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  21 <title>Chapter 6. BIND 9 Configuration Reference</title>
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  31 <tr><th colspan="3" align="center">Chapter 6. <acronym class="acronym">BIND</acronym> 9 Configuration Reference</th></tr>
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  42 <div class="chapter" lang="en">
  43 <div class="titlepage"><div><div><h2 class="title">
  44 <a name="Bv9ARM.ch06"></a>Chapter 6. <acronym class="acronym">BIND</acronym> 9 Configuration Reference</h2></div></div></div>
  45 <div class="toc">
  46 <p><b>Table of Contents</b></p>
  47 <dl>
  48 <dt><span class="sect1"><a href="Bv9ARM.ch06.html#configuration_file_elements">Configuration File Elements</a></span></dt>
  49 <dd><dl>
  50 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#address_match_lists">Address Match Lists</a></span></dt>
  51 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2573235">Comment Syntax</a></span></dt>
  52 </dl></dd>
  53 <dt><span class="sect1"><a href="Bv9ARM.ch06.html#Configuration_File_Grammar">Configuration File Grammar</a></span></dt>
  54 <dd><dl>
  55 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2573895"><span><strong class="command">acl</strong></span> Statement Grammar</a></span></dt>
  56 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#acl"><span><strong class="command">acl</strong></span> Statement Definition and
  57           Usage</a></span></dt>
  58 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574091"><span><strong class="command">controls</strong></span> Statement Grammar</a></span></dt>
  59 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage"><span><strong class="command">controls</strong></span> Statement Definition and
  60           Usage</a></span></dt>
  61 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574451"><span><strong class="command">include</strong></span> Statement Grammar</a></span></dt>
  62 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574468"><span><strong class="command">include</strong></span> Statement Definition and
  63           Usage</a></span></dt>
  64 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574628"><span><strong class="command">key</strong></span> Statement Grammar</a></span></dt>
  65 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574651"><span><strong class="command">key</strong></span> Statement Definition and Usage</a></span></dt>
  66 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574742"><span><strong class="command">logging</strong></span> Statement Grammar</a></span></dt>
  67 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574868"><span><strong class="command">logging</strong></span> Statement Definition and
  68           Usage</a></span></dt>
  69 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577079"><span><strong class="command">lwres</strong></span> Statement Grammar</a></span></dt>
  70 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577153"><span><strong class="command">lwres</strong></span> Statement Definition and Usage</a></span></dt>
  71 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577285"><span><strong class="command">masters</strong></span> Statement Grammar</a></span></dt>
  72 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577329"><span><strong class="command">masters</strong></span> Statement Definition and
  73           Usage</a></span></dt>
  74 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577350"><span><strong class="command">options</strong></span> Statement Grammar</a></span></dt>
  75 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#options"><span><strong class="command">options</strong></span> Statement Definition and
  76           Usage</a></span></dt>
  77 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#server_statement_grammar"><span><strong class="command">server</strong></span> Statement Grammar</a></span></dt>
  78 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#server_statement_definition_and_usage"><span><strong class="command">server</strong></span> Statement Definition and
  79             Usage</a></span></dt>
  80 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#statschannels"><span><strong class="command">statistics-channels</strong></span> Statement Grammar</a></span></dt>
  81 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2590471"><span><strong class="command">statistics-channels</strong></span> Statement Definition and
  82             Usage</a></span></dt>
  83 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#trusted-keys"><span><strong class="command">trusted-keys</strong></span> Statement Grammar</a></span></dt>
  84 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2590642"><span><strong class="command">trusted-keys</strong></span> Statement Definition
  85             and Usage</a></span></dt>
  86 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2590757"><span><strong class="command">managed-keys</strong></span> Statement Grammar</a></span></dt>
  87 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#managed-keys"><span><strong class="command">managed-keys</strong></span> Statement Definition
  88             and Usage</a></span></dt>
  89 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#view_statement_grammar"><span><strong class="command">view</strong></span> Statement Grammar</a></span></dt>
  90 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2591192"><span><strong class="command">view</strong></span> Statement Definition and Usage</a></span></dt>
  91 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#zone_statement_grammar"><span><strong class="command">zone</strong></span>
  92             Statement Grammar</a></span></dt>
  93 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2592901"><span><strong class="command">zone</strong></span> Statement Definition and Usage</a></span></dt>
  94 </dl></dd>
  95 <dt><span class="sect1"><a href="Bv9ARM.ch06.html#id2596587">Zone File</a></span></dt>
  96 <dd><dl>
  97 <dt><span class="sect2"><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>
  98 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2598681">Discussion of MX Records</a></span></dt>
  99 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#Setting_TTLs">Setting TTLs</a></span></dt>
 100 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2599297">Inverse Mapping in IPv4</a></span></dt>
 101 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2599492">Other Zone File Directives</a></span></dt>
 102 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2599765"><acronym class="acronym">BIND</acronym> Master File Extension: the  <span><strong class="command">$GENERATE</strong></span> Directive</a></span></dt>
 103 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#zonefile_format">Additional File Formats</a></span></dt>
 104 </dl></dd>
 105 <dt><span class="sect1"><a href="Bv9ARM.ch06.html#statistics">BIND9 Statistics</a></span></dt>
 106 <dd><dl><dt><span class="sect2"><a href="Bv9ARM.ch06.html#statistics_counters">Statistics Counters</a></span></dt></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="sect1" lang="en">
 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>
 135 <col>
 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><strong class="command">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 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><strong class="command">123</strong></span>,
 219                   <span><strong class="command">45.67</strong></span> or <span><strong class="command">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><strong class="command">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><strong class="command">fe80::1</strong></span> on the link
 257                   attached to the interface <span><strong class="command">ne0</strong></span>
 258                   can be specified as <span><strong class="command">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><strong class="command">127/8</strong></span> is the
 310                   network <span><strong class="command">127.0.0.0</strong></span> with
 311                   netmask <span><strong class="command">255.0.0.0</strong></span> and <span><strong class="command">1.2.3.0/28</strong></span> is
 312                   network <span><strong class="command">1.2.3.0</strong></span> with netmask <span><strong class="command">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><strong class="command">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="sect2" lang="en">
 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="sect3" lang="en">
 495 <div class="titlepage"><div><div><h4 class="title">
 496 <a name="id2572933"></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="sect3" lang="en">
 504 <div class="titlepage"><div><div><h4 class="title">
 505 <a name="id2572961"></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><strong class="command">listen-on</strong></span> and <span><strong class="command">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 type="disc">
 514 <li>an IP address (IPv4 or IPv6)</li>
 515 <li>an IP prefix (in `/' notation)</li>
 516 <li>
 517                 a key ID, as defined by the <span><strong class="command">key</strong></span>
 518                 statement
 519               </li>
 520 <li>the name of an address match list defined with
 521                 the <span><strong class="command">acl</strong></span> statement
 522               </li>
 523 <li>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><strong class="command">listen-on</strong></span> ports, or in a
 548             <span><strong class="command">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><strong class="command">allow-notify</strong></span>,
 555             <span><strong class="command">allow-recursion</strong></span>,
 556             <span><strong class="command">allow-recursion-on</strong></span>,
 557             <span><strong class="command">allow-query</strong></span>,
 558             <span><strong class="command">allow-query-on</strong></span>,
 559             <span><strong class="command">allow-query-cache</strong></span>,
 560             <span><strong class="command">allow-query-cache-on</strong></span>,
 561             <span><strong class="command">allow-transfer</strong></span>,
 562             <span><strong class="command">allow-update</strong></span>,
 563             <span><strong class="command">allow-update-forwarding</strong></span>, and
 564             <span><strong class="command">blackhole</strong></span> all use address match
 565             lists.  Similarly, the <span><strong class="command">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><strong class="command">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><strong class="command">! 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="sect2" lang="en">
 588 <div class="titlepage"><div><div><h3 class="title">
 589 <a name="id2573235"></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="sect3" lang="en">
 598 <div class="titlepage"><div><div><h4 class="title">
 599 <a name="id2573318"></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="sect3" lang="en">
 614 <div class="titlepage"><div><div><h4 class="title">
 615 <a name="id2573348"></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="sect1" lang="en">
 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>
 704 <col>
 705 </colgroup>
 706 <tbody>
 707 <tr>
 708 <td>
 709                 <p><span><strong class="command">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><strong class="command">controls</strong></span></p>
 721               </td>
 722 <td>
 723                 <p>
 724                   declares control channels to be used
 725                   by the <span><strong class="command">rndc</strong></span> utility.
 726                 </p>
 727               </td>
 728 </tr>
 729 <tr>
 730 <td>
 731                 <p><span><strong class="command">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><strong class="command">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><strong class="command">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><strong class="command">lwres</strong></span></p>
 764               </td>
 765 <td>
 766                 <p>
 767                   configures <span><strong class="command">named</strong></span> to
 768                   also act as a light-weight resolver daemon (<span><strong class="command">lwresd</strong></span>).
 769                 </p>
 770               </td>
 771 </tr>
 772 <tr>
 773 <td>
 774                 <p><span><strong class="command">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><strong class="command">masters</strong></span> or
 781                   <span><strong class="command">also-notify</strong></span> lists.
 782                 </p>
 783               </td>
 784 </tr>
 785 <tr>
 786 <td>
 787                 <p><span><strong class="command">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><strong class="command">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><strong class="command">statistics-channels</strong></span></p>
 810               </td>
 811 <td>
 812                 <p>
 813                   declares communication channels to get access to
 814                   <span><strong class="command">named</strong></span> statistics.
 815                 </p>
 816               </td>
 817 </tr>
 818 <tr>
 819 <td>
 820                 <p><span><strong class="command">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><strong class="command">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><strong class="command">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><strong class="command">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><strong class="command">logging</strong></span> and
 863         <span><strong class="command">options</strong></span> statements may only occur once
 864         per
 865         configuration.
 866       </p>
 867 <div class="sect2" lang="en">
 868 <div class="titlepage"><div><div><h3 class="title">
 869 <a name="id2573895"></a><span><strong class="command">acl</strong></span> Statement Grammar</h3></div></div></div>
 870 <pre class="programlisting"><span><strong class="command">acl</strong></span> acl-name {
 871     address_match_list
 872 };
 873 </pre>
 874 </div>
 875 <div class="sect2" lang="en">
 876 <div class="titlepage"><div><div><h3 class="title">
 877 <a name="acl"></a><span><strong class="command">acl</strong></span> Statement Definition and
 878           Usage</h3></div></div></div>
 879 <p>
 880           The <span><strong class="command">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           Note that an address match list's name must be defined
 886           with <span><strong class="command">acl</strong></span> before it can be used
 887           elsewhere; no forward references are allowed.
 888         </p>
 889 <p>
 890           The following ACLs are built-in:
 891         </p>
 892 <div class="informaltable"><table border="1">
 893 <colgroup>
 894 <col>
 895 <col>
 896 </colgroup>
 897 <tbody>
 898 <tr>
 899 <td>
 900                   <p><span><strong class="command">any</strong></span></p>
 901                 </td>
 902 <td>
 903                   <p>
 904                     Matches all hosts.
 905                   </p>
 906                 </td>
 907 </tr>
 908 <tr>
 909 <td>
 910                   <p><span><strong class="command">none</strong></span></p>
 911                 </td>
 912 <td>
 913                   <p>
 914                     Matches no hosts.
 915                   </p>
 916                 </td>
 917 </tr>
 918 <tr>
 919 <td>
 920                   <p><span><strong class="command">localhost</strong></span></p>
 921                 </td>
 922 <td>
 923                   <p>
 924                     Matches the IPv4 and IPv6 addresses of all network
 925                     interfaces on the system.  When addresses are
 926                     added or removed, the <span><strong class="command">localhost</strong></span>
 927                     ACL element is updated to reflect the changes.
 928                   </p>
 929                 </td>
 930 </tr>
 931 <tr>
 932 <td>
 933                   <p><span><strong class="command">localnets</strong></span></p>
 934                 </td>
 935 <td>
 936                   <p>
 937                     Matches any host on an IPv4 or IPv6 network
 938                     for which the system has an interface.
 939                     When addresses are added or removed,
 940                     the <span><strong class="command">localnets</strong></span>
 941                     ACL element is updated to reflect the changes.
 942                     Some systems do not provide a way to determine the prefix
 943                     lengths of
 944                     local IPv6 addresses.
 945                     In such a case, <span><strong class="command">localnets</strong></span>
 946                     only matches the local
 947                     IPv6 addresses, just like <span><strong class="command">localhost</strong></span>.
 948                   </p>
 949                 </td>
 950 </tr>
 951 </tbody>
 952 </table></div>
 953 </div>
 954 <div class="sect2" lang="en">
 955 <div class="titlepage"><div><div><h3 class="title">
 956 <a name="id2574091"></a><span><strong class="command">controls</strong></span> Statement Grammar</h3></div></div></div>
 957 <pre class="programlisting"><span><strong class="command">controls</strong></span> {
 958    [ inet ( ip_addr | * ) [ port ip_port ]
 959                 allow { <em class="replaceable"><code> address_match_list </code></em> }
 960                 keys { <em class="replaceable"><code>key_list</code></em> }; ]
 961    [ inet ...; ]
 962    [ 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>
 963      keys { <em class="replaceable"><code>key_list</code></em> }; ]
 964    [ unix ...; ]
 965 };
 966 </pre>
 967 </div>
 968 <div class="sect2" lang="en">
 969 <div class="titlepage"><div><div><h3 class="title">
 970 <a name="controls_statement_definition_and_usage"></a><span><strong class="command">controls</strong></span> Statement Definition and
 971           Usage</h3></div></div></div>
 972 <p>
 973           The <span><strong class="command">controls</strong></span> statement declares control
 974           channels to be used by system administrators to control the
 975           operation of the name server. These control channels are
 976           used by the <span><strong class="command">rndc</strong></span> utility to send
 977           commands to and retrieve non-DNS results from a name server.
 978         </p>
 979 <p>
 980           An <span><strong class="command">inet</strong></span> control channel is a TCP socket
 981           listening at the specified <span><strong class="command">ip_port</strong></span> on the
 982           specified <span><strong class="command">ip_addr</strong></span>, which can be an IPv4 or IPv6
 983           address.  An <span><strong class="command">ip_addr</strong></span> of <code class="literal">*</code> (asterisk) is
 984           interpreted as the IPv4 wildcard address; connections will be
 985           accepted on any of the system's IPv4 addresses.
 986           To listen on the IPv6 wildcard address,
 987           use an <span><strong class="command">ip_addr</strong></span> of <code class="literal">::</code>.
 988           If you will only use <span><strong class="command">rndc</strong></span> on the local host,
 989           using the loopback address (<code class="literal">127.0.0.1</code>
 990           or <code class="literal">::1</code>) is recommended for maximum security.
 991         </p>
 992 <p>
 993           If no port is specified, port 953 is used. The asterisk
 994           "<code class="literal">*</code>" cannot be used for <span><strong class="command">ip_port</strong></span>.
 995         </p>
 996 <p>
 997           The ability to issue commands over the control channel is
 998           restricted by the <span><strong class="command">allow</strong></span> and
 999           <span><strong class="command">keys</strong></span> clauses.
1000           Connections to the control channel are permitted based on the
1001           <span><strong class="command">address_match_list</strong></span>.  This is for simple
1002           IP address based filtering only; any <span><strong class="command">key_id</strong></span>
1003           elements of the <span><strong class="command">address_match_list</strong></span>
1004           are ignored.
1005         </p>
1006 <p>
1007           A <span><strong class="command">unix</strong></span> control channel is a UNIX domain
1008           socket listening at the specified path in the file system.
1009           Access to the socket is specified by the <span><strong class="command">perm</strong></span>,
1010           <span><strong class="command">owner</strong></span> and <span><strong class="command">group</strong></span> clauses.
1011           Note on some platforms (SunOS and Solaris) the permissions
1012           (<span><strong class="command">perm</strong></span>) are applied to the parent directory
1013           as the permissions on the socket itself are ignored.
1014         </p>
1015 <p>
1016           The primary authorization mechanism of the command
1017           channel is the <span><strong class="command">key_list</strong></span>, which
1018           contains a list of <span><strong class="command">key_id</strong></span>s.
1019           Each <span><strong class="command">key_id</strong></span> in the <span><strong class="command">key_list</strong></span>
1020           is authorized to execute commands over the control channel.
1021           See <a href="Bv9ARM.ch03.html#rndc">Remote Name Daemon Control application</a> in <a href="Bv9ARM.ch03.html#admin_tools" title="Administrative Tools">the section called &#8220;Administrative Tools&#8221;</a>)
1022           for information about configuring keys in <span><strong class="command">rndc</strong></span>.
1023         </p>
1024 <p>
1025           If no <span><strong class="command">controls</strong></span> statement is present,
1026           <span><strong class="command">named</strong></span> will set up a default
1027           control channel listening on the loopback address 127.0.0.1
1028           and its IPv6 counterpart ::1.
1029           In this case, and also when the <span><strong class="command">controls</strong></span> statement
1030           is present but does not have a <span><strong class="command">keys</strong></span> clause,
1031           <span><strong class="command">named</strong></span> will attempt to load the command channel key
1032           from the file <code class="filename">rndc.key</code> in
1033           <code class="filename">/etc</code> (or whatever <code class="varname">sysconfdir</code>
1034           was specified as when <acronym class="acronym">BIND</acronym> was built).
1035           To create a <code class="filename">rndc.key</code> file, run
1036           <strong class="userinput"><code>rndc-confgen -a</code></strong>.
1037         </p>
1038 <p>
1039           The <code class="filename">rndc.key</code> feature was created to
1040           ease the transition of systems from <acronym class="acronym">BIND</acronym> 8,
1041           which did not have digital signatures on its command channel
1042           messages and thus did not have a <span><strong class="command">keys</strong></span> clause.
1043
1044           It makes it possible to use an existing <acronym class="acronym">BIND</acronym> 8
1045           configuration file in <acronym class="acronym">BIND</acronym> 9 unchanged,
1046           and still have <span><strong class="command">rndc</strong></span> work the same way
1047           <span><strong class="command">ndc</strong></span> worked in BIND 8, simply by executing the
1048           command <strong class="userinput"><code>rndc-confgen -a</code></strong> after BIND 9 is
1049           installed.
1050         </p>
1051 <p>
1052           Since the <code class="filename">rndc.key</code> feature
1053           is only intended to allow the backward-compatible usage of
1054           <acronym class="acronym">BIND</acronym> 8 configuration files, this
1055           feature does not
1056           have a high degree of configurability.  You cannot easily change
1057           the key name or the size of the secret, so you should make a
1058           <code class="filename">rndc.conf</code> with your own key if you
1059           wish to change
1060           those things.  The <code class="filename">rndc.key</code> file
1061           also has its
1062           permissions set such that only the owner of the file (the user that
1063           <span><strong class="command">named</strong></span> is running as) can access it.
1064           If you
1065           desire greater flexibility in allowing other users to access
1066           <span><strong class="command">rndc</strong></span> commands, then you need to create
1067           a
1068           <code class="filename">rndc.conf</code> file and make it group
1069           readable by a group
1070           that contains the users who should have access.
1071         </p>
1072 <p>
1073           To disable the command channel, use an empty
1074           <span><strong class="command">controls</strong></span> statement:
1075           <span><strong class="command">controls { };</strong></span>.
1076         </p>
1077 </div>
1078 <div class="sect2" lang="en">
1079 <div class="titlepage"><div><div><h3 class="title">
1080 <a name="id2574451"></a><span><strong class="command">include</strong></span> Statement Grammar</h3></div></div></div>
1081 <pre class="programlisting"><span><strong class="command">include</strong></span> <em class="replaceable"><code>filename</code></em>;</pre>
1082 </div>
1083 <div class="sect2" lang="en">
1084 <div class="titlepage"><div><div><h3 class="title">
1085 <a name="id2574468"></a><span><strong class="command">include</strong></span> Statement Definition and
1086           Usage</h3></div></div></div>
1087 <p>
1088           The <span><strong class="command">include</strong></span> statement inserts the
1089           specified file at the point where the <span><strong class="command">include</strong></span>
1090           statement is encountered. The <span><strong class="command">include</strong></span>
1091                 statement facilitates the administration of configuration
1092           files
1093           by permitting the reading or writing of some things but not
1094           others. For example, the statement could include private keys
1095           that are readable only by the name server.
1096         </p>
1097 </div>
1098 <div class="sect2" lang="en">
1099 <div class="titlepage"><div><div><h3 class="title">
1100 <a name="id2574628"></a><span><strong class="command">key</strong></span> Statement Grammar</h3></div></div></div>
1101 <pre class="programlisting"><span><strong class="command">key</strong></span> <em class="replaceable"><code>key_id</code></em> {
1102     algorithm <em class="replaceable"><code>string</code></em>;
1103     secret <em class="replaceable"><code>string</code></em>;
1104 };
1105 </pre>
1106 </div>
1107 <div class="sect2" lang="en">
1108 <div class="titlepage"><div><div><h3 class="title">
1109 <a name="id2574651"></a><span><strong class="command">key</strong></span> Statement Definition and Usage</h3></div></div></div>
1110 <p>
1111           The <span><strong class="command">key</strong></span> statement defines a shared
1112           secret key for use with TSIG (see <a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
1113           or the command channel
1114           (see <a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and
1115           Usage">the section called &#8220;<span><strong class="command">controls</strong></span> Statement Definition and
1116           Usage&#8221;</a>).
1117         </p>
1118 <p>
1119           The <span><strong class="command">key</strong></span> statement can occur at the
1120           top level
1121           of the configuration file or inside a <span><strong class="command">view</strong></span>
1122           statement.  Keys defined in top-level <span><strong class="command">key</strong></span>
1123           statements can be used in all views.  Keys intended for use in
1124           a <span><strong class="command">controls</strong></span> statement
1125           (see <a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and
1126           Usage">the section called &#8220;<span><strong class="command">controls</strong></span> Statement Definition and
1127           Usage&#8221;</a>)
1128           must be defined at the top level.
1129         </p>
1130 <p>
1131           The <em class="replaceable"><code>key_id</code></em>, also known as the
1132           key name, is a domain name uniquely identifying the key. It can
1133           be used in a <span><strong class="command">server</strong></span>
1134           statement to cause requests sent to that
1135           server to be signed with this key, or in address match lists to
1136           verify that incoming requests have been signed with a key
1137           matching this name, algorithm, and secret.
1138         </p>
1139 <p>
1140           The <em class="replaceable"><code>algorithm_id</code></em> is a string
1141           that specifies a security/authentication algorithm.  Named
1142           supports <code class="literal">hmac-md5</code>,
1143           <code class="literal">hmac-sha1</code>, <code class="literal">hmac-sha224</code>,
1144           <code class="literal">hmac-sha256</code>, <code class="literal">hmac-sha384</code>
1145           and <code class="literal">hmac-sha512</code> TSIG authentication.
1146           Truncated hashes are supported by appending the minimum
1147           number of required bits preceded by a dash, e.g.
1148           <code class="literal">hmac-sha1-80</code>.  The
1149           <em class="replaceable"><code>secret_string</code></em> is the secret
1150           to be used by the algorithm, and is treated as a base-64
1151           encoded string.
1152         </p>
1153 </div>
1154 <div class="sect2" lang="en">
1155 <div class="titlepage"><div><div><h3 class="title">
1156 <a name="id2574742"></a><span><strong class="command">logging</strong></span> Statement Grammar</h3></div></div></div>
1157 <pre class="programlisting"><span><strong class="command">logging</strong></span> {
1158    [ <span><strong class="command">channel</strong></span> <em class="replaceable"><code>channel_name</code></em> {
1159      ( <span><strong class="command">file</strong></span> <em class="replaceable"><code>path_name</code></em>
1160          [ <span><strong class="command">versions</strong></span> ( <em class="replaceable"><code>number</code></em> | <span><strong class="command">unlimited</strong></span> ) ]
1161          [ <span><strong class="command">size</strong></span> <em class="replaceable"><code>size_spec</code></em> ]
1162        | <span><strong class="command">syslog</strong></span> <em class="replaceable"><code>syslog_facility</code></em>
1163        | <span><strong class="command">stderr</strong></span>
1164        | <span><strong class="command">null</strong></span> );
1165      [ <span><strong class="command">severity</strong></span> (<code class="option">critical</code> | <code class="option">error</code> | <code class="option">warning</code> | <code class="option">notice</code> |
1166                  <code class="option">info</code> | <code class="option">debug</code> [ <em class="replaceable"><code>level</code></em> ] | <code class="option">dynamic</code> ); ]
1167      [ <span><strong class="command">print-category</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1168      [ <span><strong class="command">print-severity</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1169      [ <span><strong class="command">print-time</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1170    }; ]
1171    [ <span><strong class="command">category</strong></span> <em class="replaceable"><code>category_name</code></em> {
1172      <em class="replaceable"><code>channel_name</code></em> ; [ <em class="replaceable"><code>channel_name</code></em> ; ... ]
1173    }; ]
1174    ...
1175 };
1176 </pre>
1177 </div>
1178 <div class="sect2" lang="en">
1179 <div class="titlepage"><div><div><h3 class="title">
1180 <a name="id2574868"></a><span><strong class="command">logging</strong></span> Statement Definition and
1181           Usage</h3></div></div></div>
1182 <p>
1183           The <span><strong class="command">logging</strong></span> statement configures a
1184           wide
1185           variety of logging options for the name server. Its <span><strong class="command">channel</strong></span> phrase
1186           associates output methods, format options and severity levels with
1187           a name that can then be used with the <span><strong class="command">category</strong></span> phrase
1188           to select how various classes of messages are logged.
1189         </p>
1190 <p>
1191           Only one <span><strong class="command">logging</strong></span> statement is used to
1192           define
1193           as many channels and categories as are wanted. If there is no <span><strong class="command">logging</strong></span> statement,
1194           the logging configuration will be:
1195         </p>
1196 <pre class="programlisting">logging {
1197      category default { default_syslog; default_debug; };
1198      category unmatched { null; };
1199 };
1200 </pre>
1201 <p>
1202           In <acronym class="acronym">BIND</acronym> 9, the logging configuration
1203           is only established when
1204           the entire configuration file has been parsed.  In <acronym class="acronym">BIND</acronym> 8, it was
1205           established as soon as the <span><strong class="command">logging</strong></span>
1206           statement
1207           was parsed. When the server is starting up, all logging messages
1208           regarding syntax errors in the configuration file go to the default
1209           channels, or to standard error if the "<code class="option">-g</code>" option
1210           was specified.
1211         </p>
1212 <div class="sect3" lang="en">
1213 <div class="titlepage"><div><div><h4 class="title">
1214 <a name="id2574920"></a>The <span><strong class="command">channel</strong></span> Phrase</h4></div></div></div>
1215 <p>
1216             All log output goes to one or more <span class="emphasis"><em>channels</em></span>;
1217             you can make as many of them as you want.
1218           </p>
1219 <p>
1220             Every channel definition must include a destination clause that
1221             says whether messages selected for the channel go to a file, to a
1222             particular syslog facility, to the standard error stream, or are
1223             discarded. It can optionally also limit the message severity level
1224             that will be accepted by the channel (the default is
1225             <span><strong class="command">info</strong></span>), and whether to include a
1226             <span><strong class="command">named</strong></span>-generated time stamp, the
1227             category name
1228             and/or severity level (the default is not to include any).
1229           </p>
1230 <p>
1231             The <span><strong class="command">null</strong></span> destination clause
1232             causes all messages sent to the channel to be discarded;
1233             in that case, other options for the channel are meaningless.
1234           </p>
1235 <p>
1236             The <span><strong class="command">file</strong></span> destination clause directs
1237             the channel
1238             to a disk file.  It can include limitations
1239             both on how large the file is allowed to become, and how many
1240             versions
1241             of the file will be saved each time the file is opened.
1242           </p>
1243 <p>
1244             If you use the <span><strong class="command">versions</strong></span> log file
1245             option, then
1246             <span><strong class="command">named</strong></span> will retain that many backup
1247             versions of the file by
1248             renaming them when opening.  For example, if you choose to keep
1249             three old versions
1250             of the file <code class="filename">lamers.log</code>, then just
1251             before it is opened
1252             <code class="filename">lamers.log.1</code> is renamed to
1253             <code class="filename">lamers.log.2</code>, <code class="filename">lamers.log.0</code> is renamed
1254             to <code class="filename">lamers.log.1</code>, and <code class="filename">lamers.log</code> is
1255             renamed to <code class="filename">lamers.log.0</code>.
1256             You can say <span><strong class="command">versions unlimited</strong></span> to
1257             not limit
1258             the number of versions.
1259             If a <span><strong class="command">size</strong></span> option is associated with
1260             the log file,
1261             then renaming is only done when the file being opened exceeds the
1262             indicated size.  No backup versions are kept by default; any
1263             existing
1264             log file is simply appended.
1265           </p>
1266 <p>
1267             The <span><strong class="command">size</strong></span> option for files is used
1268             to limit log
1269             growth. If the file ever exceeds the size, then <span><strong class="command">named</strong></span> will
1270             stop writing to the file unless it has a <span><strong class="command">versions</strong></span> option
1271             associated with it.  If backup versions are kept, the files are
1272             rolled as
1273             described above and a new one begun.  If there is no
1274             <span><strong class="command">versions</strong></span> option, no more data will
1275             be written to the log
1276             until some out-of-band mechanism removes or truncates the log to
1277             less than the
1278             maximum size.  The default behavior is not to limit the size of
1279             the
1280             file.
1281           </p>
1282 <p>
1283             Example usage of the <span><strong class="command">size</strong></span> and
1284             <span><strong class="command">versions</strong></span> options:
1285           </p>
1286 <pre class="programlisting">channel an_example_channel {
1287     file "example.log" versions 3 size 20m;
1288     print-time yes;
1289     print-category yes;
1290 };
1291 </pre>
1292 <p>
1293             The <span><strong class="command">syslog</strong></span> destination clause
1294             directs the
1295             channel to the system log.  Its argument is a
1296             syslog facility as described in the <span><strong class="command">syslog</strong></span> man
1297             page. Known facilities are <span><strong class="command">kern</strong></span>, <span><strong class="command">user</strong></span>,
1298             <span><strong class="command">mail</strong></span>, <span><strong class="command">daemon</strong></span>, <span><strong class="command">auth</strong></span>,
1299             <span><strong class="command">syslog</strong></span>, <span><strong class="command">lpr</strong></span>, <span><strong class="command">news</strong></span>,
1300             <span><strong class="command">uucp</strong></span>, <span><strong class="command">cron</strong></span>, <span><strong class="command">authpriv</strong></span>,
1301             <span><strong class="command">ftp</strong></span>, <span><strong class="command">local0</strong></span>, <span><strong class="command">local1</strong></span>,
1302             <span><strong class="command">local2</strong></span>, <span><strong class="command">local3</strong></span>, <span><strong class="command">local4</strong></span>,
1303             <span><strong class="command">local5</strong></span>, <span><strong class="command">local6</strong></span> and
1304             <span><strong class="command">local7</strong></span>, however not all facilities
1305             are supported on
1306             all operating systems.
1307             How <span><strong class="command">syslog</strong></span> will handle messages
1308             sent to
1309             this facility is described in the <span><strong class="command">syslog.conf</strong></span> man
1310             page. If you have a system which uses a very old version of <span><strong class="command">syslog</strong></span> that
1311             only uses two arguments to the <span><strong class="command">openlog()</strong></span> function,
1312             then this clause is silently ignored.
1313           </p>
1314 <p>
1315             On Windows machines syslog messages are directed to the EventViewer.
1316           </p>
1317 <p>
1318             The <span><strong class="command">severity</strong></span> clause works like <span><strong class="command">syslog</strong></span>'s
1319             "priorities", except that they can also be used if you are writing
1320             straight to a file rather than using <span><strong class="command">syslog</strong></span>.
1321             Messages which are not at least of the severity level given will
1322             not be selected for the channel; messages of higher severity
1323             levels
1324             will be accepted.
1325           </p>
1326 <p>
1327             If you are using <span><strong class="command">syslog</strong></span>, then the <span><strong class="command">syslog.conf</strong></span> priorities
1328             will also determine what eventually passes through. For example,
1329             defining a channel facility and severity as <span><strong class="command">daemon</strong></span> and <span><strong class="command">debug</strong></span> but
1330             only logging <span><strong class="command">daemon.warning</strong></span> via <span><strong class="command">syslog.conf</strong></span> will
1331             cause messages of severity <span><strong class="command">info</strong></span> and
1332             <span><strong class="command">notice</strong></span> to
1333             be dropped. If the situation were reversed, with <span><strong class="command">named</strong></span> writing
1334             messages of only <span><strong class="command">warning</strong></span> or higher,
1335             then <span><strong class="command">syslogd</strong></span> would
1336             print all messages it received from the channel.
1337           </p>
1338 <p>
1339             The <span><strong class="command">stderr</strong></span> destination clause
1340             directs the
1341             channel to the server's standard error stream.  This is intended
1342             for
1343             use when the server is running as a foreground process, for
1344             example
1345             when debugging a configuration.
1346           </p>
1347 <p>
1348             The server can supply extensive debugging information when
1349             it is in debugging mode. If the server's global debug level is
1350             greater
1351             than zero, then debugging mode will be active. The global debug
1352             level is set either by starting the <span><strong class="command">named</strong></span> server
1353             with the <code class="option">-d</code> flag followed by a positive integer,
1354             or by running <span><strong class="command">rndc trace</strong></span>.
1355             The global debug level
1356             can be set to zero, and debugging mode turned off, by running <span><strong class="command">rndc
1357 notrace</strong></span>. All debugging messages in the server have a debug
1358             level, and higher debug levels give more detailed output. Channels
1359             that specify a specific debug severity, for example:
1360           </p>
1361 <pre class="programlisting">channel specific_debug_level {
1362     file "foo";
1363     severity debug 3;
1364 };
1365 </pre>
1366 <p>
1367             will get debugging output of level 3 or less any time the
1368             server is in debugging mode, regardless of the global debugging
1369             level. Channels with <span><strong class="command">dynamic</strong></span>
1370             severity use the
1371             server's global debug level to determine what messages to print.
1372           </p>
1373 <p>
1374             If <span><strong class="command">print-time</strong></span> has been turned on,
1375             then
1376             the date and time will be logged. <span><strong class="command">print-time</strong></span> may
1377             be specified for a <span><strong class="command">syslog</strong></span> channel,
1378             but is usually
1379             pointless since <span><strong class="command">syslog</strong></span> also logs
1380             the date and
1381             time. If <span><strong class="command">print-category</strong></span> is
1382             requested, then the
1383             category of the message will be logged as well. Finally, if <span><strong class="command">print-severity</strong></span> is
1384             on, then the severity level of the message will be logged. The <span><strong class="command">print-</strong></span> options may
1385             be used in any combination, and will always be printed in the
1386             following
1387             order: time, category, severity. Here is an example where all
1388             three <span><strong class="command">print-</strong></span> options
1389             are on:
1390           </p>
1391 <p>
1392             <code class="computeroutput">28-Feb-2000 15:05:32.863 general: notice: running</code>
1393           </p>
1394 <p>
1395             There are four predefined channels that are used for
1396             <span><strong class="command">named</strong></span>'s default logging as follows.
1397             How they are
1398             used is described in <a href="Bv9ARM.ch06.html#the_category_phrase" title="The category Phrase">the section called &#8220;The <span><strong class="command">category</strong></span> Phrase&#8221;</a>.
1399           </p>
1400 <pre class="programlisting">channel default_syslog {
1401     // send to syslog's daemon facility
1402     syslog daemon;
1403     // only send priority info and higher
1404     severity info;
1405
1406 channel default_debug {
1407     // write to named.run in the working directory
1408     // Note: stderr is used instead of "named.run" if
1409     // the server is started with the '-f' option.
1410     file "named.run";
1411     // log at the server's current debug level
1412     severity dynamic;
1413 };
1414
1415 channel default_stderr {
1416     // writes to stderr
1417     stderr;
1418     // only send priority info and higher
1419     severity info;
1420 };
1421
1422 channel null {
1423    // toss anything sent to this channel
1424    null;
1425 };
1426 </pre>
1427 <p>
1428             The <span><strong class="command">default_debug</strong></span> channel has the
1429             special
1430             property that it only produces output when the server's debug
1431             level is
1432             nonzero.  It normally writes to a file called <code class="filename">named.run</code>
1433             in the server's working directory.
1434           </p>
1435 <p>
1436             For security reasons, when the "<code class="option">-u</code>"
1437             command line option is used, the <code class="filename">named.run</code> file
1438             is created only after <span><strong class="command">named</strong></span> has
1439             changed to the
1440             new UID, and any debug output generated while <span><strong class="command">named</strong></span> is
1441             starting up and still running as root is discarded.  If you need
1442             to capture this output, you must run the server with the "<code class="option">-g</code>"
1443             option and redirect standard error to a file.
1444           </p>
1445 <p>
1446             Once a channel is defined, it cannot be redefined. Thus you
1447             cannot alter the built-in channels directly, but you can modify
1448             the default logging by pointing categories at channels you have
1449             defined.
1450           </p>
1451 </div>
1452 <div class="sect3" lang="en">
1453 <div class="titlepage"><div><div><h4 class="title">
1454 <a name="the_category_phrase"></a>The <span><strong class="command">category</strong></span> Phrase</h4></div></div></div>
1455 <p>
1456             There are many categories, so you can send the logs you want
1457             to see wherever you want, without seeing logs you don't want. If
1458             you don't specify a list of channels for a category, then log
1459             messages
1460             in that category will be sent to the <span><strong class="command">default</strong></span> category
1461             instead. If you don't specify a default category, the following
1462             "default default" is used:
1463           </p>
1464 <pre class="programlisting">category default { default_syslog; default_debug; };
1465 </pre>
1466 <p>
1467             As an example, let's say you want to log security events to
1468             a file, but you also want keep the default logging behavior. You'd
1469             specify the following:
1470           </p>
1471 <pre class="programlisting">channel my_security_channel {
1472     file "my_security_file";
1473     severity info;
1474 };
1475 category security {
1476     my_security_channel;
1477     default_syslog;
1478     default_debug;
1479 };</pre>
1480 <p>
1481             To discard all messages in a category, specify the <span><strong class="command">null</strong></span> channel:
1482           </p>
1483 <pre class="programlisting">category xfer-out { null; };
1484 category notify { null; };
1485 </pre>
1486 <p>
1487             Following are the available categories and brief descriptions
1488             of the types of log information they contain. More
1489             categories may be added in future <acronym class="acronym">BIND</acronym> releases.
1490           </p>
1491 <div class="informaltable"><table border="1">
1492 <colgroup>
1493 <col>
1494 <col>
1495 </colgroup>
1496 <tbody>
1497 <tr>
1498 <td>
1499                     <p><span><strong class="command">default</strong></span></p>
1500                   </td>
1501 <td>
1502                     <p>
1503                       The default category defines the logging
1504                       options for those categories where no specific
1505                       configuration has been
1506                       defined.
1507                     </p>
1508                   </td>
1509 </tr>
1510 <tr>
1511 <td>
1512                     <p><span><strong class="command">general</strong></span></p>
1513                   </td>
1514 <td>
1515                     <p>
1516                       The catch-all. Many things still aren't
1517                       classified into categories, and they all end up here.
1518                     </p>
1519                   </td>
1520 </tr>
1521 <tr>
1522 <td>
1523                     <p><span><strong class="command">database</strong></span></p>
1524                   </td>
1525 <td>
1526                     <p>
1527                       Messages relating to the databases used
1528                       internally by the name server to store zone and cache
1529                       data.
1530                     </p>
1531                   </td>
1532 </tr>
1533 <tr>
1534 <td>
1535                     <p><span><strong class="command">security</strong></span></p>
1536                   </td>
1537 <td>
1538                     <p>
1539                       Approval and denial of requests.
1540                     </p>
1541                   </td>
1542 </tr>
1543 <tr>
1544 <td>
1545                     <p><span><strong class="command">config</strong></span></p>
1546                   </td>
1547 <td>
1548                     <p>
1549                       Configuration file parsing and processing.
1550                     </p>
1551                   </td>
1552 </tr>
1553 <tr>
1554 <td>
1555                     <p><span><strong class="command">resolver</strong></span></p>
1556                   </td>
1557 <td>
1558                     <p>
1559                       DNS resolution, such as the recursive
1560                       lookups performed on behalf of clients by a caching name
1561                       server.
1562                     </p>
1563                   </td>
1564 </tr>
1565 <tr>
1566 <td>
1567                     <p><span><strong class="command">xfer-in</strong></span></p>
1568                   </td>
1569 <td>
1570                     <p>
1571                       Zone transfers the server is receiving.
1572                     </p>
1573                   </td>
1574 </tr>
1575 <tr>
1576 <td>
1577                     <p><span><strong class="command">xfer-out</strong></span></p>
1578                   </td>
1579 <td>
1580                     <p>
1581                       Zone transfers the server is sending.
1582                     </p>
1583                   </td>
1584 </tr>
1585 <tr>
1586 <td>
1587                     <p><span><strong class="command">notify</strong></span></p>
1588                   </td>
1589 <td>
1590                     <p>
1591                       The NOTIFY protocol.
1592                     </p>
1593                   </td>
1594 </tr>
1595 <tr>
1596 <td>
1597                     <p><span><strong class="command">client</strong></span></p>
1598                   </td>
1599 <td>
1600                     <p>
1601                       Processing of client requests.
1602                     </p>
1603                   </td>
1604 </tr>
1605 <tr>
1606 <td>
1607                     <p><span><strong class="command">unmatched</strong></span></p>
1608                   </td>
1609 <td>
1610                     <p>
1611                       Messages that <span><strong class="command">named</strong></span> was unable to determine the
1612                       class of or for which there was no matching <span><strong class="command">view</strong></span>.
1613                       A one line summary is also logged to the <span><strong class="command">client</strong></span> category.
1614                       This category is best sent to a file or stderr, by
1615                       default it is sent to
1616                       the <span><strong class="command">null</strong></span> channel.
1617                     </p>
1618                   </td>
1619 </tr>
1620 <tr>
1621 <td>
1622                     <p><span><strong class="command">network</strong></span></p>
1623                   </td>
1624 <td>
1625                     <p>
1626                       Network operations.
1627                     </p>
1628                   </td>
1629 </tr>
1630 <tr>
1631 <td>
1632                     <p><span><strong class="command">update</strong></span></p>
1633                   </td>
1634 <td>
1635                     <p>
1636                       Dynamic updates.
1637                     </p>
1638                   </td>
1639 </tr>
1640 <tr>
1641 <td>
1642                     <p><span><strong class="command">update-security</strong></span></p>
1643                   </td>
1644 <td>
1645                     <p>
1646                       Approval and denial of update requests.
1647                     </p>
1648                   </td>
1649 </tr>
1650 <tr>
1651 <td>
1652                     <p><span><strong class="command">queries</strong></span></p>
1653                   </td>
1654 <td>
1655                     <p>
1656                       Specify where queries should be logged to.
1657                     </p>
1658                     <p>
1659                       At startup, specifying the category <span><strong class="command">queries</strong></span> will also
1660                       enable query logging unless <span><strong class="command">querylog</strong></span> option has been
1661                       specified.
1662                     </p>
1663
1664                     <p>
1665                       The query log entry reports the client's IP
1666                       address and port number, and the query name,
1667                       class and type.  Next it reports whether the
1668                       Recursion Desired flag was set (+ if set, -
1669                       if not set), if the query was signed (S),
1670                       EDNS was in use (E), if TCP was used (T), if
1671                       DO (DNSSEC Ok) was set (D), or if CD (Checking
1672                       Disabled) was set (C).  After this the
1673                       destination address the query was sent to is
1674                       reported.
1675                     </p>
1676
1677                     <p>
1678                       <code class="computeroutput">client 127.0.0.1#62536 (www.example.com): query: www.example.com IN AAAA +SE</code>
1679                     </p>
1680                     <p>
1681                       <code class="computeroutput">client ::1#62537 (www.example.net): query: www.example.net IN AAAA -SE</code>
1682                     </p>
1683                     <p>
1684                       (The first part of this log message, showing the
1685                       client address/port number and query name, is
1686                       repeated in all subsequent log messages related
1687                       to the same query.)
1688                     </p>
1689                   </td>
1690 </tr>
1691 <tr>
1692 <td>
1693                     <p><span><strong class="command">query-errors</strong></span></p>
1694                   </td>
1695 <td>
1696                     <p>
1697                       Information about queries that resulted in some
1698                       failure.
1699                     </p>
1700                   </td>
1701 </tr>
1702 <tr>
1703 <td>
1704                     <p><span><strong class="command">dispatch</strong></span></p>
1705                   </td>
1706 <td>
1707                     <p>
1708                       Dispatching of incoming packets to the
1709                       server modules where they are to be processed.
1710                     </p>
1711                   </td>
1712 </tr>
1713 <tr>
1714 <td>
1715                     <p><span><strong class="command">dnssec</strong></span></p>
1716                   </td>
1717 <td>
1718                     <p>
1719                       DNSSEC and TSIG protocol processing.
1720                     </p>
1721                   </td>
1722 </tr>
1723 <tr>
1724 <td>
1725                     <p><span><strong class="command">lame-servers</strong></span></p>
1726                   </td>
1727 <td>
1728                     <p>
1729                       Lame servers.  These are misconfigurations
1730                       in remote servers, discovered by BIND 9 when trying to
1731                       query those servers during resolution.
1732                     </p>
1733                   </td>
1734 </tr>
1735 <tr>
1736 <td>
1737                     <p><span><strong class="command">delegation-only</strong></span></p>
1738                   </td>
1739 <td>
1740                     <p>
1741                       Delegation only.  Logs queries that have been
1742                       forced to NXDOMAIN as the result of a
1743                       delegation-only zone or a
1744                       <span><strong class="command">delegation-only</strong></span> in a
1745                       forward, hint or stub zone declaration.
1746                     </p>
1747                   </td>
1748 </tr>
1749 <tr>
1750 <td>
1751                     <p><span><strong class="command">edns-disabled</strong></span></p>
1752                   </td>
1753 <td>
1754                     <p>
1755                       Log queries that have been forced to use plain
1756                       DNS due to timeouts.  This is often due to
1757                       the remote servers not being RFC 1034 compliant
1758                       (not always returning FORMERR or similar to
1759                       EDNS queries and other extensions to the DNS
1760                       when they are not understood).  In other words, this is
1761                       targeted at servers that fail to respond to
1762                       DNS queries that they don't understand.
1763                     </p>
1764                     <p>
1765                       Note: the log message can also be due to
1766                       packet loss.  Before reporting servers for
1767                       non-RFC 1034 compliance they should be re-tested
1768                       to determine the nature of the non-compliance.
1769                       This testing should prevent or reduce the
1770                       number of false-positive reports.
1771                     </p>
1772                     <p>
1773                       Note: eventually <span><strong class="command">named</strong></span> will have to stop
1774                       treating such timeouts as due to RFC 1034 non
1775                       compliance and start treating it as plain
1776                       packet loss.  Falsely classifying packet
1777                       loss as due to RFC 1034 non compliance impacts
1778                       on DNSSEC validation which requires EDNS for
1779                       the DNSSEC records to be returned.
1780                     </p>
1781                   </td>
1782 </tr>
1783 <tr>
1784 <td>
1785                     <p><span><strong class="command">RPZ</strong></span></p>
1786                   </td>
1787 <td>
1788                     <p>
1789                       Information about errors in response policy zone files,
1790                       rewritten responses, and at the highest
1791                       <span><strong class="command">debug</strong></span> levels, mere rewriting
1792                       attempts.
1793                     </p>
1794                   </td>
1795 </tr>
1796 <tr>
1797 <td>
1798                     <p><span><strong class="command">rate-limit</strong></span></p>
1799                   </td>
1800 <td>
1801                     <p>
1802                       (Only available when <acronym class="acronym">BIND</acronym> 9 is
1803                       configured with the <strong class="userinput"><code>--enable-rrl</code></strong>
1804                       option at compile time.)
1805                     </p>
1806                     <p>
1807                       The start, periodic, and final notices of the
1808                       rate limiting of a stream of responses are logged at
1809                       <span><strong class="command">info</strong></span> severity in this category.
1810                       These messages include a hash value of the domain name
1811                       of the response and the name itself,
1812                       except when there is insufficient memory to record
1813                       the name for the final notice
1814                       The final notice is normally delayed until about one
1815                       minute after rate limit stops.
1816                       A lack of memory can hurry the final notice,
1817                       in which case it starts with an asterisk (*).
1818                       Various internal events are logged at debug 1 level
1819                       and higher.
1820                     </p>
1821                     <p>
1822                       Rate limiting of individual requests
1823                       is logged in the <span><strong class="command">query-errors</strong></span> category.
1824                     </p>
1825                   </td>
1826 </tr>
1827 </tbody>
1828 </table></div>
1829 </div>
1830 <div class="sect3" lang="en">
1831 <div class="titlepage"><div><div><h4 class="title">
1832 <a name="id2576491"></a>The <span><strong class="command">query-errors</strong></span> Category</h4></div></div></div>
1833 <p>
1834             The <span><strong class="command">query-errors</strong></span> category is
1835             specifically intended for debugging purposes: To identify
1836             why and how specific queries result in responses which
1837             indicate an error.
1838             Messages of this category are therefore only logged
1839             with <span><strong class="command">debug</strong></span> levels.
1840           </p>
1841 <p>
1842             At the debug levels of 1 or higher, each response with the
1843             rcode of SERVFAIL is logged as follows:
1844           </p>
1845 <p>
1846             <code class="computeroutput">client 127.0.0.1#61502: query failed (SERVFAIL) for www.example.com/IN/AAAA at query.c:3880</code>
1847           </p>
1848 <p>
1849             This means an error resulting in SERVFAIL was
1850             detected at line 3880 of source file
1851             <code class="filename">query.c</code>.
1852             Log messages of this level will particularly
1853             help identify the cause of SERVFAIL for an
1854             authoritative server.
1855           </p>
1856 <p>
1857             At the debug levels of 2 or higher, detailed context
1858             information of recursive resolutions that resulted in
1859             SERVFAIL is logged.
1860             The log message will look like as follows:
1861           </p>
1862 <p>
1863
1864             </p>
1865 <pre class="programlisting">
1866 fetch completed at resolver.c:2970 for www.example.com/A
1867 in 30.000183: timed out/success [domain:example.com,
1868 referral:2,restart:7,qrysent:8,timeout:5,lame:0,neterr:0,
1869 badresp:1,adberr:0,findfail:0,valfail:0]
1870             </pre>
1871 <p>
1872           </p>
1873 <p>
1874             The first part before the colon shows that a recursive
1875             resolution for AAAA records of www.example.com completed
1876             in 30.000183 seconds and the final result that led to the
1877             SERVFAIL was determined at line 2970 of source file
1878             <code class="filename">resolver.c</code>.
1879           </p>
1880 <p>
1881             The following part shows the detected final result and the
1882             latest result of DNSSEC validation.
1883             The latter is always success when no validation attempt
1884             is made.
1885             In this example, this query resulted in SERVFAIL probably
1886             because all name servers are down or unreachable, leading
1887             to a timeout in 30 seconds.
1888             DNSSEC validation was probably not attempted.
1889           </p>
1890 <p>
1891             The last part enclosed in square brackets shows statistics
1892             information collected for this particular resolution
1893             attempt.
1894             The <code class="varname">domain</code> field shows the deepest zone
1895             that the resolver reached;
1896             it is the zone where the error was finally detected.
1897             The meaning of the other fields is summarized in the
1898             following table.
1899           </p>
1900 <div class="informaltable"><table border="1">
1901 <colgroup>
1902 <col>
1903 <col>
1904 </colgroup>
1905 <tbody>
1906 <tr>
1907 <td>
1908                     <p><code class="varname">referral</code></p>
1909                   </td>
1910 <td>
1911                     <p>
1912                       The number of referrals the resolver received
1913                       throughout the resolution process.
1914                       In the above example this is 2, which are most
1915                       likely com and example.com.
1916                     </p>
1917                   </td>
1918 </tr>
1919 <tr>
1920 <td>
1921                     <p><code class="varname">restart</code></p>
1922                   </td>
1923 <td>
1924                     <p>
1925                       The number of cycles that the resolver tried
1926                       remote servers at the <code class="varname">domain</code>
1927                       zone.
1928                       In each cycle the resolver sends one query
1929                       (possibly resending it, depending on the response)
1930                       to each known name server of
1931                       the <code class="varname">domain</code> zone.
1932                     </p>
1933                   </td>
1934 </tr>
1935 <tr>
1936 <td>
1937                     <p><code class="varname">qrysent</code></p>
1938                   </td>
1939 <td>
1940                     <p>
1941                       The number of queries the resolver sent at the
1942                       <code class="varname">domain</code> zone.
1943                     </p>
1944                   </td>
1945 </tr>
1946 <tr>
1947 <td>
1948                     <p><code class="varname">timeout</code></p>
1949                   </td>
1950 <td>
1951                     <p>
1952                       The number of timeouts since the resolver
1953                       received the last response.
1954                     </p>
1955                   </td>
1956 </tr>
1957 <tr>
1958 <td>
1959                     <p><code class="varname">lame</code></p>
1960                   </td>
1961 <td>
1962                     <p>
1963                       The number of lame servers the resolver detected
1964                       at the <code class="varname">domain</code> zone.
1965                       A server is detected to be lame either by an
1966                       invalid response or as a result of lookup in
1967                       BIND9's address database (ADB), where lame
1968                       servers are cached.
1969                     </p>
1970                   </td>
1971 </tr>
1972 <tr>
1973 <td>
1974                     <p><code class="varname">neterr</code></p>
1975                   </td>
1976 <td>
1977                     <p>
1978                       The number of erroneous results that the
1979                       resolver encountered in sending queries
1980                       at the <code class="varname">domain</code> zone.
1981                       One common case is the remote server is
1982                       unreachable and the resolver receives an ICMP
1983                       unreachable error message.
1984                     </p>
1985                   </td>
1986 </tr>
1987 <tr>
1988 <td>
1989                     <p><code class="varname">badresp</code></p>
1990                   </td>
1991 <td>
1992                     <p>
1993                       The number of unexpected responses (other than
1994                       <code class="varname">lame</code>) to queries sent by the
1995                       resolver at the <code class="varname">domain</code> zone.
1996                     </p>
1997                   </td>
1998 </tr>
1999 <tr>
2000 <td>
2001                     <p><code class="varname">adberr</code></p>
2002                   </td>
2003 <td>
2004                     <p>
2005                       Failures in finding remote server addresses
2006                       of the <code class="varname">domain</code> zone in the ADB.
2007                       One common case of this is that the remote
2008                       server's name does not have any address records.
2009                     </p>
2010                   </td>
2011 </tr>
2012 <tr>
2013 <td>
2014                     <p><code class="varname">findfail</code></p>
2015                   </td>
2016 <td>
2017                     <p>
2018                       Failures of resolving remote server addresses.
2019                       This is a total number of failures throughout
2020                       the resolution process.
2021                     </p>
2022                   </td>
2023 </tr>
2024 <tr>
2025 <td>
2026                     <p><code class="varname">valfail</code></p>
2027                   </td>
2028 <td>
2029                     <p>
2030                       Failures of DNSSEC validation.
2031                       Validation failures are counted throughout
2032                       the resolution process (not limited to
2033                       the <code class="varname">domain</code> zone), but should
2034                       only happen in <code class="varname">domain</code>.
2035                     </p>
2036                   </td>
2037 </tr>
2038 </tbody>
2039 </table></div>
2040 <p>
2041             At the debug levels of 3 or higher, the same messages
2042             as those at the debug 1 level are logged for other errors
2043             than SERVFAIL.
2044             Note that negative responses such as NXDOMAIN are not
2045             regarded as errors here.
2046           </p>
2047 <p>
2048             At the debug levels of 4 or higher, the same messages
2049             as those at the debug 2 level are logged for other errors
2050             than SERVFAIL.
2051             Unlike the above case of level 3, messages are logged for
2052             negative responses.
2053             This is because any unexpected results can be difficult to
2054             debug in the recursion case.
2055           </p>
2056 </div>
2057 </div>
2058 <div class="sect2" lang="en">
2059 <div class="titlepage"><div><div><h3 class="title">
2060 <a name="id2577079"></a><span><strong class="command">lwres</strong></span> Statement Grammar</h3></div></div></div>
2061 <p>
2062            This is the grammar of the <span><strong class="command">lwres</strong></span>
2063           statement in the <code class="filename">named.conf</code> file:
2064         </p>
2065 <pre class="programlisting"><span><strong class="command">lwres</strong></span> {
2066     [<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>] ;
2067                 [<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>]
2068     [<span class="optional"> view <em class="replaceable"><code>view_name</code></em>; </span>]
2069     [<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>]
2070     [<span class="optional"> ndots <em class="replaceable"><code>number</code></em>; </span>]
2071 };
2072 </pre>
2073 </div>
2074 <div class="sect2" lang="en">
2075 <div class="titlepage"><div><div><h3 class="title">
2076 <a name="id2577153"></a><span><strong class="command">lwres</strong></span> Statement Definition and Usage</h3></div></div></div>
2077 <p>
2078           The <span><strong class="command">lwres</strong></span> statement configures the
2079           name
2080           server to also act as a lightweight resolver server. (See
2081           <a href="Bv9ARM.ch05.html#lwresd" title="Running a Resolver Daemon">the section called &#8220;Running a Resolver Daemon&#8221;</a>.)  There may be multiple
2082           <span><strong class="command">lwres</strong></span> statements configuring
2083           lightweight resolver servers with different properties.
2084         </p>
2085 <p>
2086           The <span><strong class="command">listen-on</strong></span> statement specifies a
2087           list of
2088           IPv4 addresses (and ports) that this instance of a lightweight
2089           resolver daemon
2090           should accept requests on.  If no port is specified, port 921 is
2091           used.
2092           If this statement is omitted, requests will be accepted on
2093           127.0.0.1,
2094           port 921.
2095         </p>
2096 <p>
2097           The <span><strong class="command">view</strong></span> statement binds this
2098           instance of a
2099           lightweight resolver daemon to a view in the DNS namespace, so that
2100           the
2101           response will be constructed in the same manner as a normal DNS
2102           query
2103           matching this view.  If this statement is omitted, the default view
2104           is
2105           used, and if there is no default view, an error is triggered.
2106         </p>
2107 <p>
2108           The <span><strong class="command">search</strong></span> statement is equivalent to
2109           the
2110           <span><strong class="command">search</strong></span> statement in
2111           <code class="filename">/etc/resolv.conf</code>.  It provides a
2112           list of domains
2113           which are appended to relative names in queries.
2114         </p>
2115 <p>
2116           The <span><strong class="command">ndots</strong></span> statement is equivalent to
2117           the
2118           <span><strong class="command">ndots</strong></span> statement in
2119           <code class="filename">/etc/resolv.conf</code>.  It indicates the
2120           minimum
2121           number of dots in a relative domain name that should result in an
2122           exact match lookup before search path elements are appended.
2123         </p>
2124 </div>
2125 <div class="sect2" lang="en">
2126 <div class="titlepage"><div><div><h3 class="title">
2127 <a name="id2577285"></a><span><strong class="command">masters</strong></span> Statement Grammar</h3></div></div></div>
2128 <pre class="programlisting">
2129 <span><strong class="command">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> |
2130       <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>] };
2131 </pre>
2132 </div>
2133 <div class="sect2" lang="en">
2134 <div class="titlepage"><div><div><h3 class="title">
2135 <a name="id2577329"></a><span><strong class="command">masters</strong></span> Statement Definition and
2136           Usage</h3></div></div></div>
2137 <p><span><strong class="command">masters</strong></span>
2138           lists allow for a common set of masters to be easily used by
2139           multiple stub and slave zones in their <span><strong class="command">masters</strong></span>
2140           or <span><strong class="command">also-notify</strong></span> lists.
2141         </p>
2142 </div>
2143 <div class="sect2" lang="en">
2144 <div class="titlepage"><div><div><h3 class="title">
2145 <a name="id2577350"></a><span><strong class="command">options</strong></span> Statement Grammar</h3></div></div></div>
2146 <p>
2147           This is the grammar of the <span><strong class="command">options</strong></span>
2148           statement in the <code class="filename">named.conf</code> file:
2149         </p>
2150 <pre class="programlisting"><span><strong class="command">options</strong></span> {
2151     [<span class="optional"> attach-cache <em class="replaceable"><code>cache_name</code></em>; </span>]
2152     [<span class="optional"> version <em class="replaceable"><code>version_string</code></em>; </span>]
2153     [<span class="optional"> hostname <em class="replaceable"><code>hostname_string</code></em>; </span>]
2154     [<span class="optional"> server-id <em class="replaceable"><code>server_id_string</code></em>; </span>]
2155     [<span class="optional"> directory <em class="replaceable"><code>path_name</code></em>; </span>]
2156     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2157     [<span class="optional"> managed-keys-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2158     [<span class="optional"> named-xfer <em class="replaceable"><code>path_name</code></em>; </span>]
2159     [<span class="optional"> tkey-gssapi-keytab <em class="replaceable"><code>path_name</code></em>; </span>]
2160     [<span class="optional"> tkey-gssapi-credential <em class="replaceable"><code>principal</code></em>; </span>]
2161     [<span class="optional"> tkey-domain <em class="replaceable"><code>domainname</code></em>; </span>]
2162     [<span class="optional"> tkey-dhkey <em class="replaceable"><code>key_name</code></em> <em class="replaceable"><code>key_tag</code></em>; </span>]
2163     [<span class="optional"> cache-file <em class="replaceable"><code>path_name</code></em>; </span>]
2164     [<span class="optional"> dump-file <em class="replaceable"><code>path_name</code></em>; </span>]
2165     [<span class="optional"> bindkeys-file <em class="replaceable"><code>path_name</code></em>; </span>]
2166     [<span class="optional"> secroots-file <em class="replaceable"><code>path_name</code></em>; </span>]
2167     [<span class="optional"> session-keyfile <em class="replaceable"><code>path_name</code></em>; </span>]
2168     [<span class="optional"> session-keyname <em class="replaceable"><code>key_name</code></em>; </span>]
2169     [<span class="optional"> session-keyalg <em class="replaceable"><code>algorithm_id</code></em>; </span>]
2170     [<span class="optional"> memstatistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2171     [<span class="optional"> memstatistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2172     [<span class="optional"> pid-file <em class="replaceable"><code>path_name</code></em>; </span>]
2173     [<span class="optional"> recursing-file <em class="replaceable"><code>path_name</code></em>; </span>]
2174     [<span class="optional"> statistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2175     [<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>]
2176     [<span class="optional"> auth-nxdomain <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2177     [<span class="optional"> deallocate-on-exit <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2178     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em>; </span>]
2179     [<span class="optional"> fake-iquery <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2180     [<span class="optional"> fetch-glue <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2181     [<span class="optional"> flush-zones-on-shutdown <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2182     [<span class="optional"> has-old-clients <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2183     [<span class="optional"> host-statistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2184     [<span class="optional"> host-statistics-max <em class="replaceable"><code>number</code></em>; </span>]
2185     [<span class="optional"> minimal-responses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2186     [<span class="optional"> multiple-cnames <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2187     [<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>]
2188     [<span class="optional"> recursion <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2189     [<span class="optional"> request-nsid <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2190     [<span class="optional"> rfc2308-type1 <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2191     [<span class="optional"> use-id-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2192     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2193     [<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>]
2194     [<span class="optional"> dnssec-enable <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2195     [<span class="optional"> dnssec-validation (<em class="replaceable"><code>yes_or_no</code></em> | <code class="constant">auto</code>); </span>]
2196     [<span class="optional"> dnssec-lookaside ( <em class="replaceable"><code>auto</code></em> |
2197                         <em class="replaceable"><code>no</code></em> |
2198                         <em class="replaceable"><code>domain</code></em> trust-anchor <em class="replaceable"><code>domain</code></em> ); </span>]
2199     [<span class="optional"> dnssec-must-be-secure <em class="replaceable"><code>domain yes_or_no</code></em>; </span>]
2200     [<span class="optional"> dnssec-accept-expired <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2201     [<span class="optional"> forward ( <em class="replaceable"><code>only</code></em> | <em class="replaceable"><code>first</code></em> ); </span>]
2202     [<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>]
2203     [<span class="optional"> dual-stack-servers [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] {
2204         ( <em class="replaceable"><code>domain_name</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] |
2205           <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ) ;
2206         ... }; </span>]
2207     [<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> )
2208         ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2209     [<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>]
2210     [<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>]
2211     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2212     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2213     [<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>]
2214     [<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>]
2215     [<span class="optional"> check-sibling <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2216     [<span class="optional"> check-spf ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2217     [<span class="optional"> allow-new-zones { <em class="replaceable"><code>yes_or_no</code></em> }; </span>]
2218     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2219     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2220     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2221     [<span class="optional"> allow-query-cache { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2222     [<span class="optional"> allow-query-cache-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2223     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2224     [<span class="optional"> allow-recursion { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2225     [<span class="optional"> allow-recursion-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2226     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2227     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2228     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2229     [<span class="optional"> dnssec-update-mode ( <em class="replaceable"><code>maintain</code></em> | <em class="replaceable"><code>no-resign</code></em> ); </span>]
2230     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2231     [<span class="optional"> dnssec-loadkeys-interval <em class="replaceable"><code>number</code></em>; </span>]
2232     [<span class="optional"> dnssec-secure-to-insecure <em class="replaceable"><code>yes_or_no</code></em> ;</span>]
2233     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2234     [<span class="optional"> allow-v6-synthesis { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2235     [<span class="optional"> blackhole { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2236     [<span class="optional"> no-case-compress { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2237     [<span class="optional"> use-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2238     [<span class="optional"> avoid-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2239     [<span class="optional"> use-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2240     [<span class="optional"> avoid-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2241     [<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>]
2242     [<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>]
2243     [<span class="optional"> query-source ( ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2244         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
2245         [<span class="optional"> address ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2246         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
2247     [<span class="optional"> query-source-v6 ( ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2248         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
2249         [<span class="optional"> address ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2250         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
2251     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2252     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
2253     [<span class="optional"> queryport-pool-updateinterval <em class="replaceable"><code>number</code></em>; </span>]
2254     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em>; </span>]
2255     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em>; </span>]
2256     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em>; </span>]
2257     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em>; </span>]
2258     [<span class="optional"> tcp-clients <em class="replaceable"><code>number</code></em>; </span>]
2259     [<span class="optional"> reserved-sockets <em class="replaceable"><code>number</code></em>; </span>]
2260     [<span class="optional"> recursive-clients <em class="replaceable"><code>number</code></em>; </span>]
2261     [<span class="optional"> serial-query-rate <em class="replaceable"><code>number</code></em>; </span>]
2262     [<span class="optional"> serial-queries <em class="replaceable"><code>number</code></em>; </span>]
2263     [<span class="optional"> tcp-listen-queue <em class="replaceable"><code>number</code></em>; </span>]
2264     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em>; </span>]
2265     [<span class="optional"> transfers-in  <em class="replaceable"><code>number</code></em>; </span>]
2266     [<span class="optional"> transfers-out <em class="replaceable"><code>number</code></em>; </span>]
2267     [<span class="optional"> transfers-per-ns <em class="replaceable"><code>number</code></em>; </span>]
2268     [<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>]
2269     [<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>]
2270     [<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>]
2271     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
2272                              [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
2273     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2274     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
2275     [<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>]
2276     [<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>]
2277     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2278     [<span class="optional"> also-notify { <em class="replaceable"><code>ip_addr</code></em>
2279                     [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] [<span class="optional">key <em class="replaceable"><code>keyname</code></em></span>] ;
2280                     [<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 class="optional">key <em class="replaceable"><code>keyname</code></em></span>] ; ... </span>] }; </span>]
2281     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em>; </span>]
2282     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
2283     [<span class="optional"> coresize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2284     [<span class="optional"> datasize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2285     [<span class="optional"> files <em class="replaceable"><code>size_spec</code></em> ; </span>]
2286     [<span class="optional"> stacksize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2287     [<span class="optional"> cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2288     [<span class="optional"> heartbeat-interval <em class="replaceable"><code>number</code></em>; </span>]
2289     [<span class="optional"> interface-interval <em class="replaceable"><code>number</code></em>; </span>]
2290     [<span class="optional"> statistics-interval <em class="replaceable"><code>number</code></em>; </span>]
2291     [<span class="optional"> topology { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2292     [<span class="optional"> sortlist { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2293     [<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>] };
2294     [<span class="optional"> lame-ttl <em class="replaceable"><code>number</code></em>; </span>]
2295     [<span class="optional"> max-ncache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2296     [<span class="optional"> max-cache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2297     [<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>]
2298     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
2299     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
2300     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
2301     [<span class="optional"> min-roots <em class="replaceable"><code>number</code></em>; </span>]
2302     [<span class="optional"> use-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2303     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2304     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2305     [<span class="optional"> treat-cr-as-space <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2306     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2307     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2308     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2309     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2310     [<span class="optional"> port <em class="replaceable"><code>ip_port</code></em>; </span>]
2311     [<span class="optional"> additional-from-auth <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2312     [<span class="optional"> additional-from-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2313     [<span class="optional"> random-device <em class="replaceable"><code>path_name</code></em> ; </span>]
2314     [<span class="optional"> max-cache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2315     [<span class="optional"> match-mapped-addresses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2316     [<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>]
2317     [<span class="optional"> filter-aaaa { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2318     [<span class="optional"> dns64 <em class="replaceable"><code>ipv6-prefix</code></em> {
2319         [<span class="optional"> clients { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2320         [<span class="optional"> mapped { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2321         [<span class="optional"> exclude { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2322         [<span class="optional"> suffix IPv6-address; </span>]
2323         [<span class="optional"> recursive-only <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2324         [<span class="optional"> break-dnssec <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2325     }; </span>];
2326     [<span class="optional"> dns64-server <em class="replaceable"><code>name</code></em> </span>]
2327     [<span class="optional"> dns64-contact <em class="replaceable"><code>name</code></em> </span>]
2328     [<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>]
2329     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2330     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2331     [<span class="optional"> max-rsa-exponent-size <em class="replaceable"><code>number</code></em>; </span>]
2332     [<span class="optional"> root-delegation-only [<span class="optional"> exclude { <em class="replaceable"><code>namelist</code></em> } </span>] ; </span>]
2333     [<span class="optional"> querylog <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2334     [<span class="optional"> disable-algorithms <em class="replaceable"><code>domain</code></em> { <em class="replaceable"><code>algorithm</code></em>;
2335                                 [<span class="optional"> <em class="replaceable"><code>algorithm</code></em>; </span>] }; </span>]
2336     [<span class="optional"> acache-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2337     [<span class="optional"> acache-cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2338     [<span class="optional"> max-acache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2339     [<span class="optional"> clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2340     [<span class="optional"> max-clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2341     [<span class="optional"> max-recursion-depth <em class="replaceable"><code>number</code></em> ; </span>]
2342     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
2343     [<span class="optional"> empty-server <em class="replaceable"><code>name</code></em> ; </span>]
2344     [<span class="optional"> empty-contact <em class="replaceable"><code>name</code></em> ; </span>]
2345     [<span class="optional"> empty-zones-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2346     [<span class="optional"> disable-empty-zone <em class="replaceable"><code>zone_name</code></em> ; </span>]
2347     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2348     [<span class="optional"> zero-no-soa-ttl-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2349     [<span class="optional"> resolver-query-timeout <em class="replaceable"><code>number</code></em> ; </span>]
2350     [<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>]
2351     [<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>]
2352     [<span class="optional"> rate-limit {
2353         [<span class="optional"> responses-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2354         [<span class="optional"> referrals-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2355         [<span class="optional"> nodata-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2356         [<span class="optional"> nxdomains-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2357         [<span class="optional"> errors-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2358         [<span class="optional"> all-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2359         [<span class="optional"> window <em class="replaceable"><code>number</code></em> ; </span>]
2360         [<span class="optional"> log-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2361         [<span class="optional"> qps-scale <em class="replaceable"><code>number</code></em> ; </span>]
2362         [<span class="optional"> ipv4-prefix-length <em class="replaceable"><code>number</code></em> ; </span>]
2363         [<span class="optional"> ipv6-prefix-length <em class="replaceable"><code>number</code></em> ; </span>]
2364         [<span class="optional"> slip <em class="replaceable"><code>number</code></em> ; </span>]
2365         [<span class="optional"> exempt-clients  { <em class="replaceable"><code>address_match_list</code></em> } ; </span>]
2366         [<span class="optional"> max-table-size <em class="replaceable"><code>number</code></em> ; </span>]
2367         [<span class="optional"> min-table-size <em class="replaceable"><code>number</code></em> ; </span>]
2368       } ; </span>]
2369     [<span class="optional"> response-policy { <em class="replaceable"><code>zone_name</code></em>
2370         [<span class="optional"> policy given | disabled | passthru | nxdomain | nodata | cname <em class="replaceable"><code>domain</code></em> </span>]
2371         [<span class="optional"> recursive-only <em class="replaceable"><code>yes_or_no</code></em> </span>] [<span class="optional"> max-policy-ttl <em class="replaceable"><code>number</code></em> </span>] ;
2372     } [<span class="optional"> recursive-only <em class="replaceable"><code>yes_or_no</code></em> </span>] [<span class="optional"> max-policy-ttl <em class="replaceable"><code>number</code></em> </span>]
2373         [<span class="optional"> break-dnssec <em class="replaceable"><code>yes_or_no</code></em> </span>] [<span class="optional"> min-ns-dots <em class="replaceable"><code>number</code></em> </span>] ; </span>]
2374 };
2375 </pre>
2376 </div>
2377 <div class="sect2" lang="en">
2378 <div class="titlepage"><div><div><h3 class="title">
2379 <a name="options"></a><span><strong class="command">options</strong></span> Statement Definition and
2380           Usage</h3></div></div></div>
2381 <p>
2382           The <span><strong class="command">options</strong></span> statement sets up global
2383           options
2384           to be used by <acronym class="acronym">BIND</acronym>. This statement
2385           may appear only
2386           once in a configuration file. If there is no <span><strong class="command">options</strong></span>
2387           statement, an options block with each option set to its default will
2388           be used.
2389         </p>
2390 <div class="variablelist"><dl>
2391 <dt><span class="term"><span><strong class="command">attach-cache</strong></span></span></dt>
2392 <dd>
2393 <p>
2394                   Allows multiple views to share a single cache
2395                   database.
2396                   Each view has its own cache database by default, but
2397                   if multiple views have the same operational policy
2398                   for name resolution and caching, those views can
2399                   share a single cache to save memory and possibly
2400                   improve resolution efficiency by using this option.
2401                 </p>
2402 <p>
2403                   The <span><strong class="command">attach-cache</strong></span> option
2404                   may also be specified in <span><strong class="command">view</strong></span>
2405                   statements, in which case it overrides the
2406                   global <span><strong class="command">attach-cache</strong></span> option.
2407                 </p>
2408 <p>
2409                   The <em class="replaceable"><code>cache_name</code></em> specifies
2410                   the cache to be shared.
2411                   When the <span><strong class="command">named</strong></span> server configures
2412                   views which are supposed to share a cache, it
2413                   creates a cache with the specified name for the
2414                   first view of these sharing views.
2415                   The rest of the views will simply refer to the
2416                   already created cache.
2417                 </p>
2418 <p>
2419                   One common configuration to share a cache would be to
2420                   allow all views to share a single cache.
2421                   This can be done by specifying
2422                   the <span><strong class="command">attach-cache</strong></span> as a global
2423                   option with an arbitrary name.
2424                 </p>
2425 <p>
2426                   Another possible operation is to allow a subset of
2427                   all views to share a cache while the others to
2428                   retain their own caches.
2429                   For example, if there are three views A, B, and C,
2430                   and only A and B should share a cache, specify the
2431                   <span><strong class="command">attach-cache</strong></span> option as a view A (or
2432                   B)'s option, referring to the other view name:
2433                 </p>
2434 <pre class="programlisting">
2435   view "A" {
2436     // this view has its own cache
2437     ...
2438   };
2439   view "B" {
2440     // this view refers to A's cache
2441     attach-cache "A";
2442   };
2443   view "C" {
2444     // this view has its own cache
2445     ...
2446   };
2447 </pre>
2448 <p>
2449                   Views that share a cache must have the same policy
2450                   on configurable parameters that may affect caching.
2451                   The current implementation requires the following
2452                   configurable options be consistent among these
2453                   views:
2454                   <span><strong class="command">check-names</strong></span>,
2455                   <span><strong class="command">cleaning-interval</strong></span>,
2456                   <span><strong class="command">dnssec-accept-expired</strong></span>,
2457                   <span><strong class="command">dnssec-validation</strong></span>,
2458                   <span><strong class="command">max-cache-ttl</strong></span>,
2459                   <span><strong class="command">max-ncache-ttl</strong></span>,
2460                   <span><strong class="command">max-cache-size</strong></span>, and
2461                   <span><strong class="command">zero-no-soa-ttl</strong></span>.
2462                 </p>
2463 <p>
2464                   Note that there may be other parameters that may
2465                   cause confusion if they are inconsistent for
2466                   different views that share a single cache.
2467                   For example, if these views define different sets of
2468                   forwarders that can return different answers for the
2469                   same question, sharing the answer does not make
2470                   sense or could even be harmful.
2471                   It is administrator's responsibility to ensure
2472                   configuration differences in different views do
2473                   not cause disruption with a shared cache.
2474                 </p>
2475 </dd>
2476 <dt><span class="term"><span><strong class="command">directory</strong></span></span></dt>
2477 <dd><p>
2478                 The working directory of the server.
2479                 Any non-absolute pathnames in the configuration file will be
2480                 taken
2481                 as relative to this directory. The default location for most
2482                 server
2483                 output files (e.g. <code class="filename">named.run</code>)
2484                 is this directory.
2485                 If a directory is not specified, the working directory
2486                 defaults to `<code class="filename">.</code>', the directory from
2487                 which the server
2488                 was started. The directory specified should be an absolute
2489                 path.
2490               </p></dd>
2491 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
2492 <dd><p>
2493                 When performing dynamic update of secure zones, the
2494                 directory where the public and private DNSSEC key files
2495                 should be found, if different than the current working
2496                 directory.  (Note that this option has no effect on the
2497                 paths for files containing non-DNSSEC keys such as
2498                 <code class="filename">bind.keys</code>,
2499                 <code class="filename">rndc.key</code> or
2500                 <code class="filename">session.key</code>.)
2501               </p></dd>
2502 <dt><span class="term"><span><strong class="command">managed-keys-directory</strong></span></span></dt>
2503 <dd>
2504 <p>
2505                 Specifies the directory in which to store the files that
2506                 track managed DNSSEC keys.  By default, this is the working
2507                 directory.
2508               </p>
2509 <p>
2510                 If <span><strong class="command">named</strong></span> is not configured to use views,
2511                 then managed keys for the server will be tracked in a single
2512                 file called <code class="filename">managed-keys.bind</code>.
2513                 Otherwise, managed keys will be tracked in separate files,
2514                 one file per view; each file name will be the SHA256 hash
2515                 of the view name, followed by the extension
2516                 <code class="filename">.mkeys</code>.
2517               </p>
2518 </dd>
2519 <dt><span class="term"><span><strong class="command">named-xfer</strong></span></span></dt>
2520 <dd><p>
2521                 <span class="emphasis"><em>This option is obsolete.</em></span> It
2522                 was used in <acronym class="acronym">BIND</acronym> 8 to specify
2523                 the pathname to the <span><strong class="command">named-xfer</strong></span>
2524                 program.  In <acronym class="acronym">BIND</acronym> 9, no separate
2525                 <span><strong class="command">named-xfer</strong></span> program is needed;
2526                 its functionality is built into the name server.
2527               </p></dd>
2528 <dt><span class="term"><span><strong class="command">tkey-gssapi-keytab</strong></span></span></dt>
2529 <dd><p>
2530                 The KRB5 keytab file to use for GSS-TSIG updates. If
2531                 this option is set and tkey-gssapi-credential is not
2532                 set, then updates will be allowed with any key
2533                 matching a principal in the specified keytab.
2534               </p></dd>
2535 <dt><span class="term"><span><strong class="command">tkey-gssapi-credential</strong></span></span></dt>
2536 <dd><p>
2537                 The security credential with which the server should
2538                 authenticate keys requested by the GSS-TSIG protocol.
2539                 Currently only Kerberos 5 authentication is available
2540                 and the credential is a Kerberos principal which the
2541                 server can acquire through the default system key
2542                 file, normally <code class="filename">/etc/krb5.keytab</code>.
2543                 The location keytab file can be overridden using the
2544                 tkey-gssapi-keytab option. Normally this principal is
2545                 of the form "<strong class="userinput"><code>DNS/</code></strong><code class="varname">server.domain</code>".
2546                 To use GSS-TSIG, <span><strong class="command">tkey-domain</strong></span> must
2547                 also be set if a specific keytab is not set with
2548                 tkey-gssapi-keytab.
2549               </p></dd>
2550 <dt><span class="term"><span><strong class="command">tkey-domain</strong></span></span></dt>
2551 <dd><p>
2552                 The domain appended to the names of all shared keys
2553                 generated with <span><strong class="command">TKEY</strong></span>.  When a
2554                 client requests a <span><strong class="command">TKEY</strong></span> exchange,
2555                 it may or may not specify the desired name for the
2556                 key. If present, the name of the shared key will
2557                 be <code class="varname">client specified part</code> +
2558                 <code class="varname">tkey-domain</code>.  Otherwise, the
2559                 name of the shared key will be <code class="varname">random hex
2560                 digits</code> + <code class="varname">tkey-domain</code>.
2561                 In most cases, the <span><strong class="command">domainname</strong></span>
2562                 should be the server's domain name, or an otherwise
2563                 non-existent subdomain like
2564                 "_tkey.<code class="varname">domainname</code>".  If you are
2565                 using GSS-TSIG, this variable must be defined, unless
2566                 you specify a specific keytab using tkey-gssapi-keytab.
2567               </p></dd>
2568 <dt><span class="term"><span><strong class="command">tkey-dhkey</strong></span></span></dt>
2569 <dd><p>
2570                 The Diffie-Hellman key used by the server
2571                 to generate shared keys with clients using the Diffie-Hellman
2572                 mode
2573                 of <span><strong class="command">TKEY</strong></span>. The server must be
2574                 able to load the
2575                 public and private keys from files in the working directory.
2576                 In
2577                 most cases, the keyname should be the server's host name.
2578               </p></dd>
2579 <dt><span class="term"><span><strong class="command">cache-file</strong></span></span></dt>
2580 <dd><p>
2581                 This is for testing only.  Do not use.
2582               </p></dd>
2583 <dt><span class="term"><span><strong class="command">dump-file</strong></span></span></dt>
2584 <dd><p>
2585                 The pathname of the file the server dumps
2586                 the database to when instructed to do so with
2587                 <span><strong class="command">rndc dumpdb</strong></span>.
2588                 If not specified, the default is <code class="filename">named_dump.db</code>.
2589               </p></dd>
2590 <dt><span class="term"><span><strong class="command">memstatistics-file</strong></span></span></dt>
2591 <dd><p>
2592                 The pathname of the file the server writes memory
2593                 usage statistics to on exit. If not specified,
2594                 the default is <code class="filename">named.memstats</code>.
2595               </p></dd>
2596 <dt><span class="term"><span><strong class="command">pid-file</strong></span></span></dt>
2597 <dd><p>
2598                 The pathname of the file the server writes its process ID
2599                 in. If not specified, the default is
2600                 <code class="filename">/var/run/named/named.pid</code>.
2601                 The PID file is used by programs that want to send signals to
2602                 the running
2603                 name server. Specifying <span><strong class="command">pid-file none</strong></span> disables the
2604                 use of a PID file &#8212; no file will be written and any
2605                 existing one will be removed.  Note that <span><strong class="command">none</strong></span>
2606                 is a keyword, not a filename, and therefore is not enclosed
2607                 in
2608                 double quotes.
2609               </p></dd>
2610 <dt><span class="term"><span><strong class="command">recursing-file</strong></span></span></dt>
2611 <dd><p>
2612                 The pathname of the file the server dumps
2613                 the queries that are currently recursing when instructed
2614                 to do so with <span><strong class="command">rndc recursing</strong></span>.
2615                 If not specified, the default is <code class="filename">named.recursing</code>.
2616               </p></dd>
2617 <dt><span class="term"><span><strong class="command">statistics-file</strong></span></span></dt>
2618 <dd><p>
2619                 The pathname of the file the server appends statistics
2620                 to when instructed to do so using <span><strong class="command">rndc stats</strong></span>.
2621                 If not specified, the default is <code class="filename">named.stats</code> in the
2622                 server's current directory.  The format of the file is
2623                 described
2624                 in <a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
2625               </p></dd>
2626 <dt><span class="term"><span><strong class="command">bindkeys-file</strong></span></span></dt>
2627 <dd><p>
2628                 The pathname of a file to override the built-in trusted
2629                 keys provided by <span><strong class="command">named</strong></span>.
2630                 See the discussion of <span><strong class="command">dnssec-lookaside</strong></span>
2631                 and <span><strong class="command">dnssec-validation</strong></span> for details.
2632                 If not specified, the default is
2633                 <code class="filename">/etc/bind.keys</code>.
2634               </p></dd>
2635 <dt><span class="term"><span><strong class="command">secroots-file</strong></span></span></dt>
2636 <dd><p>
2637                 The pathname of the file the server dumps
2638                 security roots to when instructed to do so with
2639                 <span><strong class="command">rndc secroots</strong></span>.
2640                 If not specified, the default is
2641                 <code class="filename">named.secroots</code>.
2642               </p></dd>
2643 <dt><span class="term"><span><strong class="command">session-keyfile</strong></span></span></dt>
2644 <dd><p>
2645                 The pathname of the file into which to write a TSIG
2646                 session key generated by <span><strong class="command">named</strong></span> for use by
2647                 <span><strong class="command">nsupdate -l</strong></span>.  If not specified, the
2648                 default is <code class="filename">/var/run/named/session.key</code>.
2649                 (See <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>, and in
2650                 particular the discussion of the
2651                 <span><strong class="command">update-policy</strong></span> statement's
2652                 <strong class="userinput"><code>local</code></strong> option for more
2653                 information about this feature.)
2654               </p></dd>
2655 <dt><span class="term"><span><strong class="command">session-keyname</strong></span></span></dt>
2656 <dd><p>
2657                 The key name to use for the TSIG session key.
2658                 If not specified, the default is "local-ddns".
2659               </p></dd>
2660 <dt><span class="term"><span><strong class="command">session-keyalg</strong></span></span></dt>
2661 <dd><p>
2662                 The algorithm to use for the TSIG session key.
2663                 Valid values are hmac-sha1, hmac-sha224, hmac-sha256,
2664                 hmac-sha384, hmac-sha512 and hmac-md5.  If not
2665                 specified, the default is hmac-sha256.
2666               </p></dd>
2667 <dt><span class="term"><span><strong class="command">port</strong></span></span></dt>
2668 <dd><p>
2669                 The UDP/TCP port number the server uses for
2670                 receiving and sending DNS protocol traffic.
2671                 The default is 53.  This option is mainly intended for server
2672                 testing;
2673                 a server using a port other than 53 will not be able to
2674                 communicate with
2675                 the global DNS.
2676               </p></dd>
2677 <dt><span class="term"><span><strong class="command">random-device</strong></span></span></dt>
2678 <dd><p>
2679                 The source of entropy to be used by the server.  Entropy is
2680                 primarily needed
2681                 for DNSSEC operations, such as TKEY transactions and dynamic
2682                 update of signed
2683                 zones.  This options specifies the device (or file) from which
2684                 to read
2685                 entropy.  If this is a file, operations requiring entropy will
2686                 fail when the
2687                 file has been exhausted.  If not specified, the default value
2688                 is
2689                 <code class="filename">/dev/random</code>
2690                 (or equivalent) when present, and none otherwise.  The
2691                 <span><strong class="command">random-device</strong></span> option takes
2692                 effect during
2693                 the initial configuration load at server startup time and
2694                 is ignored on subsequent reloads.
2695               </p></dd>
2696 <dt><span class="term"><span><strong class="command">preferred-glue</strong></span></span></dt>
2697 <dd><p>
2698                 If specified, the listed type (A or AAAA) will be emitted
2699                 before other glue
2700                 in the additional section of a query response.
2701                 The default is not to prefer any type (NONE).
2702               </p></dd>
2703 <dt>
2704 <a name="root_delegation_only"></a><span class="term"><span><strong class="command">root-delegation-only</strong></span></span>
2705 </dt>
2706 <dd>
2707 <p>
2708                 Turn on enforcement of delegation-only in TLDs
2709                 (top level domains) and root zones with an optional
2710                 exclude list.
2711               </p>
2712 <p>
2713                 DS queries are expected to be made to and be answered by
2714                 delegation only zones.  Such queries and responses are
2715                 treated as an exception to delegation-only processing
2716                 and are not converted to NXDOMAIN responses provided
2717                 a CNAME is not discovered at the query name.
2718               </p>
2719 <p>
2720                 If a delegation only zone server also serves a child
2721                 zone it is not always possible to determine whether
2722                 an answer comes from the delegation only zone or the
2723                 child zone.  SOA NS and DNSKEY records are apex
2724                 only records and a matching response that contains
2725                 these records or DS is treated as coming from a
2726                 child zone.  RRSIG records are also examined to see
2727                 if they are signed by a child zone or not.  The
2728                 authority section is also examined to see if there
2729                 is evidence that the answer is from the child zone.
2730                 Answers that are determined to be from a child zone
2731                 are not converted to NXDOMAIN responses.  Despite
2732                 all these checks there is still a possibility of
2733                 false negatives when a child zone is being served.
2734               </p>
2735 <p>
2736                 Similarly false positives can arise from empty nodes
2737                 (no records at the name) in the delegation only zone
2738                 when the query type is not ANY.
2739               </p>
2740 <p>
2741                 Note some TLDs are not delegation only (e.g. "DE", "LV",
2742                 "US" and "MUSEUM").  This list is not exhaustive.
2743               </p>
2744 <pre class="programlisting">
2745 options {
2746         root-delegation-only exclude { "de"; "lv"; "us"; "museum"; };
2747 };
2748 </pre>
2749 </dd>
2750 <dt><span class="term"><span><strong class="command">disable-algorithms</strong></span></span></dt>
2751 <dd><p>
2752                 Disable the specified DNSSEC algorithms at and below the
2753                 specified name.
2754                 Multiple <span><strong class="command">disable-algorithms</strong></span>
2755                 statements are allowed.
2756                 Only the most specific will be applied.
2757               </p></dd>
2758 <dt><span class="term"><span><strong class="command">dnssec-lookaside</strong></span></span></dt>
2759 <dd>
2760 <p>
2761                 When set, <span><strong class="command">dnssec-lookaside</strong></span> provides the
2762                 validator with an alternate method to validate DNSKEY
2763                 records at the top of a zone.  When a DNSKEY is at or
2764                 below a domain specified by the deepest
2765                 <span><strong class="command">dnssec-lookaside</strong></span>, and the normal DNSSEC
2766                 validation has left the key untrusted, the trust-anchor
2767                 will be appended to the key name and a DLV record will be
2768                 looked up to see if it can validate the key.  If the DLV
2769                 record validates a DNSKEY (similarly to the way a DS
2770                 record does) the DNSKEY RRset is deemed to be trusted.
2771               </p>
2772 <p>
2773                 If <span><strong class="command">dnssec-lookaside</strong></span> is set to
2774                 <strong class="userinput"><code>auto</code></strong>, then built-in default
2775                 values for the DLV domain and trust anchor will be
2776                 used, along with a built-in key for validation.
2777               </p>
2778 <p>
2779                 If <span><strong class="command">dnssec-lookaside</strong></span> is set to
2780                 <strong class="userinput"><code>no</code></strong>, then dnssec-lookaside
2781                 is not used.
2782               </p>
2783 <p>
2784                 The default DLV key is stored in the file
2785                 <code class="filename">bind.keys</code>;
2786                 <span><strong class="command">named</strong></span> will load that key at
2787                 startup if <span><strong class="command">dnssec-lookaside</strong></span> is set to
2788                 <code class="constant">auto</code>.  A copy of the file is
2789                 installed along with <acronym class="acronym">BIND</acronym> 9, and is
2790                 current as of the release date.  If the DLV key expires, a
2791                 new copy of <code class="filename">bind.keys</code> can be downloaded
2792                 from <a href="https://www.isc.org/solutions/dlv/" target="_top">https://www.isc.org/solutions/dlv/</a>.
2793               </p>
2794 <p>
2795                 (To prevent problems if <code class="filename">bind.keys</code> is
2796                 not found, the current key is also compiled in to
2797                 <span><strong class="command">named</strong></span>.  Relying on this is not
2798                 recommended, however, as it requires <span><strong class="command">named</strong></span>
2799                 to be recompiled with a new key when the DLV key expires.)
2800               </p>
2801 <p>
2802                 NOTE: <span><strong class="command">named</strong></span> only loads certain specific
2803                 keys from <code class="filename">bind.keys</code>:  those for the
2804                 DLV zone and for the DNS root zone.  The file cannot be
2805                 used to store keys for other zones.
2806               </p>
2807 </dd>
2808 <dt><span class="term"><span><strong class="command">dnssec-must-be-secure</strong></span></span></dt>
2809 <dd><p>
2810                 Specify hierarchies which must be or may not be secure
2811                 (signed and validated).  If <strong class="userinput"><code>yes</code></strong>,
2812                 then <span><strong class="command">named</strong></span> will only accept answers if
2813                 they are secure.  If <strong class="userinput"><code>no</code></strong>, then normal
2814                 DNSSEC validation applies allowing for insecure answers to
2815                 be accepted.  The specified domain must be under a
2816                 <span><strong class="command">trusted-keys</strong></span> or
2817                 <span><strong class="command">managed-keys</strong></span> statement, or
2818                 <span><strong class="command">dnssec-lookaside</strong></span> must be active.
2819               </p></dd>
2820 <dt><span class="term"><span><strong class="command">dns64</strong></span></span></dt>
2821 <dd>
2822 <p>
2823                 This directive instructs <span><strong class="command">named</strong></span> to
2824                 return mapped IPv4 addresses to AAAA queries when
2825                 there are no AAAA records.  It is intended to be
2826                 used in conjunction with a NAT64.  Each
2827                 <span><strong class="command">dns64</strong></span> defines one DNS64 prefix.
2828                 Multiple DNS64 prefixes can be defined.
2829               </p>
2830 <p>
2831                 Compatible IPv6 prefixes have lengths of 32, 40, 48, 56,
2832                 64 and 96 as per RFC 6052.
2833               </p>
2834 <p>
2835                 Additionally a reverse IP6.ARPA zone will be created for
2836                 the prefix to provide a mapping from the IP6.ARPA names
2837                 to the corresponding IN-ADDR.ARPA names using synthesized
2838                 CNAMEs.  <span><strong class="command">dns64-server</strong></span> and
2839                 <span><strong class="command">dns64-contact</strong></span> can be used to specify
2840                 the name of the server and contact for the zones. These
2841                 are settable at the view / options level.  These are
2842                 not settable on a per-prefix basis.
2843               </p>
2844 <p>
2845                 Each <span><strong class="command">dns64</strong></span> supports an optional
2846                 <span><strong class="command">clients</strong></span> ACL that determines which
2847                 clients are affected by this directive.  If not defined,
2848                 it defaults to <strong class="userinput"><code>any;</code></strong>.
2849               </p>
2850 <p>
2851                 Each <span><strong class="command">dns64</strong></span> supports an optional
2852                 <span><strong class="command">mapped</strong></span> ACL that selects which
2853                 IPv4 addresses are to be mapped in the corresponding
2854                 A RRset.  If not defined it defaults to
2855                 <strong class="userinput"><code>any;</code></strong>.
2856               </p>
2857 <p>
2858                 Normally, DNS64 won't apply to a domain name that
2859                 owns one or more AAAA records; these records will
2860                 simply be returned.  The optional
2861                 <span><strong class="command">exclude</strong></span> ACL allows specification
2862                 of a list of IPv6 addresses that will be ignored
2863                 if they appear in a domain name's AAAA records, and
2864                 DNS64 will be applied to any A records the domain
2865                 name owns.  If not defined, <span><strong class="command">exclude</strong></span>
2866                 defaults to none.
2867               </p>
2868 <p>
2869                 A optional <span><strong class="command">suffix</strong></span> can also
2870                 be defined to set the bits trailing the mapped
2871                 IPv4 address bits.  By default these bits are
2872                 set to <strong class="userinput"><code>::</code></strong>.  The bits
2873                 matching the prefix and mapped IPv4 address
2874                 must be zero.
2875               </p>
2876 <p>
2877                 If <span><strong class="command">recursive-only</strong></span> is set to
2878                 <span><strong class="command">yes</strong></span> the DNS64 synthesis will
2879                 only happen for recursive queries.  The default
2880                 is <span><strong class="command">no</strong></span>.
2881               </p>
2882 <p>
2883                 If <span><strong class="command">break-dnssec</strong></span> is set to
2884                 <span><strong class="command">yes</strong></span> the DNS64 synthesis will
2885                 happen even if the result, if validated, would
2886                 cause a DNSSEC validation failure.  If this option
2887                 is set to <span><strong class="command">no</strong></span> (the default), the DO
2888                 is set on the incoming query, and there are RRSIGs on
2889                 the applicable records, then synthesis will not happen.
2890               </p>
2891 <pre class="programlisting">
2892         acl rfc1918 { 10/8; 192.168/16; 172.16/12; };
2893
2894         dns64 64:FF9B::/96 {
2895                 clients { any; };
2896                 mapped { !rfc1918; any; };
2897                 exclude { 64:FF9B::/96; ::ffff:0000:0000/96; };
2898                 suffix ::;
2899         };
2900 </pre>
2901 </dd>
2902 <dt><span class="term"><span><strong class="command">dnssec-update-mode</strong></span></span></dt>
2903 <dd>
2904 <p>
2905                   If this option is set to its default value of
2906                   <code class="literal">maintain</code> in a zone of type
2907                   <code class="literal">master</code> which is DNSSEC-signed
2908                   and configured to allow dynamic updates (see
2909                   <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>), and
2910                   if <span><strong class="command">named</strong></span> has access to the
2911                   private signing key(s) for the zone, then
2912                   <span><strong class="command">named</strong></span> will automatically sign all new
2913                   or changed records and maintain signatures for the zone
2914                   by regenerating RRSIG records whenever they approach
2915                   their expiration date.
2916                 </p>
2917 <p>
2918                   If the option is changed to <code class="literal">no-resign</code>,
2919                   then <span><strong class="command">named</strong></span> will sign all new or
2920                   changed records, but scheduled maintenance of
2921                   signatures is disabled.
2922                 </p>
2923 <p>
2924                   With either of these settings, <span><strong class="command">named</strong></span>
2925                   will reject updates to a DNSSEC-signed zone when the
2926                   signing keys are inactive or unavailable to
2927                   <span><strong class="command">named</strong></span>.  (A planned third option,
2928                   <code class="literal">external</code>, will disable all automatic
2929                   signing and allow DNSSEC data to be submitted into a zone
2930                   via dynamic update; this is not yet implemented.)
2931                 </p>
2932 </dd>
2933 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
2934 <dd>
2935 <p>
2936                 If <strong class="userinput"><code>full</code></strong>, the server will collect
2937                 statistical data on all zones (unless specifically
2938                 turned off on a per-zone basis by specifying
2939                 <span><strong class="command">zone-statistics terse</strong></span> or
2940                 <span><strong class="command">zone-statistics none</strong></span>
2941                 in the <span><strong class="command">zone</strong></span> statement).
2942                 The default is <strong class="userinput"><code>terse</code></strong>, providing
2943                 minimal statistics on zones (including name and
2944                 current serial number, but not query type
2945                 counters).
2946               </p>
2947 <p>
2948                 These statistics may be accessed via the
2949                 <span><strong class="command">statistics-channel</strong></span> or
2950                 using <span><strong class="command">rndc stats</strong></span>, which
2951                 will dump them to the file listed
2952                 in the <span><strong class="command">statistics-file</strong></span>.  See
2953                 also <a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
2954               </p>
2955 <p>
2956                 For backward compatibility with earlier versions
2957                 of BIND 9, the <span><strong class="command">zone-statistics</strong></span>
2958                 option can also accept <strong class="userinput"><code>yes</code></strong>
2959                 or <strong class="userinput"><code>no</code></strong>, which have the same
2960                 effect as <strong class="userinput"><code>full</code></strong> and
2961                 <strong class="userinput"><code>terse</code></strong>, respectively.
2962               </p>
2963 </dd>
2964 </dl></div>
2965 <div class="sect3" lang="en">
2966 <div class="titlepage"><div><div><h4 class="title">
2967 <a name="boolean_options"></a>Boolean Options</h4></div></div></div>
2968 <div class="variablelist"><dl>
2969 <dt><span class="term"><span><strong class="command">allow-new-zones</strong></span></span></dt>
2970 <dd><p>
2971                   If <strong class="userinput"><code>yes</code></strong>, then zones can be
2972                   added at runtime via <span><strong class="command">rndc addzone</strong></span>
2973                   or deleted via <span><strong class="command">rndc delzone</strong></span>.
2974                   The default is <strong class="userinput"><code>no</code></strong>.
2975                 </p></dd>
2976 <dt><span class="term"><span><strong class="command">auth-nxdomain</strong></span></span></dt>
2977 <dd><p>
2978                   If <strong class="userinput"><code>yes</code></strong>, then the <span><strong class="command">AA</strong></span> bit
2979                   is always set on NXDOMAIN responses, even if the server is
2980                   not actually
2981                   authoritative. The default is <strong class="userinput"><code>no</code></strong>;
2982                   this is
2983                   a change from <acronym class="acronym">BIND</acronym> 8. If you
2984                   are using very old DNS software, you
2985                   may need to set it to <strong class="userinput"><code>yes</code></strong>.
2986                 </p></dd>
2987 <dt><span class="term"><span><strong class="command">deallocate-on-exit</strong></span></span></dt>
2988 <dd><p>
2989                   This option was used in <acronym class="acronym">BIND</acronym>
2990                   8 to enable checking
2991                   for memory leaks on exit. <acronym class="acronym">BIND</acronym> 9 ignores the option and always performs
2992                   the checks.
2993                 </p></dd>
2994 <dt><span class="term"><span><strong class="command">memstatistics</strong></span></span></dt>
2995 <dd><p>
2996                   Write memory statistics to the file specified by
2997                   <span><strong class="command">memstatistics-file</strong></span> at exit.
2998                   The default is <strong class="userinput"><code>no</code></strong> unless
2999                   '-m record' is specified on the command line in
3000                   which case it is <strong class="userinput"><code>yes</code></strong>.
3001                 </p></dd>
3002 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
3003 <dd>
3004 <p>
3005                   If <strong class="userinput"><code>yes</code></strong>, then the
3006                   server treats all zones as if they are doing zone transfers
3007                   across
3008                   a dial-on-demand dialup link, which can be brought up by
3009                   traffic
3010                   originating from this server. This has different effects
3011                   according
3012                   to zone type and concentrates the zone maintenance so that
3013                   it all
3014                   happens in a short interval, once every <span><strong class="command">heartbeat-interval</strong></span> and
3015                   hopefully during the one call. It also suppresses some of
3016                   the normal
3017                   zone maintenance traffic. The default is <strong class="userinput"><code>no</code></strong>.
3018                 </p>
3019 <p>
3020                   The <span><strong class="command">dialup</strong></span> option
3021                   may also be specified in the <span><strong class="command">view</strong></span> and
3022                   <span><strong class="command">zone</strong></span> statements,
3023                   in which case it overrides the global <span><strong class="command">dialup</strong></span>
3024                   option.
3025                 </p>
3026 <p>
3027                   If the zone is a master zone, then the server will send out a
3028                   NOTIFY
3029                   request to all the slaves (default). This should trigger the
3030                   zone serial
3031                   number check in the slave (providing it supports NOTIFY)
3032                   allowing the slave
3033                   to verify the zone while the connection is active.
3034                   The set of servers to which NOTIFY is sent can be controlled
3035                   by
3036                   <span><strong class="command">notify</strong></span> and <span><strong class="command">also-notify</strong></span>.
3037                 </p>
3038 <p>
3039                   If the
3040                   zone is a slave or stub zone, then the server will suppress
3041                   the regular
3042                   "zone up to date" (refresh) queries and only perform them
3043                   when the
3044                   <span><strong class="command">heartbeat-interval</strong></span> expires in
3045                   addition to sending
3046                   NOTIFY requests.
3047                 </p>
3048 <p>
3049                   Finer control can be achieved by using
3050                   <strong class="userinput"><code>notify</code></strong> which only sends NOTIFY
3051                   messages,
3052                   <strong class="userinput"><code>notify-passive</code></strong> which sends NOTIFY
3053                   messages and
3054                   suppresses the normal refresh queries, <strong class="userinput"><code>refresh</code></strong>
3055                   which suppresses normal refresh processing and sends refresh
3056                   queries
3057                   when the <span><strong class="command">heartbeat-interval</strong></span>
3058                   expires, and
3059                   <strong class="userinput"><code>passive</code></strong> which just disables normal
3060                   refresh
3061                   processing.
3062                 </p>
3063 <div class="informaltable"><table border="1">
3064 <colgroup>
3065 <col>
3066 <col>
3067 <col>
3068 <col>
3069 </colgroup>
3070 <tbody>
3071 <tr>
3072 <td>
3073                           <p>
3074                             dialup mode
3075                           </p>
3076                         </td>
3077 <td>
3078                           <p>
3079                             normal refresh
3080                           </p>
3081                         </td>
3082 <td>
3083                           <p>
3084                             heart-beat refresh
3085                           </p>
3086                         </td>
3087 <td>
3088                           <p>
3089                             heart-beat notify
3090                           </p>
3091                         </td>
3092 </tr>
3093 <tr>
3094 <td>
3095                           <p><span><strong class="command">no</strong></span> (default)</p>
3096                         </td>
3097 <td>
3098                           <p>
3099                             yes
3100                           </p>
3101                         </td>
3102 <td>
3103                           <p>
3104                             no
3105                           </p>
3106                         </td>
3107 <td>
3108                           <p>
3109                             no
3110                           </p>
3111                         </td>
3112 </tr>
3113 <tr>
3114 <td>
3115                           <p><span><strong class="command">yes</strong></span></p>
3116                         </td>
3117 <td>
3118                           <p>
3119                             no
3120                           </p>
3121                         </td>
3122 <td>
3123                           <p>
3124                             yes
3125                           </p>
3126                         </td>
3127 <td>
3128                           <p>
3129                             yes
3130                           </p>
3131                         </td>
3132 </tr>
3133 <tr>
3134 <td>
3135                           <p><span><strong class="command">notify</strong></span></p>
3136                         </td>
3137 <td>
3138                           <p>
3139                             yes
3140                           </p>
3141                         </td>
3142 <td>
3143                           <p>
3144                             no
3145                           </p>
3146                         </td>
3147 <td>
3148                           <p>
3149                             yes
3150                           </p>
3151                         </td>
3152 </tr>
3153 <tr>
3154 <td>
3155                           <p><span><strong class="command">refresh</strong></span></p>
3156                         </td>
3157 <td>
3158                           <p>
3159                             no
3160                           </p>
3161                         </td>
3162 <td>
3163                           <p>
3164                             yes
3165                           </p>
3166                         </td>
3167 <td>
3168                           <p>
3169                             no
3170                           </p>
3171                         </td>
3172 </tr>
3173 <tr>
3174 <td>
3175                           <p><span><strong class="command">passive</strong></span></p>
3176                         </td>
3177 <td>
3178                           <p>
3179                             no
3180                           </p>
3181                         </td>
3182 <td>
3183                           <p>
3184                             no
3185                           </p>
3186                         </td>
3187 <td>
3188                           <p>
3189                             no
3190                           </p>
3191                         </td>
3192 </tr>
3193 <tr>
3194 <td>
3195                           <p><span><strong class="command">notify-passive</strong></span></p>
3196                         </td>
3197 <td>
3198                           <p>
3199                             no
3200                           </p>
3201                         </td>
3202 <td>
3203                           <p>
3204                             no
3205                           </p>
3206                         </td>
3207 <td>
3208                           <p>
3209                             yes
3210                           </p>
3211                         </td>
3212 </tr>
3213 </tbody>
3214 </table></div>
3215 <p>
3216                   Note that normal NOTIFY processing is not affected by
3217                   <span><strong class="command">dialup</strong></span>.
3218                 </p>
3219 </dd>
3220 <dt><span class="term"><span><strong class="command">fake-iquery</strong></span></span></dt>
3221 <dd><p>
3222                   In <acronym class="acronym">BIND</acronym> 8, this option
3223                   enabled simulating the obsolete DNS query type
3224                   IQUERY. <acronym class="acronym">BIND</acronym> 9 never does
3225                   IQUERY simulation.
3226                 </p></dd>
3227 <dt><span class="term"><span><strong class="command">fetch-glue</strong></span></span></dt>
3228 <dd><p>
3229                   This option is obsolete.
3230                   In BIND 8, <strong class="userinput"><code>fetch-glue yes</code></strong>
3231                   caused the server to attempt to fetch glue resource records
3232                   it
3233                   didn't have when constructing the additional
3234                   data section of a response.  This is now considered a bad
3235                   idea
3236                   and BIND 9 never does it.
3237                 </p></dd>
3238 <dt><span class="term"><span><strong class="command">flush-zones-on-shutdown</strong></span></span></dt>
3239 <dd><p>
3240                   When the nameserver exits due receiving SIGTERM,
3241                   flush or do not flush any pending zone writes.  The default
3242                   is
3243                   <span><strong class="command">flush-zones-on-shutdown</strong></span> <strong class="userinput"><code>no</code></strong>.
3244                 </p></dd>
3245 <dt><span class="term"><span><strong class="command">has-old-clients</strong></span></span></dt>
3246 <dd><p>
3247                   This option was incorrectly implemented
3248                   in <acronym class="acronym">BIND</acronym> 8, and is ignored by <acronym class="acronym">BIND</acronym> 9.
3249                   To achieve the intended effect
3250                   of
3251                   <span><strong class="command">has-old-clients</strong></span> <strong class="userinput"><code>yes</code></strong>, specify
3252                   the two separate options <span><strong class="command">auth-nxdomain</strong></span> <strong class="userinput"><code>yes</code></strong>
3253                   and <span><strong class="command">rfc2308-type1</strong></span> <strong class="userinput"><code>no</code></strong> instead.
3254                 </p></dd>
3255 <dt><span class="term"><span><strong class="command">host-statistics</strong></span></span></dt>
3256 <dd><p>
3257                   In BIND 8, this enables keeping of
3258                   statistics for every host that the name server interacts
3259                   with.
3260                   Not implemented in BIND 9.
3261                 </p></dd>
3262 <dt><span class="term"><span><strong class="command">maintain-ixfr-base</strong></span></span></dt>
3263 <dd><p>
3264                   <span class="emphasis"><em>This option is obsolete</em></span>.
3265                   It was used in <acronym class="acronym">BIND</acronym> 8 to
3266                   determine whether a transaction log was
3267                   kept for Incremental Zone Transfer. <acronym class="acronym">BIND</acronym> 9 maintains a transaction
3268                   log whenever possible.  If you need to disable outgoing
3269                   incremental zone
3270                   transfers, use <span><strong class="command">provide-ixfr</strong></span> <strong class="userinput"><code>no</code></strong>.
3271                 </p></dd>
3272 <dt><span class="term"><span><strong class="command">minimal-responses</strong></span></span></dt>
3273 <dd><p>
3274                   If <strong class="userinput"><code>yes</code></strong>, then when generating
3275                   responses the server will only add records to the authority
3276                   and additional data sections when they are required (e.g.
3277                   delegations, negative responses).  This may improve the
3278                   performance of the server.
3279                   The default is <strong class="userinput"><code>no</code></strong>.
3280                 </p></dd>
3281 <dt><span class="term"><span><strong class="command">multiple-cnames</strong></span></span></dt>
3282 <dd><p>
3283                   This option was used in <acronym class="acronym">BIND</acronym> 8 to allow
3284                   a domain name to have multiple CNAME records in violation of
3285                   the DNS standards.  <acronym class="acronym">BIND</acronym> 9.2 onwards
3286                   always strictly enforces the CNAME rules both in master
3287                   files and dynamic updates.
3288                 </p></dd>
3289 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
3290 <dd>
3291 <p>
3292                   If <strong class="userinput"><code>yes</code></strong> (the default),
3293                   DNS NOTIFY messages are sent when a zone the server is
3294                   authoritative for
3295                   changes, see <a href="Bv9ARM.ch04.html#notify" title="Notify">the section called &#8220;Notify&#8221;</a>.  The messages are
3296                   sent to the
3297                   servers listed in the zone's NS records (except the master
3298                   server identified
3299                   in the SOA MNAME field), and to any servers listed in the
3300                   <span><strong class="command">also-notify</strong></span> option.
3301                 </p>
3302 <p>
3303                   If <strong class="userinput"><code>master-only</code></strong>, notifies are only
3304                   sent
3305                   for master zones.
3306                   If <strong class="userinput"><code>explicit</code></strong>, notifies are sent only
3307                   to
3308                   servers explicitly listed using <span><strong class="command">also-notify</strong></span>.
3309                   If <strong class="userinput"><code>no</code></strong>, no notifies are sent.
3310                 </p>
3311 <p>
3312                   The <span><strong class="command">notify</strong></span> option may also be
3313                   specified in the <span><strong class="command">zone</strong></span>
3314                   statement,
3315                   in which case it overrides the <span><strong class="command">options notify</strong></span> statement.
3316                   It would only be necessary to turn off this option if it
3317                   caused slaves
3318                   to crash.
3319                 </p>
3320 </dd>
3321 <dt><span class="term"><span><strong class="command">notify-to-soa</strong></span></span></dt>
3322 <dd><p>
3323                   If <strong class="userinput"><code>yes</code></strong> do not check the nameservers
3324                   in the NS RRset against the SOA MNAME.  Normally a NOTIFY
3325                   message is not sent to the SOA MNAME (SOA ORIGIN) as it is
3326                   supposed to contain the name of the ultimate master.
3327                   Sometimes, however, a slave is listed as the SOA MNAME in
3328                   hidden master configurations and in that case you would
3329                   want the ultimate master to still send NOTIFY messages to
3330                   all the nameservers listed in the NS RRset.
3331                 </p></dd>
3332 <dt><span class="term"><span><strong class="command">recursion</strong></span></span></dt>
3333 <dd><p>
3334                   If <strong class="userinput"><code>yes</code></strong>, and a
3335                   DNS query requests recursion, then the server will attempt
3336                   to do
3337                   all the work required to answer the query. If recursion is
3338                   off
3339                   and the server does not already know the answer, it will
3340                   return a
3341                   referral response. The default is
3342                   <strong class="userinput"><code>yes</code></strong>.
3343                   Note that setting <span><strong class="command">recursion no</strong></span> does not prevent
3344                   clients from getting data from the server's cache; it only
3345                   prevents new data from being cached as an effect of client
3346                   queries.
3347                   Caching may still occur as an effect the server's internal
3348                   operation, such as NOTIFY address lookups.
3349                   See also <span><strong class="command">fetch-glue</strong></span> above.
3350                 </p></dd>
3351 <dt><span class="term"><span><strong class="command">request-nsid</strong></span></span></dt>
3352 <dd><p>
3353                   If <strong class="userinput"><code>yes</code></strong>, then an empty EDNS(0)
3354                   NSID (Name Server Identifier) option is sent with all
3355                   queries to authoritative name servers during iterative
3356                   resolution. If the authoritative server returns an NSID
3357                   option in its response, then its contents are logged in
3358                   the <span><strong class="command">resolver</strong></span> category at level
3359                   <span><strong class="command">info</strong></span>.
3360                   The default is <strong class="userinput"><code>no</code></strong>.
3361                 </p></dd>
3362 <dt><span class="term"><span><strong class="command">rfc2308-type1</strong></span></span></dt>
3363 <dd>
3364 <p>
3365                   Setting this to <strong class="userinput"><code>yes</code></strong> will
3366                   cause the server to send NS records along with the SOA
3367                   record for negative
3368                   answers. The default is <strong class="userinput"><code>no</code></strong>.
3369                 </p>
3370 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3371 <h3 class="title">Note</h3>
3372 <p>
3373                     Not yet implemented in <acronym class="acronym">BIND</acronym>
3374                     9.
3375                   </p>
3376 </div>
3377 </dd>
3378 <dt><span class="term"><span><strong class="command">use-id-pool</strong></span></span></dt>
3379 <dd><p>
3380                   <span class="emphasis"><em>This option is obsolete</em></span>.
3381                   <acronym class="acronym">BIND</acronym> 9 always allocates query
3382                   IDs from a pool.
3383                 </p></dd>
3384 <dt><span class="term"><span><strong class="command">use-ixfr</strong></span></span></dt>
3385 <dd><p>
3386                   <span class="emphasis"><em>This option is obsolete</em></span>.
3387                   If you need to disable IXFR to a particular server or
3388                   servers, see
3389                   the information on the <span><strong class="command">provide-ixfr</strong></span> option
3390                   in <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3391             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3392             Usage&#8221;</a>.
3393                   See also
3394                   <a href="Bv9ARM.ch04.html#incremental_zone_transfers" title="Incremental Zone Transfers (IXFR)">the section called &#8220;Incremental Zone Transfers (IXFR)&#8221;</a>.
3395                 </p></dd>
3396 <dt><span class="term"><span><strong class="command">provide-ixfr</strong></span></span></dt>
3397 <dd><p>
3398                   See the description of
3399                   <span><strong class="command">provide-ixfr</strong></span> in
3400                   <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3401             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3402             Usage&#8221;</a>.
3403                 </p></dd>
3404 <dt><span class="term"><span><strong class="command">request-ixfr</strong></span></span></dt>
3405 <dd><p>
3406                   See the description of
3407                   <span><strong class="command">request-ixfr</strong></span> in
3408                   <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3409             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3410             Usage&#8221;</a>.
3411                 </p></dd>
3412 <dt><span class="term"><span><strong class="command">treat-cr-as-space</strong></span></span></dt>
3413 <dd><p>
3414                   This option was used in <acronym class="acronym">BIND</acronym>
3415                   8 to make
3416                   the server treat carriage return ("<span><strong class="command">\r</strong></span>") characters the same way
3417                   as a space or tab character,
3418                   to facilitate loading of zone files on a UNIX system that
3419                   were generated
3420                   on an NT or DOS machine. In <acronym class="acronym">BIND</acronym> 9, both UNIX "<span><strong class="command">\n</strong></span>"
3421                   and NT/DOS "<span><strong class="command">\r\n</strong></span>" newlines
3422                   are always accepted,
3423                   and the option is ignored.
3424                 </p></dd>
3425 <dt>
3426 <span class="term"><span><strong class="command">additional-from-auth</strong></span>, </span><span class="term"><span><strong class="command">additional-from-cache</strong></span></span>
3427 </dt>
3428 <dd>
3429 <p>
3430                   These options control the behavior of an authoritative
3431                   server when
3432                   answering queries which have additional data, or when
3433                   following CNAME
3434                   and DNAME chains.
3435                 </p>
3436 <p>
3437                   When both of these options are set to <strong class="userinput"><code>yes</code></strong>
3438                   (the default) and a
3439                   query is being answered from authoritative data (a zone
3440                   configured into the server), the additional data section of
3441                   the
3442                   reply will be filled in using data from other authoritative
3443                   zones
3444                   and from the cache.  In some situations this is undesirable,
3445                   such
3446                   as when there is concern over the correctness of the cache,
3447                   or
3448                   in servers where slave zones may be added and modified by
3449                   untrusted third parties.  Also, avoiding
3450                   the search for this additional data will speed up server
3451                   operations
3452                   at the possible expense of additional queries to resolve
3453                   what would
3454                   otherwise be provided in the additional section.
3455                 </p>
3456 <p>
3457                   For example, if a query asks for an MX record for host <code class="literal">foo.example.com</code>,
3458                   and the record found is "<code class="literal">MX 10 mail.example.net</code>", normally the address
3459                   records (A and AAAA) for <code class="literal">mail.example.net</code> will be provided as well,
3460                   if known, even though they are not in the example.com zone.
3461                   Setting these options to <span><strong class="command">no</strong></span>
3462                   disables this behavior and makes
3463                   the server only search for additional data in the zone it
3464                   answers from.
3465                 </p>
3466 <p>
3467                   These options are intended for use in authoritative-only
3468                   servers, or in authoritative-only views.  Attempts to set
3469                   them to <span><strong class="command">no</strong></span> without also
3470                   specifying
3471                   <span><strong class="command">recursion no</strong></span> will cause the
3472                   server to
3473                   ignore the options and log a warning message.
3474                 </p>
3475 <p>
3476                   Specifying <span><strong class="command">additional-from-cache no</strong></span> actually
3477                   disables the use of the cache not only for additional data
3478                   lookups
3479                   but also when looking up the answer.  This is usually the
3480                   desired
3481                   behavior in an authoritative-only server where the
3482                   correctness of
3483                   the cached data is an issue.
3484                 </p>
3485 <p>
3486                   When a name server is non-recursively queried for a name
3487                   that is not
3488                   below the apex of any served zone, it normally answers with
3489                   an
3490                   "upwards referral" to the root servers or the servers of
3491                   some other
3492                   known parent of the query name.  Since the data in an
3493                   upwards referral
3494                   comes from the cache, the server will not be able to provide
3495                   upwards
3496                   referrals when <span><strong class="command">additional-from-cache no</strong></span>
3497                   has been specified.  Instead, it will respond to such
3498                   queries
3499                   with REFUSED.  This should not cause any problems since
3500                   upwards referrals are not required for the resolution
3501                   process.
3502                 </p>
3503 </dd>
3504 <dt><span class="term"><span><strong class="command">match-mapped-addresses</strong></span></span></dt>
3505 <dd>
3506 <p>
3507                   If <strong class="userinput"><code>yes</code></strong>, then an
3508                   IPv4-mapped IPv6 address will match any address match
3509                   list entries that match the corresponding IPv4 address.
3510                 </p>
3511 <p>
3512                   This option was introduced to work around a kernel quirk
3513                   in some operating systems that causes IPv4 TCP
3514                   connections, such as zone transfers, to be accepted on an
3515                   IPv6 socket using mapped addresses.  This caused address
3516                   match lists designed for IPv4 to fail to match.  However,
3517                   <span><strong class="command">named</strong></span> now solves this problem
3518                   internally.  The use of this option is discouraged.
3519                 </p>
3520 </dd>
3521 <dt><span class="term"><span><strong class="command">filter-aaaa-on-v4</strong></span></span></dt>
3522 <dd>
3523 <p>
3524                   This option is only available when
3525                   <acronym class="acronym">BIND</acronym> 9 is compiled with the
3526                   <strong class="userinput"><code>--enable-filter-aaaa</code></strong> option on the
3527                   "configure" command line.  It is intended to help the
3528                   transition from IPv4 to IPv6 by not giving IPv6 addresses
3529                   to DNS clients unless they have connections to the IPv6
3530                   Internet.  This is not recommended unless absolutely
3531                   necessary.  The default is <strong class="userinput"><code>no</code></strong>.
3532                   The <span><strong class="command">filter-aaaa-on-v4</strong></span> option
3533                   may also be specified in <span><strong class="command">view</strong></span> statements
3534                   to override the global <span><strong class="command">filter-aaaa-on-v4</strong></span>
3535                   option.
3536                 </p>
3537 <p>
3538                   If <strong class="userinput"><code>yes</code></strong>,
3539                   the DNS client is at an IPv4 address, in <span><strong class="command">filter-aaaa</strong></span>,
3540                   and if the response does not include DNSSEC signatures,
3541                   then all AAAA records are deleted from the response.
3542                   This filtering applies to all responses and not only
3543                   authoritative responses.
3544                 </p>
3545 <p>
3546                   If <strong class="userinput"><code>break-dnssec</code></strong>,
3547                   then AAAA records are deleted even when dnssec is enabled.
3548                   As suggested by the name, this makes the response not verify,
3549                   because the DNSSEC protocol is designed detect deletions.
3550                 </p>
3551 <p>
3552                   This mechanism can erroneously cause other servers to
3553                   not give AAAA records to their clients.
3554                   A recursing server with both IPv6 and IPv4 network connections
3555                   that queries an authoritative server using this mechanism
3556                   via IPv4 will be denied AAAA records even if its client is
3557                   using IPv6.
3558                 </p>
3559 <p>
3560                   This mechanism is applied to authoritative as well as
3561                   non-authoritative records.
3562                   A client using IPv4 that is not allowed recursion can
3563                   erroneously be given AAAA records because the server is not
3564                   allowed to check for A records.
3565                 </p>
3566 <p>
3567                   Some AAAA records are given to IPv4 clients in glue records.
3568                   IPv4 clients that are servers can then erroneously
3569                   answer requests for AAAA records received via IPv4.
3570                 </p>
3571 </dd>
3572 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
3573 <dd>
3574 <p>
3575                   When <strong class="userinput"><code>yes</code></strong> and the server loads a new
3576                   version of a master zone from its zone file or receives a
3577                   new version of a slave file via zone transfer, it will
3578                   compare the new version to the previous one and calculate
3579                   a set of differences.  The differences are then logged in
3580                   the zone's journal file such that the changes can be
3581                   transmitted to downstream slaves as an incremental zone
3582                   transfer.
3583                 </p>
3584 <p>
3585                   By allowing incremental zone transfers to be used for
3586                   non-dynamic zones, this option saves bandwidth at the
3587                   expense of increased CPU and memory consumption at the
3588                   master.
3589                   In particular, if the new version of a zone is completely
3590                   different from the previous one, the set of differences
3591                   will be of a size comparable to the combined size of the
3592                   old and new zone version, and the server will need to
3593                   temporarily allocate memory to hold this complete
3594                   difference set.
3595                 </p>
3596 <p><span><strong class="command">ixfr-from-differences</strong></span>
3597                   also accepts <span><strong class="command">master</strong></span> and
3598                   <span><strong class="command">slave</strong></span> at the view and options
3599                   levels which causes
3600                   <span><strong class="command">ixfr-from-differences</strong></span> to be enabled for
3601                   all <span><strong class="command">master</strong></span> or
3602                   <span><strong class="command">slave</strong></span> zones respectively.
3603                   It is off by default.
3604                 </p>
3605 </dd>
3606 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
3607 <dd><p>
3608                   This should be set when you have multiple masters for a zone
3609                   and the
3610                   addresses refer to different machines.  If <strong class="userinput"><code>yes</code></strong>, <span><strong class="command">named</strong></span> will
3611                   not log
3612                   when the serial number on the master is less than what <span><strong class="command">named</strong></span>
3613                   currently
3614                   has.  The default is <strong class="userinput"><code>no</code></strong>.
3615                 </p></dd>
3616 <dt><span class="term"><span><strong class="command">dnssec-enable</strong></span></span></dt>
3617 <dd><p>
3618                   Enable DNSSEC support in <span><strong class="command">named</strong></span>.  Unless set to <strong class="userinput"><code>yes</code></strong>,
3619                   <span><strong class="command">named</strong></span> behaves as if it does not support DNSSEC.
3620                   The default is <strong class="userinput"><code>yes</code></strong>.
3621                 </p></dd>
3622 <dt><span class="term"><span><strong class="command">dnssec-validation</strong></span></span></dt>
3623 <dd><p>
3624                   Enable DNSSEC validation in <span><strong class="command">named</strong></span>.
3625                   Note <span><strong class="command">dnssec-enable</strong></span> also needs to be
3626                   set to <strong class="userinput"><code>yes</code></strong> to be effective.
3627                   If set to <strong class="userinput"><code>no</code></strong>, DNSSEC validation
3628                   is disabled.  If set to <strong class="userinput"><code>auto</code></strong>,
3629                   DNSSEC validation is enabled, and a default
3630                   trust-anchor for the DNS root zone is used.  If set to
3631                   <strong class="userinput"><code>yes</code></strong>, DNSSEC validation is enabled,
3632                   but a trust anchor must be manually configured using
3633                   a <span><strong class="command">trusted-keys</strong></span> or
3634                   <span><strong class="command">managed-keys</strong></span> statement.  The default
3635                   is <strong class="userinput"><code>yes</code></strong>.
3636                 </p></dd>
3637 <dt><span class="term"><span><strong class="command">dnssec-accept-expired</strong></span></span></dt>
3638 <dd><p>
3639                   Accept expired signatures when verifying DNSSEC signatures.
3640                   The default is <strong class="userinput"><code>no</code></strong>.
3641                   Setting this option to <strong class="userinput"><code>yes</code></strong>
3642                   leaves <span><strong class="command">named</strong></span> vulnerable to
3643                   replay attacks.
3644                 </p></dd>
3645 <dt><span class="term"><span><strong class="command">querylog</strong></span></span></dt>
3646 <dd><p>
3647                   Specify whether query logging should be started when <span><strong class="command">named</strong></span>
3648                   starts.
3649                   If <span><strong class="command">querylog</strong></span> is not specified,
3650                   then the query logging
3651                   is determined by the presence of the logging category <span><strong class="command">queries</strong></span>.
3652                 </p></dd>
3653 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
3654 <dd>
3655 <p>
3656                   This option is used to restrict the character set and syntax
3657                   of
3658                   certain domain names in master files and/or DNS responses
3659                   received
3660                   from the network.  The default varies according to usage
3661                   area.  For
3662                   <span><strong class="command">master</strong></span> zones the default is <span><strong class="command">fail</strong></span>.
3663                   For <span><strong class="command">slave</strong></span> zones the default
3664                   is <span><strong class="command">warn</strong></span>.
3665                   For answers received from the network (<span><strong class="command">response</strong></span>)
3666                   the default is <span><strong class="command">ignore</strong></span>.
3667                 </p>
3668 <p>
3669                   The rules for legal hostnames and mail domains are derived
3670                   from RFC 952 and RFC 821 as modified by RFC 1123.
3671                 </p>
3672 <p><span><strong class="command">check-names</strong></span>
3673                   applies to the owner names of A, AAAA and MX records.
3674                   It also applies to the domain names in the RDATA of NS, SOA,
3675                   MX, and SRV records.
3676                   It also applies to the RDATA of PTR records where the owner
3677                   name indicated that it is a reverse lookup of a hostname
3678                   (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, or IP6.INT).
3679                 </p>
3680 </dd>
3681 <dt><span class="term"><span><strong class="command">check-dup-records</strong></span></span></dt>
3682 <dd><p>
3683                   Check master zones for records that are treated as different
3684                   by DNSSEC but are semantically equal in plain DNS.  The
3685                   default is to <span><strong class="command">warn</strong></span>.  Other possible
3686                   values are <span><strong class="command">fail</strong></span> and
3687                   <span><strong class="command">ignore</strong></span>.
3688                 </p></dd>
3689 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
3690 <dd><p>
3691                   Check whether the MX record appears to refer to a IP address.
3692                   The default is to <span><strong class="command">warn</strong></span>.  Other possible
3693                   values are <span><strong class="command">fail</strong></span> and
3694                   <span><strong class="command">ignore</strong></span>.
3695                 </p></dd>
3696 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
3697 <dd><p>
3698                   This option is used to check for non-terminal wildcards.
3699                   The use of non-terminal wildcards is almost always as a
3700                   result of a failure
3701                   to understand the wildcard matching algorithm (RFC 1034).
3702                   This option
3703                   affects master zones.  The default (<span><strong class="command">yes</strong></span>) is to check
3704                   for non-terminal wildcards and issue a warning.
3705                 </p></dd>
3706 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
3707 <dd>
3708 <p>
3709                   Perform post load zone integrity checks on master
3710                   zones.  This checks that MX and SRV records refer
3711                   to address (A or AAAA) records and that glue
3712                   address records exist for delegated zones.  For
3713                   MX and SRV records only in-zone hostnames are
3714                   checked (for out-of-zone hostnames use
3715                   <span><strong class="command">named-checkzone</strong></span>).
3716                   For NS records only names below top of zone are
3717                   checked (for out-of-zone names and glue consistency
3718                   checks use <span><strong class="command">named-checkzone</strong></span>).
3719                   The default is <span><strong class="command">yes</strong></span>.
3720                 </p>
3721 <p>
3722                   The use of the SPF record for publishing Sender
3723                   Policy Framework is deprecated as the migration
3724                   from using TXT records to SPF records was abandoned.
3725                   Enabling this option also checks that a TXT Sender
3726                   Policy Framework record exists (starts with "v=spf1")
3727                   if there is an SPF record. Warnings are emitted if the
3728                   TXT record does not exist and can be suppressed with
3729                   <span><strong class="command">check-spf</strong></span>.
3730                 </p>
3731 </dd>
3732 <dt><span class="term"><span><strong class="command">check-mx-cname</strong></span></span></dt>
3733 <dd><p>
3734                   If <span><strong class="command">check-integrity</strong></span> is set then
3735                   fail, warn or ignore MX records that refer
3736                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
3737                 </p></dd>
3738 <dt><span class="term"><span><strong class="command">check-srv-cname</strong></span></span></dt>
3739 <dd><p>
3740                   If <span><strong class="command">check-integrity</strong></span> is set then
3741                   fail, warn or ignore SRV records that refer
3742                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
3743                 </p></dd>
3744 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
3745 <dd><p>
3746                   When performing integrity checks, also check that
3747                   sibling glue exists.  The default is <span><strong class="command">yes</strong></span>.
3748                 </p></dd>
3749 <dt><span class="term"><span><strong class="command">check-spf</strong></span></span></dt>
3750 <dd><p>
3751                   If <span><strong class="command">check-integrity</strong></span> is set then
3752                   check that there is a TXT Sender Policy Framework
3753                   record present (starts with "v=spf1") if there is an
3754                   SPF record present. The default is
3755                   <span><strong class="command">warn</strong></span>.
3756                 </p></dd>
3757 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
3758 <dd><p>
3759                   When returning authoritative negative responses to
3760                   SOA queries set the TTL of the SOA record returned in
3761                   the authority section to zero.
3762                   The default is <span><strong class="command">yes</strong></span>.
3763                 </p></dd>
3764 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl-cache</strong></span></span></dt>
3765 <dd><p>
3766                   When caching a negative response to a SOA query
3767                   set the TTL to zero.
3768                   The default is <span><strong class="command">no</strong></span>.
3769                 </p></dd>
3770 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
3771 <dd>
3772 <p>
3773                   When set to the default value of <code class="literal">yes</code>,
3774                   check the KSK bit in each key to determine how the key
3775                   should be used when generating RRSIGs for a secure zone.
3776                 </p>
3777 <p>
3778                   Ordinarily, zone-signing keys (that is, keys without the
3779                   KSK bit set) are used to sign the entire zone, while
3780                   key-signing keys (keys with the KSK bit set) are only
3781                   used to sign the DNSKEY RRset at the zone apex.
3782                   However, if this option is set to <code class="literal">no</code>,
3783                   then the KSK bit is ignored; KSKs are treated as if they
3784                   were ZSKs and are used to sign the entire zone.  This is
3785                   similar to the <span><strong class="command">dnssec-signzone -z</strong></span>
3786                   command line option.
3787                 </p>
3788 <p>
3789                   When this option is set to <code class="literal">yes</code>, there
3790                   must be at least two active keys for every algorithm
3791                   represented in the DNSKEY RRset: at least one KSK and one
3792                   ZSK per algorithm.  If there is any algorithm for which
3793                   this requirement is not met, this option will be ignored
3794                   for that algorithm.
3795                 </p>
3796 </dd>
3797 <dt><span class="term"><span><strong class="command">dnssec-dnskey-kskonly</strong></span></span></dt>
3798 <dd>
3799 <p>
3800                   When this option and <span><strong class="command">update-check-ksk</strong></span>
3801                   are both set to <code class="literal">yes</code>, only key-signing
3802                   keys (that is, keys with the KSK bit set) will be used
3803                   to sign the DNSKEY RRset at the zone apex.  Zone-signing
3804                   keys (keys without the KSK bit set) will be used to sign
3805                   the remainder of the zone, but not the DNSKEY RRset.
3806                   This is similar to the
3807                   <span><strong class="command">dnssec-signzone -x</strong></span> command line option.
3808                 </p>
3809 <p>
3810                   The default is <span><strong class="command">no</strong></span>.  If
3811                   <span><strong class="command">update-check-ksk</strong></span> is set to
3812                   <code class="literal">no</code>, this option is ignored.
3813                 </p>
3814 </dd>
3815 <dt><span class="term"><span><strong class="command">dnssec-loadkeys-interval</strong></span></span></dt>
3816 <dd><p>
3817                   When a zone is configured with <span><strong class="command">auto-dnssec
3818                   maintain;</strong></span> its key repository must be checked
3819                   periodically to see if any new keys have been added
3820                   or any existing keys' timing metadata has been updated
3821                   (see <a href="man.dnssec-keygen.html" title="dnssec-keygen"><span class="refentrytitle"><span class="application">dnssec-keygen</span></span>(8)</a> and
3822                   <a href="man.dnssec-settime.html" title="dnssec-settime"><span class="refentrytitle"><span class="application">dnssec-settime</span></span>(8)</a>).  The
3823                   <span><strong class="command">dnssec-loadkeys-interval</strong></span> option
3824                   sets the frequency of automatic repository checks, in
3825                   minutes.  The default is <code class="literal">60</code> (1 hour),
3826                   the minimum is <code class="literal">1</code> (1 minute), and the
3827                   maximum is <code class="literal">1440</code> (24 hours); any higher
3828                   value is silently reduced.
3829                 </p></dd>
3830 <dt><span class="term"><span><strong class="command">try-tcp-refresh</strong></span></span></dt>
3831 <dd><p>
3832                   Try to refresh the zone using TCP if UDP queries fail.
3833                   For BIND 8 compatibility, the default is
3834                   <span><strong class="command">yes</strong></span>.
3835                 </p></dd>
3836 <dt><span class="term"><span><strong class="command">dnssec-secure-to-insecure</strong></span></span></dt>
3837 <dd>
3838 <p>
3839                   Allow a dynamic zone to transition from secure to
3840                   insecure (i.e., signed to unsigned) by deleting all
3841                   of the DNSKEY records.  The default is <span><strong class="command">no</strong></span>.
3842                   If set to <span><strong class="command">yes</strong></span>, and if the DNSKEY RRset
3843                   at the zone apex is deleted, all RRSIG and NSEC records
3844                   will be removed from the zone as well.
3845                 </p>
3846 <p>
3847                   If the zone uses NSEC3, then it is also necessary to
3848                   delete the NSEC3PARAM RRset from the zone apex; this will
3849                   cause the removal of all corresponding NSEC3 records.
3850                   (It is expected that this requirement will be eliminated
3851                   in a future release.)
3852                 </p>
3853 <p>
3854                   Note that if a zone has been configured with
3855                   <span><strong class="command">auto-dnssec maintain</strong></span> and the
3856                   private keys remain accessible in the key repository,
3857                   then the zone will be automatically signed again the
3858                   next time <span><strong class="command">named</strong></span> is started.
3859                 </p>
3860 </dd>
3861 </dl></div>
3862 </div>
3863 <div class="sect3" lang="en">
3864 <div class="titlepage"><div><div><h4 class="title">
3865 <a name="id2583425"></a>Forwarding</h4></div></div></div>
3866 <p>
3867             The forwarding facility can be used to create a large site-wide
3868             cache on a few servers, reducing traffic over links to external
3869             name servers. It can also be used to allow queries by servers that
3870             do not have direct access to the Internet, but wish to look up
3871             exterior
3872             names anyway. Forwarding occurs only on those queries for which
3873             the server is not authoritative and does not have the answer in
3874             its cache.
3875           </p>
3876 <div class="variablelist"><dl>
3877 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
3878 <dd><p>
3879                   This option is only meaningful if the
3880                   forwarders list is not empty. A value of <code class="varname">first</code>,
3881                   the default, causes the server to query the forwarders
3882                   first &#8212; and
3883                   if that doesn't answer the question, the server will then
3884                   look for
3885                   the answer itself. If <code class="varname">only</code> is
3886                   specified, the
3887                   server will only query the forwarders.
3888                 </p></dd>
3889 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
3890 <dd><p>
3891                   Specifies the IP addresses to be used
3892                   for forwarding. The default is the empty list (no
3893                   forwarding).
3894                 </p></dd>
3895 </dl></div>
3896 <p>
3897             Forwarding can also be configured on a per-domain basis, allowing
3898             for the global forwarding options to be overridden in a variety
3899             of ways. You can set particular domains to use different
3900             forwarders,
3901             or have a different <span><strong class="command">forward only/first</strong></span> behavior,
3902             or not forward at all, see <a href="Bv9ARM.ch06.html#zone_statement_grammar" title="zone
3903             Statement Grammar">the section called &#8220;<span><strong class="command">zone</strong></span>
3904             Statement Grammar&#8221;</a>.
3905           </p>
3906 </div>
3907 <div class="sect3" lang="en">
3908 <div class="titlepage"><div><div><h4 class="title">
3909 <a name="id2583483"></a>Dual-stack Servers</h4></div></div></div>
3910 <p>
3911             Dual-stack servers are used as servers of last resort to work
3912             around
3913             problems in reachability due the lack of support for either IPv4
3914             or IPv6
3915             on the host machine.
3916           </p>
3917 <div class="variablelist"><dl>
3918 <dt><span class="term"><span><strong class="command">dual-stack-servers</strong></span></span></dt>
3919 <dd><p>
3920                   Specifies host names or addresses of machines with access to
3921                   both IPv4 and IPv6 transports. If a hostname is used, the
3922                   server must be able
3923                   to resolve the name using only the transport it has.  If the
3924                   machine is dual
3925                   stacked, then the <span><strong class="command">dual-stack-servers</strong></span> have no effect unless
3926                   access to a transport has been disabled on the command line
3927                   (e.g. <span><strong class="command">named -4</strong></span>).
3928                 </p></dd>
3929 </dl></div>
3930 </div>
3931 <div class="sect3" lang="en">
3932 <div class="titlepage"><div><div><h4 class="title">
3933 <a name="access_control"></a>Access Control</h4></div></div></div>
3934 <p>
3935             Access to the server can be restricted based on the IP address
3936             of the requesting system. See <a href="Bv9ARM.ch06.html#address_match_lists" title="Address Match Lists">the section called &#8220;Address Match Lists&#8221;</a> for
3937             details on how to specify IP address lists.
3938           </p>
3939 <div class="variablelist"><dl>
3940 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
3941 <dd><p>
3942                   Specifies which hosts are allowed to
3943                   notify this server, a slave, of zone changes in addition
3944                   to the zone masters.
3945                   <span><strong class="command">allow-notify</strong></span> may also be
3946                   specified in the
3947                   <span><strong class="command">zone</strong></span> statement, in which case
3948                   it overrides the
3949                   <span><strong class="command">options allow-notify</strong></span>
3950                   statement.  It is only meaningful
3951                   for a slave zone.  If not specified, the default is to
3952                   process notify messages
3953                   only from a zone's master.
3954                 </p></dd>
3955 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
3956 <dd>
3957 <p>
3958                   Specifies which hosts are allowed to ask ordinary
3959                   DNS questions. <span><strong class="command">allow-query</strong></span> may
3960                   also be specified in the <span><strong class="command">zone</strong></span>
3961                   statement, in which case it overrides the
3962                   <span><strong class="command">options allow-query</strong></span> statement.
3963                   If not specified, the default is to allow queries
3964                   from all hosts.
3965                 </p>
3966 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3967 <h3 class="title">Note</h3>
3968 <p>
3969                     <span><strong class="command">allow-query-cache</strong></span> is now
3970                     used to specify access to the cache.
3971                   </p>
3972 </div>
3973 </dd>
3974 <dt><span class="term"><span><strong class="command">allow-query-on</strong></span></span></dt>
3975 <dd>
3976 <p>
3977                   Specifies which local addresses can accept ordinary
3978                   DNS questions. This makes it possible, for instance,
3979                   to allow queries on internal-facing interfaces but
3980                   disallow them on external-facing ones, without
3981                   necessarily knowing the internal network's addresses.
3982                 </p>
3983 <p>
3984                   Note that <span><strong class="command">allow-query-on</strong></span> is only
3985                   checked for queries that are permitted by
3986                   <span><strong class="command">allow-query</strong></span>.  A query must be
3987                   allowed by both ACLs, or it will be refused.
3988                 </p>
3989 <p>
3990                   <span><strong class="command">allow-query-on</strong></span> may
3991                   also be specified in the <span><strong class="command">zone</strong></span>
3992                   statement, in which case it overrides the
3993                   <span><strong class="command">options allow-query-on</strong></span> statement.
3994                 </p>
3995 <p>
3996                   If not specified, the default is to allow queries
3997                   on all addresses.
3998                 </p>
3999 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4000 <h3 class="title">Note</h3>
4001 <p>
4002                     <span><strong class="command">allow-query-cache</strong></span> is
4003                     used to specify access to the cache.
4004                   </p>
4005 </div>
4006 </dd>
4007 <dt><span class="term"><span><strong class="command">allow-query-cache</strong></span></span></dt>
4008 <dd><p>
4009                   Specifies which hosts are allowed to get answers
4010                   from the cache.  If <span><strong class="command">allow-query-cache</strong></span>
4011                   is not set then <span><strong class="command">allow-recursion</strong></span>
4012                   is used if set, otherwise <span><strong class="command">allow-query</strong></span>
4013                   is used if set unless <span><strong class="command">recursion no;</strong></span> is
4014                   set in which case <span><strong class="command">none;</strong></span> is used,
4015                   otherwise the default (<span><strong class="command">localnets;</strong></span>
4016                   <span><strong class="command">localhost;</strong></span>) is used.
4017                 </p></dd>
4018 <dt><span class="term"><span><strong class="command">allow-query-cache-on</strong></span></span></dt>
4019 <dd><p>
4020                   Specifies which local addresses can give answers
4021                   from the cache.  If not specified, the default is
4022                   to allow cache queries on any address,
4023                   <span><strong class="command">localnets</strong></span> and
4024                   <span><strong class="command">localhost</strong></span>.
4025                 </p></dd>
4026 <dt><span class="term"><span><strong class="command">allow-recursion</strong></span></span></dt>
4027 <dd><p>
4028                   Specifies which hosts are allowed to make recursive
4029                   queries through this server. If
4030                   <span><strong class="command">allow-recursion</strong></span> is not set
4031                   then <span><strong class="command">allow-query-cache</strong></span> is
4032                   used if set, otherwise <span><strong class="command">allow-query</strong></span>
4033                   is used if set, otherwise the default
4034                   (<span><strong class="command">localnets;</strong></span>
4035                   <span><strong class="command">localhost;</strong></span>) is used.
4036                 </p></dd>
4037 <dt><span class="term"><span><strong class="command">allow-recursion-on</strong></span></span></dt>
4038 <dd><p>
4039                   Specifies which local addresses can accept recursive
4040                   queries.  If not specified, the default is to allow
4041                   recursive queries on all addresses.
4042                 </p></dd>
4043 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
4044 <dd><p>
4045                   Specifies which hosts are allowed to
4046                   submit Dynamic DNS updates for master zones. The default is
4047                   to deny
4048                   updates from all hosts.  Note that allowing updates based
4049                   on the requestor's IP address is insecure; see
4050                   <a href="Bv9ARM.ch07.html#dynamic_update_security" title="Dynamic Update Security">the section called &#8220;Dynamic Update Security&#8221;</a> for details.
4051                 </p></dd>
4052 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
4053 <dd>
4054 <p>
4055                   Specifies which hosts are allowed to
4056                   submit Dynamic DNS updates to slave zones to be forwarded to
4057                   the
4058                   master.  The default is <strong class="userinput"><code>{ none; }</code></strong>,
4059                   which
4060                   means that no update forwarding will be performed.  To
4061                   enable
4062                   update forwarding, specify
4063                   <strong class="userinput"><code>allow-update-forwarding { any; };</code></strong>.
4064                   Specifying values other than <strong class="userinput"><code>{ none; }</code></strong> or
4065                   <strong class="userinput"><code>{ any; }</code></strong> is usually
4066                   counterproductive, since
4067                   the responsibility for update access control should rest
4068                   with the
4069                   master server, not the slaves.
4070                 </p>
4071 <p>
4072                   Note that enabling the update forwarding feature on a slave
4073                   server
4074                   may expose master servers relying on insecure IP address
4075                   based
4076                   access control to attacks; see <a href="Bv9ARM.ch07.html#dynamic_update_security" title="Dynamic Update Security">the section called &#8220;Dynamic Update Security&#8221;</a>
4077                   for more details.
4078                 </p>
4079 </dd>
4080 <dt><span class="term"><span><strong class="command">allow-v6-synthesis</strong></span></span></dt>
4081 <dd><p>
4082                   This option was introduced for the smooth transition from
4083                   AAAA
4084                   to A6 and from "nibble labels" to binary labels.
4085                   However, since both A6 and binary labels were then
4086                   deprecated,
4087                   this option was also deprecated.
4088                   It is now ignored with some warning messages.
4089                 </p></dd>
4090 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
4091 <dd><p>
4092                   Specifies which hosts are allowed to
4093                   receive zone transfers from the server. <span><strong class="command">allow-transfer</strong></span> may
4094                   also be specified in the <span><strong class="command">zone</strong></span>
4095                   statement, in which
4096                   case it overrides the <span><strong class="command">options allow-transfer</strong></span> statement.
4097                   If not specified, the default is to allow transfers to all
4098                   hosts.
4099                 </p></dd>
4100 <dt><span class="term"><span><strong class="command">blackhole</strong></span></span></dt>
4101 <dd><p>
4102                   Specifies a list of addresses that the
4103                   server will not accept queries from or use to resolve a
4104                   query. Queries
4105                   from these addresses will not be responded to. The default
4106                   is <strong class="userinput"><code>none</code></strong>.
4107                 </p></dd>
4108 <dt><span class="term"><span><strong class="command">filter-aaaa</strong></span></span></dt>
4109 <dd><p>
4110                   Specifies a list of addresses to which
4111                   <span><strong class="command">filter-aaaa-on-v4</strong></span>
4112                   is applies.  The default is <strong class="userinput"><code>any</code></strong>.
4113                 </p></dd>
4114 <dt><span class="term"><span><strong class="command">no-case-compress</strong></span></span></dt>
4115 <dd>
4116 <p>
4117                   Specifies a list of addresses which require responses
4118                   to use case-insensitive compression.  This ACL can be
4119                   used when <span><strong class="command">named</strong></span> needs to work with
4120                   clients that do not comply with the requirement in RFC
4121                   1034 to use case-insensitive name comparisons when
4122                   checking for matching domain names.
4123                 </p>
4124 <p>
4125                   If left undefined, the ACL defaults to
4126                   <span><strong class="command">none</strong></span>: case-insensitive compression
4127                   will be used for all clients.  If the ACL is defined and
4128                   matches a client, then case will be ignored when
4129                   compressing domain names in DNS responses sent to that
4130                   client.
4131                 </p>
4132 <p>
4133                   This can result in slightly smaller responses: if
4134                   a response contains the names "example.com" and
4135                   "example.COM", case-insensitive compression would treat
4136                   the second one as a duplicate.  It also ensures
4137                   that the case of the query name exactly matches the
4138                   case of the owner names of returned records, rather
4139                   than matching the case of the records entered in
4140                   the zone file.  This allows responses to exactly
4141                   match the query, which is required by some clients
4142                   due to incorrect use of case-sensitive comparisons.
4143                 </p>
4144 <p>
4145                   Case-insensitive compression is <span class="emphasis"><em>always</em></span>
4146                   used in AXFR and IXFR responses, regardless of whether
4147                   the client matches this ACL.
4148                 </p>
4149 <p>
4150                   There are circumstances in which <span><strong class="command">named</strong></span>
4151                   will not preserve the case of owner names of records:
4152                   if a zone file defines records of different types with
4153                   the same name, but the capitalization of the name is
4154                   different (e.g., "www.example.com/A" and
4155                   "WWW.EXAMPLE.COM/AAAA"), then all responses for that
4156                   name will use the <span class="emphasis"><em>first</em></span> version
4157                   of the name that was used in the zone file.  This
4158                   limitation may be addressed in a future release.  However,
4159                   domain names specified in the rdata of resource records
4160                   (i.e., records of type NS, MX, CNAME, etc) will always
4161                   have their case preserved unless the client matches this
4162                   ACL.
4163                 </p>
4164 </dd>
4165 <dt><span class="term"><span><strong class="command">resolver-query-timeout</strong></span></span></dt>
4166 <dd><p>
4167                   The amount of time the resolver will spend attempting
4168                   to resolve a recursive query before failing.  The default
4169                   and minimum is <code class="literal">10</code> and the maximum is
4170                   <code class="literal">30</code>.  Setting it to <code class="literal">0</code>
4171                   will result in the default being used.
4172                 </p></dd>
4173 </dl></div>
4174 </div>
4175 <div class="sect3" lang="en">
4176 <div class="titlepage"><div><div><h4 class="title">
4177 <a name="id2584157"></a>Interfaces</h4></div></div></div>
4178 <p>
4179             The interfaces and ports that the server will answer queries
4180             from may be specified using the <span><strong class="command">listen-on</strong></span> option. <span><strong class="command">listen-on</strong></span> takes
4181             an optional port and an <code class="varname">address_match_list</code>
4182             of IPv4 addresses.  (IPv6 addresses are ignored, with a
4183             logged warning.)
4184             The server will listen on all interfaces allowed by the address
4185             match list. If a port is not specified, port 53 will be used.
4186           </p>
4187 <p>
4188             Multiple <span><strong class="command">listen-on</strong></span> statements are
4189             allowed.
4190             For example,
4191           </p>
4192 <pre class="programlisting">listen-on { 5.6.7.8; };
4193 listen-on port 1234 { !1.2.3.4; 1.2/16; };
4194 </pre>
4195 <p>
4196             will enable the name server on port 53 for the IP address
4197             5.6.7.8, and on port 1234 of an address on the machine in net
4198             1.2 that is not 1.2.3.4.
4199           </p>
4200 <p>
4201             If no <span><strong class="command">listen-on</strong></span> is specified, the
4202             server will listen on port 53 on all IPv4 interfaces.
4203           </p>
4204 <p>
4205             The <span><strong class="command">listen-on-v6</strong></span> option is used to
4206             specify the interfaces and the ports on which the server will
4207             listen
4208             for incoming queries sent using IPv6.
4209           </p>
4210 <p>
4211             When </p>
4212 <pre class="programlisting">{ any; }</pre>
4213 <p> is
4214             specified
4215             as the <code class="varname">address_match_list</code> for the
4216             <span><strong class="command">listen-on-v6</strong></span> option,
4217             the server does not bind a separate socket to each IPv6 interface
4218             address as it does for IPv4 if the operating system has enough API
4219             support for IPv6 (specifically if it conforms to RFC 3493 and RFC
4220             3542).
4221             Instead, it listens on the IPv6 wildcard address.
4222             If the system only has incomplete API support for IPv6, however,
4223             the behavior is the same as that for IPv4.
4224           </p>
4225 <p>
4226             A list of particular IPv6 addresses can also be specified, in
4227             which case
4228             the server listens on a separate socket for each specified
4229             address,
4230             regardless of whether the desired API is supported by the system.
4231             IPv4 addresses specified in <span><strong class="command">listen-on-v6</strong></span>
4232             will be ignored, with a logged warning.
4233           </p>
4234 <p>
4235             Multiple <span><strong class="command">listen-on-v6</strong></span> options can
4236             be used.
4237             For example,
4238           </p>
4239 <pre class="programlisting">listen-on-v6 { any; };
4240 listen-on-v6 port 1234 { !2001:db8::/32; any; };
4241 </pre>
4242 <p>
4243             will enable the name server on port 53 for any IPv6 addresses
4244             (with a single wildcard socket),
4245             and on port 1234 of IPv6 addresses that is not in the prefix
4246             2001:db8::/32 (with separate sockets for each matched address.)
4247           </p>
4248 <p>
4249             To make the server not listen on any IPv6 address, use
4250           </p>
4251 <pre class="programlisting">listen-on-v6 { none; };
4252 </pre>
4253 <p>
4254             If no <span><strong class="command">listen-on-v6</strong></span> option is
4255             specified, the server will not listen on any IPv6 address
4256             unless <span><strong class="command">-6</strong></span> is specified when <span><strong class="command">named</strong></span> is
4257             invoked.  If <span><strong class="command">-6</strong></span> is specified then
4258             <span><strong class="command">named</strong></span> will listen on port 53 on all IPv6 interfaces by default.
4259           </p>
4260 </div>
4261 <div class="sect3" lang="en">
4262 <div class="titlepage"><div><div><h4 class="title">
4263 <a name="query_address"></a>Query Address</h4></div></div></div>
4264 <p>
4265             If the server doesn't know the answer to a question, it will
4266             query other name servers. <span><strong class="command">query-source</strong></span> specifies
4267             the address and port used for such queries. For queries sent over
4268             IPv6, there is a separate <span><strong class="command">query-source-v6</strong></span> option.
4269             If <span><strong class="command">address</strong></span> is <span><strong class="command">*</strong></span> (asterisk) or is omitted,
4270             a wildcard IP address (<span><strong class="command">INADDR_ANY</strong></span>)
4271             will be used.
4272           </p>
4273 <p>
4274             If <span><strong class="command">port</strong></span> is <span><strong class="command">*</strong></span> or is omitted,
4275             a random port number from a pre-configured
4276             range is picked up and will be used for each query.
4277             The port range(s) is that specified in
4278             the <span><strong class="command">use-v4-udp-ports</strong></span> (for IPv4)
4279             and <span><strong class="command">use-v6-udp-ports</strong></span> (for IPv6)
4280             options, excluding the ranges specified in
4281             the <span><strong class="command">avoid-v4-udp-ports</strong></span>
4282             and <span><strong class="command">avoid-v6-udp-ports</strong></span> options, respectively.
4283           </p>
4284 <p>
4285             The defaults of the <span><strong class="command">query-source</strong></span> and
4286             <span><strong class="command">query-source-v6</strong></span> options
4287             are:
4288           </p>
4289 <pre class="programlisting">query-source address * port *;
4290 query-source-v6 address * port *;
4291 </pre>
4292 <p>
4293             If <span><strong class="command">use-v4-udp-ports</strong></span> or
4294             <span><strong class="command">use-v6-udp-ports</strong></span> is unspecified,
4295             <span><strong class="command">named</strong></span> will check if the operating
4296             system provides a programming interface to retrieve the
4297             system's default range for ephemeral ports.
4298             If such an interface is available,
4299             <span><strong class="command">named</strong></span> will use the corresponding system
4300             default range; otherwise, it will use its own defaults:
4301          </p>
4302 <pre class="programlisting">use-v4-udp-ports { range 1024 65535; };
4303 use-v6-udp-ports { range 1024 65535; };
4304 </pre>
4305 <p>
4306             Note: make sure the ranges be sufficiently large for
4307             security.  A desirable size depends on various parameters,
4308             but we generally recommend it contain at least 16384 ports
4309             (14 bits of entropy).
4310             Note also that the system's default range when used may be
4311             too small for this purpose, and that the range may even be
4312             changed while <span><strong class="command">named</strong></span> is running; the new
4313             range will automatically be applied when <span><strong class="command">named</strong></span>
4314             is reloaded.
4315             It is encouraged to
4316             configure <span><strong class="command">use-v4-udp-ports</strong></span> and
4317             <span><strong class="command">use-v6-udp-ports</strong></span> explicitly so that the
4318             ranges are sufficiently large and are reasonably
4319             independent from the ranges used by other applications.
4320           </p>
4321 <p>
4322             Note: the operational configuration
4323             where <span><strong class="command">named</strong></span> runs may prohibit the use
4324             of some ports.  For example, UNIX systems will not allow
4325             <span><strong class="command">named</strong></span> running without a root privilege
4326             to use ports less than 1024.
4327             If such ports are included in the specified (or detected)
4328             set of query ports, the corresponding query attempts will
4329             fail, resulting in resolution failures or delay.
4330             It is therefore important to configure the set of ports
4331             that can be safely used in the expected operational environment.
4332           </p>
4333 <p>
4334             The defaults of the <span><strong class="command">avoid-v4-udp-ports</strong></span> and
4335             <span><strong class="command">avoid-v6-udp-ports</strong></span> options
4336             are:
4337           </p>
4338 <pre class="programlisting">avoid-v4-udp-ports {};
4339 avoid-v6-udp-ports {};
4340 </pre>
4341 <p>
4342             Note: BIND 9.5.0 introduced
4343             the <span><strong class="command">use-queryport-pool</strong></span>
4344             option to support a pool of such random ports, but this
4345             option is now obsolete because reusing the same ports in
4346             the pool may not be sufficiently secure.
4347             For the same reason, it is generally strongly discouraged to
4348             specify a particular port for the
4349             <span><strong class="command">query-source</strong></span> or
4350             <span><strong class="command">query-source-v6</strong></span> options;
4351             it implicitly disables the use of randomized port numbers.
4352           </p>
4353 <div class="variablelist"><dl>
4354 <dt><span class="term"><span><strong class="command">use-queryport-pool</strong></span></span></dt>
4355 <dd><p>
4356                   This option is obsolete.
4357                 </p></dd>
4358 <dt><span class="term"><span><strong class="command">queryport-pool-ports</strong></span></span></dt>
4359 <dd><p>
4360                   This option is obsolete.
4361                 </p></dd>
4362 <dt><span class="term"><span><strong class="command">queryport-pool-updateinterval</strong></span></span></dt>
4363 <dd><p>
4364                   This option is obsolete.
4365                 </p></dd>
4366 </dl></div>
4367 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4368 <h3 class="title">Note</h3>
4369 <p>
4370               The address specified in the <span><strong class="command">query-source</strong></span> option
4371               is used for both UDP and TCP queries, but the port applies only
4372               to UDP queries.  TCP queries always use a random
4373               unprivileged port.
4374             </p>
4375 </div>
4376 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4377 <h3 class="title">Note</h3>
4378 <p>
4379               Solaris 2.5.1 and earlier does not support setting the source
4380               address for TCP sockets.
4381             </p>
4382 </div>
4383 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4384 <h3 class="title">Note</h3>
4385 <p>
4386               See also <span><strong class="command">transfer-source</strong></span> and
4387               <span><strong class="command">notify-source</strong></span>.
4388             </p>
4389 </div>
4390 </div>
4391 <div class="sect3" lang="en">
4392 <div class="titlepage"><div><div><h4 class="title">
4393 <a name="zone_transfers"></a>Zone Transfers</h4></div></div></div>
4394 <p>
4395             <acronym class="acronym">BIND</acronym> has mechanisms in place to
4396             facilitate zone transfers
4397             and set limits on the amount of load that transfers place on the
4398             system. The following options apply to zone transfers.
4399           </p>
4400 <div class="variablelist"><dl>
4401 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
4402 <dd>
4403 <p>
4404                   Defines a global list of IP addresses of name servers
4405                   that are also sent NOTIFY messages whenever a fresh copy of
4406                   the
4407                   zone is loaded, in addition to the servers listed in the
4408                   zone's NS records.
4409                   This helps to ensure that copies of the zones will
4410                   quickly converge on stealth servers.
4411                   Optionally, a port may be specified with each
4412                   <span><strong class="command">also-notify</strong></span> address to send
4413                   the notify messages to a port other than the
4414                   default of 53.
4415                   An optional TSIG key can also be specified with each
4416                   address to cause the notify messages to be signed; this
4417                   can be useful when sending notifies to multiple views.
4418                   In place of explicit addresses, one or more named
4419                   <span><strong class="command">masters</strong></span> lists can be used.
4420                 </p>
4421 <p>
4422                   If an <span><strong class="command">also-notify</strong></span> list
4423                   is given in a <span><strong class="command">zone</strong></span> statement,
4424                   it will override
4425                   the <span><strong class="command">options also-notify</strong></span>
4426                   statement. When a <span><strong class="command">zone notify</strong></span>
4427                   statement
4428                   is set to <span><strong class="command">no</strong></span>, the IP
4429                   addresses in the global <span><strong class="command">also-notify</strong></span> list will
4430                   not be sent NOTIFY messages for that zone. The default is
4431                   the empty
4432                   list (no global notification list).
4433                 </p>
4434 </dd>
4435 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
4436 <dd><p>
4437                   Inbound zone transfers running longer than
4438                   this many minutes will be terminated. The default is 120
4439                   minutes
4440                   (2 hours).  The maximum value is 28 days (40320 minutes).
4441                 </p></dd>
4442 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
4443 <dd><p>
4444                   Inbound zone transfers making no progress
4445                   in this many minutes will be terminated. The default is 60
4446                   minutes
4447                   (1 hour).  The maximum value is 28 days (40320 minutes).
4448                 </p></dd>
4449 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
4450 <dd><p>
4451                   Outbound zone transfers running longer than
4452                   this many minutes will be terminated. The default is 120
4453                   minutes
4454                   (2 hours).  The maximum value is 28 days (40320 minutes).
4455                 </p></dd>
4456 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
4457 <dd><p>
4458                   Outbound zone transfers making no progress
4459                   in this many minutes will be terminated.  The default is 60
4460                   minutes (1
4461                   hour).  The maximum value is 28 days (40320 minutes).
4462                 </p></dd>
4463 <dt><span class="term"><span><strong class="command">serial-query-rate</strong></span></span></dt>
4464 <dd>
4465 <p>
4466                   Slave servers will periodically query master
4467                   servers to find out if zone serial numbers have
4468                   changed. Each such query uses a minute amount of
4469                   the slave server's network bandwidth.  To limit
4470                   the amount of bandwidth used, BIND 9 limits the
4471                   rate at which queries are sent.  The value of the
4472                   <span><strong class="command">serial-query-rate</strong></span> option, an
4473                   integer, is the maximum number of queries sent
4474                   per second.  The default is 20.
4475                 </p>
4476 <p>
4477                   In addition to controlling the rate SOA refresh
4478                   queries are issued at
4479                   <span><strong class="command">serial-query-rate</strong></span> also controls
4480                   the rate at which NOTIFY messages are sent from
4481                   both master and slave zones.
4482                 </p>
4483 </dd>
4484 <dt><span class="term"><span><strong class="command">serial-queries</strong></span></span></dt>
4485 <dd><p>
4486                   In BIND 8, the <span><strong class="command">serial-queries</strong></span>
4487                   option
4488                   set the maximum number of concurrent serial number queries
4489                   allowed to be outstanding at any given time.
4490                   BIND 9 does not limit the number of outstanding
4491                   serial queries and ignores the <span><strong class="command">serial-queries</strong></span> option.
4492                   Instead, it limits the rate at which the queries are sent
4493                   as defined using the <span><strong class="command">serial-query-rate</strong></span> option.
4494                 </p></dd>
4495 <dt><span class="term"><span><strong class="command">transfer-format</strong></span></span></dt>
4496 <dd><p>
4497                   Zone transfers can be sent using two different formats,
4498                   <span><strong class="command">one-answer</strong></span> and
4499                   <span><strong class="command">many-answers</strong></span>.
4500                   The <span><strong class="command">transfer-format</strong></span> option is used
4501                   on the master server to determine which format it sends.
4502                   <span><strong class="command">one-answer</strong></span> uses one DNS message per
4503                   resource record transferred.
4504                   <span><strong class="command">many-answers</strong></span> packs as many resource
4505                   records as possible into a message.
4506                   <span><strong class="command">many-answers</strong></span> is more efficient, but is
4507                   only supported by relatively new slave servers,
4508                   such as <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
4509                   8.x and <acronym class="acronym">BIND</acronym> 4.9.5 onwards.
4510                   The <span><strong class="command">many-answers</strong></span> format is also supported by
4511                   recent Microsoft Windows nameservers.
4512                   The default is <span><strong class="command">many-answers</strong></span>.
4513                   <span><strong class="command">transfer-format</strong></span> may be overridden on a
4514                   per-server basis by using the <span><strong class="command">server</strong></span>
4515                   statement.
4516                 </p></dd>
4517 <dt><span class="term"><span><strong class="command">transfers-in</strong></span></span></dt>
4518 <dd><p>
4519                   The maximum number of inbound zone transfers
4520                   that can be running concurrently. The default value is <code class="literal">10</code>.
4521                   Increasing <span><strong class="command">transfers-in</strong></span> may
4522                   speed up the convergence
4523                   of slave zones, but it also may increase the load on the
4524                   local system.
4525                 </p></dd>
4526 <dt><span class="term"><span><strong class="command">transfers-out</strong></span></span></dt>
4527 <dd><p>
4528                   The maximum number of outbound zone transfers
4529                   that can be running concurrently. Zone transfer requests in
4530                   excess
4531                   of the limit will be refused. The default value is <code class="literal">10</code>.
4532                 </p></dd>
4533 <dt><span class="term"><span><strong class="command">transfers-per-ns</strong></span></span></dt>
4534 <dd><p>
4535                   The maximum number of inbound zone transfers
4536                   that can be concurrently transferring from a given remote
4537                   name server.
4538                   The default value is <code class="literal">2</code>.
4539                   Increasing <span><strong class="command">transfers-per-ns</strong></span>
4540                   may
4541                   speed up the convergence of slave zones, but it also may
4542                   increase
4543                   the load on the remote name server. <span><strong class="command">transfers-per-ns</strong></span> may
4544                   be overridden on a per-server basis by using the <span><strong class="command">transfers</strong></span> phrase
4545                   of the <span><strong class="command">server</strong></span> statement.
4546                 </p></dd>
4547 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
4548 <dd>
4549 <p><span><strong class="command">transfer-source</strong></span>
4550                   determines which local address will be bound to IPv4
4551                   TCP connections used to fetch zones transferred
4552                   inbound by the server.  It also determines the
4553                   source IPv4 address, and optionally the UDP port,
4554                   used for the refresh queries and forwarded dynamic
4555                   updates.  If not set, it defaults to a system
4556                   controlled value which will usually be the address
4557                   of the interface "closest to" the remote end. This
4558                   address must appear in the remote end's
4559                   <span><strong class="command">allow-transfer</strong></span> option for the
4560                   zone being transferred, if one is specified. This
4561                   statement sets the
4562                   <span><strong class="command">transfer-source</strong></span> for all zones,
4563                   but can be overridden on a per-view or per-zone
4564                   basis by including a
4565                   <span><strong class="command">transfer-source</strong></span> statement within
4566                   the <span><strong class="command">view</strong></span> or
4567                   <span><strong class="command">zone</strong></span> block in the configuration
4568                   file.
4569                 </p>
4570 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4571 <h3 class="title">Note</h3>
4572 <p>
4573                     Solaris 2.5.1 and earlier does not support setting the
4574                     source address for TCP sockets.
4575                   </p>
4576 </div>
4577 </dd>
4578 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
4579 <dd><p>
4580                   The same as <span><strong class="command">transfer-source</strong></span>,
4581                   except zone transfers are performed using IPv6.
4582                 </p></dd>
4583 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
4584 <dd>
4585 <p>
4586                   An alternate transfer source if the one listed in
4587                   <span><strong class="command">transfer-source</strong></span> fails and
4588                   <span><strong class="command">use-alt-transfer-source</strong></span> is
4589                   set.
4590                 </p>
4591 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4592 <h3 class="title">Note</h3>
4593                   If you do not wish the alternate transfer source
4594                   to be used, you should set
4595                   <span><strong class="command">use-alt-transfer-source</strong></span>
4596                   appropriately and you should not depend upon
4597                   getting an answer back to the first refresh
4598                   query.
4599                 </div>
4600 </dd>
4601 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
4602 <dd><p>
4603                   An alternate transfer source if the one listed in
4604                   <span><strong class="command">transfer-source-v6</strong></span> fails and
4605                   <span><strong class="command">use-alt-transfer-source</strong></span> is
4606                   set.
4607                 </p></dd>
4608 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
4609 <dd><p>
4610                   Use the alternate transfer sources or not.  If views are
4611                   specified this defaults to <span><strong class="command">no</strong></span>
4612                   otherwise it defaults to
4613                   <span><strong class="command">yes</strong></span> (for BIND 8
4614                   compatibility).
4615                 </p></dd>
4616 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
4617 <dd>
4618 <p><span><strong class="command">notify-source</strong></span>
4619                   determines which local source address, and
4620                   optionally UDP port, will be used to send NOTIFY
4621                   messages.  This address must appear in the slave
4622                   server's <span><strong class="command">masters</strong></span> zone clause or
4623                   in an <span><strong class="command">allow-notify</strong></span> clause.  This
4624                   statement sets the <span><strong class="command">notify-source</strong></span>
4625                   for all zones, but can be overridden on a per-zone or
4626                   per-view basis by including a
4627                   <span><strong class="command">notify-source</strong></span> statement within
4628                   the <span><strong class="command">zone</strong></span> or
4629                   <span><strong class="command">view</strong></span> block in the configuration
4630                   file.
4631                 </p>
4632 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4633 <h3 class="title">Note</h3>
4634 <p>
4635                     Solaris 2.5.1 and earlier does not support setting the
4636                     source address for TCP sockets.
4637                   </p>
4638 </div>
4639 </dd>
4640 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
4641 <dd><p>
4642                   Like <span><strong class="command">notify-source</strong></span>,
4643                   but applies to notify messages sent to IPv6 addresses.
4644                 </p></dd>
4645 </dl></div>
4646 </div>
4647 <div class="sect3" lang="en">
4648 <div class="titlepage"><div><div><h4 class="title">
4649 <a name="id2585310"></a>UDP Port Lists</h4></div></div></div>
4650 <p>
4651             <span><strong class="command">use-v4-udp-ports</strong></span>,
4652             <span><strong class="command">avoid-v4-udp-ports</strong></span>,
4653             <span><strong class="command">use-v6-udp-ports</strong></span>, and
4654             <span><strong class="command">avoid-v6-udp-ports</strong></span>
4655             specify a list of IPv4 and IPv6 UDP ports that will be
4656             used or not used as source ports for UDP messages.
4657             See <a href="Bv9ARM.ch06.html#query_address" title="Query Address">the section called &#8220;Query Address&#8221;</a> about how the
4658             available ports are determined.
4659             For example, with the following configuration
4660           </p>
4661 <pre class="programlisting">
4662 use-v6-udp-ports { range 32768 65535; };
4663 avoid-v6-udp-ports { 40000; range 50000 60000; };
4664 </pre>
4665 <p>
4666              UDP ports of IPv6 messages sent
4667              from <span><strong class="command">named</strong></span> will be in one
4668              of the following ranges: 32768 to 39999, 40001 to 49999,
4669              and 60001 to 65535.
4670            </p>
4671 <p>
4672              <span><strong class="command">avoid-v4-udp-ports</strong></span> and
4673              <span><strong class="command">avoid-v6-udp-ports</strong></span> can be used
4674              to prevent <span><strong class="command">named</strong></span> from choosing as its random source port a
4675              port that is blocked by your firewall or a port that is
4676              used by other applications;
4677              if a query went out with a source port blocked by a
4678              firewall, the
4679              answer would not get by the firewall and the name server would
4680              have to query again.
4681              Note: the desired range can also be represented only with
4682              <span><strong class="command">use-v4-udp-ports</strong></span> and
4683              <span><strong class="command">use-v6-udp-ports</strong></span>, and the
4684              <span><strong class="command">avoid-</strong></span> options are redundant in that
4685              sense; they are provided for backward compatibility and
4686              to possibly simplify the port specification.
4687            </p>
4688 </div>
4689 <div class="sect3" lang="en">
4690 <div class="titlepage"><div><div><h4 class="title">
4691 <a name="id2585438"></a>Operating System Resource Limits</h4></div></div></div>
4692 <p>
4693             The server's usage of many system resources can be limited.
4694             Scaled values are allowed when specifying resource limits.  For
4695             example, <span><strong class="command">1G</strong></span> can be used instead of
4696             <span><strong class="command">1073741824</strong></span> to specify a limit of
4697             one
4698             gigabyte. <span><strong class="command">unlimited</strong></span> requests
4699             unlimited use, or the
4700             maximum available amount. <span><strong class="command">default</strong></span>
4701             uses the limit
4702             that was in force when the server was started. See the description
4703             of <span><strong class="command">size_spec</strong></span> in <a href="Bv9ARM.ch06.html#configuration_file_elements" title="Configuration File Elements">the section called &#8220;Configuration File Elements&#8221;</a>.
4704           </p>
4705 <p>
4706             The following options set operating system resource limits for
4707             the name server process.  Some operating systems don't support
4708             some or
4709             any of the limits. On such systems, a warning will be issued if
4710             the
4711             unsupported limit is used.
4712           </p>
4713 <div class="variablelist"><dl>
4714 <dt><span class="term"><span><strong class="command">coresize</strong></span></span></dt>
4715 <dd><p>
4716                   The maximum size of a core dump. The default
4717                   is <code class="literal">default</code>.
4718                 </p></dd>
4719 <dt><span class="term"><span><strong class="command">datasize</strong></span></span></dt>
4720 <dd><p>
4721                   The maximum amount of data memory the server
4722                   may use. The default is <code class="literal">default</code>.
4723                   This is a hard limit on server memory usage.
4724                   If the server attempts to allocate memory in excess of this
4725                   limit, the allocation will fail, which may in turn leave
4726                   the server unable to perform DNS service.  Therefore,
4727                   this option is rarely useful as a way of limiting the
4728                   amount of memory used by the server, but it can be used
4729                   to raise an operating system data size limit that is
4730                   too small by default.  If you wish to limit the amount
4731                   of memory used by the server, use the
4732                   <span><strong class="command">max-cache-size</strong></span> and
4733                   <span><strong class="command">recursive-clients</strong></span>
4734                   options instead.
4735                 </p></dd>
4736 <dt><span class="term"><span><strong class="command">files</strong></span></span></dt>
4737 <dd><p>
4738                   The maximum number of files the server
4739                   may have open concurrently. The default is <code class="literal">unlimited</code>.
4740                 </p></dd>
4741 <dt><span class="term"><span><strong class="command">stacksize</strong></span></span></dt>
4742 <dd><p>
4743                   The maximum amount of stack memory the server
4744                   may use. The default is <code class="literal">default</code>.
4745                 </p></dd>
4746 </dl></div>
4747 </div>
4748 <div class="sect3" lang="en">
4749 <div class="titlepage"><div><div><h4 class="title">
4750 <a name="server_resource_limits"></a>Server  Resource Limits</h4></div></div></div>
4751 <p>
4752             The following options set limits on the server's
4753             resource consumption that are enforced internally by the
4754             server rather than the operating system.
4755           </p>
4756 <div class="variablelist"><dl>
4757 <dt><span class="term"><span><strong class="command">max-ixfr-log-size</strong></span></span></dt>
4758 <dd><p>
4759                   This option is obsolete; it is accepted
4760                   and ignored for BIND 8 compatibility.  The option
4761                   <span><strong class="command">max-journal-size</strong></span> performs a
4762                   similar function in BIND 9.
4763                 </p></dd>
4764 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
4765 <dd><p>
4766                   Sets a maximum size for each journal file
4767                   (see <a href="Bv9ARM.ch04.html#journal" title="The journal file">the section called &#8220;The journal file&#8221;</a>).  When the journal file
4768                   approaches
4769                   the specified size, some of the oldest transactions in the
4770                   journal
4771                   will be automatically removed.  The largest permitted
4772                   value is 2 gigabytes. The default is
4773                   <code class="literal">unlimited</code>, which also
4774                   means 2 gigabytes.
4775                   This may also be set on a per-zone basis.
4776                 </p></dd>
4777 <dt><span class="term"><span><strong class="command">host-statistics-max</strong></span></span></dt>
4778 <dd><p>
4779                   In BIND 8, specifies the maximum number of host statistics
4780                   entries to be kept.
4781                   Not implemented in BIND 9.
4782                 </p></dd>
4783 <dt><span class="term"><span><strong class="command">recursive-clients</strong></span></span></dt>
4784 <dd><p>
4785                   The maximum number of simultaneous recursive lookups
4786                   the server will perform on behalf of clients.  The default
4787                   is
4788                   <code class="literal">1000</code>.  Because each recursing
4789                   client uses a fair
4790                   bit of memory, on the order of 20 kilobytes, the value of
4791                   the
4792                   <span><strong class="command">recursive-clients</strong></span> option may
4793                   have to be decreased
4794                   on hosts with limited memory.
4795                 </p></dd>
4796 <dt><span class="term"><span><strong class="command">tcp-clients</strong></span></span></dt>
4797 <dd><p>
4798                   The maximum number of simultaneous client TCP
4799                   connections that the server will accept.
4800                   The default is <code class="literal">100</code>.
4801                 </p></dd>
4802 <dt><span class="term"><span><strong class="command">reserved-sockets</strong></span></span></dt>
4803 <dd>
4804 <p>
4805                   The number of file descriptors reserved for TCP, stdio,
4806                   etc.  This needs to be big enough to cover the number of
4807                   interfaces <span><strong class="command">named</strong></span> listens on, <span><strong class="command">tcp-clients</strong></span> as well as
4808                   to provide room for outgoing TCP queries and incoming zone
4809                   transfers.  The default is <code class="literal">512</code>.
4810                   The minimum value is <code class="literal">128</code> and the
4811                   maximum value is <code class="literal">128</code> less than
4812                   maxsockets (-S).  This option may be removed in the future.
4813                 </p>
4814 <p>
4815                   This option has little effect on Windows.
4816                 </p>
4817 </dd>
4818 <dt><span class="term"><span><strong class="command">max-cache-size</strong></span></span></dt>
4819 <dd><p>
4820                   The maximum amount of memory to use for the
4821                   server's cache, in bytes.
4822                   When the amount of data in the cache
4823                   reaches this limit, the server will cause records to expire
4824                   prematurely based on an LRU based strategy so that
4825                   the limit is not exceeded.
4826                   A value of 0 is special, meaning that
4827                   records are purged from the cache only when their
4828                   TTLs expire.
4829                   Another special keyword <strong class="userinput"><code>unlimited</code></strong>
4830                   means the maximum value of 32-bit unsigned integers
4831                   (0xffffffff), which may not have the same effect as
4832                   0 on machines that support more than 32 bits of
4833                   memory space.
4834                   Any positive values less than 2MB will be ignored reset
4835                   to 2MB.
4836                   In a server with multiple views, the limit applies
4837                   separately to the cache of each view.
4838                   The default is 0.
4839                 </p></dd>
4840 <dt><span class="term"><span><strong class="command">tcp-listen-queue</strong></span></span></dt>
4841 <dd><p>
4842                   The listen queue depth.  The default and minimum is 10.
4843                   If the kernel supports the accept filter "dataready" this
4844                   also controls how
4845                   many TCP connections that will be queued in kernel space
4846                   waiting for
4847                   some data before being passed to accept.  Nonzero values
4848                   less than 10 will be silently raised. A value of 0 may also
4849                   be used; on most platforms this sets the listen queue
4850                   length to a system-defined default value.
4851                 </p></dd>
4852 </dl></div>
4853 </div>
4854 <div class="sect3" lang="en">
4855 <div class="titlepage"><div><div><h4 class="title">
4856 <a name="id2585861"></a>Periodic Task Intervals</h4></div></div></div>
4857 <div class="variablelist"><dl>
4858 <dt><span class="term"><span><strong class="command">cleaning-interval</strong></span></span></dt>
4859 <dd><p>
4860                   This interval is effectively obsolete.  Previously,
4861                   the server would remove expired resource records
4862                   from the cache every <span><strong class="command">cleaning-interval</strong></span> minutes.
4863                   <acronym class="acronym">BIND</acronym> 9 now manages cache
4864                   memory in a more sophisticated manner and does not
4865                   rely on the periodic cleaning any more.
4866                   Specifying this option therefore has no effect on
4867                   the server's behavior.
4868                 </p></dd>
4869 <dt><span class="term"><span><strong class="command">heartbeat-interval</strong></span></span></dt>
4870 <dd><p>
4871                   The server will perform zone maintenance tasks
4872                   for all zones marked as <span><strong class="command">dialup</strong></span> whenever this
4873                   interval expires. The default is 60 minutes. Reasonable
4874                   values are up
4875                   to 1 day (1440 minutes).  The maximum value is 28 days
4876                   (40320 minutes).
4877                   If set to 0, no zone maintenance for these zones will occur.
4878                 </p></dd>
4879 <dt><span class="term"><span><strong class="command">interface-interval</strong></span></span></dt>
4880 <dd><p>
4881                   The server will scan the network interface list
4882                   every <span><strong class="command">interface-interval</strong></span>
4883                   minutes. The default
4884                   is 60 minutes. The maximum value is 28 days (40320 minutes).
4885                   If set to 0, interface scanning will only occur when
4886                   the configuration file is  loaded. After the scan, the
4887                   server will
4888                   begin listening for queries on any newly discovered
4889                   interfaces (provided they are allowed by the
4890                   <span><strong class="command">listen-on</strong></span> configuration), and
4891                   will
4892                   stop listening on interfaces that have gone away.
4893                 </p></dd>
4894 <dt><span class="term"><span><strong class="command">statistics-interval</strong></span></span></dt>
4895 <dd>
4896 <p>
4897                   Name server statistics will be logged
4898                   every <span><strong class="command">statistics-interval</strong></span>
4899                   minutes. The default is
4900                   60. The maximum value is 28 days (40320 minutes).
4901                   If set to 0, no statistics will be logged.
4902                   </p>
4903 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4904 <h3 class="title">Note</h3>
4905 <p>
4906                     Not yet implemented in
4907                     <acronym class="acronym">BIND</acronym> 9.
4908                   </p>
4909 </div>
4910 </dd>
4911 </dl></div>
4912 </div>
4913 <div class="sect3" lang="en">
4914 <div class="titlepage"><div><div><h4 class="title">
4915 <a name="topology"></a>Topology</h4></div></div></div>
4916 <p>
4917             All other things being equal, when the server chooses a name
4918             server
4919             to query from a list of name servers, it prefers the one that is
4920             topologically closest to itself. The <span><strong class="command">topology</strong></span> statement
4921             takes an <span><strong class="command">address_match_list</strong></span> and
4922             interprets it
4923             in a special way. Each top-level list element is assigned a
4924             distance.
4925             Non-negated elements get a distance based on their position in the
4926             list, where the closer the match is to the start of the list, the
4927             shorter the distance is between it and the server. A negated match
4928             will be assigned the maximum distance from the server. If there
4929             is no match, the address will get a distance which is further than
4930             any non-negated list element, and closer than any negated element.
4931             For example,
4932           </p>
4933 <pre class="programlisting">topology {
4934     10/8;
4935     !1.2.3/24;
4936     { 1.2/16; 3/8; };
4937 };</pre>
4938 <p>
4939             will prefer servers on network 10 the most, followed by hosts
4940             on network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the
4941             exception of hosts on network 1.2.3 (netmask 255.255.255.0), which
4942             is preferred least of all.
4943           </p>
4944 <p>
4945             The default topology is
4946           </p>
4947 <pre class="programlisting">    topology { localhost; localnets; };
4948 </pre>
4949 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4950 <h3 class="title">Note</h3>
4951 <p>
4952               The <span><strong class="command">topology</strong></span> option
4953               is not implemented in <acronym class="acronym">BIND</acronym> 9.
4954             </p>
4955 </div>
4956 </div>
4957 <div class="sect3" lang="en">
4958 <div class="titlepage"><div><div><h4 class="title">
4959 <a name="the_sortlist_statement"></a>The <span><strong class="command">sortlist</strong></span> Statement</h4></div></div></div>
4960 <p>
4961             The response to a DNS query may consist of multiple resource
4962             records (RRs) forming a resource records set (RRset).
4963             The name server will normally return the
4964             RRs within the RRset in an indeterminate order
4965             (but see the <span><strong class="command">rrset-order</strong></span>
4966             statement in <a href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">the section called &#8220;RRset Ordering&#8221;</a>).
4967             The client resolver code should rearrange the RRs as appropriate,
4968             that is, using any addresses on the local net in preference to
4969             other addresses.
4970             However, not all resolvers can do this or are correctly
4971             configured.
4972             When a client is using a local server, the sorting can be performed
4973             in the server, based on the client's address. This only requires
4974             configuring the name servers, not all the clients.
4975           </p>
4976 <p>
4977             The <span><strong class="command">sortlist</strong></span> statement (see below)
4978             takes
4979             an <span><strong class="command">address_match_list</strong></span> and
4980             interprets it even
4981             more specifically than the <span><strong class="command">topology</strong></span>
4982             statement
4983             does (<a href="Bv9ARM.ch06.html#topology" title="Topology">the section called &#8220;Topology&#8221;</a>).
4984             Each top level statement in the <span><strong class="command">sortlist</strong></span> must
4985             itself be an explicit <span><strong class="command">address_match_list</strong></span> with
4986             one or two elements. The first element (which may be an IP
4987             address,
4988             an IP prefix, an ACL name or a nested <span><strong class="command">address_match_list</strong></span>)
4989             of each top level list is checked against the source address of
4990             the query until a match is found.
4991           </p>
4992 <p>
4993             Once the source address of the query has been matched, if
4994             the top level statement contains only one element, the actual
4995             primitive
4996             element that matched the source address is used to select the
4997             address
4998             in the response to move to the beginning of the response. If the
4999             statement is a list of two elements, then the second element is
5000             treated the same as the <span><strong class="command">address_match_list</strong></span> in
5001             a <span><strong class="command">topology</strong></span> statement. Each top
5002             level element
5003             is assigned a distance and the address in the response with the
5004             minimum
5005             distance is moved to the beginning of the response.
5006           </p>
5007 <p>
5008             In the following example, any queries received from any of
5009             the addresses of the host itself will get responses preferring
5010             addresses
5011             on any of the locally connected networks. Next most preferred are
5012             addresses
5013             on the 192.168.1/24 network, and after that either the
5014             192.168.2/24
5015             or
5016             192.168.3/24 network with no preference shown between these two
5017             networks. Queries received from a host on the 192.168.1/24 network
5018             will prefer other addresses on that network to the 192.168.2/24
5019             and
5020             192.168.3/24 networks. Queries received from a host on the
5021             192.168.4/24
5022             or the 192.168.5/24 network will only prefer other addresses on
5023             their directly connected networks.
5024           </p>
5025 <pre class="programlisting">sortlist {
5026     // IF the local host
5027     // THEN first fit on the following nets
5028     { localhost;
5029         { localnets;
5030             192.168.1/24;
5031             { 192.168.2/24; 192.168.3/24; }; }; };
5032     // IF on class C 192.168.1 THEN use .1, or .2 or .3
5033     { 192.168.1/24;
5034         { 192.168.1/24;
5035             { 192.168.2/24; 192.168.3/24; }; }; };
5036     // IF on class C 192.168.2 THEN use .2, or .1 or .3
5037     { 192.168.2/24;
5038         { 192.168.2/24;
5039             { 192.168.1/24; 192.168.3/24; }; }; };
5040     // IF on class C 192.168.3 THEN use .3, or .1 or .2
5041     { 192.168.3/24;
5042         { 192.168.3/24;
5043             { 192.168.1/24; 192.168.2/24; }; }; };
5044     // IF .4 or .5 THEN prefer that net
5045     { { 192.168.4/24; 192.168.5/24; };
5046     };
5047 };</pre>
5048 <p>
5049             The following example will give reasonable behavior for the
5050             local host and hosts on directly connected networks. It is similar
5051             to the behavior of the address sort in <acronym class="acronym">BIND</acronym> 4.9.x. Responses sent
5052             to queries from the local host will favor any of the directly
5053             connected
5054             networks. Responses sent to queries from any other hosts on a
5055             directly
5056             connected network will prefer addresses on that same network.
5057             Responses
5058             to other queries will not be sorted.
5059           </p>
5060 <pre class="programlisting">sortlist {
5061            { localhost; localnets; };
5062            { localnets; };
5063 };
5064 </pre>
5065 </div>
5066 <div class="sect3" lang="en">
5067 <div class="titlepage"><div><div><h4 class="title">
5068 <a name="rrset_ordering"></a>RRset Ordering</h4></div></div></div>
5069 <p>
5070             When multiple records are returned in an answer it may be
5071             useful to configure the order of the records placed into the
5072             response.
5073             The <span><strong class="command">rrset-order</strong></span> statement permits
5074             configuration
5075             of the ordering of the records in a multiple record response.
5076             See also the <span><strong class="command">sortlist</strong></span> statement,
5077             <a href="Bv9ARM.ch06.html#the_sortlist_statement" title="The sortlist Statement">the section called &#8220;The <span><strong class="command">sortlist</strong></span> Statement&#8221;</a>.
5078           </p>
5079 <p>
5080             An <span><strong class="command">order_spec</strong></span> is defined as
5081             follows:
5082           </p>
5083 <p>
5084             [<span class="optional">class <em class="replaceable"><code>class_name</code></em></span>]
5085             [<span class="optional">type <em class="replaceable"><code>type_name</code></em></span>]
5086             [<span class="optional">name <em class="replaceable"><code>"domain_name"</code></em></span>]
5087             order <em class="replaceable"><code>ordering</code></em>
5088           </p>
5089 <p>
5090             If no class is specified, the default is <span><strong class="command">ANY</strong></span>.
5091             If no type is specified, the default is <span><strong class="command">ANY</strong></span>.
5092             If no name is specified, the default is "<span><strong class="command">*</strong></span>" (asterisk).
5093           </p>
5094 <p>
5095             The legal values for <span><strong class="command">ordering</strong></span> are:
5096           </p>
5097 <div class="informaltable"><table border="1">
5098 <colgroup>
5099 <col>
5100 <col>
5101 </colgroup>
5102 <tbody>
5103 <tr>
5104 <td>
5105                     <p><span><strong class="command">fixed</strong></span></p>
5106                   </td>
5107 <td>
5108                     <p>
5109                       Records are returned in the order they
5110                       are defined in the zone file.
5111                     </p>
5112                   </td>
5113 </tr>
5114 <tr>
5115 <td>
5116                     <p><span><strong class="command">random</strong></span></p>
5117                   </td>
5118 <td>
5119                     <p>
5120                       Records are returned in some random order.
5121                     </p>
5122                   </td>
5123 </tr>
5124 <tr>
5125 <td>
5126                     <p><span><strong class="command">cyclic</strong></span></p>
5127                   </td>
5128 <td>
5129                     <p>
5130                       Records are returned in a cyclic round-robin order.
5131                     </p>
5132                     <p>
5133                       If <acronym class="acronym">BIND</acronym> is configured with the
5134                       "--enable-fixed-rrset" option at compile time, then
5135                       the initial ordering of the RRset will match the
5136                       one specified in the zone file.
5137                     </p>
5138                   </td>
5139 </tr>
5140 </tbody>
5141 </table></div>
5142 <p>
5143             For example:
5144           </p>
5145 <pre class="programlisting">rrset-order {
5146    class IN type A name "host.example.com" order random;
5147    order cyclic;
5148 };
5149 </pre>
5150 <p>
5151             will cause any responses for type A records in class IN that
5152             have "<code class="literal">host.example.com</code>" as a
5153             suffix, to always be returned
5154             in random order. All other records are returned in cyclic order.
5155           </p>
5156 <p>
5157             If multiple <span><strong class="command">rrset-order</strong></span> statements
5158             appear, they are not combined &#8212; the last one applies.
5159           </p>
5160 <p>
5161             By default, all records are returned in random order.
5162           </p>
5163 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5164 <h3 class="title">Note</h3>
5165 <p>
5166               In this release of <acronym class="acronym">BIND</acronym> 9, the
5167               <span><strong class="command">rrset-order</strong></span> statement does not support
5168               "fixed" ordering by default.  Fixed ordering can be enabled
5169               at compile time by specifying "--enable-fixed-rrset" on
5170               the "configure" command line.
5171             </p>
5172 </div>
5173 </div>
5174 <div class="sect3" lang="en">
5175 <div class="titlepage"><div><div><h4 class="title">
5176 <a name="tuning"></a>Tuning</h4></div></div></div>
5177 <div class="variablelist"><dl>
5178 <dt><span class="term"><span><strong class="command">lame-ttl</strong></span></span></dt>
5179 <dd>
5180 <p>
5181                   Sets the number of seconds to cache a
5182                   lame server indication. 0 disables caching. (This is
5183                   <span class="bold"><strong>NOT</strong></span> recommended.)
5184                   The default is <code class="literal">600</code> (10 minutes) and the
5185                   maximum value is
5186                   <code class="literal">1800</code> (30 minutes).
5187                 </p>
5188 <p>
5189                   Lame-ttl also controls the amount of time DNSSEC
5190                   validation failures are cached.  There is a minimum
5191                   of 30 seconds applied to bad cache entries if the
5192                   lame-ttl is set to less than 30 seconds.
5193                 </p>
5194 </dd>
5195 <dt><span class="term"><span><strong class="command">max-ncache-ttl</strong></span></span></dt>
5196 <dd><p>
5197                   To reduce network traffic and increase performance,
5198                   the server stores negative answers. <span><strong class="command">max-ncache-ttl</strong></span> is
5199                   used to set a maximum retention time for these answers in
5200                   the server
5201                   in seconds. The default
5202                   <span><strong class="command">max-ncache-ttl</strong></span> is <code class="literal">10800</code> seconds (3 hours).
5203                   <span><strong class="command">max-ncache-ttl</strong></span> cannot exceed
5204                   7 days and will
5205                   be silently truncated to 7 days if set to a greater value.
5206                 </p></dd>
5207 <dt><span class="term"><span><strong class="command">max-cache-ttl</strong></span></span></dt>
5208 <dd><p>
5209                   Sets the maximum time for which the server will
5210                   cache ordinary (positive) answers. The default is
5211                   one week (7 days).
5212                   A value of zero may cause all queries to return
5213                   SERVFAIL, because of lost caches of intermediate
5214                   RRsets (such as NS and glue AAAA/A records) in the
5215                   resolution process.
5216                 </p></dd>
5217 <dt><span class="term"><span><strong class="command">min-roots</strong></span></span></dt>
5218 <dd>
5219 <p>
5220                   The minimum number of root servers that
5221                   is required for a request for the root servers to be
5222                   accepted. The default
5223                   is <strong class="userinput"><code>2</code></strong>.
5224                 </p>
5225 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5226 <h3 class="title">Note</h3>
5227 <p>
5228                     Not implemented in <acronym class="acronym">BIND</acronym> 9.
5229                   </p>
5230 </div>
5231 </dd>
5232 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
5233 <dd>
5234 <p>
5235                   Specifies the number of days into the future when
5236                   DNSSEC signatures automatically generated as a
5237                   result of dynamic updates (<a href="Bv9ARM.ch04.html#dynamic_update" title="Dynamic Update">the section called &#8220;Dynamic Update&#8221;</a>) will expire.  There
5238                   is an optional second field which specifies how
5239                   long before expiry that the signatures will be
5240                   regenerated.  If not specified, the signatures will
5241                   be regenerated at 1/4 of base interval.  The second
5242                   field is specified in days if the base interval is
5243                   greater than 7 days otherwise it is specified in hours.
5244                   The default base interval is <code class="literal">30</code> days
5245                   giving a re-signing interval of 7 1/2 days.  The maximum
5246                   values are 10 years (3660 days).
5247                 </p>
5248 <p>
5249                   The signature inception time is unconditionally
5250                   set to one hour before the current time to allow
5251                   for a limited amount of clock skew.
5252                 </p>
5253 <p>
5254                   The <span><strong class="command">sig-validity-interval</strong></span>
5255                   should be, at least, several multiples of the SOA
5256                   expire interval to allow for reasonable interaction
5257                   between the various timer and expiry dates.
5258                 </p>
5259 </dd>
5260 <dt><span class="term"><span><strong class="command">sig-signing-nodes</strong></span></span></dt>
5261 <dd><p>
5262                   Specify the maximum number of nodes to be
5263                   examined in each quantum when signing a zone with
5264                   a new DNSKEY. The default is
5265                   <code class="literal">100</code>.
5266                 </p></dd>
5267 <dt><span class="term"><span><strong class="command">sig-signing-signatures</strong></span></span></dt>
5268 <dd><p>
5269                   Specify a threshold number of signatures that
5270                   will terminate processing a quantum when signing
5271                   a zone with a new DNSKEY.  The default is
5272                   <code class="literal">10</code>.
5273                 </p></dd>
5274 <dt><span class="term"><span><strong class="command">sig-signing-type</strong></span></span></dt>
5275 <dd>
5276 <p>
5277                   Specify a private RDATA type to be used when generating
5278                   signing state records.  The default is
5279                   <code class="literal">65534</code>.
5280                 </p>
5281 <p>
5282                   It is expected that this parameter may be removed
5283                   in a future version once there is a standard type.
5284                 </p>
5285 <p>
5286                   Signing state records are used to internally by
5287                   <span><strong class="command">named</strong></span> to track the current state of
5288                   a zone-signing process, i.e., whether it is still active
5289                   or has been completed.  The records can be inspected
5290                   using the command
5291                   <span><strong class="command">rndc signing -list <em class="replaceable"><code>zone</code></em></strong></span>.
5292                   Once <span><strong class="command">named</strong></span> has finished signing
5293                   a zone with a particular key, the signing state
5294                   record associated with that key can be removed from
5295                   the zone by running
5296                   <span><strong class="command">rndc signing -clear <em class="replaceable"><code>keyid/algorithm</code></em> <em class="replaceable"><code>zone</code></em></strong></span>.
5297                   To clear all of the completed signing state
5298                   records for a zone, use
5299                   <span><strong class="command">rndc signing -clear all <em class="replaceable"><code>zone</code></em></strong></span>.
5300                 </p>
5301 </dd>
5302 <dt>
5303 <span class="term"><span><strong class="command">min-refresh-time</strong></span>, </span><span class="term"><span><strong class="command">max-refresh-time</strong></span>, </span><span class="term"><span><strong class="command">min-retry-time</strong></span>, </span><span class="term"><span><strong class="command">max-retry-time</strong></span></span>
5304 </dt>
5305 <dd>
5306 <p>
5307                   These options control the server's behavior on refreshing a
5308                   zone
5309                   (querying for SOA changes) or retrying failed transfers.
5310                   Usually the SOA values for the zone are used, but these
5311                   values
5312                   are set by the master, giving slave server administrators
5313                   little
5314                   control over their contents.
5315                 </p>
5316 <p>
5317                   These options allow the administrator to set a minimum and
5318                   maximum
5319                   refresh and retry time either per-zone, per-view, or
5320                   globally.
5321                   These options are valid for slave and stub zones,
5322                   and clamp the SOA refresh and retry times to the specified
5323                   values.
5324                 </p>
5325 <p>
5326                   The following defaults apply.
5327                   <span><strong class="command">min-refresh-time</strong></span> 300 seconds,
5328                   <span><strong class="command">max-refresh-time</strong></span> 2419200 seconds
5329                   (4 weeks), <span><strong class="command">min-retry-time</strong></span> 500 seconds,
5330                   and <span><strong class="command">max-retry-time</strong></span> 1209600 seconds
5331                   (2 weeks).
5332                 </p>
5333 </dd>
5334 <dt><span class="term"><span><strong class="command">edns-udp-size</strong></span></span></dt>
5335 <dd>
5336 <p>
5337                   Sets the advertised EDNS UDP buffer size in bytes
5338                   to control the size of packets received.
5339                   Valid values are 512 to 4096 (values outside this range
5340                   will be silently adjusted).  The default value
5341                   is 4096.  The usual reason for setting
5342                   <span><strong class="command">edns-udp-size</strong></span> to a non-default
5343                   value is to get UDP answers to pass through broken
5344                   firewalls that block fragmented packets and/or
5345                   block UDP packets that are greater than 512 bytes.
5346                 </p>
5347 <p>
5348                   <span><strong class="command">named</strong></span> will fallback to using 512 bytes
5349                   if it get a series of timeout at the initial value.  512
5350                   bytes is not being offered to encourage sites to fix their
5351                   firewalls.  Small EDNS UDP sizes will result in the
5352                   excessive use of TCP.
5353                 </p>
5354 </dd>
5355 <dt><span class="term"><span><strong class="command">max-udp-size</strong></span></span></dt>
5356 <dd>
5357 <p>
5358                   Sets the maximum EDNS UDP message size
5359                   <span><strong class="command">named</strong></span> will send in bytes.
5360                   Valid values are 512 to 4096 (values outside this
5361                   range will be silently adjusted).  The default
5362                   value is 4096.  The usual reason for setting
5363                   <span><strong class="command">max-udp-size</strong></span> to a non-default
5364                   value is to get UDP answers to pass through broken
5365                   firewalls that block fragmented packets and/or
5366                   block UDP packets that are greater than 512 bytes.
5367                   This is independent of the advertised receive
5368                   buffer (<span><strong class="command">edns-udp-size</strong></span>).
5369                 </p>
5370 <p>
5371                   Setting this to a low value will encourage additional
5372                   TCP traffic to the nameserver.
5373                 </p>
5374 </dd>
5375 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
5376 <dd>
5377 <p>Specifies
5378                   the file format of zone files (see
5379                   <a href="Bv9ARM.ch06.html#zonefile_format" title="Additional File Formats">the section called &#8220;Additional File Formats&#8221;</a>).
5380                   The default value is <code class="constant">text</code>, which is the
5381                   standard textual representation, except for slave zones,
5382                   in which the default value is <code class="constant">raw</code>.
5383                   Files in other formats than <code class="constant">text</code> are
5384                   typically expected to be generated by the
5385                   <span><strong class="command">named-compilezone</strong></span> tool, or dumped by
5386                   <span><strong class="command">named</strong></span>.
5387                 </p>
5388 <p>
5389                   Note that when a zone file in a different format than
5390                   <code class="constant">text</code> is loaded, <span><strong class="command">named</strong></span>
5391                   may omit some of the checks which would be performed for a
5392                   file in the <code class="constant">text</code> format.  In particular,
5393                   <span><strong class="command">check-names</strong></span> checks do not apply
5394                   for the <code class="constant">raw</code> format.  This means
5395                   a zone file in the <code class="constant">raw</code> format
5396                   must be generated with the same check level as that
5397                   specified in the <span><strong class="command">named</strong></span> configuration
5398                   file.  This statement sets the
5399                   <span><strong class="command">masterfile-format</strong></span> for all zones,
5400                   but can be overridden on a per-zone or per-view basis
5401                   by including a <span><strong class="command">masterfile-format</strong></span>
5402                   statement within the <span><strong class="command">zone</strong></span> or
5403                   <span><strong class="command">view</strong></span> block in the configuration
5404                   file.
5405                 </p>
5406 </dd>
5407 <dt>
5408 <a name="clients-per-query"></a><span class="term"><span><strong class="command">clients-per-query</strong></span>, </span><span class="term"><span><strong class="command">max-clients-per-query</strong></span></span>
5409 </dt>
5410 <dd>
5411 <p>These set the
5412                   initial value (minimum) and maximum number of recursive
5413                   simultaneous clients for any given query
5414                   (&lt;qname,qtype,qclass&gt;) that the server will accept
5415                   before dropping additional clients.  <span><strong class="command">named</strong></span> will attempt to
5416                   self tune this value and changes will be logged.  The
5417                   default values are 10 and 100.
5418                 </p>
5419 <p>
5420                   This value should reflect how many queries come in for
5421                   a given name in the time it takes to resolve that name.
5422                   If the number of queries exceed this value, <span><strong class="command">named</strong></span> will
5423                   assume that it is dealing with a non-responsive zone
5424                   and will drop additional queries.  If it gets a response
5425                   after dropping queries, it will raise the estimate.  The
5426                   estimate will then be lowered in 20 minutes if it has
5427                   remained unchanged.
5428                 </p>
5429 <p>
5430                   If <span><strong class="command">clients-per-query</strong></span> is set to zero,
5431                   then there is no limit on the number of clients per query
5432                   and no queries will be dropped.
5433                 </p>
5434 <p>
5435                   If <span><strong class="command">max-clients-per-query</strong></span> is set to zero,
5436                   then there is no upper bound other than imposed by
5437                   <span><strong class="command">recursive-clients</strong></span>.
5438                 </p>
5439 </dd>
5440 <dt>
5441 <a name="max-recursion-depth"></a><span class="term"><span><strong class="command">max-recursion-depth</strong></span></span>
5442 </dt>
5443 <dd><p>
5444                   Sets the maximum number of levels of recursion
5445                   that are permitted at any one time while servicing
5446                   a recursive query. Resolving a name may require
5447                   looking up a name server address, which in turn
5448                   requires resolving another name, etc; if the number
5449                   of indirections exceeds this value, the recursive
5450                   query is terminated and returns SERVFAIL.  The
5451                   default is 7.
5452                 </p></dd>
5453 <dt>
5454 <a name="max-recursion-queries"></a><span class="term"><span><strong class="command">max-recursion-queries</strong></span></span>
5455 </dt>
5456 <dd><p>
5457                   Sets the maximum number of iterative queries that
5458                   may be sent while servicing a recursive query.
5459                   If more queries are sent, the recursive query
5460                   is terminated and returns SERVFAIL. The default
5461                   is 50.
5462                 </p></dd>
5463 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
5464 <dd>
5465 <p>
5466                   The delay, in seconds, between sending sets of notify
5467                   messages for a zone.  The default is five (5) seconds.
5468                 </p>
5469 <p>
5470                   The overall rate that NOTIFY messages are sent for all
5471                   zones is controlled by <span><strong class="command">serial-query-rate</strong></span>.
5472                 </p>
5473 </dd>
5474 <dt><span class="term"><span><strong class="command">max-rsa-exponent-size</strong></span></span></dt>
5475 <dd><p>
5476                   The maximum RSA exponent size, in bits, that will
5477                   be accepted when validating.  Valid values are 35
5478                   to 4096 bits.  The default zero (0) is also accepted
5479                   and is equivalent to 4096.
5480                 </p></dd>
5481 </dl></div>
5482 </div>
5483 <div class="sect3" lang="en">
5484 <div class="titlepage"><div><div><h4 class="title">
5485 <a name="builtin"></a>Built-in server information zones</h4></div></div></div>
5486 <p>
5487             The server provides some helpful diagnostic information
5488             through a number of built-in zones under the
5489             pseudo-top-level-domain <code class="literal">bind</code> in the
5490             <span><strong class="command">CHAOS</strong></span> class.  These zones are part
5491             of a
5492             built-in view (see <a href="Bv9ARM.ch06.html#view_statement_grammar" title="view Statement Grammar">the section called &#8220;<span><strong class="command">view</strong></span> Statement Grammar&#8221;</a>) of
5493             class
5494             <span><strong class="command">CHAOS</strong></span> which is separate from the
5495             default view of class <span><strong class="command">IN</strong></span>. Most global
5496             configuration options (<span><strong class="command">allow-query</strong></span>,
5497             etc) will apply to this view, but some are locally
5498             overridden: <span><strong class="command">notify</strong></span>,
5499             <span><strong class="command">recursion</strong></span> and
5500             <span><strong class="command">allow-new-zones</strong></span> are
5501             always set to <strong class="userinput"><code>no</code></strong>.
5502           </p>
5503 <p>
5504             If you need to disable these zones, use the options
5505             below, or hide the built-in <span><strong class="command">CHAOS</strong></span>
5506             view by
5507             defining an explicit view of class <span><strong class="command">CHAOS</strong></span>
5508             that matches all clients.
5509           </p>
5510 <div class="variablelist"><dl>
5511 <dt><span class="term"><span><strong class="command">version</strong></span></span></dt>
5512 <dd><p>
5513                   The version the server should report
5514                   via a query of the name <code class="literal">version.bind</code>
5515                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5516                   The default is the real version number of this server.
5517                   Specifying <span><strong class="command">version none</strong></span>
5518                   disables processing of the queries.
5519                 </p></dd>
5520 <dt><span class="term"><span><strong class="command">hostname</strong></span></span></dt>
5521 <dd><p>
5522                   The hostname the server should report via a query of
5523                   the name <code class="filename">hostname.bind</code>
5524                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5525                   This defaults to the hostname of the machine hosting the
5526                   name server as
5527                   found by the gethostname() function.  The primary purpose of such queries
5528                   is to
5529                   identify which of a group of anycast servers is actually
5530                   answering your queries.  Specifying <span><strong class="command">hostname none;</strong></span>
5531                   disables processing of the queries.
5532                 </p></dd>
5533 <dt><span class="term"><span><strong class="command">server-id</strong></span></span></dt>
5534 <dd><p>
5535                   The ID the server should report when receiving a Name
5536                   Server Identifier (NSID) query, or a query of the name
5537                   <code class="filename">ID.SERVER</code> with type
5538                   <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5539                   The primary purpose of such queries is to
5540                   identify which of a group of anycast servers is actually
5541                   answering your queries.  Specifying <span><strong class="command">server-id none;</strong></span>
5542                   disables processing of the queries.
5543                   Specifying <span><strong class="command">server-id hostname;</strong></span> will cause <span><strong class="command">named</strong></span> to
5544                   use the hostname as found by the gethostname() function.
5545                   The default <span><strong class="command">server-id</strong></span> is <span><strong class="command">none</strong></span>.
5546                 </p></dd>
5547 </dl></div>
5548 </div>
5549 <div class="sect3" lang="en">
5550 <div class="titlepage"><div><div><h4 class="title">
5551 <a name="empty"></a>Built-in Empty Zones</h4></div></div></div>
5552 <p>
5553             Named has some built-in empty zones (SOA and NS records only).
5554             These are for zones that should normally be answered locally
5555             and which queries should not be sent to the Internet's root
5556             servers.  The official servers which cover these namespaces
5557             return NXDOMAIN responses to these queries.  In particular,
5558             these cover the reverse namespaces for addresses from
5559             RFC 1918, RFC 4193, RFC 5737 and RFC 6598.  They also include the
5560             reverse namespace for IPv6 local address (locally assigned),
5561             IPv6 link local addresses, the IPv6 loopback address and the
5562             IPv6 unknown address.
5563           </p>
5564 <p>
5565             Named will attempt to determine if a built-in zone already exists
5566             or is active (covered by a forward-only forwarding declaration)
5567             and will not create an empty zone in that case.
5568           </p>
5569 <p>
5570             The current list of empty zones is:
5571             </p>
5572 <div class="itemizedlist"><ul type="disc">
5573 <li>10.IN-ADDR.ARPA</li>
5574 <li>16.172.IN-ADDR.ARPA</li>
5575 <li>17.172.IN-ADDR.ARPA</li>
5576 <li>18.172.IN-ADDR.ARPA</li>
5577 <li>19.172.IN-ADDR.ARPA</li>
5578 <li>20.172.IN-ADDR.ARPA</li>
5579 <li>21.172.IN-ADDR.ARPA</li>
5580 <li>22.172.IN-ADDR.ARPA</li>
5581 <li>23.172.IN-ADDR.ARPA</li>
5582 <li>24.172.IN-ADDR.ARPA</li>
5583 <li>25.172.IN-ADDR.ARPA</li>
5584 <li>26.172.IN-ADDR.ARPA</li>
5585 <li>27.172.IN-ADDR.ARPA</li>
5586 <li>28.172.IN-ADDR.ARPA</li>
5587 <li>29.172.IN-ADDR.ARPA</li>
5588 <li>30.172.IN-ADDR.ARPA</li>
5589 <li>31.172.IN-ADDR.ARPA</li>
5590 <li>168.192.IN-ADDR.ARPA</li>
5591 <li>64.100.IN-ADDR.ARPA</li>
5592 <li>65.100.IN-ADDR.ARPA</li>
5593 <li>66.100.IN-ADDR.ARPA</li>
5594 <li>67.100.IN-ADDR.ARPA</li>
5595 <li>68.100.IN-ADDR.ARPA</li>
5596 <li>69.100.IN-ADDR.ARPA</li>
5597 <li>70.100.IN-ADDR.ARPA</li>
5598 <li>71.100.IN-ADDR.ARPA</li>
5599 <li>72.100.IN-ADDR.ARPA</li>
5600 <li>73.100.IN-ADDR.ARPA</li>
5601 <li>74.100.IN-ADDR.ARPA</li>
5602 <li>75.100.IN-ADDR.ARPA</li>
5603 <li>76.100.IN-ADDR.ARPA</li>
5604 <li>77.100.IN-ADDR.ARPA</li>
5605 <li>78.100.IN-ADDR.ARPA</li>
5606 <li>79.100.IN-ADDR.ARPA</li>
5607 <li>80.100.IN-ADDR.ARPA</li>
5608 <li>81.100.IN-ADDR.ARPA</li>
5609 <li>82.100.IN-ADDR.ARPA</li>
5610 <li>83.100.IN-ADDR.ARPA</li>
5611 <li>84.100.IN-ADDR.ARPA</li>
5612 <li>85.100.IN-ADDR.ARPA</li>
5613 <li>86.100.IN-ADDR.ARPA</li>
5614 <li>87.100.IN-ADDR.ARPA</li>
5615 <li>88.100.IN-ADDR.ARPA</li>
5616 <li>89.100.IN-ADDR.ARPA</li>
5617 <li>90.100.IN-ADDR.ARPA</li>
5618 <li>91.100.IN-ADDR.ARPA</li>
5619 <li>92.100.IN-ADDR.ARPA</li>
5620 <li>93.100.IN-ADDR.ARPA</li>
5621 <li>94.100.IN-ADDR.ARPA</li>
5622 <li>95.100.IN-ADDR.ARPA</li>
5623 <li>96.100.IN-ADDR.ARPA</li>
5624 <li>97.100.IN-ADDR.ARPA</li>
5625 <li>98.100.IN-ADDR.ARPA</li>
5626 <li>99.100.IN-ADDR.ARPA</li>
5627 <li>100.100.IN-ADDR.ARPA</li>
5628 <li>101.100.IN-ADDR.ARPA</li>
5629 <li>102.100.IN-ADDR.ARPA</li>
5630 <li>103.100.IN-ADDR.ARPA</li>
5631 <li>104.100.IN-ADDR.ARPA</li>
5632 <li>105.100.IN-ADDR.ARPA</li>
5633 <li>106.100.IN-ADDR.ARPA</li>
5634 <li>107.100.IN-ADDR.ARPA</li>
5635 <li>108.100.IN-ADDR.ARPA</li>
5636 <li>109.100.IN-ADDR.ARPA</li>
5637 <li>110.100.IN-ADDR.ARPA</li>
5638 <li>111.100.IN-ADDR.ARPA</li>
5639 <li>112.100.IN-ADDR.ARPA</li>
5640 <li>113.100.IN-ADDR.ARPA</li>
5641 <li>114.100.IN-ADDR.ARPA</li>
5642 <li>115.100.IN-ADDR.ARPA</li>
5643 <li>116.100.IN-ADDR.ARPA</li>
5644 <li>117.100.IN-ADDR.ARPA</li>
5645 <li>118.100.IN-ADDR.ARPA</li>
5646 <li>119.100.IN-ADDR.ARPA</li>
5647 <li>120.100.IN-ADDR.ARPA</li>
5648 <li>121.100.IN-ADDR.ARPA</li>
5649 <li>122.100.IN-ADDR.ARPA</li>
5650 <li>123.100.IN-ADDR.ARPA</li>
5651 <li>124.100.IN-ADDR.ARPA</li>
5652 <li>125.100.IN-ADDR.ARPA</li>
5653 <li>126.100.IN-ADDR.ARPA</li>
5654 <li>127.100.IN-ADDR.ARPA</li>
5655 <li>0.IN-ADDR.ARPA</li>
5656 <li>127.IN-ADDR.ARPA</li>
5657 <li>254.169.IN-ADDR.ARPA</li>
5658 <li>2.0.192.IN-ADDR.ARPA</li>
5659 <li>100.51.198.IN-ADDR.ARPA</li>
5660 <li>113.0.203.IN-ADDR.ARPA</li>
5661 <li>255.255.255.255.IN-ADDR.ARPA</li>
5662 <li>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>
5663 <li>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>
5664 <li>8.B.D.0.1.0.0.2.IP6.ARPA</li>
5665 <li>D.F.IP6.ARPA</li>
5666 <li>8.E.F.IP6.ARPA</li>
5667 <li>9.E.F.IP6.ARPA</li>
5668 <li>A.E.F.IP6.ARPA</li>
5669 <li>B.E.F.IP6.ARPA</li>
5670 </ul></div>
5671 <p>
5672           </p>
5673 <p>
5674             Empty zones are settable at the view level and only apply to
5675             views of class IN.  Disabled empty zones are only inherited
5676             from options if there are no disabled empty zones specified
5677             at the view level.  To override the options list of disabled
5678             zones, you can disable the root zone at the view level, for example:
5679 </p>
5680 <pre class="programlisting">
5681             disable-empty-zone ".";
5682 </pre>
5683 <p>
5684           </p>
5685 <p>
5686             If you are using the address ranges covered here, you should
5687             already have reverse zones covering the addresses you use.
5688             In practice this appears to not be the case with many queries
5689             being made to the infrastructure servers for names in these
5690             spaces.  So many in fact that sacrificial servers were needed
5691             to be deployed to channel the query load away from the
5692             infrastructure servers.
5693           </p>
5694 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5695 <h3 class="title">Note</h3>
5696             The real parent servers for these zones should disable all
5697             empty zone under the parent zone they serve.  For the real
5698             root servers, this is all built-in empty zones.  This will
5699             enable them to return referrals to deeper in the tree.
5700           </div>
5701 <div class="variablelist"><dl>
5702 <dt><span class="term"><span><strong class="command">empty-server</strong></span></span></dt>
5703 <dd><p>
5704                   Specify what server name will appear in the returned
5705                   SOA record for empty zones.  If none is specified, then
5706                   the zone's name will be used.
5707                 </p></dd>
5708 <dt><span class="term"><span><strong class="command">empty-contact</strong></span></span></dt>
5709 <dd><p>
5710                   Specify what contact name will appear in the returned
5711                   SOA record for empty zones.  If none is specified, then
5712                   "." will be used.
5713                 </p></dd>
5714 <dt><span class="term"><span><strong class="command">empty-zones-enable</strong></span></span></dt>
5715 <dd><p>
5716                   Enable or disable all empty zones.  By default, they
5717                   are enabled.
5718                 </p></dd>
5719 <dt><span class="term"><span><strong class="command">disable-empty-zone</strong></span></span></dt>
5720 <dd><p>
5721                   Disable individual empty zones.  By default, none are
5722                   disabled.  This option can be specified multiple times.
5723                 </p></dd>
5724 </dl></div>
5725 </div>
5726 <div class="sect3" lang="en">
5727 <div class="titlepage"><div><div><h4 class="title">
5728 <a name="acache"></a>Additional Section Caching</h4></div></div></div>
5729 <p>
5730             The additional section cache, also called <span><strong class="command">acache</strong></span>,
5731             is an internal cache to improve the response performance of BIND 9.
5732             When additional section caching is enabled, BIND 9 will
5733             cache an internal short-cut to the additional section content for
5734             each answer RR.
5735             Note that <span><strong class="command">acache</strong></span> is an internal caching
5736             mechanism of BIND 9, and is not related to the DNS caching
5737             server function.
5738           </p>
5739 <p>
5740             Additional section caching does not change the
5741             response content (except the RRsets ordering of the additional
5742             section, see below), but can improve the response performance
5743             significantly.
5744             It is particularly effective when BIND 9 acts as an authoritative
5745             server for a zone that has many delegations with many glue RRs.
5746           </p>
5747 <p>
5748             In order to obtain the maximum performance improvement
5749             from additional section caching, setting
5750             <span><strong class="command">additional-from-cache</strong></span>
5751             to <span><strong class="command">no</strong></span> is recommended, since the current
5752             implementation of <span><strong class="command">acache</strong></span>
5753             does not short-cut of additional section information from the
5754             DNS cache data.
5755           </p>
5756 <p>
5757             One obvious disadvantage of <span><strong class="command">acache</strong></span> is
5758             that it requires much more
5759             memory for the internal cached data.
5760             Thus, if the response performance does not matter and memory
5761             consumption is much more critical, the
5762             <span><strong class="command">acache</strong></span> mechanism can be
5763             disabled by setting <span><strong class="command">acache-enable</strong></span> to
5764             <span><strong class="command">no</strong></span>.
5765             It is also possible to specify the upper limit of memory
5766             consumption
5767             for acache by using <span><strong class="command">max-acache-size</strong></span>.
5768           </p>
5769 <p>
5770             Additional section caching also has a minor effect on the
5771             RRset ordering in the additional section.
5772             Without <span><strong class="command">acache</strong></span>,
5773             <span><strong class="command">cyclic</strong></span> order is effective for the additional
5774             section as well as the answer and authority sections.
5775             However, additional section caching fixes the ordering when it
5776             first caches an RRset for the additional section, and the same
5777             ordering will be kept in succeeding responses, regardless of the
5778             setting of <span><strong class="command">rrset-order</strong></span>.
5779             The effect of this should be minor, however, since an
5780             RRset in the additional section
5781             typically only contains a small number of RRs (and in many cases
5782             it only contains a single RR), in which case the
5783             ordering does not matter much.
5784           </p>
5785 <p>
5786             The following is a summary of options related to
5787             <span><strong class="command">acache</strong></span>.
5788           </p>
5789 <div class="variablelist"><dl>
5790 <dt><span class="term"><span><strong class="command">acache-enable</strong></span></span></dt>
5791 <dd><p>
5792                   If <span><strong class="command">yes</strong></span>, additional section caching is
5793                   enabled.  The default value is <span><strong class="command">no</strong></span>.
5794                 </p></dd>
5795 <dt><span class="term"><span><strong class="command">acache-cleaning-interval</strong></span></span></dt>
5796 <dd><p>
5797                   The server will remove stale cache entries, based on an LRU
5798                   based
5799                   algorithm, every <span><strong class="command">acache-cleaning-interval</strong></span> minutes.
5800                   The default is 60 minutes.
5801                   If set to 0, no periodic cleaning will occur.
5802                 </p></dd>
5803 <dt><span class="term"><span><strong class="command">max-acache-size</strong></span></span></dt>
5804 <dd><p>
5805                   The maximum amount of memory in bytes to use for the server's acache.
5806                   When the amount of data in the acache reaches this limit,
5807                   the server
5808                   will clean more aggressively so that the limit is not
5809                   exceeded.
5810                   In a server with multiple views, the limit applies
5811                   separately to the
5812                   acache of each view.
5813                   The default is <code class="literal">16M</code>.
5814                 </p></dd>
5815 </dl></div>
5816 </div>
5817 <div class="sect3" lang="en">
5818 <div class="titlepage"><div><div><h4 class="title">
5819 <a name="id2588485"></a>Content Filtering</h4></div></div></div>
5820 <p>
5821             <acronym class="acronym">BIND</acronym> 9 provides the ability to filter
5822             out DNS responses from external DNS servers containing
5823             certain types of data in the answer section.
5824             Specifically, it can reject address (A or AAAA) records if
5825             the corresponding IPv4 or IPv6 addresses match the given
5826             <code class="varname">address_match_list</code> of the
5827             <span><strong class="command">deny-answer-addresses</strong></span> option.
5828             It can also reject CNAME or DNAME records if the "alias"
5829             name (i.e., the CNAME alias or the substituted query name
5830             due to DNAME) matches the
5831             given <code class="varname">namelist</code> of the
5832             <span><strong class="command">deny-answer-aliases</strong></span> option, where
5833             "match" means the alias name is a subdomain of one of
5834             the <code class="varname">name_list</code> elements.
5835             If the optional <code class="varname">namelist</code> is specified
5836             with <span><strong class="command">except-from</strong></span>, records whose query name
5837             matches the list will be accepted regardless of the filter
5838             setting.
5839             Likewise, if the alias name is a subdomain of the
5840             corresponding zone, the <span><strong class="command">deny-answer-aliases</strong></span>
5841             filter will not apply;
5842             for example, even if "example.com" is specified for
5843             <span><strong class="command">deny-answer-aliases</strong></span>,
5844           </p>
5845 <pre class="programlisting">www.example.com. CNAME xxx.example.com.</pre>
5846 <p>
5847             returned by an "example.com" server will be accepted.
5848           </p>
5849 <p>
5850             In the <code class="varname">address_match_list</code> of the
5851             <span><strong class="command">deny-answer-addresses</strong></span> option, only
5852             <code class="varname">ip_addr</code>
5853             and <code class="varname">ip_prefix</code>
5854             are meaningful;
5855             any <code class="varname">key_id</code> will be silently ignored.
5856           </p>
5857 <p>
5858             If a response message is rejected due to the filtering,
5859             the entire message is discarded without being cached, and
5860             a SERVFAIL error will be returned to the client.
5861           </p>
5862 <p>
5863             This filtering is intended to prevent "DNS rebinding attacks," in
5864             which an attacker, in response to a query for a domain name the
5865             attacker controls, returns an IP address within your own network or
5866             an alias name within your own domain.
5867             A naive web browser or script could then serve as an
5868             unintended proxy, allowing the attacker
5869             to get access to an internal node of your local network
5870             that couldn't be externally accessed otherwise.
5871             See the paper available at
5872             <a href="http://portal.acm.org/citation.cfm?id=1315245.1315298" target="_top">
5873             http://portal.acm.org/citation.cfm?id=1315245.1315298
5874             </a>
5875             for more details about the attacks.
5876           </p>
5877 <p>
5878             For example, if you own a domain named "example.net" and
5879             your internal network uses an IPv4 prefix 192.0.2.0/24,
5880             you might specify the following rules:
5881           </p>
5882 <pre class="programlisting">deny-answer-addresses { 192.0.2.0/24; } except-from { "example.net"; };
5883 deny-answer-aliases { "example.net"; };
5884 </pre>
5885 <p>
5886             If an external attacker lets a web browser in your local
5887             network look up an IPv4 address of "attacker.example.com",
5888             the attacker's DNS server would return a response like this:
5889           </p>
5890 <pre class="programlisting">attacker.example.com. A 192.0.2.1</pre>
5891 <p>
5892             in the answer section.
5893             Since the rdata of this record (the IPv4 address) matches
5894             the specified prefix 192.0.2.0/24, this response will be
5895             ignored.
5896           </p>
5897 <p>
5898             On the other hand, if the browser looks up a legitimate
5899             internal web server "www.example.net" and the
5900             following response is returned to
5901             the <acronym class="acronym">BIND</acronym> 9 server
5902           </p>
5903 <pre class="programlisting">www.example.net. A 192.0.2.2</pre>
5904 <p>
5905             it will be accepted since the owner name "www.example.net"
5906             matches the <span><strong class="command">except-from</strong></span> element,
5907             "example.net".
5908           </p>
5909 <p>
5910             Note that this is not really an attack on the DNS per se.
5911             In fact, there is nothing wrong for an "external" name to
5912             be mapped to your "internal" IP address or domain name
5913             from the DNS point of view.
5914             It might actually be provided for a legitimate purpose,
5915             such as for debugging.
5916             As long as the mapping is provided by the correct owner,
5917             it is not possible or does not make sense to detect
5918             whether the intent of the mapping is legitimate or not
5919             within the DNS.
5920             The "rebinding" attack must primarily be protected at the
5921             application that uses the DNS.
5922             For a large site, however, it may be difficult to protect
5923             all possible applications at once.
5924             This filtering feature is provided only to help such an
5925             operational environment;
5926             it is generally discouraged to turn it on unless you are
5927             very sure you have no other choice and the attack is a
5928             real threat for your applications.
5929           </p>
5930 <p>
5931             Care should be particularly taken if you want to use this
5932             option for addresses within 127.0.0.0/8.
5933             These addresses are obviously "internal", but many
5934             applications conventionally rely on a DNS mapping from
5935             some name to such an address.
5936             Filtering out DNS records containing this address
5937             spuriously can break such applications.
5938           </p>
5939 </div>
5940 <div class="sect3" lang="en">
5941 <div class="titlepage"><div><div><h4 class="title">
5942 <a name="id2588747"></a>Response Policy Zone (RPZ) Rewriting</h4></div></div></div>
5943 <p>
5944             <acronym class="acronym">BIND</acronym> 9 includes a limited
5945             mechanism to modify DNS responses for requests
5946             analogous to email anti-spam DNS blacklists.
5947             Responses can be changed to deny the existence of domains(NXDOMAIN),
5948             deny the existence of IP addresses for domains (NODATA),
5949             or contain other IP addresses or data.
5950           </p>
5951 <p>
5952             Response policy zones are named in the
5953             <span><strong class="command">response-policy</strong></span> option for the view or among the
5954             global options if there is no response-policy option for the view.
5955             RPZs are ordinary DNS zones containing RRsets
5956             that can be queried normally if allowed.
5957             It is usually best to restrict those queries with something like
5958             <span><strong class="command">allow-query { localhost; };</strong></span>.
5959           </p>
5960 <p>
5961             Four policy triggers are encoded in RPZ records, QNAME, IP, NSIP,
5962             and NSDNAME.
5963             QNAME RPZ records triggered by query names of requests and targets
5964             of CNAME records resolved to generate the response.
5965             The owner name of a QNAME RPZ record is the query name relativized
5966             to the RPZ.
5967           </p>
5968 <p>
5969             The second kind of RPZ trigger is an IP address in an A and AAAA
5970             record in the ANSWER section of a response.
5971             IP address triggers are encoded in records that have owner names
5972             that are subdomains of <strong class="userinput"><code>rpz-ip</code></strong> relativized
5973             to the RPZ origin name and encode an IP address or address block.
5974             IPv4 trigger addresses are represented as
5975             <strong class="userinput"><code>prefixlength.B4.B3.B2.B1.rpz-ip</code></strong>.
5976             The prefix length must be between 1 and 32.
5977             All four bytes, B4, B3, B2, and B1, must be present.
5978             B4 is the decimal value of the least significant byte of the
5979             IPv4 address as in IN-ADDR.ARPA.
5980             IPv6 addresses are encoded in a format similar to the standard
5981             IPv6 text representation,
5982             <strong class="userinput"><code>prefixlength.W8.W7.W6.W5.W4.W3.W2.W1.rpz-ip</code></strong>.
5983             Each of W8,...,W1 is a one to four digit hexadecimal number
5984             representing 16 bits of the IPv6 address as in the standard text
5985             representation of IPv6 addresses, but reversed as in IN-ADDR.ARPA.
5986             All 8 words must be present except when consecutive
5987             zero words are replaced with <strong class="userinput"><code>.zz.</code></strong>
5988             analogous to double colons (::) in standard IPv6 text encodings.
5989             The prefix length must be between 1 and 128.
5990           </p>
5991 <p>
5992             NSDNAME triggers match names of authoritative servers
5993             for the query name, a parent of the query name, a CNAME for
5994             query name, or a parent of a CNAME.
5995             They are encoded as subdomains of
5996             <strong class="userinput"><code>rpz-nsdomain</code></strong> relativized
5997             to the RPZ origin name.
5998             NSIP triggers match IP addresses in A and
5999             AAAA RRsets for domains that can be checked against NSDNAME
6000             policy records.
6001             NSIP triggers are encoded like IP triggers except as subdomains of
6002             <strong class="userinput"><code>rpz-nsip</code></strong>.
6003             NSDNAME and NSIP triggers are checked only for names with at
6004             least <span><strong class="command">min-ns-dots</strong></span> dots.
6005             The default value of <span><strong class="command">min-ns-dots</strong></span> is 1 to
6006             exclude top level domains.
6007           </p>
6008 <p>
6009             The query response is checked against all RPZs, so
6010             two or more policy records can be triggered by a response.
6011             Because DNS responses can be rewritten according to at most one
6012             policy record, a single record encoding an action (other than
6013             <span><strong class="command">DISABLED</strong></span> actions) must be chosen.
6014             Triggers or the records that encode them are chosen in
6015             the following order:
6016             </p>
6017 <div class="itemizedlist"><ul type="disc">
6018 <li>Choose the triggered record in the zone that appears
6019                 first in the response-policy option.
6020               </li>
6021 <li>Prefer QNAME to IP to NSDNAME to NSIP triggers
6022                 in a single zone.
6023               </li>
6024 <li>Among NSDNAME triggers, prefer the
6025                 trigger that matches the smallest name under the DNSSEC ordering.
6026               </li>
6027 <li>Among IP or NSIP triggers, prefer the trigger
6028                 with the longest prefix.
6029               </li>
6030 <li>Among triggers with the same prefex length,
6031                 prefer the IP or NSIP trigger that matches
6032                 the smallest IP address.
6033               </li>
6034 </ul></div>
6035 <p>
6036           </p>
6037 <p>
6038             When the processing of a response is restarted to resolve
6039             DNAME or CNAME records and a policy record set has
6040             not been triggered,
6041             all RPZs are again consulted for the DNAME or CNAME names
6042             and addresses.
6043           </p>
6044 <p>
6045             RPZ record sets are sets of any types of DNS record except
6046             DNAME or DNSSEC that encode actions or responses to queries.
6047             </p>
6048 <div class="itemizedlist"><ul type="disc">
6049 <li>The <span><strong class="command">NXDOMAIN</strong></span> response is encoded
6050                 by a CNAME whose target is the root domain (.)
6051               </li>
6052 <li>A CNAME whose target is the wildcard top-level
6053                 domain (*.) specifies the <span><strong class="command">NODATA</strong></span> action,
6054                 which rewrites the response to NODATA or ANCOUNT=1.
6055               </li>
6056 <li>The <span><strong class="command">Local Data</strong></span> action is
6057                 represented by a set ordinary DNS records that are used
6058                 to answer queries.  Queries for record types not the
6059                 set are answered with NODATA.
6060
6061                 A special form of local data is a CNAME whose target is a
6062                 wildcard such as *.example.com.
6063                 It is used as if were an ordinary CNAME after the astrisk (*)
6064                 has been replaced with the query name.
6065                 The purpose for this special form is query logging in the
6066                 walled garden's authority DNS server.
6067               </li>
6068 <li>The <span><strong class="command">PASSTHRU</strong></span> policy is specified
6069                 by a CNAME whose target is <span><strong class="command">rpz-passthru.</strong></span>
6070                 It causes the response to not be rewritten
6071                 and is most often used to "poke holes" in policies for
6072                 CIDR blocks.
6073                 (A CNAME whose target is the variable part of its owner name
6074                 is an obsolete specification of the PASSTHRU policy.)
6075               </li>
6076 </ul></div>
6077 <p>
6078           </p>
6079 <p>
6080             The actions specified in an RPZ can be overridden with a
6081             <span><strong class="command">policy</strong></span> clause in the
6082             <span><strong class="command">response-policy</strong></span> option.
6083             An organization using an RPZ provided by another organization might
6084             use this mechanism to redirect domains to its own walled garden.
6085             </p>
6086 <div class="itemizedlist"><ul type="disc">
6087 <li>
6088 <span><strong class="command">GIVEN</strong></span> says "do not override but
6089                 perform the action specified in the zone."
6090               </li>
6091 <li>
6092 <span><strong class="command">DISABLED</strong></span> causes policy records to do
6093                 nothing but log what they might have done.
6094                 The response to the DNS query will be written according to
6095                 any triggered policy records that are not disabled.
6096                 Disabled policy zones should appear first,
6097                 because they will often not be logged
6098                 if a higher precedence trigger is found first.
6099               </li>
6100 <li>
6101 <span><strong class="command">PASSTHRU</strong></span> causes all policy records
6102                 to act as if they were CNAME records with targets the variable
6103                 part of their owner name.  They protect the response from
6104                 being changed.
6105               </li>
6106 <li>
6107 <span><strong class="command">NXDOMAIN</strong></span> causes all RPZ records
6108                 to specify NXDOMAIN policies.
6109               </li>
6110 <li>
6111 <span><strong class="command">NODATA</strong></span> overrides with the
6112                 NODATA policy
6113               </li>
6114 <li>
6115 <span><strong class="command">CNAME domain</strong></span> causes all RPZ
6116                 policy records to act as if they were "cname domain" records.
6117               </li>
6118 </ul></div>
6119 <p>
6120           </p>
6121 <p>
6122             By default, the actions encoded in an RPZ are applied
6123             only to queries that ask for recursion (RD=1).
6124             That default can be changed for a single RPZ or all RPZs in a view
6125             with a <span><strong class="command">recursive-only no</strong></span> clause.
6126             This feature is useful for serving the same zone files
6127             both inside and outside an RFC 1918 cloud and using RPZ to
6128             delete answers that would otherwise contain RFC 1918 values
6129             on the externally visible name server or view.
6130           </p>
6131 <p>
6132             Also by default, RPZ actions are applied only to DNS requests that
6133             either do not request DNSSEC metadata (DO=0) or when no DNSSEC
6134             records are available for request name in the original zone (not
6135             the response policy zone).
6136             This default can be changed for all RPZs in a view with a
6137             <span><strong class="command">break-dnssec yes</strong></span> clause.
6138             In that case, RPZ actions are applied regardless of DNSSEC.
6139             The name of the clause option reflects the fact that results
6140             rewritten by RPZ actions cannot verify.
6141           </p>
6142 <p>
6143             The TTL of a record modified by RPZ policies is set from the
6144             TTL of the relevant record in policy zone.  It is then limited
6145             to a maximum value.
6146             The <span><strong class="command">max-policy-ttl</strong></span> clause changes that
6147             maximum from its default of 5.
6148           </p>
6149 <p>
6150             For example, you might use this option statement
6151           </p>
6152 <pre class="programlisting">    response-policy { zone "badlist"; };</pre>
6153 <p>
6154             and this zone statement
6155           </p>
6156 <pre class="programlisting">    zone "badlist" {type master; file "master/badlist"; allow-query {none;}; };</pre>
6157 <p>
6158             with this zone file
6159           </p>
6160 <pre class="programlisting">$TTL 1H
6161 @                       SOA LOCALHOST. named-mgr.example.com (1 1h 15m 30d 2h)
6162                         NS  LOCALHOST.
6163
6164 ; QNAME policy records.  There are no periods (.) after the owner names.
6165 nxdomain.domain.com     CNAME   .               ; NXDOMAIN policy
6166 nodata.domain.com       CNAME   *.              ; NODATA policy
6167 bad.domain.com          A       10.0.0.1        ; redirect to a walled garden
6168                         AAAA    2001:2::1
6169
6170 ; do not rewrite (PASSTHRU) OK.DOMAIN.COM
6171 ok.domain.com           CNAME   rpz-passthru.
6172
6173 bzone.domain.com        CNAME   garden.example.com.
6174
6175 ; redirect x.bzone.domain.com to x.bzone.domain.com.garden.example.com
6176 *.bzone.domain.com      CNAME   *.garden.example.com.
6177
6178
6179 ; IP policy records that rewrite all answers for 127/8 except 127.0.0.1
6180 8.0.0.0.127.rpz-ip      CNAME   .
6181 32.1.0.0.127.rpz-ip     CNAME   rpz-passthru.
6182
6183 ; NSDNAME and NSIP policy records
6184 ns.domain.com.rpz-nsdname   CNAME   .
6185 48.zz.2.2001.rpz-nsip       CNAME   .
6186 </pre>
6187 <p>
6188             RPZ can affect server performance.
6189             Each configured response policy zone requires the server to
6190             perform one to four additional database lookups before a
6191             query can be answered.
6192             For example, a DNS server with four policy zones, each with all
6193             four kinds of response triggers, QNAME, IP, NSIP, and
6194             NSDNAME, requires a total of 17 times as many database
6195             lookups as a similar DNS server with no response policy zones.
6196             A <acronym class="acronym">BIND9</acronym> server with adequate memory and one
6197             response policy zone with QNAME and IP triggers might achieve a
6198             maximum queries-per-second rate about 20% lower.
6199             A server with four response policy zones with QNAME and IP
6200             triggers might have a maximum QPS rate about 50% lower.
6201           </p>
6202 <p>
6203             Responses rewritten by RPZ are counted in the
6204             <span><strong class="command">RPZRewrites</strong></span> statistics.
6205           </p>
6206 </div>
6207 <div class="sect3" lang="en">
6208 <div class="titlepage"><div><div><h4 class="title">
6209 <a name="id2589177"></a>Response Rate Limiting</h4></div></div></div>
6210 <p>
6211             This feature is only available when <acronym class="acronym">BIND</acronym> 9
6212             is compiled with the <strong class="userinput"><code>--enable-rrl</code></strong>
6213             option on the "configure" command line.
6214           </p>
6215 <p>
6216             Excessive almost identical UDP <span class="emphasis"><em>responses</em></span>
6217             can be controlled by configuring a
6218             <span><strong class="command">rate-limit</strong></span> clause in an
6219             <span><strong class="command">options</strong></span> or <span><strong class="command">view</strong></span> statement.
6220             This mechanism keeps authoritative BIND 9 from being used
6221             in amplifying reflection denial of service (DoS) attacks.
6222             Short truncated (TC=1) responses can be sent to provide
6223             rate-limited responses to legitimate clients within
6224             a range of forged, attacked IP addresses.
6225             Legitimate clients react to dropped or truncated response
6226             by retrying with UDP or with TCP respectively.
6227           </p>
6228 <p>
6229             This mechanism is intended for authoritative DNS servers.
6230             It can be used on recursive servers but can slow
6231             applications such as SMTP servers (mail receivers) and
6232             HTTP clients (web browsers) that repeatedly request the
6233             same domains.
6234             When possible, closing "open" recursive servers is better.
6235           </p>
6236 <p>
6237             Response rate limiting uses a "credit" or "token bucket" scheme.
6238             Each combination of identical response and client
6239             has a conceptual account that earns a specified number
6240             of credits every second.
6241             A prospective response debits its account by one.
6242             Responses are dropped or truncated
6243             while the account is negative.
6244             Responses are tracked within a rolling window of time
6245             which defaults to 15 seconds, but can be configured with
6246             the <span><strong class="command">window</strong></span> option to any value from
6247             1 to 3600 seconds (1 hour).
6248             The account cannot become more positive than
6249             the per-second limit
6250             or more negative than <span><strong class="command">window</strong></span>
6251             times the per-second limit.
6252             When the specified number of credits for a class of
6253             responses is set to 0, those responses are not rate limited.
6254           </p>
6255 <p>
6256             The notions of "identical response" and "DNS client"
6257             for rate limiting are not simplistic.
6258             All responses to an address block are counted as if to a
6259             single client.
6260             The prefix lengths of addresses blocks are
6261             specified with <span><strong class="command">ipv4-prefix-length</strong></span> (default 24)
6262             and <span><strong class="command">ipv6-prefix-length</strong></span> (default 56).
6263           </p>
6264 <p>
6265             All non-empty responses for a valid domain name (qname)
6266             and record type (qtype) are identical and have a limit specified
6267             with <span><strong class="command">responses-per-second</strong></span>
6268             (default 0 or no limit).
6269             All empty (NODATA) responses for a valid domain,
6270             regardless of query type, are identical.
6271             Responses in the NODATA class are limited by
6272             <span><strong class="command">nodata-per-second</strong></span>
6273             (default <span><strong class="command">responses-per-second</strong></span>).
6274             Requests for any and all undefined subdomains of a given
6275             valid domain result in NXDOMAIN errors, and are identical
6276             regardless of query type.
6277             They are limited by <span><strong class="command">nxdomain-per-second</strong></span>
6278             (default <span><strong class="command">responses-per-second</strong></span>).
6279             This controls some attacks using random names, but
6280             can be relaxed or turned off (set to 0)
6281             on servers that expect many legitimate
6282             NXDOMAIN responses, such as from anti-spam blacklists.
6283             Referrals or delegations to the server of a given
6284             domain are identical and are limited by
6285             <span><strong class="command">referrals-per-second</strong></span>
6286             (default <span><strong class="command">responses-per-second</strong></span>).
6287           </p>
6288 <p>
6289             Responses generated from local wildcards are counted and limited
6290             as if they were for the parent domain name.
6291             This controls flooding using random.wild.example.com.
6292           </p>
6293 <p>
6294             All requests that result in DNS errors other
6295             than NXDOMAIN, such as SERVFAIL and FORMERR, are identical
6296             regardless of requested name (qname) or record type (qtype).
6297             This controls attacks using invalid requests or distant,
6298             broken authoritative servers.
6299             By default the limit on errors is the same as the
6300             <span><strong class="command">responses-per-second</strong></span> value,
6301             but it can be set separately with
6302             <span><strong class="command">errors-per-second</strong></span>.
6303           </p>
6304 <p>
6305             Many attacks using DNS involve UDP requests with forged source
6306             addresses.
6307             Rate limiting prevents the use of BIND 9 to flood a network
6308             with responses to requests with forged source addresses,
6309             but could let a third party block responses to legitimate requests.
6310             There is a mechanism that can answer some legitimate
6311             requests from a client whose address is being forged in a flood.
6312             Setting <span><strong class="command">slip</strong></span> to 2 (its default) causes every
6313             other UDP request to be answered with a small truncated (TC=1)
6314             response.
6315             The small size and reduced frequency, and so lack of
6316             amplification, of "slipped" responses make them unattractive
6317             for reflection DoS attacks.
6318             <span><strong class="command">slip</strong></span> must be between 0 and 10.
6319             A value of 0 does not "slip":
6320             no truncated responses are sent due to rate limiting,
6321             all responses are dropped.
6322             A value of 1 causes every response to slip;
6323             values between 2 and 10 cause every n'th response to slip.
6324             Some error responses including REFUSED and SERVFAIL
6325             cannot be replaced with truncated responses and are instead
6326             leaked at the <span><strong class="command">slip</strong></span> rate.
6327           </p>
6328 <p>
6329             (NOTE: Dropped responses from an authoritative server may
6330             reduce the difficulty of a third party successfully forging
6331             a response to a recursive resolver. The best security
6332             against forged responses is for authoritative operators
6333             to sign their zones using DNSSEC and for resolver operators
6334             to validate the responses. When this is not an option,
6335             operators who are more concerned with response integrity
6336             than with flood mitigation may consider setting
6337             <span><strong class="command">slip</strong></span> to 1, causing all rate-limited
6338             responses to be truncated rather than dropped.  This reduces
6339             the effectiveness of rate-limiting against reflection attacks.)
6340           </p>
6341 <p>
6342             When the approximate query per second rate exceeds
6343             the <span><strong class="command">qps-scale</strong></span> value,
6344             then the <span><strong class="command">responses-per-second</strong></span>,
6345             <span><strong class="command">errors-per-second</strong></span>,
6346             <span><strong class="command">nxdomains-per-second</strong></span> and
6347             <span><strong class="command">all-per-second</strong></span> values are reduced by the
6348             ratio of the current rate to the <span><strong class="command">qps-scale</strong></span> value.
6349             This feature can tighten defenses during attacks.
6350             For example, with
6351             <span><strong class="command">qps-scale 250; responses-per-second 20;</strong></span> and
6352             a total query rate of 1000 queries/second for all queries from
6353             all DNS clients including via TCP,
6354             then the effective responses/second limit changes to
6355             (250/1000)*20 or 5.
6356             Responses sent via TCP are not limited
6357             but are counted to compute the query per second rate.
6358           </p>
6359 <p>
6360             Communities of DNS clients can be given their own parameters or no
6361             rate limiting by putting
6362             <span><strong class="command">rate-limit</strong></span> statements in <span><strong class="command">view</strong></span>
6363             statements instead of the global <span><strong class="command">option</strong></span>
6364             statement.
6365             A <span><strong class="command">rate-limit</strong></span> statement in a view replaces,
6366             rather than supplementing, a <span><strong class="command">rate-limit</strong></span>
6367             statement among the main options.
6368             DNS clients within a view can be exempted from rate limits
6369             with the <span><strong class="command">exempt-clients</strong></span> clause.
6370           </p>
6371 <p>
6372             UDP responses of all kinds can be limited with the
6373             <span><strong class="command">all-per-second</strong></span> phrase.
6374             This rate limiting is unlike the rate limiting provided by
6375             <span><strong class="command">responses-per-second</strong></span>,
6376             <span><strong class="command">errors-per-second</strong></span>, and
6377             <span><strong class="command">nxdomains-per-second</strong></span> on a DNS server
6378             which are often invisible to the victim of a DNS reflection attack.
6379             Unless the forged requests of the attack are the same as the
6380             legitimate requests of the victim, the victim's requests are
6381             not affected.
6382             Responses affected by an <span><strong class="command">all-per-second</strong></span> limit
6383             are always dropped; the <span><strong class="command">slip</strong></span> value has no
6384             effect.
6385             An <span><strong class="command">all-per-second</strong></span> limit should be
6386             at least 4 times as large as the other limits,
6387             because single DNS clients often send bursts of legitimate
6388             requests.
6389             For example, the receipt of a single mail message can prompt
6390             requests from an SMTP server for NS, PTR, A, and AAAA records
6391             as the incoming SMTP/TCP/IP connection is considered.
6392             The SMTP server can need additional NS, A, AAAA, MX, TXT, and SPF
6393             records as it considers the STMP <span><strong class="command">Mail From</strong></span>
6394             command.
6395             Web browsers often repeatedly resolve the same names that
6396             are repeated in HTML &lt;IMG&gt; tags in a page.
6397             <span><strong class="command">All-per-second</strong></span> is similar to the
6398             rate limiting offered by firewalls but often inferior.
6399             Attacks that justify ignoring the
6400             contents of DNS responses are likely to be attacks on the
6401             DNS server itself.
6402             They usually should be discarded before the DNS server
6403             spends resources making TCP connections or parsing DNS requests,
6404             but that rate limiting must be done before the
6405             DNS server sees the requests.
6406           </p>
6407 <p>
6408             The maximum size of the table used to track requests and
6409             rate limit responses is set with <span><strong class="command">max-table-size</strong></span>.
6410             Each entry in the table is between 40 and 80 bytes.
6411             The table needs approximately as many entries as the number
6412             of requests received per second.
6413             The default is 20,000.
6414             To reduce the cold start of growing the table,
6415             <span><strong class="command">min-table-size</strong></span> (default 500)
6416             can set the minimum table size.
6417             Enable <span><strong class="command">rate-limit</strong></span> category logging to monitor
6418             expansions of the table and inform
6419             choices for the initial and maximum table size.
6420           </p>
6421 <p>
6422             Use <span><strong class="command">log-only yes</strong></span> to test rate limiting parameters
6423             without actually dropping any requests.
6424           </p>
6425 <p>
6426             Responses dropped by rate limits are included in the
6427             <span><strong class="command">RateDropped</strong></span> and <span><strong class="command">QryDropped</strong></span>
6428             statistics.
6429             Responses that truncated by rate limits are included in
6430             <span><strong class="command">RateSlipped</strong></span> and <span><strong class="command">RespTruncated</strong></span>.
6431           </p>
6432 </div>
6433 </div>
6434 <div class="sect2" lang="en">
6435 <div class="titlepage"><div><div><h3 class="title">
6436 <a name="server_statement_grammar"></a><span><strong class="command">server</strong></span> Statement Grammar</h3></div></div></div>
6437 <pre class="programlisting"><span><strong class="command">server</strong></span> <em class="replaceable"><code>ip_addr[/prefixlen]</code></em> {
6438     [<span class="optional"> bogus <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6439     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6440     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6441     [<span class="optional"> request-nsid <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6442     [<span class="optional"> edns <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6443     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
6444     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
6445     [<span class="optional"> transfers <em class="replaceable"><code>number</code></em> ; </span>]
6446     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em> ; ]</span>]
6447     [<span class="optional"> keys <em class="replaceable"><code>{ string ; [<span class="optional"> string ; [<span class="optional">...</span>]</span>] }</code></em> ; </span>]
6448     [<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>]
6449     [<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>]
6450     [<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>]
6451     [<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>]
6452     [<span class="optional"> query-source [<span class="optional"> address ( <em class="replaceable"><code>ip_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
6453                   [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]; </span>]
6454     [<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>]
6455                      [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]; </span>]
6456     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6457     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
6458     [<span class="optional"> queryport-pool-updateinterval <em class="replaceable"><code>number</code></em>; </span>]
6459 };
6460 </pre>
6461 </div>
6462 <div class="sect2" lang="en">
6463 <div class="titlepage"><div><div><h3 class="title">
6464 <a name="server_statement_definition_and_usage"></a><span><strong class="command">server</strong></span> Statement Definition and
6465             Usage</h3></div></div></div>
6466 <p>
6467             The <span><strong class="command">server</strong></span> statement defines
6468             characteristics
6469             to be associated with a remote name server.  If a prefix length is
6470             specified, then a range of servers is covered.  Only the most
6471             specific
6472             server clause applies regardless of the order in
6473             <code class="filename">named.conf</code>.
6474           </p>
6475 <p>
6476             The <span><strong class="command">server</strong></span> statement can occur at
6477             the top level of the
6478             configuration file or inside a <span><strong class="command">view</strong></span>
6479             statement.
6480             If a <span><strong class="command">view</strong></span> statement contains
6481             one or more <span><strong class="command">server</strong></span> statements, only
6482             those
6483             apply to the view and any top-level ones are ignored.
6484             If a view contains no <span><strong class="command">server</strong></span>
6485             statements,
6486             any top-level <span><strong class="command">server</strong></span> statements are
6487             used as
6488             defaults.
6489           </p>
6490 <p>
6491             If you discover that a remote server is giving out bad data,
6492             marking it as bogus will prevent further queries to it. The
6493             default
6494             value of <span><strong class="command">bogus</strong></span> is <span><strong class="command">no</strong></span>.
6495           </p>
6496 <p>
6497             The <span><strong class="command">provide-ixfr</strong></span> clause determines
6498             whether
6499             the local server, acting as master, will respond with an
6500             incremental
6501             zone transfer when the given remote server, a slave, requests it.
6502             If set to <span><strong class="command">yes</strong></span>, incremental transfer
6503             will be provided
6504             whenever possible. If set to <span><strong class="command">no</strong></span>,
6505             all transfers
6506             to the remote server will be non-incremental. If not set, the
6507             value
6508             of the <span><strong class="command">provide-ixfr</strong></span> option in the
6509             view or
6510             global options block is used as a default.
6511           </p>
6512 <p>
6513             The <span><strong class="command">request-ixfr</strong></span> clause determines
6514             whether
6515             the local server, acting as a slave, will request incremental zone
6516             transfers from the given remote server, a master. If not set, the
6517             value of the <span><strong class="command">request-ixfr</strong></span> option in
6518             the view or global options block is used as a default. It may
6519             also be set in the zone block and, if set there, it will
6520             override the global or view setting for that zone.
6521           </p>
6522 <p>
6523             IXFR requests to servers that do not support IXFR will
6524             automatically
6525             fall back to AXFR.  Therefore, there is no need to manually list
6526             which servers support IXFR and which ones do not; the global
6527             default
6528             of <span><strong class="command">yes</strong></span> should always work.
6529             The purpose of the <span><strong class="command">provide-ixfr</strong></span> and
6530             <span><strong class="command">request-ixfr</strong></span> clauses is
6531             to make it possible to disable the use of IXFR even when both
6532             master
6533             and slave claim to support it, for example if one of the servers
6534             is buggy and crashes or corrupts data when IXFR is used.
6535           </p>
6536 <p>
6537             The <span><strong class="command">edns</strong></span> clause determines whether
6538             the local server will attempt to use EDNS when communicating
6539             with the remote server.  The default is <span><strong class="command">yes</strong></span>.
6540           </p>
6541 <p>
6542             The <span><strong class="command">edns-udp-size</strong></span> option sets the EDNS UDP size
6543             that is advertised by <span><strong class="command">named</strong></span> when querying the remote server.
6544             Valid values are 512 to 4096 bytes (values outside this range will be
6545             silently adjusted).  This option is useful when you wish to
6546             advertises a different value to this server than the value you
6547             advertise globally, for example, when there is a firewall at the
6548             remote site that is blocking large replies.
6549           </p>
6550 <p>
6551             The <span><strong class="command">max-udp-size</strong></span> option sets the
6552             maximum EDNS UDP message size <span><strong class="command">named</strong></span> will send.  Valid
6553             values are 512 to 4096 bytes (values outside this range will
6554             be silently adjusted).  This option is useful when you
6555             know that there is a firewall that is blocking large
6556             replies from <span><strong class="command">named</strong></span>.
6557           </p>
6558 <p>
6559             The server supports two zone transfer methods. The first, <span><strong class="command">one-answer</strong></span>,
6560             uses one DNS message per resource record transferred. <span><strong class="command">many-answers</strong></span> packs
6561             as many resource records as possible into a message. <span><strong class="command">many-answers</strong></span> is
6562             more efficient, but is only known to be understood by <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
6563             8.x, and patched versions of <acronym class="acronym">BIND</acronym>
6564             4.9.5. You can specify which method
6565             to use for a server with the <span><strong class="command">transfer-format</strong></span> option.
6566             If <span><strong class="command">transfer-format</strong></span> is not
6567             specified, the <span><strong class="command">transfer-format</strong></span>
6568             specified
6569             by the <span><strong class="command">options</strong></span> statement will be
6570             used.
6571           </p>
6572 <p><span><strong class="command">transfers</strong></span>
6573             is used to limit the number of concurrent inbound zone
6574             transfers from the specified server. If no
6575             <span><strong class="command">transfers</strong></span> clause is specified, the
6576             limit is set according to the
6577             <span><strong class="command">transfers-per-ns</strong></span> option.
6578           </p>
6579 <p>
6580             The <span><strong class="command">keys</strong></span> clause identifies a
6581             <span><strong class="command">key_id</strong></span> defined by the <span><strong class="command">key</strong></span> statement,
6582             to be used for transaction security (TSIG, <a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
6583             when talking to the remote server.
6584             When a request is sent to the remote server, a request signature
6585             will be generated using the key specified here and appended to the
6586             message. A request originating from the remote server is not
6587             required
6588             to be signed by this key.
6589           </p>
6590 <p>
6591             Although the grammar of the <span><strong class="command">keys</strong></span>
6592             clause
6593             allows for multiple keys, only a single key per server is
6594             currently
6595             supported.
6596           </p>
6597 <p>
6598             The <span><strong class="command">transfer-source</strong></span> and
6599             <span><strong class="command">transfer-source-v6</strong></span> clauses specify
6600             the IPv4 and IPv6 source
6601             address to be used for zone transfer with the remote server,
6602             respectively.
6603             For an IPv4 remote server, only <span><strong class="command">transfer-source</strong></span> can
6604             be specified.
6605             Similarly, for an IPv6 remote server, only
6606             <span><strong class="command">transfer-source-v6</strong></span> can be
6607             specified.
6608             For more details, see the description of
6609             <span><strong class="command">transfer-source</strong></span> and
6610             <span><strong class="command">transfer-source-v6</strong></span> in
6611             <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
6612           </p>
6613 <p>
6614             The <span><strong class="command">notify-source</strong></span> and
6615             <span><strong class="command">notify-source-v6</strong></span> clauses specify the
6616             IPv4 and IPv6 source address to be used for notify
6617             messages sent to remote servers, respectively.  For an
6618             IPv4 remote server, only <span><strong class="command">notify-source</strong></span>
6619             can be specified.  Similarly, for an IPv6 remote server,
6620             only <span><strong class="command">notify-source-v6</strong></span> can be specified.
6621           </p>
6622 <p>
6623             The <span><strong class="command">query-source</strong></span> and
6624             <span><strong class="command">query-source-v6</strong></span> clauses specify the
6625             IPv4 and IPv6 source address to be used for queries
6626             sent to remote servers, respectively.  For an IPv4
6627             remote server, only <span><strong class="command">query-source</strong></span> can
6628             be specified.  Similarly, for an IPv6 remote server,
6629             only <span><strong class="command">query-source-v6</strong></span> can be specified.
6630           </p>
6631 <p>
6632             The <span><strong class="command">request-nsid</strong></span> clause determines
6633             whether the local server will add a NSID EDNS option
6634             to requests sent to the server.  This overrides
6635             <span><strong class="command">request-nsid</strong></span> set at the view or
6636             option level.
6637           </p>
6638 </div>
6639 <div class="sect2" lang="en">
6640 <div class="titlepage"><div><div><h3 class="title">
6641 <a name="statschannels"></a><span><strong class="command">statistics-channels</strong></span> Statement Grammar</h3></div></div></div>
6642 <pre class="programlisting"><span><strong class="command">statistics-channels</strong></span> {
6643    [ inet ( ip_addr | * ) [ port ip_port ]
6644    [ allow { <em class="replaceable"><code> address_match_list </code></em> } ]; ]
6645    [ inet ...; ]
6646 };
6647 </pre>
6648 </div>
6649 <div class="sect2" lang="en">
6650 <div class="titlepage"><div><div><h3 class="title">
6651 <a name="id2590471"></a><span><strong class="command">statistics-channels</strong></span> Statement Definition and
6652             Usage</h3></div></div></div>
6653 <p>
6654           The <span><strong class="command">statistics-channels</strong></span> statement
6655           declares communication channels to be used by system
6656           administrators to get access to statistics information of
6657           the name server.
6658         </p>
6659 <p>
6660           This statement intends to be flexible to support multiple
6661           communication protocols in the future, but currently only
6662           HTTP access is supported.
6663           It requires that BIND 9 be compiled with libxml2;
6664           the <span><strong class="command">statistics-channels</strong></span> statement is
6665           still accepted even if it is built without the library,
6666           but any HTTP access will fail with an error.
6667         </p>
6668 <p>
6669           An <span><strong class="command">inet</strong></span> control channel is a TCP socket
6670           listening at the specified <span><strong class="command">ip_port</strong></span> on the
6671           specified <span><strong class="command">ip_addr</strong></span>, which can be an IPv4 or IPv6
6672           address.  An <span><strong class="command">ip_addr</strong></span> of <code class="literal">*</code> (asterisk) is
6673           interpreted as the IPv4 wildcard address; connections will be
6674           accepted on any of the system's IPv4 addresses.
6675           To listen on the IPv6 wildcard address,
6676           use an <span><strong class="command">ip_addr</strong></span> of <code class="literal">::</code>.
6677         </p>
6678 <p>
6679           If no port is specified, port 80 is used for HTTP channels.
6680           The asterisk "<code class="literal">*</code>" cannot be used for
6681           <span><strong class="command">ip_port</strong></span>.
6682         </p>
6683 <p>
6684           The attempt of opening a statistics channel is
6685           restricted by the optional <span><strong class="command">allow</strong></span> clause.
6686           Connections to the statistics channel are permitted based on the
6687           <span><strong class="command">address_match_list</strong></span>.
6688           If no <span><strong class="command">allow</strong></span> clause is present,
6689           <span><strong class="command">named</strong></span> accepts connection
6690           attempts from any address; since the statistics may
6691           contain sensitive internal information, it is highly
6692           recommended to restrict the source of connection requests
6693           appropriately.
6694         </p>
6695 <p>
6696           If no <span><strong class="command">statistics-channels</strong></span> statement is present,
6697           <span><strong class="command">named</strong></span> will not open any communication channels.
6698         </p>
6699 <p>
6700           If the statistics channel is configured to listen on 127.0.0.1
6701           port 8888, then the statistics are accessible in XML format at
6702           <a href="http://127.0.0.1:8888/" target="_top">http://127.0.0.1:8888/</a> or
6703           <a href="http://127.0.0.1:8888/xml" target="_top">http://127.0.0.1:8888/xml</a>. A CSS file is
6704           included which can format the XML statistics into tables
6705           when viewed with a stylesheet-capable browser.  When
6706           <acronym class="acronym">BIND</acronym> 9 is configured with --enable-newstats,
6707           a new XML schema is used (version 3) which adds additional
6708           zone statistics and uses a flatter tree for more efficient
6709           parsing.  The stylesheet included uses the Google Charts API
6710           to render data into into charts and graphs when using a
6711           javascript-capable browser.
6712         </p>
6713 <p>
6714           Applications that depend on a particular XML schema
6715           can request
6716           <a href="http://127.0.0.1:8888/xml/v2" target="_top">http://127.0.0.1:8888/xml/v2</a> for version 2
6717           of the statistics XML schema or
6718           <a href="http://127.0.0.1:8888/xml/v3" target="_top">http://127.0.0.1:8888/xml/v3</a> for version 3.
6719           If the requested schema is supported by the server, then
6720           it will respond; if not, it will return a "page not found"
6721           error.
6722         </p>
6723 </div>
6724 <div class="sect2" lang="en">
6725 <div class="titlepage"><div><div><h3 class="title">
6726 <a name="trusted-keys"></a><span><strong class="command">trusted-keys</strong></span> Statement Grammar</h3></div></div></div>
6727 <pre class="programlisting"><span><strong class="command">trusted-keys</strong></span> {
6728     <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> ;
6729     [<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>]
6730 };
6731 </pre>
6732 </div>
6733 <div class="sect2" lang="en">
6734 <div class="titlepage"><div><div><h3 class="title">
6735 <a name="id2590642"></a><span><strong class="command">trusted-keys</strong></span> Statement Definition
6736             and Usage</h3></div></div></div>
6737 <p>
6738             The <span><strong class="command">trusted-keys</strong></span> statement defines
6739             DNSSEC security roots. DNSSEC is described in <a href="Bv9ARM.ch04.html#DNSSEC" title="DNSSEC">the section called &#8220;DNSSEC&#8221;</a>. A security root is defined when the
6740             public key for a non-authoritative zone is known, but
6741             cannot be securely obtained through DNS, either because
6742             it is the DNS root zone or because its parent zone is
6743             unsigned.  Once a key has been configured as a trusted
6744             key, it is treated as if it had been validated and
6745             proven secure. The resolver attempts DNSSEC validation
6746             on all DNS data in subdomains of a security root.
6747           </p>
6748 <p>
6749             All keys (and corresponding zones) listed in
6750             <span><strong class="command">trusted-keys</strong></span> are deemed to exist regardless
6751             of what parent zones say.  Similarly for all keys listed in
6752             <span><strong class="command">trusted-keys</strong></span> only those keys are
6753             used to validate the DNSKEY RRset.  The parent's DS RRset
6754             will not be used.
6755           </p>
6756 <p>
6757             The <span><strong class="command">trusted-keys</strong></span> statement can contain
6758             multiple key entries, each consisting of the key's
6759             domain name, flags, protocol, algorithm, and the Base-64
6760             representation of the key data.
6761             Spaces, tabs, newlines and carriage returns are ignored
6762             in the key data, so the configuration may be split up into
6763             multiple lines.
6764           </p>
6765 <p>
6766             <span><strong class="command">trusted-keys</strong></span> may be set at the top level
6767             of <code class="filename">named.conf</code> or within a view.  If it is
6768             set in both places, they are additive: keys defined at the top
6769             level are inherited by all views, but keys defined in a view
6770             are only used within that view.
6771           </p>
6772 </div>
6773 <div class="sect2" lang="en">
6774 <div class="titlepage"><div><div><h3 class="title">
6775 <a name="id2590757"></a><span><strong class="command">managed-keys</strong></span> Statement Grammar</h3></div></div></div>
6776 <pre class="programlisting"><span><strong class="command">managed-keys</strong></span> {
6777     <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> ;
6778     [<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>]
6779 };
6780 </pre>
6781 </div>
6782 <div class="sect2" lang="en">
6783 <div class="titlepage"><div><div><h3 class="title">
6784 <a name="managed-keys"></a><span><strong class="command">managed-keys</strong></span> Statement Definition
6785             and Usage</h3></div></div></div>
6786 <p>
6787             The <span><strong class="command">managed-keys</strong></span> statement, like
6788             <span><strong class="command">trusted-keys</strong></span>, defines DNSSEC
6789             security roots.  The difference is that
6790             <span><strong class="command">managed-keys</strong></span> can be kept up to date
6791             automatically, without intervention from the resolver
6792             operator.
6793           </p>
6794 <p>
6795             Suppose, for example, that a zone's key-signing
6796             key was compromised, and the zone owner had to revoke and
6797             replace the key.  A resolver which had the old key in a
6798             <span><strong class="command">trusted-keys</strong></span> statement would be
6799             unable to validate this zone any longer; it would
6800             reply with a SERVFAIL response code.  This would
6801             continue until the resolver operator had updated the
6802             <span><strong class="command">trusted-keys</strong></span> statement with the new key.
6803           </p>
6804 <p>
6805             If, however, the zone were listed in a
6806             <span><strong class="command">managed-keys</strong></span> statement instead, then the
6807             zone owner could add a "stand-by" key to the zone in advance.
6808             <span><strong class="command">named</strong></span> would store the stand-by key, and
6809             when the original key was revoked, <span><strong class="command">named</strong></span>
6810             would be able to transition smoothly to the new key.  It would
6811             also recognize that the old key had been revoked, and cease
6812             using that key to validate answers, minimizing the damage that
6813             the compromised key could do.
6814           </p>
6815 <p>
6816             A <span><strong class="command">managed-keys</strong></span> statement contains a list of
6817             the keys to be managed, along with information about how the
6818             keys are to be initialized for the first time.  The only
6819             initialization method currently supported (as of
6820             <acronym class="acronym">BIND</acronym> 9.7.0) is <code class="literal">initial-key</code>.
6821             This means the <span><strong class="command">managed-keys</strong></span> statement must
6822             contain a copy of the initializing key.  (Future releases may
6823             allow keys to be initialized by other methods, eliminating this
6824             requirement.)
6825           </p>
6826 <p>
6827             Consequently, a <span><strong class="command">managed-keys</strong></span> statement
6828             appears similar to a <span><strong class="command">trusted-keys</strong></span>, differing
6829             in the presence of the second field, containing the keyword
6830             <code class="literal">initial-key</code>.  The difference is, whereas the
6831             keys listed in a <span><strong class="command">trusted-keys</strong></span> continue to be
6832             trusted until they are removed from
6833             <code class="filename">named.conf</code>, an initializing key listed
6834             in a <span><strong class="command">managed-keys</strong></span> statement is only trusted
6835             <span class="emphasis"><em>once</em></span>: for as long as it takes to load the
6836             managed key database and start the RFC 5011 key maintenance
6837             process.
6838           </p>
6839 <p>
6840             The first time <span><strong class="command">named</strong></span> runs with a managed key
6841             configured in <code class="filename">named.conf</code>, it fetches the
6842             DNSKEY RRset directly from the zone apex, and validates it
6843             using the key specified in the <span><strong class="command">managed-keys</strong></span>
6844             statement.  If the DNSKEY RRset is validly signed, then it is
6845             used as the basis for a new managed keys database.
6846           </p>
6847 <p>
6848             From that point on, whenever <span><strong class="command">named</strong></span> runs, it
6849             sees the <span><strong class="command">managed-keys</strong></span> statement, checks to
6850             make sure RFC 5011 key maintenance has already been initialized
6851             for the specified domain, and if so, it simply moves on.  The
6852             key specified in the <span><strong class="command">managed-keys</strong></span> is not
6853             used to validate answers; it has been superseded by the key or
6854             keys stored in the managed keys database.
6855           </p>
6856 <p>
6857             The next time <span><strong class="command">named</strong></span> runs after a name
6858             has been <span class="emphasis"><em>removed</em></span> from the
6859             <span><strong class="command">managed-keys</strong></span> statement, the corresponding
6860             zone will be removed from the managed keys database,
6861             and RFC 5011 key maintenance will no longer be used for that
6862             domain.
6863           </p>
6864 <p>
6865             <span><strong class="command">named</strong></span> only maintains a single managed keys
6866             database; consequently, unlike <span><strong class="command">trusted-keys</strong></span>,
6867             <span><strong class="command">managed-keys</strong></span> may only be set at the top
6868             level of <code class="filename">named.conf</code>, not within a view.
6869           </p>
6870 <p>
6871             In the current implementation, the managed keys database is
6872             stored as a master-format zone file called
6873             <code class="filename">managed-keys.bind</code>.  When the key database
6874             is changed, the zone is updated.  As with any other dynamic
6875             zone, changes will be written into a journal file,
6876             <code class="filename">managed-keys.bind.jnl</code>.  They are committed
6877             to the master file as soon as possible afterward; in the case
6878             of the managed key database, this will usually occur within 30
6879             seconds.  So, whenever <span><strong class="command">named</strong></span> is using
6880             automatic key maintenance, those two files can be expected to
6881             exist in the working directory.  (For this reason among others,
6882             the working directory should be always be writable by
6883             <span><strong class="command">named</strong></span>.)
6884           </p>
6885 <p>
6886             If the <span><strong class="command">dnssec-validation</strong></span> option is
6887             set to <strong class="userinput"><code>auto</code></strong>, <span><strong class="command">named</strong></span>
6888             will automatically initialize a managed key for the
6889             root zone.  Similarly, if the <span><strong class="command">dnssec-lookaside</strong></span>
6890             option is set to <strong class="userinput"><code>auto</code></strong>,
6891             <span><strong class="command">named</strong></span> will automatically initialize
6892             a managed key for the zone <code class="literal">dlv.isc.org</code>.
6893             In both cases, the key that is used to initialize the key
6894             maintenance process is built into <span><strong class="command">named</strong></span>,
6895             and can be overridden from <span><strong class="command">bindkeys-file</strong></span>.
6896           </p>
6897 </div>
6898 <div class="sect2" lang="en">
6899 <div class="titlepage"><div><div><h3 class="title">
6900 <a name="view_statement_grammar"></a><span><strong class="command">view</strong></span> Statement Grammar</h3></div></div></div>
6901 <pre class="programlisting"><span><strong class="command">view</strong></span> <em class="replaceable"><code>view_name</code></em>
6902       [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6903       match-clients { <em class="replaceable"><code>address_match_list</code></em> };
6904       match-destinations { <em class="replaceable"><code>address_match_list</code></em> };
6905       match-recursive-only <em class="replaceable"><code>yes_or_no</code></em> ;
6906       [<span class="optional"> <em class="replaceable"><code>view_option</code></em>; ...</span>]
6907       [<span class="optional"> <em class="replaceable"><code>zone_statement</code></em>; ...</span>]
6908 };
6909 </pre>
6910 </div>
6911 <div class="sect2" lang="en">
6912 <div class="titlepage"><div><div><h3 class="title">
6913 <a name="id2591192"></a><span><strong class="command">view</strong></span> Statement Definition and Usage</h3></div></div></div>
6914 <p>
6915             The <span><strong class="command">view</strong></span> statement is a powerful
6916             feature
6917             of <acronym class="acronym">BIND</acronym> 9 that lets a name server
6918             answer a DNS query differently
6919             depending on who is asking. It is particularly useful for
6920             implementing
6921             split DNS setups without having to run multiple servers.
6922           </p>
6923 <p>
6924             Each <span><strong class="command">view</strong></span> statement defines a view
6925             of the
6926             DNS namespace that will be seen by a subset of clients.  A client
6927             matches
6928             a view if its source IP address matches the
6929             <code class="varname">address_match_list</code> of the view's
6930             <span><strong class="command">match-clients</strong></span> clause and its
6931             destination IP address matches
6932             the <code class="varname">address_match_list</code> of the
6933             view's
6934             <span><strong class="command">match-destinations</strong></span> clause.  If not
6935             specified, both
6936             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
6937             default to matching all addresses.  In addition to checking IP
6938             addresses
6939             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
6940             can also take <span><strong class="command">keys</strong></span> which provide an
6941             mechanism for the
6942             client to select the view.  A view can also be specified
6943             as <span><strong class="command">match-recursive-only</strong></span>, which
6944             means that only recursive
6945             requests from matching clients will match that view.
6946             The order of the <span><strong class="command">view</strong></span> statements is
6947             significant &#8212;
6948             a client request will be resolved in the context of the first
6949             <span><strong class="command">view</strong></span> that it matches.
6950           </p>
6951 <p>
6952             Zones defined within a <span><strong class="command">view</strong></span>
6953             statement will
6954             only be accessible to clients that match the <span><strong class="command">view</strong></span>.
6955             By defining a zone of the same name in multiple views, different
6956             zone data can be given to different clients, for example,
6957             "internal"
6958             and "external" clients in a split DNS setup.
6959           </p>
6960 <p>
6961             Many of the options given in the <span><strong class="command">options</strong></span> statement
6962             can also be used within a <span><strong class="command">view</strong></span>
6963             statement, and then
6964             apply only when resolving queries with that view.  When no
6965             view-specific
6966             value is given, the value in the <span><strong class="command">options</strong></span> statement
6967             is used as a default.  Also, zone options can have default values
6968             specified
6969             in the <span><strong class="command">view</strong></span> statement; these
6970             view-specific defaults
6971             take precedence over those in the <span><strong class="command">options</strong></span> statement.
6972           </p>
6973 <p>
6974             Views are class specific.  If no class is given, class IN
6975             is assumed.  Note that all non-IN views must contain a hint zone,
6976             since only the IN class has compiled-in default hints.
6977           </p>
6978 <p>
6979             If there are no <span><strong class="command">view</strong></span> statements in
6980             the config
6981             file, a default view that matches any client is automatically
6982             created
6983             in class IN. Any <span><strong class="command">zone</strong></span> statements
6984             specified on
6985             the top level of the configuration file are considered to be part
6986             of
6987             this default view, and the <span><strong class="command">options</strong></span>
6988             statement will
6989             apply to the default view. If any explicit <span><strong class="command">view</strong></span>
6990             statements are present, all <span><strong class="command">zone</strong></span>
6991             statements must
6992             occur inside <span><strong class="command">view</strong></span> statements.
6993           </p>
6994 <p>
6995             Here is an example of a typical split DNS setup implemented
6996             using <span><strong class="command">view</strong></span> statements:
6997           </p>
6998 <pre class="programlisting">view "internal" {
6999       // This should match our internal networks.
7000       match-clients { 10.0.0.0/8; };
7001
7002       // Provide recursive service to internal
7003       // clients only.
7004       recursion yes;
7005
7006       // Provide a complete view of the example.com
7007       // zone including addresses of internal hosts.
7008       zone "example.com" {
7009             type master;
7010             file "example-internal.db";
7011       };
7012 };
7013
7014 view "external" {
7015       // Match all clients not matched by the
7016       // previous view.
7017       match-clients { any; };
7018
7019       // Refuse recursive service to external clients.
7020       recursion no;
7021
7022       // Provide a restricted view of the example.com
7023       // zone containing only publicly accessible hosts.
7024       zone "example.com" {
7025            type master;
7026            file "example-external.db";
7027       };
7028 };
7029 </pre>
7030 </div>
7031 <div class="sect2" lang="en">
7032 <div class="titlepage"><div><div><h3 class="title">
7033 <a name="zone_statement_grammar"></a><span><strong class="command">zone</strong></span>
7034             Statement Grammar</h3></div></div></div>
7035 <pre class="programlisting"><span><strong class="command">zone</strong></span> <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7036     type master;
7037     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7038     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7039     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7040     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7041     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7042     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7043     [<span class="optional"> dnssec-loadkeys-interval <em class="replaceable"><code>number</code></em>; </span>]
7044     [<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>]
7045     [<span class="optional"> also-notify { <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ;
7046                   [<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>]
7047     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
7048     [<span class="optional"> check-mx (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
7049     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7050     [<span class="optional"> check-spf ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
7051     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7052     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
7053     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
7054     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
7055     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
7056     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
7057     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
7058     [<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>]
7059     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
7060     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7061     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
7062     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7063     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7064     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
7065     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
7066     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
7067     [<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>]
7068     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
7069     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7070     [<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>]
7071     [<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>]
7072     [<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>]
7073     [<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>]
7074     [<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>]
7075     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
7076     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
7077     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
7078     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
7079     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7080     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7081     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7082     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7083     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
7084     [<span class="optional"> auto-dnssec <code class="constant">allow</code>|<code class="constant">maintain</code>|<code class="constant">off</code>; </span>]
7085     [<span class="optional"> inline-signing <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7086     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7087     [<span class="optional"> serial-update-method <code class="constant">increment</code>|<code class="constant">unixtime</code>; </span>]
7088 };
7089
7090 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7091     type slave;
7092     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7093     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7094     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7095     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7096     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7097     [<span class="optional"> dnssec-update-mode ( <em class="replaceable"><code>maintain</code></em> | <em class="replaceable"><code>no-resign</code></em> ); </span>]
7098     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7099     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7100     [<span class="optional"> dnssec-loadkeys-interval <em class="replaceable"><code>number</code></em>; </span>]
7101     [<span class="optional"> dnssec-secure-to-insecure <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7102     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7103     [<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>
7104                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
7105                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
7106     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
7107     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
7108     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
7109     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
7110     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
7111     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
7112     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
7113     [<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>]
7114     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
7115     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7116     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
7117     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7118     [<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>
7119                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
7120                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
7121     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
7122     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
7123     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
7124     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
7125     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
7126     [<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>]
7127     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
7128     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7129     [<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>]
7130     [<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>]
7131     [<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>]
7132     [<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>]
7133     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
7134                              [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7135     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7136     [<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>]
7137     [<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>]
7138     [<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>]
7139     [<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>]
7140     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
7141     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
7142     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
7143     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
7144     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7145     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7146     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7147     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7148     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
7149     [<span class="optional"> auto-dnssec <code class="constant">allow</code>|<code class="constant">maintain</code>|<code class="constant">off</code>; </span>]
7150     [<span class="optional"> inline-signing <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7151     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7152     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7153 };
7154
7155 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7156     type hint;
7157     file <em class="replaceable"><code>string</code></em> ;
7158     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7159     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>] // Not Implemented.
7160 };
7161
7162 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7163     type stub;
7164     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7165     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7166     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
7167     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
7168     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7169     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
7170     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
7171     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
7172     [<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>]
7173     [<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>
7174                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
7175                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
7176     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
7177     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
7178     [<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>]
7179     [<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>]
7180     [<span class="optional"> transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
7181                          [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7182     [<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>]
7183     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
7184                             [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7185     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7186     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7187     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
7188     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7189     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7190     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7191     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7192     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7193 };
7194
7195 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7196     type static-stub;
7197     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7198     [<span class="optional"> server-addresses { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> ; ... </span>] }; </span>]
7199     [<span class="optional"> server-names { [<span class="optional"> <em class="replaceable"><code>namelist</code></em> </span>] }; </span>]
7200     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7201 };
7202
7203 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7204     type forward;
7205     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
7206     [<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>]
7207     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7208 };
7209
7210 zone <em class="replaceable"><code>"."</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7211     type redirect;
7212     file <em class="replaceable"><code>string</code></em> ;
7213     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
7214     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7215 };
7216
7217 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7218     type delegation-only;
7219 };
7220
7221 </pre>
7222 </div>
7223 <div class="sect2" lang="en">
7224 <div class="titlepage"><div><div><h3 class="title">
7225 <a name="id2592901"></a><span><strong class="command">zone</strong></span> Statement Definition and Usage</h3></div></div></div>
7226 <div class="sect3" lang="en">
7227 <div class="titlepage"><div><div><h4 class="title">
7228 <a name="id2592908"></a>Zone Types</h4></div></div></div>
7229 <div class="informaltable"><table border="1">
7230 <colgroup>
7231 <col>
7232 <col>
7233 </colgroup>
7234 <tbody>
7235 <tr>
7236 <td>
7237                       <p>
7238                         <code class="varname">master</code>
7239                       </p>
7240                     </td>
7241 <td>
7242                       <p>
7243                         The server has a master copy of the data
7244                         for the zone and will be able to provide authoritative
7245                         answers for
7246                         it.
7247                       </p>
7248                     </td>
7249 </tr>
7250 <tr>
7251 <td>
7252                       <p>
7253                         <code class="varname">slave</code>
7254                       </p>
7255                     </td>
7256 <td>
7257                       <p>
7258                         A slave zone is a replica of a master
7259                         zone. The <span><strong class="command">masters</strong></span> list
7260                         specifies one or more IP addresses
7261                         of master servers that the slave contacts to update
7262                         its copy of the zone.
7263                         Masters list elements can also be names of other
7264                         masters lists.
7265                         By default, transfers are made from port 53 on the
7266                         servers; this can
7267                         be changed for all servers by specifying a port number
7268                         before the
7269                         list of IP addresses, or on a per-server basis after
7270                         the IP address.
7271                         Authentication to the master can also be done with
7272                         per-server TSIG keys.
7273                         If a file is specified, then the
7274                         replica will be written to this file whenever the zone
7275                         is changed,
7276                         and reloaded from this file on a server restart. Use
7277                         of a file is
7278                         recommended, since it often speeds server startup and
7279                         eliminates
7280                         a needless waste of bandwidth. Note that for large
7281                         numbers (in the
7282                         tens or hundreds of thousands) of zones per server, it
7283                         is best to
7284                         use a two-level naming scheme for zone filenames. For
7285                         example,
7286                         a slave server for the zone <code class="literal">example.com</code> might place
7287                         the zone contents into a file called
7288                         <code class="filename">ex/example.com</code> where <code class="filename">ex/</code> is
7289                         just the first two letters of the zone name. (Most
7290                         operating systems
7291                         behave very slowly if you put 100000 files into
7292                         a single directory.)
7293                       </p>
7294                     </td>
7295 </tr>
7296 <tr>
7297 <td>
7298                       <p>
7299                         <code class="varname">stub</code>
7300                       </p>
7301                     </td>
7302 <td>
7303                       <p>
7304                         A stub zone is similar to a slave zone,
7305                         except that it replicates only the NS records of a
7306                         master zone instead
7307                         of the entire zone. Stub zones are not a standard part
7308                         of the DNS;
7309                         they are a feature specific to the <acronym class="acronym">BIND</acronym> implementation.
7310                       </p>
7311
7312                       <p>
7313                         Stub zones can be used to eliminate the need for glue
7314                         NS record
7315                         in a parent zone at the expense of maintaining a stub
7316                         zone entry and
7317                         a set of name server addresses in <code class="filename">named.conf</code>.
7318                         This usage is not recommended for new configurations,
7319                         and BIND 9
7320                         supports it only in a limited way.
7321                         In <acronym class="acronym">BIND</acronym> 4/8, zone
7322                         transfers of a parent zone
7323                         included the NS records from stub children of that
7324                         zone. This meant
7325                         that, in some cases, users could get away with
7326                         configuring child stubs
7327                         only in the master server for the parent zone. <acronym class="acronym">BIND</acronym>
7328                         9 never mixes together zone data from different zones
7329                         in this
7330                         way. Therefore, if a <acronym class="acronym">BIND</acronym> 9 master serving a parent
7331                         zone has child stub zones configured, all the slave
7332                         servers for the
7333                         parent zone also need to have the same child stub
7334                         zones
7335                         configured.
7336                       </p>
7337
7338                       <p>
7339                         Stub zones can also be used as a way of forcing the
7340                         resolution
7341                         of a given domain to use a particular set of
7342                         authoritative servers.
7343                         For example, the caching name servers on a private
7344                         network using
7345                         RFC1918 addressing may be configured with stub zones
7346                         for
7347                         <code class="literal">10.in-addr.arpa</code>
7348                         to use a set of internal name servers as the
7349                         authoritative
7350                         servers for that domain.
7351                       </p>
7352                     </td>
7353 </tr>
7354 <tr>
7355 <td>
7356                       <p>
7357                         <code class="varname">static-stub</code>
7358                       </p>
7359                     </td>
7360 <td>
7361                       <p>
7362                         A static-stub zone is similar to a stub zone
7363                         with the following exceptions:
7364                         the zone data is statically configured, rather
7365                         than transferred from a master server;
7366                         when recursion is necessary for a query that
7367                         matches a static-stub zone, the locally
7368                         configured data (nameserver names and glue addresses)
7369                         is always used even if different authoritative
7370                         information is cached.
7371                       </p>
7372                       <p>
7373                         Zone data is configured via the
7374                         <span><strong class="command">server-addresses</strong></span> and
7375                         <span><strong class="command">server-names</strong></span> zone options.
7376                       </p>
7377                       <p>
7378                         The zone data is maintained in the form of NS
7379                         and (if necessary) glue A or AAAA RRs
7380                         internally, which can be seen by dumping zone
7381                         databases by <span><strong class="command">rndc dumpdb -all</strong></span>.
7382                         The configured RRs are considered local configuration
7383                         parameters rather than public data.
7384                         Non recursive queries (i.e., those with the RD
7385                         bit off) to a static-stub zone are therefore
7386                         prohibited and will be responded with REFUSED.
7387                       </p>
7388                       <p>
7389                         Since the data is statically configured, no
7390                         zone maintenance action takes place for a static-stub
7391                         zone.
7392                         For example, there is no periodic refresh
7393                         attempt, and an incoming notify message
7394                         will be rejected with an rcode of NOTAUTH.
7395                       </p>
7396                       <p>
7397                         Each static-stub zone is configured with
7398                         internally generated NS and (if necessary)
7399                         glue A or AAAA RRs
7400                       </p>
7401                     </td>
7402 </tr>
7403 <tr>
7404 <td>
7405                       <p>
7406                         <code class="varname">forward</code>
7407                       </p>
7408                     </td>
7409 <td>
7410                       <p>
7411                         A "forward zone" is a way to configure
7412                         forwarding on a per-domain basis.  A <span><strong class="command">zone</strong></span> statement
7413                         of type <span><strong class="command">forward</strong></span> can
7414                         contain a <span><strong class="command">forward</strong></span>
7415                         and/or <span><strong class="command">forwarders</strong></span>
7416                         statement,
7417                         which will apply to queries within the domain given by
7418                         the zone
7419                         name. If no <span><strong class="command">forwarders</strong></span>
7420                         statement is present or
7421                         an empty list for <span><strong class="command">forwarders</strong></span> is given, then no
7422                         forwarding will be done for the domain, canceling the
7423                         effects of
7424                         any forwarders in the <span><strong class="command">options</strong></span> statement. Thus
7425                         if you want to use this type of zone to change the
7426                         behavior of the
7427                         global <span><strong class="command">forward</strong></span> option
7428                         (that is, "forward first"
7429                         to, then "forward only", or vice versa, but want to
7430                         use the same
7431                         servers as set globally) you need to re-specify the
7432                         global forwarders.
7433                       </p>
7434                     </td>
7435 </tr>
7436 <tr>
7437 <td>
7438                       <p>
7439                         <code class="varname">hint</code>
7440                       </p>
7441                     </td>
7442 <td>
7443                       <p>
7444                         The initial set of root name servers is
7445                         specified using a "hint zone". When the server starts
7446                         up, it uses
7447                         the root hints to find a root name server and get the
7448                         most recent
7449                         list of root name servers. If no hint zone is
7450                         specified for class
7451                         IN, the server uses a compiled-in default set of root
7452                         servers hints.
7453                         Classes other than IN have no built-in defaults hints.
7454                       </p>
7455                     </td>
7456 </tr>
7457 <tr>
7458 <td>
7459                       <p>
7460                         <code class="varname">redirect</code>
7461                       </p>
7462                     </td>
7463 <td>
7464                       <p>
7465                         Redirect zones are used to provide answers to
7466                         queries when normal resolution would result in
7467                         NXDOMAIN being returned.
7468                         Only one redirect zone is supported
7469                         per view.  <span><strong class="command">allow-query</strong></span> can be
7470                         used to restrict which clients see these answers.
7471                       </p>
7472                       <p>
7473                         If the client has requested DNSSEC records (DO=1) and
7474                         the NXDOMAIN response is signed then no substitution
7475                         will occur.
7476                       </p>
7477                       <p>
7478                         To redirect all NXDOMAIN responses to
7479                         100.100.100.2 and
7480                         2001:ffff:ffff::100.100.100.2, one would
7481                         configure a type redirect zone named ".",
7482                         with the zone file containing wildcard records
7483                         that point to the desired addresses:
7484                         <code class="literal">"*. IN A 100.100.100.2"</code>
7485                         and
7486                         <code class="literal">"*. IN AAAA 2001:ffff:ffff::100.100.100.2"</code>.
7487                       </p>
7488                       <p>
7489                         To redirect all Spanish names (under .ES) one
7490                         would use similar entries but with the names
7491                         "*.ES." instead of "*.".  To redirect all
7492                         commercial Spanish names (under COM.ES) one
7493                         would use wildcard entries called "*.COM.ES.".
7494                       </p>
7495                       <p>
7496                         Note that the redirect zone supports all
7497                         possible types; it is not limited to A and
7498                         AAAA records.
7499                       </p>
7500                       <p>
7501                         Because redirect zones are not referenced
7502                         directly by name, they are not kept in the
7503                         zone lookup table with normal master and slave
7504                         zones. Consequently, it is not currently possible
7505                         to use
7506                         <span><strong class="command">rndc reload
7507                                 <em class="replaceable"><code>zonename</code></em></strong></span>
7508                         to reload a redirect zone.  However, when using
7509                         <span><strong class="command">rndc reload</strong></span> without specifying
7510                         a zone name, redirect zones will be reloaded along
7511                         with other zones.
7512                       </p>
7513                     </td>
7514 </tr>
7515 <tr>
7516 <td>
7517                       <p>
7518                         <code class="varname">delegation-only</code>
7519                       </p>
7520                     </td>
7521 <td>
7522                       <p>
7523                         This is used to enforce the delegation-only
7524                         status of infrastructure zones (e.g. COM,
7525                         NET, ORG).  Any answer that is received
7526                         without an explicit or implicit delegation
7527                         in the authority section will be treated
7528                         as NXDOMAIN.  This does not apply to the
7529                         zone apex.  This should not be applied to
7530                         leaf zones.
7531                       </p>
7532                       <p>
7533                         <code class="varname">delegation-only</code> has no
7534                         effect on answers received from forwarders.
7535                       </p>
7536                       <p>
7537                         See caveats in <a href="Bv9ARM.ch06.html#root_delegation_only"><span><strong class="command">root-delegation-only</strong></span></a>.
7538                       </p>
7539                     </td>
7540 </tr>
7541 </tbody>
7542 </table></div>
7543 </div>
7544 <div class="sect3" lang="en">
7545 <div class="titlepage"><div><div><h4 class="title">
7546 <a name="id2593653"></a>Class</h4></div></div></div>
7547 <p>
7548               The zone's name may optionally be followed by a class. If
7549               a class is not specified, class <code class="literal">IN</code> (for <code class="varname">Internet</code>),
7550               is assumed. This is correct for the vast majority of cases.
7551             </p>
7552 <p>
7553               The <code class="literal">hesiod</code> class is
7554               named for an information service from MIT's Project Athena. It
7555               is
7556               used to share information about various systems databases, such
7557               as users, groups, printers and so on. The keyword
7558               <code class="literal">HS</code> is
7559               a synonym for hesiod.
7560             </p>
7561 <p>
7562               Another MIT development is Chaosnet, a LAN protocol created
7563               in the mid-1970s. Zone data for it can be specified with the <code class="literal">CHAOS</code> class.
7564             </p>
7565 </div>
7566 <div class="sect3" lang="en">
7567 <div class="titlepage"><div><div><h4 class="title">
7568 <a name="id2593686"></a>Zone Options</h4></div></div></div>
7569 <div class="variablelist"><dl>
7570 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
7571 <dd><p>
7572                     See the description of
7573                     <span><strong class="command">allow-notify</strong></span> in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
7574                   </p></dd>
7575 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
7576 <dd><p>
7577                     See the description of
7578                     <span><strong class="command">allow-query</strong></span> in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
7579                   </p></dd>
7580 <dt><span class="term"><span><strong class="command">allow-query-on</strong></span></span></dt>
7581 <dd><p>
7582                     See the description of
7583                     <span><strong class="command">allow-query-on</strong></span> in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
7584                   </p></dd>
7585 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
7586 <dd><p>
7587                     See the description of <span><strong class="command">allow-transfer</strong></span>
7588                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
7589                   </p></dd>
7590 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
7591 <dd><p>
7592                     See the description of <span><strong class="command">allow-update</strong></span>
7593                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
7594                   </p></dd>
7595 <dt><span class="term"><span><strong class="command">update-policy</strong></span></span></dt>
7596 <dd><p>
7597                     Specifies a "Simple Secure Update" policy. See
7598                     <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>.
7599                   </p></dd>
7600 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
7601 <dd><p>
7602                     See the description of <span><strong class="command">allow-update-forwarding</strong></span>
7603                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
7604                   </p></dd>
7605 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
7606 <dd><p>
7607                     Only meaningful if <span><strong class="command">notify</strong></span>
7608                     is
7609                     active for this zone. The set of machines that will
7610                     receive a
7611                     <code class="literal">DNS NOTIFY</code> message
7612                     for this zone is made up of all the listed name servers
7613                     (other than
7614                     the primary master) for the zone plus any IP addresses
7615                     specified
7616                     with <span><strong class="command">also-notify</strong></span>. A port
7617                     may be specified
7618                     with each <span><strong class="command">also-notify</strong></span>
7619                     address to send the notify
7620                     messages to a port other than the default of 53.
7621                     A TSIG key may also be specified to cause the
7622                     <code class="literal">NOTIFY</code> to be signed by the
7623                     given key.
7624                     <span><strong class="command">also-notify</strong></span> is not
7625                     meaningful for stub zones.
7626                     The default is the empty list.
7627                   </p></dd>
7628 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
7629 <dd><p>
7630                     This option is used to restrict the character set and
7631                     syntax of
7632                     certain domain names in master files and/or DNS responses
7633                     received from the
7634                     network.  The default varies according to zone type.  For <span><strong class="command">master</strong></span> zones the default is <span><strong class="command">fail</strong></span>.  For <span><strong class="command">slave</strong></span>
7635                     zones the default is <span><strong class="command">warn</strong></span>.
7636                     It is not implemented for <span><strong class="command">hint</strong></span> zones.
7637                   </p></dd>
7638 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
7639 <dd><p>
7640                     See the description of
7641                     <span><strong class="command">check-mx</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7642                   </p></dd>
7643 <dt><span class="term"><span><strong class="command">check-spf</strong></span></span></dt>
7644 <dd><p>
7645                     See the description of
7646                     <span><strong class="command">check-spf</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7647                   </p></dd>
7648 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
7649 <dd><p>
7650                     See the description of
7651                     <span><strong class="command">check-wildcard</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7652                   </p></dd>
7653 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
7654 <dd><p>
7655                     See the description of
7656                     <span><strong class="command">check-integrity</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7657                   </p></dd>
7658 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
7659 <dd><p>
7660                     See the description of
7661                     <span><strong class="command">check-sibling</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7662                   </p></dd>
7663 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
7664 <dd><p>
7665                     See the description of
7666                     <span><strong class="command">zero-no-soa-ttl</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7667                   </p></dd>
7668 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
7669 <dd><p>
7670                     See the description of
7671                     <span><strong class="command">update-check-ksk</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7672                   </p></dd>
7673 <dt><span class="term"><span><strong class="command">dnssec-update-mode</strong></span></span></dt>
7674 <dd><p>
7675                     See the description of
7676                     <span><strong class="command">dnssec-update-mode</strong></span> in <a href="Bv9ARM.ch06.html#options" title="options Statement Definition and
7677           Usage">the section called &#8220;<span><strong class="command">options</strong></span> Statement Definition and
7678           Usage&#8221;</a>.
7679                   </p></dd>
7680 <dt><span class="term"><span><strong class="command">dnssec-dnskey-kskonly</strong></span></span></dt>
7681 <dd><p>
7682                     See the description of
7683                     <span><strong class="command">dnssec-dnskey-kskonly</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7684                   </p></dd>
7685 <dt><span class="term"><span><strong class="command">try-tcp-refresh</strong></span></span></dt>
7686 <dd><p>
7687                     See the description of
7688                     <span><strong class="command">try-tcp-refresh</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7689                   </p></dd>
7690 <dt><span class="term"><span><strong class="command">database</strong></span></span></dt>
7691 <dd>
7692 <p>
7693                     Specify the type of database to be used for storing the
7694                     zone data.  The string following the <span><strong class="command">database</strong></span> keyword
7695                     is interpreted as a list of whitespace-delimited words.
7696                     The first word
7697                     identifies the database type, and any subsequent words are
7698                     passed
7699                     as arguments to the database to be interpreted in a way
7700                     specific
7701                     to the database type.
7702                   </p>
7703 <p>
7704                     The default is <strong class="userinput"><code>"rbt"</code></strong>, BIND 9's
7705                     native in-memory
7706                     red-black-tree database.  This database does not take
7707                     arguments.
7708                   </p>
7709 <p>
7710                     Other values are possible if additional database drivers
7711                     have been linked into the server.  Some sample drivers are
7712                     included
7713                     with the distribution but none are linked in by default.
7714                   </p>
7715 </dd>
7716 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
7717 <dd><p>
7718                     See the description of
7719                     <span><strong class="command">dialup</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7720                   </p></dd>
7721 <dt><span class="term"><span><strong class="command">delegation-only</strong></span></span></dt>
7722 <dd>
7723 <p>
7724                     The flag only applies to forward, hint and stub
7725                     zones.  If set to <strong class="userinput"><code>yes</code></strong>,
7726                     then the zone will also be treated as if it is
7727                     also a delegation-only type zone.
7728                   </p>
7729 <p>
7730                     See caveats in <a href="Bv9ARM.ch06.html#root_delegation_only"><span><strong class="command">root-delegation-only</strong></span></a>.
7731                   </p>
7732 </dd>
7733 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
7734 <dd><p>
7735                     Only meaningful if the zone has a forwarders
7736                     list. The <span><strong class="command">only</strong></span> value causes
7737                     the lookup to fail
7738                     after trying the forwarders and getting no answer, while <span><strong class="command">first</strong></span> would
7739                     allow a normal lookup to be tried.
7740                   </p></dd>
7741 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
7742 <dd><p>
7743                     Used to override the list of global forwarders.
7744                     If it is not specified in a zone of type <span><strong class="command">forward</strong></span>,
7745                     no forwarding is done for the zone and the global options are
7746                     not used.
7747                   </p></dd>
7748 <dt><span class="term"><span><strong class="command">ixfr-base</strong></span></span></dt>
7749 <dd><p>
7750                     Was used in <acronym class="acronym">BIND</acronym> 8 to
7751                     specify the name
7752                     of the transaction log (journal) file for dynamic update
7753                     and IXFR.
7754                     <acronym class="acronym">BIND</acronym> 9 ignores the option
7755                     and constructs the name of the journal
7756                     file by appending "<code class="filename">.jnl</code>"
7757                     to the name of the
7758                     zone file.
7759                   </p></dd>
7760 <dt><span class="term"><span><strong class="command">ixfr-tmp-file</strong></span></span></dt>
7761 <dd><p>
7762                     Was an undocumented option in <acronym class="acronym">BIND</acronym> 8.
7763                     Ignored in <acronym class="acronym">BIND</acronym> 9.
7764                   </p></dd>
7765 <dt><span class="term"><span><strong class="command">journal</strong></span></span></dt>
7766 <dd><p>
7767                     Allow the default journal's filename to be overridden.
7768                     The default is the zone's filename with "<code class="filename">.jnl</code>" appended.
7769                     This is applicable to <span><strong class="command">master</strong></span> and <span><strong class="command">slave</strong></span> zones.
7770                   </p></dd>
7771 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
7772 <dd><p>
7773                     See the description of
7774                     <span><strong class="command">max-journal-size</strong></span> in <a href="Bv9ARM.ch06.html#server_resource_limits" title="Server  Resource Limits">the section called &#8220;Server  Resource Limits&#8221;</a>.
7775                   </p></dd>
7776 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
7777 <dd><p>
7778                     See the description of
7779                     <span><strong class="command">max-transfer-time-in</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
7780                   </p></dd>
7781 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
7782 <dd><p>
7783                     See the description of
7784                     <span><strong class="command">max-transfer-idle-in</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
7785                   </p></dd>
7786 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
7787 <dd><p>
7788                     See the description of
7789                     <span><strong class="command">max-transfer-time-out</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
7790                   </p></dd>
7791 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
7792 <dd><p>
7793                     See the description of
7794                     <span><strong class="command">max-transfer-idle-out</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
7795                   </p></dd>
7796 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
7797 <dd><p>
7798                     See the description of
7799                     <span><strong class="command">notify</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7800                   </p></dd>
7801 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
7802 <dd><p>
7803                     See the description of
7804                     <span><strong class="command">notify-delay</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
7805                   </p></dd>
7806 <dt><span class="term"><span><strong class="command">notify-to-soa</strong></span></span></dt>
7807 <dd><p>
7808                     See the description of
7809                     <span><strong class="command">notify-to-soa</strong></span> in
7810                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7811                   </p></dd>
7812 <dt><span class="term"><span><strong class="command">pubkey</strong></span></span></dt>
7813 <dd><p>
7814                     In <acronym class="acronym">BIND</acronym> 8, this option was
7815                     intended for specifying
7816                     a public zone key for verification of signatures in DNSSEC
7817                     signed
7818                     zones when they are loaded from disk. <acronym class="acronym">BIND</acronym> 9 does not verify signatures
7819                     on load and ignores the option.
7820                   </p></dd>
7821 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
7822 <dd><p>
7823                     If <strong class="userinput"><code>yes</code></strong>, the server will keep
7824                     statistical
7825                     information for this zone, which can be dumped to the
7826                     <span><strong class="command">statistics-file</strong></span> defined in
7827                     the server options.
7828                   </p></dd>
7829 <dt><span class="term"><span><strong class="command">server-addresses</strong></span></span></dt>
7830 <dd>
7831 <p>
7832                     Only meaningful for static-stub zones.
7833                     This is a list of IP addresses to which queries
7834                     should be sent in recursive resolution for the
7835                     zone.
7836                     A non empty list for this option will internally
7837                     configure the apex NS RR with associated glue A or
7838                     AAAA RRs.
7839                   </p>
7840 <p>
7841                     For example, if "example.com" is configured as a
7842                     static-stub zone with 192.0.2.1 and 2001:db8::1234
7843                     in a <span><strong class="command">server-addresses</strong></span> option,
7844                     the following RRs will be internally configured.
7845                   </p>
7846 <pre class="programlisting">example.com. NS example.com.
7847 example.com. A 192.0.2.1
7848 example.com. AAAA 2001:db8::1234</pre>
7849 <p>
7850                     These records are internally used to resolve
7851                     names under the static-stub zone.
7852                     For instance, if the server receives a query for
7853                     "www.example.com" with the RD bit on, the server
7854                     will initiate recursive resolution and send
7855                     queries to 192.0.2.1 and/or 2001:db8::1234.
7856                   </p>
7857 </dd>
7858 <dt><span class="term"><span><strong class="command">server-names</strong></span></span></dt>
7859 <dd>
7860 <p>
7861                     Only meaningful for static-stub zones.
7862                     This is a list of domain names of nameservers that
7863                     act as authoritative servers of the static-stub
7864                     zone.
7865                     These names will be resolved to IP addresses when
7866                     <span><strong class="command">named</strong></span> needs to send queries to
7867                     these servers.
7868                     To make this supplemental resolution successful,
7869                     these names must not be a subdomain of the origin
7870                     name of static-stub zone.
7871                     That is, when "example.net" is the origin of a
7872                     static-stub zone, "ns.example" and
7873                     "master.example.com" can be specified in the
7874                     <span><strong class="command">server-names</strong></span> option, but
7875                     "ns.example.net" cannot, and will be rejected by
7876                     the configuration parser.
7877                   </p>
7878 <p>
7879                     A non empty list for this option will internally
7880                     configure the apex NS RR with the specified names.
7881                     For example, if "example.com" is configured as a
7882                     static-stub zone with "ns1.example.net" and
7883                     "ns2.example.net"
7884                     in a <span><strong class="command">server-names</strong></span> option,
7885                     the following RRs will be internally configured.
7886                   </p>
7887 <pre class="programlisting">example.com. NS ns1.example.net.
7888 example.com. NS ns2.example.net.
7889 </pre>
7890 <p>
7891                     These records are internally used to resolve
7892                     names under the static-stub zone.
7893                     For instance, if the server receives a query for
7894                     "www.example.com" with the RD bit on, the server
7895                     initiate recursive resolution,
7896                     resolve "ns1.example.net" and/or
7897                     "ns2.example.net" to IP addresses, and then send
7898                     queries to (one or more of) these addresses.
7899                   </p>
7900 </dd>
7901 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
7902 <dd><p>
7903                     See the description of
7904                     <span><strong class="command">sig-validity-interval</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
7905                   </p></dd>
7906 <dt><span class="term"><span><strong class="command">sig-signing-nodes</strong></span></span></dt>
7907 <dd><p>
7908                     See the description of
7909                     <span><strong class="command">sig-signing-nodes</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
7910                   </p></dd>
7911 <dt><span class="term"><span><strong class="command">sig-signing-signatures</strong></span></span></dt>
7912 <dd><p>
7913                     See the description of
7914                     <span><strong class="command">sig-signing-signatures</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
7915                   </p></dd>
7916 <dt><span class="term"><span><strong class="command">sig-signing-type</strong></span></span></dt>
7917 <dd><p>
7918                     See the description of
7919                     <span><strong class="command">sig-signing-type</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
7920                   </p></dd>
7921 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
7922 <dd><p>
7923                     See the description of
7924                     <span><strong class="command">transfer-source</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
7925                   </p></dd>
7926 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
7927 <dd><p>
7928                     See the description of
7929                     <span><strong class="command">transfer-source-v6</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
7930                   </p></dd>
7931 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
7932 <dd><p>
7933                     See the description of
7934                     <span><strong class="command">alt-transfer-source</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
7935                   </p></dd>
7936 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
7937 <dd><p>
7938                     See the description of
7939                     <span><strong class="command">alt-transfer-source-v6</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
7940                   </p></dd>
7941 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
7942 <dd><p>
7943                     See the description of
7944                     <span><strong class="command">use-alt-transfer-source</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
7945                   </p></dd>
7946 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
7947 <dd><p>
7948                     See the description of
7949                     <span><strong class="command">notify-source</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
7950                   </p></dd>
7951 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
7952 <dd><p>
7953                     See the description of
7954                     <span><strong class="command">notify-source-v6</strong></span> in <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
7955                   </p></dd>
7956 <dt>
7957 <span class="term"><span><strong class="command">min-refresh-time</strong></span>, </span><span class="term"><span><strong class="command">max-refresh-time</strong></span>, </span><span class="term"><span><strong class="command">min-retry-time</strong></span>, </span><span class="term"><span><strong class="command">max-retry-time</strong></span></span>
7958 </dt>
7959 <dd><p>
7960                     See the description in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
7961                   </p></dd>
7962 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
7963 <dd><p>
7964                     See the description of
7965                     <span><strong class="command">ixfr-from-differences</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7966                     (Note that the <span><strong class="command">ixfr-from-differences</strong></span>
7967                     <strong class="userinput"><code>master</code></strong> and
7968                     <strong class="userinput"><code>slave</code></strong> choices are not
7969                     available at the zone level.)
7970                   </p></dd>
7971 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
7972 <dd><p>
7973                     See the description of
7974                     <span><strong class="command">key-directory</strong></span> in <a href="Bv9ARM.ch06.html#options" title="options Statement Definition and
7975           Usage">the section called &#8220;<span><strong class="command">options</strong></span> Statement Definition and
7976           Usage&#8221;</a>.
7977                   </p></dd>
7978 <dt><span class="term"><span><strong class="command">auto-dnssec</strong></span></span></dt>
7979 <dd>
7980 <p>
7981                     Zones configured for dynamic DNS may also use this
7982                     option to allow varying levels of automatic DNSSEC key
7983                     management. There are three possible settings:
7984                   </p>
7985 <p>
7986                     <span><strong class="command">auto-dnssec allow;</strong></span> permits
7987                     keys to be updated and the zone fully re-signed
7988                     whenever the user issues the command <span><strong class="command">rndc sign
7989                     <em class="replaceable"><code>zonename</code></em></strong></span>.
7990                   </p>
7991 <p>
7992                     <span><strong class="command">auto-dnssec maintain;</strong></span> includes the
7993                     above, but also automatically adjusts the zone's DNSSEC
7994                     keys on schedule, according to the keys' timing metadata
7995                     (see <a href="man.dnssec-keygen.html" title="dnssec-keygen"><span class="refentrytitle"><span class="application">dnssec-keygen</span></span>(8)</a> and
7996                     <a href="man.dnssec-settime.html" title="dnssec-settime"><span class="refentrytitle"><span class="application">dnssec-settime</span></span>(8)</a>).  The command
7997                     <span><strong class="command">rndc sign
7998                     <em class="replaceable"><code>zonename</code></em></strong></span> causes
7999                     <span><strong class="command">named</strong></span> to load keys from the key
8000                     repository and sign the zone with all keys that are
8001                     active.
8002                     <span><strong class="command">rndc loadkeys
8003                     <em class="replaceable"><code>zonename</code></em></strong></span> causes
8004                     <span><strong class="command">named</strong></span> to load keys from the key
8005                     repository and schedule key maintenance events to occur
8006                     in the future, but it does not sign the full zone
8007                     immediately.  Note: once keys have been loaded for a
8008                     zone the first time, the repository will be searched
8009                     for changes periodically, regardless of whether
8010                     <span><strong class="command">rndc loadkeys</strong></span> is used.  The recheck
8011                     interval is defined by
8012                     <span><strong class="command">dnssec-loadkeys-interval</strong></span>.)
8013                   </p>
8014 <p>
8015                     The default setting is <span><strong class="command">auto-dnssec off</strong></span>.
8016                   </p>
8017 </dd>
8018 <dt><span class="term"><span><strong class="command">serial-update-method</strong></span></span></dt>
8019 <dd>
8020 <p>
8021                     Zones configured for dynamic DNS may use this
8022                     option to set the update method that will be used for
8023                     the zone serial number in the SOA record.
8024                   </p>
8025 <p>
8026                     With the default setting of
8027                     <span><strong class="command">serial-update-method increment;</strong></span>, the
8028                     SOA serial number will be incremented by one each time
8029                     the zone is updated.
8030                   </p>
8031 <p>
8032                     When set to
8033                     <span><strong class="command">serial-update-method unixtime;</strong></span>, the
8034                     SOA serial number will be set to the number of seconds
8035                     since the UNIX epoch, unless the serial number is
8036                     already greater than or equal to that value, in which
8037                     case it is simply incremented by one.
8038                   </p>
8039 </dd>
8040 <dt><span class="term"><span><strong class="command">inline-signing</strong></span></span></dt>
8041 <dd><p>
8042                     If <code class="literal">yes</code>, this enables
8043                     "bump in the wire" signing of a zone, where a
8044                     unsigned zone is transferred in or loaded from
8045                     disk and a signed version of the zone is served,
8046                     with possibly, a different serial number.  This
8047                     behaviour is disabled by default.
8048                   </p></dd>
8049 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
8050 <dd><p>
8051                     See the description of <span><strong class="command">multi-master</strong></span> in
8052                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8053                   </p></dd>
8054 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
8055 <dd><p>
8056                     See the description of <span><strong class="command">masterfile-format</strong></span>
8057                     in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8058                   </p></dd>
8059 <dt><span class="term"><span><strong class="command">dnssec-secure-to-insecure</strong></span></span></dt>
8060 <dd><p>
8061                     See the description of
8062                     <span><strong class="command">dnssec-secure-to-insecure</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8063                   </p></dd>
8064 </dl></div>
8065 </div>
8066 <div class="sect3" lang="en">
8067 <div class="titlepage"><div><div><h4 class="title">
8068 <a name="dynamic_update_policies"></a>Dynamic Update Policies</h4></div></div></div>
8069 <p><acronym class="acronym">BIND</acronym> 9 supports two alternative
8070               methods of granting clients the right to perform
8071               dynamic updates to a zone, configured by the
8072               <span><strong class="command">allow-update</strong></span> and
8073               <span><strong class="command">update-policy</strong></span> option, respectively.
8074             </p>
8075 <p>
8076               The <span><strong class="command">allow-update</strong></span> clause works the
8077               same way as in previous versions of <acronym class="acronym">BIND</acronym>.
8078               It grants given clients the permission to update any
8079               record of any name in the zone.
8080             </p>
8081 <p>
8082               The <span><strong class="command">update-policy</strong></span> clause
8083               allows more fine-grained control over what updates are
8084               allowed.  A set of rules is specified, where each rule
8085               either grants or denies permissions for one or more
8086               names to be updated by one or more identities.  If
8087               the dynamic update request message is signed (that is,
8088               it includes either a TSIG or SIG(0) record), the
8089               identity of the signer can be determined.
8090             </p>
8091 <p>
8092               Rules are specified in the <span><strong class="command">update-policy</strong></span>
8093               zone option, and are only meaningful for master zones.
8094               When the <span><strong class="command">update-policy</strong></span> statement
8095               is present, it is a configuration error for the
8096               <span><strong class="command">allow-update</strong></span> statement to be
8097               present.  The <span><strong class="command">update-policy</strong></span> statement
8098               only examines the signer of a message; the source
8099               address is not relevant.
8100             </p>
8101 <p>
8102               There is a pre-defined <span><strong class="command">update-policy</strong></span>
8103               rule which can be switched on with the command
8104               <span><strong class="command">update-policy local;</strong></span>.
8105               Switching on this rule in a zone causes
8106               <span><strong class="command">named</strong></span> to generate a TSIG session
8107               key and place it in a file, and to allow that key
8108               to update the zone.  (By default, the file is
8109               <code class="filename">/var/run/named/session.key</code>, the key
8110               name is "local-ddns" and the key algorithm is HMAC-SHA256,
8111               but these values are configurable with the
8112               <span><strong class="command">session-keyfile</strong></span>,
8113               <span><strong class="command">session-keyname</strong></span> and
8114               <span><strong class="command">session-keyalg</strong></span> options, respectively).
8115             </p>
8116 <p>
8117               A client running on the local system, and with appropriate
8118               permissions, may read that file and use the key to sign update
8119               requests.  The zone's update policy will be set to allow that
8120               key to change any record within the zone.  Assuming the
8121               key name is "local-ddns", this policy is equivalent to:
8122             </p>
8123 <pre class="programlisting">update-policy { grant local-ddns zonesub any; };
8124             </pre>
8125 <p>
8126               The command <span><strong class="command">nsupdate -l</strong></span> sends update
8127               requests to localhost, and signs them using the session key.
8128             </p>
8129 <p>
8130               Other rule definitions look like this:
8131             </p>
8132 <pre class="programlisting">
8133 ( <span><strong class="command">grant</strong></span> | <span><strong class="command">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>]
8134 </pre>
8135 <p>
8136               Each rule grants or denies privileges.  Once a message has
8137               successfully matched a rule, the operation is immediately
8138               granted or denied and no further rules are examined.  A rule
8139               is matched when the signer matches the identity field, the
8140               name matches the name field in accordance with the nametype
8141               field, and the type matches the types specified in the type
8142               field.
8143             </p>
8144 <p>
8145               No signer is required for <em class="replaceable"><code>tcp-self</code></em>
8146               or <em class="replaceable"><code>6to4-self</code></em> however the standard
8147               reverse mapping / prefix conversion must match the identity
8148               field.
8149             </p>
8150 <p>
8151               The identity field specifies a name or a wildcard
8152               name.  Normally, this is the name of the TSIG or
8153               SIG(0) key used to sign the update request.  When a
8154               TKEY exchange has been used to create a shared secret,
8155               the identity of the shared secret is the same as the
8156               identity of the key used to authenticate the TKEY
8157               exchange.  TKEY is also the negotiation method used
8158               by GSS-TSIG, which establishes an identity that is
8159               the Kerberos principal of the client, such as
8160               <strong class="userinput"><code>"user@host.domain"</code></strong>.  When the
8161               <em class="replaceable"><code>identity</code></em> field specifies
8162               a wildcard name, it is subject to DNS wildcard
8163               expansion, so the rule will apply to multiple identities.
8164               The <em class="replaceable"><code>identity</code></em> field must
8165               contain a fully-qualified domain name.
8166             </p>
8167 <p>
8168               For nametypes <code class="varname">krb5-self</code>,
8169               <code class="varname">ms-self</code>, <code class="varname">krb5-subdomain</code>,
8170               and <code class="varname">ms-subdomain</code> the
8171               <em class="replaceable"><code>identity</code></em> field specifies
8172               the Windows or Kerberos realm of the machine belongs to.
8173             </p>
8174 <p>
8175               The <em class="replaceable"><code>nametype</code></em> field has 13
8176               values:
8177               <code class="varname">name</code>, <code class="varname">subdomain</code>,
8178               <code class="varname">wildcard</code>, <code class="varname">self</code>,
8179               <code class="varname">selfsub</code>, <code class="varname">selfwild</code>,
8180               <code class="varname">krb5-self</code>, <code class="varname">ms-self</code>,
8181               <code class="varname">krb5-subdomain</code>,
8182               <code class="varname">ms-subdomain</code>,
8183               <code class="varname">tcp-self</code>, <code class="varname">6to4-self</code>,
8184               <code class="varname">zonesub</code>, and <code class="varname">external</code>.
8185             </p>
8186 <div class="informaltable"><table border="1">
8187 <colgroup>
8188 <col>
8189 <col>
8190 </colgroup>
8191 <tbody>
8192 <tr>
8193 <td>
8194                       <p>
8195                         <code class="varname">name</code>
8196                       </p>
8197                     </td>
8198 <td>
8199                       <p>
8200                         Exact-match semantics.  This rule matches
8201                         when the name being updated is identical
8202                         to the contents of the
8203                         <em class="replaceable"><code>name</code></em> field.
8204                       </p>
8205                     </td>
8206 </tr>
8207 <tr>
8208 <td>
8209                       <p>
8210                         <code class="varname">subdomain</code>
8211                       </p>
8212                     </td>
8213 <td>
8214                       <p>
8215                         This rule matches when the name being updated
8216                         is a subdomain of, or identical to, the
8217                         contents of the <em class="replaceable"><code>name</code></em>
8218                         field.
8219                       </p>
8220                     </td>
8221 </tr>
8222 <tr>
8223 <td>
8224                       <p>
8225                         <code class="varname">zonesub</code>
8226                       </p>
8227                     </td>
8228 <td>
8229                       <p>
8230                         This rule is similar to subdomain, except that
8231                         it matches when the name being updated is a
8232                         subdomain of the zone in which the
8233                         <span><strong class="command">update-policy</strong></span> statement
8234                         appears.  This obviates the need to type the zone
8235                         name twice, and enables the use of a standard
8236                         <span><strong class="command">update-policy</strong></span> statement in
8237                         multiple zones without modification.
8238                       </p>
8239                       <p>
8240                         When this rule is used, the
8241                         <em class="replaceable"><code>name</code></em> field is omitted.
8242                       </p>
8243                     </td>
8244 </tr>
8245 <tr>
8246 <td>
8247                       <p>
8248                         <code class="varname">wildcard</code>
8249                       </p>
8250                     </td>
8251 <td>
8252                       <p>
8253                         The <em class="replaceable"><code>name</code></em> field
8254                         is subject to DNS wildcard expansion, and
8255                         this rule matches when the name being updated
8256                         name is a valid expansion of the wildcard.
8257                       </p>
8258                     </td>
8259 </tr>
8260 <tr>
8261 <td>
8262                       <p>
8263                         <code class="varname">self</code>
8264                       </p>
8265                     </td>
8266 <td>
8267                       <p>
8268                         This rule matches when the name being updated
8269                         matches the contents of the
8270                         <em class="replaceable"><code>identity</code></em> field.
8271                         The <em class="replaceable"><code>name</code></em> field
8272                         is ignored, but should be the same as the
8273                         <em class="replaceable"><code>identity</code></em> field.
8274                         The <code class="varname">self</code> nametype is
8275                         most useful when allowing using one key per
8276                         name to update, where the key has the same
8277                         name as the name to be updated.  The
8278                         <em class="replaceable"><code>identity</code></em> would
8279                         be specified as <code class="constant">*</code> (an asterisk) in
8280                         this case.
8281                       </p>
8282                     </td>
8283 </tr>
8284 <tr>
8285 <td>
8286                       <p>
8287                         <code class="varname">selfsub</code>
8288                       </p>
8289                     </td>
8290 <td>
8291                       <p>
8292                         This rule is similar to <code class="varname">self</code>
8293                         except that subdomains of <code class="varname">self</code>
8294                         can also be updated.
8295                       </p>
8296                     </td>
8297 </tr>
8298 <tr>
8299 <td>
8300                       <p>
8301                         <code class="varname">selfwild</code>
8302                       </p>
8303                     </td>
8304 <td>
8305                       <p>
8306                         This rule is similar to <code class="varname">self</code>
8307                         except that only subdomains of
8308                         <code class="varname">self</code> can be updated.
8309                       </p>
8310                     </td>
8311 </tr>
8312 <tr>
8313 <td>
8314                       <p>
8315                         <code class="varname">ms-self</code>
8316                       </p>
8317                     </td>
8318 <td>
8319                       <p>
8320                         This rule takes a Windows machine principal
8321                         (machine$@REALM) for machine in REALM and
8322                         and converts it machine.realm allowing the machine
8323                         to update machine.realm.  The REALM to be matched
8324                         is specified in the <em class="replaceable"><code>identity</code></em>
8325                         field.
8326                       </p>
8327                     </td>
8328 </tr>
8329 <tr>
8330 <td>
8331                       <p>
8332                         <code class="varname">ms-subdomain</code>
8333                       </p>
8334                     </td>
8335 <td>
8336                       <p>
8337                         This rule takes a Windows machine principal
8338                         (machine$@REALM) for machine in REALM and
8339                         converts it to machine.realm allowing the machine
8340                         to update subdomains of machine.realm.  The REALM
8341                         to be matched is specified in the
8342                         <em class="replaceable"><code>identity</code></em> field.
8343                       </p>
8344                     </td>
8345 </tr>
8346 <tr>
8347 <td>
8348                       <p>
8349                         <code class="varname">krb5-self</code>
8350                       </p>
8351                     </td>
8352 <td>
8353                       <p>
8354                         This rule takes a Kerberos machine principal
8355                         (host/machine@REALM) for machine in REALM and
8356                         and converts it machine.realm allowing the machine
8357                         to update machine.realm.  The REALM to be matched
8358                         is specified in the <em class="replaceable"><code>identity</code></em>
8359                         field.
8360                       </p>
8361                     </td>
8362 </tr>
8363 <tr>
8364 <td>
8365                       <p>
8366                         <code class="varname">krb5-subdomain</code>
8367                       </p>
8368                     </td>
8369 <td>
8370                       <p>
8371                         This rule takes a Kerberos machine principal
8372                         (host/machine@REALM) for machine in REALM and
8373                         converts it to machine.realm allowing the machine
8374                         to update subdomains of machine.realm.  The REALM
8375                         to be matched is specified in the
8376                         <em class="replaceable"><code>identity</code></em> field.
8377                       </p>
8378                     </td>
8379 </tr>
8380 <tr>
8381 <td>
8382                       <p>
8383                         <code class="varname">tcp-self</code>
8384                       </p>
8385                     </td>
8386 <td>
8387                       <p>
8388                         Allow updates that have been sent via TCP and
8389                         for which the standard mapping from the initiating
8390                         IP address into the IN-ADDR.ARPA and IP6.ARPA
8391                         namespaces match the name to be updated.
8392                       </p>
8393                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
8394 <h3 class="title">Note</h3>
8395                         It is theoretically possible to spoof these TCP
8396                         sessions.
8397                       </div>
8398                     </td>
8399 </tr>
8400 <tr>
8401 <td>
8402                       <p>
8403                         <code class="varname">6to4-self</code>
8404                       </p>
8405                     </td>
8406 <td>
8407                       <p>
8408                         Allow the 6to4 prefix to be update by any TCP
8409                         connection from the 6to4 network or from the
8410                         corresponding IPv4 address.  This is intended
8411                         to allow NS or DNAME RRsets to be added to the
8412                         reverse tree.
8413                       </p>
8414                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
8415 <h3 class="title">Note</h3>
8416                         It is theoretically possible to spoof these TCP
8417                         sessions.
8418                       </div>
8419                     </td>
8420 </tr>
8421 <tr>
8422 <td>
8423                       <p>
8424                         <code class="varname">external</code>
8425                       </p>
8426                     </td>
8427 <td>
8428                       <p>
8429                         This rule allows <span><strong class="command">named</strong></span>
8430                         to defer the decision of whether to allow a
8431                         given update to an external daemon.
8432                       </p>
8433                       <p>
8434                         The method of communicating with the daemon is
8435                         specified in the <em class="replaceable"><code>identity</code></em>
8436                         field, the format of which is
8437                         "<code class="constant">local:</code><em class="replaceable"><code>path</code></em>",
8438                         where <em class="replaceable"><code>path</code></em> is the location
8439                         of a UNIX-domain socket.  (Currently, "local" is the
8440                         only supported mechanism.)
8441                       </p>
8442                       <p>
8443                         Requests to the external daemon are sent over the
8444                         UNIX-domain socket as datagrams with the following
8445                         format:
8446                       </p>
8447                       <pre class="programlisting">
8448    Protocol version number (4 bytes, network byte order, currently 1)
8449    Request length (4 bytes, network byte order)
8450    Signer (null-terminated string)
8451    Name (null-terminated string)
8452    TCP source address (null-terminated string)
8453    Rdata type (null-terminated string)
8454    Key (null-terminated string)
8455    TKEY token length (4 bytes, network byte order)
8456    TKEY token (remainder of packet)</pre>
8457                       <p>
8458                         The daemon replies with a four-byte value in
8459                         network byte order, containing either 0 or 1; 0
8460                         indicates that the specified update is not
8461                         permitted, and 1 indicates that it is.
8462                       </p>
8463                     </td>
8464 </tr>
8465 </tbody>
8466 </table></div>
8467 <p>
8468               In all cases, the <em class="replaceable"><code>name</code></em>
8469               field must specify a fully-qualified domain name.
8470             </p>
8471 <p>
8472               If no types are explicitly specified, this rule matches
8473               all types except RRSIG, NS, SOA, NSEC and NSEC3. Types
8474               may be specified by name, including "ANY" (ANY matches
8475               all types except NSEC and NSEC3, which can never be
8476               updated).  Note that when an attempt is made to delete
8477               all records associated with a name, the rules are
8478               checked for each existing record type.
8479             </p>
8480 </div>
8481 </div>
8482 </div>
8483 <div class="sect1" lang="en">
8484 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
8485 <a name="id2596587"></a>Zone File</h2></div></div></div>
8486 <div class="sect2" lang="en">
8487 <div class="titlepage"><div><div><h3 class="title">
8488 <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>
8489 <p>
8490             This section, largely borrowed from RFC 1034, describes the
8491             concept of a Resource Record (RR) and explains when each is used.
8492             Since the publication of RFC 1034, several new RRs have been
8493             identified
8494             and implemented in the DNS. These are also included.
8495           </p>
8496 <div class="sect3" lang="en">
8497 <div class="titlepage"><div><div><h4 class="title">
8498 <a name="id2596605"></a>Resource Records</h4></div></div></div>
8499 <p>
8500               A domain name identifies a node.  Each node has a set of
8501               resource information, which may be empty.  The set of resource
8502               information associated with a particular name is composed of
8503               separate RRs. The order of RRs in a set is not significant and
8504               need not be preserved by name servers, resolvers, or other
8505               parts of the DNS. However, sorting of multiple RRs is
8506               permitted for optimization purposes, for example, to specify
8507               that a particular nearby server be tried first. See <a href="Bv9ARM.ch06.html#the_sortlist_statement" title="The sortlist Statement">the section called &#8220;The <span><strong class="command">sortlist</strong></span> Statement&#8221;</a> and <a href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">the section called &#8220;RRset Ordering&#8221;</a>.
8508             </p>
8509 <p>
8510               The components of a Resource Record are:
8511             </p>
8512 <div class="informaltable"><table border="1">
8513 <colgroup>
8514 <col>
8515 <col>
8516 </colgroup>
8517 <tbody>
8518 <tr>
8519 <td>
8520                       <p>
8521                         owner name
8522                       </p>
8523                     </td>
8524 <td>
8525                       <p>
8526                         The domain name where the RR is found.
8527                       </p>
8528                     </td>
8529 </tr>
8530 <tr>
8531 <td>
8532                       <p>
8533                         type
8534                       </p>
8535                     </td>
8536 <td>
8537                       <p>
8538                         An encoded 16-bit value that specifies
8539                         the type of the resource record.
8540                       </p>
8541                     </td>
8542 </tr>
8543 <tr>
8544 <td>
8545                       <p>
8546                         TTL
8547                       </p>
8548                     </td>
8549 <td>
8550                       <p>
8551                         The time-to-live of the RR. This field
8552                         is a 32-bit integer in units of seconds, and is
8553                         primarily used by
8554                         resolvers when they cache RRs. The TTL describes how
8555                         long a RR can
8556                         be cached before it should be discarded.
8557                       </p>
8558                     </td>
8559 </tr>
8560 <tr>
8561 <td>
8562                       <p>
8563                         class
8564                       </p>
8565                     </td>
8566 <td>
8567                       <p>
8568                         An encoded 16-bit value that identifies
8569                         a protocol family or instance of a protocol.
8570                       </p>
8571                     </td>
8572 </tr>
8573 <tr>
8574 <td>
8575                       <p>
8576                         RDATA
8577                       </p>
8578                     </td>
8579 <td>
8580                       <p>
8581                         The resource data.  The format of the
8582                         data is type (and sometimes class) specific.
8583                       </p>
8584                     </td>
8585 </tr>
8586 </tbody>
8587 </table></div>
8588 <p>
8589               The following are <span class="emphasis"><em>types</em></span> of valid RRs:
8590             </p>
8591 <div class="informaltable"><table border="1">
8592 <colgroup>
8593 <col>
8594 <col>
8595 </colgroup>
8596 <tbody>
8597 <tr>
8598 <td>
8599                       <p>
8600                         A
8601                       </p>
8602                     </td>
8603 <td>
8604                       <p>
8605                         A host address.  In the IN class, this is a
8606                         32-bit IP address.  Described in RFC 1035.
8607                       </p>
8608                     </td>
8609 </tr>
8610 <tr>
8611 <td>
8612                       <p>
8613                         AAAA
8614                       </p>
8615                     </td>
8616 <td>
8617                       <p>
8618                         IPv6 address.  Described in RFC 1886.
8619                       </p>
8620                     </td>
8621 </tr>
8622 <tr>
8623 <td>
8624                       <p>
8625                         A6
8626                       </p>
8627                     </td>
8628 <td>
8629                       <p>
8630                         IPv6 address.  This can be a partial
8631                         address (a suffix) and an indirection to the name
8632                         where the rest of the
8633                         address (the prefix) can be found.  Experimental.
8634                         Described in RFC 2874.
8635                       </p>
8636                     </td>
8637 </tr>
8638 <tr>
8639 <td>
8640                       <p>
8641                         AFSDB
8642                       </p>
8643                     </td>
8644 <td>
8645                       <p>
8646                         Location of AFS database servers.
8647                         Experimental.  Described in RFC 1183.
8648                       </p>
8649                     </td>
8650 </tr>
8651 <tr>
8652 <td>
8653                       <p>
8654                         APL
8655                       </p>
8656                     </td>
8657 <td>
8658                       <p>
8659                         Address prefix list.  Experimental.
8660                         Described in RFC 3123.
8661                       </p>
8662                     </td>
8663 </tr>
8664 <tr>
8665 <td>
8666                       <p>
8667                         CERT
8668                       </p>
8669                     </td>
8670 <td>
8671                       <p>
8672                         Holds a digital certificate.
8673                         Described in RFC 2538.
8674                       </p>
8675                     </td>
8676 </tr>
8677 <tr>
8678 <td>
8679                       <p>
8680                         CNAME
8681                       </p>
8682                     </td>
8683 <td>
8684                       <p>
8685                         Identifies the canonical name of an alias.
8686                         Described in RFC 1035.
8687                       </p>
8688                     </td>
8689 </tr>
8690 <tr>
8691 <td>
8692                       <p>
8693                         DHCID
8694                       </p>
8695                     </td>
8696 <td>
8697                       <p>
8698                         Is used for identifying which DHCP client is
8699                         associated with this name.  Described in RFC 4701.
8700                       </p>
8701                     </td>
8702 </tr>
8703 <tr>
8704 <td>
8705                       <p>
8706                         DNAME
8707                       </p>
8708                     </td>
8709 <td>
8710                       <p>
8711                         Replaces the domain name specified with
8712                         another name to be looked up, effectively aliasing an
8713                         entire
8714                         subtree of the domain name space rather than a single
8715                         record
8716                         as in the case of the CNAME RR.
8717                         Described in RFC 2672.
8718                       </p>
8719                     </td>
8720 </tr>
8721 <tr>
8722 <td>
8723                       <p>
8724                         DNSKEY
8725                       </p>
8726                     </td>
8727 <td>
8728                       <p>
8729                         Stores a public key associated with a signed
8730                         DNS zone.  Described in RFC 4034.
8731                       </p>
8732                     </td>
8733 </tr>
8734 <tr>
8735 <td>
8736                       <p>
8737                         DS
8738                       </p>
8739                     </td>
8740 <td>
8741                       <p>
8742                         Stores the hash of a public key associated with a
8743                         signed DNS zone.  Described in RFC 4034.
8744                       </p>
8745                     </td>
8746 </tr>
8747 <tr>
8748 <td>
8749                       <p>
8750                         GPOS
8751                       </p>
8752                     </td>
8753 <td>
8754                       <p>
8755                         Specifies the global position.  Superseded by LOC.
8756                       </p>
8757                     </td>
8758 </tr>
8759 <tr>
8760 <td>
8761                       <p>
8762                         HINFO
8763                       </p>
8764                     </td>
8765 <td>
8766                       <p>
8767                         Identifies the CPU and OS used by a host.
8768                         Described in RFC 1035.
8769                       </p>
8770                     </td>
8771 </tr>
8772 <tr>
8773 <td>
8774                       <p>
8775                         IPSECKEY
8776                       </p>
8777                     </td>
8778 <td>
8779                       <p>
8780                         Provides a method for storing IPsec keying material in
8781                         DNS.  Described in RFC 4025.
8782                       </p>
8783                     </td>
8784 </tr>
8785 <tr>
8786 <td>
8787                       <p>
8788                         ISDN
8789                       </p>
8790                     </td>
8791 <td>
8792                       <p>
8793                         Representation of ISDN addresses.
8794                         Experimental.  Described in RFC 1183.
8795                       </p>
8796                     </td>
8797 </tr>
8798 <tr>
8799 <td>
8800                       <p>
8801                         KEY
8802                       </p>
8803                     </td>
8804 <td>
8805                       <p>
8806                         Stores a public key associated with a
8807                         DNS name.  Used in original DNSSEC; replaced
8808                         by DNSKEY in DNSSECbis, but still used with
8809                         SIG(0).  Described in RFCs 2535 and 2931.
8810                       </p>
8811                     </td>
8812 </tr>
8813 <tr>
8814 <td>
8815                       <p>
8816                         KX
8817                       </p>
8818                     </td>
8819 <td>
8820                       <p>
8821                         Identifies a key exchanger for this
8822                         DNS name.  Described in RFC 2230.
8823                       </p>
8824                     </td>
8825 </tr>
8826 <tr>
8827 <td>
8828                       <p>
8829                         LOC
8830                       </p>
8831                     </td>
8832 <td>
8833                       <p>
8834                         For storing GPS info.  Described in RFC 1876.
8835                         Experimental.
8836                       </p>
8837                     </td>
8838 </tr>
8839 <tr>
8840 <td>
8841                       <p>
8842                         MX
8843                       </p>
8844                     </td>
8845 <td>
8846                       <p>
8847                         Identifies a mail exchange for the domain with
8848                         a 16-bit preference value (lower is better)
8849                         followed by the host name of the mail exchange.
8850                         Described in RFC 974, RFC 1035.
8851                       </p>
8852                     </td>
8853 </tr>
8854 <tr>
8855 <td>
8856                       <p>
8857                         NAPTR
8858                       </p>
8859                     </td>
8860 <td>
8861                       <p>
8862                         Name authority pointer.  Described in RFC 2915.
8863                       </p>
8864                     </td>
8865 </tr>
8866 <tr>
8867 <td>
8868                       <p>
8869                         NSAP
8870                       </p>
8871                     </td>
8872 <td>
8873                       <p>
8874                         A network service access point.
8875                         Described in RFC 1706.
8876                       </p>
8877                     </td>
8878 </tr>
8879 <tr>
8880 <td>
8881                       <p>
8882                         NS
8883                       </p>
8884                     </td>
8885 <td>
8886                       <p>
8887                         The authoritative name server for the
8888                         domain.  Described in RFC 1035.
8889                       </p>
8890                     </td>
8891 </tr>
8892 <tr>
8893 <td>
8894                       <p>
8895                         NSEC
8896                       </p>
8897                     </td>
8898 <td>
8899                       <p>
8900                         Used in DNSSECbis to securely indicate that
8901                         RRs with an owner name in a certain name interval do
8902                         not exist in
8903                         a zone and indicate what RR types are present for an
8904                         existing name.
8905                         Described in RFC 4034.
8906                       </p>
8907                     </td>
8908 </tr>
8909 <tr>
8910 <td>
8911                       <p>
8912                         NSEC3
8913                       </p>
8914                     </td>
8915 <td>
8916                       <p>
8917                         Used in DNSSECbis to securely indicate that
8918                         RRs with an owner name in a certain name
8919                         interval do not exist in a zone and indicate
8920                         what RR types are present for an existing
8921                         name.  NSEC3 differs from NSEC in that it
8922                         prevents zone enumeration but is more
8923                         computationally expensive on both the server
8924                         and the client than NSEC.  Described in RFC
8925                         5155.
8926                       </p>
8927                     </td>
8928 </tr>
8929 <tr>
8930 <td>
8931                       <p>
8932                         NSEC3PARAM
8933                       </p>
8934                     </td>
8935 <td>
8936                       <p>
8937                         Used in DNSSECbis to tell the authoritative
8938                         server which NSEC3 chains are available to use.
8939                         Described in RFC 5155.
8940                       </p>
8941                     </td>
8942 </tr>
8943 <tr>
8944 <td>
8945                       <p>
8946                         NXT
8947                       </p>
8948                     </td>
8949 <td>
8950                       <p>
8951                         Used in DNSSEC to securely indicate that
8952                         RRs with an owner name in a certain name interval do
8953                         not exist in
8954                         a zone and indicate what RR types are present for an
8955                         existing name.
8956                         Used in original DNSSEC; replaced by NSEC in
8957                         DNSSECbis.
8958                         Described in RFC 2535.
8959                       </p>
8960                     </td>
8961 </tr>
8962 <tr>
8963 <td>
8964                       <p>
8965                         PTR
8966                       </p>
8967                     </td>
8968 <td>
8969                       <p>
8970                         A pointer to another part of the domain
8971                         name space.  Described in RFC 1035.
8972                       </p>
8973                     </td>
8974 </tr>
8975 <tr>
8976 <td>
8977                       <p>
8978                         PX
8979                       </p>
8980                     </td>
8981 <td>
8982                       <p>
8983                         Provides mappings between RFC 822 and X.400
8984                         addresses.  Described in RFC 2163.
8985                       </p>
8986                     </td>
8987 </tr>
8988 <tr>
8989 <td>
8990                       <p>
8991                         RP
8992                       </p>
8993                     </td>
8994 <td>
8995                       <p>
8996                         Information on persons responsible
8997                         for the domain.  Experimental.  Described in RFC 1183.
8998                       </p>
8999                     </td>
9000 </tr>
9001 <tr>
9002 <td>
9003                       <p>
9004                         RRSIG
9005                       </p>
9006                     </td>
9007 <td>
9008                       <p>
9009                         Contains DNSSECbis signature data.  Described
9010                         in RFC 4034.
9011                       </p>
9012                     </td>
9013 </tr>
9014 <tr>
9015 <td>
9016                       <p>
9017                         RT
9018                       </p>
9019                     </td>
9020 <td>
9021                       <p>
9022                         Route-through binding for hosts that
9023                         do not have their own direct wide area network
9024                         addresses.
9025                         Experimental.  Described in RFC 1183.
9026                       </p>
9027                     </td>
9028 </tr>
9029 <tr>
9030 <td>
9031                       <p>
9032                         SIG
9033                       </p>
9034                     </td>
9035 <td>
9036                       <p>
9037                         Contains DNSSEC signature data.  Used in
9038                         original DNSSEC; replaced by RRSIG in
9039                         DNSSECbis, but still used for SIG(0).
9040                         Described in RFCs 2535 and 2931.
9041                       </p>
9042                     </td>
9043 </tr>
9044 <tr>
9045 <td>
9046                       <p>
9047                         SOA
9048                       </p>
9049                     </td>
9050 <td>
9051                       <p>
9052                         Identifies the start of a zone of authority.
9053                         Described in RFC 1035.
9054                       </p>
9055                     </td>
9056 </tr>
9057 <tr>
9058 <td>
9059                       <p>
9060                         SPF
9061                       </p>
9062                     </td>
9063 <td>
9064                       <p>
9065                         Contains the Sender Policy Framework information
9066                         for a given email domain.  Described in RFC 4408.
9067                       </p>
9068                     </td>
9069 </tr>
9070 <tr>
9071 <td>
9072                       <p>
9073                         SRV
9074                       </p>
9075                     </td>
9076 <td>
9077                       <p>
9078                         Information about well known network
9079                         services (replaces WKS).  Described in RFC 2782.
9080                       </p>
9081                     </td>
9082 </tr>
9083 <tr>
9084 <td>
9085                       <p>
9086                         SSHFP
9087                       </p>
9088                     </td>
9089 <td>
9090                       <p>
9091                         Provides a way to securely publish a secure shell key's
9092                         fingerprint.  Described in RFC 4255.
9093                       </p>
9094                     </td>
9095 </tr>
9096 <tr>
9097 <td>
9098                       <p>
9099                         TXT
9100                       </p>
9101                     </td>
9102 <td>
9103                       <p>
9104                         Text records.  Described in RFC 1035.
9105                       </p>
9106                     </td>
9107 </tr>
9108 <tr>
9109 <td>
9110                       <p>
9111                         WKS
9112                       </p>
9113                     </td>
9114 <td>
9115                       <p>
9116                         Information about which well known
9117                         network services, such as SMTP, that a domain
9118                         supports. Historical.
9119                       </p>
9120                     </td>
9121 </tr>
9122 <tr>
9123 <td>
9124                       <p>
9125                         X25
9126                       </p>
9127                     </td>
9128 <td>
9129                       <p>
9130                         Representation of X.25 network addresses.
9131                         Experimental.  Described in RFC 1183.
9132                       </p>
9133                     </td>
9134 </tr>
9135 </tbody>
9136 </table></div>
9137 <p>
9138               The following <span class="emphasis"><em>classes</em></span> of resource records
9139               are currently valid in the DNS:
9140             </p>
9141 <div class="informaltable"><table border="1">
9142 <colgroup>
9143 <col>
9144 <col>
9145 </colgroup>
9146 <tbody>
9147 <tr>
9148 <td>
9149                       <p>
9150                         IN
9151                       </p>
9152                     </td>
9153 <td>
9154                       <p>
9155                         The Internet.
9156                       </p>
9157                     </td>
9158 </tr>
9159 <tr>
9160 <td>
9161                       <p>
9162                         CH
9163                       </p>
9164                     </td>
9165 <td>
9166                       <p>
9167                         Chaosnet, a LAN protocol created at MIT in the
9168                         mid-1970s.
9169                         Rarely used for its historical purpose, but reused for
9170                         BIND's
9171                         built-in server information zones, e.g.,
9172                         <code class="literal">version.bind</code>.
9173                       </p>
9174                     </td>
9175 </tr>
9176 <tr>
9177 <td>
9178                       <p>
9179                         HS
9180                       </p>
9181                     </td>
9182 <td>
9183                       <p>
9184                         Hesiod, an information service
9185                         developed by MIT's Project Athena. It is used to share
9186                         information
9187                         about various systems databases, such as users,
9188                         groups, printers
9189                         and so on.
9190                       </p>
9191                     </td>
9192 </tr>
9193 </tbody>
9194 </table></div>
9195 <p>
9196               The owner name is often implicit, rather than forming an
9197               integral
9198               part of the RR.  For example, many name servers internally form
9199               tree
9200               or hash structures for the name space, and chain RRs off nodes.
9201               The remaining RR parts are the fixed header (type, class, TTL)
9202               which is consistent for all RRs, and a variable part (RDATA)
9203               that
9204               fits the needs of the resource being described.
9205             </p>
9206 <p>
9207               The meaning of the TTL field is a time limit on how long an
9208               RR can be kept in a cache.  This limit does not apply to
9209               authoritative
9210               data in zones; it is also timed out, but by the refreshing
9211               policies
9212               for the zone.  The TTL is assigned by the administrator for the
9213               zone where the data originates.  While short TTLs can be used to
9214               minimize caching, and a zero TTL prohibits caching, the
9215               realities
9216               of Internet performance suggest that these times should be on
9217               the
9218               order of days for the typical host.  If a change can be
9219               anticipated,
9220               the TTL can be reduced prior to the change to minimize
9221               inconsistency
9222               during the change, and then increased back to its former value
9223               following
9224               the change.
9225             </p>
9226 <p>
9227               The data in the RDATA section of RRs is carried as a combination
9228               of binary strings and domain names.  The domain names are
9229               frequently
9230               used as "pointers" to other data in the DNS.
9231             </p>
9232 </div>
9233 <div class="sect3" lang="en">
9234 <div class="titlepage"><div><div><h4 class="title">
9235 <a name="id2598161"></a>Textual expression of RRs</h4></div></div></div>
9236 <p>
9237               RRs are represented in binary form in the packets of the DNS
9238               protocol, and are usually represented in highly encoded form
9239               when
9240               stored in a name server or resolver.  In the examples provided
9241               in
9242               RFC 1034, a style similar to that used in master files was
9243               employed
9244               in order to show the contents of RRs.  In this format, most RRs
9245               are shown on a single line, although continuation lines are
9246               possible
9247               using parentheses.
9248             </p>
9249 <p>
9250               The start of the line gives the owner of the RR.  If a line
9251               begins with a blank, then the owner is assumed to be the same as
9252               that of the previous RR.  Blank lines are often included for
9253               readability.
9254             </p>
9255 <p>
9256               Following the owner, we list the TTL, type, and class of the
9257               RR.  Class and type use the mnemonics defined above, and TTL is
9258               an integer before the type field.  In order to avoid ambiguity
9259               in
9260               parsing, type and class mnemonics are disjoint, TTLs are
9261               integers,
9262               and the type mnemonic is always last. The IN class and TTL
9263               values
9264               are often omitted from examples in the interests of clarity.
9265             </p>
9266 <p>
9267               The resource data or RDATA section of the RR are given using
9268               knowledge of the typical representation for the data.
9269             </p>
9270 <p>
9271               For example, we might show the RRs carried in a message as:
9272             </p>
9273 <div class="informaltable"><table border="1">
9274 <colgroup>
9275 <col>
9276 <col>
9277 <col>
9278 </colgroup>
9279 <tbody>
9280 <tr>
9281 <td>
9282                       <p>
9283                         <code class="literal">ISI.EDU.</code>
9284                       </p>
9285                     </td>
9286 <td>
9287                       <p>
9288                         <code class="literal">MX</code>
9289                       </p>
9290                     </td>
9291 <td>
9292                       <p>
9293                         <code class="literal">10 VENERA.ISI.EDU.</code>
9294                       </p>
9295                     </td>
9296 </tr>
9297 <tr>
9298 <td>
9299                       <p></p>
9300                     </td>
9301 <td>
9302                       <p>
9303                         <code class="literal">MX</code>
9304                       </p>
9305                     </td>
9306 <td>
9307                       <p>
9308                         <code class="literal">10 VAXA.ISI.EDU</code>
9309                       </p>
9310                     </td>
9311 </tr>
9312 <tr>
9313 <td>
9314                       <p>
9315                         <code class="literal">VENERA.ISI.EDU</code>
9316                       </p>
9317                     </td>
9318 <td>
9319                       <p>
9320                         <code class="literal">A</code>
9321                       </p>
9322                     </td>
9323 <td>
9324                       <p>
9325                         <code class="literal">128.9.0.32</code>
9326                       </p>
9327                     </td>
9328 </tr>
9329 <tr>
9330 <td>
9331                       <p></p>
9332                     </td>
9333 <td>
9334                       <p>
9335                         <code class="literal">A</code>
9336                       </p>
9337                     </td>
9338 <td>
9339                       <p>
9340                         <code class="literal">10.1.0.52</code>
9341                       </p>
9342                     </td>
9343 </tr>
9344 <tr>
9345 <td>
9346                       <p>
9347                         <code class="literal">VAXA.ISI.EDU</code>
9348                       </p>
9349                     </td>
9350 <td>
9351                       <p>
9352                         <code class="literal">A</code>
9353                       </p>
9354                     </td>
9355 <td>
9356                       <p>
9357                         <code class="literal">10.2.0.27</code>
9358                       </p>
9359                     </td>
9360 </tr>
9361 <tr>
9362 <td>
9363                       <p></p>
9364                     </td>
9365 <td>
9366                       <p>
9367                         <code class="literal">A</code>
9368                       </p>
9369                     </td>
9370 <td>
9371                       <p>
9372                         <code class="literal">128.9.0.33</code>
9373                       </p>
9374                     </td>
9375 </tr>
9376 </tbody>
9377 </table></div>
9378 <p>
9379               The MX RRs have an RDATA section which consists of a 16-bit
9380               number followed by a domain name.  The address RRs use a
9381               standard
9382               IP address format to contain a 32-bit internet address.
9383             </p>
9384 <p>
9385               The above example shows six RRs, with two RRs at each of three
9386               domain names.
9387             </p>
9388 <p>
9389               Similarly we might see:
9390             </p>
9391 <div class="informaltable"><table border="1">
9392 <colgroup>
9393 <col>
9394 <col>
9395 <col>
9396 </colgroup>
9397 <tbody>
9398 <tr>
9399 <td>
9400                       <p>
9401                         <code class="literal">XX.LCS.MIT.EDU.</code>
9402                       </p>
9403                     </td>
9404 <td>
9405                       <p>
9406                         <code class="literal">IN A</code>
9407                       </p>
9408                     </td>
9409 <td>
9410                       <p>
9411                         <code class="literal">10.0.0.44</code>
9412                       </p>
9413                     </td>
9414 </tr>
9415 <tr>
9416 <td> </td>
9417 <td>
9418                       <p>
9419                         <code class="literal">CH A</code>
9420                       </p>
9421                     </td>
9422 <td>
9423                       <p>
9424                         <code class="literal">MIT.EDU. 2420</code>
9425                       </p>
9426                     </td>
9427 </tr>
9428 </tbody>
9429 </table></div>
9430 <p>
9431               This example shows two addresses for
9432               <code class="literal">XX.LCS.MIT.EDU</code>, each of a different class.
9433             </p>
9434 </div>
9435 </div>
9436 <div class="sect2" lang="en">
9437 <div class="titlepage"><div><div><h3 class="title">
9438 <a name="id2598681"></a>Discussion of MX Records</h3></div></div></div>
9439 <p>
9440             As described above, domain servers store information as a
9441             series of resource records, each of which contains a particular
9442             piece of information about a given domain name (which is usually,
9443             but not always, a host). The simplest way to think of a RR is as
9444             a typed pair of data, a domain name matched with a relevant datum,
9445             and stored with some additional type information to help systems
9446             determine when the RR is relevant.
9447           </p>
9448 <p>
9449             MX records are used to control delivery of email. The data
9450             specified in the record is a priority and a domain name. The
9451             priority
9452             controls the order in which email delivery is attempted, with the
9453             lowest number first. If two priorities are the same, a server is
9454             chosen randomly. If no servers at a given priority are responding,
9455             the mail transport agent will fall back to the next largest
9456             priority.
9457             Priority numbers do not have any absolute meaning &#8212; they are
9458             relevant
9459             only respective to other MX records for that domain name. The
9460             domain
9461             name given is the machine to which the mail will be delivered.
9462             It <span class="emphasis"><em>must</em></span> have an associated address record
9463             (A or AAAA) &#8212; CNAME is not sufficient.
9464           </p>
9465 <p>
9466             For a given domain, if there is both a CNAME record and an
9467             MX record, the MX record is in error, and will be ignored.
9468             Instead,
9469             the mail will be delivered to the server specified in the MX
9470             record
9471             pointed to by the CNAME.
9472             For example:
9473           </p>
9474 <div class="informaltable"><table border="1">
9475 <colgroup>
9476 <col>
9477 <col>
9478 <col>
9479 <col>
9480 <col>
9481 </colgroup>
9482 <tbody>
9483 <tr>
9484 <td>
9485                     <p>
9486                       <code class="literal">example.com.</code>
9487                     </p>
9488                   </td>
9489 <td>
9490                     <p>
9491                       <code class="literal">IN</code>
9492                     </p>
9493                   </td>
9494 <td>
9495                     <p>
9496                       <code class="literal">MX</code>
9497                     </p>
9498                   </td>
9499 <td>
9500                     <p>
9501                       <code class="literal">10</code>
9502                     </p>
9503                   </td>
9504 <td>
9505                     <p>
9506                       <code class="literal">mail.example.com.</code>
9507                     </p>
9508                   </td>
9509 </tr>
9510 <tr>
9511 <td>
9512                     <p></p>
9513                   </td>
9514 <td>
9515                     <p>
9516                       <code class="literal">IN</code>
9517                     </p>
9518                   </td>
9519 <td>
9520                     <p>
9521                       <code class="literal">MX</code>
9522                     </p>
9523                   </td>
9524 <td>
9525                     <p>
9526                       <code class="literal">10</code>
9527                     </p>
9528                   </td>
9529 <td>
9530                     <p>
9531                       <code class="literal">mail2.example.com.</code>
9532                     </p>
9533                   </td>
9534 </tr>
9535 <tr>
9536 <td>
9537                     <p></p>
9538                   </td>
9539 <td>
9540                     <p>
9541                       <code class="literal">IN</code>
9542                     </p>
9543                   </td>
9544 <td>
9545                     <p>
9546                       <code class="literal">MX</code>
9547                     </p>
9548                   </td>
9549 <td>
9550                     <p>
9551                       <code class="literal">20</code>
9552                     </p>
9553                   </td>
9554 <td>
9555                     <p>
9556                       <code class="literal">mail.backup.org.</code>
9557                     </p>
9558                   </td>
9559 </tr>
9560 <tr>
9561 <td>
9562                     <p>
9563                       <code class="literal">mail.example.com.</code>
9564                     </p>
9565                   </td>
9566 <td>
9567                     <p>
9568                       <code class="literal">IN</code>
9569                     </p>
9570                   </td>
9571 <td>
9572                     <p>
9573                       <code class="literal">A</code>
9574                     </p>
9575                   </td>
9576 <td>
9577                     <p>
9578                       <code class="literal">10.0.0.1</code>
9579                     </p>
9580                   </td>
9581 <td>
9582                     <p></p>
9583                   </td>
9584 </tr>
9585 <tr>
9586 <td>
9587                     <p>
9588                       <code class="literal">mail2.example.com.</code>
9589                     </p>
9590                   </td>
9591 <td>
9592                     <p>
9593                       <code class="literal">IN</code>
9594                     </p>
9595                   </td>
9596 <td>
9597                     <p>
9598                       <code class="literal">A</code>
9599                     </p>
9600                   </td>
9601 <td>
9602                     <p>
9603                       <code class="literal">10.0.0.2</code>
9604                     </p>
9605                   </td>
9606 <td>
9607                     <p></p>
9608                   </td>
9609 </tr>
9610 </tbody>
9611 </table></div>
9612 <p>
9613             Mail delivery will be attempted to <code class="literal">mail.example.com</code> and
9614             <code class="literal">mail2.example.com</code> (in
9615             any order), and if neither of those succeed, delivery to <code class="literal">mail.backup.org</code> will
9616             be attempted.
9617           </p>
9618 </div>
9619 <div class="sect2" lang="en">
9620 <div class="titlepage"><div><div><h3 class="title">
9621 <a name="Setting_TTLs"></a>Setting TTLs</h3></div></div></div>
9622 <p>
9623             The time-to-live of the RR field is a 32-bit integer represented
9624             in units of seconds, and is primarily used by resolvers when they
9625             cache RRs. The TTL describes how long a RR can be cached before it
9626             should be discarded. The following three types of TTL are
9627             currently
9628             used in a zone file.
9629           </p>
9630 <div class="informaltable"><table border="1">
9631 <colgroup>
9632 <col>
9633 <col>
9634 </colgroup>
9635 <tbody>
9636 <tr>
9637 <td>
9638                     <p>
9639                       SOA
9640                     </p>
9641                   </td>
9642 <td>
9643                     <p>
9644                       The last field in the SOA is the negative
9645                       caching TTL. This controls how long other servers will
9646                       cache no-such-domain
9647                       (NXDOMAIN) responses from you.
9648                     </p>
9649                     <p>
9650                       The maximum time for
9651                       negative caching is 3 hours (3h).
9652                     </p>
9653                   </td>
9654 </tr>
9655 <tr>
9656 <td>
9657                     <p>
9658                       $TTL
9659                     </p>
9660                   </td>
9661 <td>
9662                     <p>
9663                       The $TTL directive at the top of the
9664                       zone file (before the SOA) gives a default TTL for every
9665                       RR without
9666                       a specific TTL set.
9667                     </p>
9668                   </td>
9669 </tr>
9670 <tr>
9671 <td>
9672                     <p>
9673                       RR TTLs
9674                     </p>
9675                   </td>
9676 <td>
9677                     <p>
9678                       Each RR can have a TTL as the second
9679                       field in the RR, which will control how long other
9680                       servers can cache it.
9681                     </p>
9682                   </td>
9683 </tr>
9684 </tbody>
9685 </table></div>
9686 <p>
9687             All of these TTLs default to units of seconds, though units
9688             can be explicitly specified, for example, <code class="literal">1h30m</code>.
9689           </p>
9690 </div>
9691 <div class="sect2" lang="en">
9692 <div class="titlepage"><div><div><h3 class="title">
9693 <a name="id2599297"></a>Inverse Mapping in IPv4</h3></div></div></div>
9694 <p>
9695             Reverse name resolution (that is, translation from IP address
9696             to name) is achieved by means of the <span class="emphasis"><em>in-addr.arpa</em></span> domain
9697             and PTR records. Entries in the in-addr.arpa domain are made in
9698             least-to-most significant order, read left to right. This is the
9699             opposite order to the way IP addresses are usually written. Thus,
9700             a machine with an IP address of 10.1.2.3 would have a
9701             corresponding
9702             in-addr.arpa name of
9703             3.2.1.10.in-addr.arpa. This name should have a PTR resource record
9704             whose data field is the name of the machine or, optionally,
9705             multiple
9706             PTR records if the machine has more than one name. For example,
9707             in the [<span class="optional">example.com</span>] domain:
9708           </p>
9709 <div class="informaltable"><table border="1">
9710 <colgroup>
9711 <col>
9712 <col>
9713 </colgroup>
9714 <tbody>
9715 <tr>
9716 <td>
9717                     <p>
9718                       <code class="literal">$ORIGIN</code>
9719                     </p>
9720                   </td>
9721 <td>
9722                     <p>
9723                       <code class="literal">2.1.10.in-addr.arpa</code>
9724                     </p>
9725                   </td>
9726 </tr>
9727 <tr>
9728 <td>
9729                     <p>
9730                       <code class="literal">3</code>
9731                     </p>
9732                   </td>
9733 <td>
9734                     <p>
9735                       <code class="literal">IN PTR foo.example.com.</code>
9736                     </p>
9737                   </td>
9738 </tr>
9739 </tbody>
9740 </table></div>
9741 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
9742 <h3 class="title">Note</h3>
9743 <p>
9744               The <span><strong class="command">$ORIGIN</strong></span> lines in the examples
9745               are for providing context to the examples only &#8212; they do not
9746               necessarily
9747               appear in the actual usage. They are only used here to indicate
9748               that the example is relative to the listed origin.
9749             </p>
9750 </div>
9751 </div>
9752 <div class="sect2" lang="en">
9753 <div class="titlepage"><div><div><h3 class="title">
9754 <a name="id2599492"></a>Other Zone File Directives</h3></div></div></div>
9755 <p>
9756             The Master File Format was initially defined in RFC 1035 and
9757             has subsequently been extended. While the Master File Format
9758             itself
9759             is class independent all records in a Master File must be of the
9760             same
9761             class.
9762           </p>
9763 <p>
9764             Master File Directives include <span><strong class="command">$ORIGIN</strong></span>, <span><strong class="command">$INCLUDE</strong></span>,
9765             and <span><strong class="command">$TTL.</strong></span>
9766           </p>
9767 <div class="sect3" lang="en">
9768 <div class="titlepage"><div><div><h4 class="title">
9769 <a name="id2599514"></a>The <span><strong class="command">@</strong></span> (at-sign)</h4></div></div></div>
9770 <p>
9771               When used in the label (or name) field, the asperand or
9772               at-sign (@) symbol represents the current origin.
9773               At the start of the zone file, it is the
9774               &lt;<code class="varname">zone_name</code>&gt; (followed by
9775               trailing dot).
9776             </p>
9777 </div>
9778 <div class="sect3" lang="en">
9779 <div class="titlepage"><div><div><h4 class="title">
9780 <a name="id2599530"></a>The <span><strong class="command">$ORIGIN</strong></span> Directive</h4></div></div></div>
9781 <p>
9782               Syntax: <span><strong class="command">$ORIGIN</strong></span>
9783               <em class="replaceable"><code>domain-name</code></em>
9784               [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
9785             </p>
9786 <p><span><strong class="command">$ORIGIN</strong></span>
9787               sets the domain name that will be appended to any
9788               unqualified records. When a zone is first read in there
9789               is an implicit <span><strong class="command">$ORIGIN</strong></span>
9790               &lt;<code class="varname">zone_name</code>&gt;<span><strong class="command">.</strong></span>
9791               (followed by trailing dot).
9792               The current <span><strong class="command">$ORIGIN</strong></span> is appended to
9793               the domain specified in the <span><strong class="command">$ORIGIN</strong></span>
9794               argument if it is not absolute.
9795             </p>
9796 <pre class="programlisting">
9797 $ORIGIN example.com.
9798 WWW     CNAME   MAIN-SERVER
9799 </pre>
9800 <p>
9801               is equivalent to
9802             </p>
9803 <pre class="programlisting">
9804 WWW.EXAMPLE.COM. CNAME MAIN-SERVER.EXAMPLE.COM.
9805 </pre>
9806 </div>
9807 <div class="sect3" lang="en">
9808 <div class="titlepage"><div><div><h4 class="title">
9809 <a name="id2599591"></a>The <span><strong class="command">$INCLUDE</strong></span> Directive</h4></div></div></div>
9810 <p>
9811               Syntax: <span><strong class="command">$INCLUDE</strong></span>
9812               <em class="replaceable"><code>filename</code></em>
9813               [<span class="optional">
9814 <em class="replaceable"><code>origin</code></em> </span>]
9815               [<span class="optional"> <em class="replaceable"><code>comment</code></em> </span>]
9816             </p>
9817 <p>
9818               Read and process the file <code class="filename">filename</code> as
9819               if it were included into the file at this point.  If <span><strong class="command">origin</strong></span> is
9820               specified the file is processed with <span><strong class="command">$ORIGIN</strong></span> set
9821               to that value, otherwise the current <span><strong class="command">$ORIGIN</strong></span> is
9822               used.
9823             </p>
9824 <p>
9825               The origin and the current domain name
9826               revert to the values they had prior to the <span><strong class="command">$INCLUDE</strong></span> once
9827               the file has been read.
9828             </p>
9829 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
9830 <h3 class="title">Note</h3>
9831 <p>
9832                 RFC 1035 specifies that the current origin should be restored
9833                 after
9834                 an <span><strong class="command">$INCLUDE</strong></span>, but it is silent
9835                 on whether the current
9836                 domain name should also be restored.  BIND 9 restores both of
9837                 them.
9838                 This could be construed as a deviation from RFC 1035, a
9839                 feature, or both.
9840               </p>
9841 </div>
9842 </div>
9843 <div class="sect3" lang="en">
9844 <div class="titlepage"><div><div><h4 class="title">
9845 <a name="id2599729"></a>The <span><strong class="command">$TTL</strong></span> Directive</h4></div></div></div>
9846 <p>
9847               Syntax: <span><strong class="command">$TTL</strong></span>
9848               <em class="replaceable"><code>default-ttl</code></em>
9849               [<span class="optional">
9850 <em class="replaceable"><code>comment</code></em> </span>]
9851             </p>
9852 <p>
9853               Set the default Time To Live (TTL) for subsequent records
9854               with undefined TTLs. Valid TTLs are of the range 0-2147483647
9855               seconds.
9856             </p>
9857 <p><span><strong class="command">$TTL</strong></span>
9858                is defined in RFC 2308.
9859             </p>
9860 </div>
9861 </div>
9862 <div class="sect2" lang="en">
9863 <div class="titlepage"><div><div><h3 class="title">
9864 <a name="id2599765"></a><acronym class="acronym">BIND</acronym> Master File Extension: the  <span><strong class="command">$GENERATE</strong></span> Directive</h3></div></div></div>
9865 <p>
9866             Syntax: <span><strong class="command">$GENERATE</strong></span>
9867             <em class="replaceable"><code>range</code></em>
9868             <em class="replaceable"><code>lhs</code></em>
9869             [<span class="optional"><em class="replaceable"><code>ttl</code></em></span>]
9870             [<span class="optional"><em class="replaceable"><code>class</code></em></span>]
9871             <em class="replaceable"><code>type</code></em>
9872             <em class="replaceable"><code>rhs</code></em>
9873             [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
9874           </p>
9875 <p><span><strong class="command">$GENERATE</strong></span>
9876             is used to create a series of resource records that only
9877             differ from each other by an
9878             iterator. <span><strong class="command">$GENERATE</strong></span> can be used to
9879             easily generate the sets of records required to support
9880             sub /24 reverse delegations described in RFC 2317:
9881             Classless IN-ADDR.ARPA delegation.
9882           </p>
9883 <pre class="programlisting">$ORIGIN 0.0.192.IN-ADDR.ARPA.
9884 $GENERATE 1-2 @ NS SERVER$.EXAMPLE.
9885 $GENERATE 1-127 $ CNAME $.0</pre>
9886 <p>
9887             is equivalent to
9888           </p>
9889 <pre class="programlisting">0.0.0.192.IN-ADDR.ARPA. NS SERVER1.EXAMPLE.
9890 0.0.0.192.IN-ADDR.ARPA. NS SERVER2.EXAMPLE.
9891 1.0.0.192.IN-ADDR.ARPA. CNAME 1.0.0.0.192.IN-ADDR.ARPA.
9892 2.0.0.192.IN-ADDR.ARPA. CNAME 2.0.0.0.192.IN-ADDR.ARPA.
9893 ...
9894 127.0.0.192.IN-ADDR.ARPA. CNAME 127.0.0.0.192.IN-ADDR.ARPA.
9895 </pre>
9896 <p>
9897             Generate a set of A and MX records.  Note the MX's right hand
9898             side is a quoted string.  The quotes will be stripped when the
9899             right hand side is processed.
9900            </p>
9901 <pre class="programlisting">
9902 $ORIGIN EXAMPLE.
9903 $GENERATE 1-127 HOST-$ A 1.2.3.$
9904 $GENERATE 1-127 HOST-$ MX "0 ."</pre>
9905 <p>
9906             is equivalent to
9907           </p>
9908 <pre class="programlisting">HOST-1.EXAMPLE.   A  1.2.3.1
9909 HOST-1.EXAMPLE.   MX 0 .
9910 HOST-2.EXAMPLE.   A  1.2.3.2
9911 HOST-2.EXAMPLE.   MX 0 .
9912 HOST-3.EXAMPLE.   A  1.2.3.3
9913 HOST-3.EXAMPLE.   MX 0 .
9914 ...
9915 HOST-127.EXAMPLE. A  1.2.3.127
9916 HOST-127.EXAMPLE. MX 0 .
9917 </pre>
9918 <div class="informaltable"><table border="1">
9919 <colgroup>
9920 <col>
9921 <col>
9922 </colgroup>
9923 <tbody>
9924 <tr>
9925 <td>
9926                     <p><span><strong class="command">range</strong></span></p>
9927                   </td>
9928 <td>
9929                     <p>
9930                       This can be one of two forms: start-stop
9931                       or start-stop/step. If the first form is used, then step
9932                       is set to 1. start, stop and step must be positive
9933                       integers between 0 and (2^31)-1. start must not be
9934                       larger than stop.
9935                     </p>
9936                   </td>
9937 </tr>
9938 <tr>
9939 <td>
9940                     <p><span><strong class="command">lhs</strong></span></p>
9941                   </td>
9942 <td>
9943                     <p>This
9944                       describes the owner name of the resource records
9945                       to be created.  Any single <span><strong class="command">$</strong></span>
9946                       (dollar sign)
9947                       symbols within the <span><strong class="command">lhs</strong></span> string
9948                       are replaced by the iterator value.
9949
9950                       To get a $ in the output, you need to escape the
9951                       <span><strong class="command">$</strong></span> using a backslash
9952                       <span><strong class="command">\</strong></span>,
9953                       e.g. <span><strong class="command">\$</strong></span>. The
9954                       <span><strong class="command">$</strong></span> may optionally be followed
9955                       by modifiers which change the offset from the
9956                       iterator, field width and base.
9957
9958                       Modifiers are introduced by a
9959                       <span><strong class="command">{</strong></span> (left brace) immediately following the
9960                       <span><strong class="command">$</strong></span> as
9961                       <span><strong class="command">${offset[,width[,base]]}</strong></span>.
9962                       For example, <span><strong class="command">${-20,3,d}</strong></span>
9963                       subtracts 20 from the current value, prints the
9964                       result as a decimal in a zero-padded field of
9965                       width 3.
9966
9967                       Available output forms are decimal
9968                       (<span><strong class="command">d</strong></span>), octal
9969                       (<span><strong class="command">o</strong></span>), hexadecimal
9970                       (<span><strong class="command">x</strong></span> or <span><strong class="command">X</strong></span>
9971                       for uppercase) and nibble
9972                       (<span><strong class="command">n</strong></span> or <span><strong class="command">N</strong></span>\
9973                       for uppercase).  The default modifier is
9974                       <span><strong class="command">${0,0,d}</strong></span>.  If the
9975                       <span><strong class="command">lhs</strong></span> is not absolute, the
9976                       current <span><strong class="command">$ORIGIN</strong></span> is appended
9977                       to the name.
9978                     </p>
9979                     <p>
9980                       In nibble mode the value will be treated as
9981                       if it was a reversed hexadecimal string
9982                       with each hexadecimal digit as a separate
9983                       label.  The width field includes the label
9984                       separator.
9985                     </p>
9986                     <p>
9987                       For compatibility with earlier versions,
9988                       <span><strong class="command">$$</strong></span> is still recognized as
9989                       indicating a literal $ in the output.
9990                     </p>
9991                   </td>
9992 </tr>
9993 <tr>
9994 <td>
9995                     <p><span><strong class="command">ttl</strong></span></p>
9996                   </td>
9997 <td>
9998                     <p>
9999                       Specifies the time-to-live of the generated records. If
10000                       not specified this will be inherited using the
10001                       normal TTL inheritance rules.
10002                     </p>
10003                     <p><span><strong class="command">class</strong></span>
10004                       and <span><strong class="command">ttl</strong></span> can be
10005                       entered in either order.
10006                     </p>
10007                   </td>
10008 </tr>
10009 <tr>
10010 <td>
10011                     <p><span><strong class="command">class</strong></span></p>
10012                   </td>
10013 <td>
10014                     <p>
10015                       Specifies the class of the generated records.
10016                       This must match the zone class if it is
10017                       specified.
10018                     </p>
10019                     <p><span><strong class="command">class</strong></span>
10020                       and <span><strong class="command">ttl</strong></span> can be
10021                       entered in either order.
10022                     </p>
10023                   </td>
10024 </tr>
10025 <tr>
10026 <td>
10027                     <p><span><strong class="command">type</strong></span></p>
10028                   </td>
10029 <td>
10030                     <p>
10031                       Any valid type.
10032                     </p>
10033                   </td>
10034 </tr>
10035 <tr>
10036 <td>
10037                     <p><span><strong class="command">rhs</strong></span></p>
10038                   </td>
10039 <td>
10040                     <p>
10041                       <span><strong class="command">rhs</strong></span>, optionally, quoted string.
10042                     </p>
10043                   </td>
10044 </tr>
10045 </tbody>
10046 </table></div>
10047 <p>
10048             The <span><strong class="command">$GENERATE</strong></span> directive is a <acronym class="acronym">BIND</acronym> extension
10049             and not part of the standard zone file format.
10050           </p>
10051 <p>
10052             BIND 8 does not support the optional TTL and CLASS fields.
10053           </p>
10054 </div>
10055 <div class="sect2" lang="en">
10056 <div class="titlepage"><div><div><h3 class="title">
10057 <a name="zonefile_format"></a>Additional File Formats</h3></div></div></div>
10058 <p>
10059             In addition to the standard textual format, BIND 9
10060             supports the ability to read or dump to zone files in
10061             other formats.  The <code class="constant">raw</code> format is
10062             currently available as an additional format.  It is a
10063             binary format representing BIND 9's internal data
10064             structure directly, thereby remarkably improving the
10065             loading time.
10066           </p>
10067 <p>
10068             For a primary server, a zone file in the
10069             <code class="constant">raw</code> format is expected to be
10070             generated from a textual zone file by the
10071             <span><strong class="command">named-compilezone</strong></span> command.  For a
10072             secondary server or for a dynamic zone, it is automatically
10073             generated (if this format is specified by the
10074             <span><strong class="command">masterfile-format</strong></span> option) when
10075             <span><strong class="command">named</strong></span> dumps the zone contents after
10076             zone transfer or when applying prior updates.
10077           </p>
10078 <p>
10079             If a zone file in a binary format needs manual modification,
10080             it first must be converted to a textual form by the
10081             <span><strong class="command">named-compilezone</strong></span> command.  All
10082             necessary modification should go to the text file, which
10083             should then be converted to the binary form by the
10084             <span><strong class="command">named-compilezone</strong></span> command again.
10085           </p>
10086 <p>
10087              Although the <code class="constant">raw</code> format uses the
10088              network byte order and avoids architecture-dependent
10089              data alignment so that it is as much portable as
10090              possible, it is primarily expected to be used inside
10091              the same single system.  In order to export a zone
10092              file in the <code class="constant">raw</code> format or make a
10093              portable backup of the file, it is recommended to
10094              convert the file to the standard textual representation.
10095           </p>
10096 </div>
10097 </div>
10098 <div class="sect1" lang="en">
10099 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
10100 <a name="statistics"></a>BIND9 Statistics</h2></div></div></div>
10101 <p>
10102           <acronym class="acronym">BIND</acronym> 9 maintains lots of statistics
10103           information and provides several interfaces for users to
10104           get access to the statistics.
10105           The available statistics include all statistics counters
10106           that were available in <acronym class="acronym">BIND</acronym> 8 and
10107           are meaningful in <acronym class="acronym">BIND</acronym> 9,
10108           and other information that is considered useful.
10109         </p>
10110 <p>
10111           The statistics information is categorized into the following
10112           sections.
10113         </p>
10114 <div class="informaltable"><table border="1">
10115 <colgroup>
10116 <col>
10117 <col>
10118 </colgroup>
10119 <tbody>
10120 <tr>
10121 <td>
10122                   <p>Incoming Requests</p>
10123                 </td>
10124 <td>
10125                   <p>
10126                     The number of incoming DNS requests for each OPCODE.
10127                   </p>
10128                 </td>
10129 </tr>
10130 <tr>
10131 <td>
10132                   <p>Incoming Queries</p>
10133                 </td>
10134 <td>
10135                   <p>
10136                     The number of incoming queries for each RR type.
10137                   </p>
10138                 </td>
10139 </tr>
10140 <tr>
10141 <td>
10142                   <p>Outgoing Queries</p>
10143                 </td>
10144 <td>
10145                   <p>
10146                     The number of outgoing queries for each RR
10147                     type sent from the internal resolver.
10148                     Maintained per view.
10149                   </p>
10150                 </td>
10151 </tr>
10152 <tr>
10153 <td>
10154                   <p>Name Server Statistics</p>
10155                 </td>
10156 <td>
10157                   <p>
10158                     Statistics counters about incoming request processing.
10159                   </p>
10160                 </td>
10161 </tr>
10162 <tr>
10163 <td>
10164                   <p>Zone Maintenance Statistics</p>
10165                 </td>
10166 <td>
10167                   <p>
10168                     Statistics counters regarding zone maintenance
10169                     operations such as zone transfers.
10170                   </p>
10171                 </td>
10172 </tr>
10173 <tr>
10174 <td>
10175                   <p>Resolver Statistics</p>
10176                 </td>
10177 <td>
10178                   <p>
10179                     Statistics counters about name resolution
10180                     performed in the internal resolver.
10181                     Maintained per view.
10182                   </p>
10183                 </td>
10184 </tr>
10185 <tr>
10186 <td>
10187                   <p>Cache DB RRsets</p>
10188                 </td>
10189 <td>
10190                   <p>
10191                     The number of RRsets per RR type and nonexistent
10192                     names stored in the cache database.
10193                     If the exclamation mark (!) is printed for a RR
10194                     type, it means that particular type of RRset is
10195                     known to be nonexistent (this is also known as
10196                     "NXRRSET").
10197                     Maintained per view.
10198                   </p>
10199                 </td>
10200 </tr>
10201 <tr>
10202 <td>
10203                   <p>Socket I/O Statistics</p>
10204                 </td>
10205 <td>
10206                   <p>
10207                     Statistics counters about network related events.
10208                   </p>
10209                 </td>
10210 </tr>
10211 </tbody>
10212 </table></div>
10213 <p>
10214           A subset of Name Server Statistics is collected and shown
10215           per zone for which the server has the authority when
10216           <span><strong class="command">zone-statistics</strong></span> is set to
10217           <strong class="userinput"><code>yes</code></strong>.
10218           These statistics counters are shown with their zone and view
10219           names.
10220           In some cases the view names are omitted for the default view.
10221         </p>
10222 <p>
10223           There are currently two user interfaces to get access to the
10224           statistics.
10225           One is in the plain text format dumped to the file specified
10226           by the <span><strong class="command">statistics-file</strong></span> configuration option.
10227           The other is remotely accessible via a statistics channel
10228           when the <span><strong class="command">statistics-channels</strong></span> statement
10229           is specified in the configuration file
10230           (see <a href="Bv9ARM.ch06.html#statschannels" title="statistics-channels Statement Grammar">the section called &#8220;<span><strong class="command">statistics-channels</strong></span> Statement Grammar&#8221;</a>.)
10231         </p>
10232 <div class="sect3" lang="en">
10233 <div class="titlepage"><div><div><h4 class="title">
10234 <a name="statsfile"></a>The Statistics File</h4></div></div></div>
10235 <p>
10236             The text format statistics dump begins with a line, like:
10237           </p>
10238 <p>
10239             <span><strong class="command">+++ Statistics Dump +++ (973798949)</strong></span>
10240           </p>
10241 <p>
10242             The number in parentheses is a standard
10243             Unix-style timestamp, measured as seconds since January 1, 1970.
10244
10245             Following
10246             that line is a set of statistics information, which is categorized
10247             as described above.
10248             Each section begins with a line, like:
10249           </p>
10250 <p>
10251             <span><strong class="command">++ Name Server Statistics ++</strong></span>
10252           </p>
10253 <p>
10254             Each section consists of lines, each containing the statistics
10255             counter value followed by its textual description.
10256             See below for available counters.
10257             For brevity, counters that have a value of 0 are not shown
10258             in the statistics file.
10259           </p>
10260 <p>
10261             The statistics dump ends with the line where the
10262             number is identical to the number in the beginning line; for example:
10263           </p>
10264 <p>
10265             <span><strong class="command">--- Statistics Dump --- (973798949)</strong></span>
10266           </p>
10267 </div>
10268 <div class="sect2" lang="en">
10269 <div class="titlepage"><div><div><h3 class="title">
10270 <a name="statistics_counters"></a>Statistics Counters</h3></div></div></div>
10271 <p>
10272             The following tables summarize statistics counters that
10273             <acronym class="acronym">BIND</acronym> 9 provides.
10274             For each row of the tables, the leftmost column is the
10275             abbreviated symbol name of that counter.
10276             These symbols are shown in the statistics information
10277             accessed via an HTTP statistics channel.
10278             The rightmost column gives the description of the counter,
10279             which is also shown in the statistics file
10280             (but, in this document, possibly with slight modification
10281             for better readability).
10282             Additional notes may also be provided in this column.
10283             When a middle column exists between these two columns,
10284             it gives the corresponding counter name of the
10285             <acronym class="acronym">BIND</acronym> 8 statistics, if applicable.
10286           </p>
10287 <div class="sect3" lang="en">
10288 <div class="titlepage"><div><div><h4 class="title">
10289 <a name="id2600855"></a>Name Server Statistics Counters</h4></div></div></div>
10290 <div class="informaltable"><table border="1">
10291 <colgroup>
10292 <col>
10293 <col>
10294 <col>
10295 </colgroup>
10296 <tbody>
10297 <tr>
10298 <td>
10299                       <p>
10300                         <span class="emphasis"><em>Symbol</em></span>
10301                       </p>
10302                     </td>
10303 <td>
10304                       <p>
10305                         <span class="emphasis"><em>BIND8 Symbol</em></span>
10306                       </p>
10307                     </td>
10308 <td>
10309                       <p>
10310                         <span class="emphasis"><em>Description</em></span>
10311                       </p>
10312                     </td>
10313 </tr>
10314 <tr>
10315 <td>
10316                       <p><span><strong class="command">Requestv4</strong></span></p>
10317                     </td>
10318 <td>
10319                       <p><span><strong class="command">RQ</strong></span></p>
10320                     </td>
10321 <td>
10322                       <p>
10323                         IPv4 requests received.
10324                         Note: this also counts non query requests.
10325                       </p>
10326                     </td>
10327 </tr>
10328 <tr>
10329 <td>
10330                       <p><span><strong class="command">Requestv6</strong></span></p>
10331                     </td>
10332 <td>
10333                       <p><span><strong class="command">RQ</strong></span></p>
10334                     </td>
10335 <td>
10336                       <p>
10337                         IPv6 requests received.
10338                         Note: this also counts non query requests.
10339                       </p>
10340                     </td>
10341 </tr>
10342 <tr>
10343 <td>
10344                       <p><span><strong class="command">ReqEdns0</strong></span></p>
10345                     </td>
10346 <td>
10347                       <p><span><strong class="command"></strong></span></p>
10348                     </td>
10349 <td>
10350                       <p>
10351                         Requests with EDNS(0) received.
10352                       </p>
10353                     </td>
10354 </tr>
10355 <tr>
10356 <td>
10357                       <p><span><strong class="command">ReqBadEDNSVer</strong></span></p>
10358                     </td>
10359 <td>
10360                       <p><span><strong class="command"></strong></span></p>
10361                     </td>
10362 <td>
10363                       <p>
10364                         Requests with unsupported EDNS version received.
10365                       </p>
10366                     </td>
10367 </tr>
10368 <tr>
10369 <td>
10370                       <p><span><strong class="command">ReqTSIG</strong></span></p>
10371                     </td>
10372 <td>
10373                       <p><span><strong class="command"></strong></span></p>
10374                     </td>
10375 <td>
10376                       <p>
10377                         Requests with TSIG received.
10378                       </p>
10379                     </td>
10380 </tr>
10381 <tr>
10382 <td>
10383                       <p><span><strong class="command">ReqSIG0</strong></span></p>
10384                     </td>
10385 <td>
10386                       <p><span><strong class="command"></strong></span></p>
10387                     </td>
10388 <td>
10389                       <p>
10390                         Requests with SIG(0) received.
10391                       </p>
10392                     </td>
10393 </tr>
10394 <tr>
10395 <td>
10396                       <p><span><strong class="command">ReqBadSIG</strong></span></p>
10397                     </td>
10398 <td>
10399                       <p><span><strong class="command"></strong></span></p>
10400                     </td>
10401 <td>
10402                       <p>
10403                         Requests with invalid (TSIG or SIG(0)) signature.
10404                       </p>
10405                     </td>
10406 </tr>
10407 <tr>
10408 <td>
10409                       <p><span><strong class="command">ReqTCP</strong></span></p>
10410                     </td>
10411 <td>
10412                       <p><span><strong class="command">RTCP</strong></span></p>
10413                     </td>
10414 <td>
10415                       <p>
10416                         TCP requests received.
10417                       </p>
10418                     </td>
10419 </tr>
10420 <tr>
10421 <td>
10422                       <p><span><strong class="command">AuthQryRej</strong></span></p>
10423                     </td>
10424 <td>
10425                       <p><span><strong class="command">RUQ</strong></span></p>
10426                     </td>
10427 <td>
10428                       <p>
10429                         Authoritative (non recursive) queries rejected.
10430                       </p>
10431                     </td>
10432 </tr>
10433 <tr>
10434 <td>
10435                       <p><span><strong class="command">RecQryRej</strong></span></p>
10436                     </td>
10437 <td>
10438                       <p><span><strong class="command">RURQ</strong></span></p>
10439                     </td>
10440 <td>
10441                       <p>
10442                         Recursive queries rejected.
10443                       </p>
10444                     </td>
10445 </tr>
10446 <tr>
10447 <td>
10448                       <p><span><strong class="command">XfrRej</strong></span></p>
10449                     </td>
10450 <td>
10451                       <p><span><strong class="command">RUXFR</strong></span></p>
10452                     </td>
10453 <td>
10454                       <p>
10455                         Zone transfer requests rejected.
10456                       </p>
10457                     </td>
10458 </tr>
10459 <tr>
10460 <td>
10461                       <p><span><strong class="command">UpdateRej</strong></span></p>
10462                     </td>
10463 <td>
10464                       <p><span><strong class="command">RUUpd</strong></span></p>
10465                     </td>
10466 <td>
10467                       <p>
10468                         Dynamic update requests rejected.
10469                       </p>
10470                     </td>
10471 </tr>
10472 <tr>
10473 <td>
10474                       <p><span><strong class="command">Response</strong></span></p>
10475                     </td>
10476 <td>
10477                       <p><span><strong class="command">SAns</strong></span></p>
10478                     </td>
10479 <td>
10480                       <p>
10481                         Responses sent.
10482                       </p>
10483                     </td>
10484 </tr>
10485 <tr>
10486 <td>
10487                       <p><span><strong class="command">RespTruncated</strong></span></p>
10488                     </td>
10489 <td>
10490                       <p><span><strong class="command"></strong></span></p>
10491                     </td>
10492 <td>
10493                       <p>
10494                         Truncated responses sent.
10495                       </p>
10496                     </td>
10497 </tr>
10498 <tr>
10499 <td>
10500                       <p><span><strong class="command">RespEDNS0</strong></span></p>
10501                     </td>
10502 <td>
10503                       <p><span><strong class="command"></strong></span></p>
10504                     </td>
10505 <td>
10506                       <p>
10507                         Responses with EDNS(0) sent.
10508                       </p>
10509                     </td>
10510 </tr>
10511 <tr>
10512 <td>
10513                       <p><span><strong class="command">RespTSIG</strong></span></p>
10514                     </td>
10515 <td>
10516                       <p><span><strong class="command"></strong></span></p>
10517                     </td>
10518 <td>
10519                       <p>
10520                         Responses with TSIG sent.
10521                       </p>
10522                     </td>
10523 </tr>
10524 <tr>
10525 <td>
10526                       <p><span><strong class="command">RespSIG0</strong></span></p>
10527                     </td>
10528 <td>
10529                       <p><span><strong class="command"></strong></span></p>
10530                     </td>
10531 <td>
10532                       <p>
10533                         Responses with SIG(0) sent.
10534                       </p>
10535                     </td>
10536 </tr>
10537 <tr>
10538 <td>
10539                       <p><span><strong class="command">QrySuccess</strong></span></p>
10540                     </td>
10541 <td>
10542                       <p><span><strong class="command"></strong></span></p>
10543                     </td>
10544 <td>
10545                       <p>
10546                         Queries resulted in a successful answer.
10547                         This means the query which returns a NOERROR response
10548                         with at least one answer RR.
10549                         This corresponds to the
10550                         <span><strong class="command">success</strong></span> counter
10551                         of previous versions of
10552                         <acronym class="acronym">BIND</acronym> 9.
10553                       </p>
10554                     </td>
10555 </tr>
10556 <tr>
10557 <td>
10558                       <p><span><strong class="command">QryAuthAns</strong></span></p>
10559                     </td>
10560 <td>
10561                       <p><span><strong class="command"></strong></span></p>
10562                     </td>
10563 <td>
10564                       <p>
10565                         Queries resulted in authoritative answer.
10566                       </p>
10567                     </td>
10568 </tr>
10569 <tr>
10570 <td>
10571                       <p><span><strong class="command">QryNoauthAns</strong></span></p>
10572                     </td>
10573 <td>
10574                       <p><span><strong class="command">SNaAns</strong></span></p>
10575                     </td>
10576 <td>
10577                       <p>
10578                         Queries resulted in non authoritative answer.
10579                       </p>
10580                     </td>
10581 </tr>
10582 <tr>
10583 <td>
10584                       <p><span><strong class="command">QryReferral</strong></span></p>
10585                     </td>
10586 <td>
10587                       <p><span><strong class="command"></strong></span></p>
10588                     </td>
10589 <td>
10590                       <p>
10591                         Queries resulted in referral answer.
10592                         This corresponds to the
10593                         <span><strong class="command">referral</strong></span> counter
10594                         of previous versions of
10595                         <acronym class="acronym">BIND</acronym> 9.
10596                       </p>
10597                     </td>
10598 </tr>
10599 <tr>
10600 <td>
10601                       <p><span><strong class="command">QryNxrrset</strong></span></p>
10602                     </td>
10603 <td>
10604                       <p><span><strong class="command"></strong></span></p>
10605                     </td>
10606 <td>
10607                       <p>
10608                         Queries resulted in NOERROR responses with no data.
10609                         This corresponds to the
10610                         <span><strong class="command">nxrrset</strong></span> counter
10611                         of previous versions of
10612                         <acronym class="acronym">BIND</acronym> 9.
10613                       </p>
10614                     </td>
10615 </tr>
10616 <tr>
10617 <td>
10618                       <p><span><strong class="command">QrySERVFAIL</strong></span></p>
10619                     </td>
10620 <td>
10621                       <p><span><strong class="command">SFail</strong></span></p>
10622                     </td>
10623 <td>
10624                       <p>
10625                         Queries resulted in SERVFAIL.
10626                       </p>
10627                     </td>
10628 </tr>
10629 <tr>
10630 <td>
10631                       <p><span><strong class="command">QryFORMERR</strong></span></p>
10632                     </td>
10633 <td>
10634                       <p><span><strong class="command">SFErr</strong></span></p>
10635                     </td>
10636 <td>
10637                       <p>
10638                         Queries resulted in FORMERR.
10639                       </p>
10640                     </td>
10641 </tr>
10642 <tr>
10643 <td>
10644                       <p><span><strong class="command">QryNXDOMAIN</strong></span></p>
10645                     </td>
10646 <td>
10647                       <p><span><strong class="command">SNXD</strong></span></p>
10648                     </td>
10649 <td>
10650                       <p>
10651                         Queries resulted in NXDOMAIN.
10652                         This corresponds to the
10653                         <span><strong class="command">nxdomain</strong></span> counter
10654                         of previous versions of
10655                         <acronym class="acronym">BIND</acronym> 9.
10656                       </p>
10657                     </td>
10658 </tr>
10659 <tr>
10660 <td>
10661                       <p><span><strong class="command">QryRecursion</strong></span></p>
10662                     </td>
10663 <td>
10664                       <p><span><strong class="command">RFwdQ</strong></span></p>
10665                     </td>
10666 <td>
10667                       <p>
10668                         Queries which caused the server
10669                         to perform recursion in order to find the final answer.
10670                         This corresponds to the
10671                         <span><strong class="command">recursion</strong></span> counter
10672                         of previous versions of
10673                         <acronym class="acronym">BIND</acronym> 9.
10674                       </p>
10675                     </td>
10676 </tr>
10677 <tr>
10678 <td>
10679                       <p><span><strong class="command">QryDuplicate</strong></span></p>
10680                     </td>
10681 <td>
10682                       <p><span><strong class="command">RDupQ</strong></span></p>
10683                     </td>
10684 <td>
10685                       <p>
10686                         Queries which the server attempted to
10687                         recurse but discovered an existing query with the same
10688                         IP address, port, query ID, name, type and class
10689                         already being processed.
10690                         This corresponds to the
10691                         <span><strong class="command">duplicate</strong></span> counter
10692                         of previous versions of
10693                         <acronym class="acronym">BIND</acronym> 9.
10694                       </p>
10695                     </td>
10696 </tr>
10697 <tr>
10698 <td>
10699                       <p><span><strong class="command">QryDropped</strong></span></p>
10700                     </td>
10701 <td>
10702                       <p><span><strong class="command"></strong></span></p>
10703                     </td>
10704 <td>
10705                       <p>
10706                         Recursive queries for which the server
10707                         discovered an excessive number of existing
10708                         recursive queries for the same name, type and
10709                         class and were subsequently dropped.
10710                         This is the number of dropped queries due to
10711                         the reason explained with the
10712                         <span><strong class="command">clients-per-query</strong></span>
10713                         and
10714                         <span><strong class="command">max-clients-per-query</strong></span>
10715                         options
10716                         (see the description about
10717                         <a href="Bv9ARM.ch06.html#clients-per-query"><span><strong class="command">clients-per-query</strong></span></a>.)
10718                         This corresponds to the
10719                         <span><strong class="command">dropped</strong></span> counter
10720                         of previous versions of
10721                         <acronym class="acronym">BIND</acronym> 9.
10722                       </p>
10723                     </td>
10724 </tr>
10725 <tr>
10726 <td>
10727                       <p><span><strong class="command">QryFailure</strong></span></p>
10728                     </td>
10729 <td>
10730                       <p><span><strong class="command"></strong></span></p>
10731                     </td>
10732 <td>
10733                       <p>
10734                         Other query failures.
10735                         This corresponds to the
10736                         <span><strong class="command">failure</strong></span> counter
10737                         of previous versions of
10738                         <acronym class="acronym">BIND</acronym> 9.
10739                         Note: this counter is provided mainly for
10740                         backward compatibility with the previous versions.
10741                         Normally a more fine-grained counters such as
10742                         <span><strong class="command">AuthQryRej</strong></span> and
10743                         <span><strong class="command">RecQryRej</strong></span>
10744                         that would also fall into this counter are provided,
10745                         and so this counter would not be of much
10746                         interest in practice.
10747                       </p>
10748                     </td>
10749 </tr>
10750 <tr>
10751 <td>
10752                       <p><span><strong class="command">XfrReqDone</strong></span></p>
10753                     </td>
10754 <td>
10755                       <p><span><strong class="command"></strong></span></p>
10756                     </td>
10757 <td>
10758                       <p>
10759                         Requested zone transfers completed.
10760                       </p>
10761                     </td>
10762 </tr>
10763 <tr>
10764 <td>
10765                       <p><span><strong class="command">UpdateReqFwd</strong></span></p>
10766                     </td>
10767 <td>
10768                       <p><span><strong class="command"></strong></span></p>
10769                     </td>
10770 <td>
10771                       <p>
10772                         Update requests forwarded.
10773                       </p>
10774                     </td>
10775 </tr>
10776 <tr>
10777 <td>
10778                       <p><span><strong class="command">UpdateRespFwd</strong></span></p>
10779                     </td>
10780 <td>
10781                       <p><span><strong class="command"></strong></span></p>
10782                     </td>
10783 <td>
10784                       <p>
10785                         Update responses forwarded.
10786                       </p>
10787                     </td>
10788 </tr>
10789 <tr>
10790 <td>
10791                       <p><span><strong class="command">UpdateFwdFail</strong></span></p>
10792                     </td>
10793 <td>
10794                       <p><span><strong class="command"></strong></span></p>
10795                     </td>
10796 <td>
10797                       <p>
10798                         Dynamic update forward failed.
10799                       </p>
10800                     </td>
10801 </tr>
10802 <tr>
10803 <td>
10804                       <p><span><strong class="command">UpdateDone</strong></span></p>
10805                     </td>
10806 <td>
10807                       <p><span><strong class="command"></strong></span></p>
10808                     </td>
10809 <td>
10810                       <p>
10811                         Dynamic updates completed.
10812                       </p>
10813                     </td>
10814 </tr>
10815 <tr>
10816 <td>
10817                       <p><span><strong class="command">UpdateFail</strong></span></p>
10818                     </td>
10819 <td>
10820                       <p><span><strong class="command"></strong></span></p>
10821                     </td>
10822 <td>
10823                       <p>
10824                         Dynamic updates failed.
10825                       </p>
10826                     </td>
10827 </tr>
10828 <tr>
10829 <td>
10830                       <p><span><strong class="command">UpdateBadPrereq</strong></span></p>
10831                     </td>
10832 <td>
10833                       <p><span><strong class="command"></strong></span></p>
10834                     </td>
10835 <td>
10836                       <p>
10837                         Dynamic updates rejected due to prerequisite failure.
10838                       </p>
10839                     </td>
10840 </tr>
10841 <tr>
10842 <td>
10843                       <p><span><strong class="command">RPZRewrites</strong></span></p>
10844                     </td>
10845 <td>
10846                       <p><span><strong class="command"></strong></span></p>
10847                     </td>
10848 <td>
10849                       <p>
10850                         Response policy zone rewrites.
10851                       </p>
10852                     </td>
10853 </tr>
10854 <tr>
10855 <td>
10856                       <p><span><strong class="command">RateDropped</strong></span></p>
10857                     </td>
10858 <td>
10859                       <p><span><strong class="command"></strong></span></p>
10860                     </td>
10861 <td>
10862                       <p>
10863                         Responses dropped by rate limits.
10864                       </p>
10865                     </td>
10866 </tr>
10867 <tr>
10868 <td>
10869                       <p><span><strong class="command">RateSlipped</strong></span></p>
10870                     </td>
10871 <td>
10872                       <p><span><strong class="command"></strong></span></p>
10873                     </td>
10874 <td>
10875                       <p>
10876                         Responses truncated by rate limits.
10877                       </p>
10878                     </td>
10879 </tr>
10880 </tbody>
10881 </table></div>
10882 </div>
10883 <div class="sect3" lang="en">
10884 <div class="titlepage"><div><div><h4 class="title">
10885 <a name="id2602424"></a>Zone Maintenance Statistics Counters</h4></div></div></div>
10886 <div class="informaltable"><table border="1">
10887 <colgroup>
10888 <col>
10889 <col>
10890 </colgroup>
10891 <tbody>
10892 <tr>
10893 <td>
10894                       <p>
10895                         <span class="emphasis"><em>Symbol</em></span>
10896                       </p>
10897                     </td>
10898 <td>
10899                       <p>
10900                         <span class="emphasis"><em>Description</em></span>
10901                       </p>
10902                     </td>
10903 </tr>
10904 <tr>
10905 <td>
10906                       <p><span><strong class="command">NotifyOutv4</strong></span></p>
10907                     </td>
10908 <td>
10909                       <p>
10910                         IPv4 notifies sent.
10911                       </p>
10912                     </td>
10913 </tr>
10914 <tr>
10915 <td>
10916                       <p><span><strong class="command">NotifyOutv6</strong></span></p>
10917                     </td>
10918 <td>
10919                       <p>
10920                         IPv6 notifies sent.
10921                       </p>
10922                     </td>
10923 </tr>
10924 <tr>
10925 <td>
10926                       <p><span><strong class="command">NotifyInv4</strong></span></p>
10927                     </td>
10928 <td>
10929                       <p>
10930                         IPv4 notifies received.
10931                       </p>
10932                     </td>
10933 </tr>
10934 <tr>
10935 <td>
10936                       <p><span><strong class="command">NotifyInv6</strong></span></p>
10937                     </td>
10938 <td>
10939                       <p>
10940                         IPv6 notifies received.
10941                       </p>
10942                     </td>
10943 </tr>
10944 <tr>
10945 <td>
10946                       <p><span><strong class="command">NotifyRej</strong></span></p>
10947                     </td>
10948 <td>
10949                       <p>
10950                         Incoming notifies rejected.
10951                       </p>
10952                     </td>
10953 </tr>
10954 <tr>
10955 <td>
10956                       <p><span><strong class="command">SOAOutv4</strong></span></p>
10957                     </td>
10958 <td>
10959                       <p>
10960                         IPv4 SOA queries sent.
10961                       </p>
10962                     </td>
10963 </tr>
10964 <tr>
10965 <td>
10966                       <p><span><strong class="command">SOAOutv6</strong></span></p>
10967                     </td>
10968 <td>
10969                       <p>
10970                         IPv6 SOA queries sent.
10971                       </p>
10972                     </td>
10973 </tr>
10974 <tr>
10975 <td>
10976                       <p><span><strong class="command">AXFRReqv4</strong></span></p>
10977                     </td>
10978 <td>
10979                       <p>
10980                         IPv4 AXFR requested.
10981                       </p>
10982                     </td>
10983 </tr>
10984 <tr>
10985 <td>
10986                       <p><span><strong class="command">AXFRReqv6</strong></span></p>
10987                     </td>
10988 <td>
10989                       <p>
10990                         IPv6 AXFR requested.
10991                       </p>
10992                     </td>
10993 </tr>
10994 <tr>
10995 <td>
10996                       <p><span><strong class="command">IXFRReqv4</strong></span></p>
10997                     </td>
10998 <td>
10999                       <p>
11000                         IPv4 IXFR requested.
11001                       </p>
11002                     </td>
11003 </tr>
11004 <tr>
11005 <td>
11006                       <p><span><strong class="command">IXFRReqv6</strong></span></p>
11007                     </td>
11008 <td>
11009                       <p>
11010                         IPv6 IXFR requested.
11011                       </p>
11012                     </td>
11013 </tr>
11014 <tr>
11015 <td>
11016                       <p><span><strong class="command">XfrSuccess</strong></span></p>
11017                     </td>
11018 <td>
11019                       <p>
11020                         Zone transfer requests succeeded.
11021                       </p>
11022                     </td>
11023 </tr>
11024 <tr>
11025 <td>
11026                       <p><span><strong class="command">XfrFail</strong></span></p>
11027                     </td>
11028 <td>
11029                       <p>
11030                         Zone transfer requests failed.
11031                       </p>
11032                     </td>
11033 </tr>
11034 </tbody>
11035 </table></div>
11036 </div>
11037 <div class="sect3" lang="en">
11038 <div class="titlepage"><div><div><h4 class="title">
11039 <a name="id2602875"></a>Resolver Statistics Counters</h4></div></div></div>
11040 <div class="informaltable"><table border="1">
11041 <colgroup>
11042 <col>
11043 <col>
11044 <col>
11045 </colgroup>
11046 <tbody>
11047 <tr>
11048 <td>
11049                       <p>
11050                         <span class="emphasis"><em>Symbol</em></span>
11051                       </p>
11052                     </td>
11053 <td>
11054                       <p>
11055                         <span class="emphasis"><em>BIND8 Symbol</em></span>
11056                       </p>
11057                     </td>
11058 <td>
11059                       <p>
11060                         <span class="emphasis"><em>Description</em></span>
11061                       </p>
11062                     </td>
11063 </tr>
11064 <tr>
11065 <td>
11066                       <p><span><strong class="command">Queryv4</strong></span></p>
11067                     </td>
11068 <td>
11069                       <p><span><strong class="command">SFwdQ</strong></span></p>
11070                     </td>
11071 <td>
11072                       <p>
11073                         IPv4 queries sent.
11074                       </p>
11075                     </td>
11076 </tr>
11077 <tr>
11078 <td>
11079                       <p><span><strong class="command">Queryv6</strong></span></p>
11080                     </td>
11081 <td>
11082                       <p><span><strong class="command">SFwdQ</strong></span></p>
11083                     </td>
11084 <td>
11085                       <p>
11086                         IPv6 queries sent.
11087                       </p>
11088                     </td>
11089 </tr>
11090 <tr>
11091 <td>
11092                       <p><span><strong class="command">Responsev4</strong></span></p>
11093                     </td>
11094 <td>
11095                       <p><span><strong class="command">RR</strong></span></p>
11096                     </td>
11097 <td>
11098                       <p>
11099                         IPv4 responses received.
11100                       </p>
11101                     </td>
11102 </tr>
11103 <tr>
11104 <td>
11105                       <p><span><strong class="command">Responsev6</strong></span></p>
11106                     </td>
11107 <td>
11108                       <p><span><strong class="command">RR</strong></span></p>
11109                     </td>
11110 <td>
11111                       <p>
11112                         IPv6 responses received.
11113                       </p>
11114                     </td>
11115 </tr>
11116 <tr>
11117 <td>
11118                       <p><span><strong class="command">NXDOMAIN</strong></span></p>
11119                     </td>
11120 <td>
11121                       <p><span><strong class="command">RNXD</strong></span></p>
11122                     </td>
11123 <td>
11124                       <p>
11125                         NXDOMAIN received.
11126                       </p>
11127                     </td>
11128 </tr>
11129 <tr>
11130 <td>
11131                       <p><span><strong class="command">SERVFAIL</strong></span></p>
11132                     </td>
11133 <td>
11134                       <p><span><strong class="command">RFail</strong></span></p>
11135                     </td>
11136 <td>
11137                       <p>
11138                         SERVFAIL received.
11139                       </p>
11140                     </td>
11141 </tr>
11142 <tr>
11143 <td>
11144                       <p><span><strong class="command">FORMERR</strong></span></p>
11145                     </td>
11146 <td>
11147                       <p><span><strong class="command">RFErr</strong></span></p>
11148                     </td>
11149 <td>
11150                       <p>
11151                         FORMERR received.
11152                       </p>
11153                     </td>
11154 </tr>
11155 <tr>
11156 <td>
11157                       <p><span><strong class="command">OtherError</strong></span></p>
11158                     </td>
11159 <td>
11160                       <p><span><strong class="command">RErr</strong></span></p>
11161                     </td>
11162 <td>
11163                       <p>
11164                         Other errors received.
11165                       </p>
11166                     </td>
11167 </tr>
11168 <tr>
11169 <td>
11170                       <p><span><strong class="command">EDNS0Fail</strong></span></p>
11171                                                  </td>
11172 <td>
11173                       <p><span><strong class="command"></strong></span></p>
11174                     </td>
11175 <td>
11176                       <p>
11177                         EDNS(0) query failures.
11178                       </p>
11179                     </td>
11180 </tr>
11181 <tr>
11182 <td>
11183                       <p><span><strong class="command">Mismatch</strong></span></p>
11184                     </td>
11185 <td>
11186                       <p><span><strong class="command">RDupR</strong></span></p>
11187                     </td>
11188 <td>
11189                       <p>
11190                         Mismatch responses received.
11191                         The DNS ID, response's source address,
11192                         and/or the response's source port does not
11193                         match what was expected.
11194                         (The port must be 53 or as defined by
11195                         the <span><strong class="command">port</strong></span> option.)
11196                         This may be an indication of a cache
11197                         poisoning attempt.
11198                       </p>
11199                     </td>
11200 </tr>
11201 <tr>
11202 <td>
11203                       <p><span><strong class="command">Truncated</strong></span></p>
11204                     </td>
11205 <td>
11206                       <p><span><strong class="command"></strong></span></p>
11207                     </td>
11208 <td>
11209                       <p>
11210                         Truncated responses received.
11211                       </p>
11212                     </td>
11213 </tr>
11214 <tr>
11215 <td>
11216                       <p><span><strong class="command">Lame</strong></span></p>
11217                     </td>
11218 <td>
11219                       <p><span><strong class="command">RLame</strong></span></p>
11220                     </td>
11221 <td>
11222                       <p>
11223                         Lame delegations received.
11224                       </p>
11225                     </td>
11226 </tr>
11227 <tr>
11228 <td>
11229                       <p><span><strong class="command">Retry</strong></span></p>
11230                     </td>
11231 <td>
11232                       <p><span><strong class="command">SDupQ</strong></span></p>
11233                     </td>
11234 <td>
11235                       <p>
11236                         Query retries performed.
11237                       </p>
11238                     </td>
11239 </tr>
11240 <tr>
11241 <td>
11242                       <p><span><strong class="command">QueryAbort</strong></span></p>
11243                     </td>
11244 <td>
11245                       <p><span><strong class="command"></strong></span></p>
11246                     </td>
11247 <td>
11248                       <p>
11249                         Queries aborted due to quota control.
11250                       </p>
11251                     </td>
11252 </tr>
11253 <tr>
11254 <td>
11255                       <p><span><strong class="command">QuerySockFail</strong></span></p>
11256                     </td>
11257 <td>
11258                       <p><span><strong class="command"></strong></span></p>
11259                     </td>
11260 <td>
11261                       <p>
11262                         Failures in opening query sockets.
11263                         One common reason for such failures is a
11264                         failure of opening a new socket due to a
11265                         limitation on file descriptors.
11266                       </p>
11267                     </td>
11268 </tr>
11269 <tr>
11270 <td>
11271                       <p><span><strong class="command">QueryTimeout</strong></span></p>
11272                     </td>
11273 <td>
11274                       <p><span><strong class="command"></strong></span></p>
11275                     </td>
11276 <td>
11277                       <p>
11278                         Query timeouts.
11279                       </p>
11280                     </td>
11281 </tr>
11282 <tr>
11283 <td>
11284                       <p><span><strong class="command">GlueFetchv4</strong></span></p>
11285                     </td>
11286 <td>
11287                       <p><span><strong class="command">SSysQ</strong></span></p>
11288                     </td>
11289 <td>
11290                       <p>
11291                         IPv4 NS address fetches invoked.
11292                       </p>
11293                     </td>
11294 </tr>
11295 <tr>
11296 <td>
11297                       <p><span><strong class="command">GlueFetchv6</strong></span></p>
11298                     </td>
11299 <td>
11300                       <p><span><strong class="command">SSysQ</strong></span></p>
11301                     </td>
11302 <td>
11303                       <p>
11304                         IPv6 NS address fetches invoked.
11305                       </p>
11306                     </td>
11307 </tr>
11308 <tr>
11309 <td>
11310                       <p><span><strong class="command">GlueFetchv4Fail</strong></span></p>
11311                     </td>
11312 <td>
11313                       <p><span><strong class="command"></strong></span></p>
11314                     </td>
11315 <td>
11316                       <p>
11317                         IPv4 NS address fetch failed.
11318                       </p>
11319                     </td>
11320 </tr>
11321 <tr>
11322 <td>
11323                       <p><span><strong class="command">GlueFetchv6Fail</strong></span></p>
11324                     </td>
11325 <td>
11326                       <p><span><strong class="command"></strong></span></p>
11327                     </td>
11328 <td>
11329                       <p>
11330                         IPv6 NS address fetch failed.
11331                       </p>
11332                     </td>
11333 </tr>
11334 <tr>
11335 <td>
11336                       <p><span><strong class="command">ValAttempt</strong></span></p>
11337                     </td>
11338 <td>
11339                       <p><span><strong class="command"></strong></span></p>
11340                     </td>
11341 <td>
11342                       <p>
11343                         DNSSEC validation attempted.
11344                       </p>
11345                     </td>
11346 </tr>
11347 <tr>
11348 <td>
11349                       <p><span><strong class="command">ValOk</strong></span></p>
11350                     </td>
11351 <td>
11352                       <p><span><strong class="command"></strong></span></p>
11353                     </td>
11354 <td>
11355                       <p>
11356                         DNSSEC validation succeeded.
11357                       </p>
11358                     </td>
11359 </tr>
11360 <tr>
11361 <td>
11362                       <p><span><strong class="command">ValNegOk</strong></span></p>
11363                     </td>
11364 <td>
11365                       <p><span><strong class="command"></strong></span></p>
11366                     </td>
11367 <td>
11368                       <p>
11369                         DNSSEC validation on negative information succeeded.
11370                       </p>
11371                     </td>
11372 </tr>
11373 <tr>
11374 <td>
11375                       <p><span><strong class="command">ValFail</strong></span></p>
11376                     </td>
11377 <td>
11378                       <p><span><strong class="command"></strong></span></p>
11379                     </td>
11380 <td>
11381                       <p>
11382                         DNSSEC validation failed.
11383                       </p>
11384                     </td>
11385 </tr>
11386 <tr>
11387 <td>
11388                       <p><span><strong class="command">QryRTTnn</strong></span></p>
11389                     </td>
11390 <td>
11391                       <p><span><strong class="command"></strong></span></p>
11392                     </td>
11393 <td>
11394                       <p>
11395                         Frequency table on round trip times (RTTs) of
11396                         queries.
11397                         Each <span><strong class="command">nn</strong></span> specifies the corresponding
11398                         frequency.
11399                         In the sequence of
11400                         <span><strong class="command">nn_1</strong></span>,
11401                         <span><strong class="command">nn_2</strong></span>,
11402                         ...,
11403                         <span><strong class="command">nn_m</strong></span>,
11404                         the value of <span><strong class="command">nn_i</strong></span> is the
11405                         number of queries whose RTTs are between
11406                         <span><strong class="command">nn_(i-1)</strong></span> (inclusive) and
11407                         <span><strong class="command">nn_i</strong></span> (exclusive) milliseconds.
11408                         For the sake of convenience we define
11409                         <span><strong class="command">nn_0</strong></span> to be 0.
11410                         The last entry should be represented as
11411                         <span><strong class="command">nn_m+</strong></span>, which means the
11412                         number of queries whose RTTs are equal to or over
11413                         <span><strong class="command">nn_m</strong></span> milliseconds.
11414                       </p>
11415                     </td>
11416 </tr>
11417 </tbody>
11418 </table></div>
11419 </div>
11420 <div class="sect3" lang="en">
11421 <div class="titlepage"><div><div><h4 class="title">
11422 <a name="id2603897"></a>Socket I/O Statistics Counters</h4></div></div></div>
11423 <p>
11424               Socket I/O statistics counters are defined per socket
11425               types, which are
11426               <span><strong class="command">UDP4</strong></span> (UDP/IPv4),
11427               <span><strong class="command">UDP6</strong></span> (UDP/IPv6),
11428               <span><strong class="command">TCP4</strong></span> (TCP/IPv4),
11429               <span><strong class="command">TCP6</strong></span> (TCP/IPv6),
11430               <span><strong class="command">Unix</strong></span> (Unix Domain), and
11431               <span><strong class="command">FDwatch</strong></span> (sockets opened outside the
11432               socket module).
11433               In the following table <span><strong class="command">&lt;TYPE&gt;</strong></span>
11434               represents a socket type.
11435               Not all counters are available for all socket types;
11436               exceptions are noted in the description field.
11437             </p>
11438 <div class="informaltable"><table border="1">
11439 <colgroup>
11440 <col>
11441 <col>
11442 </colgroup>
11443 <tbody>
11444 <tr>
11445 <td>
11446                       <p>
11447                         <span class="emphasis"><em>Symbol</em></span>
11448                       </p>
11449                     </td>
11450 <td>
11451                       <p>
11452                         <span class="emphasis"><em>Description</em></span>
11453                       </p>
11454                     </td>
11455 </tr>
11456 <tr>
11457 <td>
11458                       <p><span><strong class="command">&lt;TYPE&gt;Open</strong></span></p>
11459                     </td>
11460 <td>
11461                       <p>
11462                         Sockets opened successfully.
11463                         This counter is not applicable to the
11464                         <span><strong class="command">FDwatch</strong></span> type.
11465                       </p>
11466                     </td>
11467 </tr>
11468 <tr>
11469 <td>
11470                       <p><span><strong class="command">&lt;TYPE&gt;OpenFail</strong></span></p>
11471                     </td>
11472 <td>
11473                       <p>
11474                         Failures of opening sockets.
11475                         This counter is not applicable to the
11476                         <span><strong class="command">FDwatch</strong></span> type.
11477                       </p>
11478                     </td>
11479 </tr>
11480 <tr>
11481 <td>
11482                       <p><span><strong class="command">&lt;TYPE&gt;Close</strong></span></p>
11483                     </td>
11484 <td>
11485                       <p>
11486                         Sockets closed.
11487                       </p>
11488                     </td>
11489 </tr>
11490 <tr>
11491 <td>
11492                       <p><span><strong class="command">&lt;TYPE&gt;BindFail</strong></span></p>
11493                     </td>
11494 <td>
11495                       <p>
11496                         Failures of binding sockets.
11497                       </p>
11498                     </td>
11499 </tr>
11500 <tr>
11501 <td>
11502                       <p><span><strong class="command">&lt;TYPE&gt;ConnFail</strong></span></p>
11503                     </td>
11504 <td>
11505                       <p>
11506                         Failures of connecting sockets.
11507                       </p>
11508                     </td>
11509 </tr>
11510 <tr>
11511 <td>
11512                       <p><span><strong class="command">&lt;TYPE&gt;Conn</strong></span></p>
11513                     </td>
11514 <td>
11515                       <p>
11516                         Connections established successfully.
11517                       </p>
11518                     </td>
11519 </tr>
11520 <tr>
11521 <td>
11522                       <p><span><strong class="command">&lt;TYPE&gt;AcceptFail</strong></span></p>
11523                     </td>
11524 <td>
11525                       <p>
11526                         Failures of accepting incoming connection requests.
11527                         This counter is not applicable to the
11528                         <span><strong class="command">UDP</strong></span> and
11529                         <span><strong class="command">FDwatch</strong></span> types.
11530                       </p>
11531                     </td>
11532 </tr>
11533 <tr>
11534 <td>
11535                       <p><span><strong class="command">&lt;TYPE&gt;Accept</strong></span></p>
11536                     </td>
11537 <td>
11538                       <p>
11539                         Incoming connections successfully accepted.
11540                         This counter is not applicable to the
11541                         <span><strong class="command">UDP</strong></span> and
11542                         <span><strong class="command">FDwatch</strong></span> types.
11543                       </p>
11544                     </td>
11545 </tr>
11546 <tr>
11547 <td>
11548                       <p><span><strong class="command">&lt;TYPE&gt;SendErr</strong></span></p>
11549                     </td>
11550 <td>
11551                       <p>
11552                         Errors in socket send operations.
11553                         This counter corresponds
11554                         to <span><strong class="command">SErr</strong></span> counter of
11555                         <span><strong class="command">BIND</strong></span> 8.
11556                       </p>
11557                     </td>
11558 </tr>
11559 <tr>
11560 <td>
11561                       <p><span><strong class="command">&lt;TYPE&gt;RecvErr</strong></span></p>
11562                     </td>
11563 <td>
11564                       <p>
11565                         Errors in socket receive operations.
11566                         This includes errors of send operations on a
11567                         connected UDP socket notified by an ICMP error
11568                         message.
11569                       </p>
11570                     </td>
11571 </tr>
11572 </tbody>
11573 </table></div>
11574 </div>
11575 <div class="sect3" lang="en">
11576 <div class="titlepage"><div><div><h4 class="title">
11577 <a name="id2604339"></a>Compatibility with <span class="emphasis"><em>BIND</em></span> 8 Counters</h4></div></div></div>
11578 <p>
11579               Most statistics counters that were available
11580               in <span><strong class="command">BIND</strong></span> 8 are also supported in
11581               <span><strong class="command">BIND</strong></span> 9 as shown in the above tables.
11582               Here are notes about other counters that do not appear
11583               in these tables.
11584             </p>
11585 <div class="variablelist"><dl>
11586 <dt><span class="term"><span><strong class="command">RFwdR,SFwdR</strong></span></span></dt>
11587 <dd><p>
11588                     These counters are not supported
11589                     because <span><strong class="command">BIND</strong></span> 9 does not adopt
11590                     the notion of <span class="emphasis"><em>forwarding</em></span>
11591                     as <span><strong class="command">BIND</strong></span> 8 did.
11592                   </p></dd>
11593 <dt><span class="term"><span><strong class="command">RAXFR</strong></span></span></dt>
11594 <dd><p>
11595                     This counter is accessible in the Incoming Queries section.
11596                   </p></dd>
11597 <dt><span class="term"><span><strong class="command">RIQ</strong></span></span></dt>
11598 <dd><p>
11599                     This counter is accessible in the Incoming Requests section.
11600                   </p></dd>
11601 <dt><span class="term"><span><strong class="command">ROpts</strong></span></span></dt>
11602 <dd><p>
11603                     This counter is not supported
11604                     because <span><strong class="command">BIND</strong></span> 9 does not care
11605                     about IP options in the first place.
11606                   </p></dd>
11607 </dl></div>
11608 </div>
11609 </div>
11610 </div>
11611 </div>
11612 <div class="navfooter">
11613 <hr>
11614 <table width="100%" summary="Navigation footer">
11615 <tr>
11616 <td width="40%" align="left">
11617 <a accesskey="p" href="Bv9ARM.ch05.html">Prev</a> </td>
11618 <td width="20%" align="center"> </td>
11619 <td width="40%" align="right"> <a accesskey="n" href="Bv9ARM.ch07.html">Next</a>
11620 </td>
11621 </tr>
11622 <tr>
11623 <td width="40%" align="left" valign="top">Chapter 5. The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver </td>
11624 <td width="20%" align="center"><a accesskey="h" href="Bv9ARM.html">Home</a></td>
11625 <td width="40%" align="right" valign="top"> Chapter 7. <acronym class="acronym">BIND</acronym> 9 Security Considerations</td>
11626 </tr>
11627 </table>
11628 </div>
11629 <p style="text-align: center;">BIND Version 9.9</p>
11630 </body>
11631 </html>