     </td>
8808 </tr>
8809 </tbody>
8810 </table></div>
8811 <p>
8812               The following are <span class="emphasis"><em>types</em></span> of valid RRs:
8813             </p>
8814 <div class="informaltable"><table border="1">
8815 <colgroup>
8816 <col width="0.875in" class="1">
8817 <col width="3.625in" class="2">
8818 </colgroup>
8819 <tbody>
8820 <tr>
8821 <td>
8822                       <p>
8823                         A
8824                       </p>
8825                     </td>
8826 <td>
8827                       <p>
8828                         A host address.  In the IN class, this is a
8829                         32-bit IP address.  Described in RFC 1035.
8830                       </p>
8831                     </td>
8832 </tr>
8833 <tr>
8834 <td>
8835                       <p>
8836                         AAAA
8837                       </p>
8838                     </td>
8839 <td>
8840                       <p>
8841                         IPv6 address.  Described in RFC 1886.
8842                       </p>
8843                     </td>
8844 </tr>
8845 <tr>
8846 <td>
8847                       <p>
8848                         A6
8849                       </p>
8850                     </td>
8851 <td>
8852                       <p>
8853                         IPv6 address.  This can be a partial
8854                         address (a suffix) and an indirection to the name
8855                         where the rest of the
8856                         address (the prefix) can be found.  Experimental.
8857                         Described in RFC 2874.
8858                       </p>
8859                     </td>
8860 </tr>
8861 <tr>
8862 <td>
8863                       <p>
8864                         AFSDB
8865                       </p>
8866                     </td>
8867 <td>
8868                       <p>
8869                         Location of AFS database servers.
8870                         Experimental.  Described in RFC 1183.
8871                       </p>
8872                     </td>
8873 </tr>
8874 <tr>
8875 <td>
8876                       <p>
8877                         APL
8878                       </p>
8879                     </td>
8880 <td>
8881                       <p>
8882                         Address prefix list.  Experimental.
8883                         Described in RFC 3123.
8884                       </p>
8885                     </td>
8886 </tr>
8887 <tr>
8888 <td>
8889                       <p>
8890                         ATMA
8891                       </p>
8892                     </td>
8893 <td>
8894                       <p>
8895                         ATM Address.
8896                       </p>
8897                     </td>
8898 </tr>
8899 <tr>
8900 <td>
8901                       <p>
8902                         AVC
8903                       </p>
8904                     </td>
8905 <td>
8906                       <p>
8907                         Application Visibility and Control record.
8908                       </p>
8909                     </td>
8910 </tr>
8911 <tr>
8912 <td>
8913                       <p>
8914                         CAA
8915                       </p>
8916                     </td>
8917 <td>
8918                       <p>
8919                         Identifies which Certificate Authorities can issue
8920                         certificates for this domain and what rules they
8921                         need to follow when doing so. Defined in RFC 6844.
8922                       </p>
8923                     </td>
8924 </tr>
8925 <tr>
8926 <td>
8927                       <p>
8928                         CDNSKEY
8929                       </p>
8930                     </td>
8931 <td>
8932                       <p>
8933                         Identifies which DNSKEY records should be published
8934                         as DS records in the parent zone.
8935                       </p>
8936                     </td>
8937 </tr>
8938 <tr>
8939 <td>
8940                       <p>
8941                         CDS
8942                       </p>
8943                     </td>
8944 <td>
8945                       <p>
8946                         Contains the set of DS records that should be published
8947                         by the parent zone.
8948                       </p>
8949                     </td>
8950 </tr>
8951 <tr>
8952 <td>
8953                       <p>
8954                         CERT
8955                       </p>
8956                     </td>
8957 <td>
8958                       <p>
8959                         Holds a digital certificate.
8960                         Described in RFC 2538.
8961                       </p>
8962                     </td>
8963 </tr>
8964 <tr>
8965 <td>
8966                       <p>
8967                         CNAME
8968                       </p>
8969                     </td>
8970 <td>
8971                       <p>
8972                         Identifies the canonical name of an alias.
8973                         Described in RFC 1035.
8974                       </p>
8975                     </td>
8976 </tr>
8977 <tr>
8978 <td>
8979                       <p>
8980                         CSYNC
8981                       </p>
8982                     </td>
8983 <td>
8984                       <p>
8985                         Child-to-Parent Synchronization in DNS as described
8986                         in RFC 7477.
8987                       </p>
8988                     </td>
8989 </tr>
8990 <tr>
8991 <td>
8992                       <p>
8993                         DHCID
8994                       </p>
8995                     </td>
8996 <td>
8997                       <p>
8998                         Is used for identifying which DHCP client is
8999                         associated with this name.  Described in RFC 4701.
9000                       </p>
9001                     </td>
9002 </tr>
9003 <tr>
9004 <td>
9005                       <p>
9006                         DLV
9007                       </p>
9008                     </td>
9009 <td>
9010                       <p>
9011                         A DNS Look-aside Validation record which contains
9012                         the records that are used as trust anchors for
9013                         zones in a DLV namespace.  Described in RFC 4431.
9014                       </p>
9015                     </td>
9016 </tr>
9017 <tr>
9018 <td>
9019                       <p>
9020                         DNAME
9021                       </p>
9022                     </td>
9023 <td>
9024                       <p>
9025                         Replaces the domain name specified with
9026                         another name to be looked up, effectively aliasing an
9027                         entire
9028                         subtree of the domain name space rather than a single
9029                         record
9030                         as in the case of the CNAME RR.
9031                         Described in RFC 2672.
9032                       </p>
9033                     </td>
9034 </tr>
9035 <tr>
9036 <td>
9037                       <p>
9038                         DNSKEY
9039                       </p>
9040                     </td>
9041 <td>
9042                       <p>
9043                         Stores a public key associated with a signed
9044                         DNS zone.  Described in RFC 4034.
9045                       </p>
9046                     </td>
9047 </tr>
9048 <tr>
9049 <td>
9050                       <p>
9051                         DS
9052                       </p>
9053                     </td>
9054 <td>
9055                       <p>
9056                         Stores the hash of a public key associated with a
9057                         signed DNS zone.  Described in RFC 4034.
9058                       </p>
9059                     </td>
9060 </tr>
9061 <tr>
9062 <td>
9063                       <p>
9064                         EID
9065                       </p>
9066                     </td>
9067 <td>
9068                       <p>
9069                         End Point Identifier.
9070                       </p>
9071                     </td>
9072 </tr>
9073 <tr>
9074 <td>
9075                       <p>
9076                         EUI48
9077                       </p>
9078                     </td>
9079 <td>
9080                       <p>
9081                         A 48-bit EUI address. Described in RFC 7043.
9082                       </p>
9083                     </td>
9084 </tr>
9085 <tr>
9086 <td>
9087                       <p>
9088                         EUI64
9089                       </p>
9090                     </td>
9091 <td>
9092                       <p>
9093                         A 64-bit EUI address. Described in RFC 7043.
9094                       </p>
9095                     </td>
9096 </tr>
9097 <tr>
9098 <td>
9099                       <p>
9100                         GID
9101                       </p>
9102                     </td>
9103 <td>
9104                       <p>
9105                         Reserved.
9106                       </p>
9107                     </td>
9108 </tr>
9109 <tr>
9110 <td>
9111                       <p>
9112                         GPOS
9113                       </p>
9114                     </td>
9115 <td>
9116                       <p>
9117                         Specifies the global position.  Superseded by LOC.
9118                       </p>
9119                     </td>
9120 </tr>
9121 <tr>
9122 <td>
9123                       <p>
9124                         HINFO
9125                       </p>
9126                     </td>
9127 <td>
9128                       <p>
9129                         Identifies the CPU and OS used by a host.
9130                         Described in RFC 1035.
9131                       </p>
9132                     </td>
9133 </tr>
9134 <tr>
9135 <td>
9136                       <p>
9137                         HIP
9138                       </p>
9139                     </td>
9140 <td>
9141                       <p>
9142                         Host Identity Protocol Address.
9143                         Described in RFC 5205.
9144                       </p>
9145                     </td>
9146 </tr>
9147 <tr>
9148 <td>
9149                       <p>
9150                         IPSECKEY
9151                       </p>
9152                     </td>
9153 <td>
9154                       <p>
9155                         Provides a method for storing IPsec keying material in
9156                         DNS.  Described in RFC 4025.
9157                       </p>
9158                     </td>
9159 </tr>
9160 <tr>
9161 <td>
9162                       <p>
9163                         ISDN
9164                       </p>
9165                     </td>
9166 <td>
9167                       <p>
9168                         Representation of ISDN addresses.
9169                         Experimental.  Described in RFC 1183.
9170                       </p>
9171                     </td>
9172 </tr>
9173 <tr>
9174 <td>
9175                       <p>
9176                         KEY
9177                       </p>
9178                     </td>
9179 <td>
9180                       <p>
9181                         Stores a public key associated with a
9182                         DNS name.  Used in original DNSSEC; replaced
9183                         by DNSKEY in DNSSECbis, but still used with
9184                         SIG(0).  Described in RFCs 2535 and 2931.
9185                       </p>
9186                     </td>
9187 </tr>
9188 <tr>
9189 <td>
9190                       <p>
9191                         KX
9192                       </p>
9193                     </td>
9194 <td>
9195                       <p>
9196                         Identifies a key exchanger for this
9197                         DNS name.  Described in RFC 2230.
9198                       </p>
9199                     </td>
9200 </tr>
9201 <tr>
9202 <td>
9203                       <p>
9204                         L32
9205                       </p>
9206                     </td>
9207 <td>
9208                       <p>
9209                         Holds 32-bit Locator values for
9210                         Identifier-Locator Network Protocol. Described
9211                         in RFC 6742.
9212                       </p>
9213                     </td>
9214 </tr>
9215 <tr>
9216 <td>
9217                       <p>
9218                         L64
9219                       </p>
9220                     </td>
9221 <td>
9222                       <p>
9223                         Holds 64-bit Locator values for
9224                         Identifier-Locator Network Protocol. Described
9225                         in RFC 6742.
9226                       </p>
9227                     </td>
9228 </tr>
9229 <tr>
9230 <td>
9231                       <p>
9232                         LOC
9233                       </p>
9234                     </td>
9235 <td>
9236                       <p>
9237                         For storing GPS info.  Described in RFC 1876.
9238                         Experimental.
9239                       </p>
9240                     </td>
9241 </tr>
9242 <tr>
9243 <td>
9244                       <p>
9245                         LP
9246                       </p>
9247                     </td>
9248 <td>
9249                       <p>
9250                         Identifier-Locator Network Protocol.
9251                         Described in RFC 6742.
9252                       </p>
9253                     </td>
9254 </tr>
9255 <tr>
9256 <td>
9257                       <p>
9258                         MB
9259                       </p>
9260                     </td>
9261 <td>
9262                       <p>
9263                         Mail Box.  Historical.
9264                       </p>
9265                     </td>
9266 </tr>
9267 <tr>
9268 <td>
9269                       <p>
9270                         MD
9271                       </p>
9272                     </td>
9273 <td>
9274                       <p>
9275                         Mail Destination.  Historical.
9276                       </p>
9277                     </td>
9278 </tr>
9279 <tr>
9280 <td>
9281                       <p>
9282                         MF
9283                       </p>
9284                     </td>
9285 <td>
9286                       <p>
9287                         Mail Forwarder.  Historical.
9288                       </p>
9289                     </td>
9290 </tr>
9291 <tr>
9292 <td>
9293                       <p>
9294                         MG
9295                       </p>
9296                     </td>
9297 <td>
9298                       <p>
9299                         Mail Group.  Historical.
9300                       </p>
9301                     </td>
9302 </tr>
9303 <tr>
9304 <td>
9305                       <p>
9306                         MINFO
9307                       </p>
9308                     </td>
9309 <td>
9310                       <p>
9311                         Mail Information.
9312                       </p>
9313                     </td>
9314 </tr>
9315 <tr>
9316 <td>
9317                       <p>
9318                         MR
9319                       </p>
9320                     </td>
9321 <td>
9322                       <p>
9323                         Mail Rename. Historical.
9324                       </p>
9325                     </td>
9326 </tr>
9327 <tr>
9328 <td>
9329                       <p>
9330                         MX
9331                       </p>
9332                     </td>
9333 <td>
9334                       <p>
9335                         Identifies a mail exchange for the domain with
9336                         a 16-bit preference value (lower is better)
9337                         followed by the host name of the mail exchange.
9338                         Described in RFC 974, RFC 1035.
9339                       </p>
9340                     </td>
9341 </tr>
9342 <tr>
9343 <td>
9344                       <p>
9345                         NAPTR
9346                       </p>
9347                     </td>
9348 <td>
9349                       <p>
9350                         Name authority pointer.  Described in RFC 2915.
9351                       </p>
9352                     </td>
9353 </tr>
9354 <tr>
9355 <td>
9356                       <p>
9357                         NID
9358                       </p>
9359                     </td>
9360 <td>
9361                       <p>
9362                         Holds values for Node Identifiers in
9363                         Identifier-Locator Network Protocol. Described
9364                         in RFC 6742.
9365                       </p>
9366                     </td>
9367 </tr>
9368 <tr>
9369 <td>
9370                       <p>
9371                         NINFO
9372                       </p>
9373                     </td>
9374 <td>
9375                       <p>
9376                         Contains zone status information.
9377                       </p>
9378                     </td>
9379 </tr>
9380 <tr>
9381 <td>
9382                       <p>
9383                         NIMLOC
9384                       </p>
9385                     </td>
9386 <td>
9387                       <p>
9388                         Nimrod Locator.
9389                       </p>
9390                     </td>
9391 </tr>
9392 <tr>
9393 <td>
9394                       <p>
9395                         NSAP
9396                       </p>
9397                     </td>
9398 <td>
9399                       <p>
9400                         A network service access point.
9401                         Described in RFC 1706.
9402                       </p>
9403                     </td>
9404 </tr>
9405 <tr>
9406 <td>
9407                       <p>
9408                         NSAP-PTR
9409                       </p>
9410                     </td>
9411 <td>
9412                       <p>
9413                         Historical.
9414                       </p>
9415                     </td>
9416 </tr>
9417 <tr>
9418 <td>
9419                       <p>
9420                         NS
9421                       </p>
9422                     </td>
9423 <td>
9424                       <p>
9425                         The authoritative name server for the
9426                         domain.  Described in RFC 1035.
9427                       </p>
9428                     </td>
9429 </tr>
9430 <tr>
9431 <td>
9432                       <p>
9433                         NSEC
9434                       </p>
9435                     </td>
9436 <td>
9437                       <p>
9438                         Used in DNSSECbis to securely indicate that
9439                         RRs with an owner name in a certain name interval do
9440                         not exist in
9441                         a zone and indicate what RR types are present for an
9442                         existing name.
9443                         Described in RFC 4034.
9444                       </p>
9445                     </td>
9446 </tr>
9447 <tr>
9448 <td>
9449                       <p>
9450                         NSEC3
9451                       </p>
9452                     </td>
9453 <td>
9454                       <p>
9455                         Used in DNSSECbis to securely indicate that
9456                         RRs with an owner name in a certain name
9457                         interval do not exist in a zone and indicate
9458                         what RR types are present for an existing
9459                         name.  NSEC3 differs from NSEC in that it
9460                         prevents zone enumeration but is more
9461                         computationally expensive on both the server
9462                         and the client than NSEC.  Described in RFC
9463                         5155.
9464                       </p>
9465                     </td>
9466 </tr>
9467 <tr>
9468 <td>
9469                       <p>
9470                         NSEC3PARAM
9471                       </p>
9472                     </td>
9473 <td>
9474                       <p>
9475                         Used in DNSSECbis to tell the authoritative
9476                         server which NSEC3 chains are available to use.
9477                         Described in RFC 5155.
9478                       </p>
9479                     </td>
9480 </tr>
9481 <tr>
9482 <td>
9483                       <p>
9484                         NULL
9485                       </p>
9486                     </td>
9487 <td>
9488                       <p>
9489                         This is an opaque container.
9490                       </p>
9491                     </td>
9492 </tr>
9493 <tr>
9494 <td>
9495                       <p>
9496                         NXT
9497                       </p>
9498                     </td>
9499 <td>
9500                       <p>
9501                         Used in DNSSEC to securely indicate that
9502                         RRs with an owner name in a certain name interval do
9503                         not exist in
9504                         a zone and indicate what RR types are present for an
9505                         existing name.
9506                         Used in original DNSSEC; replaced by NSEC in
9507                         DNSSECbis.
9508                         Described in RFC 2535.
9509                       </p>
9510                     </td>
9511 </tr>
9512 <tr>
9513 <td>
9514                       <p>
9515                         OPENPGPKEY
9516                       </p>
9517                     </td>
9518 <td>
9519                       <p>
9520                         Used to hold an OPENPGPKEY.
9521                       </p>
9522                     </td>
9523 </tr>
9524 <tr>
9525 <td>
9526                       <p>
9527                         PTR
9528                       </p>
9529                     </td>
9530 <td>
9531                       <p>
9532                         A pointer to another part of the domain
9533                         name space.  Described in RFC 1035.
9534                       </p>
9535                     </td>
9536 </tr>
9537 <tr>
9538 <td>
9539                       <p>
9540                         PX
9541                       </p>
9542                     </td>
9543 <td>
9544                       <p>
9545                         Provides mappings between RFC 822 and X.400
9546                         addresses.  Described in RFC 2163.
9547                       </p>
9548                     </td>
9549 </tr>
9550 <tr>
9551 <td>
9552                       <p>
9553                         RKEY
9554                       </p>
9555                     </td>
9556 <td>
9557                       <p>
9558                         Resource key.
9559                       </p>
9560                     </td>
9561 </tr>
9562 <tr>
9563 <td>
9564                       <p>
9565                         RP
9566                       </p>
9567                     </td>
9568 <td>
9569                       <p>
9570                         Information on persons responsible
9571                         for the domain.  Experimental.  Described in RFC 1183.
9572                       </p>
9573                     </td>
9574 </tr>
9575 <tr>
9576 <td>
9577                       <p>
9578                         RRSIG
9579                       </p>
9580                     </td>
9581 <td>
9582                       <p>
9583                         Contains DNSSECbis signature data.  Described
9584                         in RFC 4034.
9585                       </p>
9586                     </td>
9587 </tr>
9588 <tr>
9589 <td>
9590                       <p>
9591                         RT
9592                       </p>
9593                     </td>
9594 <td>
9595                       <p>
9596                         Route-through binding for hosts that
9597                         do not have their own direct wide area network
9598                         addresses.
9599                         Experimental.  Described in RFC 1183.
9600                       </p>
9601                     </td>
9602 </tr>
9603 <tr>
9604 <td>
9605                       <p>
9606                         SIG
9607                       </p>
9608                     </td>
9609 <td>
9610                       <p>
9611                         Contains DNSSEC signature data.  Used in
9612                         original DNSSEC; replaced by RRSIG in
9613                         DNSSECbis, but still used for SIG(0).
9614                         Described in RFCs 2535 and 2931.
9615                       </p>
9616                     </td>
9617 </tr>
9618 <tr>
9619 <td>
9620                       <p>
9621                         SINK
9622                       </p>
9623                     </td>
9624 <td>
9625                       <p>
9626                         The kitchen sink record.
9627                       </p>
9628                     </td>
9629 </tr>
9630 <tr>
9631 <td>
9632                       <p>
9633                         SMIMEA
9634                       </p>
9635                     </td>
9636 <td>
9637                       <p>
9638                         The S/MIME Security Certificate Association.
9639                       </p>
9640                     </td>
9641 </tr>
9642 <tr>
9643 <td>
9644                       <p>
9645                         SOA
9646                       </p>
9647                     </td>
9648 <td>
9649                       <p>
9650                         Identifies the start of a zone of authority.
9651                         Described in RFC 1035.
9652                       </p>
9653                     </td>
9654 </tr>
9655 <tr>
9656 <td>
9657                       <p>
9658                         SPF
9659                       </p>
9660                     </td>
9661 <td>
9662                       <p>
9663                         Contains the Sender Policy Framework information
9664                         for a given email domain.  Described in RFC 4408.
9665                       </p>
9666                     </td>
9667 </tr>
9668 <tr>
9669 <td>
9670                       <p>
9671                         SRV
9672                       </p>
9673                     </td>
9674 <td>
9675                       <p>
9676                         Information about well known network
9677                         services (replaces WKS).  Described in RFC 2782.
9678                       </p>
9679                     </td>
9680 </tr>
9681 <tr>
9682 <td>
9683                       <p>
9684                         SSHFP
9685                       </p>
9686                     </td>
9687 <td>
9688                       <p>
9689                         Provides a way to securely publish a secure shell key's
9690                         fingerprint.  Described in RFC 4255.
9691                       </p>
9692                     </td>
9693 </tr>
9694 <tr>
9695 <td>
9696                       <p>
9697                         TA
9698                       </p>
9699                     </td>
9700 <td>
9701                       <p>
9702                         Trust Anchor. Experimental.
9703                       </p>
9704                     </td>
9705 </tr>
9706 <tr>
9707 <td>
9708                       <p>
9709                         TALINK
9710                       </p>
9711                     </td>
9712 <td>
9713                       <p>
9714                         Trust Anchor Link.  Experimental.
9715                       </p>
9716                     </td>
9717 </tr>
9718 <tr>
9719 <td>
9720                       <p>
9721                         TLSA
9722                       </p>
9723                     </td>
9724 <td>
9725                       <p>
9726                         Transport Layer Security Certificate Association.
9727                         Described in RFC 6698.
9728                       </p>
9729                     </td>
9730 </tr>
9731 <tr>
9732 <td>
9733                       <p>
9734                         TXT
9735                       </p>
9736                     </td>
9737 <td>
9738                       <p>
9739                         Text records.  Described in RFC 1035.
9740                       </p>
9741                     </td>
9742 </tr>
9743 <tr>
9744 <td>
9745                       <p>
9746                         UID
9747                       </p>
9748                     </td>
9749 <td>
9750                       <p>
9751                         Reserved.
9752                       </p>
9753                     </td>
9754 </tr>
9755 <tr>
9756 <td>
9757                       <p>
9758                         UINFO
9759                       </p>
9760                     </td>
9761 <td>
9762                       <p>
9763                         Reserved.
9764                       </p>
9765                     </td>
9766 </tr>
9767 <tr>
9768 <td>
9769                       <p>
9770                         UNSPEC
9771                       </p>
9772                     </td>
9773 <td>
9774                       <p>
9775                         Reserved. Historical.
9776                       </p>
9777                     </td>
9778 </tr>
9779 <tr>
9780 <td>
9781                       <p>
9782                         URI
9783                       </p>
9784                     </td>
9785 <td>
9786                       <p>
9787                         Holds a URI. Described in RFC 7553.
9788                       </p>
9789                     </td>
9790 </tr>
9791 <tr>
9792 <td>
9793                       <p>
9794                         WKS
9795                       </p>
9796                     </td>
9797 <td>
9798                       <p>
9799                         Information about which well known
9800                         network services, such as SMTP, that a domain
9801                         supports. Historical.
9802                       </p>
9803                     </td>
9804 </tr>
9805 <tr>
9806 <td>
9807                       <p>
9808                         X25
9809                       </p>
9810                     </td>
9811 <td>
9812                       <p>
9813                         Representation of X.25 network addresses.
9814                         Experimental.  Described in RFC 1183.
9815                       </p>
9816                     </td>
9817 </tr>
9818 </tbody>
9819 </table></div>
9820 <p>
9821               The following <span class="emphasis"><em>classes</em></span> of resource records
9822               are currently valid in the DNS:
9823             </p>
9824 <div class="informaltable"><table border="1">
9825 <colgroup>
9826 <col width="0.875in" class="1">
9827 <col width="3.625in" class="2">
9828 </colgroup>
9829 <tbody>
9830 <tr>
9831 <td>
9832                       <p>
9833                         IN
9834                       </p>
9835                     </td>
9836 <td>
9837                       <p>
9838                         The Internet.
9839                       </p>
9840                     </td>
9841 </tr>
9842 <tr>
9843 <td>
9844                       <p>
9845                         CH
9846                       </p>
9847                     </td>
9848 <td>
9849                       <p>
9850                         Chaosnet, a LAN protocol created at MIT in the
9851                         mid-1970s.
9852                         Rarely used for its historical purpose, but reused for
9853                         BIND's
9854                         built-in server information zones, e.g.,
9855                         <code class="literal">version.bind</code>.
9856                       </p>
9857                     </td>
9858 </tr>
9859 <tr>
9860 <td>
9861                       <p>
9862                         HS
9863                       </p>
9864                     </td>
9865 <td>
9866                       <p>
9867                         Hesiod, an information service
9868                         developed by MIT's Project Athena. It is used to share
9869                         information
9870                         about various systems databases, such as users,
9871                         groups, printers
9872                         and so on.
9873                       </p>
9874                     </td>
9875 </tr>
9876 </tbody>
9877 </table></div>
9878 <p>
9879               The owner name is often implicit, rather than forming an
9880               integral
9881               part of the RR.  For example, many name servers internally form
9882               tree
9883               or hash structures for the name space, and chain RRs off nodes.
9884               The remaining RR parts are the fixed header (type, class, TTL)
9885               which is consistent for all RRs, and a variable part (RDATA)
9886               that
9887               fits the needs of the resource being described.
9888             </p>
9889 <p>
9890               The meaning of the TTL field is a time limit on how long an
9891               RR can be kept in a cache.  This limit does not apply to
9892               authoritative
9893               data in zones; it is also timed out, but by the refreshing
9894               policies
9895               for the zone.  The TTL is assigned by the administrator for the
9896               zone where the data originates.  While short TTLs can be used to
9897               minimize caching, and a zero TTL prohibits caching, the
9898               realities
9899               of Internet performance suggest that these times should be on
9900               the
9901               order of days for the typical host.  If a change can be
9902               anticipated,
9903               the TTL can be reduced prior to the change to minimize
9904               inconsistency
9905               during the change, and then increased back to its former value
9906               following
9907               the change.
9908             </p>
9909 <p>
9910               The data in the RDATA section of RRs is carried as a combination
9911               of binary strings and domain names.  The domain names are
9912               frequently
9913               used as "pointers" to other data in the DNS.
9914             </p>
9915 </div>
9916 <div class="section">
9917 <div class="titlepage"><div><div><h4 class="title">
9918 <a name="rr_text"></a>Textual expression of RRs</h4></div></div></div>
9919 <p>
9920               RRs are represented in binary form in the packets of the DNS
9921               protocol, and are usually represented in highly encoded form
9922               when
9923               stored in a name server or resolver.  In the examples provided
9924               in
9925               RFC 1034, a style similar to that used in master files was
9926               employed
9927               in order to show the contents of RRs.  In this format, most RRs
9928               are shown on a single line, although continuation lines are
9929               possible
9930               using parentheses.
9931             </p>
9932 <p>
9933               The start of the line gives the owner of the RR.  If a line
9934               begins with a blank, then the owner is assumed to be the same as
9935               that of the previous RR.  Blank lines are often included for
9936               readability.
9937             </p>
9938 <p>
9939               Following the owner, we list the TTL, type, and class of the
9940               RR.  Class and type use the mnemonics defined above, and TTL is
9941               an integer before the type field.  In order to avoid ambiguity
9942               in
9943               parsing, type and class mnemonics are disjoint, TTLs are
9944               integers,
9945               and the type mnemonic is always last. The IN class and TTL
9946               values
9947               are often omitted from examples in the interests of clarity.
9948             </p>
9949 <p>
9950               The resource data or RDATA section of the RR are given using
9951               knowledge of the typical representation for the data.
9952             </p>
9953 <p>
9954               For example, we might show the RRs carried in a message as:
9955             </p>
9956 <div class="informaltable"><table border="1">
9957 <colgroup>
9958 <col width="1.381in" class="1">
9959 <col width="1.020in" class="2">
9960 <col width="2.099in" class="3">
9961 </colgroup>
9962 <tbody>
9963 <tr>
9964 <td>
9965                       <p>
9966                         <code class="literal">ISI.EDU.</code>
9967                       </p>
9968                     </td>
9969 <td>
9970                       <p>
9971                         <code class="literal">MX</code>
9972                       </p>
9973                     </td>
9974 <td>
9975                       <p>
9976                         <code class="literal">10 VENERA.ISI.EDU.</code>
9977                       </p>
9978                     </td>
9979 </tr>
9980 <tr>
9981 <td>
9982                       <p></p>
9983                     </td>
9984 <td>
9985                       <p>
9986                         <code class="literal">MX</code>
9987                       </p>
9988                     </td>
9989 <td>
9990                       <p>
9991                         <code class="literal">10 VAXA.ISI.EDU</code>
9992                       </p>
9993                     </td>
9994 </tr>
9995 <tr>
9996 <td>
9997                       <p>
9998                         <code class="literal">VENERA.ISI.EDU</code>
9999                       </p>
10000                     </td>
10001 <td>
10002                       <p>
10003                         <code class="literal">A</code>
10004                       </p>
10005                     </td>
10006 <td>
10007                       <p>
10008                         <code class="literal">128.9.0.32</code>
10009                       </p>
10010                     </td>
10011 </tr>
10012 <tr>
10013 <td>
10014                       <p></p>
10015                     </td>
10016 <td>
10017                       <p>
10018                         <code class="literal">A</code>
10019                       </p>
10020                     </td>
10021 <td>
10022                       <p>
10023                         <code class="literal">10.1.0.52</code>
10024                       </p>
10025                     </td>
10026 </tr>
10027 <tr>
10028 <td>
10029                       <p>
10030                         <code class="literal">VAXA.ISI.EDU</code>
10031                       </p>
10032                     </td>
10033 <td>
10034                       <p>
10035                         <code class="literal">A</code>
10036                       </p>
10037                     </td>
10038 <td>
10039                       <p>
10040                         <code class="literal">10.2.0.27</code>
10041                       </p>
10042                     </td>
10043 </tr>
10044 <tr>
10045 <td>
10046                       <p></p>
10047                     </td>
10048 <td>
10049                       <p>
10050                         <code class="literal">A</code>
10051                       </p>
10052                     </td>
10053 <td>
10054                       <p>
10055                         <code class="literal">128.9.0.33</code>
10056                       </p>
10057                     </td>
10058 </tr>
10059 </tbody>
10060 </table></div>
10061 <p>
10062               The MX RRs have an RDATA section which consists of a 16-bit
10063               number followed by a domain name.  The address RRs use a
10064               standard
10065               IP address format to contain a 32-bit internet address.
10066             </p>
10067 <p>
10068               The above example shows six RRs, with two RRs at each of three
10069               domain names.
10070             </p>
10071 <p>
10072               Similarly we might see:
10073             </p>
10074 <div class="informaltable"><table border="1">
10075 <colgroup>
10076 <col width="1.491in" class="1">
10077 <col width="1.067in" class="2">
10078 <col width="2.067in" class="3">
10079 </colgroup>
10080 <tbody>
10081 <tr>
10082 <td>
10083                       <p>
10084                         <code class="literal">XX.LCS.MIT.EDU.</code>
10085                       </p>
10086                     </td>
10087 <td>
10088                       <p>
10089                         <code class="literal">IN A</code>
10090                       </p>
10091                     </td>
10092 <td>
10093                       <p>
10094                         <code class="literal">10.0.0.44</code>
10095                       </p>
10096                     </td>
10097 </tr>
10098 <tr>
10099 <td> </td>
10100 <td>
10101                       <p>
10102                         <code class="literal">CH A</code>
10103                       </p>
10104                     </td>
10105 <td>
10106                       <p>
10107                         <code class="literal">MIT.EDU. 2420</code>
10108                       </p>
10109                     </td>
10110 </tr>
10111 </tbody>
10112 </table></div>
10113 <p>
10114               This example shows two addresses for
10115               <code class="literal">XX.LCS.MIT.EDU</code>, each of a different class.
10116             </p>
10117 </div>
10118 </div>
10119 <div class="section">
10120 <div class="titlepage"><div><div><h3 class="title">
10121 <a name="mx_records"></a>Discussion of MX Records</h3></div></div></div>
10122 <p>
10123             As described above, domain servers store information as a
10124             series of resource records, each of which contains a particular
10125             piece of information about a given domain name (which is usually,
10126             but not always, a host). The simplest way to think of a RR is as
10127             a typed pair of data, a domain name matched with a relevant datum,
10128             and stored with some additional type information to help systems
10129             determine when the RR is relevant.
10130           </p>
10131 <p>
10132             MX records are used to control delivery of email. The data
10133             specified in the record is a priority and a domain name. The
10134             priority
10135             controls the order in which email delivery is attempted, with the
10136             lowest number first. If two priorities are the same, a server is
10137             chosen randomly. If no servers at a given priority are responding,
10138             the mail transport agent will fall back to the next largest
10139             priority.
10140             Priority numbers do not have any absolute meaning &#8212; they are
10141             relevant
10142             only respective to other MX records for that domain name. The
10143             domain
10144             name given is the machine to which the mail will be delivered.
10145             It <span class="emphasis"><em>must</em></span> have an associated address record
10146             (A or AAAA) &#8212; CNAME is not sufficient.
10147           </p>
10148 <p>
10149             For a given domain, if there is both a CNAME record and an
10150             MX record, the MX record is in error, and will be ignored.
10151             Instead,
10152             the mail will be delivered to the server specified in the MX
10153             record
10154             pointed to by the CNAME.
10155             For example:
10156           </p>
10157 <div class="informaltable"><table border="1">
10158 <colgroup>
10159 <col width="1.708in" class="1">
10160 <col width="0.444in" class="2">
10161 <col width="0.444in" class="3">
10162 <col width="0.976in" class="4">
10163 <col width="1.553in" class="5">
10164 </colgroup>
10165 <tbody>
10166 <tr>
10167 <td>
10168                     <p>
10169                       <code class="literal">example.com.</code>
10170                     </p>
10171                   </td>
10172 <td>
10173                     <p>
10174                       <code class="literal">IN</code>
10175                     </p>
10176                   </td>
10177 <td>
10178                     <p>
10179                       <code class="literal">MX</code>
10180                     </p>
10181                   </td>
10182 <td>
10183                     <p>
10184                       <code class="literal">10</code>
10185                     </p>
10186                   </td>
10187 <td>
10188                     <p>
10189                       <code class="literal">mail.example.com.</code>
10190                     </p>
10191                   </td>
10192 </tr>
10193 <tr>
10194 <td>
10195                     <p></p>
10196                   </td>
10197 <td>
10198                     <p>
10199                       <code class="literal">IN</code>
10200                     </p>
10201                   </td>
10202 <td>
10203                     <p>
10204                       <code class="literal">MX</code>
10205                     </p>
10206                   </td>
10207 <td>
10208                     <p>
10209                       <code class="literal">10</code>
10210                     </p>
10211                   </td>
10212 <td>
10213                     <p>
10214                       <code class="literal">mail2.example.com.</code>
10215                     </p>
10216                   </td>
10217 </tr>
10218 <tr>
10219 <td>
10220                     <p></p>
10221                   </td>
10222 <td>
10223                     <p>
10224                       <code class="literal">IN</code>
10225                     </p>
10226                   </td>
10227 <td>
10228                     <p>
10229                       <code class="literal">MX</code>
10230                     </p>
10231                   </td>
10232 <td>
10233                     <p>
10234                       <code class="literal">20</code>
10235                     </p>
10236                   </td>
10237 <td>
10238                     <p>
10239                       <code class="literal">mail.backup.org.</code>
10240                     </p>
10241                   </td>
10242 </tr>
10243 <tr>
10244 <td>
10245                     <p>
10246                       <code class="literal">mail.example.com.</code>
10247                     </p>
10248                   </td>
10249 <td>
10250                     <p>
10251                       <code class="literal">IN</code>
10252                     </p>
10253                   </td>
10254 <td>
10255                     <p>
10256                       <code class="literal">A</code>
10257                     </p>
10258                   </td>
10259 <td>
10260                     <p>
10261                       <code class="literal">10.0.0.1</code>
10262                     </p>
10263                   </td>
10264 <td>
10265                     <p></p>
10266                   </td>
10267 </tr>
10268 <tr>
10269 <td>
10270                     <p>
10271                       <code class="literal">mail2.example.com.</code>
10272                     </p>
10273                   </td>
10274 <td>
10275                     <p>
10276                       <code class="literal">IN</code>
10277                     </p>
10278                   </td>
10279 <td>
10280                     <p>
10281                       <code class="literal">A</code>
10282                     </p>
10283                   </td>
10284 <td>
10285                     <p>
10286                       <code class="literal">10.0.0.2</code>
10287                     </p>
10288                   </td>
10289 <td>
10290                     <p></p>
10291                   </td>
10292 </tr>
10293 </tbody>
10294 </table></div>
10295 <p>
10296             Mail delivery will be attempted to <code class="literal">mail.example.com</code> and
10297             <code class="literal">mail2.example.com</code> (in
10298             any order), and if neither of those succeed, delivery to <code class="literal">mail.backup.org</code> will
10299             be attempted.
10300           </p>
10301 </div>
10302 <div class="section">
10303 <div class="titlepage"><div><div><h3 class="title">
10304 <a name="Setting_TTLs"></a>Setting TTLs</h3></div></div></div>
10305 <p>
10306             The time-to-live of the RR field is a 32-bit integer represented
10307             in units of seconds, and is primarily used by resolvers when they
10308             cache RRs. The TTL describes how long a RR can be cached before it
10309             should be discarded. The following three types of TTL are
10310             currently
10311             used in a zone file.
10312           </p>
10313 <div class="informaltable"><table border="1">
10314 <colgroup>
10315 <col width="0.750in" class="1">
10316 <col width="4.375in" class="2">
10317 </colgroup>
10318 <tbody>
10319 <tr>
10320 <td>
10321                     <p>
10322                       SOA
10323                     </p>
10324                   </td>
10325 <td>
10326                     <p>
10327                       The last field in the SOA is the negative
10328                       caching TTL. This controls how long other servers will
10329                       cache no-such-domain
10330                       (NXDOMAIN) responses from you.
10331                     </p>
10332                     <p>
10333                       The maximum time for
10334                       negative caching is 3 hours (3h).
10335                     </p>
10336                   </td>
10337 </tr>
10338 <tr>
10339 <td>
10340                     <p>
10341                       $TTL
10342                     </p>
10343                   </td>
10344 <td>
10345                     <p>
10346                       The $TTL directive at the top of the
10347                       zone file (before the SOA) gives a default TTL for every
10348                       RR without
10349                       a specific TTL set.
10350                     </p>
10351                   </td>
10352 </tr>
10353 <tr>
10354 <td>
10355                     <p>
10356                       RR TTLs
10357                     </p>
10358                   </td>
10359 <td>
10360                     <p>
10361                       Each RR can have a TTL as the second
10362                       field in the RR, which will control how long other
10363                       servers can cache it.
10364                     </p>
10365                   </td>
10366 </tr>
10367 </tbody>
10368 </table></div>
10369 <p>
10370             All of these TTLs default to units of seconds, though units
10371             can be explicitly specified, for example, <code class="literal">1h30m</code>.
10372           </p>
10373 </div>
10374 <div class="section">
10375 <div class="titlepage"><div><div><h3 class="title">
10376 <a name="ipv4_reverse"></a>Inverse Mapping in IPv4</h3></div></div></div>
10377 <p>
10378             Reverse name resolution (that is, translation from IP address
10379             to name) is achieved by means of the <span class="emphasis"><em>in-addr.arpa</em></span> domain
10380             and PTR records. Entries in the in-addr.arpa domain are made in
10381             least-to-most significant order, read left to right. This is the
10382             opposite order to the way IP addresses are usually written. Thus,
10383             a machine with an IP address of 10.1.2.3 would have a
10384             corresponding
10385             in-addr.arpa name of
10386             3.2.1.10.in-addr.arpa. This name should have a PTR resource record
10387             whose data field is the name of the machine or, optionally,
10388             multiple
10389             PTR records if the machine has more than one name. For example,
10390             in the [<span class="optional">example.com</span>] domain:
10391           </p>
10392 <div class="informaltable"><table border="1">
10393 <colgroup>
10394 <col width="1.125in" class="1">
10395 <col width="4.000in" class="2">
10396 </colgroup>
10397 <tbody>
10398 <tr>
10399 <td>
10400                     <p>
10401                       <code class="literal">$ORIGIN</code>
10402                     </p>
10403                   </td>
10404 <td>
10405                     <p>
10406                       <code class="literal">2.1.10.in-addr.arpa</code>
10407                     </p>
10408                   </td>
10409 </tr>
10410 <tr>
10411 <td>
10412                     <p>
10413                       <code class="literal">3</code>
10414                     </p>
10415                   </td>
10416 <td>
10417                     <p>
10418                       <code class="literal">IN PTR foo.example.com.</code>
10419                     </p>
10420                   </td>
10421 </tr>
10422 </tbody>
10423 </table></div>
10424 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
10425 <h3 class="title">Note</h3>
10426 <p>
10427               The <span class="command"><strong>$ORIGIN</strong></span> lines in the examples
10428               are for providing context to the examples only &#8212; they do not
10429               necessarily
10430               appear in the actual usage. They are only used here to indicate
10431               that the example is relative to the listed origin.
10432             </p>
10433 </div>
10434 </div>
10435 <div class="section">
10436 <div class="titlepage"><div><div><h3 class="title">
10437 <a name="zone_directives"></a>Other Zone File Directives</h3></div></div></div>
10438 <p>
10439             The Master File Format was initially defined in RFC 1035 and
10440             has subsequently been extended. While the Master File Format
10441             itself
10442             is class independent all records in a Master File must be of the
10443             same
10444             class.
10445           </p>
10446 <p>
10447             Master File Directives include <span class="command"><strong>$ORIGIN</strong></span>, <span class="command"><strong>$INCLUDE</strong></span>,
10448             and <span class="command"><strong>$TTL.</strong></span>
10449           </p>
10450 <div class="section">
10451 <div class="titlepage"><div><div><h4 class="title">
10452 <a name="atsign"></a>The <span class="command"><strong>@</strong></span> (at-sign)</h4></div></div></div>
10453 <p>
10454               When used in the label (or name) field, the asperand or
10455               at-sign (@) symbol represents the current origin.
10456               At the start of the zone file, it is the
10457               &lt;<code class="varname">zone_name</code>&gt; (followed by
10458               trailing dot).
10459             </p>
10460 </div>
10461 <div class="section">
10462 <div class="titlepage"><div><div><h4 class="title">
10463 <a name="origin_directive"></a>The <span class="command"><strong>$ORIGIN</strong></span> Directive</h4></div></div></div>
10464 <p>
10465               Syntax: <span class="command"><strong>$ORIGIN</strong></span>
10466               <em class="replaceable"><code>domain-name</code></em>
10467               [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
10468             </p>
10469 <p><span class="command"><strong>$ORIGIN</strong></span>
10470               sets the domain name that will be appended to any
10471               unqualified records. When a zone is first read in there
10472               is an implicit <span class="command"><strong>$ORIGIN</strong></span>
10473               &lt;<code class="varname">zone_name</code>&gt;<span class="command"><strong>.</strong></span>
10474               (followed by trailing dot).
10475               The current <span class="command"><strong>$ORIGIN</strong></span> is appended to
10476               the domain specified in the <span class="command"><strong>$ORIGIN</strong></span>
10477               argument if it is not absolute.
10478             </p>
10479 <pre class="programlisting">
10480 $ORIGIN example.com.
10481 WWW     CNAME   MAIN-SERVER
10482 </pre>
10483 <p>
10484               is equivalent to
10485             </p>
10486 <pre class="programlisting">
10487 WWW.EXAMPLE.COM. CNAME MAIN-SERVER.EXAMPLE.COM.
10488 </pre>
10489 </div>
10490 <div class="section">
10491 <div class="titlepage"><div><div><h4 class="title">
10492 <a name="include_directive"></a>The <span class="command"><strong>$INCLUDE</strong></span> Directive</h4></div></div></div>
10493 <p>
10494               Syntax: <span class="command"><strong>$INCLUDE</strong></span>
10495               <em class="replaceable"><code>filename</code></em>
10496               [<span class="optional">
10497 <em class="replaceable"><code>origin</code></em> </span>]
10498               [<span class="optional"> <em class="replaceable"><code>comment</code></em> </span>]
10499             </p>
10500 <p>
10501               Read and process the file <code class="filename">filename</code> as
10502               if it were included into the file at this point.  If <span class="command"><strong>origin</strong></span> is
10503               specified the file is processed with <span class="command"><strong>$ORIGIN</strong></span> set
10504               to that value, otherwise the current <span class="command"><strong>$ORIGIN</strong></span> is
10505               used.
10506             </p>
10507 <p>
10508               The origin and the current domain name
10509               revert to the values they had prior to the <span class="command"><strong>$INCLUDE</strong></span> once
10510               the file has been read.
10511             </p>
10512 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
10513 <h3 class="title">Note</h3>
10514 <p>
10515                 RFC 1035 specifies that the current origin should be restored
10516                 after
10517                 an <span class="command"><strong>$INCLUDE</strong></span>, but it is silent
10518                 on whether the current
10519                 domain name should also be restored.  BIND 9 restores both of
10520                 them.
10521                 This could be construed as a deviation from RFC 1035, a
10522                 feature, or both.
10523               </p>
10524 </div>
10525 </div>
10526 <div class="section">
10527 <div class="titlepage"><div><div><h4 class="title">
10528 <a name="ttl_directive"></a>The <span class="command"><strong>$TTL</strong></span> Directive</h4></div></div></div>
10529 <p>
10530               Syntax: <span class="command"><strong>$TTL</strong></span>
10531               <em class="replaceable"><code>default-ttl</code></em>
10532               [<span class="optional">
10533 <em class="replaceable"><code>comment</code></em> </span>]
10534             </p>
10535 <p>
10536               Set the default Time To Live (TTL) for subsequent records
10537               with undefined TTLs. Valid TTLs are of the range 0-2147483647
10538               seconds.
10539             </p>
10540 <p><span class="command"><strong>$TTL</strong></span>
10541                is defined in RFC 2308.
10542             </p>
10543 </div>
10544 </div>
10545 <div class="section">
10546 <div class="titlepage"><div><div><h3 class="title">
10547 <a name="generate_directive"></a><acronym class="acronym">BIND</acronym> Master File Extension: the  <span class="command"><strong>$GENERATE</strong></span> Directive</h3></div></div></div>
10548 <p>
10549             Syntax: <span class="command"><strong>$GENERATE</strong></span>
10550             <em class="replaceable"><code>range</code></em>
10551             <em class="replaceable"><code>lhs</code></em>
10552             [<span class="optional"><em class="replaceable"><code>ttl</code></em></span>]
10553             [<span class="optional"><em class="replaceable"><code>class</code></em></span>]
10554             <em class="replaceable"><code>type</code></em>
10555             <em class="replaceable"><code>rhs</code></em>
10556             [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
10557           </p>
10558 <p><span class="command"><strong>$GENERATE</strong></span>
10559             is used to create a series of resource records that only
10560             differ from each other by an
10561             iterator. <span class="command"><strong>$GENERATE</strong></span> can be used to
10562             easily generate the sets of records required to support
10563             sub /24 reverse delegations described in RFC 2317:
10564             Classless IN-ADDR.ARPA delegation.
10565           </p>
10566 <pre class="programlisting">$ORIGIN 0.0.192.IN-ADDR.ARPA.
10567 $GENERATE 1-2 @ NS SERVER$.EXAMPLE.
10568 $GENERATE 1-127 $ CNAME $.0</pre>
10569 <p>
10570             is equivalent to
10571           </p>
10572 <pre class="programlisting">0.0.0.192.IN-ADDR.ARPA. NS SERVER1.EXAMPLE.
10573 0.0.0.192.IN-ADDR.ARPA. NS SERVER2.EXAMPLE.
10574 1.0.0.192.IN-ADDR.ARPA. CNAME 1.0.0.0.192.IN-ADDR.ARPA.
10575 2.0.0.192.IN-ADDR.ARPA. CNAME 2.0.0.0.192.IN-ADDR.ARPA.
10576 ...
10577 127.0.0.192.IN-ADDR.ARPA. CNAME 127.0.0.0.192.IN-ADDR.ARPA.
10578 </pre>
10579 <p>
10580             Generate a set of A and MX records.  Note the MX's right hand
10581             side is a quoted string.  The quotes will be stripped when the
10582             right hand side is processed.
10583            </p>
10584 <pre class="programlisting">
10585 $ORIGIN EXAMPLE.
10586 $GENERATE 1-127 HOST-$ A 1.2.3.$
10587 $GENERATE 1-127 HOST-$ MX "0 ."</pre>
10588 <p>
10589             is equivalent to
10590           </p>
10591 <pre class="programlisting">HOST-1.EXAMPLE.   A  1.2.3.1
10592 HOST-1.EXAMPLE.   MX 0 .
10593 HOST-2.EXAMPLE.   A  1.2.3.2
10594 HOST-2.EXAMPLE.   MX 0 .
10595 HOST-3.EXAMPLE.   A  1.2.3.3
10596 HOST-3.EXAMPLE.   MX 0 .
10597 ...
10598 HOST-127.EXAMPLE. A  1.2.3.127
10599 HOST-127.EXAMPLE. MX 0 .
10600 </pre>
10601 <div class="informaltable"><table border="1">
10602 <colgroup>
10603 <col width="0.875in" class="1">
10604 <col width="4.250in" class="2">
10605 </colgroup>
10606 <tbody>
10607 <tr>
10608 <td>
10609                     <p><span class="command"><strong>range</strong></span></p>
10610                   </td>
10611 <td>
10612                     <p>
10613                       This can be one of two forms: start-stop
10614                       or start-stop/step. If the first form is used, then step
10615                       is set to 1. start, stop and step must be positive
10616                       integers between 0 and (2^31)-1. start must not be
10617                       larger than stop.
10618                     </p>
10619                   </td>
10620 </tr>
10621 <tr>
10622 <td>
10623                     <p><span class="command"><strong>lhs</strong></span></p>
10624                   </td>
10625 <td>
10626                     <p>This
10627                       describes the owner name of the resource records
10628                       to be created.  Any single <span class="command"><strong>$</strong></span>
10629                       (dollar sign)
10630                       symbols within the <span class="command"><strong>lhs</strong></span> string
10631                       are replaced by the iterator value.
10632
10633                       To get a $ in the output, you need to escape the
10634                       <span class="command"><strong>$</strong></span> using a backslash
10635                       <span class="command"><strong>\</strong></span>,
10636                       e.g. <span class="command"><strong>\$</strong></span>. The
10637                       <span class="command"><strong>$</strong></span> may optionally be followed
10638                       by modifiers which change the offset from the
10639                       iterator, field width and base.
10640
10641                       Modifiers are introduced by a
10642                       <span class="command"><strong>{</strong></span> (left brace) immediately following the
10643                       <span class="command"><strong>$</strong></span> as
10644                       <span class="command"><strong>${offset[,width[,base]]}</strong></span>.
10645                       For example, <span class="command"><strong>${-20,3,d}</strong></span>
10646                       subtracts 20 from the current value, prints the
10647                       result as a decimal in a zero-padded field of
10648                       width 3.
10649
10650                       Available output forms are decimal
10651                       (<span class="command"><strong>d</strong></span>), octal
10652                       (<span class="command"><strong>o</strong></span>), hexadecimal
10653                       (<span class="command"><strong>x</strong></span> or <span class="command"><strong>X</strong></span>
10654                       for uppercase) and nibble
10655                       (<span class="command"><strong>n</strong></span> or <span class="command"><strong>N</strong></span>\
10656                       for uppercase).  The default modifier is
10657                       <span class="command"><strong>${0,0,d}</strong></span>.  If the
10658                       <span class="command"><strong>lhs</strong></span> is not absolute, the
10659                       current <span class="command"><strong>$ORIGIN</strong></span> is appended
10660                       to the name.
10661                     </p>
10662                     <p>
10663                       In nibble mode the value will be treated as
10664                       if it was a reversed hexadecimal string
10665                       with each hexadecimal digit as a separate
10666                       label.  The width field includes the label
10667                       separator.
10668                     </p>
10669                     <p>
10670                       For compatibility with earlier versions,
10671                       <span class="command"><strong>$$</strong></span> is still recognized as
10672                       indicating a literal $ in the output.
10673                     </p>
10674                   </td>
10675 </tr>
10676 <tr>
10677 <td>
10678                     <p><span class="command"><strong>ttl</strong></span></p>
10679                   </td>
10680 <td>
10681                     <p>
10682                       Specifies the time-to-live of the generated records. If
10683                       not specified this will be inherited using the
10684                       normal TTL inheritance rules.
10685                     </p>
10686                     <p><span class="command"><strong>class</strong></span>
10687                       and <span class="command"><strong>ttl</strong></span> can be
10688                       entered in either order.
10689                     </p>
10690                   </td>
10691 </tr>
10692 <tr>
10693 <td>
10694                     <p><span class="command"><strong>class</strong></span></p>
10695                   </td>
10696 <td>
10697                     <p>
10698                       Specifies the class of the generated records.
10699                       This must match the zone class if it is
10700                       specified.
10701                     </p>
10702                     <p><span class="command"><strong>class</strong></span>
10703                       and <span class="command"><strong>ttl</strong></span> can be
10704                       entered in either order.
10705                     </p>
10706                   </td>
10707 </tr>
10708 <tr>
10709 <td>
10710                     <p><span class="command"><strong>type</strong></span></p>
10711                   </td>
10712 <td>
10713                     <p>
10714                       Any valid type.
10715                     </p>
10716                   </td>
10717 </tr>
10718 <tr>
10719 <td>
10720                     <p><span class="command"><strong>rhs</strong></span></p>
10721                   </td>
10722 <td>
10723                     <p>
10724                       <span class="command"><strong>rhs</strong></span>, optionally, quoted string.
10725                     </p>
10726                   </td>
10727 </tr>
10728 </tbody>
10729 </table></div>
10730 <p>
10731             The <span class="command"><strong>$GENERATE</strong></span> directive is a <acronym class="acronym">BIND</acronym> extension
10732             and not part of the standard zone file format.
10733           </p>
10734 <p>
10735             BIND 8 does not support the optional TTL and CLASS fields.
10736           </p>
10737 </div>
10738 <div class="section">
10739 <div class="titlepage"><div><div><h3 class="title">
10740 <a name="zonefile_format"></a>Additional File Formats</h3></div></div></div>
10741 <p>
10742             In addition to the standard textual format, BIND 9
10743             supports the ability to read or dump to zone files in
10744             other formats.  The <code class="constant">raw</code> format is
10745             currently available as an additional format.  It is a
10746             binary format representing BIND 9's internal data
10747             structure directly, thereby remarkably improving the
10748             loading time.
10749           </p>
10750 <p>
10751             For a primary server, a zone file in the
10752             <code class="constant">raw</code> format is expected to be
10753             generated from a textual zone file by the
10754             <span class="command"><strong>named-compilezone</strong></span> command.  For a
10755             secondary server or for a dynamic zone, it is automatically
10756             generated (if this format is specified by the
10757             <span class="command"><strong>masterfile-format</strong></span> option) when
10758             <span class="command"><strong>named</strong></span> dumps the zone contents after
10759             zone transfer or when applying prior updates.
10760           </p>
10761 <p>
10762             If a zone file in a binary format needs manual modification,
10763             it first must be converted to a textual form by the
10764             <span class="command"><strong>named-compilezone</strong></span> command.  All
10765             necessary modification should go to the text file, which
10766             should then be converted to the binary form by the
10767             <span class="command"><strong>named-compilezone</strong></span> command again.
10768           </p>
10769 <p>
10770              Although the <code class="constant">raw</code> format uses the
10771              network byte order and avoids architecture-dependent
10772              data alignment so that it is as much portable as
10773              possible, it is primarily expected to be used inside
10774              the same single system.  In order to export a zone
10775              file in the <code class="constant">raw</code> format or make a
10776              portable backup of the file, it is recommended to
10777              convert the file to the standard textual representation.
10778           </p>
10779 </div>
10780 </div>
10781 <div class="section">
10782 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
10783 <a name="statistics"></a>BIND9 Statistics</h2></div></div></div>
10784 <p>
10785           <acronym class="acronym">BIND</acronym> 9 maintains lots of statistics
10786           information and provides several interfaces for users to
10787           get access to the statistics.
10788           The available statistics include all statistics counters
10789           that were available in <acronym class="acronym">BIND</acronym> 8 and
10790           are meaningful in <acronym class="acronym">BIND</acronym> 9,
10791           and other information that is considered useful.
10792         </p>
10793 <p>
10794           The statistics information is categorized into the following
10795           sections.
10796         </p>
10797 <div class="informaltable"><table border="1">
10798 <colgroup>
10799 <col width="3.300in" class="1">
10800 <col width="2.625in" class="2">
10801 </colgroup>
10802 <tbody>
10803 <tr>
10804 <td>
10805                   <p>Incoming Requests</p>
10806                 </td>
10807 <td>
10808                   <p>
10809                     The number of incoming DNS requests for each OPCODE.
10810                   </p>
10811                 </td>
10812 </tr>
10813 <tr>
10814 <td>
10815                   <p>Incoming Queries</p>
10816                 </td>
10817 <td>
10818                   <p>
10819                     The number of incoming queries for each RR type.
10820                   </p>
10821                 </td>
10822 </tr>
10823 <tr>
10824 <td>
10825                   <p>Outgoing Queries</p>
10826                 </td>
10827 <td>
10828                   <p>
10829                     The number of outgoing queries for each RR
10830                     type sent from the internal resolver.
10831                     Maintained per view.
10832                   </p>
10833                 </td>
10834 </tr>
10835 <tr>
10836 <td>
10837                   <p>Name Server Statistics</p>
10838                 </td>
10839 <td>
10840                   <p>
10841                     Statistics counters about incoming request processing.
10842                   </p>
10843                 </td>
10844 </tr>
10845 <tr>
10846 <td>
10847                   <p>Zone Maintenance Statistics</p>
10848                 </td>
10849 <td>
10850                   <p>
10851                     Statistics counters regarding zone maintenance
10852                     operations such as zone transfers.
10853                   </p>
10854                 </td>
10855 </tr>
10856 <tr>
10857 <td>
10858                   <p>Resolver Statistics</p>
10859                 </td>
10860 <td>
10861                   <p>
10862                     Statistics counters about name resolution
10863                     performed in the internal resolver.
10864                     Maintained per view.
10865                   </p>
10866                 </td>
10867 </tr>
10868 <tr>
10869 <td>
10870                   <p>Cache DB RRsets</p>
10871                 </td>
10872 <td>
10873                   <p>
10874                     The number of RRsets per RR type and nonexistent
10875                     names stored in the cache database.
10876                     If the exclamation mark (!) is printed for a RR
10877                     type, it means that particular type of RRset is
10878                     known to be nonexistent (this is also known as
10879                     "NXRRSET").
10880                     Maintained per view.
10881                   </p>
10882                 </td>
10883 </tr>
10884 <tr>
10885 <td>
10886                   <p>Socket I/O Statistics</p>
10887                 </td>
10888 <td>
10889                   <p>
10890                     Statistics counters about network related events.
10891                   </p>
10892                 </td>
10893 </tr>
10894 </tbody>
10895 </table></div>
10896 <p>
10897           A subset of Name Server Statistics is collected and shown
10898           per zone for which the server has the authority when
10899           <span class="command"><strong>zone-statistics</strong></span> is set to
10900           <strong class="userinput"><code>full</code></strong> (or <strong class="userinput"><code>yes</code></strong>
10901           for backward compatibility. See the description of
10902           <span class="command"><strong>zone-statistics</strong></span> in <a class="xref" href="Bv9ARM.ch06.html#options" title="options Statement Definition and Usage">the section called &#8220;<span class="command"><strong>options</strong></span> Statement Definition and
10903           Usage&#8221;</a>
10904           for further details.
10905         </p>
10906 <p>
10907           These statistics counters are shown with their zone and
10908           view names. The view name is omitted when the server is
10909           not configured with explicit views.</p>
10910 <p>
10911           There are currently two user interfaces to get access to the
10912           statistics.
10913           One is in the plain text format dumped to the file specified
10914           by the <span class="command"><strong>statistics-file</strong></span> configuration option.
10915           The other is remotely accessible via a statistics channel
10916           when the <span class="command"><strong>statistics-channels</strong></span> statement
10917           is specified in the configuration file
10918           (see <a class="xref" href="Bv9ARM.ch06.html#statschannels" title="statistics-channels Statement Grammar">the section called &#8220;<span class="command"><strong>statistics-channels</strong></span> Statement Grammar&#8221;</a>.)
10919         </p>
10920 <div class="section">
10921 <div class="titlepage"><div><div><h3 class="title">
10922 <a name="statsfile"></a>The Statistics File</h3></div></div></div>
10923 <p>
10924             The text format statistics dump begins with a line, like:
10925           </p>
10926 <p>
10927             <span class="command"><strong>+++ Statistics Dump +++ (973798949)</strong></span>
10928           </p>
10929 <p>
10930             The number in parentheses is a standard
10931             Unix-style timestamp, measured as seconds since January 1, 1970.
10932
10933             Following
10934             that line is a set of statistics information, which is categorized
10935             as described above.
10936             Each section begins with a line, like:
10937           </p>
10938 <p>
10939             <span class="command"><strong>++ Name Server Statistics ++</strong></span>
10940           </p>
10941 <p>
10942             Each section consists of lines, each containing the statistics
10943             counter value followed by its textual description.
10944             See below for available counters.
10945             For brevity, counters that have a value of 0 are not shown
10946             in the statistics file.
10947           </p>
10948 <p>
10949             The statistics dump ends with the line where the
10950             number is identical to the number in the beginning line; for example:
10951           </p>
10952 <p>
10953             <span class="command"><strong>--- Statistics Dump --- (973798949)</strong></span>
10954           </p>
10955 </div>
10956 <div class="section">
10957 <div class="titlepage"><div><div><h3 class="title">
10958 <a name="statistics_counters"></a>Statistics Counters</h3></div></div></div>
10959 <p>
10960             The following tables summarize statistics counters that
10961             <acronym class="acronym">BIND</acronym> 9 provides.
10962             For each row of the tables, the leftmost column is the
10963             abbreviated symbol name of that counter.
10964             These symbols are shown in the statistics information
10965             accessed via an HTTP statistics channel.
10966             The rightmost column gives the description of the counter,
10967             which is also shown in the statistics file
10968             (but, in this document, possibly with slight modification
10969             for better readability).
10970             Additional notes may also be provided in this column.
10971             When a middle column exists between these two columns,
10972             it gives the corresponding counter name of the
10973             <acronym class="acronym">BIND</acronym> 8 statistics, if applicable.
10974           </p>
10975 <div class="section">
10976 <div class="titlepage"><div><div><h4 class="title">
10977 <a name="stats_counters"></a>Name Server Statistics Counters</h4></div></div></div>
10978 <div class="informaltable"><table border="1">
10979 <colgroup>
10980 <col width="1.150in" class="1">
10981 <col width="1.150in" class="2">
10982 <col width="3.350in" class="3">
10983 </colgroup>
10984 <tbody>
10985 <tr>
10986 <td>
10987                       <p>
10988                         <span class="emphasis"><em>Symbol</em></span>
10989                       </p>
10990                     </td>
10991 <td>
10992                       <p>
10993                         <span class="emphasis"><em>BIND8 Symbol</em></span>
10994                       </p>
10995                     </td>
10996 <td>
10997                       <p>
10998                         <span class="emphasis"><em>Description</em></span>
10999                       </p>
11000                     </td>
11001 </tr>
11002 <tr>
11003 <td>
11004                       <p><span class="command"><strong>Requestv4</strong></span></p>
11005                     </td>
11006 <td>
11007                       <p><span class="command"><strong>RQ</strong></span></p>
11008                     </td>
11009 <td>
11010                       <p>
11011                         IPv4 requests received.
11012                         Note: this also counts non query requests.
11013                       </p>
11014                     </td>
11015 </tr>
11016 <tr>
11017 <td>
11018                       <p><span class="command"><strong>Requestv6</strong></span></p>
11019                     </td>
11020 <td>
11021                       <p><span class="command"><strong>RQ</strong></span></p>
11022                     </td>
11023 <td>
11024                       <p>
11025                         IPv6 requests received.
11026                         Note: this also counts non query requests.
11027                       </p>
11028                     </td>
11029 </tr>
11030 <tr>
11031 <td>
11032                       <p><span class="command"><strong>ReqEdns0</strong></span></p>
11033                     </td>
11034 <td>
11035                       <p><span class="command"><strong></strong></span></p>
11036                     </td>
11037 <td>
11038                       <p>
11039                         Requests with EDNS(0) received.
11040                       </p>
11041                     </td>
11042 </tr>
11043 <tr>
11044 <td>
11045                       <p><span class="command"><strong>ReqBadEDNSVer</strong></span></p>
11046                     </td>
11047 <td>
11048                       <p><span class="command"><strong></strong></span></p>
11049                     </td>
11050 <td>
11051                       <p>
11052                         Requests with unsupported EDNS version received.
11053                       </p>
11054                     </td>
11055 </tr>
11056 <tr>
11057 <td>
11058                       <p><span class="command"><strong>ReqTSIG</strong></span></p>
11059                     </td>
11060 <td>
11061                       <p><span class="command"><strong></strong></span></p>
11062                     </td>
11063 <td>
11064                       <p>
11065                         Requests with TSIG received.
11066                       </p>
11067                     </td>
11068 </tr>
11069 <tr>
11070 <td>
11071                       <p><span class="command"><strong>ReqSIG0</strong></span></p>
11072                     </td>
11073 <td>
11074                       <p><span class="command"><strong></strong></span></p>
11075                     </td>
11076 <td>
11077                       <p>
11078                         Requests with SIG(0) received.
11079                       </p>
11080                     </td>
11081 </tr>
11082 <tr>
11083 <td>
11084                       <p><span class="command"><strong>ReqBadSIG</strong></span></p>
11085                     </td>
11086 <td>
11087                       <p><span class="command"><strong></strong></span></p>
11088                     </td>
11089 <td>
11090                       <p>
11091                         Requests with invalid (TSIG or SIG(0)) signature.
11092                       </p>
11093                     </td>
11094 </tr>
11095 <tr>
11096 <td>
11097                       <p><span class="command"><strong>ReqTCP</strong></span></p>
11098                     </td>
11099 <td>
11100                       <p><span class="command"><strong>RTCP</strong></span></p>
11101                     </td>
11102 <td>
11103                       <p>
11104                         TCP requests received.
11105                       </p>
11106                     </td>
11107 </tr>
11108 <tr>
11109 <td>
11110                       <p><span class="command"><strong>AuthQryRej</strong></span></p>
11111                     </td>
11112 <td>
11113                       <p><span class="command"><strong>RUQ</strong></span></p>
11114                     </td>
11115 <td>
11116                       <p>
11117                         Authoritative (non recursive) queries rejected.
11118                       </p>
11119                     </td>
11120 </tr>
11121 <tr>
11122 <td>
11123                       <p><span class="command"><strong>RecQryRej</strong></span></p>
11124                     </td>
11125 <td>
11126                       <p><span class="command"><strong>RURQ</strong></span></p>
11127                     </td>
11128 <td>
11129                       <p>
11130                         Recursive queries rejected.
11131                       </p>
11132                     </td>
11133 </tr>
11134 <tr>
11135 <td>
11136                       <p><span class="command"><strong>XfrRej</strong></span></p>
11137                     </td>
11138 <td>
11139                       <p><span class="command"><strong>RUXFR</strong></span></p>
11140                     </td>
11141 <td>
11142                       <p>
11143                         Zone transfer requests rejected.
11144                       </p>
11145                     </td>
11146 </tr>
11147 <tr>
11148 <td>
11149                       <p><span class="command"><strong>UpdateRej</strong></span></p>
11150                     </td>
11151 <td>
11152                       <p><span class="command"><strong>RUUpd</strong></span></p>
11153                     </td>
11154 <td>
11155                       <p>
11156                         Dynamic update requests rejected.
11157                       </p>
11158                     </td>
11159 </tr>
11160 <tr>
11161 <td>
11162                       <p><span class="command"><strong>Response</strong></span></p>
11163                     </td>
11164 <td>
11165                       <p><span class="command"><strong>SAns</strong></span></p>
11166                     </td>
11167 <td>
11168                       <p>
11169                         Responses sent.
11170                       </p>
11171                     </td>
11172 </tr>
11173 <tr>
11174 <td>
11175                       <p><span class="command"><strong>RespTruncated</strong></span></p>
11176                     </td>
11177 <td>
11178                       <p><span class="command"><strong></strong></span></p>
11179                     </td>
11180 <td>
11181                       <p>
11182                         Truncated responses sent.
11183                       </p>
11184                     </td>
11185 </tr>
11186 <tr>
11187 <td>
11188                       <p><span class="command"><strong>RespEDNS0</strong></span></p>
11189                     </td>
11190 <td>
11191                       <p><span class="command"><strong></strong></span></p>
11192                     </td>
11193 <td>
11194                       <p>
11195                         Responses with EDNS(0) sent.
11196                       </p>
11197                     </td>
11198 </tr>
11199 <tr>
11200 <td>
11201                       <p><span class="command"><strong>RespTSIG</strong></span></p>
11202                     </td>
11203 <td>
11204                       <p><span class="command"><strong></strong></span></p>
11205                     </td>
11206 <td>
11207                       <p>
11208                         Responses with TSIG sent.
11209                       </p>
11210                     </td>
11211 </tr>
11212 <tr>
11213 <td>
11214                       <p><span class="command"><strong>RespSIG0</strong></span></p>
11215                     </td>
11216 <td>
11217                       <p><span class="command"><strong></strong></span></p>
11218                     </td>
11219 <td>
11220                       <p>
11221                         Responses with SIG(0) sent.
11222                       </p>
11223                     </td>
11224 </tr>
11225 <tr>
11226 <td>
11227                       <p><span class="command"><strong>QrySuccess</strong></span></p>
11228                     </td>
11229 <td>
11230                       <p><span class="command"><strong></strong></span></p>
11231                     </td>
11232 <td>
11233                       <p>
11234                         Queries resulted in a successful answer.
11235                         This means the query which returns a NOERROR response
11236                         with at least one answer RR.
11237                         This corresponds to the
11238                         <span class="command"><strong>success</strong></span> counter
11239                         of previous versions of
11240                         <acronym class="acronym">BIND</acronym> 9.
11241                       </p>
11242                     </td>
11243 </tr>
11244 <tr>
11245 <td>
11246                       <p><span class="command"><strong>QryAuthAns</strong></span></p>
11247                     </td>
11248 <td>
11249                       <p><span class="command"><strong></strong></span></p>
11250                     </td>
11251 <td>
11252                       <p>
11253                         Queries resulted in authoritative answer.
11254                       </p>
11255                     </td>
11256 </tr>
11257 <tr>
11258 <td>
11259                       <p><span class="command"><strong>QryNoauthAns</strong></span></p>
11260                     </td>
11261 <td>
11262                       <p><span class="command"><strong>SNaAns</strong></span></p>
11263                     </td>
11264 <td>
11265                       <p>
11266                         Queries resulted in non authoritative answer.
11267                       </p>
11268                     </td>
11269 </tr>
11270 <tr>
11271 <td>
11272                       <p><span class="command"><strong>QryReferral</strong></span></p>
11273                     </td>
11274 <td>
11275                       <p><span class="command"><strong></strong></span></p>
11276                     </td>
11277 <td>
11278                       <p>
11279                         Queries resulted in referral answer.
11280                         This corresponds to the
11281                         <span class="command"><strong>referral</strong></span> counter
11282                         of previous versions of
11283                         <acronym class="acronym">BIND</acronym> 9.
11284                       </p>
11285                     </td>
11286 </tr>
11287 <tr>
11288 <td>
11289                       <p><span class="command"><strong>QryNxrrset</strong></span></p>
11290                     </td>
11291 <td>
11292                       <p><span class="command"><strong></strong></span></p>
11293                     </td>
11294 <td>
11295                       <p>
11296                         Queries resulted in NOERROR responses with no data.
11297                         This corresponds to the
11298                         <span class="command"><strong>nxrrset</strong></span> counter
11299                         of previous versions of
11300                         <acronym class="acronym">BIND</acronym> 9.
11301                       </p>
11302                     </td>
11303 </tr>
11304 <tr>
11305 <td>
11306                       <p><span class="command"><strong>QrySERVFAIL</strong></span></p>
11307                     </td>
11308 <td>
11309                       <p><span class="command"><strong>SFail</strong></span></p>
11310                     </td>
11311 <td>
11312                       <p>
11313                         Queries resulted in SERVFAIL.
11314                       </p>
11315                     </td>
11316 </tr>
11317 <tr>
11318 <td>
11319                       <p><span class="command"><strong>QryFORMERR</strong></span></p>
11320                     </td>
11321 <td>
11322                       <p><span class="command"><strong>SFErr</strong></span></p>
11323                     </td>
11324 <td>
11325                       <p>
11326                         Queries resulted in FORMERR.
11327                       </p>
11328                     </td>
11329 </tr>
11330 <tr>
11331 <td>
11332                       <p><span class="command"><strong>QryNXDOMAIN</strong></span></p>
11333                     </td>
11334 <td>
11335                       <p><span class="command"><strong>SNXD</strong></span></p>
11336                     </td>
11337 <td>
11338                       <p>
11339                         Queries resulted in NXDOMAIN.
11340                         This corresponds to the
11341                         <span class="command"><strong>nxdomain</strong></span> counter
11342                         of previous versions of
11343                         <acronym class="acronym">BIND</acronym> 9.
11344                       </p>
11345                     </td>
11346 </tr>
11347 <tr>
11348 <td>
11349                       <p><span class="command"><strong>QryRecursion</strong></span></p>
11350                     </td>
11351 <td>
11352                       <p><span class="command"><strong>RFwdQ</strong></span></p>
11353                     </td>
11354 <td>
11355                       <p>
11356                         Queries which caused the server
11357                         to perform recursion in order to find the final answer.
11358                         This corresponds to the
11359                         <span class="command"><strong>recursion</strong></span> counter
11360                         of previous versions of
11361                         <acronym class="acronym">BIND</acronym> 9.
11362                       </p>
11363                     </td>
11364 </tr>
11365 <tr>
11366 <td>
11367                       <p><span class="command"><strong>QryDuplicate</strong></span></p>
11368                     </td>
11369 <td>
11370                       <p><span class="command"><strong>RDupQ</strong></span></p>
11371                     </td>
11372 <td>
11373                       <p>
11374                         Queries which the server attempted to
11375                         recurse but discovered an existing query with the same
11376                         IP address, port, query ID, name, type and class
11377                         already being processed.
11378                         This corresponds to the
11379                         <span class="command"><strong>duplicate</strong></span> counter
11380                         of previous versions of
11381                         <acronym class="acronym">BIND</acronym> 9.
11382                       </p>
11383                     </td>
11384 </tr>
11385 <tr>
11386 <td>
11387                       <p><span class="command"><strong>QryDropped</strong></span></p>
11388                     </td>
11389 <td>
11390                       <p><span class="command"><strong></strong></span></p>
11391                     </td>
11392 <td>
11393                       <p>
11394                         Recursive queries for which the server
11395                         discovered an excessive number of existing
11396                         recursive queries for the same name, type and
11397                         class and were subsequently dropped.
11398                         This is the number of dropped queries due to
11399                         the reason explained with the
11400                         <span class="command"><strong>clients-per-query</strong></span>
11401                         and
11402                         <span class="command"><strong>max-clients-per-query</strong></span>
11403                         options
11404                         (see the description about
11405                         <a class="xref" href="Bv9ARM.ch06.html#clients-per-query"><span class="command"><strong>clients-per-query</strong></span></a>.)
11406                         This corresponds to the
11407                         <span class="command"><strong>dropped</strong></span> counter
11408                         of previous versions of
11409                         <acronym class="acronym">BIND</acronym> 9.
11410                       </p>
11411                     </td>
11412 </tr>
11413 <tr>
11414 <td>
11415                       <p><span class="command"><strong>QryFailure</strong></span></p>
11416                     </td>
11417 <td>
11418                       <p><span class="command"><strong></strong></span></p>
11419                     </td>
11420 <td>
11421                       <p>
11422                         Other query failures.
11423                         This corresponds to the
11424                         <span class="command"><strong>failure</strong></span> counter
11425                         of previous versions of
11426                         <acronym class="acronym">BIND</acronym> 9.
11427                         Note: this counter is provided mainly for
11428                         backward compatibility with the previous versions.
11429                         Normally a more fine-grained counters such as
11430                         <span class="command"><strong>AuthQryRej</strong></span> and
11431                         <span class="command"><strong>RecQryRej</strong></span>
11432                         that would also fall into this counter are provided,
11433                         and so this counter would not be of much
11434                         interest in practice.
11435                       </p>
11436                     </td>
11437 </tr>
11438 <tr>
11439 <td>
11440                       <p><span class="command"><strong>XfrReqDone</strong></span></p>
11441                     </td>
11442 <td>
11443                       <p><span class="command"><strong></strong></span></p>
11444                     </td>
11445 <td>
11446                       <p>
11447                         Requested zone transfers completed.
11448                       </p>
11449                     </td>
11450 </tr>
11451 <tr>
11452 <td>
11453                       <p><span class="command"><strong>UpdateReqFwd</strong></span></p>
11454                     </td>
11455 <td>
11456                       <p><span class="command"><strong></strong></span></p>
11457                     </td>
11458 <td>
11459                       <p>
11460                         Update requests forwarded.
11461                       </p>
11462                     </td>
11463 </tr>
11464 <tr>
11465 <td>
11466                       <p><span class="command"><strong>UpdateRespFwd</strong></span></p>
11467                     </td>
11468 <td>
11469                       <p><span class="command"><strong></strong></span></p>
11470                     </td>
11471 <td>
11472                       <p>
11473                         Update responses forwarded.
11474                       </p>
11475                     </td>
11476 </tr>
11477 <tr>
11478 <td>
11479                       <p><span class="command"><strong>UpdateFwdFail</strong></span></p>
11480                     </td>
11481 <td>
11482                       <p><span class="command"><strong></strong></span></p>
11483                     </td>
11484 <td>
11485                       <p>
11486                         Dynamic update forward failed.
11487                       </p>
11488                     </td>
11489 </tr>
11490 <tr>
11491 <td>
11492                       <p><span class="command"><strong>UpdateDone</strong></span></p>
11493                     </td>
11494 <td>
11495                       <p><span class="command"><strong></strong></span></p>
11496                     </td>
11497 <td>
11498                       <p>
11499                         Dynamic updates completed.
11500                       </p>
11501                     </td>
11502 </tr>
11503 <tr>
11504 <td>
11505                       <p><span class="command"><strong>UpdateFail</strong></span></p>
11506                     </td>
11507 <td>
11508                       <p><span class="command"><strong></strong></span></p>
11509                     </td>
11510 <td>
11511                       <p>
11512                         Dynamic updates failed.
11513                       </p>
11514                     </td>
11515 </tr>
11516 <tr>
11517 <td>
11518                       <p><span class="command"><strong>UpdateBadPrereq</strong></span></p>
11519                     </td>
11520 <td>
11521                       <p><span class="command"><strong></strong></span></p>
11522                     </td>
11523 <td>
11524                       <p>
11525                         Dynamic updates rejected due to prerequisite failure.
11526                       </p>
11527                     </td>
11528 </tr>
11529 <tr>
11530 <td>
11531                       <p><span class="command"><strong>RPZRewrites</strong></span></p>
11532                     </td>
11533 <td>
11534                       <p><span class="command"><strong></strong></span></p>
11535                     </td>
11536 <td>
11537                       <p>
11538                         Response policy zone rewrites.
11539                       </p>
11540                     </td>
11541 </tr>
11542 <tr>
11543 <td>
11544                       <p><span class="command"><strong>RateDropped</strong></span></p>
11545                     </td>
11546 <td>
11547                       <p><span class="command"><strong></strong></span></p>
11548                     </td>
11549 <td>
11550                       <p>
11551                         Responses dropped by rate limits.
11552                       </p>
11553                     </td>
11554 </tr>
11555 <tr>
11556 <td>
11557                       <p><span class="command"><strong>RateSlipped</strong></span></p>
11558                     </td>
11559 <td>
11560                       <p><span class="command"><strong></strong></span></p>
11561                     </td>
11562 <td>
11563                       <p>
11564                         Responses truncated by rate limits.
11565                       </p>
11566                     </td>
11567 </tr>
11568 </tbody>
11569 </table></div>
11570 </div>
11571 <div class="section">
11572 <div class="titlepage"><div><div><h4 class="title">
11573 <a name="zone_stats"></a>Zone Maintenance Statistics Counters</h4></div></div></div>
11574 <div class="informaltable"><table border="1">
11575 <colgroup>
11576 <col width="1.150in" class="1">
11577 <col width="3.350in" class="2">
11578 </colgroup>
11579 <tbody>
11580 <tr>
11581 <td>
11582                       <p>
11583                         <span class="emphasis"><em>Symbol</em></span>
11584                       </p>
11585                     </td>
11586 <td>
11587                       <p>
11588                         <span class="emphasis"><em>Description</em></span>
11589                       </p>
11590                     </td>
11591 </tr>
11592 <tr>
11593 <td>
11594                       <p><span class="command"><strong>NotifyOutv4</strong></span></p>
11595                     </td>
11596 <td>
11597                       <p>
11598                         IPv4 notifies sent.
11599                       </p>
11600                     </td>
11601 </tr>
11602 <tr>
11603 <td>
11604                       <p><span class="command"><strong>NotifyOutv6</strong></span></p>
11605                     </td>
11606 <td>
11607                       <p>
11608                         IPv6 notifies sent.
11609                       </p>
11610                     </td>
11611 </tr>
11612 <tr>
11613 <td>
11614                       <p><span class="command"><strong>NotifyInv4</strong></span></p>
11615                     </td>
11616 <td>
11617                       <p>
11618                         IPv4 notifies received.
11619                       </p>
11620                     </td>
11621 </tr>
11622 <tr>
11623 <td>
11624                       <p><span class="command"><strong>NotifyInv6</strong></span></p>
11625                     </td>
11626 <td>
11627                       <p>
11628                         IPv6 notifies received.
11629                       </p>
11630                     </td>
11631 </tr>
11632 <tr>
11633 <td>
11634                       <p><span class="command"><strong>NotifyRej</strong></span></p>
11635                     </td>
11636 <td>
11637                       <p>
11638                         Incoming notifies rejected.
11639                       </p>
11640                     </td>
11641 </tr>
11642 <tr>
11643 <td>
11644                       <p><span class="command"><strong>SOAOutv4</strong></span></p>
11645                     </td>
11646 <td>
11647                       <p>
11648                         IPv4 SOA queries sent.
11649                       </p>
11650                     </td>
11651 </tr>
11652 <tr>
11653 <td>
11654                       <p><span class="command"><strong>SOAOutv6</strong></span></p>
11655                     </td>
11656 <td>
11657                       <p>
11658                         IPv6 SOA queries sent.
11659                       </p>
11660                     </td>
11661 </tr>
11662 <tr>
11663 <td>
11664                       <p><span class="command"><strong>AXFRReqv4</strong></span></p>
11665                     </td>
11666 <td>
11667                       <p>
11668                         IPv4 AXFR requested.
11669                       </p>
11670                     </td>
11671 </tr>
11672 <tr>
11673 <td>
11674                       <p><span class="command"><strong>AXFRReqv6</strong></span></p>
11675                     </td>
11676 <td>
11677                       <p>
11678                         IPv6 AXFR requested.
11679                       </p>
11680                     </td>
11681 </tr>
11682 <tr>
11683 <td>
11684                       <p><span class="command"><strong>IXFRReqv4</strong></span></p>
11685                     </td>
11686 <td>
11687                       <p>
11688                         IPv4 IXFR requested.
11689                       </p>
11690                     </td>
11691 </tr>
11692 <tr>
11693 <td>
11694                       <p><span class="command"><strong>IXFRReqv6</strong></span></p>
11695                     </td>
11696 <td>
11697                       <p>
11698                         IPv6 IXFR requested.
11699                       </p>
11700                     </td>
11701 </tr>
11702 <tr>
11703 <td>
11704                       <p><span class="command"><strong>XfrSuccess</strong></span></p>
11705                     </td>
11706 <td>
11707                       <p>
11708                         Zone transfer requests succeeded.
11709                       </p>
11710                     </td>
11711 </tr>
11712 <tr>
11713 <td>
11714                       <p><span class="command"><strong>XfrFail</strong></span></p>
11715                     </td>
11716 <td>
11717                       <p>
11718                         Zone transfer requests failed.
11719                       </p>
11720                     </td>
11721 </tr>
11722 </tbody>
11723 </table></div>
11724 </div>
11725 <div class="section">
11726 <div class="titlepage"><div><div><h4 class="title">
11727 <a name="resolver_stats"></a>Resolver Statistics Counters</h4></div></div></div>
11728 <div class="informaltable"><table border="1">
11729 <colgroup>
11730 <col width="1.150in" class="1">
11731 <col width="1.150in" class="2">
11732 <col width="3.350in" class="3">
11733 </colgroup>
11734 <tbody>
11735 <tr>
11736 <td>
11737                       <p>
11738                         <span class="emphasis"><em>Symbol</em></span>
11739                       </p>
11740                     </td>
11741 <td>
11742                       <p>
11743                         <span class="emphasis"><em>BIND8 Symbol</em></span>
11744                       </p>
11745                     </td>
11746 <td>
11747                       <p>
11748                         <span class="emphasis"><em>Description</em></span>
11749                       </p>
11750                     </td>
11751 </tr>
11752 <tr>
11753 <td>
11754                       <p><span class="command"><strong>Queryv4</strong></span></p>
11755                     </td>
11756 <td>
11757                       <p><span class="command"><strong>SFwdQ</strong></span></p>
11758                     </td>
11759 <td>
11760                       <p>
11761                         IPv4 queries sent.
11762                       </p>
11763                     </td>
11764 </tr>
11765 <tr>
11766 <td>
11767                       <p><span class="command"><strong>Queryv6</strong></span></p>
11768                     </td>
11769 <td>
11770                       <p><span class="command"><strong>SFwdQ</strong></span></p>
11771                     </td>
11772 <td>
11773                       <p>
11774                         IPv6 queries sent.
11775                       </p>
11776                     </td>
11777 </tr>
11778 <tr>
11779 <td>
11780                       <p><span class="command"><strong>Responsev4</strong></span></p>
11781                     </td>
11782 <td>
11783                       <p><span class="command"><strong>RR</strong></span></p>
11784                     </td>
11785 <td>
11786                       <p>
11787                         IPv4 responses received.
11788                       </p>
11789                     </td>
11790 </tr>
11791 <tr>
11792 <td>
11793                       <p><span class="command"><strong>Responsev6</strong></span></p>
11794                     </td>
11795 <td>
11796                       <p><span class="command"><strong>RR</strong></span></p>
11797                     </td>
11798 <td>
11799                       <p>
11800                         IPv6 responses received.
11801                       </p>
11802                     </td>
11803 </tr>
11804 <tr>
11805 <td>
11806                       <p><span class="command"><strong>NXDOMAIN</strong></span></p>
11807                     </td>
11808 <td>
11809                       <p><span class="command"><strong>RNXD</strong></span></p>
11810                     </td>
11811 <td>
11812                       <p>
11813                         NXDOMAIN received.
11814                       </p>
11815                     </td>
11816 </tr>
11817 <tr>
11818 <td>
11819                       <p><span class="command"><strong>SERVFAIL</strong></span></p>
11820                     </td>
11821 <td>
11822                       <p><span class="command"><strong>RFail</strong></span></p>
11823                     </td>
11824 <td>
11825                       <p>
11826                         SERVFAIL received.
11827                       </p>
11828                     </td>
11829 </tr>
11830 <tr>
11831 <td>
11832                       <p><span class="command"><strong>FORMERR</strong></span></p>
11833                     </td>
11834 <td>
11835                       <p><span class="command"><strong>RFErr</strong></span></p>
11836                     </td>
11837 <td>
11838                       <p>
11839                         FORMERR received.
11840                       </p>
11841                     </td>
11842 </tr>
11843 <tr>
11844 <td>
11845                       <p><span class="command"><strong>OtherError</strong></span></p>
11846                     </td>
11847 <td>
11848                       <p><span class="command"><strong>RErr</strong></span></p>
11849                     </td>
11850 <td>
11851                       <p>
11852                         Other errors received.
11853                       </p>
11854                     </td>
11855 </tr>
11856 <tr>
11857 <td>
11858                       <p><span class="command"><strong>EDNS0Fail</strong></span></p>
11859                                                  </td>
11860 <td>
11861                       <p><span class="command"><strong></strong></span></p>
11862                     </td>
11863 <td>
11864                       <p>
11865                         EDNS(0) query failures.
11866                       </p>
11867                     </td>
11868 </tr>
11869 <tr>
11870 <td>
11871                       <p><span class="command"><strong>Mismatch</strong></span></p>
11872                     </td>
11873 <td>
11874                       <p><span class="command"><strong>RDupR</strong></span></p>
11875                     </td>
11876 <td>
11877                       <p>
11878                         Mismatch responses received.
11879                         The DNS ID, response's source address,
11880                         and/or the response's source port does not
11881                         match what was expected.
11882                         (The port must be 53 or as defined by
11883                         the <span class="command"><strong>port</strong></span> option.)
11884                         This may be an indication of a cache
11885                         poisoning attempt.
11886                       </p>
11887                     </td>
11888 </tr>
11889 <tr>
11890 <td>
11891                       <p><span class="command"><strong>Truncated</strong></span></p>
11892                     </td>
11893 <td>
11894                       <p><span class="command"><strong></strong></span></p>
11895                     </td>
11896 <td>
11897                       <p>
11898                         Truncated responses received.
11899                       </p>
11900                     </td>
11901 </tr>
11902 <tr>
11903 <td>
11904                       <p><span class="command"><strong>Lame</strong></span></p>
11905                     </td>
11906 <td>
11907                       <p><span class="command"><strong>RLame</strong></span></p>
11908                     </td>
11909 <td>
11910                       <p>
11911                         Lame delegations received.
11912                       </p>
11913                     </td>
11914 </tr>
11915 <tr>
11916 <td>
11917                       <p><span class="command"><strong>Retry</strong></span></p>
11918                     </td>
11919 <td>
11920                       <p><span class="command"><strong>SDupQ</strong></span></p>
11921                     </td>
11922 <td>
11923                       <p>
11924                         Query retries performed.
11925                       </p>
11926                     </td>
11927 </tr>
11928 <tr>
11929 <td>
11930                       <p><span class="command"><strong>QueryAbort</strong></span></p>
11931                     </td>
11932 <td>
11933                       <p><span class="command"><strong></strong></span></p>
11934                     </td>
11935 <td>
11936                       <p>
11937                         Queries aborted due to quota control.
11938                       </p>
11939                     </td>
11940 </tr>
11941 <tr>
11942 <td>
11943                       <p><span class="command"><strong>QuerySockFail</strong></span></p>
11944                     </td>
11945 <td>
11946                       <p><span class="command"><strong></strong></span></p>
11947                     </td>
11948 <td>
11949                       <p>
11950                         Failures in opening query sockets.
11951                         One common reason for such failures is a
11952                         failure of opening a new socket due to a
11953                         limitation on file descriptors.
11954                       </p>
11955                     </td>
11956 </tr>
11957 <tr>
11958 <td>
11959                       <p><span class="command"><strong>QueryTimeout</strong></span></p>
11960                     </td>
11961 <td>
11962                       <p><span class="command"><strong></strong></span></p>
11963                     </td>
11964 <td>
11965                       <p>
11966                         Query timeouts.
11967                       </p>
11968                     </td>
11969 </tr>
11970 <tr>
11971 <td>
11972                       <p><span class="command"><strong>GlueFetchv4</strong></span></p>
11973                     </td>
11974 <td>
11975                       <p><span class="command"><strong>SSysQ</strong></span></p>
11976                     </td>
11977 <td>
11978                       <p>
11979                         IPv4 NS address fetches invoked.
11980                       </p>
11981                     </td>
11982 </tr>
11983 <tr>
11984 <td>
11985                       <p><span class="command"><strong>GlueFetchv6</strong></span></p>
11986                     </td>
11987 <td>
11988                       <p><span class="command"><strong>SSysQ</strong></span></p>
11989                     </td>
11990 <td>
11991                       <p>
11992                         IPv6 NS address fetches invoked.
11993                       </p>
11994                     </td>
11995 </tr>
11996 <tr>
11997 <td>
11998                       <p><span class="command"><strong>GlueFetchv4Fail</strong></span></p>
11999                     </td>
12000 <td>
12001                       <p><span class="command"><strong></strong></span></p>
12002                     </td>
12003 <td>
12004                       <p>
12005                         IPv4 NS address fetch failed.
12006                       </p>
12007                     </td>
12008 </tr>
12009 <tr>
12010 <td>
12011                       <p><span class="command"><strong>GlueFetchv6Fail</strong></span></p>
12012                     </td>
12013 <td>
12014                       <p><span class="command"><strong></strong></span></p>
12015                     </td>
12016 <td>
12017                       <p>
12018                         IPv6 NS address fetch failed.
12019                       </p>
12020                     </td>
12021 </tr>
12022 <tr>
12023 <td>
12024                       <p><span class="command"><strong>ValAttempt</strong></span></p>
12025                     </td>
12026 <td>
12027                       <p><span class="command"><strong></strong></span></p>
12028                     </td>
12029 <td>
12030                       <p>
12031                         DNSSEC validation attempted.
12032                       </p>
12033                     </td>
12034 </tr>
12035 <tr>
12036 <td>
12037                       <p><span class="command"><strong>ValOk</strong></span></p>
12038                     </td>
12039 <td>
12040                       <p><span class="command"><strong></strong></span></p>
12041                     </td>
12042 <td>
12043                       <p>
12044                         DNSSEC validation succeeded.
12045                       </p>
12046                     </td>
12047 </tr>
12048 <tr>
12049 <td>
12050                       <p><span class="command"><strong>ValNegOk</strong></span></p>
12051                     </td>
12052 <td>
12053                       <p><span class="command"><strong></strong></span></p>
12054                     </td>
12055 <td>
12056                       <p>
12057                         DNSSEC validation on negative information succeeded.
12058                       </p>
12059                     </td>
12060 </tr>
12061 <tr>
12062 <td>
12063                       <p><span class="command"><strong>ValFail</strong></span></p>
12064                     </td>
12065 <td>
12066                       <p><span class="command"><strong></strong></span></p>
12067                     </td>
12068 <td>
12069                       <p>
12070                         DNSSEC validation failed.
12071                       </p>
12072                     </td>
12073 </tr>
12074 <tr>
12075 <td>
12076                       <p><span class="command"><strong>QryRTTnn</strong></span></p>
12077                     </td>
12078 <td>
12079                       <p><span class="command"><strong></strong></span></p>
12080                     </td>
12081 <td>
12082                       <p>
12083                         Frequency table on round trip times (RTTs) of
12084                         queries.
12085                         Each <span class="command"><strong>nn</strong></span> specifies the corresponding
12086                         frequency.
12087                         In the sequence of
12088                         <span class="command"><strong>nn_1</strong></span>,
12089                         <span class="command"><strong>nn_2</strong></span>,
12090                         ...,
12091                         <span class="command"><strong>nn_m</strong></span>,
12092                         the value of <span class="command"><strong>nn_i</strong></span> is the
12093                         number of queries whose RTTs are between
12094                         <span class="command"><strong>nn_(i-1)</strong></span> (inclusive) and
12095                         <span class="command"><strong>nn_i</strong></span> (exclusive) milliseconds.
12096                         For the sake of convenience we define
12097                         <span class="command"><strong>nn_0</strong></span> to be 0.
12098                         The last entry should be represented as
12099                         <span class="command"><strong>nn_m+</strong></span>, which means the
12100                         number of queries whose RTTs are equal to or over
12101                         <span class="command"><strong>nn_m</strong></span> milliseconds.
12102                       </p>
12103                     </td>
12104 </tr>
12105 </tbody>
12106 </table></div>
12107 </div>
12108 <div class="section">
12109 <div class="titlepage"><div><div><h4 class="title">
12110 <a name="socket_stats"></a>Socket I/O Statistics Counters</h4></div></div></div>
12111 <p>
12112               Socket I/O statistics counters are defined per socket
12113               types, which are
12114               <span class="command"><strong>UDP4</strong></span> (UDP/IPv4),
12115               <span class="command"><strong>UDP6</strong></span> (UDP/IPv6),
12116               <span class="command"><strong>TCP4</strong></span> (TCP/IPv4),
12117               <span class="command"><strong>TCP6</strong></span> (TCP/IPv6),
12118               <span class="command"><strong>Unix</strong></span> (Unix Domain), and
12119               <span class="command"><strong>FDwatch</strong></span> (sockets opened outside the
12120               socket module).
12121               In the following table <span class="command"><strong>&lt;TYPE&gt;</strong></span>
12122               represents a socket type.
12123               Not all counters are available for all socket types;
12124               exceptions are noted in the description field.
12125             </p>
12126 <div class="informaltable"><table border="1">
12127 <colgroup>
12128 <col width="1.150in" class="1">
12129 <col width="3.350in" class="2">
12130 </colgroup>
12131 <tbody>
12132 <tr>
12133 <td>
12134                       <p>
12135                         <span class="emphasis"><em>Symbol</em></span>
12136                       </p>
12137                     </td>
12138 <td>
12139                       <p>
12140                         <span class="emphasis"><em>Description</em></span>
12141                       </p>
12142                     </td>
12143 </tr>
12144 <tr>
12145 <td>
12146                       <p><span class="command"><strong>&lt;TYPE&gt;Open</strong></span></p>
12147                     </td>
12148 <td>
12149                       <p>
12150                         Sockets opened successfully.
12151                         This counter is not applicable to the
12152                         <span class="command"><strong>FDwatch</strong></span> type.
12153                       </p>
12154                     </td>
12155 </tr>
12156 <tr>
12157 <td>
12158                       <p><span class="command"><strong>&lt;TYPE&gt;OpenFail</strong></span></p>
12159                     </td>
12160 <td>
12161                       <p>
12162                         Failures of opening sockets.
12163                         This counter is not applicable to the
12164                         <span class="command"><strong>FDwatch</strong></span> type.
12165                       </p>
12166                     </td>
12167 </tr>
12168 <tr>
12169 <td>
12170                       <p><span class="command"><strong>&lt;TYPE&gt;Close</strong></span></p>
12171                     </td>
12172 <td>
12173                       <p>
12174                         Sockets closed.
12175                       </p>
12176                     </td>
12177 </tr>
12178 <tr>
12179 <td>
12180                       <p><span class="command"><strong>&lt;TYPE&gt;BindFail</strong></span></p>
12181                     </td>
12182 <td>
12183                       <p>
12184                         Failures of binding sockets.
12185                       </p>
12186                     </td>
12187 </tr>
12188 <tr>
12189 <td>
12190                       <p><span class="command"><strong>&lt;TYPE&gt;ConnFail</strong></span></p>
12191                     </td>
12192 <td>
12193                       <p>
12194                         Failures of connecting sockets.
12195                       </p>
12196                     </td>
12197 </tr>
12198 <tr>
12199 <td>
12200                       <p><span class="command"><strong>&lt;TYPE&gt;Conn</strong></span></p>
12201                     </td>
12202 <td>
12203                       <p>
12204                         Connections established successfully.
12205                       </p>
12206                     </td>
12207 </tr>
12208 <tr>
12209 <td>
12210                       <p><span class="command"><strong>&lt;TYPE&gt;AcceptFail</strong></span></p>
12211                     </td>
12212 <td>
12213                       <p>
12214                         Failures of accepting incoming connection requests.
12215                         This counter is not applicable to the
12216                         <span class="command"><strong>UDP</strong></span> and
12217                         <span class="command"><strong>FDwatch</strong></span> types.
12218                       </p>
12219                     </td>
12220 </tr>
12221 <tr>
12222 <td>
12223                       <p><span class="command"><strong>&lt;TYPE&gt;Accept</strong></span></p>
12224                     </td>
12225 <td>
12226                       <p>
12227                         Incoming connections successfully accepted.
12228                         This counter is not applicable to the
12229                         <span class="command"><strong>UDP</strong></span> and
12230                         <span class="command"><strong>FDwatch</strong></span> types.
12231                       </p>
12232                     </td>
12233 </tr>
12234 <tr>
12235 <td>
12236                       <p><span class="command"><strong>&lt;TYPE&gt;SendErr</strong></span></p>
12237                     </td>
12238 <td>
12239                       <p>
12240                         Errors in socket send operations.
12241                         This counter corresponds
12242                         to <span class="command"><strong>SErr</strong></span> counter of
12243                         <span class="command"><strong>BIND</strong></span> 8.
12244                       </p>
12245                     </td>
12246 </tr>
12247 <tr>
12248 <td>
12249                       <p><span class="command"><strong>&lt;TYPE&gt;RecvErr</strong></span></p>
12250                     </td>
12251 <td>
12252                       <p>
12253                         Errors in socket receive operations.
12254                         This includes errors of send operations on a
12255                         connected UDP socket notified by an ICMP error
12256                         message.
12257                       </p>
12258                     </td>
12259 </tr>
12260 </tbody>
12261 </table></div>
12262 </div>
12263 <div class="section">
12264 <div class="titlepage"><div><div><h4 class="title">
12265 <a name="bind8_compatibility"></a>Compatibility with <span class="emphasis"><em>BIND</em></span> 8 Counters</h4></div></div></div>
12266 <p>
12267               Most statistics counters that were available
12268               in <span class="command"><strong>BIND</strong></span> 8 are also supported in
12269               <span class="command"><strong>BIND</strong></span> 9 as shown in the above tables.
12270               Here are notes about other counters that do not appear
12271               in these tables.
12272             </p>
12273 <div class="variablelist"><dl class="variablelist">
12274 <dt><span class="term"><span class="command"><strong>RFwdR,SFwdR</strong></span></span></dt>
12275 <dd><p>
12276                     These counters are not supported
12277                     because <span class="command"><strong>BIND</strong></span> 9 does not adopt
12278                     the notion of <span class="emphasis"><em>forwarding</em></span>
12279                     as <span class="command"><strong>BIND</strong></span> 8 did.
12280                   </p></dd>
12281 <dt><span class="term"><span class="command"><strong>RAXFR</strong></span></span></dt>
12282 <dd><p>
12283                     This counter is accessible in the Incoming Queries section.
12284                   </p></dd>
12285 <dt><span class="term"><span class="command"><strong>RIQ</strong></span></span></dt>
12286 <dd><p>
12287                     This counter is accessible in the Incoming Requests section.
12288                   </p></dd>
12289 <dt><span class="term"><span class="command"><strong>ROpts</strong></span></span></dt>
12290 <dd><p>
12291                     This counter is not supported
12292                     because <span class="command"><strong>BIND</strong></span> 9 does not care
12293                     about IP options in the first place.
12294                   </p></dd>
12295 </dl></div>
12296 </div>
12297 </div>
12298 </div>
12299 </div>
12300 <div class="navfooter">
12301 <hr>
12302 <table width="100%" summary="Navigation footer">
12303 <tr>
12304 <td width="40%" align="left">
12305 <a accesskey="p" href="Bv9ARM.ch05.html">Prev</a> </td>
12306 <td width="20%" align="center"> </td>
12307 <td width="40%" align="right"> <a accesskey="n" href="Bv9ARM.ch07.html">Next</a>
12308 </td>
12309 </tr>
12310 <tr>
12311 <td width="40%" align="left" valign="top">Chapter 5. The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver </td>
12312 <td width="20%" align="center"><a accesskey="h" href="Bv9ARM.html">Home</a></td>
12313 <td width="40%" align="right" valign="top"> Chapter 7. <acronym class="acronym">BIND</acronym> 9 Security Considerations</td>
12314 </tr>
12315 </table>
12316 </div>
12317 <p xmlns:db="http://docbook.org/ns/docbook" style="text-align: center;">BIND 9.9.9-P3 (Extended Support Version)</p>
12318 </body>
12319 </html>