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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#id2573374">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#id2574035"><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#id2574225"><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#id2574584"><span><strong class="command">include</strong></span> Statement Grammar</a></span></dt>
  62 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574601"><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#id2574761"><span><strong class="command">key</strong></span> Statement Grammar</a></span></dt>
  65 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574785"><span><strong class="command">key</strong></span> Statement Definition and Usage</a></span></dt>
  66 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574875"><span><strong class="command">logging</strong></span> Statement Grammar</a></span></dt>
  67 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575001"><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#id2577236"><span><strong class="command">lwres</strong></span> Statement Grammar</a></span></dt>
  70 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577309"><span><strong class="command">lwres</strong></span> Statement Definition and Usage</a></span></dt>
  71 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577373"><span><strong class="command">masters</strong></span> Statement Grammar</a></span></dt>
  72 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577417"><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#id2577438"><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#id2590832"><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#id2591139"><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#id2591186"><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#id2591553"><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#id2593398"><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#id2597084">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#id2600002">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#id2600549">Inverse Mapping in IPv4</a></span></dt>
 101 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2600812">Other Zone File Directives</a></span></dt>
 102 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2601017"><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="id2573073"></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="id2573100"></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="id2573374"></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="id2573458"></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="id2573488"></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="id2574035"></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           The following ACLs are built-in:
 886         </p>
 887 <div class="informaltable"><table border="1">
 888 <colgroup>
 889 <col>
 890 <col>
 891 </colgroup>
 892 <tbody>
 893 <tr>
 894 <td>
 895                   <p><span><strong class="command">any</strong></span></p>
 896                 </td>
 897 <td>
 898                   <p>
 899                     Matches all hosts.
 900                   </p>
 901                 </td>
 902 </tr>
 903 <tr>
 904 <td>
 905                   <p><span><strong class="command">none</strong></span></p>
 906                 </td>
 907 <td>
 908                   <p>
 909                     Matches no hosts.
 910                   </p>
 911                 </td>
 912 </tr>
 913 <tr>
 914 <td>
 915                   <p><span><strong class="command">localhost</strong></span></p>
 916                 </td>
 917 <td>
 918                   <p>
 919                     Matches the IPv4 and IPv6 addresses of all network
 920                     interfaces on the system.  When addresses are
 921                     added or removed, the <span><strong class="command">localhost</strong></span>
 922                     ACL element is updated to reflect the changes.
 923                   </p>
 924                 </td>
 925 </tr>
 926 <tr>
 927 <td>
 928                   <p><span><strong class="command">localnets</strong></span></p>
 929                 </td>
 930 <td>
 931                   <p>
 932                     Matches any host on an IPv4 or IPv6 network
 933                     for which the system has an interface.
 934                     When addresses are added or removed,
 935                     the <span><strong class="command">localnets</strong></span>
 936                     ACL element is updated to reflect the changes.
 937                     Some systems do not provide a way to determine the prefix
 938                     lengths of
 939                     local IPv6 addresses.
 940                     In such a case, <span><strong class="command">localnets</strong></span>
 941                     only matches the local
 942                     IPv6 addresses, just like <span><strong class="command">localhost</strong></span>.
 943                   </p>
 944                 </td>
 945 </tr>
 946 </tbody>
 947 </table></div>
 948 </div>
 949 <div class="sect2" lang="en">
 950 <div class="titlepage"><div><div><h3 class="title">
 951 <a name="id2574225"></a><span><strong class="command">controls</strong></span> Statement Grammar</h3></div></div></div>
 952 <pre class="programlisting"><span><strong class="command">controls</strong></span> {
 953    [ inet ( ip_addr | * ) [ port ip_port ]
 954                 allow { <em class="replaceable"><code> address_match_list </code></em> }
 955                 keys { <em class="replaceable"><code>key_list</code></em> }; ]
 956    [ inet ...; ]
 957    [ unix <em class="replaceable"><code>path</code></em> perm <em class="replaceable"><code>number</code></em> owner <em class="replaceable"><code>number</code></em> group <em class="replaceable"><code>number</code></em>
 958      keys { <em class="replaceable"><code>key_list</code></em> }; ]
 959    [ unix ...; ]
 960 };
 961 </pre>
 962 </div>
 963 <div class="sect2" lang="en">
 964 <div class="titlepage"><div><div><h3 class="title">
 965 <a name="controls_statement_definition_and_usage"></a><span><strong class="command">controls</strong></span> Statement Definition and
 966           Usage</h3></div></div></div>
 967 <p>
 968           The <span><strong class="command">controls</strong></span> statement declares control
 969           channels to be used by system administrators to control the
 970           operation of the name server. These control channels are
 971           used by the <span><strong class="command">rndc</strong></span> utility to send
 972           commands to and retrieve non-DNS results from a name server.
 973         </p>
 974 <p>
 975           An <span><strong class="command">inet</strong></span> control channel is a TCP socket
 976           listening at the specified <span><strong class="command">ip_port</strong></span> on the
 977           specified <span><strong class="command">ip_addr</strong></span>, which can be an IPv4 or IPv6
 978           address.  An <span><strong class="command">ip_addr</strong></span> of <code class="literal">*</code> (asterisk) is
 979           interpreted as the IPv4 wildcard address; connections will be
 980           accepted on any of the system's IPv4 addresses.
 981           To listen on the IPv6 wildcard address,
 982           use an <span><strong class="command">ip_addr</strong></span> of <code class="literal">::</code>.
 983           If you will only use <span><strong class="command">rndc</strong></span> on the local host,
 984           using the loopback address (<code class="literal">127.0.0.1</code>
 985           or <code class="literal">::1</code>) is recommended for maximum security.
 986         </p>
 987 <p>
 988           If no port is specified, port 953 is used. The asterisk
 989           "<code class="literal">*</code>" cannot be used for <span><strong class="command">ip_port</strong></span>.
 990         </p>
 991 <p>
 992           The ability to issue commands over the control channel is
 993           restricted by the <span><strong class="command">allow</strong></span> and
 994           <span><strong class="command">keys</strong></span> clauses.
 995           Connections to the control channel are permitted based on the
 996           <span><strong class="command">address_match_list</strong></span>.  This is for simple
 997           IP address based filtering only; any <span><strong class="command">key_id</strong></span>
 998           elements of the <span><strong class="command">address_match_list</strong></span>
 999           are ignored.
1000         </p>
1001 <p>
1002           A <span><strong class="command">unix</strong></span> control channel is a UNIX domain
1003           socket listening at the specified path in the file system.
1004           Access to the socket is specified by the <span><strong class="command">perm</strong></span>,
1005           <span><strong class="command">owner</strong></span> and <span><strong class="command">group</strong></span> clauses.
1006           Note on some platforms (SunOS and Solaris) the permissions
1007           (<span><strong class="command">perm</strong></span>) are applied to the parent directory
1008           as the permissions on the socket itself are ignored.
1009         </p>
1010 <p>
1011           The primary authorization mechanism of the command
1012           channel is the <span><strong class="command">key_list</strong></span>, which
1013           contains a list of <span><strong class="command">key_id</strong></span>s.
1014           Each <span><strong class="command">key_id</strong></span> in the <span><strong class="command">key_list</strong></span>
1015           is authorized to execute commands over the control channel.
1016           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>)
1017           for information about configuring keys in <span><strong class="command">rndc</strong></span>.
1018         </p>
1019 <p>
1020           If no <span><strong class="command">controls</strong></span> statement is present,
1021           <span><strong class="command">named</strong></span> will set up a default
1022           control channel listening on the loopback address 127.0.0.1
1023           and its IPv6 counterpart ::1.
1024           In this case, and also when the <span><strong class="command">controls</strong></span> statement
1025           is present but does not have a <span><strong class="command">keys</strong></span> clause,
1026           <span><strong class="command">named</strong></span> will attempt to load the command channel key
1027           from the file <code class="filename">rndc.key</code> in
1028           <code class="filename">/etc</code> (or whatever <code class="varname">sysconfdir</code>
1029           was specified as when <acronym class="acronym">BIND</acronym> was built).
1030           To create a <code class="filename">rndc.key</code> file, run
1031           <strong class="userinput"><code>rndc-confgen -a</code></strong>.
1032         </p>
1033 <p>
1034           The <code class="filename">rndc.key</code> feature was created to
1035           ease the transition of systems from <acronym class="acronym">BIND</acronym> 8,
1036           which did not have digital signatures on its command channel
1037           messages and thus did not have a <span><strong class="command">keys</strong></span> clause.
1038
1039           It makes it possible to use an existing <acronym class="acronym">BIND</acronym> 8
1040           configuration file in <acronym class="acronym">BIND</acronym> 9 unchanged,
1041           and still have <span><strong class="command">rndc</strong></span> work the same way
1042           <span><strong class="command">ndc</strong></span> worked in BIND 8, simply by executing the
1043           command <strong class="userinput"><code>rndc-confgen -a</code></strong> after BIND 9 is
1044           installed.
1045         </p>
1046 <p>
1047           Since the <code class="filename">rndc.key</code> feature
1048           is only intended to allow the backward-compatible usage of
1049           <acronym class="acronym">BIND</acronym> 8 configuration files, this
1050           feature does not
1051           have a high degree of configurability.  You cannot easily change
1052           the key name or the size of the secret, so you should make a
1053           <code class="filename">rndc.conf</code> with your own key if you
1054           wish to change
1055           those things.  The <code class="filename">rndc.key</code> file
1056           also has its
1057           permissions set such that only the owner of the file (the user that
1058           <span><strong class="command">named</strong></span> is running as) can access it.
1059           If you
1060           desire greater flexibility in allowing other users to access
1061           <span><strong class="command">rndc</strong></span> commands, then you need to create
1062           a
1063           <code class="filename">rndc.conf</code> file and make it group
1064           readable by a group
1065           that contains the users who should have access.
1066         </p>
1067 <p>
1068           To disable the command channel, use an empty
1069           <span><strong class="command">controls</strong></span> statement:
1070           <span><strong class="command">controls { };</strong></span>.
1071         </p>
1072 </div>
1073 <div class="sect2" lang="en">
1074 <div class="titlepage"><div><div><h3 class="title">
1075 <a name="id2574584"></a><span><strong class="command">include</strong></span> Statement Grammar</h3></div></div></div>
1076 <pre class="programlisting"><span><strong class="command">include</strong></span> <em class="replaceable"><code>filename</code></em>;</pre>
1077 </div>
1078 <div class="sect2" lang="en">
1079 <div class="titlepage"><div><div><h3 class="title">
1080 <a name="id2574601"></a><span><strong class="command">include</strong></span> Statement Definition and
1081           Usage</h3></div></div></div>
1082 <p>
1083           The <span><strong class="command">include</strong></span> statement inserts the
1084           specified file at the point where the <span><strong class="command">include</strong></span>
1085           statement is encountered. The <span><strong class="command">include</strong></span>
1086                 statement facilitates the administration of configuration
1087           files
1088           by permitting the reading or writing of some things but not
1089           others. For example, the statement could include private keys
1090           that are readable only by the name server.
1091         </p>
1092 </div>
1093 <div class="sect2" lang="en">
1094 <div class="titlepage"><div><div><h3 class="title">
1095 <a name="id2574761"></a><span><strong class="command">key</strong></span> Statement Grammar</h3></div></div></div>
1096 <pre class="programlisting"><span><strong class="command">key</strong></span> <em class="replaceable"><code>key_id</code></em> {
1097     algorithm <em class="replaceable"><code>algorithm_id</code></em>;
1098     secret <em class="replaceable"><code>secret_string</code></em>;
1099 };
1100 </pre>
1101 </div>
1102 <div class="sect2" lang="en">
1103 <div class="titlepage"><div><div><h3 class="title">
1104 <a name="id2574785"></a><span><strong class="command">key</strong></span> Statement Definition and Usage</h3></div></div></div>
1105 <p>
1106           The <span><strong class="command">key</strong></span> statement defines a shared
1107           secret key for use with TSIG (see <a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
1108           or the command channel
1109           (see <a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and
1110           Usage">the section called &#8220;<span><strong class="command">controls</strong></span> Statement Definition and
1111           Usage&#8221;</a>).
1112         </p>
1113 <p>
1114           The <span><strong class="command">key</strong></span> statement can occur at the
1115           top level
1116           of the configuration file or inside a <span><strong class="command">view</strong></span>
1117           statement.  Keys defined in top-level <span><strong class="command">key</strong></span>
1118           statements can be used in all views.  Keys intended for use in
1119           a <span><strong class="command">controls</strong></span> statement
1120           (see <a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and
1121           Usage">the section called &#8220;<span><strong class="command">controls</strong></span> Statement Definition and
1122           Usage&#8221;</a>)
1123           must be defined at the top level.
1124         </p>
1125 <p>
1126           The <em class="replaceable"><code>key_id</code></em>, also known as the
1127           key name, is a domain name uniquely identifying the key. It can
1128           be used in a <span><strong class="command">server</strong></span>
1129           statement to cause requests sent to that
1130           server to be signed with this key, or in address match lists to
1131           verify that incoming requests have been signed with a key
1132           matching this name, algorithm, and secret.
1133         </p>
1134 <p>
1135           The <em class="replaceable"><code>algorithm_id</code></em> is a string
1136           that specifies a security/authentication algorithm.  Named
1137           supports <code class="literal">hmac-md5</code>,
1138           <code class="literal">hmac-sha1</code>, <code class="literal">hmac-sha224</code>,
1139           <code class="literal">hmac-sha256</code>, <code class="literal">hmac-sha384</code>
1140           and <code class="literal">hmac-sha512</code> TSIG authentication.
1141           Truncated hashes are supported by appending the minimum
1142           number of required bits preceded by a dash, e.g.
1143           <code class="literal">hmac-sha1-80</code>.  The
1144           <em class="replaceable"><code>secret_string</code></em> is the secret
1145           to be used by the algorithm, and is treated as a base-64
1146           encoded string.
1147         </p>
1148 </div>
1149 <div class="sect2" lang="en">
1150 <div class="titlepage"><div><div><h3 class="title">
1151 <a name="id2574875"></a><span><strong class="command">logging</strong></span> Statement Grammar</h3></div></div></div>
1152 <pre class="programlisting"><span><strong class="command">logging</strong></span> {
1153    [ <span><strong class="command">channel</strong></span> <em class="replaceable"><code>channel_name</code></em> {
1154      ( <span><strong class="command">file</strong></span> <em class="replaceable"><code>path_name</code></em>
1155          [ <span><strong class="command">versions</strong></span> ( <em class="replaceable"><code>number</code></em> | <span><strong class="command">unlimited</strong></span> ) ]
1156          [ <span><strong class="command">size</strong></span> <em class="replaceable"><code>size_spec</code></em> ]
1157        | <span><strong class="command">syslog</strong></span> <em class="replaceable"><code>syslog_facility</code></em>
1158        | <span><strong class="command">stderr</strong></span>
1159        | <span><strong class="command">null</strong></span> );
1160      [ <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> |
1161                  <code class="option">info</code> | <code class="option">debug</code> [ <em class="replaceable"><code>level</code></em> ] | <code class="option">dynamic</code> ); ]
1162      [ <span><strong class="command">print-category</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1163      [ <span><strong class="command">print-severity</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1164      [ <span><strong class="command">print-time</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1165    }; ]
1166    [ <span><strong class="command">category</strong></span> <em class="replaceable"><code>category_name</code></em> {
1167      <em class="replaceable"><code>channel_name</code></em> ; [ <em class="replaceable"><code>channel_name</code></em> ; ... ]
1168    }; ]
1169    ...
1170 };
1171 </pre>
1172 </div>
1173 <div class="sect2" lang="en">
1174 <div class="titlepage"><div><div><h3 class="title">
1175 <a name="id2575001"></a><span><strong class="command">logging</strong></span> Statement Definition and
1176           Usage</h3></div></div></div>
1177 <p>
1178           The <span><strong class="command">logging</strong></span> statement configures a
1179           wide
1180           variety of logging options for the name server. Its <span><strong class="command">channel</strong></span> phrase
1181           associates output methods, format options and severity levels with
1182           a name that can then be used with the <span><strong class="command">category</strong></span> phrase
1183           to select how various classes of messages are logged.
1184         </p>
1185 <p>
1186           Only one <span><strong class="command">logging</strong></span> statement is used to
1187           define
1188           as many channels and categories as are wanted. If there is no <span><strong class="command">logging</strong></span> statement,
1189           the logging configuration will be:
1190         </p>
1191 <pre class="programlisting">logging {
1192      category default { default_syslog; default_debug; };
1193      category unmatched { null; };
1194 };
1195 </pre>
1196 <p>
1197           In <acronym class="acronym">BIND</acronym> 9, the logging configuration
1198           is only established when
1199           the entire configuration file has been parsed.  In <acronym class="acronym">BIND</acronym> 8, it was
1200           established as soon as the <span><strong class="command">logging</strong></span>
1201           statement
1202           was parsed. When the server is starting up, all logging messages
1203           regarding syntax errors in the configuration file go to the default
1204           channels, or to standard error if the "<code class="option">-g</code>" option
1205           was specified.
1206         </p>
1207 <div class="sect3" lang="en">
1208 <div class="titlepage"><div><div><h4 class="title">
1209 <a name="id2575053"></a>The <span><strong class="command">channel</strong></span> Phrase</h4></div></div></div>
1210 <p>
1211             All log output goes to one or more <span class="emphasis"><em>channels</em></span>;
1212             you can make as many of them as you want.
1213           </p>
1214 <p>
1215             Every channel definition must include a destination clause that
1216             says whether messages selected for the channel go to a file, to a
1217             particular syslog facility, to the standard error stream, or are
1218             discarded. It can optionally also limit the message severity level
1219             that will be accepted by the channel (the default is
1220             <span><strong class="command">info</strong></span>), and whether to include a
1221             <span><strong class="command">named</strong></span>-generated time stamp, the
1222             category name
1223             and/or severity level (the default is not to include any).
1224           </p>
1225 <p>
1226             The <span><strong class="command">null</strong></span> destination clause
1227             causes all messages sent to the channel to be discarded;
1228             in that case, other options for the channel are meaningless.
1229           </p>
1230 <p>
1231             The <span><strong class="command">file</strong></span> destination clause directs
1232             the channel
1233             to a disk file.  It can include limitations
1234             both on how large the file is allowed to become, and how many
1235             versions
1236             of the file will be saved each time the file is opened.
1237           </p>
1238 <p>
1239             If you use the <span><strong class="command">versions</strong></span> log file
1240             option, then
1241             <span><strong class="command">named</strong></span> will retain that many backup
1242             versions of the file by
1243             renaming them when opening.  For example, if you choose to keep
1244             three old versions
1245             of the file <code class="filename">lamers.log</code>, then just
1246             before it is opened
1247             <code class="filename">lamers.log.1</code> is renamed to
1248             <code class="filename">lamers.log.2</code>, <code class="filename">lamers.log.0</code> is renamed
1249             to <code class="filename">lamers.log.1</code>, and <code class="filename">lamers.log</code> is
1250             renamed to <code class="filename">lamers.log.0</code>.
1251             You can say <span><strong class="command">versions unlimited</strong></span> to
1252             not limit
1253             the number of versions.
1254             If a <span><strong class="command">size</strong></span> option is associated with
1255             the log file,
1256             then renaming is only done when the file being opened exceeds the
1257             indicated size.  No backup versions are kept by default; any
1258             existing
1259             log file is simply appended.
1260           </p>
1261 <p>
1262             The <span><strong class="command">size</strong></span> option for files is used
1263             to limit log
1264             growth. If the file ever exceeds the size, then <span><strong class="command">named</strong></span> will
1265             stop writing to the file unless it has a <span><strong class="command">versions</strong></span> option
1266             associated with it.  If backup versions are kept, the files are
1267             rolled as
1268             described above and a new one begun.  If there is no
1269             <span><strong class="command">versions</strong></span> option, no more data will
1270             be written to the log
1271             until some out-of-band mechanism removes or truncates the log to
1272             less than the
1273             maximum size.  The default behavior is not to limit the size of
1274             the
1275             file.
1276           </p>
1277 <p>
1278             Example usage of the <span><strong class="command">size</strong></span> and
1279             <span><strong class="command">versions</strong></span> options:
1280           </p>
1281 <pre class="programlisting">channel an_example_channel {
1282     file "example.log" versions 3 size 20m;
1283     print-time yes;
1284     print-category yes;
1285 };
1286 </pre>
1287 <p>
1288             The <span><strong class="command">syslog</strong></span> destination clause
1289             directs the
1290             channel to the system log.  Its argument is a
1291             syslog facility as described in the <span><strong class="command">syslog</strong></span> man
1292             page. Known facilities are <span><strong class="command">kern</strong></span>, <span><strong class="command">user</strong></span>,
1293             <span><strong class="command">mail</strong></span>, <span><strong class="command">daemon</strong></span>, <span><strong class="command">auth</strong></span>,
1294             <span><strong class="command">syslog</strong></span>, <span><strong class="command">lpr</strong></span>, <span><strong class="command">news</strong></span>,
1295             <span><strong class="command">uucp</strong></span>, <span><strong class="command">cron</strong></span>, <span><strong class="command">authpriv</strong></span>,
1296             <span><strong class="command">ftp</strong></span>, <span><strong class="command">local0</strong></span>, <span><strong class="command">local1</strong></span>,
1297             <span><strong class="command">local2</strong></span>, <span><strong class="command">local3</strong></span>, <span><strong class="command">local4</strong></span>,
1298             <span><strong class="command">local5</strong></span>, <span><strong class="command">local6</strong></span> and
1299             <span><strong class="command">local7</strong></span>, however not all facilities
1300             are supported on
1301             all operating systems.
1302             How <span><strong class="command">syslog</strong></span> will handle messages
1303             sent to
1304             this facility is described in the <span><strong class="command">syslog.conf</strong></span> man
1305             page. If you have a system which uses a very old version of <span><strong class="command">syslog</strong></span> that
1306             only uses two arguments to the <span><strong class="command">openlog()</strong></span> function,
1307             then this clause is silently ignored.
1308           </p>
1309 <p>
1310             On Windows machines syslog messages are directed to the EventViewer.
1311           </p>
1312 <p>
1313             The <span><strong class="command">severity</strong></span> clause works like <span><strong class="command">syslog</strong></span>'s
1314             "priorities", except that they can also be used if you are writing
1315             straight to a file rather than using <span><strong class="command">syslog</strong></span>.
1316             Messages which are not at least of the severity level given will
1317             not be selected for the channel; messages of higher severity
1318             levels
1319             will be accepted.
1320           </p>
1321 <p>
1322             If you are using <span><strong class="command">syslog</strong></span>, then the <span><strong class="command">syslog.conf</strong></span> priorities
1323             will also determine what eventually passes through. For example,
1324             defining a channel facility and severity as <span><strong class="command">daemon</strong></span> and <span><strong class="command">debug</strong></span> but
1325             only logging <span><strong class="command">daemon.warning</strong></span> via <span><strong class="command">syslog.conf</strong></span> will
1326             cause messages of severity <span><strong class="command">info</strong></span> and
1327             <span><strong class="command">notice</strong></span> to
1328             be dropped. If the situation were reversed, with <span><strong class="command">named</strong></span> writing
1329             messages of only <span><strong class="command">warning</strong></span> or higher,
1330             then <span><strong class="command">syslogd</strong></span> would
1331             print all messages it received from the channel.
1332           </p>
1333 <p>
1334             The <span><strong class="command">stderr</strong></span> destination clause
1335             directs the
1336             channel to the server's standard error stream.  This is intended
1337             for
1338             use when the server is running as a foreground process, for
1339             example
1340             when debugging a configuration.
1341           </p>
1342 <p>
1343             The server can supply extensive debugging information when
1344             it is in debugging mode. If the server's global debug level is
1345             greater
1346             than zero, then debugging mode will be active. The global debug
1347             level is set either by starting the <span><strong class="command">named</strong></span> server
1348             with the <code class="option">-d</code> flag followed by a positive integer,
1349             or by running <span><strong class="command">rndc trace</strong></span>.
1350             The global debug level
1351             can be set to zero, and debugging mode turned off, by running <span><strong class="command">rndc
1352 notrace</strong></span>. All debugging messages in the server have a debug
1353             level, and higher debug levels give more detailed output. Channels
1354             that specify a specific debug severity, for example:
1355           </p>
1356 <pre class="programlisting">channel specific_debug_level {
1357     file "foo";
1358     severity debug 3;
1359 };
1360 </pre>
1361 <p>
1362             will get debugging output of level 3 or less any time the
1363             server is in debugging mode, regardless of the global debugging
1364             level. Channels with <span><strong class="command">dynamic</strong></span>
1365             severity use the
1366             server's global debug level to determine what messages to print.
1367           </p>
1368 <p>
1369             If <span><strong class="command">print-time</strong></span> has been turned on,
1370             then
1371             the date and time will be logged. <span><strong class="command">print-time</strong></span> may
1372             be specified for a <span><strong class="command">syslog</strong></span> channel,
1373             but is usually
1374             pointless since <span><strong class="command">syslog</strong></span> also logs
1375             the date and
1376             time. If <span><strong class="command">print-category</strong></span> is
1377             requested, then the
1378             category of the message will be logged as well. Finally, if <span><strong class="command">print-severity</strong></span> is
1379             on, then the severity level of the message will be logged. The <span><strong class="command">print-</strong></span> options may
1380             be used in any combination, and will always be printed in the
1381             following
1382             order: time, category, severity. Here is an example where all
1383             three <span><strong class="command">print-</strong></span> options
1384             are on:
1385           </p>
1386 <p>
1387             <code class="computeroutput">28-Feb-2000 15:05:32.863 general: notice: running</code>
1388           </p>
1389 <p>
1390             There are four predefined channels that are used for
1391             <span><strong class="command">named</strong></span>'s default logging as follows.
1392             How they are
1393             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>.
1394           </p>
1395 <pre class="programlisting">channel default_syslog {
1396     // send to syslog's daemon facility
1397     syslog daemon;
1398     // only send priority info and higher
1399     severity info;
1400
1401 channel default_debug {
1402     // write to named.run in the working directory
1403     // Note: stderr is used instead of "named.run" if
1404     // the server is started with the '-f' option.
1405     file "named.run";
1406     // log at the server's current debug level
1407     severity dynamic;
1408 };
1409
1410 channel default_stderr {
1411     // writes to stderr
1412     stderr;
1413     // only send priority info and higher
1414     severity info;
1415 };
1416
1417 channel null {
1418    // toss anything sent to this channel
1419    null;
1420 };
1421 </pre>
1422 <p>
1423             The <span><strong class="command">default_debug</strong></span> channel has the
1424             special
1425             property that it only produces output when the server's debug
1426             level is
1427             nonzero.  It normally writes to a file called <code class="filename">named.run</code>
1428             in the server's working directory.
1429           </p>
1430 <p>
1431             For security reasons, when the "<code class="option">-u</code>"
1432             command line option is used, the <code class="filename">named.run</code> file
1433             is created only after <span><strong class="command">named</strong></span> has
1434             changed to the
1435             new UID, and any debug output generated while <span><strong class="command">named</strong></span> is
1436             starting up and still running as root is discarded.  If you need
1437             to capture this output, you must run the server with the "<code class="option">-g</code>"
1438             option and redirect standard error to a file.
1439           </p>
1440 <p>
1441             Once a channel is defined, it cannot be redefined. Thus you
1442             cannot alter the built-in channels directly, but you can modify
1443             the default logging by pointing categories at channels you have
1444             defined.
1445           </p>
1446 </div>
1447 <div class="sect3" lang="en">
1448 <div class="titlepage"><div><div><h4 class="title">
1449 <a name="the_category_phrase"></a>The <span><strong class="command">category</strong></span> Phrase</h4></div></div></div>
1450 <p>
1451             There are many categories, so you can send the logs you want
1452             to see wherever you want, without seeing logs you don't want. If
1453             you don't specify a list of channels for a category, then log
1454             messages
1455             in that category will be sent to the <span><strong class="command">default</strong></span> category
1456             instead. If you don't specify a default category, the following
1457             "default default" is used:
1458           </p>
1459 <pre class="programlisting">category default { default_syslog; default_debug; };
1460 </pre>
1461 <p>
1462             As an example, let's say you want to log security events to
1463             a file, but you also want keep the default logging behavior. You'd
1464             specify the following:
1465           </p>
1466 <pre class="programlisting">channel my_security_channel {
1467     file "my_security_file";
1468     severity info;
1469 };
1470 category security {
1471     my_security_channel;
1472     default_syslog;
1473     default_debug;
1474 };</pre>
1475 <p>
1476             To discard all messages in a category, specify the <span><strong class="command">null</strong></span> channel:
1477           </p>
1478 <pre class="programlisting">category xfer-out { null; };
1479 category notify { null; };
1480 </pre>
1481 <p>
1482             Following are the available categories and brief descriptions
1483             of the types of log information they contain. More
1484             categories may be added in future <acronym class="acronym">BIND</acronym> releases.
1485           </p>
1486 <div class="informaltable"><table border="1">
1487 <colgroup>
1488 <col>
1489 <col>
1490 </colgroup>
1491 <tbody>
1492 <tr>
1493 <td>
1494                     <p><span><strong class="command">default</strong></span></p>
1495                   </td>
1496 <td>
1497                     <p>
1498                       The default category defines the logging
1499                       options for those categories where no specific
1500                       configuration has been
1501                       defined.
1502                     </p>
1503                   </td>
1504 </tr>
1505 <tr>
1506 <td>
1507                     <p><span><strong class="command">general</strong></span></p>
1508                   </td>
1509 <td>
1510                     <p>
1511                       The catch-all. Many things still aren't
1512                       classified into categories, and they all end up here.
1513                     </p>
1514                   </td>
1515 </tr>
1516 <tr>
1517 <td>
1518                     <p><span><strong class="command">database</strong></span></p>
1519                   </td>
1520 <td>
1521                     <p>
1522                       Messages relating to the databases used
1523                       internally by the name server to store zone and cache
1524                       data.
1525                     </p>
1526                   </td>
1527 </tr>
1528 <tr>
1529 <td>
1530                     <p><span><strong class="command">security</strong></span></p>
1531                   </td>
1532 <td>
1533                     <p>
1534                       Approval and denial of requests.
1535                     </p>
1536                   </td>
1537 </tr>
1538 <tr>
1539 <td>
1540                     <p><span><strong class="command">config</strong></span></p>
1541                   </td>
1542 <td>
1543                     <p>
1544                       Configuration file parsing and processing.
1545                     </p>
1546                   </td>
1547 </tr>
1548 <tr>
1549 <td>
1550                     <p><span><strong class="command">resolver</strong></span></p>
1551                   </td>
1552 <td>
1553                     <p>
1554                       DNS resolution, such as the recursive
1555                       lookups performed on behalf of clients by a caching name
1556                       server.
1557                     </p>
1558                   </td>
1559 </tr>
1560 <tr>
1561 <td>
1562                     <p><span><strong class="command">xfer-in</strong></span></p>
1563                   </td>
1564 <td>
1565                     <p>
1566                       Zone transfers the server is receiving.
1567                     </p>
1568                   </td>
1569 </tr>
1570 <tr>
1571 <td>
1572                     <p><span><strong class="command">xfer-out</strong></span></p>
1573                   </td>
1574 <td>
1575                     <p>
1576                       Zone transfers the server is sending.
1577                     </p>
1578                   </td>
1579 </tr>
1580 <tr>
1581 <td>
1582                     <p><span><strong class="command">notify</strong></span></p>
1583                   </td>
1584 <td>
1585                     <p>
1586                       The NOTIFY protocol.
1587                     </p>
1588                   </td>
1589 </tr>
1590 <tr>
1591 <td>
1592                     <p><span><strong class="command">client</strong></span></p>
1593                   </td>
1594 <td>
1595                     <p>
1596                       Processing of client requests.
1597                     </p>
1598                   </td>
1599 </tr>
1600 <tr>
1601 <td>
1602                     <p><span><strong class="command">unmatched</strong></span></p>
1603                   </td>
1604 <td>
1605                     <p>
1606                       Messages that <span><strong class="command">named</strong></span> was unable to determine the
1607                       class of or for which there was no matching <span><strong class="command">view</strong></span>.
1608                       A one line summary is also logged to the <span><strong class="command">client</strong></span> category.
1609                       This category is best sent to a file or stderr, by
1610                       default it is sent to
1611                       the <span><strong class="command">null</strong></span> channel.
1612                     </p>
1613                   </td>
1614 </tr>
1615 <tr>
1616 <td>
1617                     <p><span><strong class="command">network</strong></span></p>
1618                   </td>
1619 <td>
1620                     <p>
1621                       Network operations.
1622                     </p>
1623                   </td>
1624 </tr>
1625 <tr>
1626 <td>
1627                     <p><span><strong class="command">update</strong></span></p>
1628                   </td>
1629 <td>
1630                     <p>
1631                       Dynamic updates.
1632                     </p>
1633                   </td>
1634 </tr>
1635 <tr>
1636 <td>
1637                     <p><span><strong class="command">update-security</strong></span></p>
1638                   </td>
1639 <td>
1640                     <p>
1641                       Approval and denial of update requests.
1642                     </p>
1643                   </td>
1644 </tr>
1645 <tr>
1646 <td>
1647                     <p><span><strong class="command">queries</strong></span></p>
1648                   </td>
1649 <td>
1650                     <p>
1651                       Specify where queries should be logged to.
1652                     </p>
1653                     <p>
1654                       At startup, specifying the category <span><strong class="command">queries</strong></span> will also
1655                       enable query logging unless <span><strong class="command">querylog</strong></span> option has been
1656                       specified.
1657                     </p>
1658
1659                     <p>
1660                       The query log entry reports the client's IP
1661                       address and port number, and the query name,
1662                       class and type.  Next it reports whether the
1663                       Recursion Desired flag was set (+ if set, -
1664                       if not set), if the query was signed (S),
1665                       EDNS was in use (E), if TCP was used (T), if
1666                       DO (DNSSEC Ok) was set (D), or if CD (Checking
1667                       Disabled) was set (C).  After this the
1668                       destination address the query was sent to is
1669                       reported.
1670                     </p>
1671
1672                     <p>
1673                       <code class="computeroutput">client 127.0.0.1#62536 (www.example.com): query: www.example.com IN AAAA +SE</code>
1674                     </p>
1675                     <p>
1676                       <code class="computeroutput">client ::1#62537 (www.example.net): query: www.example.net IN AAAA -SE</code>
1677                     </p>
1678                     <p>
1679                       (The first part of this log message, showing the
1680                       client address/port number and query name, is
1681                       repeated in all subsequent log messages related
1682                       to the same query.)
1683                     </p>
1684                   </td>
1685 </tr>
1686 <tr>
1687 <td>
1688                     <p><span><strong class="command">query-errors</strong></span></p>
1689                   </td>
1690 <td>
1691                     <p>
1692                       Information about queries that resulted in some
1693                       failure.
1694                     </p>
1695                   </td>
1696 </tr>
1697 <tr>
1698 <td>
1699                     <p><span><strong class="command">dispatch</strong></span></p>
1700                   </td>
1701 <td>
1702                     <p>
1703                       Dispatching of incoming packets to the
1704                       server modules where they are to be processed.
1705                     </p>
1706                   </td>
1707 </tr>
1708 <tr>
1709 <td>
1710                     <p><span><strong class="command">dnssec</strong></span></p>
1711                   </td>
1712 <td>
1713                     <p>
1714                       DNSSEC and TSIG protocol processing.
1715                     </p>
1716                   </td>
1717 </tr>
1718 <tr>
1719 <td>
1720                     <p><span><strong class="command">lame-servers</strong></span></p>
1721                   </td>
1722 <td>
1723                     <p>
1724                       Lame servers.  These are misconfigurations
1725                       in remote servers, discovered by BIND 9 when trying to
1726                       query those servers during resolution.
1727                     </p>
1728                   </td>
1729 </tr>
1730 <tr>
1731 <td>
1732                     <p><span><strong class="command">delegation-only</strong></span></p>
1733                   </td>
1734 <td>
1735                     <p>
1736                       Delegation only.  Logs queries that have been
1737                       forced to NXDOMAIN as the result of a
1738                       delegation-only zone or a
1739                       <span><strong class="command">delegation-only</strong></span> in a
1740                       forward, hint or stub zone declaration.
1741                     </p>
1742                   </td>
1743 </tr>
1744 <tr>
1745 <td>
1746                     <p><span><strong class="command">edns-disabled</strong></span></p>
1747                   </td>
1748 <td>
1749                     <p>
1750                       Log queries that have been forced to use plain
1751                       DNS due to timeouts.  This is often due to
1752                       the remote servers not being RFC 1034 compliant
1753                       (not always returning FORMERR or similar to
1754                       EDNS queries and other extensions to the DNS
1755                       when they are not understood).  In other words, this is
1756                       targeted at servers that fail to respond to
1757                       DNS queries that they don't understand.
1758                     </p>
1759                     <p>
1760                       Note: the log message can also be due to
1761                       packet loss.  Before reporting servers for
1762                       non-RFC 1034 compliance they should be re-tested
1763                       to determine the nature of the non-compliance.
1764                       This testing should prevent or reduce the
1765                       number of false-positive reports.
1766                     </p>
1767                     <p>
1768                       Note: eventually <span><strong class="command">named</strong></span> will have to stop
1769                       treating such timeouts as due to RFC 1034 non
1770                       compliance and start treating it as plain
1771                       packet loss.  Falsely classifying packet
1772                       loss as due to RFC 1034 non compliance impacts
1773                       on DNSSEC validation which requires EDNS for
1774                       the DNSSEC records to be returned.
1775                     </p>
1776                   </td>
1777 </tr>
1778 <tr>
1779 <td>
1780                     <p><span><strong class="command">RPZ</strong></span></p>
1781                   </td>
1782 <td>
1783                     <p>
1784                       Information about errors in response policy zone files,
1785                       rewritten responses, and at the highest
1786                       <span><strong class="command">debug</strong></span> levels, mere rewriting
1787                       attempts.
1788                     </p>
1789                   </td>
1790 </tr>
1791 <tr>
1792 <td>
1793                     <p><span><strong class="command">rate-limit</strong></span></p>
1794                   </td>
1795 <td>
1796                     <p>
1797                       (Only available when <acronym class="acronym">BIND</acronym> 9 is
1798                       configured with the <strong class="userinput"><code>--enable-rrl</code></strong>
1799                       option at compile time.)
1800                     </p>
1801                     <p>
1802                       The start, periodic, and final notices of the
1803                       rate limiting of a stream of responses are logged at
1804                       <span><strong class="command">info</strong></span> severity in this category.
1805                       These messages include a hash value of the domain name
1806                       of the response and the name itself,
1807                       except when there is insufficient memory to record
1808                       the name for the final notice
1809                       The final notice is normally delayed until about one
1810                       minute after rate limit stops.
1811                       A lack of memory can hurry the final notice,
1812                       in which case it starts with an asterisk (*).
1813                       Various internal events are logged at debug 1 level
1814                       and higher.
1815                     </p>
1816                     <p>
1817                       Rate limiting of individual requests
1818                       is logged in the <span><strong class="command">query-errors</strong></span> category.
1819                     </p>
1820                   </td>
1821 </tr>
1822 <tr>
1823 <td>
1824                     <p><span><strong class="command">cname</strong></span></p>
1825                   </td>
1826 <td>
1827                     <p>
1828                       Logs nameservers that are skipped due to them being
1829                       a CNAME rather than A / AAAA records.
1830                     </p>
1831                   </td>
1832 </tr>
1833 </tbody>
1834 </table></div>
1835 </div>
1836 <div class="sect3" lang="en">
1837 <div class="titlepage"><div><div><h4 class="title">
1838 <a name="id2576580"></a>The <span><strong class="command">query-errors</strong></span> Category</h4></div></div></div>
1839 <p>
1840             The <span><strong class="command">query-errors</strong></span> category is
1841             specifically intended for debugging purposes: To identify
1842             why and how specific queries result in responses which
1843             indicate an error.
1844             Messages of this category are therefore only logged
1845             with <span><strong class="command">debug</strong></span> levels.
1846           </p>
1847 <p>
1848             At the debug levels of 1 or higher, each response with the
1849             rcode of SERVFAIL is logged as follows:
1850           </p>
1851 <p>
1852             <code class="computeroutput">client 127.0.0.1#61502: query failed (SERVFAIL) for www.example.com/IN/AAAA at query.c:3880</code>
1853           </p>
1854 <p>
1855             This means an error resulting in SERVFAIL was
1856             detected at line 3880 of source file
1857             <code class="filename">query.c</code>.
1858             Log messages of this level will particularly
1859             help identify the cause of SERVFAIL for an
1860             authoritative server.
1861           </p>
1862 <p>
1863             At the debug levels of 2 or higher, detailed context
1864             information of recursive resolutions that resulted in
1865             SERVFAIL is logged.
1866             The log message will look like as follows:
1867           </p>
1868 <p>
1869
1870             </p>
1871 <pre class="programlisting">
1872 fetch completed at resolver.c:2970 for www.example.com/A
1873 in 30.000183: timed out/success [domain:example.com,
1874 referral:2,restart:7,qrysent:8,timeout:5,lame:0,neterr:0,
1875 badresp:1,adberr:0,findfail:0,valfail:0]
1876             </pre>
1877 <p>
1878           </p>
1879 <p>
1880             The first part before the colon shows that a recursive
1881             resolution for AAAA records of www.example.com completed
1882             in 30.000183 seconds and the final result that led to the
1883             SERVFAIL was determined at line 2970 of source file
1884             <code class="filename">resolver.c</code>.
1885           </p>
1886 <p>
1887             The following part shows the detected final result and the
1888             latest result of DNSSEC validation.
1889             The latter is always success when no validation attempt
1890             is made.
1891             In this example, this query resulted in SERVFAIL probably
1892             because all name servers are down or unreachable, leading
1893             to a timeout in 30 seconds.
1894             DNSSEC validation was probably not attempted.
1895           </p>
1896 <p>
1897             The last part enclosed in square brackets shows statistics
1898             information collected for this particular resolution
1899             attempt.
1900             The <code class="varname">domain</code> field shows the deepest zone
1901             that the resolver reached;
1902             it is the zone where the error was finally detected.
1903             The meaning of the other fields is summarized in the
1904             following table.
1905           </p>
1906 <div class="informaltable"><table border="1">
1907 <colgroup>
1908 <col>
1909 <col>
1910 </colgroup>
1911 <tbody>
1912 <tr>
1913 <td>
1914                     <p><code class="varname">referral</code></p>
1915                   </td>
1916 <td>
1917                     <p>
1918                       The number of referrals the resolver received
1919                       throughout the resolution process.
1920                       In the above example this is 2, which are most
1921                       likely com and example.com.
1922                     </p>
1923                   </td>
1924 </tr>
1925 <tr>
1926 <td>
1927                     <p><code class="varname">restart</code></p>
1928                   </td>
1929 <td>
1930                     <p>
1931                       The number of cycles that the resolver tried
1932                       remote servers at the <code class="varname">domain</code>
1933                       zone.
1934                       In each cycle the resolver sends one query
1935                       (possibly resending it, depending on the response)
1936                       to each known name server of
1937                       the <code class="varname">domain</code> zone.
1938                     </p>
1939                   </td>
1940 </tr>
1941 <tr>
1942 <td>
1943                     <p><code class="varname">qrysent</code></p>
1944                   </td>
1945 <td>
1946                     <p>
1947                       The number of queries the resolver sent at the
1948                       <code class="varname">domain</code> zone.
1949                     </p>
1950                   </td>
1951 </tr>
1952 <tr>
1953 <td>
1954                     <p><code class="varname">timeout</code></p>
1955                   </td>
1956 <td>
1957                     <p>
1958                       The number of timeouts since the resolver
1959                       received the last response.
1960                     </p>
1961                   </td>
1962 </tr>
1963 <tr>
1964 <td>
1965                     <p><code class="varname">lame</code></p>
1966                   </td>
1967 <td>
1968                     <p>
1969                       The number of lame servers the resolver detected
1970                       at the <code class="varname">domain</code> zone.
1971                       A server is detected to be lame either by an
1972                       invalid response or as a result of lookup in
1973                       BIND9's address database (ADB), where lame
1974                       servers are cached.
1975                     </p>
1976                   </td>
1977 </tr>
1978 <tr>
1979 <td>
1980                     <p><code class="varname">neterr</code></p>
1981                   </td>
1982 <td>
1983                     <p>
1984                       The number of erroneous results that the
1985                       resolver encountered in sending queries
1986                       at the <code class="varname">domain</code> zone.
1987                       One common case is the remote server is
1988                       unreachable and the resolver receives an ICMP
1989                       unreachable error message.
1990                     </p>
1991                   </td>
1992 </tr>
1993 <tr>
1994 <td>
1995                     <p><code class="varname">badresp</code></p>
1996                   </td>
1997 <td>
1998                     <p>
1999                       The number of unexpected responses (other than
2000                       <code class="varname">lame</code>) to queries sent by the
2001                       resolver at the <code class="varname">domain</code> zone.
2002                     </p>
2003                   </td>
2004 </tr>
2005 <tr>
2006 <td>
2007                     <p><code class="varname">adberr</code></p>
2008                   </td>
2009 <td>
2010                     <p>
2011                       Failures in finding remote server addresses
2012                       of the <code class="varname">domain</code> zone in the ADB.
2013                       One common case of this is that the remote
2014                       server's name does not have any address records.
2015                     </p>
2016                   </td>
2017 </tr>
2018 <tr>
2019 <td>
2020                     <p><code class="varname">findfail</code></p>
2021                   </td>
2022 <td>
2023                     <p>
2024                       Failures of resolving remote server addresses.
2025                       This is a total number of failures throughout
2026                       the resolution process.
2027                     </p>
2028                   </td>
2029 </tr>
2030 <tr>
2031 <td>
2032                     <p><code class="varname">valfail</code></p>
2033                   </td>
2034 <td>
2035                     <p>
2036                       Failures of DNSSEC validation.
2037                       Validation failures are counted throughout
2038                       the resolution process (not limited to
2039                       the <code class="varname">domain</code> zone), but should
2040                       only happen in <code class="varname">domain</code>.
2041                     </p>
2042                   </td>
2043 </tr>
2044 </tbody>
2045 </table></div>
2046 <p>
2047             At the debug levels of 3 or higher, the same messages
2048             as those at the debug 1 level are logged for other errors
2049             than SERVFAIL.
2050             Note that negative responses such as NXDOMAIN are not
2051             regarded as errors here.
2052           </p>
2053 <p>
2054             At the debug levels of 4 or higher, the same messages
2055             as those at the debug 2 level are logged for other errors
2056             than SERVFAIL.
2057             Unlike the above case of level 3, messages are logged for
2058             negative responses.
2059             This is because any unexpected results can be difficult to
2060             debug in the recursion case.
2061           </p>
2062 </div>
2063 </div>
2064 <div class="sect2" lang="en">
2065 <div class="titlepage"><div><div><h3 class="title">
2066 <a name="id2577236"></a><span><strong class="command">lwres</strong></span> Statement Grammar</h3></div></div></div>
2067 <p>
2068            This is the grammar of the <span><strong class="command">lwres</strong></span>
2069           statement in the <code class="filename">named.conf</code> file:
2070         </p>
2071 <pre class="programlisting"><span><strong class="command">lwres</strong></span> {
2072     [<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>] ;
2073                 [<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>]
2074     [<span class="optional"> view <em class="replaceable"><code>view_name</code></em>; </span>]
2075     [<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>]
2076     [<span class="optional"> ndots <em class="replaceable"><code>number</code></em>; </span>]
2077 };
2078 </pre>
2079 </div>
2080 <div class="sect2" lang="en">
2081 <div class="titlepage"><div><div><h3 class="title">
2082 <a name="id2577309"></a><span><strong class="command">lwres</strong></span> Statement Definition and Usage</h3></div></div></div>
2083 <p>
2084           The <span><strong class="command">lwres</strong></span> statement configures the
2085           name
2086           server to also act as a lightweight resolver server. (See
2087           <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
2088           <span><strong class="command">lwres</strong></span> statements configuring
2089           lightweight resolver servers with different properties.
2090         </p>
2091 <p>
2092           The <span><strong class="command">listen-on</strong></span> statement specifies a
2093           list of
2094           IPv4 addresses (and ports) that this instance of a lightweight
2095           resolver daemon
2096           should accept requests on.  If no port is specified, port 921 is
2097           used.
2098           If this statement is omitted, requests will be accepted on
2099           127.0.0.1,
2100           port 921.
2101         </p>
2102 <p>
2103           The <span><strong class="command">view</strong></span> statement binds this
2104           instance of a
2105           lightweight resolver daemon to a view in the DNS namespace, so that
2106           the
2107           response will be constructed in the same manner as a normal DNS
2108           query
2109           matching this view.  If this statement is omitted, the default view
2110           is
2111           used, and if there is no default view, an error is triggered.
2112         </p>
2113 <p>
2114           The <span><strong class="command">search</strong></span> statement is equivalent to
2115           the
2116           <span><strong class="command">search</strong></span> statement in
2117           <code class="filename">/etc/resolv.conf</code>.  It provides a
2118           list of domains
2119           which are appended to relative names in queries.
2120         </p>
2121 <p>
2122           The <span><strong class="command">ndots</strong></span> statement is equivalent to
2123           the
2124           <span><strong class="command">ndots</strong></span> statement in
2125           <code class="filename">/etc/resolv.conf</code>.  It indicates the
2126           minimum
2127           number of dots in a relative domain name that should result in an
2128           exact match lookup before search path elements are appended.
2129         </p>
2130 </div>
2131 <div class="sect2" lang="en">
2132 <div class="titlepage"><div><div><h3 class="title">
2133 <a name="id2577373"></a><span><strong class="command">masters</strong></span> Statement Grammar</h3></div></div></div>
2134 <pre class="programlisting">
2135 <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> |
2136       <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>] };
2137 </pre>
2138 </div>
2139 <div class="sect2" lang="en">
2140 <div class="titlepage"><div><div><h3 class="title">
2141 <a name="id2577417"></a><span><strong class="command">masters</strong></span> Statement Definition and
2142           Usage</h3></div></div></div>
2143 <p><span><strong class="command">masters</strong></span>
2144           lists allow for a common set of masters to be easily used by
2145           multiple stub and slave zones in their <span><strong class="command">masters</strong></span>
2146           or <span><strong class="command">also-notify</strong></span> lists.
2147         </p>
2148 </div>
2149 <div class="sect2" lang="en">
2150 <div class="titlepage"><div><div><h3 class="title">
2151 <a name="id2577438"></a><span><strong class="command">options</strong></span> Statement Grammar</h3></div></div></div>
2152 <p>
2153           This is the grammar of the <span><strong class="command">options</strong></span>
2154           statement in the <code class="filename">named.conf</code> file:
2155         </p>
2156 <pre class="programlisting"><span><strong class="command">options</strong></span> {
2157     [<span class="optional"> attach-cache <em class="replaceable"><code>cache_name</code></em>; </span>]
2158     [<span class="optional"> version <em class="replaceable"><code>version_string</code></em>; </span>]
2159     [<span class="optional"> hostname <em class="replaceable"><code>hostname_string</code></em>; </span>]
2160     [<span class="optional"> server-id <em class="replaceable"><code>server_id_string</code></em>; </span>]
2161     [<span class="optional"> directory <em class="replaceable"><code>path_name</code></em>; </span>]
2162     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2163     [<span class="optional"> managed-keys-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2164     [<span class="optional"> named-xfer <em class="replaceable"><code>path_name</code></em>; </span>]
2165     [<span class="optional"> tkey-gssapi-keytab <em class="replaceable"><code>path_name</code></em>; </span>]
2166     [<span class="optional"> tkey-gssapi-credential <em class="replaceable"><code>principal</code></em>; </span>]
2167     [<span class="optional"> tkey-domain <em class="replaceable"><code>domainname</code></em>; </span>]
2168     [<span class="optional"> tkey-dhkey <em class="replaceable"><code>key_name</code></em> <em class="replaceable"><code>key_tag</code></em>; </span>]
2169     [<span class="optional"> cache-file <em class="replaceable"><code>path_name</code></em>; </span>]
2170     [<span class="optional"> dump-file <em class="replaceable"><code>path_name</code></em>; </span>]
2171     [<span class="optional"> bindkeys-file <em class="replaceable"><code>path_name</code></em>; </span>]
2172     [<span class="optional"> secroots-file <em class="replaceable"><code>path_name</code></em>; </span>]
2173     [<span class="optional"> session-keyfile <em class="replaceable"><code>path_name</code></em>; </span>]
2174     [<span class="optional"> session-keyname <em class="replaceable"><code>key_name</code></em>; </span>]
2175     [<span class="optional"> session-keyalg <em class="replaceable"><code>algorithm_id</code></em>; </span>]
2176     [<span class="optional"> memstatistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2177     [<span class="optional"> memstatistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2178     [<span class="optional"> pid-file <em class="replaceable"><code>path_name</code></em>; </span>]
2179     [<span class="optional"> recursing-file <em class="replaceable"><code>path_name</code></em>; </span>]
2180     [<span class="optional"> statistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2181     [<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>]
2182     [<span class="optional"> auth-nxdomain <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2183     [<span class="optional"> deallocate-on-exit <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2184     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em>; </span>]
2185     [<span class="optional"> fake-iquery <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2186     [<span class="optional"> fetch-glue <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2187     [<span class="optional"> flush-zones-on-shutdown <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2188     [<span class="optional"> has-old-clients <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2189     [<span class="optional"> host-statistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2190     [<span class="optional"> host-statistics-max <em class="replaceable"><code>number</code></em>; </span>]
2191     [<span class="optional"> minimal-responses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2192     [<span class="optional"> multiple-cnames <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2193     [<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>]
2194     [<span class="optional"> recursion <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2195     [<span class="optional"> request-nsid <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2196     [<span class="optional"> rfc2308-type1 <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2197     [<span class="optional"> use-id-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2198     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2199     [<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>]
2200     [<span class="optional"> dnssec-enable <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2201     [<span class="optional"> dnssec-validation (<em class="replaceable"><code>yes_or_no</code></em> | <code class="constant">auto</code>); </span>]
2202     [<span class="optional"> dnssec-lookaside ( <em class="replaceable"><code>auto</code></em> |
2203                         <em class="replaceable"><code>no</code></em> |
2204                         <em class="replaceable"><code>domain</code></em> trust-anchor <em class="replaceable"><code>domain</code></em> ); </span>]
2205     [<span class="optional"> dnssec-must-be-secure <em class="replaceable"><code>domain yes_or_no</code></em>; </span>]
2206     [<span class="optional"> dnssec-accept-expired <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2207     [<span class="optional"> forward ( <em class="replaceable"><code>only</code></em> | <em class="replaceable"><code>first</code></em> ); </span>]
2208     [<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>]
2209     [<span class="optional"> dual-stack-servers [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] {
2210         ( <em class="replaceable"><code>domain_name</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] |
2211           <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ) ;
2212         ... }; </span>]
2213     [<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> )
2214         ( <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-dup-records ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2216     [<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>]
2217     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2218     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2219     [<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>]
2220     [<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>]
2221     [<span class="optional"> check-sibling <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2222     [<span class="optional"> check-spf ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2223     [<span class="optional"> allow-new-zones { <em class="replaceable"><code>yes_or_no</code></em> }; </span>]
2224     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2225     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2226     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2227     [<span class="optional"> allow-query-cache { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2228     [<span class="optional"> allow-query-cache-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2229     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2230     [<span class="optional"> allow-recursion { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2231     [<span class="optional"> allow-recursion-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2232     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2233     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2234     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2235     [<span class="optional"> dnssec-update-mode ( <em class="replaceable"><code>maintain</code></em> | <em class="replaceable"><code>no-resign</code></em> ); </span>]
2236     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2237     [<span class="optional"> dnssec-loadkeys-interval <em class="replaceable"><code>number</code></em>; </span>]
2238     [<span class="optional"> dnssec-secure-to-insecure <em class="replaceable"><code>yes_or_no</code></em> ;</span>]
2239     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2240     [<span class="optional"> allow-v6-synthesis { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2241     [<span class="optional"> blackhole { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2242     [<span class="optional"> no-case-compress { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2243     [<span class="optional"> use-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2244     [<span class="optional"> avoid-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2245     [<span class="optional"> use-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2246     [<span class="optional"> avoid-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2247     [<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>]
2248     [<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>]
2249     [<span class="optional"> query-source ( ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2250         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
2251         [<span class="optional"> address ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2252         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
2253     [<span class="optional"> query-source-v6 ( ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2254         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
2255         [<span class="optional"> address ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2256         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
2257     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2258     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
2259     [<span class="optional"> queryport-pool-updateinterval <em class="replaceable"><code>number</code></em>; </span>]
2260     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em>; </span>]
2261     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em>; </span>]
2262     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em>; </span>]
2263     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em>; </span>]
2264     [<span class="optional"> reserved-sockets <em class="replaceable"><code>number</code></em>; </span>]
2265     [<span class="optional"> recursive-clients <em class="replaceable"><code>number</code></em>; </span>]
2266     [<span class="optional"> tcp-clients <em class="replaceable"><code>number</code></em>; </span>]
2267     [<span class="optional"> clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2268     [<span class="optional"> max-clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2269     [<span class="optional"> fetches-per-server <em class="replaceable"><code>number</code></em> [<span class="optional"><em class="replaceable"><code>(drop | fail)</code></em></span>]; </span>]
2270     [<span class="optional"> fetch-quota-params <em class="replaceable"><code>number fixedpoint fixedpoint fixedpoint</code></em> ; </span>]
2271     [<span class="optional"> fetches-per-zone<em class="replaceable"><code>number</code></em> [<span class="optional"><em class="replaceable"><code>(drop | fail)</code></em></span>]; </span>]
2272     [<span class="optional"> serial-query-rate <em class="replaceable"><code>number</code></em>; </span>]
2273     [<span class="optional"> serial-queries <em class="replaceable"><code>number</code></em>; </span>]
2274     [<span class="optional"> tcp-listen-queue <em class="replaceable"><code>number</code></em>; </span>]
2275     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em>; </span>]
2276     [<span class="optional"> transfers-in  <em class="replaceable"><code>number</code></em>; </span>]
2277     [<span class="optional"> transfers-out <em class="replaceable"><code>number</code></em>; </span>]
2278     [<span class="optional"> transfers-per-ns <em class="replaceable"><code>number</code></em>; </span>]
2279     [<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>]
2280     [<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>]
2281     [<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>]
2282     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
2283                              [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
2284     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2285     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
2286     [<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>]
2287     [<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>]
2288     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2289     [<span class="optional"> also-notify { <em class="replaceable"><code>ip_addr</code></em>
2290                     [<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>] ;
2291                     [<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>]
2292     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em>; </span>]
2293     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
2294     [<span class="optional"> coresize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2295     [<span class="optional"> datasize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2296     [<span class="optional"> files <em class="replaceable"><code>size_spec</code></em> ; </span>]
2297     [<span class="optional"> stacksize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2298     [<span class="optional"> cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2299     [<span class="optional"> heartbeat-interval <em class="replaceable"><code>number</code></em>; </span>]
2300     [<span class="optional"> interface-interval <em class="replaceable"><code>number</code></em>; </span>]
2301     [<span class="optional"> statistics-interval <em class="replaceable"><code>number</code></em>; </span>]
2302     [<span class="optional"> topology { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2303     [<span class="optional"> sortlist { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2304     [<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>] };
2305     [<span class="optional"> lame-ttl <em class="replaceable"><code>number</code></em>; </span>]
2306     [<span class="optional"> max-ncache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2307     [<span class="optional"> max-cache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2308     [<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>]
2309     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
2310     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
2311     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
2312     [<span class="optional"> min-roots <em class="replaceable"><code>number</code></em>; </span>]
2313     [<span class="optional"> use-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2314     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2315     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2316     [<span class="optional"> treat-cr-as-space <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2317     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2318     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2319     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2320     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2321     [<span class="optional"> port <em class="replaceable"><code>ip_port</code></em>; </span>]
2322     [<span class="optional"> additional-from-auth <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2323     [<span class="optional"> additional-from-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2324     [<span class="optional"> random-device <em class="replaceable"><code>path_name</code></em> ; </span>]
2325     [<span class="optional"> max-cache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2326     [<span class="optional"> match-mapped-addresses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2327     [<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>]
2328     [<span class="optional"> filter-aaaa { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2329     [<span class="optional"> dns64 <em class="replaceable"><code>ipv6-prefix</code></em> {
2330         [<span class="optional"> clients { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2331         [<span class="optional"> mapped { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2332         [<span class="optional"> exclude { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2333         [<span class="optional"> suffix IPv6-address; </span>]
2334         [<span class="optional"> recursive-only <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2335         [<span class="optional"> break-dnssec <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2336     }; </span>];
2337     [<span class="optional"> dns64-server <em class="replaceable"><code>name</code></em> </span>]
2338     [<span class="optional"> dns64-contact <em class="replaceable"><code>name</code></em> </span>]
2339     [<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>]
2340     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2341     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2342     [<span class="optional"> max-rsa-exponent-size <em class="replaceable"><code>number</code></em>; </span>]
2343     [<span class="optional"> root-delegation-only [<span class="optional"> exclude { <em class="replaceable"><code>namelist</code></em> } </span>] ; </span>]
2344     [<span class="optional"> querylog <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2345     [<span class="optional"> disable-algorithms <em class="replaceable"><code>domain</code></em> { <em class="replaceable"><code>algorithm</code></em>;
2346                                 [<span class="optional"> <em class="replaceable"><code>algorithm</code></em>; </span>] }; </span>]
2347     [<span class="optional"> acache-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2348     [<span class="optional"> acache-cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2349     [<span class="optional"> max-acache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2350     [<span class="optional"> max-recursion-depth <em class="replaceable"><code>number</code></em> ; </span>]
2351     [<span class="optional"> max-recursion-queries <em class="replaceable"><code>number</code></em> ; </span>]
2352     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
2353     [<span class="optional"> empty-server <em class="replaceable"><code>name</code></em> ; </span>]
2354     [<span class="optional"> empty-contact <em class="replaceable"><code>name</code></em> ; </span>]
2355     [<span class="optional"> empty-zones-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2356     [<span class="optional"> disable-empty-zone <em class="replaceable"><code>zone_name</code></em> ; </span>]
2357     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2358     [<span class="optional"> zero-no-soa-ttl-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2359     [<span class="optional"> resolver-query-timeout <em class="replaceable"><code>number</code></em> ; </span>]
2360     [<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>]
2361     [<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>]
2362     [<span class="optional"> rate-limit {
2363         [<span class="optional"> responses-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2364         [<span class="optional"> referrals-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2365         [<span class="optional"> nodata-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2366         [<span class="optional"> nxdomains-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2367         [<span class="optional"> errors-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2368         [<span class="optional"> all-per-second <em class="replaceable"><code>number</code></em> ; </span>]
2369         [<span class="optional"> window <em class="replaceable"><code>number</code></em> ; </span>]
2370         [<span class="optional"> log-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2371         [<span class="optional"> qps-scale <em class="replaceable"><code>number</code></em> ; </span>]
2372         [<span class="optional"> ipv4-prefix-length <em class="replaceable"><code>number</code></em> ; </span>]
2373         [<span class="optional"> ipv6-prefix-length <em class="replaceable"><code>number</code></em> ; </span>]
2374         [<span class="optional"> slip <em class="replaceable"><code>number</code></em> ; </span>]
2375         [<span class="optional"> exempt-clients  { <em class="replaceable"><code>address_match_list</code></em> } ; </span>]
2376         [<span class="optional"> max-table-size <em class="replaceable"><code>number</code></em> ; </span>]
2377         [<span class="optional"> min-table-size <em class="replaceable"><code>number</code></em> ; </span>]
2378     } ; </span>]
2379     [<span class="optional"> response-policy {
2380         zone <em class="replaceable"><code>zone_name</code></em>
2381         [<span class="optional"> policy <em class="replaceable"><code>(given | disabled | passthru |
2382                   nxdomain | nodata | cname domain</code></em>) </span>]
2383         ; [<span class="optional">...</span>]
2384     } [<span class="optional"> recursive-only <em class="replaceable"><code>yes_or_no</code></em> </span>]
2385       [<span class="optional"> max-policy-ttl <em class="replaceable"><code>number</code></em> </span>]
2386       [<span class="optional"> break-dnssec <em class="replaceable"><code>yes_or_no</code></em> </span>]
2387       [<span class="optional"> min-ns-dots <em class="replaceable"><code>number</code></em> </span>]
2388     ; </span>]
2389 };
2390 </pre>
2391 </div>
2392 <div class="sect2" lang="en">
2393 <div class="titlepage"><div><div><h3 class="title">
2394 <a name="options"></a><span><strong class="command">options</strong></span> Statement Definition and
2395           Usage</h3></div></div></div>
2396 <p>
2397           The <span><strong class="command">options</strong></span> statement sets up global
2398           options
2399           to be used by <acronym class="acronym">BIND</acronym>. This statement
2400           may appear only
2401           once in a configuration file. If there is no <span><strong class="command">options</strong></span>
2402           statement, an options block with each option set to its default will
2403           be used.
2404         </p>
2405 <div class="variablelist"><dl>
2406 <dt><span class="term"><span><strong class="command">attach-cache</strong></span></span></dt>
2407 <dd>
2408 <p>
2409                   Allows multiple views to share a single cache
2410                   database.
2411                   Each view has its own cache database by default, but
2412                   if multiple views have the same operational policy
2413                   for name resolution and caching, those views can
2414                   share a single cache to save memory and possibly
2415                   improve resolution efficiency by using this option.
2416                 </p>
2417 <p>
2418                   The <span><strong class="command">attach-cache</strong></span> option
2419                   may also be specified in <span><strong class="command">view</strong></span>
2420                   statements, in which case it overrides the
2421                   global <span><strong class="command">attach-cache</strong></span> option.
2422                 </p>
2423 <p>
2424                   The <em class="replaceable"><code>cache_name</code></em> specifies
2425                   the cache to be shared.
2426                   When the <span><strong class="command">named</strong></span> server configures
2427                   views which are supposed to share a cache, it
2428                   creates a cache with the specified name for the
2429                   first view of these sharing views.
2430                   The rest of the views will simply refer to the
2431                   already created cache.
2432                 </p>
2433 <p>
2434                   One common configuration to share a cache would be to
2435                   allow all views to share a single cache.
2436                   This can be done by specifying
2437                   the <span><strong class="command">attach-cache</strong></span> as a global
2438                   option with an arbitrary name.
2439                 </p>
2440 <p>
2441                   Another possible operation is to allow a subset of
2442                   all views to share a cache while the others to
2443                   retain their own caches.
2444                   For example, if there are three views A, B, and C,
2445                   and only A and B should share a cache, specify the
2446                   <span><strong class="command">attach-cache</strong></span> option as a view A (or
2447                   B)'s option, referring to the other view name:
2448                 </p>
2449 <pre class="programlisting">
2450   view "A" {
2451     // this view has its own cache
2452     ...
2453   };
2454   view "B" {
2455     // this view refers to A's cache
2456     attach-cache "A";
2457   };
2458   view "C" {
2459     // this view has its own cache
2460     ...
2461   };
2462 </pre>
2463 <p>
2464                   Views that share a cache must have the same policy
2465                   on configurable parameters that may affect caching.
2466                   The current implementation requires the following
2467                   configurable options be consistent among these
2468                   views:
2469                   <span><strong class="command">check-names</strong></span>,
2470                   <span><strong class="command">cleaning-interval</strong></span>,
2471                   <span><strong class="command">dnssec-accept-expired</strong></span>,
2472                   <span><strong class="command">dnssec-validation</strong></span>,
2473                   <span><strong class="command">max-cache-ttl</strong></span>,
2474                   <span><strong class="command">max-ncache-ttl</strong></span>,
2475                   <span><strong class="command">max-cache-size</strong></span>, and
2476                   <span><strong class="command">zero-no-soa-ttl</strong></span>.
2477                 </p>
2478 <p>
2479                   Note that there may be other parameters that may
2480                   cause confusion if they are inconsistent for
2481                   different views that share a single cache.
2482                   For example, if these views define different sets of
2483                   forwarders that can return different answers for the
2484                   same question, sharing the answer does not make
2485                   sense or could even be harmful.
2486                   It is administrator's responsibility to ensure
2487                   configuration differences in different views do
2488                   not cause disruption with a shared cache.
2489                 </p>
2490 </dd>
2491 <dt><span class="term"><span><strong class="command">directory</strong></span></span></dt>
2492 <dd><p>
2493                 The working directory of the server.
2494                 Any non-absolute pathnames in the configuration file will be
2495                 taken
2496                 as relative to this directory. The default location for most
2497                 server
2498                 output files (e.g. <code class="filename">named.run</code>)
2499                 is this directory.
2500                 If a directory is not specified, the working directory
2501                 defaults to `<code class="filename">.</code>', the directory from
2502                 which the server
2503                 was started. The directory specified should be an absolute
2504                 path.
2505               </p></dd>
2506 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
2507 <dd><p>
2508                 When performing dynamic update of secure zones, the
2509                 directory where the public and private DNSSEC key files
2510                 should be found, if different than the current working
2511                 directory.  (Note that this option has no effect on the
2512                 paths for files containing non-DNSSEC keys such as
2513                 <code class="filename">bind.keys</code>,
2514                 <code class="filename">rndc.key</code> or
2515                 <code class="filename">session.key</code>.)
2516               </p></dd>
2517 <dt><span class="term"><span><strong class="command">managed-keys-directory</strong></span></span></dt>
2518 <dd>
2519 <p>
2520                 Specifies the directory in which to store the files that
2521                 track managed DNSSEC keys.  By default, this is the working
2522                 directory.
2523               </p>
2524 <p>
2525                 If <span><strong class="command">named</strong></span> is not configured to use views,
2526                 then managed keys for the server will be tracked in a single
2527                 file called <code class="filename">managed-keys.bind</code>.
2528                 Otherwise, managed keys will be tracked in separate files,
2529                 one file per view; each file name will be the SHA256 hash
2530                 of the view name, followed by the extension
2531                 <code class="filename">.mkeys</code>.
2532               </p>
2533 </dd>
2534 <dt><span class="term"><span><strong class="command">named-xfer</strong></span></span></dt>
2535 <dd><p>
2536                 <span class="emphasis"><em>This option is obsolete.</em></span> It
2537                 was used in <acronym class="acronym">BIND</acronym> 8 to specify
2538                 the pathname to the <span><strong class="command">named-xfer</strong></span>
2539                 program.  In <acronym class="acronym">BIND</acronym> 9, no separate
2540                 <span><strong class="command">named-xfer</strong></span> program is needed;
2541                 its functionality is built into the name server.
2542               </p></dd>
2543 <dt><span class="term"><span><strong class="command">tkey-gssapi-keytab</strong></span></span></dt>
2544 <dd><p>
2545                 The KRB5 keytab file to use for GSS-TSIG updates. If
2546                 this option is set and tkey-gssapi-credential is not
2547                 set, then updates will be allowed with any key
2548                 matching a principal in the specified keytab.
2549               </p></dd>
2550 <dt><span class="term"><span><strong class="command">tkey-gssapi-credential</strong></span></span></dt>
2551 <dd><p>
2552                 The security credential with which the server should
2553                 authenticate keys requested by the GSS-TSIG protocol.
2554                 Currently only Kerberos 5 authentication is available
2555                 and the credential is a Kerberos principal which the
2556                 server can acquire through the default system key
2557                 file, normally <code class="filename">/etc/krb5.keytab</code>.
2558                 The location keytab file can be overridden using the
2559                 tkey-gssapi-keytab option. Normally this principal is
2560                 of the form "<strong class="userinput"><code>DNS/</code></strong><code class="varname">server.domain</code>".
2561                 To use GSS-TSIG, <span><strong class="command">tkey-domain</strong></span> must
2562                 also be set if a specific keytab is not set with
2563                 tkey-gssapi-keytab.
2564               </p></dd>
2565 <dt><span class="term"><span><strong class="command">tkey-domain</strong></span></span></dt>
2566 <dd><p>
2567                 The domain appended to the names of all shared keys
2568                 generated with <span><strong class="command">TKEY</strong></span>.  When a
2569                 client requests a <span><strong class="command">TKEY</strong></span> exchange,
2570                 it may or may not specify the desired name for the
2571                 key. If present, the name of the shared key will
2572                 be <code class="varname">client specified part</code> +
2573                 <code class="varname">tkey-domain</code>.  Otherwise, the
2574                 name of the shared key will be <code class="varname">random hex
2575                 digits</code> + <code class="varname">tkey-domain</code>.
2576                 In most cases, the <span><strong class="command">domainname</strong></span>
2577                 should be the server's domain name, or an otherwise
2578                 non-existent subdomain like
2579                 "_tkey.<code class="varname">domainname</code>".  If you are
2580                 using GSS-TSIG, this variable must be defined, unless
2581                 you specify a specific keytab using tkey-gssapi-keytab.
2582               </p></dd>
2583 <dt><span class="term"><span><strong class="command">tkey-dhkey</strong></span></span></dt>
2584 <dd><p>
2585                 The Diffie-Hellman key used by the server
2586                 to generate shared keys with clients using the Diffie-Hellman
2587                 mode
2588                 of <span><strong class="command">TKEY</strong></span>. The server must be
2589                 able to load the
2590                 public and private keys from files in the working directory.
2591                 In
2592                 most cases, the keyname should be the server's host name.
2593               </p></dd>
2594 <dt><span class="term"><span><strong class="command">cache-file</strong></span></span></dt>
2595 <dd><p>
2596                 This is for testing only.  Do not use.
2597               </p></dd>
2598 <dt><span class="term"><span><strong class="command">dump-file</strong></span></span></dt>
2599 <dd><p>
2600                 The pathname of the file the server dumps
2601                 the database to when instructed to do so with
2602                 <span><strong class="command">rndc dumpdb</strong></span>.
2603                 If not specified, the default is <code class="filename">named_dump.db</code>.
2604               </p></dd>
2605 <dt><span class="term"><span><strong class="command">memstatistics-file</strong></span></span></dt>
2606 <dd><p>
2607                 The pathname of the file the server writes memory
2608                 usage statistics to on exit. If not specified,
2609                 the default is <code class="filename">named.memstats</code>.
2610               </p></dd>
2611 <dt><span class="term"><span><strong class="command">pid-file</strong></span></span></dt>
2612 <dd><p>
2613                 The pathname of the file the server writes its process ID
2614                 in. If not specified, the default is
2615                 <code class="filename">/var/run/named/named.pid</code>.
2616                 The PID file is used by programs that want to send signals to
2617                 the running
2618                 name server. Specifying <span><strong class="command">pid-file none</strong></span> disables the
2619                 use of a PID file &#8212; no file will be written and any
2620                 existing one will be removed.  Note that <span><strong class="command">none</strong></span>
2621                 is a keyword, not a filename, and therefore is not enclosed
2622                 in
2623                 double quotes.
2624               </p></dd>
2625 <dt><span class="term"><span><strong class="command">recursing-file</strong></span></span></dt>
2626 <dd><p>
2627                 The pathname of the file the server dumps
2628                 the queries that are currently recursing when instructed
2629                 to do so with <span><strong class="command">rndc recursing</strong></span>.
2630                 If not specified, the default is <code class="filename">named.recursing</code>.
2631               </p></dd>
2632 <dt><span class="term"><span><strong class="command">statistics-file</strong></span></span></dt>
2633 <dd><p>
2634                 The pathname of the file the server appends statistics
2635                 to when instructed to do so using <span><strong class="command">rndc stats</strong></span>.
2636                 If not specified, the default is <code class="filename">named.stats</code> in the
2637                 server's current directory.  The format of the file is
2638                 described
2639                 in <a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
2640               </p></dd>
2641 <dt><span class="term"><span><strong class="command">bindkeys-file</strong></span></span></dt>
2642 <dd><p>
2643                 The pathname of a file to override the built-in trusted
2644                 keys provided by <span><strong class="command">named</strong></span>.
2645                 See the discussion of <span><strong class="command">dnssec-lookaside</strong></span>
2646                 and <span><strong class="command">dnssec-validation</strong></span> for details.
2647                 If not specified, the default is
2648                 <code class="filename">/etc/bind.keys</code>.
2649               </p></dd>
2650 <dt><span class="term"><span><strong class="command">secroots-file</strong></span></span></dt>
2651 <dd><p>
2652                 The pathname of the file the server dumps
2653                 security roots to when instructed to do so with
2654                 <span><strong class="command">rndc secroots</strong></span>.
2655                 If not specified, the default is
2656                 <code class="filename">named.secroots</code>.
2657               </p></dd>
2658 <dt><span class="term"><span><strong class="command">session-keyfile</strong></span></span></dt>
2659 <dd><p>
2660                 The pathname of the file into which to write a TSIG
2661                 session key generated by <span><strong class="command">named</strong></span> for use by
2662                 <span><strong class="command">nsupdate -l</strong></span>.  If not specified, the
2663                 default is <code class="filename">/var/run/named/session.key</code>.
2664                 (See <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>, and in
2665                 particular the discussion of the
2666                 <span><strong class="command">update-policy</strong></span> statement's
2667                 <strong class="userinput"><code>local</code></strong> option for more
2668                 information about this feature.)
2669               </p></dd>
2670 <dt><span class="term"><span><strong class="command">session-keyname</strong></span></span></dt>
2671 <dd><p>
2672                 The key name to use for the TSIG session key.
2673                 If not specified, the default is "local-ddns".
2674               </p></dd>
2675 <dt><span class="term"><span><strong class="command">session-keyalg</strong></span></span></dt>
2676 <dd><p>
2677                 The algorithm to use for the TSIG session key.
2678                 Valid values are hmac-sha1, hmac-sha224, hmac-sha256,
2679                 hmac-sha384, hmac-sha512 and hmac-md5.  If not
2680                 specified, the default is hmac-sha256.
2681               </p></dd>
2682 <dt><span class="term"><span><strong class="command">port</strong></span></span></dt>
2683 <dd><p>
2684                 The UDP/TCP port number the server uses for
2685                 receiving and sending DNS protocol traffic.
2686                 The default is 53.  This option is mainly intended for server
2687                 testing;
2688                 a server using a port other than 53 will not be able to
2689                 communicate with
2690                 the global DNS.
2691               </p></dd>
2692 <dt><span class="term"><span><strong class="command">random-device</strong></span></span></dt>
2693 <dd><p>
2694                 The source of entropy to be used by the server.  Entropy is
2695                 primarily needed
2696                 for DNSSEC operations, such as TKEY transactions and dynamic
2697                 update of signed
2698                 zones.  This options specifies the device (or file) from which
2699                 to read
2700                 entropy.  If this is a file, operations requiring entropy will
2701                 fail when the
2702                 file has been exhausted.  If not specified, the default value
2703                 is
2704                 <code class="filename">/dev/random</code>
2705                 (or equivalent) when present, and none otherwise.  The
2706                 <span><strong class="command">random-device</strong></span> option takes
2707                 effect during
2708                 the initial configuration load at server startup time and
2709                 is ignored on subsequent reloads.
2710               </p></dd>
2711 <dt><span class="term"><span><strong class="command">preferred-glue</strong></span></span></dt>
2712 <dd><p>
2713                 If specified, the listed type (A or AAAA) will be emitted
2714                 before other glue
2715                 in the additional section of a query response.
2716                 The default is not to prefer any type (NONE).
2717               </p></dd>
2718 <dt>
2719 <a name="root_delegation_only"></a><span class="term"><span><strong class="command">root-delegation-only</strong></span></span>
2720 </dt>
2721 <dd>
2722 <p>
2723                 Turn on enforcement of delegation-only in TLDs
2724                 (top level domains) and root zones with an optional
2725                 exclude list.
2726               </p>
2727 <p>
2728                 DS queries are expected to be made to and be answered by
2729                 delegation only zones.  Such queries and responses are
2730                 treated as an exception to delegation-only processing
2731                 and are not converted to NXDOMAIN responses provided
2732                 a CNAME is not discovered at the query name.
2733               </p>
2734 <p>
2735                 If a delegation only zone server also serves a child
2736                 zone it is not always possible to determine whether
2737                 an answer comes from the delegation only zone or the
2738                 child zone.  SOA NS and DNSKEY records are apex
2739                 only records and a matching response that contains
2740                 these records or DS is treated as coming from a
2741                 child zone.  RRSIG records are also examined to see
2742                 if they are signed by a child zone or not.  The
2743                 authority section is also examined to see if there
2744                 is evidence that the answer is from the child zone.
2745                 Answers that are determined to be from a child zone
2746                 are not converted to NXDOMAIN responses.  Despite
2747                 all these checks there is still a possibility of
2748                 false negatives when a child zone is being served.
2749               </p>
2750 <p>
2751                 Similarly false positives can arise from empty nodes
2752                 (no records at the name) in the delegation only zone
2753                 when the query type is not ANY.
2754               </p>
2755 <p>
2756                 Note some TLDs are not delegation only (e.g. "DE", "LV",
2757                 "US" and "MUSEUM").  This list is not exhaustive.
2758               </p>
2759 <pre class="programlisting">
2760 options {
2761         root-delegation-only exclude { "de"; "lv"; "us"; "museum"; };
2762 };
2763 </pre>
2764 </dd>
2765 <dt><span class="term"><span><strong class="command">disable-algorithms</strong></span></span></dt>
2766 <dd><p>
2767                 Disable the specified DNSSEC algorithms at and below the
2768                 specified name.
2769                 Multiple <span><strong class="command">disable-algorithms</strong></span>
2770                 statements are allowed.
2771                 Only the most specific will be applied.
2772               </p></dd>
2773 <dt><span class="term"><span><strong class="command">dnssec-lookaside</strong></span></span></dt>
2774 <dd>
2775 <p>
2776                 When set, <span><strong class="command">dnssec-lookaside</strong></span> provides the
2777                 validator with an alternate method to validate DNSKEY
2778                 records at the top of a zone.  When a DNSKEY is at or
2779                 below a domain specified by the deepest
2780                 <span><strong class="command">dnssec-lookaside</strong></span>, and the normal DNSSEC
2781                 validation has left the key untrusted, the trust-anchor
2782                 will be appended to the key name and a DLV record will be
2783                 looked up to see if it can validate the key.  If the DLV
2784                 record validates a DNSKEY (similarly to the way a DS
2785                 record does) the DNSKEY RRset is deemed to be trusted.
2786               </p>
2787 <p>
2788                 If <span><strong class="command">dnssec-lookaside</strong></span> is set to
2789                 <strong class="userinput"><code>auto</code></strong>, then built-in default
2790                 values for the DLV domain and trust anchor will be
2791                 used, along with a built-in key for validation.
2792               </p>
2793 <p>
2794                 If <span><strong class="command">dnssec-lookaside</strong></span> is set to
2795                 <strong class="userinput"><code>no</code></strong>, then dnssec-lookaside
2796                 is not used.
2797               </p>
2798 <p>
2799                 The default DLV key is stored in the file
2800                 <code class="filename">bind.keys</code>;
2801                 <span><strong class="command">named</strong></span> will load that key at
2802                 startup if <span><strong class="command">dnssec-lookaside</strong></span> is set to
2803                 <code class="constant">auto</code>.  A copy of the file is
2804                 installed along with <acronym class="acronym">BIND</acronym> 9, and is
2805                 current as of the release date.  If the DLV key expires, a
2806                 new copy of <code class="filename">bind.keys</code> can be downloaded
2807                 from <a href="https://www.isc.org/solutions/dlv/" target="_top">https://www.isc.org/solutions/dlv/</a>.
2808               </p>
2809 <p>
2810                 (To prevent problems if <code class="filename">bind.keys</code> is
2811                 not found, the current key is also compiled in to
2812                 <span><strong class="command">named</strong></span>.  Relying on this is not
2813                 recommended, however, as it requires <span><strong class="command">named</strong></span>
2814                 to be recompiled with a new key when the DLV key expires.)
2815               </p>
2816 <p>
2817                 NOTE: <span><strong class="command">named</strong></span> only loads certain specific
2818                 keys from <code class="filename">bind.keys</code>:  those for the
2819                 DLV zone and for the DNS root zone.  The file cannot be
2820                 used to store keys for other zones.
2821               </p>
2822 </dd>
2823 <dt><span class="term"><span><strong class="command">dnssec-must-be-secure</strong></span></span></dt>
2824 <dd><p>
2825                 Specify hierarchies which must be or may not be secure
2826                 (signed and validated).  If <strong class="userinput"><code>yes</code></strong>,
2827                 then <span><strong class="command">named</strong></span> will only accept answers if
2828                 they are secure.  If <strong class="userinput"><code>no</code></strong>, then normal
2829                 DNSSEC validation applies allowing for insecure answers to
2830                 be accepted.  The specified domain must be under a
2831                 <span><strong class="command">trusted-keys</strong></span> or
2832                 <span><strong class="command">managed-keys</strong></span> statement, or
2833                 <span><strong class="command">dnssec-lookaside</strong></span> must be active.
2834               </p></dd>
2835 <dt><span class="term"><span><strong class="command">dns64</strong></span></span></dt>
2836 <dd>
2837 <p>
2838                 This directive instructs <span><strong class="command">named</strong></span> to
2839                 return mapped IPv4 addresses to AAAA queries when
2840                 there are no AAAA records.  It is intended to be
2841                 used in conjunction with a NAT64.  Each
2842                 <span><strong class="command">dns64</strong></span> defines one DNS64 prefix.
2843                 Multiple DNS64 prefixes can be defined.
2844               </p>
2845 <p>
2846                 Compatible IPv6 prefixes have lengths of 32, 40, 48, 56,
2847                 64 and 96 as per RFC 6052.
2848               </p>
2849 <p>
2850                 Additionally a reverse IP6.ARPA zone will be created for
2851                 the prefix to provide a mapping from the IP6.ARPA names
2852                 to the corresponding IN-ADDR.ARPA names using synthesized
2853                 CNAMEs.  <span><strong class="command">dns64-server</strong></span> and
2854                 <span><strong class="command">dns64-contact</strong></span> can be used to specify
2855                 the name of the server and contact for the zones. These
2856                 are settable at the view / options level.  These are
2857                 not settable on a per-prefix basis.
2858               </p>
2859 <p>
2860                 Each <span><strong class="command">dns64</strong></span> supports an optional
2861                 <span><strong class="command">clients</strong></span> ACL that determines which
2862                 clients are affected by this directive.  If not defined,
2863                 it defaults to <strong class="userinput"><code>any;</code></strong>.
2864               </p>
2865 <p>
2866                 Each <span><strong class="command">dns64</strong></span> supports an optional
2867                 <span><strong class="command">mapped</strong></span> ACL that selects which
2868                 IPv4 addresses are to be mapped in the corresponding
2869                 A RRset.  If not defined it defaults to
2870                 <strong class="userinput"><code>any;</code></strong>.
2871               </p>
2872 <p>
2873                 Normally, DNS64 won't apply to a domain name that
2874                 owns one or more AAAA records; these records will
2875                 simply be returned.  The optional
2876                 <span><strong class="command">exclude</strong></span> ACL allows specification
2877                 of a list of IPv6 addresses that will be ignored
2878                 if they appear in a domain name's AAAA records, and
2879                 DNS64 will be applied to any A records the domain
2880                 name owns.  If not defined, <span><strong class="command">exclude</strong></span>
2881                 defaults to none.
2882               </p>
2883 <p>
2884                 A optional <span><strong class="command">suffix</strong></span> can also
2885                 be defined to set the bits trailing the mapped
2886                 IPv4 address bits.  By default these bits are
2887                 set to <strong class="userinput"><code>::</code></strong>.  The bits
2888                 matching the prefix and mapped IPv4 address
2889                 must be zero.
2890               </p>
2891 <p>
2892                 If <span><strong class="command">recursive-only</strong></span> is set to
2893                 <span><strong class="command">yes</strong></span> the DNS64 synthesis will
2894                 only happen for recursive queries.  The default
2895                 is <span><strong class="command">no</strong></span>.
2896               </p>
2897 <p>
2898                 If <span><strong class="command">break-dnssec</strong></span> is set to
2899                 <span><strong class="command">yes</strong></span> the DNS64 synthesis will
2900                 happen even if the result, if validated, would
2901                 cause a DNSSEC validation failure.  If this option
2902                 is set to <span><strong class="command">no</strong></span> (the default), the DO
2903                 is set on the incoming query, and there are RRSIGs on
2904                 the applicable records, then synthesis will not happen.
2905               </p>
2906 <pre class="programlisting">
2907         acl rfc1918 { 10/8; 192.168/16; 172.16/12; };
2908
2909         dns64 64:FF9B::/96 {
2910                 clients { any; };
2911                 mapped { !rfc1918; any; };
2912                 exclude { 64:FF9B::/96; ::ffff:0000:0000/96; };
2913                 suffix ::;
2914         };
2915 </pre>
2916 </dd>
2917 <dt><span class="term"><span><strong class="command">dnssec-update-mode</strong></span></span></dt>
2918 <dd>
2919 <p>
2920                   If this option is set to its default value of
2921                   <code class="literal">maintain</code> in a zone of type
2922                   <code class="literal">master</code> which is DNSSEC-signed
2923                   and configured to allow dynamic updates (see
2924                   <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>), and
2925                   if <span><strong class="command">named</strong></span> has access to the
2926                   private signing key(s) for the zone, then
2927                   <span><strong class="command">named</strong></span> will automatically sign all new
2928                   or changed records and maintain signatures for the zone
2929                   by regenerating RRSIG records whenever they approach
2930                   their expiration date.
2931                 </p>
2932 <p>
2933                   If the option is changed to <code class="literal">no-resign</code>,
2934                   then <span><strong class="command">named</strong></span> will sign all new or
2935                   changed records, but scheduled maintenance of
2936                   signatures is disabled.
2937                 </p>
2938 <p>
2939                   With either of these settings, <span><strong class="command">named</strong></span>
2940                   will reject updates to a DNSSEC-signed zone when the
2941                   signing keys are inactive or unavailable to
2942                   <span><strong class="command">named</strong></span>.  (A planned third option,
2943                   <code class="literal">external</code>, will disable all automatic
2944                   signing and allow DNSSEC data to be submitted into a zone
2945                   via dynamic update; this is not yet implemented.)
2946                 </p>
2947 </dd>
2948 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
2949 <dd>
2950 <p>
2951                 If <strong class="userinput"><code>full</code></strong>, the server will collect
2952                 statistical data on all zones (unless specifically
2953                 turned off on a per-zone basis by specifying
2954                 <span><strong class="command">zone-statistics terse</strong></span> or
2955                 <span><strong class="command">zone-statistics none</strong></span>
2956                 in the <span><strong class="command">zone</strong></span> statement).
2957                 The default is <strong class="userinput"><code>terse</code></strong>, providing
2958                 minimal statistics on zones (including name and
2959                 current serial number, but not query type
2960                 counters).
2961               </p>
2962 <p>
2963                 These statistics may be accessed via the
2964                 <span><strong class="command">statistics-channel</strong></span> or
2965                 using <span><strong class="command">rndc stats</strong></span>, which
2966                 will dump them to the file listed
2967                 in the <span><strong class="command">statistics-file</strong></span>.  See
2968                 also <a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
2969               </p>
2970 <p>
2971                 For backward compatibility with earlier versions
2972                 of BIND 9, the <span><strong class="command">zone-statistics</strong></span>
2973                 option can also accept <strong class="userinput"><code>yes</code></strong>
2974                 or <strong class="userinput"><code>no</code></strong>, which have the same
2975                 effect as <strong class="userinput"><code>full</code></strong> and
2976                 <strong class="userinput"><code>terse</code></strong>, respectively.
2977               </p>
2978 </dd>
2979 </dl></div>
2980 <div class="sect3" lang="en">
2981 <div class="titlepage"><div><div><h4 class="title">
2982 <a name="boolean_options"></a>Boolean Options</h4></div></div></div>
2983 <div class="variablelist"><dl>
2984 <dt><span class="term"><span><strong class="command">allow-new-zones</strong></span></span></dt>
2985 <dd><p>
2986                   If <strong class="userinput"><code>yes</code></strong>, then zones can be
2987                   added at runtime via <span><strong class="command">rndc addzone</strong></span>
2988                   or deleted via <span><strong class="command">rndc delzone</strong></span>.
2989                   The default is <strong class="userinput"><code>no</code></strong>.
2990                 </p></dd>
2991 <dt><span class="term"><span><strong class="command">auth-nxdomain</strong></span></span></dt>
2992 <dd><p>
2993                   If <strong class="userinput"><code>yes</code></strong>, then the <span><strong class="command">AA</strong></span> bit
2994                   is always set on NXDOMAIN responses, even if the server is
2995                   not actually
2996                   authoritative. The default is <strong class="userinput"><code>no</code></strong>;
2997                   this is
2998                   a change from <acronym class="acronym">BIND</acronym> 8. If you
2999                   are using very old DNS software, you
3000                   may need to set it to <strong class="userinput"><code>yes</code></strong>.
3001                 </p></dd>
3002 <dt><span class="term"><span><strong class="command">deallocate-on-exit</strong></span></span></dt>
3003 <dd><p>
3004                   This option was used in <acronym class="acronym">BIND</acronym>
3005                   8 to enable checking
3006                   for memory leaks on exit. <acronym class="acronym">BIND</acronym> 9 ignores the option and always performs
3007                   the checks.
3008                 </p></dd>
3009 <dt><span class="term"><span><strong class="command">memstatistics</strong></span></span></dt>
3010 <dd><p>
3011                   Write memory statistics to the file specified by
3012                   <span><strong class="command">memstatistics-file</strong></span> at exit.
3013                   The default is <strong class="userinput"><code>no</code></strong> unless
3014                   '-m record' is specified on the command line in
3015                   which case it is <strong class="userinput"><code>yes</code></strong>.
3016                 </p></dd>
3017 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
3018 <dd>
3019 <p>
3020                   If <strong class="userinput"><code>yes</code></strong>, then the
3021                   server treats all zones as if they are doing zone transfers
3022                   across
3023                   a dial-on-demand dialup link, which can be brought up by
3024                   traffic
3025                   originating from this server. This has different effects
3026                   according
3027                   to zone type and concentrates the zone maintenance so that
3028                   it all
3029                   happens in a short interval, once every <span><strong class="command">heartbeat-interval</strong></span> and
3030                   hopefully during the one call. It also suppresses some of
3031                   the normal
3032                   zone maintenance traffic. The default is <strong class="userinput"><code>no</code></strong>.
3033                 </p>
3034 <p>
3035                   The <span><strong class="command">dialup</strong></span> option
3036                   may also be specified in the <span><strong class="command">view</strong></span> and
3037                   <span><strong class="command">zone</strong></span> statements,
3038                   in which case it overrides the global <span><strong class="command">dialup</strong></span>
3039                   option.
3040                 </p>
3041 <p>
3042                   If the zone is a master zone, then the server will send out a
3043                   NOTIFY
3044                   request to all the slaves (default). This should trigger the
3045                   zone serial
3046                   number check in the slave (providing it supports NOTIFY)
3047                   allowing the slave
3048                   to verify the zone while the connection is active.
3049                   The set of servers to which NOTIFY is sent can be controlled
3050                   by
3051                   <span><strong class="command">notify</strong></span> and <span><strong class="command">also-notify</strong></span>.
3052                 </p>
3053 <p>
3054                   If the
3055                   zone is a slave or stub zone, then the server will suppress
3056                   the regular
3057                   "zone up to date" (refresh) queries and only perform them
3058                   when the
3059                   <span><strong class="command">heartbeat-interval</strong></span> expires in
3060                   addition to sending
3061                   NOTIFY requests.
3062                 </p>
3063 <p>
3064                   Finer control can be achieved by using
3065                   <strong class="userinput"><code>notify</code></strong> which only sends NOTIFY
3066                   messages,
3067                   <strong class="userinput"><code>notify-passive</code></strong> which sends NOTIFY
3068                   messages and
3069                   suppresses the normal refresh queries, <strong class="userinput"><code>refresh</code></strong>
3070                   which suppresses normal refresh processing and sends refresh
3071                   queries
3072                   when the <span><strong class="command">heartbeat-interval</strong></span>
3073                   expires, and
3074                   <strong class="userinput"><code>passive</code></strong> which just disables normal
3075                   refresh
3076                   processing.
3077                 </p>
3078 <div class="informaltable"><table border="1">
3079 <colgroup>
3080 <col>
3081 <col>
3082 <col>
3083 <col>
3084 </colgroup>
3085 <tbody>
3086 <tr>
3087 <td>
3088                           <p>
3089                             dialup mode
3090                           </p>
3091                         </td>
3092 <td>
3093                           <p>
3094                             normal refresh
3095                           </p>
3096                         </td>
3097 <td>
3098                           <p>
3099                             heart-beat refresh
3100                           </p>
3101                         </td>
3102 <td>
3103                           <p>
3104                             heart-beat notify
3105                           </p>
3106                         </td>
3107 </tr>
3108 <tr>
3109 <td>
3110                           <p><span><strong class="command">no</strong></span> (default)</p>
3111                         </td>
3112 <td>
3113                           <p>
3114                             yes
3115                           </p>
3116                         </td>
3117 <td>
3118                           <p>
3119                             no
3120                           </p>
3121                         </td>
3122 <td>
3123                           <p>
3124                             no
3125                           </p>
3126                         </td>
3127 </tr>
3128 <tr>
3129 <td>
3130                           <p><span><strong class="command">yes</strong></span></p>
3131                         </td>
3132 <td>
3133                           <p>
3134                             no
3135                           </p>
3136                         </td>
3137 <td>
3138                           <p>
3139                             yes
3140                           </p>
3141                         </td>
3142 <td>
3143                           <p>
3144                             yes
3145                           </p>
3146                         </td>
3147 </tr>
3148 <tr>
3149 <td>
3150                           <p><span><strong class="command">notify</strong></span></p>
3151                         </td>
3152 <td>
3153                           <p>
3154                             yes
3155                           </p>
3156                         </td>
3157 <td>
3158                           <p>
3159                             no
3160                           </p>
3161                         </td>
3162 <td>
3163                           <p>
3164                             yes
3165                           </p>
3166                         </td>
3167 </tr>
3168 <tr>
3169 <td>
3170                           <p><span><strong class="command">refresh</strong></span></p>
3171                         </td>
3172 <td>
3173                           <p>
3174                             no
3175                           </p>
3176                         </td>
3177 <td>
3178                           <p>
3179                             yes
3180                           </p>
3181                         </td>
3182 <td>
3183                           <p>
3184                             no
3185                           </p>
3186                         </td>
3187 </tr>
3188 <tr>
3189 <td>
3190                           <p><span><strong class="command">passive</strong></span></p>
3191                         </td>
3192 <td>
3193                           <p>
3194                             no
3195                           </p>
3196                         </td>
3197 <td>
3198                           <p>
3199                             no
3200                           </p>
3201                         </td>
3202 <td>
3203                           <p>
3204                             no
3205                           </p>
3206                         </td>
3207 </tr>
3208 <tr>
3209 <td>
3210                           <p><span><strong class="command">notify-passive</strong></span></p>
3211                         </td>
3212 <td>
3213                           <p>
3214                             no
3215                           </p>
3216                         </td>
3217 <td>
3218                           <p>
3219                             no
3220                           </p>
3221                         </td>
3222 <td>
3223                           <p>
3224                             yes
3225                           </p>
3226                         </td>
3227 </tr>
3228 </tbody>
3229 </table></div>
3230 <p>
3231                   Note that normal NOTIFY processing is not affected by
3232                   <span><strong class="command">dialup</strong></span>.
3233                 </p>
3234 </dd>
3235 <dt><span class="term"><span><strong class="command">fake-iquery</strong></span></span></dt>
3236 <dd><p>
3237                   In <acronym class="acronym">BIND</acronym> 8, this option
3238                   enabled simulating the obsolete DNS query type
3239                   IQUERY. <acronym class="acronym">BIND</acronym> 9 never does
3240                   IQUERY simulation.
3241                 </p></dd>
3242 <dt><span class="term"><span><strong class="command">fetch-glue</strong></span></span></dt>
3243 <dd><p>
3244                   This option is obsolete.
3245                   In BIND 8, <strong class="userinput"><code>fetch-glue yes</code></strong>
3246                   caused the server to attempt to fetch glue resource records
3247                   it
3248                   didn't have when constructing the additional
3249                   data section of a response.  This is now considered a bad
3250                   idea
3251                   and BIND 9 never does it.
3252                 </p></dd>
3253 <dt><span class="term"><span><strong class="command">flush-zones-on-shutdown</strong></span></span></dt>
3254 <dd><p>
3255                   When the nameserver exits due receiving SIGTERM,
3256                   flush or do not flush any pending zone writes.  The default
3257                   is
3258                   <span><strong class="command">flush-zones-on-shutdown</strong></span> <strong class="userinput"><code>no</code></strong>.
3259                 </p></dd>
3260 <dt><span class="term"><span><strong class="command">has-old-clients</strong></span></span></dt>
3261 <dd><p>
3262                   This option was incorrectly implemented
3263                   in <acronym class="acronym">BIND</acronym> 8, and is ignored by <acronym class="acronym">BIND</acronym> 9.
3264                   To achieve the intended effect
3265                   of
3266                   <span><strong class="command">has-old-clients</strong></span> <strong class="userinput"><code>yes</code></strong>, specify
3267                   the two separate options <span><strong class="command">auth-nxdomain</strong></span> <strong class="userinput"><code>yes</code></strong>
3268                   and <span><strong class="command">rfc2308-type1</strong></span> <strong class="userinput"><code>no</code></strong> instead.
3269                 </p></dd>
3270 <dt><span class="term"><span><strong class="command">host-statistics</strong></span></span></dt>
3271 <dd><p>
3272                   In BIND 8, this enables keeping of
3273                   statistics for every host that the name server interacts
3274                   with.
3275                   Not implemented in BIND 9.
3276                 </p></dd>
3277 <dt><span class="term"><span><strong class="command">maintain-ixfr-base</strong></span></span></dt>
3278 <dd><p>
3279                   <span class="emphasis"><em>This option is obsolete</em></span>.
3280                   It was used in <acronym class="acronym">BIND</acronym> 8 to
3281                   determine whether a transaction log was
3282                   kept for Incremental Zone Transfer. <acronym class="acronym">BIND</acronym> 9 maintains a transaction
3283                   log whenever possible.  If you need to disable outgoing
3284                   incremental zone
3285                   transfers, use <span><strong class="command">provide-ixfr</strong></span> <strong class="userinput"><code>no</code></strong>.
3286                 </p></dd>
3287 <dt><span class="term"><span><strong class="command">minimal-responses</strong></span></span></dt>
3288 <dd><p>
3289                   If <strong class="userinput"><code>yes</code></strong>, then when generating
3290                   responses the server will only add records to the authority
3291                   and additional data sections when they are required (e.g.
3292                   delegations, negative responses).  This may improve the
3293                   performance of the server.
3294                   The default is <strong class="userinput"><code>no</code></strong>.
3295                 </p></dd>
3296 <dt><span class="term"><span><strong class="command">multiple-cnames</strong></span></span></dt>
3297 <dd><p>
3298                   This option was used in <acronym class="acronym">BIND</acronym> 8 to allow
3299                   a domain name to have multiple CNAME records in violation of
3300                   the DNS standards.  <acronym class="acronym">BIND</acronym> 9.2 onwards
3301                   always strictly enforces the CNAME rules both in master
3302                   files and dynamic updates.
3303                 </p></dd>
3304 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
3305 <dd>
3306 <p>
3307                   If <strong class="userinput"><code>yes</code></strong> (the default),
3308                   DNS NOTIFY messages are sent when a zone the server is
3309                   authoritative for
3310                   changes, see <a href="Bv9ARM.ch04.html#notify" title="Notify">the section called &#8220;Notify&#8221;</a>.  The messages are
3311                   sent to the
3312                   servers listed in the zone's NS records (except the master
3313                   server identified
3314                   in the SOA MNAME field), and to any servers listed in the
3315                   <span><strong class="command">also-notify</strong></span> option.
3316                 </p>
3317 <p>
3318                   If <strong class="userinput"><code>master-only</code></strong>, notifies are only
3319                   sent
3320                   for master zones.
3321                   If <strong class="userinput"><code>explicit</code></strong>, notifies are sent only
3322                   to
3323                   servers explicitly listed using <span><strong class="command">also-notify</strong></span>.
3324                   If <strong class="userinput"><code>no</code></strong>, no notifies are sent.
3325                 </p>
3326 <p>
3327                   The <span><strong class="command">notify</strong></span> option may also be
3328                   specified in the <span><strong class="command">zone</strong></span>
3329                   statement,
3330                   in which case it overrides the <span><strong class="command">options notify</strong></span> statement.
3331                   It would only be necessary to turn off this option if it
3332                   caused slaves
3333                   to crash.
3334                 </p>
3335 </dd>
3336 <dt><span class="term"><span><strong class="command">notify-to-soa</strong></span></span></dt>
3337 <dd><p>
3338                   If <strong class="userinput"><code>yes</code></strong> do not check the nameservers
3339                   in the NS RRset against the SOA MNAME.  Normally a NOTIFY
3340                   message is not sent to the SOA MNAME (SOA ORIGIN) as it is
3341                   supposed to contain the name of the ultimate master.
3342                   Sometimes, however, a slave is listed as the SOA MNAME in
3343                   hidden master configurations and in that case you would
3344                   want the ultimate master to still send NOTIFY messages to
3345                   all the nameservers listed in the NS RRset.
3346                 </p></dd>
3347 <dt><span class="term"><span><strong class="command">recursion</strong></span></span></dt>
3348 <dd><p>
3349                   If <strong class="userinput"><code>yes</code></strong>, and a
3350                   DNS query requests recursion, then the server will attempt
3351                   to do
3352                   all the work required to answer the query. If recursion is
3353                   off
3354                   and the server does not already know the answer, it will
3355                   return a
3356                   referral response. The default is
3357                   <strong class="userinput"><code>yes</code></strong>.
3358                   Note that setting <span><strong class="command">recursion no</strong></span> does not prevent
3359                   clients from getting data from the server's cache; it only
3360                   prevents new data from being cached as an effect of client
3361                   queries.
3362                   Caching may still occur as an effect the server's internal
3363                   operation, such as NOTIFY address lookups.
3364                   See also <span><strong class="command">fetch-glue</strong></span> above.
3365                 </p></dd>
3366 <dt><span class="term"><span><strong class="command">request-nsid</strong></span></span></dt>
3367 <dd><p>
3368                   If <strong class="userinput"><code>yes</code></strong>, then an empty EDNS(0)
3369                   NSID (Name Server Identifier) option is sent with all
3370                   queries to authoritative name servers during iterative
3371                   resolution. If the authoritative server returns an NSID
3372                   option in its response, then its contents are logged in
3373                   the <span><strong class="command">resolver</strong></span> category at level
3374                   <span><strong class="command">info</strong></span>.
3375                   The default is <strong class="userinput"><code>no</code></strong>.
3376                 </p></dd>
3377 <dt><span class="term"><span><strong class="command">rfc2308-type1</strong></span></span></dt>
3378 <dd>
3379 <p>
3380                   Setting this to <strong class="userinput"><code>yes</code></strong> will
3381                   cause the server to send NS records along with the SOA
3382                   record for negative
3383                   answers. The default is <strong class="userinput"><code>no</code></strong>.
3384                 </p>
3385 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3386 <h3 class="title">Note</h3>
3387 <p>
3388                     Not yet implemented in <acronym class="acronym">BIND</acronym>
3389                     9.
3390                   </p>
3391 </div>
3392 </dd>
3393 <dt><span class="term"><span><strong class="command">use-id-pool</strong></span></span></dt>
3394 <dd><p>
3395                   <span class="emphasis"><em>This option is obsolete</em></span>.
3396                   <acronym class="acronym">BIND</acronym> 9 always allocates query
3397                   IDs from a pool.
3398                 </p></dd>
3399 <dt><span class="term"><span><strong class="command">use-ixfr</strong></span></span></dt>
3400 <dd><p>
3401                   <span class="emphasis"><em>This option is obsolete</em></span>.
3402                   If you need to disable IXFR to a particular server or
3403                   servers, see
3404                   the information on the <span><strong class="command">provide-ixfr</strong></span> option
3405                   in <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3406             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3407             Usage&#8221;</a>.
3408                   See also
3409                   <a href="Bv9ARM.ch04.html#incremental_zone_transfers" title="Incremental Zone Transfers (IXFR)">the section called &#8220;Incremental Zone Transfers (IXFR)&#8221;</a>.
3410                 </p></dd>
3411 <dt><span class="term"><span><strong class="command">provide-ixfr</strong></span></span></dt>
3412 <dd><p>
3413                   See the description of
3414                   <span><strong class="command">provide-ixfr</strong></span> in
3415                   <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3416             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3417             Usage&#8221;</a>.
3418                 </p></dd>
3419 <dt><span class="term"><span><strong class="command">request-ixfr</strong></span></span></dt>
3420 <dd><p>
3421                   See the description of
3422                   <span><strong class="command">request-ixfr</strong></span> in
3423                   <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3424             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3425             Usage&#8221;</a>.
3426                 </p></dd>
3427 <dt><span class="term"><span><strong class="command">treat-cr-as-space</strong></span></span></dt>
3428 <dd><p>
3429                   This option was used in <acronym class="acronym">BIND</acronym>
3430                   8 to make
3431                   the server treat carriage return ("<span><strong class="command">\r</strong></span>") characters the same way
3432                   as a space or tab character,
3433                   to facilitate loading of zone files on a UNIX system that
3434                   were generated
3435                   on an NT or DOS machine. In <acronym class="acronym">BIND</acronym> 9, both UNIX "<span><strong class="command">\n</strong></span>"
3436                   and NT/DOS "<span><strong class="command">\r\n</strong></span>" newlines
3437                   are always accepted,
3438                   and the option is ignored.
3439                 </p></dd>
3440 <dt>
3441 <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>
3442 </dt>
3443 <dd>
3444 <p>
3445                   These options control the behavior of an authoritative
3446                   server when
3447                   answering queries which have additional data, or when
3448                   following CNAME
3449                   and DNAME chains.
3450                 </p>
3451 <p>
3452                   When both of these options are set to <strong class="userinput"><code>yes</code></strong>
3453                   (the default) and a
3454                   query is being answered from authoritative data (a zone
3455                   configured into the server), the additional data section of
3456                   the
3457                   reply will be filled in using data from other authoritative
3458                   zones
3459                   and from the cache.  In some situations this is undesirable,
3460                   such
3461                   as when there is concern over the correctness of the cache,
3462                   or
3463                   in servers where slave zones may be added and modified by
3464                   untrusted third parties.  Also, avoiding
3465                   the search for this additional data will speed up server
3466                   operations
3467                   at the possible expense of additional queries to resolve
3468                   what would
3469                   otherwise be provided in the additional section.
3470                 </p>
3471 <p>
3472                   For example, if a query asks for an MX record for host <code class="literal">foo.example.com</code>,
3473                   and the record found is "<code class="literal">MX 10 mail.example.net</code>", normally the address
3474                   records (A and AAAA) for <code class="literal">mail.example.net</code> will be provided as well,
3475                   if known, even though they are not in the example.com zone.
3476                   Setting these options to <span><strong class="command">no</strong></span>
3477                   disables this behavior and makes
3478                   the server only search for additional data in the zone it
3479                   answers from.
3480                 </p>
3481 <p>
3482                   These options are intended for use in authoritative-only
3483                   servers, or in authoritative-only views.  Attempts to set
3484                   them to <span><strong class="command">no</strong></span> without also
3485                   specifying
3486                   <span><strong class="command">recursion no</strong></span> will cause the
3487                   server to
3488                   ignore the options and log a warning message.
3489                 </p>
3490 <p>
3491                   Specifying <span><strong class="command">additional-from-cache no</strong></span> actually
3492                   disables the use of the cache not only for additional data
3493                   lookups
3494                   but also when looking up the answer.  This is usually the
3495                   desired
3496                   behavior in an authoritative-only server where the
3497                   correctness of
3498                   the cached data is an issue.
3499                 </p>
3500 <p>
3501                   When a name server is non-recursively queried for a name
3502                   that is not
3503                   below the apex of any served zone, it normally answers with
3504                   an
3505                   "upwards referral" to the root servers or the servers of
3506                   some other
3507                   known parent of the query name.  Since the data in an
3508                   upwards referral
3509                   comes from the cache, the server will not be able to provide
3510                   upwards
3511                   referrals when <span><strong class="command">additional-from-cache no</strong></span>
3512                   has been specified.  Instead, it will respond to such
3513                   queries
3514                   with REFUSED.  This should not cause any problems since
3515                   upwards referrals are not required for the resolution
3516                   process.
3517                 </p>
3518 </dd>
3519 <dt><span class="term"><span><strong class="command">match-mapped-addresses</strong></span></span></dt>
3520 <dd>
3521 <p>
3522                   If <strong class="userinput"><code>yes</code></strong>, then an
3523                   IPv4-mapped IPv6 address will match any address match
3524                   list entries that match the corresponding IPv4 address.
3525                 </p>
3526 <p>
3527                   This option was introduced to work around a kernel quirk
3528                   in some operating systems that causes IPv4 TCP
3529                   connections, such as zone transfers, to be accepted on an
3530                   IPv6 socket using mapped addresses.  This caused address
3531                   match lists designed for IPv4 to fail to match.  However,
3532                   <span><strong class="command">named</strong></span> now solves this problem
3533                   internally.  The use of this option is discouraged.
3534                 </p>
3535 </dd>
3536 <dt><span class="term"><span><strong class="command">filter-aaaa-on-v4</strong></span></span></dt>
3537 <dd>
3538 <p>
3539                   This option is only available when
3540                   <acronym class="acronym">BIND</acronym> 9 is compiled with the
3541                   <strong class="userinput"><code>--enable-filter-aaaa</code></strong> option on the
3542                   "configure" command line.  It is intended to help the
3543                   transition from IPv4 to IPv6 by not giving IPv6 addresses
3544                   to DNS clients unless they have connections to the IPv6
3545                   Internet.  This is not recommended unless absolutely
3546                   necessary.  The default is <strong class="userinput"><code>no</code></strong>.
3547                   The <span><strong class="command">filter-aaaa-on-v4</strong></span> option
3548                   may also be specified in <span><strong class="command">view</strong></span> statements
3549                   to override the global <span><strong class="command">filter-aaaa-on-v4</strong></span>
3550                   option.
3551                 </p>
3552 <p>
3553                   If <strong class="userinput"><code>yes</code></strong>,
3554                   the DNS client is at an IPv4 address, in <span><strong class="command">filter-aaaa</strong></span>,
3555                   and if the response does not include DNSSEC signatures,
3556                   then all AAAA records are deleted from the response.
3557                   This filtering applies to all responses and not only
3558                   authoritative responses.
3559                 </p>
3560 <p>
3561                   If <strong class="userinput"><code>break-dnssec</code></strong>,
3562                   then AAAA records are deleted even when dnssec is enabled.
3563                   As suggested by the name, this makes the response not verify,
3564                   because the DNSSEC protocol is designed detect deletions.
3565                 </p>
3566 <p>
3567                   This mechanism can erroneously cause other servers to
3568                   not give AAAA records to their clients.
3569                   A recursing server with both IPv6 and IPv4 network connections
3570                   that queries an authoritative server using this mechanism
3571                   via IPv4 will be denied AAAA records even if its client is
3572                   using IPv6.
3573                 </p>
3574 <p>
3575                   This mechanism is applied to authoritative as well as
3576                   non-authoritative records.
3577                   A client using IPv4 that is not allowed recursion can
3578                   erroneously be given AAAA records because the server is not
3579                   allowed to check for A records.
3580                 </p>
3581 <p>
3582                   Some AAAA records are given to IPv4 clients in glue records.
3583                   IPv4 clients that are servers can then erroneously
3584                   answer requests for AAAA records received via IPv4.
3585                 </p>
3586 </dd>
3587 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
3588 <dd>
3589 <p>
3590                   When <strong class="userinput"><code>yes</code></strong> and the server loads a new
3591                   version of a master zone from its zone file or receives a
3592                   new version of a slave file via zone transfer, it will
3593                   compare the new version to the previous one and calculate
3594                   a set of differences.  The differences are then logged in
3595                   the zone's journal file such that the changes can be
3596                   transmitted to downstream slaves as an incremental zone
3597                   transfer.
3598                 </p>
3599 <p>
3600                   By allowing incremental zone transfers to be used for
3601                   non-dynamic zones, this option saves bandwidth at the
3602                   expense of increased CPU and memory consumption at the
3603                   master.
3604                   In particular, if the new version of a zone is completely
3605                   different from the previous one, the set of differences
3606                   will be of a size comparable to the combined size of the
3607                   old and new zone version, and the server will need to
3608                   temporarily allocate memory to hold this complete
3609                   difference set.
3610                 </p>
3611 <p><span><strong class="command">ixfr-from-differences</strong></span>
3612                   also accepts <span><strong class="command">master</strong></span> and
3613                   <span><strong class="command">slave</strong></span> at the view and options
3614                   levels which causes
3615                   <span><strong class="command">ixfr-from-differences</strong></span> to be enabled for
3616                   all <span><strong class="command">master</strong></span> or
3617                   <span><strong class="command">slave</strong></span> zones respectively.
3618                   It is off by default.
3619                 </p>
3620 </dd>
3621 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
3622 <dd><p>
3623                   This should be set when you have multiple masters for a zone
3624                   and the
3625                   addresses refer to different machines.  If <strong class="userinput"><code>yes</code></strong>, <span><strong class="command">named</strong></span> will
3626                   not log
3627                   when the serial number on the master is less than what <span><strong class="command">named</strong></span>
3628                   currently
3629                   has.  The default is <strong class="userinput"><code>no</code></strong>.
3630                 </p></dd>
3631 <dt><span class="term"><span><strong class="command">dnssec-enable</strong></span></span></dt>
3632 <dd><p>
3633                   This indicates whether DNSSEC-related resource
3634                   records are to be returned by <span><strong class="command">named</strong></span>.
3635                   If set to <strong class="userinput"><code>no</code></strong>,
3636                   <span><strong class="command">named</strong></span> will not return DNSSEC-related
3637                   resource records unless specifically queried for.
3638                   The default is <strong class="userinput"><code>yes</code></strong>.
3639                 </p></dd>
3640 <dt><span class="term"><span><strong class="command">dnssec-validation</strong></span></span></dt>
3641 <dd>
3642 <p>
3643                   Enable DNSSEC validation in <span><strong class="command">named</strong></span>.
3644                   Note <span><strong class="command">dnssec-enable</strong></span> also needs to be
3645                   set to <strong class="userinput"><code>yes</code></strong> to be effective.
3646                   If set to <strong class="userinput"><code>no</code></strong>, DNSSEC validation
3647                   is disabled.  If set to <strong class="userinput"><code>auto</code></strong>,
3648                   DNSSEC validation is enabled, and a default
3649                   trust-anchor for the DNS root zone is used.  If set to
3650                   <strong class="userinput"><code>yes</code></strong>, DNSSEC validation is enabled,
3651                   but a trust anchor must be manually configured using
3652                   a <span><strong class="command">trusted-keys</strong></span> or
3653                   <span><strong class="command">managed-keys</strong></span> statement.  The default
3654                   is <strong class="userinput"><code>yes</code></strong>.
3655                 </p>
3656 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3657 <h3 class="title">Note</h3>
3658 <p>
3659                     Whenever the resolver sends out queries to an
3660                     EDNS-compliant server, it always sets the DO bit
3661                     indicating it can support DNSSEC responses even if
3662                     <span><strong class="command">dnssec-validation</strong></span> is off.
3663                   </p>
3664 </div>
3665 </dd>
3666 <dt><span class="term"><span><strong class="command">dnssec-accept-expired</strong></span></span></dt>
3667 <dd><p>
3668                   Accept expired signatures when verifying DNSSEC signatures.
3669                   The default is <strong class="userinput"><code>no</code></strong>.
3670                   Setting this option to <strong class="userinput"><code>yes</code></strong>
3671                   leaves <span><strong class="command">named</strong></span> vulnerable to
3672                   replay attacks.
3673                 </p></dd>
3674 <dt><span class="term"><span><strong class="command">querylog</strong></span></span></dt>
3675 <dd><p>
3676                   Specify whether query logging should be started when <span><strong class="command">named</strong></span>
3677                   starts.
3678                   If <span><strong class="command">querylog</strong></span> is not specified,
3679                   then the query logging
3680                   is determined by the presence of the logging category <span><strong class="command">queries</strong></span>.
3681                 </p></dd>
3682 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
3683 <dd>
3684 <p>
3685                   This option is used to restrict the character set and syntax
3686                   of
3687                   certain domain names in master files and/or DNS responses
3688                   received
3689                   from the network.  The default varies according to usage
3690                   area.  For
3691                   <span><strong class="command">master</strong></span> zones the default is <span><strong class="command">fail</strong></span>.
3692                   For <span><strong class="command">slave</strong></span> zones the default
3693                   is <span><strong class="command">warn</strong></span>.
3694                   For answers received from the network (<span><strong class="command">response</strong></span>)
3695                   the default is <span><strong class="command">ignore</strong></span>.
3696                 </p>
3697 <p>
3698                   The rules for legal hostnames and mail domains are derived
3699                   from RFC 952 and RFC 821 as modified by RFC 1123.
3700                 </p>
3701 <p><span><strong class="command">check-names</strong></span>
3702                   applies to the owner names of A, AAAA and MX records.
3703                   It also applies to the domain names in the RDATA of NS, SOA,
3704                   MX, and SRV records.
3705                   It also applies to the RDATA of PTR records where the owner
3706                   name indicated that it is a reverse lookup of a hostname
3707                   (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, or IP6.INT).
3708                 </p>
3709 </dd>
3710 <dt><span class="term"><span><strong class="command">check-dup-records</strong></span></span></dt>
3711 <dd><p>
3712                   Check master zones for records that are treated as different
3713                   by DNSSEC but are semantically equal in plain DNS.  The
3714                   default is to <span><strong class="command">warn</strong></span>.  Other possible
3715                   values are <span><strong class="command">fail</strong></span> and
3716                   <span><strong class="command">ignore</strong></span>.
3717                 </p></dd>
3718 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
3719 <dd><p>
3720                   Check whether the MX record appears to refer to a IP address.
3721                   The default is to <span><strong class="command">warn</strong></span>.  Other possible
3722                   values are <span><strong class="command">fail</strong></span> and
3723                   <span><strong class="command">ignore</strong></span>.
3724                 </p></dd>
3725 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
3726 <dd><p>
3727                   This option is used to check for non-terminal wildcards.
3728                   The use of non-terminal wildcards is almost always as a
3729                   result of a failure
3730                   to understand the wildcard matching algorithm (RFC 1034).
3731                   This option
3732                   affects master zones.  The default (<span><strong class="command">yes</strong></span>) is to check
3733                   for non-terminal wildcards and issue a warning.
3734                 </p></dd>
3735 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
3736 <dd>
3737 <p>
3738                   Perform post load zone integrity checks on master
3739                   zones.  This checks that MX and SRV records refer
3740                   to address (A or AAAA) records and that glue
3741                   address records exist for delegated zones.  For
3742                   MX and SRV records only in-zone hostnames are
3743                   checked (for out-of-zone hostnames use
3744                   <span><strong class="command">named-checkzone</strong></span>).
3745                   For NS records only names below top of zone are
3746                   checked (for out-of-zone names and glue consistency
3747                   checks use <span><strong class="command">named-checkzone</strong></span>).
3748                   The default is <span><strong class="command">yes</strong></span>.
3749                 </p>
3750 <p>
3751                   The use of the SPF record for publishing Sender
3752                   Policy Framework is deprecated as the migration
3753                   from using TXT records to SPF records was abandoned.
3754                   Enabling this option also checks that a TXT Sender
3755                   Policy Framework record exists (starts with "v=spf1")
3756                   if there is an SPF record. Warnings are emitted if the
3757                   TXT record does not exist and can be suppressed with
3758                   <span><strong class="command">check-spf</strong></span>.
3759                 </p>
3760 </dd>
3761 <dt><span class="term"><span><strong class="command">check-mx-cname</strong></span></span></dt>
3762 <dd><p>
3763                   If <span><strong class="command">check-integrity</strong></span> is set then
3764                   fail, warn or ignore MX records that refer
3765                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
3766                 </p></dd>
3767 <dt><span class="term"><span><strong class="command">check-srv-cname</strong></span></span></dt>
3768 <dd><p>
3769                   If <span><strong class="command">check-integrity</strong></span> is set then
3770                   fail, warn or ignore SRV records that refer
3771                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
3772                 </p></dd>
3773 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
3774 <dd><p>
3775                   When performing integrity checks, also check that
3776                   sibling glue exists.  The default is <span><strong class="command">yes</strong></span>.
3777                 </p></dd>
3778 <dt><span class="term"><span><strong class="command">check-spf</strong></span></span></dt>
3779 <dd><p>
3780                   If <span><strong class="command">check-integrity</strong></span> is set then
3781                   check that there is a TXT Sender Policy Framework
3782                   record present (starts with "v=spf1") if there is an
3783                   SPF record present. The default is
3784                   <span><strong class="command">warn</strong></span>.
3785                 </p></dd>
3786 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
3787 <dd><p>
3788                   When returning authoritative negative responses to
3789                   SOA queries set the TTL of the SOA record returned in
3790                   the authority section to zero.
3791                   The default is <span><strong class="command">yes</strong></span>.
3792                 </p></dd>
3793 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl-cache</strong></span></span></dt>
3794 <dd><p>
3795                   When caching a negative response to a SOA query
3796                   set the TTL to zero.
3797                   The default is <span><strong class="command">no</strong></span>.
3798                 </p></dd>
3799 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
3800 <dd>
3801 <p>
3802                   When set to the default value of <code class="literal">yes</code>,
3803                   check the KSK bit in each key to determine how the key
3804                   should be used when generating RRSIGs for a secure zone.
3805                 </p>
3806 <p>
3807                   Ordinarily, zone-signing keys (that is, keys without the
3808                   KSK bit set) are used to sign the entire zone, while
3809                   key-signing keys (keys with the KSK bit set) are only
3810                   used to sign the DNSKEY RRset at the zone apex.
3811                   However, if this option is set to <code class="literal">no</code>,
3812                   then the KSK bit is ignored; KSKs are treated as if they
3813                   were ZSKs and are used to sign the entire zone.  This is
3814                   similar to the <span><strong class="command">dnssec-signzone -z</strong></span>
3815                   command line option.
3816                 </p>
3817 <p>
3818                   When this option is set to <code class="literal">yes</code>, there
3819                   must be at least two active keys for every algorithm
3820                   represented in the DNSKEY RRset: at least one KSK and one
3821                   ZSK per algorithm.  If there is any algorithm for which
3822                   this requirement is not met, this option will be ignored
3823                   for that algorithm.
3824                 </p>
3825 </dd>
3826 <dt><span class="term"><span><strong class="command">dnssec-dnskey-kskonly</strong></span></span></dt>
3827 <dd>
3828 <p>
3829                   When this option and <span><strong class="command">update-check-ksk</strong></span>
3830                   are both set to <code class="literal">yes</code>, only key-signing
3831                   keys (that is, keys with the KSK bit set) will be used
3832                   to sign the DNSKEY RRset at the zone apex.  Zone-signing
3833                   keys (keys without the KSK bit set) will be used to sign
3834                   the remainder of the zone, but not the DNSKEY RRset.
3835                   This is similar to the
3836                   <span><strong class="command">dnssec-signzone -x</strong></span> command line option.
3837                 </p>
3838 <p>
3839                   The default is <span><strong class="command">no</strong></span>.  If
3840                   <span><strong class="command">update-check-ksk</strong></span> is set to
3841                   <code class="literal">no</code>, this option is ignored.
3842                 </p>
3843 </dd>
3844 <dt><span class="term"><span><strong class="command">dnssec-loadkeys-interval</strong></span></span></dt>
3845 <dd><p>
3846                   When a zone is configured with <span><strong class="command">auto-dnssec
3847                   maintain;</strong></span> its key repository must be checked
3848                   periodically to see if any new keys have been added
3849                   or any existing keys' timing metadata has been updated
3850                   (see <a href="man.dnssec-keygen.html" title="dnssec-keygen"><span class="refentrytitle"><span class="application">dnssec-keygen</span></span>(8)</a> and
3851                   <a href="man.dnssec-settime.html" title="dnssec-settime"><span class="refentrytitle"><span class="application">dnssec-settime</span></span>(8)</a>).  The
3852                   <span><strong class="command">dnssec-loadkeys-interval</strong></span> option
3853                   sets the frequency of automatic repository checks, in
3854                   minutes.  The default is <code class="literal">60</code> (1 hour),
3855                   the minimum is <code class="literal">1</code> (1 minute), and the
3856                   maximum is <code class="literal">1440</code> (24 hours); any higher
3857                   value is silently reduced.
3858                 </p></dd>
3859 <dt><span class="term"><span><strong class="command">try-tcp-refresh</strong></span></span></dt>
3860 <dd><p>
3861                   Try to refresh the zone using TCP if UDP queries fail.
3862                   For BIND 8 compatibility, the default is
3863                   <span><strong class="command">yes</strong></span>.
3864                 </p></dd>
3865 <dt><span class="term"><span><strong class="command">dnssec-secure-to-insecure</strong></span></span></dt>
3866 <dd>
3867 <p>
3868                   Allow a dynamic zone to transition from secure to
3869                   insecure (i.e., signed to unsigned) by deleting all
3870                   of the DNSKEY records.  The default is <span><strong class="command">no</strong></span>.
3871                   If set to <span><strong class="command">yes</strong></span>, and if the DNSKEY RRset
3872                   at the zone apex is deleted, all RRSIG and NSEC records
3873                   will be removed from the zone as well.
3874                 </p>
3875 <p>
3876                   If the zone uses NSEC3, then it is also necessary to
3877                   delete the NSEC3PARAM RRset from the zone apex; this will
3878                   cause the removal of all corresponding NSEC3 records.
3879                   (It is expected that this requirement will be eliminated
3880                   in a future release.)
3881                 </p>
3882 <p>
3883                   Note that if a zone has been configured with
3884                   <span><strong class="command">auto-dnssec maintain</strong></span> and the
3885                   private keys remain accessible in the key repository,
3886                   then the zone will be automatically signed again the
3887                   next time <span><strong class="command">named</strong></span> is started.
3888                 </p>
3889 </dd>
3890 </dl></div>
3891 </div>
3892 <div class="sect3" lang="en">
3893 <div class="titlepage"><div><div><h4 class="title">
3894 <a name="id2583480"></a>Forwarding</h4></div></div></div>
3895 <p>
3896             The forwarding facility can be used to create a large site-wide
3897             cache on a few servers, reducing traffic over links to external
3898             name servers. It can also be used to allow queries by servers that
3899             do not have direct access to the Internet, but wish to look up
3900             exterior
3901             names anyway. Forwarding occurs only on those queries for which
3902             the server is not authoritative and does not have the answer in
3903             its cache.
3904           </p>
3905 <div class="variablelist"><dl>
3906 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
3907 <dd><p>
3908                   This option is only meaningful if the
3909                   forwarders list is not empty. A value of <code class="varname">first</code>,
3910                   the default, causes the server to query the forwarders
3911                   first &#8212; and
3912                   if that doesn't answer the question, the server will then
3913                   look for
3914                   the answer itself. If <code class="varname">only</code> is
3915                   specified, the
3916                   server will only query the forwarders.
3917                 </p></dd>
3918 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
3919 <dd><p>
3920                   Specifies the IP addresses to be used
3921                   for forwarding. The default is the empty list (no
3922                   forwarding).
3923                 </p></dd>
3924 </dl></div>
3925 <p>
3926             Forwarding can also be configured on a per-domain basis, allowing
3927             for the global forwarding options to be overridden in a variety
3928             of ways. You can set particular domains to use different
3929             forwarders,
3930             or have a different <span><strong class="command">forward only/first</strong></span> behavior,
3931             or not forward at all, see <a href="Bv9ARM.ch06.html#zone_statement_grammar" title="zone
3932             Statement Grammar">the section called &#8220;<span><strong class="command">zone</strong></span>
3933             Statement Grammar&#8221;</a>.
3934           </p>
3935 </div>
3936 <div class="sect3" lang="en">
3937 <div class="titlepage"><div><div><h4 class="title">
3938 <a name="id2583607"></a>Dual-stack Servers</h4></div></div></div>
3939 <p>
3940             Dual-stack servers are used as servers of last resort to work
3941             around
3942             problems in reachability due the lack of support for either IPv4
3943             or IPv6
3944             on the host machine.
3945           </p>
3946 <div class="variablelist"><dl>
3947 <dt><span class="term"><span><strong class="command">dual-stack-servers</strong></span></span></dt>
3948 <dd><p>
3949                   Specifies host names or addresses of machines with access to
3950                   both IPv4 and IPv6 transports. If a hostname is used, the
3951                   server must be able
3952                   to resolve the name using only the transport it has.  If the
3953                   machine is dual
3954                   stacked, then the <span><strong class="command">dual-stack-servers</strong></span> have no effect unless
3955                   access to a transport has been disabled on the command line
3956                   (e.g. <span><strong class="command">named -4</strong></span>).
3957                 </p></dd>
3958 </dl></div>
3959 </div>
3960 <div class="sect3" lang="en">
3961 <div class="titlepage"><div><div><h4 class="title">
3962 <a name="access_control"></a>Access Control</h4></div></div></div>
3963 <p>
3964             Access to the server can be restricted based on the IP address
3965             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
3966             details on how to specify IP address lists.
3967           </p>
3968 <div class="variablelist"><dl>
3969 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
3970 <dd><p>
3971                   Specifies which hosts are allowed to
3972                   notify this server, a slave, of zone changes in addition
3973                   to the zone masters.
3974                   <span><strong class="command">allow-notify</strong></span> may also be
3975                   specified in the
3976                   <span><strong class="command">zone</strong></span> statement, in which case
3977                   it overrides the
3978                   <span><strong class="command">options allow-notify</strong></span>
3979                   statement.  It is only meaningful
3980                   for a slave zone.  If not specified, the default is to
3981                   process notify messages
3982                   only from a zone's master.
3983                 </p></dd>
3984 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
3985 <dd>
3986 <p>
3987                   Specifies which hosts are allowed to ask ordinary
3988                   DNS questions. <span><strong class="command">allow-query</strong></span> may
3989                   also be specified in the <span><strong class="command">zone</strong></span>
3990                   statement, in which case it overrides the
3991                   <span><strong class="command">options allow-query</strong></span> statement.
3992                   If not specified, the default is to allow queries
3993                   from all hosts.
3994                 </p>
3995 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3996 <h3 class="title">Note</h3>
3997 <p>
3998                     <span><strong class="command">allow-query-cache</strong></span> is now
3999                     used to specify access to the cache.
4000                   </p>
4001 </div>
4002 </dd>
4003 <dt><span class="term"><span><strong class="command">allow-query-on</strong></span></span></dt>
4004 <dd>
4005 <p>
4006                   Specifies which local addresses can accept ordinary
4007                   DNS questions. This makes it possible, for instance,
4008                   to allow queries on internal-facing interfaces but
4009                   disallow them on external-facing ones, without
4010                   necessarily knowing the internal network's addresses.
4011                 </p>
4012 <p>
4013                   Note that <span><strong class="command">allow-query-on</strong></span> is only
4014                   checked for queries that are permitted by
4015                   <span><strong class="command">allow-query</strong></span>.  A query must be
4016                   allowed by both ACLs, or it will be refused.
4017                 </p>
4018 <p>
4019                   <span><strong class="command">allow-query-on</strong></span> may
4020                   also be specified in the <span><strong class="command">zone</strong></span>
4021                   statement, in which case it overrides the
4022                   <span><strong class="command">options allow-query-on</strong></span> statement.
4023                 </p>
4024 <p>
4025                   If not specified, the default is to allow queries
4026                   on all addresses.
4027                 </p>
4028 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4029 <h3 class="title">Note</h3>
4030 <p>
4031                     <span><strong class="command">allow-query-cache</strong></span> is
4032                     used to specify access to the cache.
4033                   </p>
4034 </div>
4035 </dd>
4036 <dt><span class="term"><span><strong class="command">allow-query-cache</strong></span></span></dt>
4037 <dd><p>
4038                   Specifies which hosts are allowed to get answers
4039                   from the cache.  If <span><strong class="command">allow-query-cache</strong></span>
4040                   is not set then <span><strong class="command">allow-recursion</strong></span>
4041                   is used if set, otherwise <span><strong class="command">allow-query</strong></span>
4042                   is used if set unless <span><strong class="command">recursion no;</strong></span> is
4043                   set in which case <span><strong class="command">none;</strong></span> is used,
4044                   otherwise the default (<span><strong class="command">localnets;</strong></span>
4045                   <span><strong class="command">localhost;</strong></span>) is used.
4046                 </p></dd>
4047 <dt><span class="term"><span><strong class="command">allow-query-cache-on</strong></span></span></dt>
4048 <dd><p>
4049                   Specifies which local addresses can give answers
4050                   from the cache.  If not specified, the default is
4051                   to allow cache queries on any address,
4052                   <span><strong class="command">localnets</strong></span> and
4053                   <span><strong class="command">localhost</strong></span>.
4054                 </p></dd>
4055 <dt><span class="term"><span><strong class="command">allow-recursion</strong></span></span></dt>
4056 <dd><p>
4057                   Specifies which hosts are allowed to make recursive
4058                   queries through this server. If
4059                   <span><strong class="command">allow-recursion</strong></span> is not set
4060                   then <span><strong class="command">allow-query-cache</strong></span> is
4061                   used if set, otherwise <span><strong class="command">allow-query</strong></span>
4062                   is used if set, otherwise the default
4063                   (<span><strong class="command">localnets;</strong></span>
4064                   <span><strong class="command">localhost;</strong></span>) is used.
4065                 </p></dd>
4066 <dt><span class="term"><span><strong class="command">allow-recursion-on</strong></span></span></dt>
4067 <dd><p>
4068                   Specifies which local addresses can accept recursive
4069                   queries.  If not specified, the default is to allow
4070                   recursive queries on all addresses.
4071                 </p></dd>
4072 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
4073 <dd><p>
4074                   Specifies which hosts are allowed to
4075                   submit Dynamic DNS updates for master zones. The default is
4076                   to deny
4077                   updates from all hosts.  Note that allowing updates based
4078                   on the requestor's IP address is insecure; see
4079                   <a href="Bv9ARM.ch07.html#dynamic_update_security" title="Dynamic Update Security">the section called &#8220;Dynamic Update Security&#8221;</a> for details.
4080                 </p></dd>
4081 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
4082 <dd>
4083 <p>
4084                   Specifies which hosts are allowed to
4085                   submit Dynamic DNS updates to slave zones to be forwarded to
4086                   the
4087                   master.  The default is <strong class="userinput"><code>{ none; }</code></strong>,
4088                   which
4089                   means that no update forwarding will be performed.  To
4090                   enable
4091                   update forwarding, specify
4092                   <strong class="userinput"><code>allow-update-forwarding { any; };</code></strong>.
4093                   Specifying values other than <strong class="userinput"><code>{ none; }</code></strong> or
4094                   <strong class="userinput"><code>{ any; }</code></strong> is usually
4095                   counterproductive, since
4096                   the responsibility for update access control should rest
4097                   with the
4098                   master server, not the slaves.
4099                 </p>
4100 <p>
4101                   Note that enabling the update forwarding feature on a slave
4102                   server
4103                   may expose master servers relying on insecure IP address
4104                   based
4105                   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>
4106                   for more details.
4107                 </p>
4108 </dd>
4109 <dt><span class="term"><span><strong class="command">allow-v6-synthesis</strong></span></span></dt>
4110 <dd><p>
4111                   This option was introduced for the smooth transition from
4112                   AAAA
4113                   to A6 and from "nibble labels" to binary labels.
4114                   However, since both A6 and binary labels were then
4115                   deprecated,
4116                   this option was also deprecated.
4117                   It is now ignored with some warning messages.
4118                 </p></dd>
4119 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
4120 <dd><p>
4121                   Specifies which hosts are allowed to
4122                   receive zone transfers from the server. <span><strong class="command">allow-transfer</strong></span> may
4123                   also be specified in the <span><strong class="command">zone</strong></span>
4124                   statement, in which
4125                   case it overrides the <span><strong class="command">options allow-transfer</strong></span> statement.
4126                   If not specified, the default is to allow transfers to all
4127                   hosts.
4128                 </p></dd>
4129 <dt><span class="term"><span><strong class="command">blackhole</strong></span></span></dt>
4130 <dd><p>
4131                   Specifies a list of addresses that the
4132                   server will not accept queries from or use to resolve a
4133                   query. Queries
4134                   from these addresses will not be responded to. The default
4135                   is <strong class="userinput"><code>none</code></strong>.
4136                 </p></dd>
4137 <dt><span class="term"><span><strong class="command">filter-aaaa</strong></span></span></dt>
4138 <dd><p>
4139                   Specifies a list of addresses to which
4140                   <span><strong class="command">filter-aaaa-on-v4</strong></span>
4141                   is applies.  The default is <strong class="userinput"><code>any</code></strong>.
4142                 </p></dd>
4143 <dt><span class="term"><span><strong class="command">no-case-compress</strong></span></span></dt>
4144 <dd>
4145 <p>
4146                   Specifies a list of addresses which require responses
4147                   to use case-insensitive compression.  This ACL can be
4148                   used when <span><strong class="command">named</strong></span> needs to work with
4149                   clients that do not comply with the requirement in RFC
4150                   1034 to use case-insensitive name comparisons when
4151                   checking for matching domain names.
4152                 </p>
4153 <p>
4154                   If left undefined, the ACL defaults to
4155                   <span><strong class="command">none</strong></span>: case-insensitive compression
4156                   will be used for all clients.  If the ACL is defined and
4157                   matches a client, then case will be ignored when
4158                   compressing domain names in DNS responses sent to that
4159                   client.
4160                 </p>
4161 <p>
4162                   This can result in slightly smaller responses: if
4163                   a response contains the names "example.com" and
4164                   "example.COM", case-insensitive compression would treat
4165                   the second one as a duplicate.  It also ensures
4166                   that the case of the query name exactly matches the
4167                   case of the owner names of returned records, rather
4168                   than matching the case of the records entered in
4169                   the zone file.  This allows responses to exactly
4170                   match the query, which is required by some clients
4171                   due to incorrect use of case-sensitive comparisons.
4172                 </p>
4173 <p>
4174                   Case-insensitive compression is <span class="emphasis"><em>always</em></span>
4175                   used in AXFR and IXFR responses, regardless of whether
4176                   the client matches this ACL.
4177                 </p>
4178 <p>
4179                   There are circumstances in which <span><strong class="command">named</strong></span>
4180                   will not preserve the case of owner names of records:
4181                   if a zone file defines records of different types with
4182                   the same name, but the capitalization of the name is
4183                   different (e.g., "www.example.com/A" and
4184                   "WWW.EXAMPLE.COM/AAAA"), then all responses for that
4185                   name will use the <span class="emphasis"><em>first</em></span> version
4186                   of the name that was used in the zone file.  This
4187                   limitation may be addressed in a future release.  However,
4188                   domain names specified in the rdata of resource records
4189                   (i.e., records of type NS, MX, CNAME, etc) will always
4190                   have their case preserved unless the client matches this
4191                   ACL.
4192                 </p>
4193 </dd>
4194 <dt><span class="term"><span><strong class="command">resolver-query-timeout</strong></span></span></dt>
4195 <dd><p>
4196                   The amount of time the resolver will spend attempting
4197                   to resolve a recursive query before failing.  The default
4198                   and minimum is <code class="literal">10</code> and the maximum is
4199                   <code class="literal">30</code>.  Setting it to <code class="literal">0</code>
4200                   will result in the default being used.
4201                 </p></dd>
4202 </dl></div>
4203 </div>
4204 <div class="sect3" lang="en">
4205 <div class="titlepage"><div><div><h4 class="title">
4206 <a name="id2584281"></a>Interfaces</h4></div></div></div>
4207 <p>
4208             The interfaces and ports that the server will answer queries
4209             from may be specified using the <span><strong class="command">listen-on</strong></span> option. <span><strong class="command">listen-on</strong></span> takes
4210             an optional port and an <code class="varname">address_match_list</code>
4211             of IPv4 addresses.  (IPv6 addresses are ignored, with a
4212             logged warning.)
4213             The server will listen on all interfaces allowed by the address
4214             match list. If a port is not specified, port 53 will be used.
4215           </p>
4216 <p>
4217             Multiple <span><strong class="command">listen-on</strong></span> statements are
4218             allowed.
4219             For example,
4220           </p>
4221 <pre class="programlisting">listen-on { 5.6.7.8; };
4222 listen-on port 1234 { !1.2.3.4; 1.2/16; };
4223 </pre>
4224 <p>
4225             will enable the name server on port 53 for the IP address
4226             5.6.7.8, and on port 1234 of an address on the machine in net
4227             1.2 that is not 1.2.3.4.
4228           </p>
4229 <p>
4230             If no <span><strong class="command">listen-on</strong></span> is specified, the
4231             server will listen on port 53 on all IPv4 interfaces.
4232           </p>
4233 <p>
4234             The <span><strong class="command">listen-on-v6</strong></span> option is used to
4235             specify the interfaces and the ports on which the server will
4236             listen
4237             for incoming queries sent using IPv6.
4238           </p>
4239 <p>
4240             When </p>
4241 <pre class="programlisting">{ any; }</pre>
4242 <p> is
4243             specified
4244             as the <code class="varname">address_match_list</code> for the
4245             <span><strong class="command">listen-on-v6</strong></span> option,
4246             the server does not bind a separate socket to each IPv6 interface
4247             address as it does for IPv4 if the operating system has enough API
4248             support for IPv6 (specifically if it conforms to RFC 3493 and RFC
4249             3542).
4250             Instead, it listens on the IPv6 wildcard address.
4251             If the system only has incomplete API support for IPv6, however,
4252             the behavior is the same as that for IPv4.
4253           </p>
4254 <p>
4255             A list of particular IPv6 addresses can also be specified, in
4256             which case
4257             the server listens on a separate socket for each specified
4258             address,
4259             regardless of whether the desired API is supported by the system.
4260             IPv4 addresses specified in <span><strong class="command">listen-on-v6</strong></span>
4261             will be ignored, with a logged warning.
4262           </p>
4263 <p>
4264             Multiple <span><strong class="command">listen-on-v6</strong></span> options can
4265             be used.
4266             For example,
4267           </p>
4268 <pre class="programlisting">listen-on-v6 { any; };
4269 listen-on-v6 port 1234 { !2001:db8::/32; any; };
4270 </pre>
4271 <p>
4272             will enable the name server on port 53 for any IPv6 addresses
4273             (with a single wildcard socket),
4274             and on port 1234 of IPv6 addresses that is not in the prefix
4275             2001:db8::/32 (with separate sockets for each matched address.)
4276           </p>
4277 <p>
4278             To make the server not listen on any IPv6 address, use
4279           </p>
4280 <pre class="programlisting">listen-on-v6 { none; };
4281 </pre>
4282 <p>
4283             If no <span><strong class="command">listen-on-v6</strong></span> option is
4284             specified, the server will not listen on any IPv6 address
4285             unless <span><strong class="command">-6</strong></span> is specified when <span><strong class="command">named</strong></span> is
4286             invoked.  If <span><strong class="command">-6</strong></span> is specified then
4287             <span><strong class="command">named</strong></span> will listen on port 53 on all IPv6 interfaces by default.
4288           </p>
4289 </div>
4290 <div class="sect3" lang="en">
4291 <div class="titlepage"><div><div><h4 class="title">
4292 <a name="query_address"></a>Query Address</h4></div></div></div>
4293 <p>
4294             If the server doesn't know the answer to a question, it will
4295             query other name servers. <span><strong class="command">query-source</strong></span> specifies
4296             the address and port used for such queries. For queries sent over
4297             IPv6, there is a separate <span><strong class="command">query-source-v6</strong></span> option.
4298             If <span><strong class="command">address</strong></span> is <span><strong class="command">*</strong></span> (asterisk) or is omitted,
4299             a wildcard IP address (<span><strong class="command">INADDR_ANY</strong></span>)
4300             will be used.
4301           </p>
4302 <p>
4303             If <span><strong class="command">port</strong></span> is <span><strong class="command">*</strong></span> or is omitted,
4304             a random port number from a pre-configured
4305             range is picked up and will be used for each query.
4306             The port range(s) is that specified in
4307             the <span><strong class="command">use-v4-udp-ports</strong></span> (for IPv4)
4308             and <span><strong class="command">use-v6-udp-ports</strong></span> (for IPv6)
4309             options, excluding the ranges specified in
4310             the <span><strong class="command">avoid-v4-udp-ports</strong></span>
4311             and <span><strong class="command">avoid-v6-udp-ports</strong></span> options, respectively.
4312           </p>
4313 <p>
4314             The defaults of the <span><strong class="command">query-source</strong></span> and
4315             <span><strong class="command">query-source-v6</strong></span> options
4316             are:
4317           </p>
4318 <pre class="programlisting">query-source address * port *;
4319 query-source-v6 address * port *;
4320 </pre>
4321 <p>
4322             If <span><strong class="command">use-v4-udp-ports</strong></span> or
4323             <span><strong class="command">use-v6-udp-ports</strong></span> is unspecified,
4324             <span><strong class="command">named</strong></span> will check if the operating
4325             system provides a programming interface to retrieve the
4326             system's default range for ephemeral ports.
4327             If such an interface is available,
4328             <span><strong class="command">named</strong></span> will use the corresponding system
4329             default range; otherwise, it will use its own defaults:
4330          </p>
4331 <pre class="programlisting">use-v4-udp-ports { range 1024 65535; };
4332 use-v6-udp-ports { range 1024 65535; };
4333 </pre>
4334 <p>
4335             Note: make sure the ranges be sufficiently large for
4336             security.  A desirable size depends on various parameters,
4337             but we generally recommend it contain at least 16384 ports
4338             (14 bits of entropy).
4339             Note also that the system's default range when used may be
4340             too small for this purpose, and that the range may even be
4341             changed while <span><strong class="command">named</strong></span> is running; the new
4342             range will automatically be applied when <span><strong class="command">named</strong></span>
4343             is reloaded.
4344             It is encouraged to
4345             configure <span><strong class="command">use-v4-udp-ports</strong></span> and
4346             <span><strong class="command">use-v6-udp-ports</strong></span> explicitly so that the
4347             ranges are sufficiently large and are reasonably
4348             independent from the ranges used by other applications.
4349           </p>
4350 <p>
4351             Note: the operational configuration
4352             where <span><strong class="command">named</strong></span> runs may prohibit the use
4353             of some ports.  For example, UNIX systems will not allow
4354             <span><strong class="command">named</strong></span> running without a root privilege
4355             to use ports less than 1024.
4356             If such ports are included in the specified (or detected)
4357             set of query ports, the corresponding query attempts will
4358             fail, resulting in resolution failures or delay.
4359             It is therefore important to configure the set of ports
4360             that can be safely used in the expected operational environment.
4361           </p>
4362 <p>
4363             The defaults of the <span><strong class="command">avoid-v4-udp-ports</strong></span> and
4364             <span><strong class="command">avoid-v6-udp-ports</strong></span> options
4365             are:
4366           </p>
4367 <pre class="programlisting">avoid-v4-udp-ports {};
4368 avoid-v6-udp-ports {};
4369 </pre>
4370 <p>
4371             Note: BIND 9.5.0 introduced
4372             the <span><strong class="command">use-queryport-pool</strong></span>
4373             option to support a pool of such random ports, but this
4374             option is now obsolete because reusing the same ports in
4375             the pool may not be sufficiently secure.
4376             For the same reason, it is generally strongly discouraged to
4377             specify a particular port for the
4378             <span><strong class="command">query-source</strong></span> or
4379             <span><strong class="command">query-source-v6</strong></span> options;
4380             it implicitly disables the use of randomized port numbers.
4381           </p>
4382 <div class="variablelist"><dl>
4383 <dt><span class="term"><span><strong class="command">use-queryport-pool</strong></span></span></dt>
4384 <dd><p>
4385                   This option is obsolete.
4386                 </p></dd>
4387 <dt><span class="term"><span><strong class="command">queryport-pool-ports</strong></span></span></dt>
4388 <dd><p>
4389                   This option is obsolete.
4390                 </p></dd>
4391 <dt><span class="term"><span><strong class="command">queryport-pool-updateinterval</strong></span></span></dt>
4392 <dd><p>
4393                   This option is obsolete.
4394                 </p></dd>
4395 </dl></div>
4396 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4397 <h3 class="title">Note</h3>
4398 <p>
4399               The address specified in the <span><strong class="command">query-source</strong></span> option
4400               is used for both UDP and TCP queries, but the port applies only
4401               to UDP queries.  TCP queries always use a random
4402               unprivileged port.
4403             </p>
4404 </div>
4405 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4406 <h3 class="title">Note</h3>
4407 <p>
4408               Solaris 2.5.1 and earlier does not support setting the source
4409               address for TCP sockets.
4410             </p>
4411 </div>
4412 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4413 <h3 class="title">Note</h3>
4414 <p>
4415               See also <span><strong class="command">transfer-source</strong></span> and
4416               <span><strong class="command">notify-source</strong></span>.
4417             </p>
4418 </div>
4419 </div>
4420 <div class="sect3" lang="en">
4421 <div class="titlepage"><div><div><h4 class="title">
4422 <a name="zone_transfers"></a>Zone Transfers</h4></div></div></div>
4423 <p>
4424             <acronym class="acronym">BIND</acronym> has mechanisms in place to
4425             facilitate zone transfers
4426             and set limits on the amount of load that transfers place on the
4427             system. The following options apply to zone transfers.
4428           </p>
4429 <div class="variablelist"><dl>
4430 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
4431 <dd>
4432 <p>
4433                   Defines a global list of IP addresses of name servers
4434                   that are also sent NOTIFY messages whenever a fresh copy of
4435                   the
4436                   zone is loaded, in addition to the servers listed in the
4437                   zone's NS records.
4438                   This helps to ensure that copies of the zones will
4439                   quickly converge on stealth servers.
4440                   Optionally, a port may be specified with each
4441                   <span><strong class="command">also-notify</strong></span> address to send
4442                   the notify messages to a port other than the
4443                   default of 53.
4444                   An optional TSIG key can also be specified with each
4445                   address to cause the notify messages to be signed; this
4446                   can be useful when sending notifies to multiple views.
4447                   In place of explicit addresses, one or more named
4448                   <span><strong class="command">masters</strong></span> lists can be used.
4449                 </p>
4450 <p>
4451                   If an <span><strong class="command">also-notify</strong></span> list
4452                   is given in a <span><strong class="command">zone</strong></span> statement,
4453                   it will override
4454                   the <span><strong class="command">options also-notify</strong></span>
4455                   statement. When a <span><strong class="command">zone notify</strong></span>
4456                   statement
4457                   is set to <span><strong class="command">no</strong></span>, the IP
4458                   addresses in the global <span><strong class="command">also-notify</strong></span> list will
4459                   not be sent NOTIFY messages for that zone. The default is
4460                   the empty
4461                   list (no global notification list).
4462                 </p>
4463 </dd>
4464 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
4465 <dd><p>
4466                   Inbound zone transfers running longer than
4467                   this many minutes will be terminated. The default is 120
4468                   minutes
4469                   (2 hours).  The maximum value is 28 days (40320 minutes).
4470                 </p></dd>
4471 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
4472 <dd><p>
4473                   Inbound zone transfers making no progress
4474                   in this many minutes will be terminated. The default is 60
4475                   minutes
4476                   (1 hour).  The maximum value is 28 days (40320 minutes).
4477                 </p></dd>
4478 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
4479 <dd><p>
4480                   Outbound zone transfers running longer than
4481                   this many minutes will be terminated. The default is 120
4482                   minutes
4483                   (2 hours).  The maximum value is 28 days (40320 minutes).
4484                 </p></dd>
4485 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
4486 <dd><p>
4487                   Outbound zone transfers making no progress
4488                   in this many minutes will be terminated.  The default is 60
4489                   minutes (1
4490                   hour).  The maximum value is 28 days (40320 minutes).
4491                 </p></dd>
4492 <dt><span class="term"><span><strong class="command">serial-query-rate</strong></span></span></dt>
4493 <dd>
4494 <p>
4495                   Slave servers will periodically query master
4496                   servers to find out if zone serial numbers have
4497                   changed. Each such query uses a minute amount of
4498                   the slave server's network bandwidth.  To limit
4499                   the amount of bandwidth used, BIND 9 limits the
4500                   rate at which queries are sent.  The value of the
4501                   <span><strong class="command">serial-query-rate</strong></span> option, an
4502                   integer, is the maximum number of queries sent
4503                   per second.  The default is 20 per second.
4504                   The lowest possible rate is one per second; when set
4505                   to zero, it will be silently raised to one.
4506                 </p>
4507 <p>
4508                   In addition to controlling the rate SOA refresh
4509                   queries are issued at,
4510                   <span><strong class="command">serial-query-rate</strong></span> also controls
4511                   the rate at which NOTIFY messages are sent from
4512                   both master and slave zones.
4513                 </p>
4514 </dd>
4515 <dt><span class="term"><span><strong class="command">serial-queries</strong></span></span></dt>
4516 <dd><p>
4517                   In BIND 8, the <span><strong class="command">serial-queries</strong></span>
4518                   option
4519                   set the maximum number of concurrent serial number queries
4520                   allowed to be outstanding at any given time.
4521                   BIND 9 does not limit the number of outstanding
4522                   serial queries and ignores the <span><strong class="command">serial-queries</strong></span> option.
4523                   Instead, it limits the rate at which the queries are sent
4524                   as defined using the <span><strong class="command">serial-query-rate</strong></span> option.
4525                 </p></dd>
4526 <dt><span class="term"><span><strong class="command">transfer-format</strong></span></span></dt>
4527 <dd><p>
4528                   Zone transfers can be sent using two different formats,
4529                   <span><strong class="command">one-answer</strong></span> and
4530                   <span><strong class="command">many-answers</strong></span>.
4531                   The <span><strong class="command">transfer-format</strong></span> option is used
4532                   on the master server to determine which format it sends.
4533                   <span><strong class="command">one-answer</strong></span> uses one DNS message per
4534                   resource record transferred.
4535                   <span><strong class="command">many-answers</strong></span> packs as many resource
4536                   records as possible into a message.
4537                   <span><strong class="command">many-answers</strong></span> is more efficient, but is
4538                   only supported by relatively new slave servers,
4539                   such as <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
4540                   8.x and <acronym class="acronym">BIND</acronym> 4.9.5 onwards.
4541                   The <span><strong class="command">many-answers</strong></span> format is also supported by
4542                   recent Microsoft Windows nameservers.
4543                   The default is <span><strong class="command">many-answers</strong></span>.
4544                   <span><strong class="command">transfer-format</strong></span> may be overridden on a
4545                   per-server basis by using the <span><strong class="command">server</strong></span>
4546                   statement.
4547                 </p></dd>
4548 <dt><span class="term"><span><strong class="command">transfers-in</strong></span></span></dt>
4549 <dd><p>
4550                   The maximum number of inbound zone transfers
4551                   that can be running concurrently. The default value is <code class="literal">10</code>.
4552                   Increasing <span><strong class="command">transfers-in</strong></span> may
4553                   speed up the convergence
4554                   of slave zones, but it also may increase the load on the
4555                   local system.
4556                 </p></dd>
4557 <dt><span class="term"><span><strong class="command">transfers-out</strong></span></span></dt>
4558 <dd><p>
4559                   The maximum number of outbound zone transfers
4560                   that can be running concurrently. Zone transfer requests in
4561                   excess
4562                   of the limit will be refused. The default value is <code class="literal">10</code>.
4563                 </p></dd>
4564 <dt><span class="term"><span><strong class="command">transfers-per-ns</strong></span></span></dt>
4565 <dd><p>
4566                   The maximum number of inbound zone transfers
4567                   that can be concurrently transferring from a given remote
4568                   name server.
4569                   The default value is <code class="literal">2</code>.
4570                   Increasing <span><strong class="command">transfers-per-ns</strong></span>
4571                   may
4572                   speed up the convergence of slave zones, but it also may
4573                   increase
4574                   the load on the remote name server. <span><strong class="command">transfers-per-ns</strong></span> may
4575                   be overridden on a per-server basis by using the <span><strong class="command">transfers</strong></span> phrase
4576                   of the <span><strong class="command">server</strong></span> statement.
4577                 </p></dd>
4578 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
4579 <dd>
4580 <p><span><strong class="command">transfer-source</strong></span>
4581                   determines which local address will be bound to IPv4
4582                   TCP connections used to fetch zones transferred
4583                   inbound by the server.  It also determines the
4584                   source IPv4 address, and optionally the UDP port,
4585                   used for the refresh queries and forwarded dynamic
4586                   updates.  If not set, it defaults to a system
4587                   controlled value which will usually be the address
4588                   of the interface "closest to" the remote end. This
4589                   address must appear in the remote end's
4590                   <span><strong class="command">allow-transfer</strong></span> option for the
4591                   zone being transferred, if one is specified. This
4592                   statement sets the
4593                   <span><strong class="command">transfer-source</strong></span> for all zones,
4594                   but can be overridden on a per-view or per-zone
4595                   basis by including a
4596                   <span><strong class="command">transfer-source</strong></span> statement within
4597                   the <span><strong class="command">view</strong></span> or
4598                   <span><strong class="command">zone</strong></span> block in the configuration
4599                   file.
4600                 </p>
4601 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4602 <h3 class="title">Note</h3>
4603 <p>
4604                     Solaris 2.5.1 and earlier does not support setting the
4605                     source address for TCP sockets.
4606                   </p>
4607 </div>
4608 </dd>
4609 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
4610 <dd><p>
4611                   The same as <span><strong class="command">transfer-source</strong></span>,
4612                   except zone transfers are performed using IPv6.
4613                 </p></dd>
4614 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
4615 <dd>
4616 <p>
4617                   An alternate transfer source if the one listed in
4618                   <span><strong class="command">transfer-source</strong></span> fails and
4619                   <span><strong class="command">use-alt-transfer-source</strong></span> is
4620                   set.
4621                 </p>
4622 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4623 <h3 class="title">Note</h3>
4624                   If you do not wish the alternate transfer source
4625                   to be used, you should set
4626                   <span><strong class="command">use-alt-transfer-source</strong></span>
4627                   appropriately and you should not depend upon
4628                   getting an answer back to the first refresh
4629                   query.
4630                 </div>
4631 </dd>
4632 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
4633 <dd><p>
4634                   An alternate transfer source if the one listed in
4635                   <span><strong class="command">transfer-source-v6</strong></span> fails and
4636                   <span><strong class="command">use-alt-transfer-source</strong></span> is
4637                   set.
4638                 </p></dd>
4639 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
4640 <dd><p>
4641                   Use the alternate transfer sources or not.  If views are
4642                   specified this defaults to <span><strong class="command">no</strong></span>
4643                   otherwise it defaults to
4644                   <span><strong class="command">yes</strong></span> (for BIND 8
4645                   compatibility).
4646                 </p></dd>
4647 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
4648 <dd>
4649 <p><span><strong class="command">notify-source</strong></span>
4650                   determines which local source address, and
4651                   optionally UDP port, will be used to send NOTIFY
4652                   messages.  This address must appear in the slave
4653                   server's <span><strong class="command">masters</strong></span> zone clause or
4654                   in an <span><strong class="command">allow-notify</strong></span> clause.  This
4655                   statement sets the <span><strong class="command">notify-source</strong></span>
4656                   for all zones, but can be overridden on a per-zone or
4657                   per-view basis by including a
4658                   <span><strong class="command">notify-source</strong></span> statement within
4659                   the <span><strong class="command">zone</strong></span> or
4660                   <span><strong class="command">view</strong></span> block in the configuration
4661                   file.
4662                 </p>
4663 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4664 <h3 class="title">Note</h3>
4665 <p>
4666                     Solaris 2.5.1 and earlier does not support setting the
4667                     source address for TCP sockets.
4668                   </p>
4669 </div>
4670 </dd>
4671 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
4672 <dd><p>
4673                   Like <span><strong class="command">notify-source</strong></span>,
4674                   but applies to notify messages sent to IPv6 addresses.
4675                 </p></dd>
4676 </dl></div>
4677 </div>
4678 <div class="sect3" lang="en">
4679 <div class="titlepage"><div><div><h4 class="title">
4680 <a name="id2585434"></a>UDP Port Lists</h4></div></div></div>
4681 <p>
4682             <span><strong class="command">use-v4-udp-ports</strong></span>,
4683             <span><strong class="command">avoid-v4-udp-ports</strong></span>,
4684             <span><strong class="command">use-v6-udp-ports</strong></span>, and
4685             <span><strong class="command">avoid-v6-udp-ports</strong></span>
4686             specify a list of IPv4 and IPv6 UDP ports that will be
4687             used or not used as source ports for UDP messages.
4688             See <a href="Bv9ARM.ch06.html#query_address" title="Query Address">the section called &#8220;Query Address&#8221;</a> about how the
4689             available ports are determined.
4690             For example, with the following configuration
4691           </p>
4692 <pre class="programlisting">
4693 use-v6-udp-ports { range 32768 65535; };
4694 avoid-v6-udp-ports { 40000; range 50000 60000; };
4695 </pre>
4696 <p>
4697              UDP ports of IPv6 messages sent
4698              from <span><strong class="command">named</strong></span> will be in one
4699              of the following ranges: 32768 to 39999, 40001 to 49999,
4700              and 60001 to 65535.
4701            </p>
4702 <p>
4703              <span><strong class="command">avoid-v4-udp-ports</strong></span> and
4704              <span><strong class="command">avoid-v6-udp-ports</strong></span> can be used
4705              to prevent <span><strong class="command">named</strong></span> from choosing as its random source port a
4706              port that is blocked by your firewall or a port that is
4707              used by other applications;
4708              if a query went out with a source port blocked by a
4709              firewall, the
4710              answer would not get by the firewall and the name server would
4711              have to query again.
4712              Note: the desired range can also be represented only with
4713              <span><strong class="command">use-v4-udp-ports</strong></span> and
4714              <span><strong class="command">use-v6-udp-ports</strong></span>, and the
4715              <span><strong class="command">avoid-</strong></span> options are redundant in that
4716              sense; they are provided for backward compatibility and
4717              to possibly simplify the port specification.
4718            </p>
4719 </div>
4720 <div class="sect3" lang="en">
4721 <div class="titlepage"><div><div><h4 class="title">
4722 <a name="id2585562"></a>Operating System Resource Limits</h4></div></div></div>
4723 <p>
4724             The server's usage of many system resources can be limited.
4725             Scaled values are allowed when specifying resource limits.  For
4726             example, <span><strong class="command">1G</strong></span> can be used instead of
4727             <span><strong class="command">1073741824</strong></span> to specify a limit of
4728             one
4729             gigabyte. <span><strong class="command">unlimited</strong></span> requests
4730             unlimited use, or the
4731             maximum available amount. <span><strong class="command">default</strong></span>
4732             uses the limit
4733             that was in force when the server was started. See the description
4734             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>.
4735           </p>
4736 <p>
4737             The following options set operating system resource limits for
4738             the name server process.  Some operating systems don't support
4739             some or
4740             any of the limits. On such systems, a warning will be issued if
4741             the
4742             unsupported limit is used.
4743           </p>
4744 <div class="variablelist"><dl>
4745 <dt><span class="term"><span><strong class="command">coresize</strong></span></span></dt>
4746 <dd><p>
4747                   The maximum size of a core dump. The default
4748                   is <code class="literal">default</code>.
4749                 </p></dd>
4750 <dt><span class="term"><span><strong class="command">datasize</strong></span></span></dt>
4751 <dd><p>
4752                   The maximum amount of data memory the server
4753                   may use. The default is <code class="literal">default</code>.
4754                   This is a hard limit on server memory usage.
4755                   If the server attempts to allocate memory in excess of this
4756                   limit, the allocation will fail, which may in turn leave
4757                   the server unable to perform DNS service.  Therefore,
4758                   this option is rarely useful as a way of limiting the
4759                   amount of memory used by the server, but it can be used
4760                   to raise an operating system data size limit that is
4761                   too small by default.  If you wish to limit the amount
4762                   of memory used by the server, use the
4763                   <span><strong class="command">max-cache-size</strong></span> and
4764                   <span><strong class="command">recursive-clients</strong></span>
4765                   options instead.
4766                 </p></dd>
4767 <dt><span class="term"><span><strong class="command">files</strong></span></span></dt>
4768 <dd><p>
4769                   The maximum number of files the server
4770                   may have open concurrently. The default is <code class="literal">unlimited</code>.
4771                 </p></dd>
4772 <dt><span class="term"><span><strong class="command">stacksize</strong></span></span></dt>
4773 <dd><p>
4774                   The maximum amount of stack memory the server
4775                   may use. The default is <code class="literal">default</code>.
4776                 </p></dd>
4777 </dl></div>
4778 </div>
4779 <div class="sect3" lang="en">
4780 <div class="titlepage"><div><div><h4 class="title">
4781 <a name="server_resource_limits"></a>Server  Resource Limits</h4></div></div></div>
4782 <p>
4783             The following options set limits on the server's
4784             resource consumption that are enforced internally by the
4785             server rather than the operating system.
4786           </p>
4787 <div class="variablelist"><dl>
4788 <dt><span class="term"><span><strong class="command">max-ixfr-log-size</strong></span></span></dt>
4789 <dd><p>
4790                   This option is obsolete; it is accepted
4791                   and ignored for BIND 8 compatibility.  The option
4792                   <span><strong class="command">max-journal-size</strong></span> performs a
4793                   similar function in BIND 9.
4794                 </p></dd>
4795 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
4796 <dd><p>
4797                   Sets a maximum size for each journal file
4798                   (see <a href="Bv9ARM.ch04.html#journal" title="The journal file">the section called &#8220;The journal file&#8221;</a>).  When the journal file
4799                   approaches
4800                   the specified size, some of the oldest transactions in the
4801                   journal
4802                   will be automatically removed.  The largest permitted
4803                   value is 2 gigabytes. The default is
4804                   <code class="literal">unlimited</code>, which also
4805                   means 2 gigabytes.
4806                   This may also be set on a per-zone basis.
4807                 </p></dd>
4808 <dt><span class="term"><span><strong class="command">host-statistics-max</strong></span></span></dt>
4809 <dd><p>
4810                   In BIND 8, specifies the maximum number of host statistics
4811                   entries to be kept.
4812                   Not implemented in BIND 9.
4813                 </p></dd>
4814 <dt><span class="term"><span><strong class="command">recursive-clients</strong></span></span></dt>
4815 <dd>
4816 <p>
4817                   The maximum number ("hard quota") of simultaneous
4818                   recursive lookups the server will perform on behalf
4819                   of clients.  The default is
4820                   <code class="literal">1000</code>.  Because each recursing
4821                   client uses a fair
4822                   bit of memory (on the order of 20 kilobytes), the
4823                   value of the
4824                   <span><strong class="command">recursive-clients</strong></span> option may
4825                   have to be decreased on hosts with limited memory.
4826                 </p>
4827 <p>
4828                   <code class="option">recursive-clients</code> defines a "hard
4829                   quota" limit for pending recursive clients: when more
4830                   clients than this are pending, new incoming requests
4831                   will not be accepted, and for each incoming request
4832                   a previous pending request will also be dropped.
4833                 </p>
4834 <p>
4835                   A "soft quota" is also set.  When this lower
4836                   quota is exceeded, incoming requests are accepted, but
4837                   for each one, a pending request will be dropped.
4838                   If <code class="option">recursive-clients</code> is greater than
4839                   1000, the soft quota is set to
4840                   <code class="option">recursive-clients</code> minus 100;
4841                   otherwise it is set to 90% of
4842                   <code class="option">recursive-clients</code>.
4843                 </p>
4844 </dd>
4845 <dt><span class="term"><span><strong class="command">tcp-clients</strong></span></span></dt>
4846 <dd><p>
4847                   The maximum number of simultaneous client TCP
4848                   connections that the server will accept.
4849                   The default is <code class="literal">100</code>.
4850                 </p></dd>
4851 <dt>
4852 <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>
4853 </dt>
4854 <dd>
4855 <p>These set the
4856                   initial value (minimum) and maximum number of recursive
4857                   simultaneous clients for any given query
4858                   (&lt;qname,qtype,qclass&gt;) that the server will accept
4859                   before dropping additional clients.  <span><strong class="command">named</strong></span> will attempt to
4860                   self tune this value and changes will be logged.  The
4861                   default values are 10 and 100.
4862                 </p>
4863 <p>
4864                   This value should reflect how many queries come in for
4865                   a given name in the time it takes to resolve that name.
4866                   If the number of queries exceed this value, <span><strong class="command">named</strong></span> will
4867                   assume that it is dealing with a non-responsive zone
4868                   and will drop additional queries.  If it gets a response
4869                   after dropping queries, it will raise the estimate.  The
4870                   estimate will then be lowered in 20 minutes if it has
4871                   remained unchanged.
4872                 </p>
4873 <p>
4874                   If <span><strong class="command">clients-per-query</strong></span> is set to zero,
4875                   then there is no limit on the number of clients per query
4876                   and no queries will be dropped.
4877                 </p>
4878 <p>
4879                   If <span><strong class="command">max-clients-per-query</strong></span> is set to zero,
4880                   then there is no upper bound other than imposed by
4881                   <span><strong class="command">recursive-clients</strong></span>.
4882                 </p>
4883 </dd>
4884 <dt>
4885 <a name="fetches-per-zone"></a><span class="term"><span><strong class="command">fetches-per-zone</strong></span></span>
4886 </dt>
4887 <dd>
4888 <p>
4889                   The maximum number of simultaneous iterative
4890                   queries to any one domain that the server will
4891                   permit before blocking new queries for data
4892                   in or beneath that zone.
4893                   This value should reflect how many fetches would
4894                   normally be sent to any one zone in the time it
4895                   would take to resolve them.  It should be smaller
4896                   than <code class="option">recursive-clients</code>.
4897                 </p>
4898 <p>
4899                   When many clients simultaneously query for the
4900                   same name and type, the clients will all be attached
4901                   to the same fetch, up to the
4902                   <code class="option">max-clients-per-query</code> limit,
4903                   and only one iterative query will be sent.
4904                   However, when clients are simultaneously
4905                   querying for <span class="emphasis"><em>different</em></span> names
4906                   or types, multiple queries will be sent and
4907                   <code class="option">max-clients-per-query</code> is not
4908                   effective as a limit.
4909                 </p>
4910 <p>
4911                   Optionally, this value may be followed by the keyword
4912                   <code class="literal">drop</code> or <code class="literal">fail</code>,
4913                   indicating whether queries which exceed the fetch
4914                   quota for a zone will be dropped with no response,
4915                   or answered with SERVFAIL.  The default is
4916                   <code class="literal">drop</code>.
4917                 </p>
4918 <p>
4919                   If <span><strong class="command">fetches-per-zone</strong></span> is set to zero,
4920                   then there is no limit on the number of fetches per query
4921                   and no queries will be dropped.  The default is zero.
4922                 </p>
4923 <p>
4924                   The current list of active fetches can be dumped by
4925                   running <span><strong class="command">rndc recursing</strong></span>.  The list
4926                   includes the number of active fetches for each
4927                   domain and the number of queries that have been
4928                   passed or dropped as a result of the
4929                   <code class="option">fetches-per-zone</code> limit.  (Note:
4930                   these counters are not cumulative over time; whenever
4931                   the number of active fetches for a domain drops to
4932                   zero, the counter for that domain is deleted, and the
4933                   next time a fetch is sent to that domain, it is
4934                   recreated with the counters set to zero.)
4935                 </p>
4936 <p>
4937                   (Note: This option is only available when BIND is
4938                   built with <span><strong class="command">configure --enable-fetchlimit</strong></span>.)
4939                 </p>
4940 </dd>
4941 <dt>
4942 <a name="fetches-per-server"></a><span class="term"><span><strong class="command">fetches-per-server</strong></span></span>
4943 </dt>
4944 <dd>
4945 <p>
4946                   The maximum number of simultaneous iterative
4947                   queries that the server will allow to be sent to
4948                   a single upstream name server before blocking
4949                   additional queries.
4950                   This value should reflect how many fetches would
4951                   normally be sent to any one server in the time it
4952                   would take to resolve them.  It should be smaller
4953                   than <code class="option">recursive-clients</code>.
4954                 </p>
4955 <p>
4956                   Optionally, this value may be followed by the keyword
4957                   <code class="literal">drop</code> or <code class="literal">fail</code>,
4958                   indicating whether queries will be dropped with no
4959                   response, or answered with SERVFAIL, when all of the
4960                   servers authoritative for a zone are found to have
4961                   exceeded the per-server quota.  The default is
4962                   <code class="literal">fail</code>.
4963                 </p>
4964 <p>
4965                   If <span><strong class="command">fetches-per-server</strong></span> is set to zero,
4966                   then there is no limit on the number of fetches per query
4967                   and no queries will be dropped.  The default is zero.
4968                 </p>
4969 <p>
4970                   The <span><strong class="command">fetches-per-server</strong></span> quota is
4971                   dynamically adjusted in response to detected
4972                   congestion. As queries are sent to a server
4973                   and are either answered or time out, an
4974                   exponentially weighted moving average is calculated
4975                   of the ratio of timeouts to responses.  If the
4976                   current average timeout ratio rises above a "high"
4977                   threshold, then <span><strong class="command">fetches-per-server</strong></span>
4978                   is reduced for that server.  If the timeout ratio
4979                   drops below a "low" threshold, then
4980                   <span><strong class="command">fetches-per-server</strong></span> is increased.
4981                   The <span><strong class="command">fetch-quota-params</strong></span> options
4982                   can be used to adjust the parameters for this
4983                   calculation.
4984                 </p>
4985 <p>
4986                   (Note: This option is only available when BIND is
4987                   built with <span><strong class="command">configure --enable-fetchlimit</strong></span>.)
4988                 </p>
4989 </dd>
4990 <dt><span class="term"><span><strong class="command">fetch-quota-params</strong></span></span></dt>
4991 <dd>
4992 <p>
4993                   Sets the parameters to use for dynamic resizing of
4994                   the <code class="option">fetches-per-server</code> quota in
4995                   response to detected congestion.
4996                 </p>
4997 <p>
4998                   The first argument is an integer value indicating
4999                   how frequently to recalculate the moving average
5000                   of the ratio of timeouts to responses for each
5001                   server.  The default is 100, meaning we recalculate
5002                   the average ratio after every 100 queries have either
5003                   been answered or timed out.
5004                 </p>
5005 <p>
5006                   The remaining three arguments represent the "low"
5007                   threshold (defaulting to a timeout ratio of 0.1),
5008                   the "high" threshold (defaulting to a timeout
5009                   ratio of 0.3), and the discount rate for
5010                   the moving average (defaulting to 0.7).
5011                   A higher discount rate causes recent events to
5012                   weigh more heavily when calculating the moving
5013                   average; a lower discount rate causes past
5014                   events to weigh more heavily, smoothing out
5015                   short-term blips in the timeout ratio.
5016                   These arguments are all fixed-point numbers with
5017                   precision of 1/100: at most two places after
5018                   the decimal point are significant.
5019                 </p>
5020 <p>
5021                   (Note: This option is only available when BIND is
5022                   built with <span><strong class="command">configure --enable-fetchlimit</strong></span>.)
5023                 </p>
5024 </dd>
5025 <dt><span class="term"><span><strong class="command">reserved-sockets</strong></span></span></dt>
5026 <dd>
5027 <p>
5028                   The number of file descriptors reserved for TCP, stdio,
5029                   etc.  This needs to be big enough to cover the number of
5030                   interfaces <span><strong class="command">named</strong></span> listens on, <span><strong class="command">tcp-clients</strong></span> as well as
5031                   to provide room for outgoing TCP queries and incoming zone
5032                   transfers.  The default is <code class="literal">512</code>.
5033                   The minimum value is <code class="literal">128</code> and the
5034                   maximum value is <code class="literal">128</code> less than
5035                   maxsockets (-S).  This option may be removed in the future.
5036                 </p>
5037 <p>
5038                   This option has little effect on Windows.
5039                 </p>
5040 </dd>
5041 <dt><span class="term"><span><strong class="command">max-cache-size</strong></span></span></dt>
5042 <dd><p>
5043                   The maximum amount of memory to use for the
5044                   server's cache, in bytes.
5045                   When the amount of data in the cache
5046                   reaches this limit, the server will cause records to expire
5047                   prematurely based on an LRU based strategy so that
5048                   the limit is not exceeded.
5049                   A value of 0 is special, meaning that
5050                   records are purged from the cache only when their
5051                   TTLs expire.
5052                   Another special keyword <strong class="userinput"><code>unlimited</code></strong>
5053                   means the maximum value of 32-bit unsigned integers
5054                   (0xffffffff), which may not have the same effect as
5055                   0 on machines that support more than 32 bits of
5056                   memory space.
5057                   Any positive values less than 2MB will be ignored reset
5058                   to 2MB.
5059                   In a server with multiple views, the limit applies
5060                   separately to the cache of each view.
5061                   The default is 0.
5062                 </p></dd>
5063 <dt><span class="term"><span><strong class="command">tcp-listen-queue</strong></span></span></dt>
5064 <dd><p>
5065                   The listen queue depth.  The default and minimum is 10.
5066                   If the kernel supports the accept filter "dataready" this
5067                   also controls how
5068                   many TCP connections that will be queued in kernel space
5069                   waiting for
5070                   some data before being passed to accept.  Nonzero values
5071                   less than 10 will be silently raised. A value of 0 may also
5072                   be used; on most platforms this sets the listen queue
5073                   length to a system-defined default value.
5074                 </p></dd>
5075 </dl></div>
5076 </div>
5077 <div class="sect3" lang="en">
5078 <div class="titlepage"><div><div><h4 class="title">
5079 <a name="id2586413"></a>Periodic Task Intervals</h4></div></div></div>
5080 <div class="variablelist"><dl>
5081 <dt><span class="term"><span><strong class="command">cleaning-interval</strong></span></span></dt>
5082 <dd><p>
5083                   This interval is effectively obsolete.  Previously,
5084                   the server would remove expired resource records
5085                   from the cache every <span><strong class="command">cleaning-interval</strong></span> minutes.
5086                   <acronym class="acronym">BIND</acronym> 9 now manages cache
5087                   memory in a more sophisticated manner and does not
5088                   rely on the periodic cleaning any more.
5089                   Specifying this option therefore has no effect on
5090                   the server's behavior.
5091                 </p></dd>
5092 <dt><span class="term"><span><strong class="command">heartbeat-interval</strong></span></span></dt>
5093 <dd><p>
5094                   The server will perform zone maintenance tasks
5095                   for all zones marked as <span><strong class="command">dialup</strong></span> whenever this
5096                   interval expires. The default is 60 minutes. Reasonable
5097                   values are up
5098                   to 1 day (1440 minutes).  The maximum value is 28 days
5099                   (40320 minutes).
5100                   If set to 0, no zone maintenance for these zones will occur.
5101                 </p></dd>
5102 <dt><span class="term"><span><strong class="command">interface-interval</strong></span></span></dt>
5103 <dd><p>
5104                   The server will scan the network interface list
5105                   every <span><strong class="command">interface-interval</strong></span>
5106                   minutes. The default
5107                   is 60 minutes. The maximum value is 28 days (40320 minutes).
5108                   If set to 0, interface scanning will only occur when
5109                   the configuration file is  loaded. After the scan, the
5110                   server will
5111                   begin listening for queries on any newly discovered
5112                   interfaces (provided they are allowed by the
5113                   <span><strong class="command">listen-on</strong></span> configuration), and
5114                   will
5115                   stop listening on interfaces that have gone away.
5116                 </p></dd>
5117 <dt><span class="term"><span><strong class="command">statistics-interval</strong></span></span></dt>
5118 <dd>
5119 <p>
5120                   Name server statistics will be logged
5121                   every <span><strong class="command">statistics-interval</strong></span>
5122                   minutes. The default is
5123                   60. The maximum value is 28 days (40320 minutes).
5124                   If set to 0, no statistics will be logged.
5125                   </p>
5126 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5127 <h3 class="title">Note</h3>
5128 <p>
5129                     Not yet implemented in
5130                     <acronym class="acronym">BIND</acronym> 9.
5131                   </p>
5132 </div>
5133 </dd>
5134 </dl></div>
5135 </div>
5136 <div class="sect3" lang="en">
5137 <div class="titlepage"><div><div><h4 class="title">
5138 <a name="topology"></a>Topology</h4></div></div></div>
5139 <p>
5140             All other things being equal, when the server chooses a name
5141             server
5142             to query from a list of name servers, it prefers the one that is
5143             topologically closest to itself. The <span><strong class="command">topology</strong></span> statement
5144             takes an <span><strong class="command">address_match_list</strong></span> and
5145             interprets it
5146             in a special way. Each top-level list element is assigned a
5147             distance.
5148             Non-negated elements get a distance based on their position in the
5149             list, where the closer the match is to the start of the list, the
5150             shorter the distance is between it and the server. A negated match
5151             will be assigned the maximum distance from the server. If there
5152             is no match, the address will get a distance which is further than
5153             any non-negated list element, and closer than any negated element.
5154             For example,
5155           </p>
5156 <pre class="programlisting">topology {
5157     10/8;
5158     !1.2.3/24;
5159     { 1.2/16; 3/8; };
5160 };</pre>
5161 <p>
5162             will prefer servers on network 10 the most, followed by hosts
5163             on network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the
5164             exception of hosts on network 1.2.3 (netmask 255.255.255.0), which
5165             is preferred least of all.
5166           </p>
5167 <p>
5168             The default topology is
5169           </p>
5170 <pre class="programlisting">    topology { localhost; localnets; };
5171 </pre>
5172 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5173 <h3 class="title">Note</h3>
5174 <p>
5175               The <span><strong class="command">topology</strong></span> option
5176               is not implemented in <acronym class="acronym">BIND</acronym> 9.
5177             </p>
5178 </div>
5179 </div>
5180 <div class="sect3" lang="en">
5181 <div class="titlepage"><div><div><h4 class="title">
5182 <a name="the_sortlist_statement"></a>The <span><strong class="command">sortlist</strong></span> Statement</h4></div></div></div>
5183 <p>
5184             The response to a DNS query may consist of multiple resource
5185             records (RRs) forming a resource records set (RRset).
5186             The name server will normally return the
5187             RRs within the RRset in an indeterminate order
5188             (but see the <span><strong class="command">rrset-order</strong></span>
5189             statement in <a href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">the section called &#8220;RRset Ordering&#8221;</a>).
5190             The client resolver code should rearrange the RRs as appropriate,
5191             that is, using any addresses on the local net in preference to
5192             other addresses.
5193             However, not all resolvers can do this or are correctly
5194             configured.
5195             When a client is using a local server, the sorting can be performed
5196             in the server, based on the client's address. This only requires
5197             configuring the name servers, not all the clients.
5198           </p>
5199 <p>
5200             The <span><strong class="command">sortlist</strong></span> statement (see below)
5201             takes
5202             an <span><strong class="command">address_match_list</strong></span> and
5203             interprets it even
5204             more specifically than the <span><strong class="command">topology</strong></span>
5205             statement
5206             does (<a href="Bv9ARM.ch06.html#topology" title="Topology">the section called &#8220;Topology&#8221;</a>).
5207             Each top level statement in the <span><strong class="command">sortlist</strong></span> must
5208             itself be an explicit <span><strong class="command">address_match_list</strong></span> with
5209             one or two elements. The first element (which may be an IP
5210             address,
5211             an IP prefix, an ACL name or a nested <span><strong class="command">address_match_list</strong></span>)
5212             of each top level list is checked against the source address of
5213             the query until a match is found.
5214           </p>
5215 <p>
5216             Once the source address of the query has been matched, if
5217             the top level statement contains only one element, the actual
5218             primitive
5219             element that matched the source address is used to select the
5220             address
5221             in the response to move to the beginning of the response. If the
5222             statement is a list of two elements, then the second element is
5223             treated the same as the <span><strong class="command">address_match_list</strong></span> in
5224             a <span><strong class="command">topology</strong></span> statement. Each top
5225             level element
5226             is assigned a distance and the address in the response with the
5227             minimum
5228             distance is moved to the beginning of the response.
5229           </p>
5230 <p>
5231             In the following example, any queries received from any of
5232             the addresses of the host itself will get responses preferring
5233             addresses
5234             on any of the locally connected networks. Next most preferred are
5235             addresses
5236             on the 192.168.1/24 network, and after that either the
5237             192.168.2/24
5238             or
5239             192.168.3/24 network with no preference shown between these two
5240             networks. Queries received from a host on the 192.168.1/24 network
5241             will prefer other addresses on that network to the 192.168.2/24
5242             and
5243             192.168.3/24 networks. Queries received from a host on the
5244             192.168.4/24
5245             or the 192.168.5/24 network will only prefer other addresses on
5246             their directly connected networks.
5247           </p>
5248 <pre class="programlisting">sortlist {
5249     // IF the local host
5250     // THEN first fit on the following nets
5251     { localhost;
5252         { localnets;
5253             192.168.1/24;
5254             { 192.168.2/24; 192.168.3/24; }; }; };
5255     // IF on class C 192.168.1 THEN use .1, or .2 or .3
5256     { 192.168.1/24;
5257         { 192.168.1/24;
5258             { 192.168.2/24; 192.168.3/24; }; }; };
5259     // IF on class C 192.168.2 THEN use .2, or .1 or .3
5260     { 192.168.2/24;
5261         { 192.168.2/24;
5262             { 192.168.1/24; 192.168.3/24; }; }; };
5263     // IF on class C 192.168.3 THEN use .3, or .1 or .2
5264     { 192.168.3/24;
5265         { 192.168.3/24;
5266             { 192.168.1/24; 192.168.2/24; }; }; };
5267     // IF .4 or .5 THEN prefer that net
5268     { { 192.168.4/24; 192.168.5/24; };
5269     };
5270 };</pre>
5271 <p>
5272             The following example will give reasonable behavior for the
5273             local host and hosts on directly connected networks. It is similar
5274             to the behavior of the address sort in <acronym class="acronym">BIND</acronym> 4.9.x. Responses sent
5275             to queries from the local host will favor any of the directly
5276             connected
5277             networks. Responses sent to queries from any other hosts on a
5278             directly
5279             connected network will prefer addresses on that same network.
5280             Responses
5281             to other queries will not be sorted.
5282           </p>
5283 <pre class="programlisting">sortlist {
5284            { localhost; localnets; };
5285            { localnets; };
5286 };
5287 </pre>
5288 </div>
5289 <div class="sect3" lang="en">
5290 <div class="titlepage"><div><div><h4 class="title">
5291 <a name="rrset_ordering"></a>RRset Ordering</h4></div></div></div>
5292 <p>
5293             When multiple records are returned in an answer it may be
5294             useful to configure the order of the records placed into the
5295             response.
5296             The <span><strong class="command">rrset-order</strong></span> statement permits
5297             configuration
5298             of the ordering of the records in a multiple record response.
5299             See also the <span><strong class="command">sortlist</strong></span> statement,
5300             <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>.
5301           </p>
5302 <p>
5303             An <span><strong class="command">order_spec</strong></span> is defined as
5304             follows:
5305           </p>
5306 <p>
5307             [<span class="optional">class <em class="replaceable"><code>class_name</code></em></span>]
5308             [<span class="optional">type <em class="replaceable"><code>type_name</code></em></span>]
5309             [<span class="optional">name <em class="replaceable"><code>"domain_name"</code></em></span>]
5310             order <em class="replaceable"><code>ordering</code></em>
5311           </p>
5312 <p>
5313             If no class is specified, the default is <span><strong class="command">ANY</strong></span>.
5314             If no type is specified, the default is <span><strong class="command">ANY</strong></span>.
5315             If no name is specified, the default is "<span><strong class="command">*</strong></span>" (asterisk).
5316           </p>
5317 <p>
5318             The legal values for <span><strong class="command">ordering</strong></span> are:
5319           </p>
5320 <div class="informaltable"><table border="1">
5321 <colgroup>
5322 <col>
5323 <col>
5324 </colgroup>
5325 <tbody>
5326 <tr>
5327 <td>
5328                     <p><span><strong class="command">fixed</strong></span></p>
5329                   </td>
5330 <td>
5331                     <p>
5332                       Records are returned in the order they
5333                       are defined in the zone file.
5334                     </p>
5335                   </td>
5336 </tr>
5337 <tr>
5338 <td>
5339                     <p><span><strong class="command">random</strong></span></p>
5340                   </td>
5341 <td>
5342                     <p>
5343                       Records are returned in some random order.
5344                     </p>
5345                   </td>
5346 </tr>
5347 <tr>
5348 <td>
5349                     <p><span><strong class="command">cyclic</strong></span></p>
5350                   </td>
5351 <td>
5352                     <p>
5353                       Records are returned in a cyclic round-robin order.
5354                     </p>
5355                     <p>
5356                       If <acronym class="acronym">BIND</acronym> is configured with the
5357                       "--enable-fixed-rrset" option at compile time, then
5358                       the initial ordering of the RRset will match the
5359                       one specified in the zone file.
5360                     </p>
5361                   </td>
5362 </tr>
5363 </tbody>
5364 </table></div>
5365 <p>
5366             For example:
5367           </p>
5368 <pre class="programlisting">rrset-order {
5369    class IN type A name "host.example.com" order random;
5370    order cyclic;
5371 };
5372 </pre>
5373 <p>
5374             will cause any responses for type A records in class IN that
5375             have "<code class="literal">host.example.com</code>" as a
5376             suffix, to always be returned
5377             in random order. All other records are returned in cyclic order.
5378           </p>
5379 <p>
5380             If multiple <span><strong class="command">rrset-order</strong></span> statements
5381             appear, they are not combined &#8212; the last one applies.
5382           </p>
5383 <p>
5384             By default, all records are returned in random order.
5385           </p>
5386 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5387 <h3 class="title">Note</h3>
5388 <p>
5389               In this release of <acronym class="acronym">BIND</acronym> 9, the
5390               <span><strong class="command">rrset-order</strong></span> statement does not support
5391               "fixed" ordering by default.  Fixed ordering can be enabled
5392               at compile time by specifying "--enable-fixed-rrset" on
5393               the "configure" command line.
5394             </p>
5395 </div>
5396 </div>
5397 <div class="sect3" lang="en">
5398 <div class="titlepage"><div><div><h4 class="title">
5399 <a name="tuning"></a>Tuning</h4></div></div></div>
5400 <div class="variablelist"><dl>
5401 <dt><span class="term"><span><strong class="command">lame-ttl</strong></span></span></dt>
5402 <dd>
5403 <p>
5404                   Sets the number of seconds to cache a
5405                   lame server indication. 0 disables caching. (This is
5406                   <span class="bold"><strong>NOT</strong></span> recommended.)
5407                   The default is <code class="literal">600</code> (10 minutes) and the
5408                   maximum value is
5409                   <code class="literal">1800</code> (30 minutes).
5410                 </p>
5411 <p>
5412                   Lame-ttl also controls the amount of time DNSSEC
5413                   validation failures are cached.  There is a minimum
5414                   of 30 seconds applied to bad cache entries if the
5415                   lame-ttl is set to less than 30 seconds.
5416                 </p>
5417 </dd>
5418 <dt><span class="term"><span><strong class="command">max-ncache-ttl</strong></span></span></dt>
5419 <dd><p>
5420                   To reduce network traffic and increase performance,
5421                   the server stores negative answers. <span><strong class="command">max-ncache-ttl</strong></span> is
5422                   used to set a maximum retention time for these answers in
5423                   the server
5424                   in seconds. The default
5425                   <span><strong class="command">max-ncache-ttl</strong></span> is <code class="literal">10800</code> seconds (3 hours).
5426                   <span><strong class="command">max-ncache-ttl</strong></span> cannot exceed
5427                   7 days and will
5428                   be silently truncated to 7 days if set to a greater value.
5429                 </p></dd>
5430 <dt><span class="term"><span><strong class="command">max-cache-ttl</strong></span></span></dt>
5431 <dd><p>
5432                   Sets the maximum time for which the server will
5433                   cache ordinary (positive) answers. The default is
5434                   one week (7 days).
5435                   A value of zero may cause all queries to return
5436                   SERVFAIL, because of lost caches of intermediate
5437                   RRsets (such as NS and glue AAAA/A records) in the
5438                   resolution process.
5439                 </p></dd>
5440 <dt><span class="term"><span><strong class="command">min-roots</strong></span></span></dt>
5441 <dd>
5442 <p>
5443                   The minimum number of root servers that
5444                   is required for a request for the root servers to be
5445                   accepted. The default
5446                   is <strong class="userinput"><code>2</code></strong>.
5447                 </p>
5448 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5449 <h3 class="title">Note</h3>
5450 <p>
5451                     Not implemented in <acronym class="acronym">BIND</acronym> 9.
5452                   </p>
5453 </div>
5454 </dd>
5455 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
5456 <dd>
5457 <p>
5458                   Specifies the number of days into the future when
5459                   DNSSEC signatures automatically generated as a
5460                   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
5461                   is an optional second field which specifies how
5462                   long before expiry that the signatures will be
5463                   regenerated.  If not specified, the signatures will
5464                   be regenerated at 1/4 of base interval.  The second
5465                   field is specified in days if the base interval is
5466                   greater than 7 days otherwise it is specified in hours.
5467                   The default base interval is <code class="literal">30</code> days
5468                   giving a re-signing interval of 7 1/2 days.  The maximum
5469                   values are 10 years (3660 days).
5470                 </p>
5471 <p>
5472                   The signature inception time is unconditionally
5473                   set to one hour before the current time to allow
5474                   for a limited amount of clock skew.
5475                 </p>
5476 <p>
5477                   The <span><strong class="command">sig-validity-interval</strong></span>
5478                   should be, at least, several multiples of the SOA
5479                   expire interval to allow for reasonable interaction
5480                   between the various timer and expiry dates.
5481                 </p>
5482 </dd>
5483 <dt><span class="term"><span><strong class="command">sig-signing-nodes</strong></span></span></dt>
5484 <dd><p>
5485                   Specify the maximum number of nodes to be
5486                   examined in each quantum when signing a zone with
5487                   a new DNSKEY. The default is
5488                   <code class="literal">100</code>.
5489                 </p></dd>
5490 <dt><span class="term"><span><strong class="command">sig-signing-signatures</strong></span></span></dt>
5491 <dd><p>
5492                   Specify a threshold number of signatures that
5493                   will terminate processing a quantum when signing
5494                   a zone with a new DNSKEY.  The default is
5495                   <code class="literal">10</code>.
5496                 </p></dd>
5497 <dt><span class="term"><span><strong class="command">sig-signing-type</strong></span></span></dt>
5498 <dd>
5499 <p>
5500                   Specify a private RDATA type to be used when generating
5501                   signing state records.  The default is
5502                   <code class="literal">65534</code>.
5503                 </p>
5504 <p>
5505                   It is expected that this parameter may be removed
5506                   in a future version once there is a standard type.
5507                 </p>
5508 <p>
5509                   Signing state records are used to internally by
5510                   <span><strong class="command">named</strong></span> to track the current state of
5511                   a zone-signing process, i.e., whether it is still active
5512                   or has been completed.  The records can be inspected
5513                   using the command
5514                   <span><strong class="command">rndc signing -list <em class="replaceable"><code>zone</code></em></strong></span>.
5515                   Once <span><strong class="command">named</strong></span> has finished signing
5516                   a zone with a particular key, the signing state
5517                   record associated with that key can be removed from
5518                   the zone by running
5519                   <span><strong class="command">rndc signing -clear <em class="replaceable"><code>keyid/algorithm</code></em> <em class="replaceable"><code>zone</code></em></strong></span>.
5520                   To clear all of the completed signing state
5521                   records for a zone, use
5522                   <span><strong class="command">rndc signing -clear all <em class="replaceable"><code>zone</code></em></strong></span>.
5523                 </p>
5524 </dd>
5525 <dt>
5526 <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>
5527 </dt>
5528 <dd>
5529 <p>
5530                   These options control the server's behavior on refreshing a
5531                   zone
5532                   (querying for SOA changes) or retrying failed transfers.
5533                   Usually the SOA values for the zone are used, but these
5534                   values
5535                   are set by the master, giving slave server administrators
5536                   little
5537                   control over their contents.
5538                 </p>
5539 <p>
5540                   These options allow the administrator to set a minimum and
5541                   maximum
5542                   refresh and retry time either per-zone, per-view, or
5543                   globally.
5544                   These options are valid for slave and stub zones,
5545                   and clamp the SOA refresh and retry times to the specified
5546                   values.
5547                 </p>
5548 <p>
5549                   The following defaults apply.
5550                   <span><strong class="command">min-refresh-time</strong></span> 300 seconds,
5551                   <span><strong class="command">max-refresh-time</strong></span> 2419200 seconds
5552                   (4 weeks), <span><strong class="command">min-retry-time</strong></span> 500 seconds,
5553                   and <span><strong class="command">max-retry-time</strong></span> 1209600 seconds
5554                   (2 weeks).
5555                 </p>
5556 </dd>
5557 <dt><span class="term"><span><strong class="command">edns-udp-size</strong></span></span></dt>
5558 <dd>
5559 <p>
5560                   Sets the advertised EDNS UDP buffer size in bytes
5561                   to control the size of packets received.
5562                   Valid values are 512 to 4096 (values outside this range
5563                   will be silently adjusted).  The default value
5564                   is 4096.  The usual reason for setting
5565                   <span><strong class="command">edns-udp-size</strong></span> to a non-default
5566                   value is to get UDP answers to pass through broken
5567                   firewalls that block fragmented packets and/or
5568                   block UDP packets that are greater than 512 bytes.
5569                 </p>
5570 <p>
5571                   <span><strong class="command">named</strong></span> will fallback to using 512 bytes
5572                   if it get a series of timeout at the initial value.  512
5573                   bytes is not being offered to encourage sites to fix their
5574                   firewalls.  Small EDNS UDP sizes will result in the
5575                   excessive use of TCP.
5576                 </p>
5577 </dd>
5578 <dt><span class="term"><span><strong class="command">max-udp-size</strong></span></span></dt>
5579 <dd>
5580 <p>
5581                   Sets the maximum EDNS UDP message size
5582                   <span><strong class="command">named</strong></span> will send in bytes.
5583                   Valid values are 512 to 4096 (values outside this
5584                   range will be silently adjusted).  The default
5585                   value is 4096.  The usual reason for setting
5586                   <span><strong class="command">max-udp-size</strong></span> to a non-default
5587                   value is to get UDP answers to pass through broken
5588                   firewalls that block fragmented packets and/or
5589                   block UDP packets that are greater than 512 bytes.
5590                   This is independent of the advertised receive
5591                   buffer (<span><strong class="command">edns-udp-size</strong></span>).
5592                 </p>
5593 <p>
5594                   Setting this to a low value will encourage additional
5595                   TCP traffic to the nameserver.
5596                 </p>
5597 </dd>
5598 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
5599 <dd>
5600 <p>Specifies
5601                   the file format of zone files (see
5602                   <a href="Bv9ARM.ch06.html#zonefile_format" title="Additional File Formats">the section called &#8220;Additional File Formats&#8221;</a>).
5603                   The default value is <code class="constant">text</code>, which is the
5604                   standard textual representation, except for slave zones,
5605                   in which the default value is <code class="constant">raw</code>.
5606                   Files in other formats than <code class="constant">text</code> are
5607                   typically expected to be generated by the
5608                   <span><strong class="command">named-compilezone</strong></span> tool, or dumped by
5609                   <span><strong class="command">named</strong></span>.
5610                 </p>
5611 <p>
5612                   Note that when a zone file in a different format than
5613                   <code class="constant">text</code> is loaded, <span><strong class="command">named</strong></span>
5614                   may omit some of the checks which would be performed for a
5615                   file in the <code class="constant">text</code> format.  In particular,
5616                   <span><strong class="command">check-names</strong></span> checks do not apply
5617                   for the <code class="constant">raw</code> format.  This means
5618                   a zone file in the <code class="constant">raw</code> format
5619                   must be generated with the same check level as that
5620                   specified in the <span><strong class="command">named</strong></span> configuration
5621                   file.  This statement sets the
5622                   <span><strong class="command">masterfile-format</strong></span> for all zones,
5623                   but can be overridden on a per-zone or per-view basis
5624                   by including a <span><strong class="command">masterfile-format</strong></span>
5625                   statement within the <span><strong class="command">zone</strong></span> or
5626                   <span><strong class="command">view</strong></span> block in the configuration
5627                   file.
5628                 </p>
5629 </dd>
5630 <dt>
5631 <a name="max-recursion-depth"></a><span class="term"><span><strong class="command">max-recursion-depth</strong></span></span>
5632 </dt>
5633 <dd><p>
5634                   Sets the maximum number of levels of recursion
5635                   that are permitted at any one time while servicing
5636                   a recursive query. Resolving a name may require
5637                   looking up a name server address, which in turn
5638                   requires resolving another name, etc; if the number
5639                   of indirections exceeds this value, the recursive
5640                   query is terminated and returns SERVFAIL.  The
5641                   default is 7.
5642                 </p></dd>
5643 <dt>
5644 <a name="max-recursion-queries"></a><span class="term"><span><strong class="command">max-recursion-queries</strong></span></span>
5645 </dt>
5646 <dd><p>
5647                   Sets the maximum number of iterative queries that
5648                   may be sent while servicing a recursive query.
5649                   If more queries are sent, the recursive query
5650                   is terminated and returns SERVFAIL. Queries to
5651                   look up top level comains such as "com" and "net"
5652                   and the DNS root zone are exempt from this limitation.
5653                   The default is 75.
5654                 </p></dd>
5655 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
5656 <dd>
5657 <p>
5658                   The delay, in seconds, between sending sets of notify
5659                   messages for a zone.  The default is five (5) seconds.
5660                 </p>
5661 <p>
5662                   The overall rate that NOTIFY messages are sent for all
5663                   zones is controlled by <span><strong class="command">serial-query-rate</strong></span>.
5664                 </p>
5665 </dd>
5666 <dt><span class="term"><span><strong class="command">max-rsa-exponent-size</strong></span></span></dt>
5667 <dd><p>
5668                   The maximum RSA exponent size, in bits, that will
5669                   be accepted when validating.  Valid values are 35
5670                   to 4096 bits.  The default zero (0) is also accepted
5671                   and is equivalent to 4096.
5672                 </p></dd>
5673 </dl></div>
5674 </div>
5675 <div class="sect3" lang="en">
5676 <div class="titlepage"><div><div><h4 class="title">
5677 <a name="builtin"></a>Built-in server information zones</h4></div></div></div>
5678 <p>
5679             The server provides some helpful diagnostic information
5680             through a number of built-in zones under the
5681             pseudo-top-level-domain <code class="literal">bind</code> in the
5682             <span><strong class="command">CHAOS</strong></span> class.  These zones are part
5683             of a
5684             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
5685             class
5686             <span><strong class="command">CHAOS</strong></span> which is separate from the
5687             default view of class <span><strong class="command">IN</strong></span>. Most global
5688             configuration options (<span><strong class="command">allow-query</strong></span>,
5689             etc) will apply to this view, but some are locally
5690             overridden: <span><strong class="command">notify</strong></span>,
5691             <span><strong class="command">recursion</strong></span> and
5692             <span><strong class="command">allow-new-zones</strong></span> are
5693             always set to <strong class="userinput"><code>no</code></strong>.
5694           </p>
5695 <p>
5696             If you need to disable these zones, use the options
5697             below, or hide the built-in <span><strong class="command">CHAOS</strong></span>
5698             view by
5699             defining an explicit view of class <span><strong class="command">CHAOS</strong></span>
5700             that matches all clients.
5701           </p>
5702 <div class="variablelist"><dl>
5703 <dt><span class="term"><span><strong class="command">version</strong></span></span></dt>
5704 <dd><p>
5705                   The version the server should report
5706                   via a query of the name <code class="literal">version.bind</code>
5707                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5708                   The default is the real version number of this server.
5709                   Specifying <span><strong class="command">version none</strong></span>
5710                   disables processing of the queries.
5711                 </p></dd>
5712 <dt><span class="term"><span><strong class="command">hostname</strong></span></span></dt>
5713 <dd><p>
5714                   The hostname the server should report via a query of
5715                   the name <code class="filename">hostname.bind</code>
5716                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5717                   This defaults to the hostname of the machine hosting the
5718                   name server as
5719                   found by the gethostname() function.  The primary purpose of such queries
5720                   is to
5721                   identify which of a group of anycast servers is actually
5722                   answering your queries.  Specifying <span><strong class="command">hostname none;</strong></span>
5723                   disables processing of the queries.
5724                 </p></dd>
5725 <dt><span class="term"><span><strong class="command">server-id</strong></span></span></dt>
5726 <dd><p>
5727                   The ID the server should report when receiving a Name
5728                   Server Identifier (NSID) query, or a query of the name
5729                   <code class="filename">ID.SERVER</code> with type
5730                   <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5731                   The primary purpose of such queries is to
5732                   identify which of a group of anycast servers is actually
5733                   answering your queries.  Specifying <span><strong class="command">server-id none;</strong></span>
5734                   disables processing of the queries.
5735                   Specifying <span><strong class="command">server-id hostname;</strong></span> will cause <span><strong class="command">named</strong></span> to
5736                   use the hostname as found by the gethostname() function.
5737                   The default <span><strong class="command">server-id</strong></span> is <span><strong class="command">none</strong></span>.
5738                 </p></dd>
5739 </dl></div>
5740 </div>
5741 <div class="sect3" lang="en">
5742 <div class="titlepage"><div><div><h4 class="title">
5743 <a name="empty"></a>Built-in Empty Zones</h4></div></div></div>
5744 <p>
5745             Named has some built-in empty zones (SOA and NS records only).
5746             These are for zones that should normally be answered locally
5747             and which queries should not be sent to the Internet's root
5748             servers.  The official servers which cover these namespaces
5749             return NXDOMAIN responses to these queries.  In particular,
5750             these cover the reverse namespaces for addresses from
5751             RFC 1918, RFC 4193, RFC 5737 and RFC 6598.  They also include the
5752             reverse namespace for IPv6 local address (locally assigned),
5753             IPv6 link local addresses, the IPv6 loopback address and the
5754             IPv6 unknown address.
5755           </p>
5756 <p>
5757             Named will attempt to determine if a built-in zone already exists
5758             or is active (covered by a forward-only forwarding declaration)
5759             and will not create an empty zone in that case.
5760           </p>
5761 <p>
5762             The current list of empty zones is:
5763             </p>
5764 <div class="itemizedlist"><ul type="disc">
5765 <li>10.IN-ADDR.ARPA</li>
5766 <li>16.172.IN-ADDR.ARPA</li>
5767 <li>17.172.IN-ADDR.ARPA</li>
5768 <li>18.172.IN-ADDR.ARPA</li>
5769 <li>19.172.IN-ADDR.ARPA</li>
5770 <li>20.172.IN-ADDR.ARPA</li>
5771 <li>21.172.IN-ADDR.ARPA</li>
5772 <li>22.172.IN-ADDR.ARPA</li>
5773 <li>23.172.IN-ADDR.ARPA</li>
5774 <li>24.172.IN-ADDR.ARPA</li>
5775 <li>25.172.IN-ADDR.ARPA</li>
5776 <li>26.172.IN-ADDR.ARPA</li>
5777 <li>27.172.IN-ADDR.ARPA</li>
5778 <li>28.172.IN-ADDR.ARPA</li>
5779 <li>29.172.IN-ADDR.ARPA</li>
5780 <li>30.172.IN-ADDR.ARPA</li>
5781 <li>31.172.IN-ADDR.ARPA</li>
5782 <li>168.192.IN-ADDR.ARPA</li>
5783 <li>64.100.IN-ADDR.ARPA</li>
5784 <li>65.100.IN-ADDR.ARPA</li>
5785 <li>66.100.IN-ADDR.ARPA</li>
5786 <li>67.100.IN-ADDR.ARPA</li>
5787 <li>68.100.IN-ADDR.ARPA</li>
5788 <li>69.100.IN-ADDR.ARPA</li>
5789 <li>70.100.IN-ADDR.ARPA</li>
5790 <li>71.100.IN-ADDR.ARPA</li>
5791 <li>72.100.IN-ADDR.ARPA</li>
5792 <li>73.100.IN-ADDR.ARPA</li>
5793 <li>74.100.IN-ADDR.ARPA</li>
5794 <li>75.100.IN-ADDR.ARPA</li>
5795 <li>76.100.IN-ADDR.ARPA</li>
5796 <li>77.100.IN-ADDR.ARPA</li>
5797 <li>78.100.IN-ADDR.ARPA</li>
5798 <li>79.100.IN-ADDR.ARPA</li>
5799 <li>80.100.IN-ADDR.ARPA</li>
5800 <li>81.100.IN-ADDR.ARPA</li>
5801 <li>82.100.IN-ADDR.ARPA</li>
5802 <li>83.100.IN-ADDR.ARPA</li>
5803 <li>84.100.IN-ADDR.ARPA</li>
5804 <li>85.100.IN-ADDR.ARPA</li>
5805 <li>86.100.IN-ADDR.ARPA</li>
5806 <li>87.100.IN-ADDR.ARPA</li>
5807 <li>88.100.IN-ADDR.ARPA</li>
5808 <li>89.100.IN-ADDR.ARPA</li>
5809 <li>90.100.IN-ADDR.ARPA</li>
5810 <li>91.100.IN-ADDR.ARPA</li>
5811 <li>92.100.IN-ADDR.ARPA</li>
5812 <li>93.100.IN-ADDR.ARPA</li>
5813 <li>94.100.IN-ADDR.ARPA</li>
5814 <li>95.100.IN-ADDR.ARPA</li>
5815 <li>96.100.IN-ADDR.ARPA</li>
5816 <li>97.100.IN-ADDR.ARPA</li>
5817 <li>98.100.IN-ADDR.ARPA</li>
5818 <li>99.100.IN-ADDR.ARPA</li>
5819 <li>100.100.IN-ADDR.ARPA</li>
5820 <li>101.100.IN-ADDR.ARPA</li>
5821 <li>102.100.IN-ADDR.ARPA</li>
5822 <li>103.100.IN-ADDR.ARPA</li>
5823 <li>104.100.IN-ADDR.ARPA</li>
5824 <li>105.100.IN-ADDR.ARPA</li>
5825 <li>106.100.IN-ADDR.ARPA</li>
5826 <li>107.100.IN-ADDR.ARPA</li>
5827 <li>108.100.IN-ADDR.ARPA</li>
5828 <li>109.100.IN-ADDR.ARPA</li>
5829 <li>110.100.IN-ADDR.ARPA</li>
5830 <li>111.100.IN-ADDR.ARPA</li>
5831 <li>112.100.IN-ADDR.ARPA</li>
5832 <li>113.100.IN-ADDR.ARPA</li>
5833 <li>114.100.IN-ADDR.ARPA</li>
5834 <li>115.100.IN-ADDR.ARPA</li>
5835 <li>116.100.IN-ADDR.ARPA</li>
5836 <li>117.100.IN-ADDR.ARPA</li>
5837 <li>118.100.IN-ADDR.ARPA</li>
5838 <li>119.100.IN-ADDR.ARPA</li>
5839 <li>120.100.IN-ADDR.ARPA</li>
5840 <li>121.100.IN-ADDR.ARPA</li>
5841 <li>122.100.IN-ADDR.ARPA</li>
5842 <li>123.100.IN-ADDR.ARPA</li>
5843 <li>124.100.IN-ADDR.ARPA</li>
5844 <li>125.100.IN-ADDR.ARPA</li>
5845 <li>126.100.IN-ADDR.ARPA</li>
5846 <li>127.100.IN-ADDR.ARPA</li>
5847 <li>0.IN-ADDR.ARPA</li>
5848 <li>127.IN-ADDR.ARPA</li>
5849 <li>254.169.IN-ADDR.ARPA</li>
5850 <li>2.0.192.IN-ADDR.ARPA</li>
5851 <li>100.51.198.IN-ADDR.ARPA</li>
5852 <li>113.0.203.IN-ADDR.ARPA</li>
5853 <li>255.255.255.255.IN-ADDR.ARPA</li>
5854 <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>
5855 <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>
5856 <li>8.B.D.0.1.0.0.2.IP6.ARPA</li>
5857 <li>D.F.IP6.ARPA</li>
5858 <li>8.E.F.IP6.ARPA</li>
5859 <li>9.E.F.IP6.ARPA</li>
5860 <li>A.E.F.IP6.ARPA</li>
5861 <li>B.E.F.IP6.ARPA</li>
5862 </ul></div>
5863 <p>
5864           </p>
5865 <p>
5866             Empty zones are settable at the view level and only apply to
5867             views of class IN.  Disabled empty zones are only inherited
5868             from options if there are no disabled empty zones specified
5869             at the view level.  To override the options list of disabled
5870             zones, you can disable the root zone at the view level, for example:
5871 </p>
5872 <pre class="programlisting">
5873             disable-empty-zone ".";
5874 </pre>
5875 <p>
5876           </p>
5877 <p>
5878             If you are using the address ranges covered here, you should
5879             already have reverse zones covering the addresses you use.
5880             In practice this appears to not be the case with many queries
5881             being made to the infrastructure servers for names in these
5882             spaces.  So many in fact that sacrificial servers were needed
5883             to be deployed to channel the query load away from the
5884             infrastructure servers.
5885           </p>
5886 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5887 <h3 class="title">Note</h3>
5888             The real parent servers for these zones should disable all
5889             empty zone under the parent zone they serve.  For the real
5890             root servers, this is all built-in empty zones.  This will
5891             enable them to return referrals to deeper in the tree.
5892           </div>
5893 <div class="variablelist"><dl>
5894 <dt><span class="term"><span><strong class="command">empty-server</strong></span></span></dt>
5895 <dd><p>
5896                   Specify what server name will appear in the returned
5897                   SOA record for empty zones.  If none is specified, then
5898                   the zone's name will be used.
5899                 </p></dd>
5900 <dt><span class="term"><span><strong class="command">empty-contact</strong></span></span></dt>
5901 <dd><p>
5902                   Specify what contact name will appear in the returned
5903                   SOA record for empty zones.  If none is specified, then
5904                   "." will be used.
5905                 </p></dd>
5906 <dt><span class="term"><span><strong class="command">empty-zones-enable</strong></span></span></dt>
5907 <dd><p>
5908                   Enable or disable all empty zones.  By default, they
5909                   are enabled.
5910                 </p></dd>
5911 <dt><span class="term"><span><strong class="command">disable-empty-zone</strong></span></span></dt>
5912 <dd><p>
5913                   Disable individual empty zones.  By default, none are
5914                   disabled.  This option can be specified multiple times.
5915                 </p></dd>
5916 </dl></div>
5917 </div>
5918 <div class="sect3" lang="en">
5919 <div class="titlepage"><div><div><h4 class="title">
5920 <a name="acache"></a>Additional Section Caching</h4></div></div></div>
5921 <p>
5922             The additional section cache, also called <span><strong class="command">acache</strong></span>,
5923             is an internal cache to improve the response performance of BIND 9.
5924             When additional section caching is enabled, BIND 9 will
5925             cache an internal short-cut to the additional section content for
5926             each answer RR.
5927             Note that <span><strong class="command">acache</strong></span> is an internal caching
5928             mechanism of BIND 9, and is not related to the DNS caching
5929             server function.
5930           </p>
5931 <p>
5932             Additional section caching does not change the
5933             response content (except the RRsets ordering of the additional
5934             section, see below), but can improve the response performance
5935             significantly.
5936             It is particularly effective when BIND 9 acts as an authoritative
5937             server for a zone that has many delegations with many glue RRs.
5938           </p>
5939 <p>
5940             In order to obtain the maximum performance improvement
5941             from additional section caching, setting
5942             <span><strong class="command">additional-from-cache</strong></span>
5943             to <span><strong class="command">no</strong></span> is recommended, since the current
5944             implementation of <span><strong class="command">acache</strong></span>
5945             does not short-cut of additional section information from the
5946             DNS cache data.
5947           </p>
5948 <p>
5949             One obvious disadvantage of <span><strong class="command">acache</strong></span> is
5950             that it requires much more
5951             memory for the internal cached data.
5952             Thus, if the response performance does not matter and memory
5953             consumption is much more critical, the
5954             <span><strong class="command">acache</strong></span> mechanism can be
5955             disabled by setting <span><strong class="command">acache-enable</strong></span> to
5956             <span><strong class="command">no</strong></span>.
5957             It is also possible to specify the upper limit of memory
5958             consumption
5959             for acache by using <span><strong class="command">max-acache-size</strong></span>.
5960           </p>
5961 <p>
5962             Additional section caching also has a minor effect on the
5963             RRset ordering in the additional section.
5964             Without <span><strong class="command">acache</strong></span>,
5965             <span><strong class="command">cyclic</strong></span> order is effective for the additional
5966             section as well as the answer and authority sections.
5967             However, additional section caching fixes the ordering when it
5968             first caches an RRset for the additional section, and the same
5969             ordering will be kept in succeeding responses, regardless of the
5970             setting of <span><strong class="command">rrset-order</strong></span>.
5971             The effect of this should be minor, however, since an
5972             RRset in the additional section
5973             typically only contains a small number of RRs (and in many cases
5974             it only contains a single RR), in which case the
5975             ordering does not matter much.
5976           </p>
5977 <p>
5978             The following is a summary of options related to
5979             <span><strong class="command">acache</strong></span>.
5980           </p>
5981 <div class="variablelist"><dl>
5982 <dt><span class="term"><span><strong class="command">acache-enable</strong></span></span></dt>
5983 <dd><p>
5984                   If <span><strong class="command">yes</strong></span>, additional section caching is
5985                   enabled.  The default value is <span><strong class="command">no</strong></span>.
5986                 </p></dd>
5987 <dt><span class="term"><span><strong class="command">acache-cleaning-interval</strong></span></span></dt>
5988 <dd><p>
5989                   The server will remove stale cache entries, based on an LRU
5990                   based
5991                   algorithm, every <span><strong class="command">acache-cleaning-interval</strong></span> minutes.
5992                   The default is 60 minutes.
5993                   If set to 0, no periodic cleaning will occur.
5994                 </p></dd>
5995 <dt><span class="term"><span><strong class="command">max-acache-size</strong></span></span></dt>
5996 <dd><p>
5997                   The maximum amount of memory in bytes to use for the server's acache.
5998                   When the amount of data in the acache reaches this limit,
5999                   the server
6000                   will clean more aggressively so that the limit is not
6001                   exceeded.
6002                   In a server with multiple views, the limit applies
6003                   separately to the
6004                   acache of each view.
6005                   The default is <code class="literal">16M</code>.
6006                 </p></dd>
6007 </dl></div>
6008 </div>
6009 <div class="sect3" lang="en">
6010 <div class="titlepage"><div><div><h4 class="title">
6011 <a name="id2588923"></a>Content Filtering</h4></div></div></div>
6012 <p>
6013             <acronym class="acronym">BIND</acronym> 9 provides the ability to filter
6014             out DNS responses from external DNS servers containing
6015             certain types of data in the answer section.
6016             Specifically, it can reject address (A or AAAA) records if
6017             the corresponding IPv4 or IPv6 addresses match the given
6018             <code class="varname">address_match_list</code> of the
6019             <span><strong class="command">deny-answer-addresses</strong></span> option.
6020             It can also reject CNAME or DNAME records if the "alias"
6021             name (i.e., the CNAME alias or the substituted query name
6022             due to DNAME) matches the
6023             given <code class="varname">namelist</code> of the
6024             <span><strong class="command">deny-answer-aliases</strong></span> option, where
6025             "match" means the alias name is a subdomain of one of
6026             the <code class="varname">name_list</code> elements.
6027             If the optional <code class="varname">namelist</code> is specified
6028             with <span><strong class="command">except-from</strong></span>, records whose query name
6029             matches the list will be accepted regardless of the filter
6030             setting.
6031             Likewise, if the alias name is a subdomain of the
6032             corresponding zone, the <span><strong class="command">deny-answer-aliases</strong></span>
6033             filter will not apply;
6034             for example, even if "example.com" is specified for
6035             <span><strong class="command">deny-answer-aliases</strong></span>,
6036           </p>
6037 <pre class="programlisting">www.example.com. CNAME xxx.example.com.</pre>
6038 <p>
6039             returned by an "example.com" server will be accepted.
6040           </p>
6041 <p>
6042             In the <code class="varname">address_match_list</code> of the
6043             <span><strong class="command">deny-answer-addresses</strong></span> option, only
6044             <code class="varname">ip_addr</code>
6045             and <code class="varname">ip_prefix</code>
6046             are meaningful;
6047             any <code class="varname">key_id</code> will be silently ignored.
6048           </p>
6049 <p>
6050             If a response message is rejected due to the filtering,
6051             the entire message is discarded without being cached, and
6052             a SERVFAIL error will be returned to the client.
6053           </p>
6054 <p>
6055             This filtering is intended to prevent "DNS rebinding attacks," in
6056             which an attacker, in response to a query for a domain name the
6057             attacker controls, returns an IP address within your own network or
6058             an alias name within your own domain.
6059             A naive web browser or script could then serve as an
6060             unintended proxy, allowing the attacker
6061             to get access to an internal node of your local network
6062             that couldn't be externally accessed otherwise.
6063             See the paper available at
6064             <a href="http://portal.acm.org/citation.cfm?id=1315245.1315298" target="_top">
6065             http://portal.acm.org/citation.cfm?id=1315245.1315298
6066             </a>
6067             for more details about the attacks.
6068           </p>
6069 <p>
6070             For example, if you own a domain named "example.net" and
6071             your internal network uses an IPv4 prefix 192.0.2.0/24,
6072             you might specify the following rules:
6073           </p>
6074 <pre class="programlisting">deny-answer-addresses { 192.0.2.0/24; } except-from { "example.net"; };
6075 deny-answer-aliases { "example.net"; };
6076 </pre>
6077 <p>
6078             If an external attacker lets a web browser in your local
6079             network look up an IPv4 address of "attacker.example.com",
6080             the attacker's DNS server would return a response like this:
6081           </p>
6082 <pre class="programlisting">attacker.example.com. A 192.0.2.1</pre>
6083 <p>
6084             in the answer section.
6085             Since the rdata of this record (the IPv4 address) matches
6086             the specified prefix 192.0.2.0/24, this response will be
6087             ignored.
6088           </p>
6089 <p>
6090             On the other hand, if the browser looks up a legitimate
6091             internal web server "www.example.net" and the
6092             following response is returned to
6093             the <acronym class="acronym">BIND</acronym> 9 server
6094           </p>
6095 <pre class="programlisting">www.example.net. A 192.0.2.2</pre>
6096 <p>
6097             it will be accepted since the owner name "www.example.net"
6098             matches the <span><strong class="command">except-from</strong></span> element,
6099             "example.net".
6100           </p>
6101 <p>
6102             Note that this is not really an attack on the DNS per se.
6103             In fact, there is nothing wrong for an "external" name to
6104             be mapped to your "internal" IP address or domain name
6105             from the DNS point of view.
6106             It might actually be provided for a legitimate purpose,
6107             such as for debugging.
6108             As long as the mapping is provided by the correct owner,
6109             it is not possible or does not make sense to detect
6110             whether the intent of the mapping is legitimate or not
6111             within the DNS.
6112             The "rebinding" attack must primarily be protected at the
6113             application that uses the DNS.
6114             For a large site, however, it may be difficult to protect
6115             all possible applications at once.
6116             This filtering feature is provided only to help such an
6117             operational environment;
6118             it is generally discouraged to turn it on unless you are
6119             very sure you have no other choice and the attack is a
6120             real threat for your applications.
6121           </p>
6122 <p>
6123             Care should be particularly taken if you want to use this
6124             option for addresses within 127.0.0.0/8.
6125             These addresses are obviously "internal", but many
6126             applications conventionally rely on a DNS mapping from
6127             some name to such an address.
6128             Filtering out DNS records containing this address
6129             spuriously can break such applications.
6130           </p>
6131 </div>
6132 <div class="sect3" lang="en">
6133 <div class="titlepage"><div><div><h4 class="title">
6134 <a name="id2589049"></a>Response Policy Zone (RPZ) Rewriting</h4></div></div></div>
6135 <p>
6136             <acronym class="acronym">BIND</acronym> 9 includes a limited
6137             mechanism to modify DNS responses for requests
6138             analogous to email anti-spam DNS blacklists.
6139             Responses can be changed to deny the existence of domains (NXDOMAIN),
6140             deny the existence of IP addresses for domains (NODATA),
6141             or contain other IP addresses or data.
6142           </p>
6143 <p>
6144             Response policy zones are named in the
6145             <span><strong class="command">response-policy</strong></span> option for the view or among the
6146             global options if there is no response-policy option for the view.
6147             RPZs are ordinary DNS zones containing RRsets
6148             that can be queried normally if allowed.
6149             It is usually best to restrict those queries with something like
6150             <span><strong class="command">allow-query { localhost; };</strong></span>.
6151           </p>
6152 <p>
6153             Four policy triggers are encoded in RPZ records, QNAME, IP, NSIP,
6154             and NSDNAME.
6155             QNAME RPZ records triggered by query names of requests and targets
6156             of CNAME records resolved to generate the response.
6157             The owner name of a QNAME RPZ record is the query name relativized
6158             to the RPZ.
6159           </p>
6160 <p>
6161             The second kind of RPZ trigger is an IP address in an A and AAAA
6162             record in the ANSWER section of a response.
6163             IP address triggers are encoded in records that have owner names
6164             that are subdomains of <strong class="userinput"><code>rpz-ip</code></strong> relativized
6165             to the RPZ origin name and encode an IP address or address block.
6166             IPv4 trigger addresses are represented as
6167             <strong class="userinput"><code>prefixlength.B4.B3.B2.B1.rpz-ip</code></strong>.
6168             The prefix length must be between 1 and 32.
6169             All four bytes, B4, B3, B2, and B1, must be present.
6170             B4 is the decimal value of the least significant byte of the
6171             IPv4 address as in IN-ADDR.ARPA.
6172             IPv6 addresses are encoded in a format similar to the standard
6173             IPv6 text representation,
6174             <strong class="userinput"><code>prefixlength.W8.W7.W6.W5.W4.W3.W2.W1.rpz-ip</code></strong>.
6175             Each of W8,...,W1 is a one to four digit hexadecimal number
6176             representing 16 bits of the IPv6 address as in the standard text
6177             representation of IPv6 addresses, but reversed as in IN-ADDR.ARPA.
6178             All 8 words must be present except when consecutive
6179             zero words are replaced with <strong class="userinput"><code>.zz.</code></strong>
6180             analogous to double colons (::) in standard IPv6 text encodings.
6181             The prefix length must be between 1 and 128.
6182           </p>
6183 <p>
6184             NSDNAME triggers match names of authoritative servers
6185             for the query name, a parent of the query name, a CNAME for
6186             query name, or a parent of a CNAME.
6187             They are encoded as subdomains of
6188             <strong class="userinput"><code>rpz-nsdomain</code></strong> relativized
6189             to the RPZ origin name.
6190             NSIP triggers match IP addresses in A and
6191             AAAA RRsets for domains that can be checked against NSDNAME
6192             policy records.
6193             NSIP triggers are encoded like IP triggers except as subdomains of
6194             <strong class="userinput"><code>rpz-nsip</code></strong>.
6195             NSDNAME and NSIP triggers are checked only for names with at
6196             least <span><strong class="command">min-ns-dots</strong></span> dots.
6197             The default value of <span><strong class="command">min-ns-dots</strong></span> is 1 to
6198             exclude top level domains.
6199           </p>
6200 <p>
6201             The query response is checked against all RPZs, so
6202             two or more policy records can be triggered by a response.
6203             Because DNS responses can be rewritten according to at most one
6204             policy record, a single record encoding an action (other than
6205             <span><strong class="command">DISABLED</strong></span> actions) must be chosen.
6206             Triggers or the records that encode them are chosen in
6207             the following order:
6208             </p>
6209 <div class="itemizedlist"><ul type="disc">
6210 <li>Choose the triggered record in the zone that appears
6211                 first in the response-policy option.
6212               </li>
6213 <li>Prefer QNAME to IP to NSDNAME to NSIP triggers
6214                 in a single zone.
6215               </li>
6216 <li>Among NSDNAME triggers, prefer the
6217                 trigger that matches the smallest name under the DNSSEC ordering.
6218               </li>
6219 <li>Among IP or NSIP triggers, prefer the trigger
6220                 with the longest prefix.
6221               </li>
6222 <li>Among triggers with the same prefix length,
6223                 prefer the IP or NSIP trigger that matches
6224                 the smallest IP address.
6225               </li>
6226 </ul></div>
6227 <p>
6228           </p>
6229 <p>
6230             When the processing of a response is restarted to resolve
6231             DNAME or CNAME records and a policy record set has
6232             not been triggered,
6233             all RPZs are again consulted for the DNAME or CNAME names
6234             and addresses.
6235           </p>
6236 <p>
6237             RPZ record sets are sets of any types of DNS record except
6238             DNAME or DNSSEC that encode actions or responses to queries.
6239             </p>
6240 <div class="itemizedlist"><ul type="disc">
6241 <li>The <span><strong class="command">NXDOMAIN</strong></span> response is encoded
6242                 by a CNAME whose target is the root domain (.)
6243               </li>
6244 <li>A CNAME whose target is the wildcard top-level
6245                 domain (*.) specifies the <span><strong class="command">NODATA</strong></span> action,
6246                 which rewrites the response to NODATA or ANCOUNT=1.
6247               </li>
6248 <li>The <span><strong class="command">Local Data</strong></span> action is
6249                 represented by a set ordinary DNS records that are used
6250                 to answer queries.  Queries for record types not the
6251                 set are answered with NODATA.
6252
6253                 A special form of local data is a CNAME whose target is a
6254                 wildcard such as *.example.com.
6255                 It is used as if were an ordinary CNAME after the astrisk (*)
6256                 has been replaced with the query name.
6257                 The purpose for this special form is query logging in the
6258                 walled garden's authority DNS server.
6259               </li>
6260 <li>The <span><strong class="command">PASSTHRU</strong></span> policy is specified
6261                 by a CNAME whose target is <span><strong class="command">rpz-passthru.</strong></span>
6262                 It causes the response to not be rewritten
6263                 and is most often used to "poke holes" in policies for
6264                 CIDR blocks.
6265                 (A CNAME whose target is the variable part of its owner name
6266                 is an obsolete specification of the PASSTHRU policy.)
6267               </li>
6268 </ul></div>
6269 <p>
6270           </p>
6271 <p>
6272             The actions specified in an RPZ can be overridden with a
6273             <span><strong class="command">policy</strong></span> clause in the
6274             <span><strong class="command">response-policy</strong></span> option.
6275             An organization using an RPZ provided by another organization might
6276             use this mechanism to redirect domains to its own walled garden.
6277             </p>
6278 <div class="itemizedlist"><ul type="disc">
6279 <li>
6280 <span><strong class="command">GIVEN</strong></span> says "do not override but
6281                 perform the action specified in the zone."
6282               </li>
6283 <li>
6284 <span><strong class="command">DISABLED</strong></span> causes policy records to do
6285                 nothing but log what they might have done.
6286                 The response to the DNS query will be written according to
6287                 any triggered policy records that are not disabled.
6288                 Disabled policy zones should appear first,
6289                 because they will often not be logged
6290                 if a higher precedence trigger is found first.
6291               </li>
6292 <li>
6293 <span><strong class="command">PASSTHRU</strong></span> causes all policy records
6294                 to act as if they were CNAME records with targets the variable
6295                 part of their owner name.  They protect the response from
6296                 being changed.
6297               </li>
6298 <li>
6299 <span><strong class="command">NXDOMAIN</strong></span> causes all RPZ records
6300                 to specify NXDOMAIN policies.
6301               </li>
6302 <li>
6303 <span><strong class="command">NODATA</strong></span> overrides with the
6304                 NODATA policy
6305               </li>
6306 <li>
6307 <span><strong class="command">CNAME domain</strong></span> causes all RPZ
6308                 policy records to act as if they were "cname domain" records.
6309               </li>
6310 </ul></div>
6311 <p>
6312           </p>
6313 <p>
6314             By default, the actions encoded in an RPZ are applied
6315             only to queries that ask for recursion (RD=1).
6316             That default can be changed for a single RPZ or all RPZs in a view
6317             with a <span><strong class="command">recursive-only no</strong></span> clause.
6318             This feature is useful for serving the same zone files
6319             both inside and outside an RFC 1918 cloud and using RPZ to
6320             delete answers that would otherwise contain RFC 1918 values
6321             on the externally visible name server or view.
6322           </p>
6323 <p>
6324             Also by default, RPZ actions are applied only to DNS requests that
6325             either do not request DNSSEC metadata (DO=0) or when no DNSSEC
6326             records are available for request name in the original zone (not
6327             the response policy zone).
6328             This default can be changed for all RPZs in a view with a
6329             <span><strong class="command">break-dnssec yes</strong></span> clause.
6330             In that case, RPZ actions are applied regardless of DNSSEC.
6331             The name of the clause option reflects the fact that results
6332             rewritten by RPZ actions cannot verify.
6333           </p>
6334 <p>
6335             The TTL of a record modified by RPZ policies is set from the
6336             TTL of the relevant record in policy zone.  It is then limited
6337             to a maximum value.
6338             The <span><strong class="command">max-policy-ttl</strong></span> clause changes that
6339             maximum from its default of 5.
6340           </p>
6341 <p>
6342             For example, you might use this option statement
6343           </p>
6344 <pre class="programlisting">    response-policy { zone "badlist"; };</pre>
6345 <p>
6346             and this zone statement
6347           </p>
6348 <pre class="programlisting">    zone "badlist" {type master; file "master/badlist"; allow-query {none;}; };</pre>
6349 <p>
6350             with this zone file
6351           </p>
6352 <pre class="programlisting">$TTL 1H
6353 @                       SOA LOCALHOST. named-mgr.example.com (1 1h 15m 30d 2h)
6354                         NS  LOCALHOST.
6355
6356 ; QNAME policy records.  There are no periods (.) after the owner names.
6357 nxdomain.domain.com     CNAME   .               ; NXDOMAIN policy
6358 nodata.domain.com       CNAME   *.              ; NODATA policy
6359 bad.domain.com          A       10.0.0.1        ; redirect to a walled garden
6360                         AAAA    2001:2::1
6361
6362 ; do not rewrite (PASSTHRU) OK.DOMAIN.COM
6363 ok.domain.com           CNAME   rpz-passthru.
6364
6365 bzone.domain.com        CNAME   garden.example.com.
6366
6367 ; redirect x.bzone.domain.com to x.bzone.domain.com.garden.example.com
6368 *.bzone.domain.com      CNAME   *.garden.example.com.
6369
6370
6371 ; IP policy records that rewrite all answers for 127/8 except 127.0.0.1
6372 8.0.0.0.127.rpz-ip      CNAME   .
6373 32.1.0.0.127.rpz-ip     CNAME   rpz-passthru.
6374
6375 ; NSDNAME and NSIP policy records
6376 ns.domain.com.rpz-nsdname   CNAME   .
6377 48.zz.2.2001.rpz-nsip       CNAME   .
6378 </pre>
6379 <p>
6380             RPZ can affect server performance.
6381             Each configured response policy zone requires the server to
6382             perform one to four additional database lookups before a
6383             query can be answered.
6384             For example, a DNS server with four policy zones, each with all
6385             four kinds of response triggers, QNAME, IP, NSIP, and
6386             NSDNAME, requires a total of 17 times as many database
6387             lookups as a similar DNS server with no response policy zones.
6388             A <acronym class="acronym">BIND9</acronym> server with adequate memory and one
6389             response policy zone with QNAME and IP triggers might achieve a
6390             maximum queries-per-second rate about 20% lower.
6391             A server with four response policy zones with QNAME and IP
6392             triggers might have a maximum QPS rate about 50% lower.
6393           </p>
6394 <p>
6395             Responses rewritten by RPZ are counted in the
6396             <span><strong class="command">RPZRewrites</strong></span> statistics.
6397           </p>
6398 </div>
6399 <div class="sect3" lang="en">
6400 <div class="titlepage"><div><div><h4 class="title">
6401 <a name="id2589479"></a>Response Rate Limiting</h4></div></div></div>
6402 <p>
6403             This feature is only available when <acronym class="acronym">BIND</acronym> 9
6404             is compiled with the <strong class="userinput"><code>--enable-rrl</code></strong>
6405             option on the "configure" command line.
6406           </p>
6407 <p>
6408             Excessive almost identical UDP <span class="emphasis"><em>responses</em></span>
6409             can be controlled by configuring a
6410             <span><strong class="command">rate-limit</strong></span> clause in an
6411             <span><strong class="command">options</strong></span> or <span><strong class="command">view</strong></span> statement.
6412             This mechanism keeps authoritative BIND 9 from being used
6413             in amplifying reflection denial of service (DoS) attacks.
6414             Short truncated (TC=1) responses can be sent to provide
6415             rate-limited responses to legitimate clients within
6416             a range of forged, attacked IP addresses.
6417             Legitimate clients react to dropped or truncated response
6418             by retrying with UDP or with TCP respectively.
6419           </p>
6420 <p>
6421             This mechanism is intended for authoritative DNS servers.
6422             It can be used on recursive servers but can slow
6423             applications such as SMTP servers (mail receivers) and
6424             HTTP clients (web browsers) that repeatedly request the
6425             same domains.
6426             When possible, closing "open" recursive servers is better.
6427           </p>
6428 <p>
6429             Response rate limiting uses a "credit" or "token bucket" scheme.
6430             Each combination of identical response and client
6431             has a conceptual account that earns a specified number
6432             of credits every second.
6433             A prospective response debits its account by one.
6434             Responses are dropped or truncated
6435             while the account is negative.
6436             Responses are tracked within a rolling window of time
6437             which defaults to 15 seconds, but can be configured with
6438             the <span><strong class="command">window</strong></span> option to any value from
6439             1 to 3600 seconds (1 hour).
6440             The account cannot become more positive than
6441             the per-second limit
6442             or more negative than <span><strong class="command">window</strong></span>
6443             times the per-second limit.
6444             When the specified number of credits for a class of
6445             responses is set to 0, those responses are not rate limited.
6446           </p>
6447 <p>
6448             The notions of "identical response" and "DNS client"
6449             for rate limiting are not simplistic.
6450             All responses to an address block are counted as if to a
6451             single client.
6452             The prefix lengths of addresses blocks are
6453             specified with <span><strong class="command">ipv4-prefix-length</strong></span> (default 24)
6454             and <span><strong class="command">ipv6-prefix-length</strong></span> (default 56).
6455           </p>
6456 <p>
6457             All non-empty responses for a valid domain name (qname)
6458             and record type (qtype) are identical and have a limit specified
6459             with <span><strong class="command">responses-per-second</strong></span>
6460             (default 0 or no limit).
6461             All empty (NODATA) responses for a valid domain,
6462             regardless of query type, are identical.
6463             Responses in the NODATA class are limited by
6464             <span><strong class="command">nodata-per-second</strong></span>
6465             (default <span><strong class="command">responses-per-second</strong></span>).
6466             Requests for any and all undefined subdomains of a given
6467             valid domain result in NXDOMAIN errors, and are identical
6468             regardless of query type.
6469             They are limited by <span><strong class="command">nxdomain-per-second</strong></span>
6470             (default <span><strong class="command">responses-per-second</strong></span>).
6471             This controls some attacks using random names, but
6472             can be relaxed or turned off (set to 0)
6473             on servers that expect many legitimate
6474             NXDOMAIN responses, such as from anti-spam blacklists.
6475             Referrals or delegations to the server of a given
6476             domain are identical and are limited by
6477             <span><strong class="command">referrals-per-second</strong></span>
6478             (default <span><strong class="command">responses-per-second</strong></span>).
6479           </p>
6480 <p>
6481             Responses generated from local wildcards are counted and limited
6482             as if they were for the parent domain name.
6483             This controls flooding using random.wild.example.com.
6484           </p>
6485 <p>
6486             All requests that result in DNS errors other
6487             than NXDOMAIN, such as SERVFAIL and FORMERR, are identical
6488             regardless of requested name (qname) or record type (qtype).
6489             This controls attacks using invalid requests or distant,
6490             broken authoritative servers.
6491             By default the limit on errors is the same as the
6492             <span><strong class="command">responses-per-second</strong></span> value,
6493             but it can be set separately with
6494             <span><strong class="command">errors-per-second</strong></span>.
6495           </p>
6496 <p>
6497             Many attacks using DNS involve UDP requests with forged source
6498             addresses.
6499             Rate limiting prevents the use of BIND 9 to flood a network
6500             with responses to requests with forged source addresses,
6501             but could let a third party block responses to legitimate requests.
6502             There is a mechanism that can answer some legitimate
6503             requests from a client whose address is being forged in a flood.
6504             Setting <span><strong class="command">slip</strong></span> to 2 (its default) causes every
6505             other UDP request to be answered with a small truncated (TC=1)
6506             response.
6507             The small size and reduced frequency, and so lack of
6508             amplification, of "slipped" responses make them unattractive
6509             for reflection DoS attacks.
6510             <span><strong class="command">slip</strong></span> must be between 0 and 10.
6511             A value of 0 does not "slip":
6512             no truncated responses are sent due to rate limiting,
6513             all responses are dropped.
6514             A value of 1 causes every response to slip;
6515             values between 2 and 10 cause every n'th response to slip.
6516             Some error responses including REFUSED and SERVFAIL
6517             cannot be replaced with truncated responses and are instead
6518             leaked at the <span><strong class="command">slip</strong></span> rate.
6519           </p>
6520 <p>
6521             (NOTE: Dropped responses from an authoritative server may
6522             reduce the difficulty of a third party successfully forging
6523             a response to a recursive resolver. The best security
6524             against forged responses is for authoritative operators
6525             to sign their zones using DNSSEC and for resolver operators
6526             to validate the responses. When this is not an option,
6527             operators who are more concerned with response integrity
6528             than with flood mitigation may consider setting
6529             <span><strong class="command">slip</strong></span> to 1, causing all rate-limited
6530             responses to be truncated rather than dropped.  This reduces
6531             the effectiveness of rate-limiting against reflection attacks.)
6532           </p>
6533 <p>
6534             When the approximate query per second rate exceeds
6535             the <span><strong class="command">qps-scale</strong></span> value,
6536             then the <span><strong class="command">responses-per-second</strong></span>,
6537             <span><strong class="command">errors-per-second</strong></span>,
6538             <span><strong class="command">nxdomains-per-second</strong></span> and
6539             <span><strong class="command">all-per-second</strong></span> values are reduced by the
6540             ratio of the current rate to the <span><strong class="command">qps-scale</strong></span> value.
6541             This feature can tighten defenses during attacks.
6542             For example, with
6543             <span><strong class="command">qps-scale 250; responses-per-second 20;</strong></span> and
6544             a total query rate of 1000 queries/second for all queries from
6545             all DNS clients including via TCP,
6546             then the effective responses/second limit changes to
6547             (250/1000)*20 or 5.
6548             Responses sent via TCP are not limited
6549             but are counted to compute the query per second rate.
6550           </p>
6551 <p>
6552             Communities of DNS clients can be given their own parameters or no
6553             rate limiting by putting
6554             <span><strong class="command">rate-limit</strong></span> statements in <span><strong class="command">view</strong></span>
6555             statements instead of the global <span><strong class="command">option</strong></span>
6556             statement.
6557             A <span><strong class="command">rate-limit</strong></span> statement in a view replaces,
6558             rather than supplementing, a <span><strong class="command">rate-limit</strong></span>
6559             statement among the main options.
6560             DNS clients within a view can be exempted from rate limits
6561             with the <span><strong class="command">exempt-clients</strong></span> clause.
6562           </p>
6563 <p>
6564             UDP responses of all kinds can be limited with the
6565             <span><strong class="command">all-per-second</strong></span> phrase.
6566             This rate limiting is unlike the rate limiting provided by
6567             <span><strong class="command">responses-per-second</strong></span>,
6568             <span><strong class="command">errors-per-second</strong></span>, and
6569             <span><strong class="command">nxdomains-per-second</strong></span> on a DNS server
6570             which are often invisible to the victim of a DNS reflection attack.
6571             Unless the forged requests of the attack are the same as the
6572             legitimate requests of the victim, the victim's requests are
6573             not affected.
6574             Responses affected by an <span><strong class="command">all-per-second</strong></span> limit
6575             are always dropped; the <span><strong class="command">slip</strong></span> value has no
6576             effect.
6577             An <span><strong class="command">all-per-second</strong></span> limit should be
6578             at least 4 times as large as the other limits,
6579             because single DNS clients often send bursts of legitimate
6580             requests.
6581             For example, the receipt of a single mail message can prompt
6582             requests from an SMTP server for NS, PTR, A, and AAAA records
6583             as the incoming SMTP/TCP/IP connection is considered.
6584             The SMTP server can need additional NS, A, AAAA, MX, TXT, and SPF
6585             records as it considers the STMP <span><strong class="command">Mail From</strong></span>
6586             command.
6587             Web browsers often repeatedly resolve the same names that
6588             are repeated in HTML &lt;IMG&gt; tags in a page.
6589             <span><strong class="command">All-per-second</strong></span> is similar to the
6590             rate limiting offered by firewalls but often inferior.
6591             Attacks that justify ignoring the
6592             contents of DNS responses are likely to be attacks on the
6593             DNS server itself.
6594             They usually should be discarded before the DNS server
6595             spends resources making TCP connections or parsing DNS requests,
6596             but that rate limiting must be done before the
6597             DNS server sees the requests.
6598           </p>
6599 <p>
6600             The maximum size of the table used to track requests and
6601             rate limit responses is set with <span><strong class="command">max-table-size</strong></span>.
6602             Each entry in the table is between 40 and 80 bytes.
6603             The table needs approximately as many entries as the number
6604             of requests received per second.
6605             The default is 20,000.
6606             To reduce the cold start of growing the table,
6607             <span><strong class="command">min-table-size</strong></span> (default 500)
6608             can set the minimum table size.
6609             Enable <span><strong class="command">rate-limit</strong></span> category logging to monitor
6610             expansions of the table and inform
6611             choices for the initial and maximum table size.
6612           </p>
6613 <p>
6614             Use <span><strong class="command">log-only yes</strong></span> to test rate limiting parameters
6615             without actually dropping any requests.
6616           </p>
6617 <p>
6618             Responses dropped by rate limits are included in the
6619             <span><strong class="command">RateDropped</strong></span> and <span><strong class="command">QryDropped</strong></span>
6620             statistics.
6621             Responses that truncated by rate limits are included in
6622             <span><strong class="command">RateSlipped</strong></span> and <span><strong class="command">RespTruncated</strong></span>.
6623           </p>
6624 </div>
6625 </div>
6626 <div class="sect2" lang="en">
6627 <div class="titlepage"><div><div><h3 class="title">
6628 <a name="server_statement_grammar"></a><span><strong class="command">server</strong></span> Statement Grammar</h3></div></div></div>
6629 <pre class="programlisting"><span><strong class="command">server</strong></span> <em class="replaceable"><code>ip_addr[/prefixlen]</code></em> {
6630     [<span class="optional"> bogus <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6631     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6632     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6633     [<span class="optional"> request-nsid <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6634     [<span class="optional"> edns <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6635     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
6636     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
6637     [<span class="optional"> transfers <em class="replaceable"><code>number</code></em> ; </span>]
6638     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em> ; ]</span>]
6639     [<span class="optional"> keys { <em class="replaceable"><code>key_id</code></em> }; </span>]
6640     [<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>]
6641     [<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>]
6642     [<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>]
6643     [<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>]
6644     [<span class="optional"> query-source [<span class="optional"> address ( <em class="replaceable"><code>ip_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
6645                   [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]; </span>]
6646     [<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>]
6647                      [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]; </span>]
6648     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6649     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
6650     [<span class="optional"> queryport-pool-updateinterval <em class="replaceable"><code>number</code></em>; </span>]
6651 };
6652 </pre>
6653 </div>
6654 <div class="sect2" lang="en">
6655 <div class="titlepage"><div><div><h3 class="title">
6656 <a name="server_statement_definition_and_usage"></a><span><strong class="command">server</strong></span> Statement Definition and
6657             Usage</h3></div></div></div>
6658 <p>
6659             The <span><strong class="command">server</strong></span> statement defines
6660             characteristics
6661             to be associated with a remote name server.  If a prefix length is
6662             specified, then a range of servers is covered.  Only the most
6663             specific
6664             server clause applies regardless of the order in
6665             <code class="filename">named.conf</code>.
6666           </p>
6667 <p>
6668             The <span><strong class="command">server</strong></span> statement can occur at
6669             the top level of the
6670             configuration file or inside a <span><strong class="command">view</strong></span>
6671             statement.
6672             If a <span><strong class="command">view</strong></span> statement contains
6673             one or more <span><strong class="command">server</strong></span> statements, only
6674             those
6675             apply to the view and any top-level ones are ignored.
6676             If a view contains no <span><strong class="command">server</strong></span>
6677             statements,
6678             any top-level <span><strong class="command">server</strong></span> statements are
6679             used as
6680             defaults.
6681           </p>
6682 <p>
6683             If you discover that a remote server is giving out bad data,
6684             marking it as bogus will prevent further queries to it. The
6685             default
6686             value of <span><strong class="command">bogus</strong></span> is <span><strong class="command">no</strong></span>.
6687           </p>
6688 <p>
6689             The <span><strong class="command">provide-ixfr</strong></span> clause determines
6690             whether
6691             the local server, acting as master, will respond with an
6692             incremental
6693             zone transfer when the given remote server, a slave, requests it.
6694             If set to <span><strong class="command">yes</strong></span>, incremental transfer
6695             will be provided
6696             whenever possible. If set to <span><strong class="command">no</strong></span>,
6697             all transfers
6698             to the remote server will be non-incremental. If not set, the
6699             value
6700             of the <span><strong class="command">provide-ixfr</strong></span> option in the
6701             view or
6702             global options block is used as a default.
6703           </p>
6704 <p>
6705             The <span><strong class="command">request-ixfr</strong></span> clause determines
6706             whether
6707             the local server, acting as a slave, will request incremental zone
6708             transfers from the given remote server, a master. If not set, the
6709             value of the <span><strong class="command">request-ixfr</strong></span> option in
6710             the view or global options block is used as a default. It may
6711             also be set in the zone block and, if set there, it will
6712             override the global or view setting for that zone.
6713           </p>
6714 <p>
6715             IXFR requests to servers that do not support IXFR will
6716             automatically
6717             fall back to AXFR.  Therefore, there is no need to manually list
6718             which servers support IXFR and which ones do not; the global
6719             default
6720             of <span><strong class="command">yes</strong></span> should always work.
6721             The purpose of the <span><strong class="command">provide-ixfr</strong></span> and
6722             <span><strong class="command">request-ixfr</strong></span> clauses is
6723             to make it possible to disable the use of IXFR even when both
6724             master
6725             and slave claim to support it, for example if one of the servers
6726             is buggy and crashes or corrupts data when IXFR is used.
6727           </p>
6728 <p>
6729             The <span><strong class="command">edns</strong></span> clause determines whether
6730             the local server will attempt to use EDNS when communicating
6731             with the remote server.  The default is <span><strong class="command">yes</strong></span>.
6732           </p>
6733 <p>
6734             The <span><strong class="command">edns-udp-size</strong></span> option sets the EDNS UDP size
6735             that is advertised by <span><strong class="command">named</strong></span> when querying the remote server.
6736             Valid values are 512 to 4096 bytes (values outside this range will be
6737             silently adjusted).  This option is useful when you wish to
6738             advertises a different value to this server than the value you
6739             advertise globally, for example, when there is a firewall at the
6740             remote site that is blocking large replies.
6741           </p>
6742 <p>
6743             The <span><strong class="command">max-udp-size</strong></span> option sets the
6744             maximum EDNS UDP message size <span><strong class="command">named</strong></span> will send.  Valid
6745             values are 512 to 4096 bytes (values outside this range will
6746             be silently adjusted).  This option is useful when you
6747             know that there is a firewall that is blocking large
6748             replies from <span><strong class="command">named</strong></span>.
6749           </p>
6750 <p>
6751             The server supports two zone transfer methods. The first, <span><strong class="command">one-answer</strong></span>,
6752             uses one DNS message per resource record transferred. <span><strong class="command">many-answers</strong></span> packs
6753             as many resource records as possible into a message. <span><strong class="command">many-answers</strong></span> is
6754             more efficient, but is only known to be understood by <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
6755             8.x, and patched versions of <acronym class="acronym">BIND</acronym>
6756             4.9.5. You can specify which method
6757             to use for a server with the <span><strong class="command">transfer-format</strong></span> option.
6758             If <span><strong class="command">transfer-format</strong></span> is not
6759             specified, the <span><strong class="command">transfer-format</strong></span>
6760             specified
6761             by the <span><strong class="command">options</strong></span> statement will be
6762             used.
6763           </p>
6764 <p><span><strong class="command">transfers</strong></span>
6765             is used to limit the number of concurrent inbound zone
6766             transfers from the specified server. If no
6767             <span><strong class="command">transfers</strong></span> clause is specified, the
6768             limit is set according to the
6769             <span><strong class="command">transfers-per-ns</strong></span> option.
6770           </p>
6771 <p>
6772             The <span><strong class="command">keys</strong></span> clause identifies a
6773             <span><strong class="command">key_id</strong></span> defined by the <span><strong class="command">key</strong></span> statement,
6774             to be used for transaction security (TSIG, <a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
6775             when talking to the remote server.
6776             When a request is sent to the remote server, a request signature
6777             will be generated using the key specified here and appended to the
6778             message. A request originating from the remote server is not
6779             required
6780             to be signed by this key.
6781           </p>
6782 <p>
6783             Only a single key per server is currently supported.
6784           </p>
6785 <p>
6786             The <span><strong class="command">transfer-source</strong></span> and
6787             <span><strong class="command">transfer-source-v6</strong></span> clauses specify
6788             the IPv4 and IPv6 source
6789             address to be used for zone transfer with the remote server,
6790             respectively.
6791             For an IPv4 remote server, only <span><strong class="command">transfer-source</strong></span> can
6792             be specified.
6793             Similarly, for an IPv6 remote server, only
6794             <span><strong class="command">transfer-source-v6</strong></span> can be
6795             specified.
6796             For more details, see the description of
6797             <span><strong class="command">transfer-source</strong></span> and
6798             <span><strong class="command">transfer-source-v6</strong></span> in
6799             <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
6800           </p>
6801 <p>
6802             The <span><strong class="command">notify-source</strong></span> and
6803             <span><strong class="command">notify-source-v6</strong></span> clauses specify the
6804             IPv4 and IPv6 source address to be used for notify
6805             messages sent to remote servers, respectively.  For an
6806             IPv4 remote server, only <span><strong class="command">notify-source</strong></span>
6807             can be specified.  Similarly, for an IPv6 remote server,
6808             only <span><strong class="command">notify-source-v6</strong></span> can be specified.
6809           </p>
6810 <p>
6811             The <span><strong class="command">query-source</strong></span> and
6812             <span><strong class="command">query-source-v6</strong></span> clauses specify the
6813             IPv4 and IPv6 source address to be used for queries
6814             sent to remote servers, respectively.  For an IPv4
6815             remote server, only <span><strong class="command">query-source</strong></span> can
6816             be specified.  Similarly, for an IPv6 remote server,
6817             only <span><strong class="command">query-source-v6</strong></span> can be specified.
6818           </p>
6819 <p>
6820             The <span><strong class="command">request-nsid</strong></span> clause determines
6821             whether the local server will add a NSID EDNS option
6822             to requests sent to the server.  This overrides
6823             <span><strong class="command">request-nsid</strong></span> set at the view or
6824             option level.
6825           </p>
6826 </div>
6827 <div class="sect2" lang="en">
6828 <div class="titlepage"><div><div><h3 class="title">
6829 <a name="statschannels"></a><span><strong class="command">statistics-channels</strong></span> Statement Grammar</h3></div></div></div>
6830 <pre class="programlisting"><span><strong class="command">statistics-channels</strong></span> {
6831    [ inet ( ip_addr | * ) [ port ip_port ]
6832    [ allow { <em class="replaceable"><code> address_match_list </code></em> } ]; ]
6833    [ inet ...; ]
6834 };
6835 </pre>
6836 </div>
6837 <div class="sect2" lang="en">
6838 <div class="titlepage"><div><div><h3 class="title">
6839 <a name="id2590832"></a><span><strong class="command">statistics-channels</strong></span> Statement Definition and
6840             Usage</h3></div></div></div>
6841 <p>
6842           The <span><strong class="command">statistics-channels</strong></span> statement
6843           declares communication channels to be used by system
6844           administrators to get access to statistics information of
6845           the name server.
6846         </p>
6847 <p>
6848           This statement intends to be flexible to support multiple
6849           communication protocols in the future, but currently only
6850           HTTP access is supported.
6851           It requires that BIND 9 be compiled with libxml2;
6852           the <span><strong class="command">statistics-channels</strong></span> statement is
6853           still accepted even if it is built without the library,
6854           but any HTTP access will fail with an error.
6855         </p>
6856 <p>
6857           An <span><strong class="command">inet</strong></span> control channel is a TCP socket
6858           listening at the specified <span><strong class="command">ip_port</strong></span> on the
6859           specified <span><strong class="command">ip_addr</strong></span>, which can be an IPv4 or IPv6
6860           address.  An <span><strong class="command">ip_addr</strong></span> of <code class="literal">*</code> (asterisk) is
6861           interpreted as the IPv4 wildcard address; connections will be
6862           accepted on any of the system's IPv4 addresses.
6863           To listen on the IPv6 wildcard address,
6864           use an <span><strong class="command">ip_addr</strong></span> of <code class="literal">::</code>.
6865         </p>
6866 <p>
6867           If no port is specified, port 80 is used for HTTP channels.
6868           The asterisk "<code class="literal">*</code>" cannot be used for
6869           <span><strong class="command">ip_port</strong></span>.
6870         </p>
6871 <p>
6872           The attempt of opening a statistics channel is
6873           restricted by the optional <span><strong class="command">allow</strong></span> clause.
6874           Connections to the statistics channel are permitted based on the
6875           <span><strong class="command">address_match_list</strong></span>.
6876           If no <span><strong class="command">allow</strong></span> clause is present,
6877           <span><strong class="command">named</strong></span> accepts connection
6878           attempts from any address; since the statistics may
6879           contain sensitive internal information, it is highly
6880           recommended to restrict the source of connection requests
6881           appropriately.
6882         </p>
6883 <p>
6884           If no <span><strong class="command">statistics-channels</strong></span> statement is present,
6885           <span><strong class="command">named</strong></span> will not open any communication channels.
6886         </p>
6887 <p>
6888           If the statistics channel is configured to listen on 127.0.0.1
6889           port 8888, then the statistics are accessible in XML format at
6890           <a href="http://127.0.0.1:8888/" target="_top">http://127.0.0.1:8888/</a> or
6891           <a href="http://127.0.0.1:8888/xml" target="_top">http://127.0.0.1:8888/xml</a>. A CSS file is
6892           included which can format the XML statistics into tables
6893           when viewed with a stylesheet-capable browser.  When
6894           <acronym class="acronym">BIND</acronym> 9 is configured with --enable-newstats,
6895           a new XML schema is used (version 3) which adds additional
6896           zone statistics and uses a flatter tree for more efficient
6897           parsing.  The stylesheet included uses the Google Charts API
6898           to render data into into charts and graphs when using a
6899           javascript-capable browser.
6900         </p>
6901 <p>
6902           Applications that depend on a particular XML schema
6903           can request
6904           <a href="http://127.0.0.1:8888/xml/v2" target="_top">http://127.0.0.1:8888/xml/v2</a> for version 2
6905           of the statistics XML schema or
6906           <a href="http://127.0.0.1:8888/xml/v3" target="_top">http://127.0.0.1:8888/xml/v3</a> for version 3.
6907           If the requested schema is supported by the server, then
6908           it will respond; if not, it will return a "page not found"
6909           error.
6910         </p>
6911 </div>
6912 <div class="sect2" lang="en">
6913 <div class="titlepage"><div><div><h3 class="title">
6914 <a name="trusted-keys"></a><span><strong class="command">trusted-keys</strong></span> Statement Grammar</h3></div></div></div>
6915 <pre class="programlisting"><span><strong class="command">trusted-keys</strong></span> {
6916     <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> ;
6917     [<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>]
6918 };
6919 </pre>
6920 </div>
6921 <div class="sect2" lang="en">
6922 <div class="titlepage"><div><div><h3 class="title">
6923 <a name="id2591139"></a><span><strong class="command">trusted-keys</strong></span> Statement Definition
6924             and Usage</h3></div></div></div>
6925 <p>
6926             The <span><strong class="command">trusted-keys</strong></span> statement defines
6927             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
6928             public key for a non-authoritative zone is known, but
6929             cannot be securely obtained through DNS, either because
6930             it is the DNS root zone or because its parent zone is
6931             unsigned.  Once a key has been configured as a trusted
6932             key, it is treated as if it had been validated and
6933             proven secure. The resolver attempts DNSSEC validation
6934             on all DNS data in subdomains of a security root.
6935           </p>
6936 <p>
6937             All keys (and corresponding zones) listed in
6938             <span><strong class="command">trusted-keys</strong></span> are deemed to exist regardless
6939             of what parent zones say.  Similarly for all keys listed in
6940             <span><strong class="command">trusted-keys</strong></span> only those keys are
6941             used to validate the DNSKEY RRset.  The parent's DS RRset
6942             will not be used.
6943           </p>
6944 <p>
6945             The <span><strong class="command">trusted-keys</strong></span> statement can contain
6946             multiple key entries, each consisting of the key's
6947             domain name, flags, protocol, algorithm, and the Base-64
6948             representation of the key data.
6949             Spaces, tabs, newlines and carriage returns are ignored
6950             in the key data, so the configuration may be split up into
6951             multiple lines.
6952           </p>
6953 <p>
6954             <span><strong class="command">trusted-keys</strong></span> may be set at the top level
6955             of <code class="filename">named.conf</code> or within a view.  If it is
6956             set in both places, they are additive: keys defined at the top
6957             level are inherited by all views, but keys defined in a view
6958             are only used within that view.
6959           </p>
6960 </div>
6961 <div class="sect2" lang="en">
6962 <div class="titlepage"><div><div><h3 class="title">
6963 <a name="id2591186"></a><span><strong class="command">managed-keys</strong></span> Statement Grammar</h3></div></div></div>
6964 <pre class="programlisting"><span><strong class="command">managed-keys</strong></span> {
6965     <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> ;
6966     [<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>]
6967 };
6968 </pre>
6969 </div>
6970 <div class="sect2" lang="en">
6971 <div class="titlepage"><div><div><h3 class="title">
6972 <a name="managed-keys"></a><span><strong class="command">managed-keys</strong></span> Statement Definition
6973             and Usage</h3></div></div></div>
6974 <p>
6975             The <span><strong class="command">managed-keys</strong></span> statement, like
6976             <span><strong class="command">trusted-keys</strong></span>, defines DNSSEC
6977             security roots.  The difference is that
6978             <span><strong class="command">managed-keys</strong></span> can be kept up to date
6979             automatically, without intervention from the resolver
6980             operator.
6981           </p>
6982 <p>
6983             Suppose, for example, that a zone's key-signing
6984             key was compromised, and the zone owner had to revoke and
6985             replace the key.  A resolver which had the old key in a
6986             <span><strong class="command">trusted-keys</strong></span> statement would be
6987             unable to validate this zone any longer; it would
6988             reply with a SERVFAIL response code.  This would
6989             continue until the resolver operator had updated the
6990             <span><strong class="command">trusted-keys</strong></span> statement with the new key.
6991           </p>
6992 <p>
6993             If, however, the zone were listed in a
6994             <span><strong class="command">managed-keys</strong></span> statement instead, then the
6995             zone owner could add a "stand-by" key to the zone in advance.
6996             <span><strong class="command">named</strong></span> would store the stand-by key, and
6997             when the original key was revoked, <span><strong class="command">named</strong></span>
6998             would be able to transition smoothly to the new key.  It would
6999             also recognize that the old key had been revoked, and cease
7000             using that key to validate answers, minimizing the damage that
7001             the compromised key could do.
7002           </p>
7003 <p>
7004             A <span><strong class="command">managed-keys</strong></span> statement contains a list of
7005             the keys to be managed, along with information about how the
7006             keys are to be initialized for the first time.  The only
7007             initialization method currently supported (as of
7008             <acronym class="acronym">BIND</acronym> 9.7.0) is <code class="literal">initial-key</code>.
7009             This means the <span><strong class="command">managed-keys</strong></span> statement must
7010             contain a copy of the initializing key.  (Future releases may
7011             allow keys to be initialized by other methods, eliminating this
7012             requirement.)
7013           </p>
7014 <p>
7015             Consequently, a <span><strong class="command">managed-keys</strong></span> statement
7016             appears similar to a <span><strong class="command">trusted-keys</strong></span>, differing
7017             in the presence of the second field, containing the keyword
7018             <code class="literal">initial-key</code>.  The difference is, whereas the
7019             keys listed in a <span><strong class="command">trusted-keys</strong></span> continue to be
7020             trusted until they are removed from
7021             <code class="filename">named.conf</code>, an initializing key listed
7022             in a <span><strong class="command">managed-keys</strong></span> statement is only trusted
7023             <span class="emphasis"><em>once</em></span>: for as long as it takes to load the
7024             managed key database and start the RFC 5011 key maintenance
7025             process.
7026           </p>
7027 <p>
7028             The first time <span><strong class="command">named</strong></span> runs with a managed key
7029             configured in <code class="filename">named.conf</code>, it fetches the
7030             DNSKEY RRset directly from the zone apex, and validates it
7031             using the key specified in the <span><strong class="command">managed-keys</strong></span>
7032             statement.  If the DNSKEY RRset is validly signed, then it is
7033             used as the basis for a new managed keys database.
7034           </p>
7035 <p>
7036             From that point on, whenever <span><strong class="command">named</strong></span> runs, it
7037             sees the <span><strong class="command">managed-keys</strong></span> statement, checks to
7038             make sure RFC 5011 key maintenance has already been initialized
7039             for the specified domain, and if so, it simply moves on.  The
7040             key specified in the <span><strong class="command">managed-keys</strong></span> is not
7041             used to validate answers; it has been superseded by the key or
7042             keys stored in the managed keys database.
7043           </p>
7044 <p>
7045             The next time <span><strong class="command">named</strong></span> runs after a name
7046             has been <span class="emphasis"><em>removed</em></span> from the
7047             <span><strong class="command">managed-keys</strong></span> statement, the corresponding
7048             zone will be removed from the managed keys database,
7049             and RFC 5011 key maintenance will no longer be used for that
7050             domain.
7051           </p>
7052 <p>
7053             <span><strong class="command">named</strong></span> only maintains a single managed keys
7054             database; consequently, unlike <span><strong class="command">trusted-keys</strong></span>,
7055             <span><strong class="command">managed-keys</strong></span> may only be set at the top
7056             level of <code class="filename">named.conf</code>, not within a view.
7057           </p>
7058 <p>
7059             In the current implementation, the managed keys database is
7060             stored as a master-format zone file called
7061             <code class="filename">managed-keys.bind</code>.  When the key database
7062             is changed, the zone is updated.  As with any other dynamic
7063             zone, changes will be written into a journal file,
7064             <code class="filename">managed-keys.bind.jnl</code>.  They are committed
7065             to the master file as soon as possible afterward; in the case
7066             of the managed key database, this will usually occur within 30
7067             seconds.  So, whenever <span><strong class="command">named</strong></span> is using
7068             automatic key maintenance, those two files can be expected to
7069             exist in the working directory.  (For this reason among others,
7070             the working directory should be always be writable by
7071             <span><strong class="command">named</strong></span>.)
7072           </p>
7073 <p>
7074             If the <span><strong class="command">dnssec-validation</strong></span> option is
7075             set to <strong class="userinput"><code>auto</code></strong>, <span><strong class="command">named</strong></span>
7076             will automatically initialize a managed key for the
7077             root zone.  Similarly, if the <span><strong class="command">dnssec-lookaside</strong></span>
7078             option is set to <strong class="userinput"><code>auto</code></strong>,
7079             <span><strong class="command">named</strong></span> will automatically initialize
7080             a managed key for the zone <code class="literal">dlv.isc.org</code>.
7081             In both cases, the key that is used to initialize the key
7082             maintenance process is built into <span><strong class="command">named</strong></span>,
7083             and can be overridden from <span><strong class="command">bindkeys-file</strong></span>.
7084           </p>
7085 </div>
7086 <div class="sect2" lang="en">
7087 <div class="titlepage"><div><div><h3 class="title">
7088 <a name="view_statement_grammar"></a><span><strong class="command">view</strong></span> Statement Grammar</h3></div></div></div>
7089 <pre class="programlisting"><span><strong class="command">view</strong></span> <em class="replaceable"><code>view_name</code></em>
7090       [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7091       match-clients { <em class="replaceable"><code>address_match_list</code></em> };
7092       match-destinations { <em class="replaceable"><code>address_match_list</code></em> };
7093       match-recursive-only <em class="replaceable"><code>yes_or_no</code></em> ;
7094       [<span class="optional"> <em class="replaceable"><code>view_option</code></em>; ...</span>]
7095       [<span class="optional"> <em class="replaceable"><code>zone_statement</code></em>; ...</span>]
7096 };
7097 </pre>
7098 </div>
7099 <div class="sect2" lang="en">
7100 <div class="titlepage"><div><div><h3 class="title">
7101 <a name="id2591553"></a><span><strong class="command">view</strong></span> Statement Definition and Usage</h3></div></div></div>
7102 <p>
7103             The <span><strong class="command">view</strong></span> statement is a powerful
7104             feature
7105             of <acronym class="acronym">BIND</acronym> 9 that lets a name server
7106             answer a DNS query differently
7107             depending on who is asking. It is particularly useful for
7108             implementing
7109             split DNS setups without having to run multiple servers.
7110           </p>
7111 <p>
7112             Each <span><strong class="command">view</strong></span> statement defines a view
7113             of the
7114             DNS namespace that will be seen by a subset of clients.  A client
7115             matches
7116             a view if its source IP address matches the
7117             <code class="varname">address_match_list</code> of the view's
7118             <span><strong class="command">match-clients</strong></span> clause and its
7119             destination IP address matches
7120             the <code class="varname">address_match_list</code> of the
7121             view's
7122             <span><strong class="command">match-destinations</strong></span> clause.  If not
7123             specified, both
7124             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
7125             default to matching all addresses.  In addition to checking IP
7126             addresses
7127             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
7128             can also take <span><strong class="command">keys</strong></span> which provide an
7129             mechanism for the
7130             client to select the view.  A view can also be specified
7131             as <span><strong class="command">match-recursive-only</strong></span>, which
7132             means that only recursive
7133             requests from matching clients will match that view.
7134             The order of the <span><strong class="command">view</strong></span> statements is
7135             significant &#8212;
7136             a client request will be resolved in the context of the first
7137             <span><strong class="command">view</strong></span> that it matches.
7138           </p>
7139 <p>
7140             Zones defined within a <span><strong class="command">view</strong></span>
7141             statement will
7142             only be accessible to clients that match the <span><strong class="command">view</strong></span>.
7143             By defining a zone of the same name in multiple views, different
7144             zone data can be given to different clients, for example,
7145             "internal"
7146             and "external" clients in a split DNS setup.
7147           </p>
7148 <p>
7149             Many of the options given in the <span><strong class="command">options</strong></span> statement
7150             can also be used within a <span><strong class="command">view</strong></span>
7151             statement, and then
7152             apply only when resolving queries with that view.  When no
7153             view-specific
7154             value is given, the value in the <span><strong class="command">options</strong></span> statement
7155             is used as a default.  Also, zone options can have default values
7156             specified
7157             in the <span><strong class="command">view</strong></span> statement; these
7158             view-specific defaults
7159             take precedence over those in the <span><strong class="command">options</strong></span> statement.
7160           </p>
7161 <p>
7162             Views are class specific.  If no class is given, class IN
7163             is assumed.  Note that all non-IN views must contain a hint zone,
7164             since only the IN class has compiled-in default hints.
7165           </p>
7166 <p>
7167             If there are no <span><strong class="command">view</strong></span> statements in
7168             the config
7169             file, a default view that matches any client is automatically
7170             created
7171             in class IN. Any <span><strong class="command">zone</strong></span> statements
7172             specified on
7173             the top level of the configuration file are considered to be part
7174             of
7175             this default view, and the <span><strong class="command">options</strong></span>
7176             statement will
7177             apply to the default view. If any explicit <span><strong class="command">view</strong></span>
7178             statements are present, all <span><strong class="command">zone</strong></span>
7179             statements must
7180             occur inside <span><strong class="command">view</strong></span> statements.
7181           </p>
7182 <p>
7183             Here is an example of a typical split DNS setup implemented
7184             using <span><strong class="command">view</strong></span> statements:
7185           </p>
7186 <pre class="programlisting">view "internal" {
7187       // This should match our internal networks.
7188       match-clients { 10.0.0.0/8; };
7189
7190       // Provide recursive service to internal
7191       // clients only.
7192       recursion yes;
7193
7194       // Provide a complete view of the example.com
7195       // zone including addresses of internal hosts.
7196       zone "example.com" {
7197             type master;
7198             file "example-internal.db";
7199       };
7200 };
7201
7202 view "external" {
7203       // Match all clients not matched by the
7204       // previous view.
7205       match-clients { any; };
7206
7207       // Refuse recursive service to external clients.
7208       recursion no;
7209
7210       // Provide a restricted view of the example.com
7211       // zone containing only publicly accessible hosts.
7212       zone "example.com" {
7213            type master;
7214            file "example-external.db";
7215       };
7216 };
7217 </pre>
7218 </div>
7219 <div class="sect2" lang="en">
7220 <div class="titlepage"><div><div><h3 class="title">
7221 <a name="zone_statement_grammar"></a><span><strong class="command">zone</strong></span>
7222             Statement Grammar</h3></div></div></div>
7223 <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>] {
7224     type master;
7225     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7226     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7227     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7228     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7229     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7230     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7231     [<span class="optional"> dnssec-loadkeys-interval <em class="replaceable"><code>number</code></em>; </span>]
7232     [<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>]
7233     [<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>] ;
7234                   [<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>]
7235     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
7236     [<span class="optional"> check-mx (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
7237     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7238     [<span class="optional"> check-spf ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
7239     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7240     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
7241     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
7242     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
7243     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
7244     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
7245     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
7246     [<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>]
7247     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
7248     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7249     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
7250     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7251     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7252     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
7253     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
7254     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
7255     [<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>]
7256     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
7257     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7258     [<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>]
7259     [<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>]
7260     [<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>]
7261     [<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>]
7262     [<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>]
7263     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
7264     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
7265     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
7266     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
7267     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7268     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7269     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7270     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7271     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
7272     [<span class="optional"> auto-dnssec <code class="constant">allow</code>|<code class="constant">maintain</code>|<code class="constant">off</code>; </span>]
7273     [<span class="optional"> inline-signing <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7274     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7275     [<span class="optional"> serial-update-method <code class="constant">increment</code>|<code class="constant">unixtime</code>; </span>]
7276 };
7277
7278 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7279     type slave;
7280     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7281     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7282     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7283     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7284     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7285     [<span class="optional"> dnssec-update-mode ( <em class="replaceable"><code>maintain</code></em> | <em class="replaceable"><code>no-resign</code></em> ); </span>]
7286     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7287     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7288     [<span class="optional"> dnssec-loadkeys-interval <em class="replaceable"><code>number</code></em>; </span>]
7289     [<span class="optional"> dnssec-secure-to-insecure <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7290     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7291     [<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>
7292                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
7293                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
7294     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
7295     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
7296     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
7297     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
7298     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
7299     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
7300     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
7301     [<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>]
7302     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
7303     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7304     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
7305     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7306     [<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>
7307                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
7308                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
7309     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
7310     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
7311     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
7312     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
7313     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
7314     [<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>]
7315     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
7316     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7317     [<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>]
7318     [<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>]
7319     [<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>]
7320     [<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>]
7321     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
7322                              [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7323     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7324     [<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>]
7325     [<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>]
7326     [<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>]
7327     [<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>]
7328     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
7329     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
7330     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
7331     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
7332     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7333     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7334     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7335     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7336     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
7337     [<span class="optional"> auto-dnssec <code class="constant">allow</code>|<code class="constant">maintain</code>|<code class="constant">off</code>; </span>]
7338     [<span class="optional"> inline-signing <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7339     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7340     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7341 };
7342
7343 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7344     type hint;
7345     file <em class="replaceable"><code>string</code></em> ;
7346     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7347     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>] // Not Implemented.
7348 };
7349
7350 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7351     type stub;
7352     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7353     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7354     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
7355     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
7356     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7357     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
7358     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
7359     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
7360     [<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>]
7361     [<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>
7362                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
7363                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
7364     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
7365     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
7366     [<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>]
7367     [<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>]
7368     [<span class="optional"> transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
7369                          [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7370     [<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>]
7371     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
7372                             [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
7373     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
7374     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7375     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
7376     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7377     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
7378     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7379     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
7380     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7381 };
7382
7383 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7384     type static-stub;
7385     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7386     [<span class="optional"> server-addresses { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> ; ... </span>] }; </span>]
7387     [<span class="optional"> server-names { [<span class="optional"> <em class="replaceable"><code>namelist</code></em> </span>] }; </span>]
7388     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7389 };
7390
7391 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7392     type forward;
7393     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
7394     [<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>]
7395     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
7396 };
7397
7398 zone <em class="replaceable"><code>"."</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7399     type redirect;
7400     file <em class="replaceable"><code>string</code></em> ;
7401     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
7402     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
7403 };
7404
7405 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
7406     type delegation-only;
7407 };
7408
7409 </pre>
7410 </div>
7411 <div class="sect2" lang="en">
7412 <div class="titlepage"><div><div><h3 class="title">
7413 <a name="id2593398"></a><span><strong class="command">zone</strong></span> Statement Definition and Usage</h3></div></div></div>
7414 <div class="sect3" lang="en">
7415 <div class="titlepage"><div><div><h4 class="title">
7416 <a name="id2593405"></a>Zone Types</h4></div></div></div>
7417 <div class="informaltable"><table border="1">
7418 <colgroup>
7419 <col>
7420 <col>
7421 </colgroup>
7422 <tbody>
7423 <tr>
7424 <td>
7425                       <p>
7426                         <code class="varname">master</code>
7427                       </p>
7428                     </td>
7429 <td>
7430                       <p>
7431                         The server has a master copy of the data
7432                         for the zone and will be able to provide authoritative
7433                         answers for
7434                         it.
7435                       </p>
7436                     </td>
7437 </tr>
7438 <tr>
7439 <td>
7440                       <p>
7441                         <code class="varname">slave</code>
7442                       </p>
7443                     </td>
7444 <td>
7445                       <p>
7446                         A slave zone is a replica of a master
7447                         zone. The <span><strong class="command">masters</strong></span> list
7448                         specifies one or more IP addresses
7449                         of master servers that the slave contacts to update
7450                         its copy of the zone.
7451                         Masters list elements can also be names of other
7452                         masters lists.
7453                         By default, transfers are made from port 53 on the
7454                         servers; this can
7455                         be changed for all servers by specifying a port number
7456                         before the
7457                         list of IP addresses, or on a per-server basis after
7458                         the IP address.
7459                         Authentication to the master can also be done with
7460                         per-server TSIG keys.
7461                         If a file is specified, then the
7462                         replica will be written to this file whenever the zone
7463                         is changed,
7464                         and reloaded from this file on a server restart. Use
7465                         of a file is
7466                         recommended, since it often speeds server startup and
7467                         eliminates
7468                         a needless waste of bandwidth. Note that for large
7469                         numbers (in the
7470                         tens or hundreds of thousands) of zones per server, it
7471                         is best to
7472                         use a two-level naming scheme for zone filenames. For
7473                         example,
7474                         a slave server for the zone <code class="literal">example.com</code> might place
7475                         the zone contents into a file called
7476                         <code class="filename">ex/example.com</code> where <code class="filename">ex/</code> is
7477                         just the first two letters of the zone name. (Most
7478                         operating systems
7479                         behave very slowly if you put 100000 files into
7480                         a single directory.)
7481                       </p>
7482                     </td>
7483 </tr>
7484 <tr>
7485 <td>
7486                       <p>
7487                         <code class="varname">stub</code>
7488                       </p>
7489                     </td>
7490 <td>
7491                       <p>
7492                         A stub zone is similar to a slave zone,
7493                         except that it replicates only the NS records of a
7494                         master zone instead
7495                         of the entire zone. Stub zones are not a standard part
7496                         of the DNS;
7497                         they are a feature specific to the <acronym class="acronym">BIND</acronym> implementation.
7498                       </p>
7499
7500                       <p>
7501                         Stub zones can be used to eliminate the need for glue
7502                         NS record
7503                         in a parent zone at the expense of maintaining a stub
7504                         zone entry and
7505                         a set of name server addresses in <code class="filename">named.conf</code>.
7506                         This usage is not recommended for new configurations,
7507                         and BIND 9
7508                         supports it only in a limited way.
7509                         In <acronym class="acronym">BIND</acronym> 4/8, zone
7510                         transfers of a parent zone
7511                         included the NS records from stub children of that
7512                         zone. This meant
7513                         that, in some cases, users could get away with
7514                         configuring child stubs
7515                         only in the master server for the parent zone. <acronym class="acronym">BIND</acronym>
7516                         9 never mixes together zone data from different zones
7517                         in this
7518                         way. Therefore, if a <acronym class="acronym">BIND</acronym> 9 master serving a parent
7519                         zone has child stub zones configured, all the slave
7520                         servers for the
7521                         parent zone also need to have the same child stub
7522                         zones
7523                         configured.
7524                       </p>
7525
7526                       <p>
7527                         Stub zones can also be used as a way of forcing the
7528                         resolution
7529                         of a given domain to use a particular set of
7530                         authoritative servers.
7531                         For example, the caching name servers on a private
7532                         network using
7533                         RFC1918 addressing may be configured with stub zones
7534                         for
7535                         <code class="literal">10.in-addr.arpa</code>
7536                         to use a set of internal name servers as the
7537                         authoritative
7538                         servers for that domain.
7539                       </p>
7540                     </td>
7541 </tr>
7542 <tr>
7543 <td>
7544                       <p>
7545                         <code class="varname">static-stub</code>
7546                       </p>
7547                     </td>
7548 <td>
7549                       <p>
7550                         A static-stub zone is similar to a stub zone
7551                         with the following exceptions:
7552                         the zone data is statically configured, rather
7553                         than transferred from a master server;
7554                         when recursion is necessary for a query that
7555                         matches a static-stub zone, the locally
7556                         configured data (nameserver names and glue addresses)
7557                         is always used even if different authoritative
7558                         information is cached.
7559                       </p>
7560                       <p>
7561                         Zone data is configured via the
7562                         <span><strong class="command">server-addresses</strong></span> and
7563                         <span><strong class="command">server-names</strong></span> zone options.
7564                       </p>
7565                       <p>
7566                         The zone data is maintained in the form of NS
7567                         and (if necessary) glue A or AAAA RRs
7568                         internally, which can be seen by dumping zone
7569                         databases by <span><strong class="command">rndc dumpdb -all</strong></span>.
7570                         The configured RRs are considered local configuration
7571                         parameters rather than public data.
7572                         Non recursive queries (i.e., those with the RD
7573                         bit off) to a static-stub zone are therefore
7574                         prohibited and will be responded with REFUSED.
7575                       </p>
7576                       <p>
7577                         Since the data is statically configured, no
7578                         zone maintenance action takes place for a static-stub
7579                         zone.
7580                         For example, there is no periodic refresh
7581                         attempt, and an incoming notify message
7582                         will be rejected with an rcode of NOTAUTH.
7583                       </p>
7584                       <p>
7585                         Each static-stub zone is configured with
7586                         internally generated NS and (if necessary)
7587                         glue A or AAAA RRs
7588                       </p>
7589                     </td>
7590 </tr>
7591 <tr>
7592 <td>
7593                       <p>
7594                         <code class="varname">forward</code>
7595                       </p>
7596                     </td>
7597 <td>
7598                       <p>
7599                         A "forward zone" is a way to configure
7600                         forwarding on a per-domain basis.  A <span><strong class="command">zone</strong></span> statement
7601                         of type <span><strong class="command">forward</strong></span> can
7602                         contain a <span><strong class="command">forward</strong></span>
7603                         and/or <span><strong class="command">forwarders</strong></span>
7604                         statement,
7605                         which will apply to queries within the domain given by
7606                         the zone
7607                         name. If no <span><strong class="command">forwarders</strong></span>
7608                         statement is present or
7609                         an empty list for <span><strong class="command">forwarders</strong></span> is given, then no
7610                         forwarding will be done for the domain, canceling the
7611                         effects of
7612                         any forwarders in the <span><strong class="command">options</strong></span> statement. Thus
7613                         if you want to use this type of zone to change the
7614                         behavior of the
7615                         global <span><strong class="command">forward</strong></span> option
7616                         (that is, "forward first"
7617                         to, then "forward only", or vice versa, but want to
7618                         use the same
7619                         servers as set globally) you need to re-specify the
7620                         global forwarders.
7621                       </p>
7622                     </td>
7623 </tr>
7624 <tr>
7625 <td>
7626                       <p>
7627                         <code class="varname">hint</code>
7628                       </p>
7629                     </td>
7630 <td>
7631                       <p>
7632                         The initial set of root name servers is
7633                         specified using a "hint zone". When the server starts
7634                         up, it uses
7635                         the root hints to find a root name server and get the
7636                         most recent
7637                         list of root name servers. If no hint zone is
7638                         specified for class
7639                         IN, the server uses a compiled-in default set of root
7640                         servers hints.
7641                         Classes other than IN have no built-in defaults hints.
7642                       </p>
7643                     </td>
7644 </tr>
7645 <tr>
7646 <td>
7647                       <p>
7648                         <code class="varname">redirect</code>
7649                       </p>
7650                     </td>
7651 <td>
7652                       <p>
7653                         Redirect zones are used to provide answers to
7654                         queries when normal resolution would result in
7655                         NXDOMAIN being returned.
7656                         Only one redirect zone is supported
7657                         per view.  <span><strong class="command">allow-query</strong></span> can be
7658                         used to restrict which clients see these answers.
7659                       </p>
7660                       <p>
7661                         If the client has requested DNSSEC records (DO=1) and
7662                         the NXDOMAIN response is signed then no substitution
7663                         will occur.
7664                       </p>
7665                       <p>
7666                         To redirect all NXDOMAIN responses to
7667                         100.100.100.2 and
7668                         2001:ffff:ffff::100.100.100.2, one would
7669                         configure a type redirect zone named ".",
7670                         with the zone file containing wildcard records
7671                         that point to the desired addresses:
7672                         <code class="literal">"*. IN A 100.100.100.2"</code>
7673                         and
7674                         <code class="literal">"*. IN AAAA 2001:ffff:ffff::100.100.100.2"</code>.
7675                       </p>
7676                       <p>
7677                         To redirect all Spanish names (under .ES) one
7678                         would use similar entries but with the names
7679                         "*.ES." instead of "*.".  To redirect all
7680                         commercial Spanish names (under COM.ES) one
7681                         would use wildcard entries called "*.COM.ES.".
7682                       </p>
7683                       <p>
7684                         Note that the redirect zone supports all
7685                         possible types; it is not limited to A and
7686                         AAAA records.
7687                       </p>
7688                       <p>
7689                         Because redirect zones are not referenced
7690                         directly by name, they are not kept in the
7691                         zone lookup table with normal master and slave
7692                         zones. Consequently, it is not currently possible
7693                         to use
7694                         <span><strong class="command">rndc reload
7695                                 <em class="replaceable"><code>zonename</code></em></strong></span>
7696                         to reload a redirect zone.  However, when using
7697                         <span><strong class="command">rndc reload</strong></span> without specifying
7698                         a zone name, redirect zones will be reloaded along
7699                         with other zones.
7700                       </p>
7701                     </td>
7702 </tr>
7703 <tr>
7704 <td>
7705                       <p>
7706                         <code class="varname">delegation-only</code>
7707                       </p>
7708                     </td>
7709 <td>
7710                       <p>
7711                         This is used to enforce the delegation-only
7712                         status of infrastructure zones (e.g. COM,
7713                         NET, ORG).  Any answer that is received
7714                         without an explicit or implicit delegation
7715                         in the authority section will be treated
7716                         as NXDOMAIN.  This does not apply to the
7717                         zone apex.  This should not be applied to
7718                         leaf zones.
7719                       </p>
7720                       <p>
7721                         <code class="varname">delegation-only</code> has no
7722                         effect on answers received from forwarders.
7723                       </p>
7724                       <p>
7725                         See caveats in <a href="Bv9ARM.ch06.html#root_delegation_only"><span><strong class="command">root-delegation-only</strong></span></a>.
7726                       </p>
7727                     </td>
7728 </tr>
7729 </tbody>
7730 </table></div>
7731 </div>
7732 <div class="sect3" lang="en">
7733 <div class="titlepage"><div><div><h4 class="title">
7734 <a name="id2594150"></a>Class</h4></div></div></div>
7735 <p>
7736               The zone's name may optionally be followed by a class. If
7737               a class is not specified, class <code class="literal">IN</code> (for <code class="varname">Internet</code>),
7738               is assumed. This is correct for the vast majority of cases.
7739             </p>
7740 <p>
7741               The <code class="literal">hesiod</code> class is
7742               named for an information service from MIT's Project Athena. It
7743               is
7744               used to share information about various systems databases, such
7745               as users, groups, printers and so on. The keyword
7746               <code class="literal">HS</code> is
7747               a synonym for hesiod.
7748             </p>
7749 <p>
7750               Another MIT development is Chaosnet, a LAN protocol created
7751               in the mid-1970s. Zone data for it can be specified with the <code class="literal">CHAOS</code> class.
7752             </p>
7753 </div>
7754 <div class="sect3" lang="en">
7755 <div class="titlepage"><div><div><h4 class="title">
7756 <a name="id2594183"></a>Zone Options</h4></div></div></div>
7757 <div class="variablelist"><dl>
7758 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
7759 <dd><p>
7760                     See the description of
7761                     <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>.
7762                   </p></dd>
7763 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
7764 <dd><p>
7765                     See the description of
7766                     <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>.
7767                   </p></dd>
7768 <dt><span class="term"><span><strong class="command">allow-query-on</strong></span></span></dt>
7769 <dd><p>
7770                     See the description of
7771                     <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>.
7772                   </p></dd>
7773 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
7774 <dd><p>
7775                     See the description of <span><strong class="command">allow-transfer</strong></span>
7776                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
7777                   </p></dd>
7778 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
7779 <dd><p>
7780                     See the description of <span><strong class="command">allow-update</strong></span>
7781                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
7782                   </p></dd>
7783 <dt><span class="term"><span><strong class="command">update-policy</strong></span></span></dt>
7784 <dd><p>
7785                     Specifies a "Simple Secure Update" policy. See
7786                     <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>.
7787                   </p></dd>
7788 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
7789 <dd><p>
7790                     See the description of <span><strong class="command">allow-update-forwarding</strong></span>
7791                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
7792                   </p></dd>
7793 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
7794 <dd><p>
7795                     Only meaningful if <span><strong class="command">notify</strong></span>
7796                     is
7797                     active for this zone. The set of machines that will
7798                     receive a
7799                     <code class="literal">DNS NOTIFY</code> message
7800                     for this zone is made up of all the listed name servers
7801                     (other than
7802                     the primary master) for the zone plus any IP addresses
7803                     specified
7804                     with <span><strong class="command">also-notify</strong></span>. A port
7805                     may be specified
7806                     with each <span><strong class="command">also-notify</strong></span>
7807                     address to send the notify
7808                     messages to a port other than the default of 53.
7809                     A TSIG key may also be specified to cause the
7810                     <code class="literal">NOTIFY</code> to be signed by the
7811                     given key.
7812                     <span><strong class="command">also-notify</strong></span> is not
7813                     meaningful for stub zones.
7814                     The default is the empty list.
7815                   </p></dd>
7816 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
7817 <dd><p>
7818                     This option is used to restrict the character set and
7819                     syntax of
7820                     certain domain names in master files and/or DNS responses
7821                     received from the
7822                     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>
7823                     zones the default is <span><strong class="command">warn</strong></span>.
7824                     It is not implemented for <span><strong class="command">hint</strong></span> zones.
7825                   </p></dd>
7826 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
7827 <dd><p>
7828                     See the description of
7829                     <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>.
7830                   </p></dd>
7831 <dt><span class="term"><span><strong class="command">check-spf</strong></span></span></dt>
7832 <dd><p>
7833                     See the description of
7834                     <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>.
7835                   </p></dd>
7836 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
7837 <dd><p>
7838                     See the description of
7839                     <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>.
7840                   </p></dd>
7841 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
7842 <dd><p>
7843                     See the description of
7844                     <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>.
7845                   </p></dd>
7846 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
7847 <dd><p>
7848                     See the description of
7849                     <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>.
7850                   </p></dd>
7851 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
7852 <dd><p>
7853                     See the description of
7854                     <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>.
7855                   </p></dd>
7856 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
7857 <dd><p>
7858                     See the description of
7859                     <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>.
7860                   </p></dd>
7861 <dt><span class="term"><span><strong class="command">dnssec-update-mode</strong></span></span></dt>
7862 <dd><p>
7863                     See the description of
7864                     <span><strong class="command">dnssec-update-mode</strong></span> in <a href="Bv9ARM.ch06.html#options" title="options Statement Definition and
7865           Usage">the section called &#8220;<span><strong class="command">options</strong></span> Statement Definition and
7866           Usage&#8221;</a>.
7867                   </p></dd>
7868 <dt><span class="term"><span><strong class="command">dnssec-dnskey-kskonly</strong></span></span></dt>
7869 <dd><p>
7870                     See the description of
7871                     <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>.
7872                   </p></dd>
7873 <dt><span class="term"><span><strong class="command">try-tcp-refresh</strong></span></span></dt>
7874 <dd><p>
7875                     See the description of
7876                     <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>.
7877                   </p></dd>
7878 <dt><span class="term"><span><strong class="command">database</strong></span></span></dt>
7879 <dd>
7880 <p>
7881                     Specify the type of database to be used for storing the
7882                     zone data.  The string following the <span><strong class="command">database</strong></span> keyword
7883                     is interpreted as a list of whitespace-delimited words.
7884                     The first word
7885                     identifies the database type, and any subsequent words are
7886                     passed
7887                     as arguments to the database to be interpreted in a way
7888                     specific
7889                     to the database type.
7890                   </p>
7891 <p>
7892                     The default is <strong class="userinput"><code>"rbt"</code></strong>, BIND 9's
7893                     native in-memory
7894                     red-black-tree database.  This database does not take
7895                     arguments.
7896                   </p>
7897 <p>
7898                     Other values are possible if additional database drivers
7899                     have been linked into the server.  Some sample drivers are
7900                     included
7901                     with the distribution but none are linked in by default.
7902                   </p>
7903 </dd>
7904 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
7905 <dd><p>
7906                     See the description of
7907                     <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>.
7908                   </p></dd>
7909 <dt><span class="term"><span><strong class="command">delegation-only</strong></span></span></dt>
7910 <dd>
7911 <p>
7912                     The flag only applies to forward, hint and stub
7913                     zones.  If set to <strong class="userinput"><code>yes</code></strong>,
7914                     then the zone will also be treated as if it is
7915                     also a delegation-only type zone.
7916                   </p>
7917 <p>
7918                     See caveats in <a href="Bv9ARM.ch06.html#root_delegation_only"><span><strong class="command">root-delegation-only</strong></span></a>.
7919                   </p>
7920 </dd>
7921 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
7922 <dd><p>
7923                     Only meaningful if the zone has a forwarders
7924                     list. The <span><strong class="command">only</strong></span> value causes
7925                     the lookup to fail
7926                     after trying the forwarders and getting no answer, while <span><strong class="command">first</strong></span> would
7927                     allow a normal lookup to be tried.
7928                   </p></dd>
7929 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
7930 <dd><p>
7931                     Used to override the list of global forwarders.
7932                     If it is not specified in a zone of type <span><strong class="command">forward</strong></span>,
7933                     no forwarding is done for the zone and the global options are
7934                     not used.
7935                   </p></dd>
7936 <dt><span class="term"><span><strong class="command">ixfr-base</strong></span></span></dt>
7937 <dd><p>
7938                     Was used in <acronym class="acronym">BIND</acronym> 8 to
7939                     specify the name
7940                     of the transaction log (journal) file for dynamic update
7941                     and IXFR.
7942                     <acronym class="acronym">BIND</acronym> 9 ignores the option
7943                     and constructs the name of the journal
7944                     file by appending "<code class="filename">.jnl</code>"
7945                     to the name of the
7946                     zone file.
7947                   </p></dd>
7948 <dt><span class="term"><span><strong class="command">ixfr-tmp-file</strong></span></span></dt>
7949 <dd><p>
7950                     Was an undocumented option in <acronym class="acronym">BIND</acronym> 8.
7951                     Ignored in <acronym class="acronym">BIND</acronym> 9.
7952                   </p></dd>
7953 <dt><span class="term"><span><strong class="command">journal</strong></span></span></dt>
7954 <dd><p>
7955                     Allow the default journal's filename to be overridden.
7956                     The default is the zone's filename with "<code class="filename">.jnl</code>" appended.
7957                     This is applicable to <span><strong class="command">master</strong></span> and <span><strong class="command">slave</strong></span> zones.
7958                   </p></dd>
7959 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
7960 <dd><p>
7961                     See the description of
7962                     <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>.
7963                   </p></dd>
7964 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
7965 <dd><p>
7966                     See the description of
7967                     <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>.
7968                   </p></dd>
7969 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
7970 <dd><p>
7971                     See the description of
7972                     <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>.
7973                   </p></dd>
7974 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
7975 <dd><p>
7976                     See the description of
7977                     <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>.
7978                   </p></dd>
7979 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
7980 <dd><p>
7981                     See the description of
7982                     <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>.
7983                   </p></dd>
7984 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
7985 <dd><p>
7986                     See the description of
7987                     <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>.
7988                   </p></dd>
7989 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
7990 <dd><p>
7991                     See the description of
7992                     <span><strong class="command">notify-delay</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
7993                   </p></dd>
7994 <dt><span class="term"><span><strong class="command">notify-to-soa</strong></span></span></dt>
7995 <dd><p>
7996                     See the description of
7997                     <span><strong class="command">notify-to-soa</strong></span> in
7998                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7999                   </p></dd>
8000 <dt><span class="term"><span><strong class="command">pubkey</strong></span></span></dt>
8001 <dd><p>
8002                     In <acronym class="acronym">BIND</acronym> 8, this option was
8003                     intended for specifying
8004                     a public zone key for verification of signatures in DNSSEC
8005                     signed
8006                     zones when they are loaded from disk. <acronym class="acronym">BIND</acronym> 9 does not verify signatures
8007                     on load and ignores the option.
8008                   </p></dd>
8009 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
8010 <dd><p>
8011                     If <strong class="userinput"><code>yes</code></strong>, the server will keep
8012                     statistical
8013                     information for this zone, which can be dumped to the
8014                     <span><strong class="command">statistics-file</strong></span> defined in
8015                     the server options.
8016                   </p></dd>
8017 <dt><span class="term"><span><strong class="command">server-addresses</strong></span></span></dt>
8018 <dd>
8019 <p>
8020                     Only meaningful for static-stub zones.
8021                     This is a list of IP addresses to which queries
8022                     should be sent in recursive resolution for the
8023                     zone.
8024                     A non empty list for this option will internally
8025                     configure the apex NS RR with associated glue A or
8026                     AAAA RRs.
8027                   </p>
8028 <p>
8029                     For example, if "example.com" is configured as a
8030                     static-stub zone with 192.0.2.1 and 2001:db8::1234
8031                     in a <span><strong class="command">server-addresses</strong></span> option,
8032                     the following RRs will be internally configured.
8033                   </p>
8034 <pre class="programlisting">example.com. NS example.com.
8035 example.com. A 192.0.2.1
8036 example.com. AAAA 2001:db8::1234</pre>
8037 <p>
8038                     These records are internally used to resolve
8039                     names under the static-stub zone.
8040                     For instance, if the server receives a query for
8041                     "www.example.com" with the RD bit on, the server
8042                     will initiate recursive resolution and send
8043                     queries to 192.0.2.1 and/or 2001:db8::1234.
8044                   </p>
8045 </dd>
8046 <dt><span class="term"><span><strong class="command">server-names</strong></span></span></dt>
8047 <dd>
8048 <p>
8049                     Only meaningful for static-stub zones.
8050                     This is a list of domain names of nameservers that
8051                     act as authoritative servers of the static-stub
8052                     zone.
8053                     These names will be resolved to IP addresses when
8054                     <span><strong class="command">named</strong></span> needs to send queries to
8055                     these servers.
8056                     To make this supplemental resolution successful,
8057                     these names must not be a subdomain of the origin
8058                     name of static-stub zone.
8059                     That is, when "example.net" is the origin of a
8060                     static-stub zone, "ns.example" and
8061                     "master.example.com" can be specified in the
8062                     <span><strong class="command">server-names</strong></span> option, but
8063                     "ns.example.net" cannot, and will be rejected by
8064                     the configuration parser.
8065                   </p>
8066 <p>
8067                     A non empty list for this option will internally
8068                     configure the apex NS RR with the specified names.
8069                     For example, if "example.com" is configured as a
8070                     static-stub zone with "ns1.example.net" and
8071                     "ns2.example.net"
8072                     in a <span><strong class="command">server-names</strong></span> option,
8073                     the following RRs will be internally configured.
8074                   </p>
8075 <pre class="programlisting">example.com. NS ns1.example.net.
8076 example.com. NS ns2.example.net.
8077 </pre>
8078 <p>
8079                     These records are internally used to resolve
8080                     names under the static-stub zone.
8081                     For instance, if the server receives a query for
8082                     "www.example.com" with the RD bit on, the server
8083                     initiate recursive resolution,
8084                     resolve "ns1.example.net" and/or
8085                     "ns2.example.net" to IP addresses, and then send
8086                     queries to (one or more of) these addresses.
8087                   </p>
8088 </dd>
8089 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
8090 <dd><p>
8091                     See the description of
8092                     <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>.
8093                   </p></dd>
8094 <dt><span class="term"><span><strong class="command">sig-signing-nodes</strong></span></span></dt>
8095 <dd><p>
8096                     See the description of
8097                     <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>.
8098                   </p></dd>
8099 <dt><span class="term"><span><strong class="command">sig-signing-signatures</strong></span></span></dt>
8100 <dd><p>
8101                     See the description of
8102                     <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>.
8103                   </p></dd>
8104 <dt><span class="term"><span><strong class="command">sig-signing-type</strong></span></span></dt>
8105 <dd><p>
8106                     See the description of
8107                     <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>.
8108                   </p></dd>
8109 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
8110 <dd><p>
8111                     See the description of
8112                     <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>.
8113                   </p></dd>
8114 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
8115 <dd><p>
8116                     See the description of
8117                     <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>.
8118                   </p></dd>
8119 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
8120 <dd><p>
8121                     See the description of
8122                     <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>.
8123                   </p></dd>
8124 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
8125 <dd><p>
8126                     See the description of
8127                     <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>.
8128                   </p></dd>
8129 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
8130 <dd><p>
8131                     See the description of
8132                     <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>.
8133                   </p></dd>
8134 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
8135 <dd><p>
8136                     See the description of
8137                     <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>.
8138                   </p></dd>
8139 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
8140 <dd><p>
8141                     See the description of
8142                     <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>.
8143                   </p></dd>
8144 <dt>
8145 <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>
8146 </dt>
8147 <dd><p>
8148                     See the description in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8149                   </p></dd>
8150 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
8151 <dd><p>
8152                     See the description of
8153                     <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>.
8154                     (Note that the <span><strong class="command">ixfr-from-differences</strong></span>
8155                     <strong class="userinput"><code>master</code></strong> and
8156                     <strong class="userinput"><code>slave</code></strong> choices are not
8157                     available at the zone level.)
8158                   </p></dd>
8159 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
8160 <dd><p>
8161                     See the description of
8162                     <span><strong class="command">key-directory</strong></span> in <a href="Bv9ARM.ch06.html#options" title="options Statement Definition and
8163           Usage">the section called &#8220;<span><strong class="command">options</strong></span> Statement Definition and
8164           Usage&#8221;</a>.
8165                   </p></dd>
8166 <dt><span class="term"><span><strong class="command">auto-dnssec</strong></span></span></dt>
8167 <dd>
8168 <p>
8169                     Zones configured for dynamic DNS may also use this
8170                     option to allow varying levels of automatic DNSSEC key
8171                     management. There are three possible settings:
8172                   </p>
8173 <p>
8174                     <span><strong class="command">auto-dnssec allow;</strong></span> permits
8175                     keys to be updated and the zone fully re-signed
8176                     whenever the user issues the command <span><strong class="command">rndc sign
8177                     <em class="replaceable"><code>zonename</code></em></strong></span>.
8178                   </p>
8179 <p>
8180                     <span><strong class="command">auto-dnssec maintain;</strong></span> includes the
8181                     above, but also automatically adjusts the zone's DNSSEC
8182                     keys on schedule, according to the keys' timing metadata
8183                     (see <a href="man.dnssec-keygen.html" title="dnssec-keygen"><span class="refentrytitle"><span class="application">dnssec-keygen</span></span>(8)</a> and
8184                     <a href="man.dnssec-settime.html" title="dnssec-settime"><span class="refentrytitle"><span class="application">dnssec-settime</span></span>(8)</a>).  The command
8185                     <span><strong class="command">rndc sign
8186                     <em class="replaceable"><code>zonename</code></em></strong></span> causes
8187                     <span><strong class="command">named</strong></span> to load keys from the key
8188                     repository and sign the zone with all keys that are
8189                     active.
8190                     <span><strong class="command">rndc loadkeys
8191                     <em class="replaceable"><code>zonename</code></em></strong></span> causes
8192                     <span><strong class="command">named</strong></span> to load keys from the key
8193                     repository and schedule key maintenance events to occur
8194                     in the future, but it does not sign the full zone
8195                     immediately.  Note: once keys have been loaded for a
8196                     zone the first time, the repository will be searched
8197                     for changes periodically, regardless of whether
8198                     <span><strong class="command">rndc loadkeys</strong></span> is used.  The recheck
8199                     interval is defined by
8200                     <span><strong class="command">dnssec-loadkeys-interval</strong></span>.)
8201                   </p>
8202 <p>
8203                     The default setting is <span><strong class="command">auto-dnssec off</strong></span>.
8204                   </p>
8205 </dd>
8206 <dt><span class="term"><span><strong class="command">serial-update-method</strong></span></span></dt>
8207 <dd>
8208 <p>
8209                     Zones configured for dynamic DNS may use this
8210                     option to set the update method that will be used for
8211                     the zone serial number in the SOA record.
8212                   </p>
8213 <p>
8214                     With the default setting of
8215                     <span><strong class="command">serial-update-method increment;</strong></span>, the
8216                     SOA serial number will be incremented by one each time
8217                     the zone is updated.
8218                   </p>
8219 <p>
8220                     When set to
8221                     <span><strong class="command">serial-update-method unixtime;</strong></span>, the
8222                     SOA serial number will be set to the number of seconds
8223                     since the UNIX epoch, unless the serial number is
8224                     already greater than or equal to that value, in which
8225                     case it is simply incremented by one.
8226                   </p>
8227 </dd>
8228 <dt><span class="term"><span><strong class="command">inline-signing</strong></span></span></dt>
8229 <dd><p>
8230                     If <code class="literal">yes</code>, this enables
8231                     "bump in the wire" signing of a zone, where a
8232                     unsigned zone is transferred in or loaded from
8233                     disk and a signed version of the zone is served,
8234                     with possibly, a different serial number.  This
8235                     behaviour is disabled by default.
8236                   </p></dd>
8237 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
8238 <dd><p>
8239                     See the description of <span><strong class="command">multi-master</strong></span> in
8240                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
8241                   </p></dd>
8242 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
8243 <dd><p>
8244                     See the description of <span><strong class="command">masterfile-format</strong></span>
8245                     in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
8246                   </p></dd>
8247 <dt><span class="term"><span><strong class="command">dnssec-secure-to-insecure</strong></span></span></dt>
8248 <dd><p>
8249                     See the description of
8250                     <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>.
8251                   </p></dd>
8252 </dl></div>
8253 </div>
8254 <div class="sect3" lang="en">
8255 <div class="titlepage"><div><div><h4 class="title">
8256 <a name="dynamic_update_policies"></a>Dynamic Update Policies</h4></div></div></div>
8257 <p><acronym class="acronym">BIND</acronym> 9 supports two alternative
8258               methods of granting clients the right to perform
8259               dynamic updates to a zone, configured by the
8260               <span><strong class="command">allow-update</strong></span> and
8261               <span><strong class="command">update-policy</strong></span> option, respectively.
8262             </p>
8263 <p>
8264               The <span><strong class="command">allow-update</strong></span> clause works the
8265               same way as in previous versions of <acronym class="acronym">BIND</acronym>.
8266               It grants given clients the permission to update any
8267               record of any name in the zone.
8268             </p>
8269 <p>
8270               The <span><strong class="command">update-policy</strong></span> clause
8271               allows more fine-grained control over what updates are
8272               allowed.  A set of rules is specified, where each rule
8273               either grants or denies permissions for one or more
8274               names to be updated by one or more identities.  If
8275               the dynamic update request message is signed (that is,
8276               it includes either a TSIG or SIG(0) record), the
8277               identity of the signer can be determined.
8278             </p>
8279 <p>
8280               Rules are specified in the <span><strong class="command">update-policy</strong></span>
8281               zone option, and are only meaningful for master zones.
8282               When the <span><strong class="command">update-policy</strong></span> statement
8283               is present, it is a configuration error for the
8284               <span><strong class="command">allow-update</strong></span> statement to be
8285               present.  The <span><strong class="command">update-policy</strong></span> statement
8286               only examines the signer of a message; the source
8287               address is not relevant.
8288             </p>
8289 <p>
8290               There is a pre-defined <span><strong class="command">update-policy</strong></span>
8291               rule which can be switched on with the command
8292               <span><strong class="command">update-policy local;</strong></span>.
8293               Switching on this rule in a zone causes
8294               <span><strong class="command">named</strong></span> to generate a TSIG session
8295               key and place it in a file, and to allow that key
8296               to update the zone.  (By default, the file is
8297               <code class="filename">/var/run/named/session.key</code>, the key
8298               name is "local-ddns" and the key algorithm is HMAC-SHA256,
8299               but these values are configurable with the
8300               <span><strong class="command">session-keyfile</strong></span>,
8301               <span><strong class="command">session-keyname</strong></span> and
8302               <span><strong class="command">session-keyalg</strong></span> options, respectively).
8303             </p>
8304 <p>
8305               A client running on the local system, and with appropriate
8306               permissions, may read that file and use the key to sign update
8307               requests.  The zone's update policy will be set to allow that
8308               key to change any record within the zone.  Assuming the
8309               key name is "local-ddns", this policy is equivalent to:
8310             </p>
8311 <pre class="programlisting">update-policy { grant local-ddns zonesub any; };
8312             </pre>
8313 <p>
8314               The command <span><strong class="command">nsupdate -l</strong></span> sends update
8315               requests to localhost, and signs them using the session key.
8316             </p>
8317 <p>
8318               Other rule definitions look like this:
8319             </p>
8320 <pre class="programlisting">
8321 ( <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>]
8322 </pre>
8323 <p>
8324               Each rule grants or denies privileges.  Once a message has
8325               successfully matched a rule, the operation is immediately
8326               granted or denied and no further rules are examined.  A rule
8327               is matched when the signer matches the identity field, the
8328               name matches the name field in accordance with the nametype
8329               field, and the type matches the types specified in the type
8330               field.
8331             </p>
8332 <p>
8333               No signer is required for <em class="replaceable"><code>tcp-self</code></em>
8334               or <em class="replaceable"><code>6to4-self</code></em> however the standard
8335               reverse mapping / prefix conversion must match the identity
8336               field.
8337             </p>
8338 <p>
8339               The identity field specifies a name or a wildcard
8340               name.  Normally, this is the name of the TSIG or
8341               SIG(0) key used to sign the update request.  When a
8342               TKEY exchange has been used to create a shared secret,
8343               the identity of the shared secret is the same as the
8344               identity of the key used to authenticate the TKEY
8345               exchange.  TKEY is also the negotiation method used
8346               by GSS-TSIG, which establishes an identity that is
8347               the Kerberos principal of the client, such as
8348               <strong class="userinput"><code>"user@host.domain"</code></strong>.  When the
8349               <em class="replaceable"><code>identity</code></em> field specifies
8350               a wildcard name, it is subject to DNS wildcard
8351               expansion, so the rule will apply to multiple identities.
8352               The <em class="replaceable"><code>identity</code></em> field must
8353               contain a fully-qualified domain name.
8354             </p>
8355 <p>
8356               For nametypes <code class="varname">krb5-self</code>,
8357               <code class="varname">ms-self</code>, <code class="varname">krb5-subdomain</code>,
8358               and <code class="varname">ms-subdomain</code> the
8359               <em class="replaceable"><code>identity</code></em> field specifies
8360               the Windows or Kerberos realm of the machine belongs to.
8361             </p>
8362 <p>
8363               The <em class="replaceable"><code>nametype</code></em> field has 13
8364               values:
8365               <code class="varname">name</code>, <code class="varname">subdomain</code>,
8366               <code class="varname">wildcard</code>, <code class="varname">self</code>,
8367               <code class="varname">selfsub</code>, <code class="varname">selfwild</code>,
8368               <code class="varname">krb5-self</code>, <code class="varname">ms-self</code>,
8369               <code class="varname">krb5-subdomain</code>,
8370               <code class="varname">ms-subdomain</code>,
8371               <code class="varname">tcp-self</code>, <code class="varname">6to4-self</code>,
8372               <code class="varname">zonesub</code>, and <code class="varname">external</code>.
8373             </p>
8374 <div class="informaltable"><table border="1">
8375 <colgroup>
8376 <col>
8377 <col>
8378 </colgroup>
8379 <tbody>
8380 <tr>
8381 <td>
8382                       <p>
8383                         <code class="varname">name</code>
8384                       </p>
8385                     </td>
8386 <td>
8387                       <p>
8388                         Exact-match semantics.  This rule matches
8389                         when the name being updated is identical
8390                         to the contents of the
8391                         <em class="replaceable"><code>name</code></em> field.
8392                       </p>
8393                     </td>
8394 </tr>
8395 <tr>
8396 <td>
8397                       <p>
8398                         <code class="varname">subdomain</code>
8399                       </p>
8400                     </td>
8401 <td>
8402                       <p>
8403                         This rule matches when the name being updated
8404                         is a subdomain of, or identical to, the
8405                         contents of the <em class="replaceable"><code>name</code></em>
8406                         field.
8407                       </p>
8408                     </td>
8409 </tr>
8410 <tr>
8411 <td>
8412                       <p>
8413                         <code class="varname">zonesub</code>
8414                       </p>
8415                     </td>
8416 <td>
8417                       <p>
8418                         This rule is similar to subdomain, except that
8419                         it matches when the name being updated is a
8420                         subdomain of the zone in which the
8421                         <span><strong class="command">update-policy</strong></span> statement
8422                         appears.  This obviates the need to type the zone
8423                         name twice, and enables the use of a standard
8424                         <span><strong class="command">update-policy</strong></span> statement in
8425                         multiple zones without modification.
8426                       </p>
8427                       <p>
8428                         When this rule is used, the
8429                         <em class="replaceable"><code>name</code></em> field is omitted.
8430                       </p>
8431                     </td>
8432 </tr>
8433 <tr>
8434 <td>
8435                       <p>
8436                         <code class="varname">wildcard</code>
8437                       </p>
8438                     </td>
8439 <td>
8440                       <p>
8441                         The <em class="replaceable"><code>name</code></em> field
8442                         is subject to DNS wildcard expansion, and
8443                         this rule matches when the name being updated
8444                         name is a valid expansion of the wildcard.
8445                       </p>
8446                     </td>
8447 </tr>
8448 <tr>
8449 <td>
8450                       <p>
8451                         <code class="varname">self</code>
8452                       </p>
8453                     </td>
8454 <td>
8455                       <p>
8456                         This rule matches when the name being updated
8457                         matches the contents of the
8458                         <em class="replaceable"><code>identity</code></em> field.
8459                         The <em class="replaceable"><code>name</code></em> field
8460                         is ignored, but should be the same as the
8461                         <em class="replaceable"><code>identity</code></em> field.
8462                         The <code class="varname">self</code> nametype is
8463                         most useful when allowing using one key per
8464                         name to update, where the key has the same
8465                         name as the name to be updated.  The
8466                         <em class="replaceable"><code>identity</code></em> would
8467                         be specified as <code class="constant">*</code> (an asterisk) in
8468                         this case.
8469                       </p>
8470                     </td>
8471 </tr>
8472 <tr>
8473 <td>
8474                       <p>
8475                         <code class="varname">selfsub</code>
8476                       </p>
8477                     </td>
8478 <td>
8479                       <p>
8480                         This rule is similar to <code class="varname">self</code>
8481                         except that subdomains of <code class="varname">self</code>
8482                         can also be updated.
8483                       </p>
8484                     </td>
8485 </tr>
8486 <tr>
8487 <td>
8488                       <p>
8489                         <code class="varname">selfwild</code>
8490                       </p>
8491                     </td>
8492 <td>
8493                       <p>
8494                         This rule is similar to <code class="varname">self</code>
8495                         except that only subdomains of
8496                         <code class="varname">self</code> can be updated.
8497                       </p>
8498                     </td>
8499 </tr>
8500 <tr>
8501 <td>
8502                       <p>
8503                         <code class="varname">ms-self</code>
8504                       </p>
8505                     </td>
8506 <td>
8507                       <p>
8508                         This rule takes a Windows machine principal
8509                         (machine$@REALM) for machine in REALM and
8510                         and converts it machine.realm allowing the machine
8511                         to update machine.realm.  The REALM to be matched
8512                         is specified in the <em class="replaceable"><code>identity</code></em>
8513                         field.
8514                       </p>
8515                     </td>
8516 </tr>
8517 <tr>
8518 <td>
8519                       <p>
8520                         <code class="varname">ms-subdomain</code>
8521                       </p>
8522                     </td>
8523 <td>
8524                       <p>
8525                         This rule takes a Windows machine principal
8526                         (machine$@REALM) for machine in REALM and
8527                         converts it to machine.realm allowing the machine
8528                         to update subdomains of machine.realm.  The REALM
8529                         to be matched is specified in the
8530                         <em class="replaceable"><code>identity</code></em> field.
8531                       </p>
8532                     </td>
8533 </tr>
8534 <tr>
8535 <td>
8536                       <p>
8537                         <code class="varname">krb5-self</code>
8538                       </p>
8539                     </td>
8540 <td>
8541                       <p>
8542                         This rule takes a Kerberos machine principal
8543                         (host/machine@REALM) for machine in REALM and
8544                         and converts it machine.realm allowing the machine
8545                         to update machine.realm.  The REALM to be matched
8546                         is specified in the <em class="replaceable"><code>identity</code></em>
8547                         field.
8548                       </p>
8549                     </td>
8550 </tr>
8551 <tr>
8552 <td>
8553                       <p>
8554                         <code class="varname">krb5-subdomain</code>
8555                       </p>
8556                     </td>
8557 <td>
8558                       <p>
8559                         This rule takes a Kerberos machine principal
8560                         (host/machine@REALM) for machine in REALM and
8561                         converts it to machine.realm allowing the machine
8562                         to update subdomains of machine.realm.  The REALM
8563                         to be matched is specified in the
8564                         <em class="replaceable"><code>identity</code></em> field.
8565                       </p>
8566                     </td>
8567 </tr>
8568 <tr>
8569 <td>
8570                       <p>
8571                         <code class="varname">tcp-self</code>
8572                       </p>
8573                     </td>
8574 <td>
8575                       <p>
8576                         Allow updates that have been sent via TCP and
8577                         for which the standard mapping from the initiating
8578                         IP address into the IN-ADDR.ARPA and IP6.ARPA
8579                         namespaces match the name to be updated.
8580                       </p>
8581                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
8582 <h3 class="title">Note</h3>
8583                         It is theoretically possible to spoof these TCP
8584                         sessions.
8585                       </div>
8586                     </td>
8587 </tr>
8588 <tr>
8589 <td>
8590                       <p>
8591                         <code class="varname">6to4-self</code>
8592                       </p>
8593                     </td>
8594 <td>
8595                       <p>
8596                         Allow the 6to4 prefix to be update by any TCP
8597                         connection from the 6to4 network or from the
8598                         corresponding IPv4 address.  This is intended
8599                         to allow NS or DNAME RRsets to be added to the
8600                         reverse tree.
8601                       </p>
8602                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
8603 <h3 class="title">Note</h3>
8604                         It is theoretically possible to spoof these TCP
8605                         sessions.
8606                       </div>
8607                     </td>
8608 </tr>
8609 <tr>
8610 <td>
8611                       <p>
8612                         <code class="varname">external</code>
8613                       </p>
8614                     </td>
8615 <td>
8616                       <p>
8617                         This rule allows <span><strong class="command">named</strong></span>
8618                         to defer the decision of whether to allow a
8619                         given update to an external daemon.
8620                       </p>
8621                       <p>
8622                         The method of communicating with the daemon is
8623                         specified in the <em class="replaceable"><code>identity</code></em>
8624                         field, the format of which is
8625                         "<code class="constant">local:</code><em class="replaceable"><code>path</code></em>",
8626                         where <em class="replaceable"><code>path</code></em> is the location
8627                         of a UNIX-domain socket.  (Currently, "local" is the
8628                         only supported mechanism.)
8629                       </p>
8630                       <p>
8631                         Requests to the external daemon are sent over the
8632                         UNIX-domain socket as datagrams with the following
8633                         format:
8634                       </p>
8635                       <pre class="programlisting">
8636    Protocol version number (4 bytes, network byte order, currently 1)
8637    Request length (4 bytes, network byte order)
8638    Signer (null-terminated string)
8639    Name (null-terminated string)
8640    TCP source address (null-terminated string)
8641    Rdata type (null-terminated string)
8642    Key (null-terminated string)
8643    TKEY token length (4 bytes, network byte order)
8644    TKEY token (remainder of packet)</pre>
8645                       <p>
8646                         The daemon replies with a four-byte value in
8647                         network byte order, containing either 0 or 1; 0
8648                         indicates that the specified update is not
8649                         permitted, and 1 indicates that it is.
8650                       </p>
8651                     </td>
8652 </tr>
8653 </tbody>
8654 </table></div>
8655 <p>
8656               In all cases, the <em class="replaceable"><code>name</code></em>
8657               field must specify a fully-qualified domain name.
8658             </p>
8659 <p>
8660               If no types are explicitly specified, this rule matches
8661               all types except RRSIG, NS, SOA, NSEC and NSEC3. Types
8662               may be specified by name, including "ANY" (ANY matches
8663               all types except NSEC and NSEC3, which can never be
8664               updated).  Note that when an attempt is made to delete
8665               all records associated with a name, the rules are
8666               checked for each existing record type.
8667             </p>
8668 </div>
8669 </div>
8670 </div>
8671 <div class="sect1" lang="en">
8672 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
8673 <a name="id2597084"></a>Zone File</h2></div></div></div>
8674 <div class="sect2" lang="en">
8675 <div class="titlepage"><div><div><h3 class="title">
8676 <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>
8677 <p>
8678             This section, largely borrowed from RFC 1034, describes the
8679             concept of a Resource Record (RR) and explains when each is used.
8680             Since the publication of RFC 1034, several new RRs have been
8681             identified
8682             and implemented in the DNS. These are also included.
8683           </p>
8684 <div class="sect3" lang="en">
8685 <div class="titlepage"><div><div><h4 class="title">
8686 <a name="id2597102"></a>Resource Records</h4></div></div></div>
8687 <p>
8688               A domain name identifies a node.  Each node has a set of
8689               resource information, which may be empty.  The set of resource
8690               information associated with a particular name is composed of
8691               separate RRs. The order of RRs in a set is not significant and
8692               need not be preserved by name servers, resolvers, or other
8693               parts of the DNS. However, sorting of multiple RRs is
8694               permitted for optimization purposes, for example, to specify
8695               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>.
8696             </p>
8697 <p>
8698               The components of a Resource Record are:
8699             </p>
8700 <div class="informaltable"><table border="1">
8701 <colgroup>
8702 <col>
8703 <col>
8704 </colgroup>
8705 <tbody>
8706 <tr>
8707 <td>
8708                       <p>
8709                         owner name
8710                       </p>
8711                     </td>
8712 <td>
8713                       <p>
8714                         The domain name where the RR is found.
8715                       </p>
8716                     </td>
8717 </tr>
8718 <tr>
8719 <td>
8720                       <p>
8721                         type
8722                       </p>
8723                     </td>
8724 <td>
8725                       <p>
8726                         An encoded 16-bit value that specifies
8727                         the type of the resource record.
8728                       </p>
8729                     </td>
8730 </tr>
8731 <tr>
8732 <td>
8733                       <p>
8734                         TTL
8735                       </p>
8736                     </td>
8737 <td>
8738                       <p>
8739                         The time-to-live of the RR. This field
8740                         is a 32-bit integer in units of seconds, and is
8741                         primarily used by
8742                         resolvers when they cache RRs. The TTL describes how
8743                         long a RR can
8744                         be cached before it should be discarded.
8745                       </p>
8746                     </td>
8747 </tr>
8748 <tr>
8749 <td>
8750                       <p>
8751                         class
8752                       </p>
8753                     </td>
8754 <td>
8755                       <p>
8756                         An encoded 16-bit value that identifies
8757                         a protocol family or instance of a protocol.
8758                       </p>
8759                     </td>
8760 </tr>
8761 <tr>
8762 <td>
8763                       <p>
8764                         RDATA
8765                       </p>
8766                     </td>
8767 <td>
8768                       <p>
8769                         The resource data.  The format of the
8770                         data is type (and sometimes class) specific.
8771                       </p>
8772                     </td>
8773 </tr>
8774 </tbody>
8775 </table></div>
8776 <p>
8777               The following are <span class="emphasis"><em>types</em></span> of valid RRs:
8778             </p>
8779 <div class="informaltable"><table border="1">
8780 <colgroup>
8781 <col>
8782 <col>
8783 </colgroup>
8784 <tbody>
8785 <tr>
8786 <td>
8787                       <p>
8788                         A
8789                       </p>
8790                     </td>
8791 <td>
8792                       <p>
8793                         A host address.  In the IN class, this is a
8794                         32-bit IP address.  Described in RFC 1035.
8795                       </p>
8796                     </td>
8797 </tr>
8798 <tr>
8799 <td>
8800                       <p>
8801                         AAAA
8802                       </p>
8803                     </td>
8804 <td>
8805                       <p>
8806                         IPv6 address.  Described in RFC 1886.
8807                       </p>
8808                     </td>
8809 </tr>
8810 <tr>
8811 <td>
8812                       <p>
8813                         A6
8814                       </p>
8815                     </td>
8816 <td>
8817                       <p>
8818                         IPv6 address.  This can be a partial
8819                         address (a suffix) and an indirection to the name
8820                         where the rest of the
8821                         address (the prefix) can be found.  Experimental.
8822                         Described in RFC 2874.
8823                       </p>
8824                     </td>
8825 </tr>
8826 <tr>
8827 <td>
8828                       <p>
8829                         AFSDB
8830                       </p>
8831                     </td>
8832 <td>
8833                       <p>
8834                         Location of AFS database servers.
8835                         Experimental.  Described in RFC 1183.
8836                       </p>
8837                     </td>
8838 </tr>
8839 <tr>
8840 <td>
8841                       <p>
8842                         APL
8843                       </p>
8844                     </td>
8845 <td>
8846                       <p>
8847                         Address prefix list.  Experimental.
8848                         Described in RFC 3123.
8849                       </p>
8850                     </td>
8851 </tr>
8852 <tr>
8853 <td>
8854                       <p>
8855                         ATMA
8856                       </p>
8857                     </td>
8858 <td>
8859                       <p>
8860                         ATM Address.
8861                       </p>
8862                     </td>
8863 </tr>
8864 <tr>
8865 <td>
8866                       <p>
8867                         CAA
8868                       </p>
8869                     </td>
8870 <td>
8871                       <p>
8872                         Identifies which Certificate Authorities can issue
8873                         certificates for this domain and what rules they
8874                         need to follow when doing so. Defined in RFC 6844.
8875                       </p>
8876                     </td>
8877 </tr>
8878 <tr>
8879 <td>
8880                       <p>
8881                         CDNSKEY
8882                       </p>
8883                     </td>
8884 <td>
8885                       <p>
8886                         Identifies which DNSKEY records should be published
8887                         as DS records in the parent zone.
8888                       </p>
8889                     </td>
8890 </tr>
8891 <tr>
8892 <td>
8893                       <p>
8894                         CDS
8895                       </p>
8896                     </td>
8897 <td>
8898                       <p>
8899                         Contains the set of DS records that should be published
8900                         by the parent zone.
8901                       </p>
8902                     </td>
8903 </tr>
8904 <tr>
8905 <td>
8906                       <p>
8907                         CERT
8908                       </p>
8909                     </td>
8910 <td>
8911                       <p>
8912                         Holds a digital certificate.
8913                         Described in RFC 2538.
8914                       </p>
8915                     </td>
8916 </tr>
8917 <tr>
8918 <td>
8919                       <p>
8920                         CNAME
8921                       </p>
8922                     </td>
8923 <td>
8924                       <p>
8925                         Identifies the canonical name of an alias.
8926                         Described in RFC 1035.
8927                       </p>
8928                     </td>
8929 </tr>
8930 <tr>
8931 <td>
8932                       <p>
8933                         DHCID
8934                       </p>
8935                     </td>
8936 <td>
8937                       <p>
8938                         Is used for identifying which DHCP client is
8939                         associated with this name.  Described in RFC 4701.
8940                       </p>
8941                     </td>
8942 </tr>
8943 <tr>
8944 <td>
8945                       <p>
8946                         DLV
8947                       </p>
8948                     </td>
8949 <td>
8950                       <p>
8951                         A DNS Look-aside Validation record which contains
8952                         the records that are used as trust anchors for
8953                         zones in a DLV namespace.  Described in RFC 4431.
8954                       </p>
8955                     </td>
8956 </tr>
8957 <tr>
8958 <td>
8959                       <p>
8960                         DNAME
8961                       </p>
8962                     </td>
8963 <td>
8964                       <p>
8965                         Replaces the domain name specified with
8966                         another name to be looked up, effectively aliasing an
8967                         entire
8968                         subtree of the domain name space rather than a single
8969                         record
8970                         as in the case of the CNAME RR.
8971                         Described in RFC 2672.
8972                       </p>
8973                     </td>
8974 </tr>
8975 <tr>
8976 <td>
8977                       <p>
8978                         DNSKEY
8979                       </p>
8980                     </td>
8981 <td>
8982                       <p>
8983                         Stores a public key associated with a signed
8984                         DNS zone.  Described in RFC 4034.
8985                       </p>
8986                     </td>
8987 </tr>
8988 <tr>
8989 <td>
8990                       <p>
8991                         DS
8992                       </p>
8993                     </td>
8994 <td>
8995                       <p>
8996                         Stores the hash of a public key associated with a
8997                         signed DNS zone.  Described in RFC 4034.
8998                       </p>
8999                     </td>
9000 </tr>
9001 <tr>
9002 <td>
9003                       <p>
9004                         EID
9005                       </p>
9006                     </td>
9007 <td>
9008                       <p>
9009                         End Point Identifier.
9010                       </p>
9011                     </td>
9012 </tr>
9013 <tr>
9014 <td>
9015                       <p>
9016                         EUI48
9017                       </p>
9018                     </td>
9019 <td>
9020                       <p>
9021                         A 48-bit EUI address. Described in RFC 7043.
9022                       </p>
9023                     </td>
9024 </tr>
9025 <tr>
9026 <td>
9027                       <p>
9028                         EUI64
9029                       </p>
9030                     </td>
9031 <td>
9032                       <p>
9033                         A 64-bit EUI address. Described in RFC 7043.
9034                       </p>
9035                     </td>
9036 </tr>
9037 <tr>
9038 <td>
9039                       <p>
9040                         GID
9041                       </p>
9042                     </td>
9043 <td>
9044                       <p>
9045                         Reserved.
9046                       </p>
9047                     </td>
9048 </tr>
9049 <tr>
9050 <td>
9051                       <p>
9052                         GPOS
9053                       </p>
9054                     </td>
9055 <td>
9056                       <p>
9057                         Specifies the global position.  Superseded by LOC.
9058                       </p>
9059                     </td>
9060 </tr>
9061 <tr>
9062 <td>
9063                       <p>
9064                         HINFO
9065                       </p>
9066                     </td>
9067 <td>
9068                       <p>
9069                         Identifies the CPU and OS used by a host.
9070                         Described in RFC 1035.
9071                       </p>
9072                     </td>
9073 </tr>
9074 <tr>
9075 <td>
9076                       <p>
9077                         HIP
9078                       </p>
9079                     </td>
9080 <td>
9081                       <p>
9082                         Host Identity Protocol Address.
9083                         Described in RFC 5205.
9084                       </p>
9085                     </td>
9086 </tr>
9087 <tr>
9088 <td>
9089                       <p>
9090                         IPSECKEY
9091                       </p>
9092                     </td>
9093 <td>
9094                       <p>
9095                         Provides a method for storing IPsec keying material in
9096                         DNS.  Described in RFC 4025.
9097                       </p>
9098                     </td>
9099 </tr>
9100 <tr>
9101 <td>
9102                       <p>
9103                         ISDN
9104                       </p>
9105                     </td>
9106 <td>
9107                       <p>
9108                         Representation of ISDN addresses.
9109                         Experimental.  Described in RFC 1183.
9110                       </p>
9111                     </td>
9112 </tr>
9113 <tr>
9114 <td>
9115                       <p>
9116                         KEY
9117                       </p>
9118                     </td>
9119 <td>
9120                       <p>
9121                         Stores a public key associated with a
9122                         DNS name.  Used in original DNSSEC; replaced
9123                         by DNSKEY in DNSSECbis, but still used with
9124                         SIG(0).  Described in RFCs 2535 and 2931.
9125                       </p>
9126                     </td>
9127 </tr>
9128 <tr>
9129 <td>
9130                       <p>
9131                         KX
9132                       </p>
9133                     </td>
9134 <td>
9135                       <p>
9136                         Identifies a key exchanger for this
9137                         DNS name.  Described in RFC 2230.
9138                       </p>
9139                     </td>
9140 </tr>
9141 <tr>
9142 <td>
9143                       <p>
9144                         L32
9145                       </p>
9146                     </td>
9147 <td>
9148                       <p>
9149                         Holds 32-bit Locator values for
9150                         Identifier-Locator Network Protocol. Described
9151                         in RFC 6742.
9152                       </p>
9153                     </td>
9154 </tr>
9155 <tr>
9156 <td>
9157                       <p>
9158                         L64
9159                       </p>
9160                     </td>
9161 <td>
9162                       <p>
9163                         Holds 64-bit Locator values for
9164                         Identifier-Locator Network Protocol. Described
9165                         in RFC 6742.
9166                       </p>
9167                     </td>
9168 </tr>
9169 <tr>
9170 <td>
9171                       <p>
9172                         LOC
9173                       </p>
9174                     </td>
9175 <td>
9176                       <p>
9177                         For storing GPS info.  Described in RFC 1876.
9178                         Experimental.
9179                       </p>
9180                     </td>
9181 </tr>
9182 <tr>
9183 <td>
9184                       <p>
9185                         LP
9186                       </p>
9187                     </td>
9188 <td>
9189                       <p>
9190                         Identifier-Locator Network Protocol.
9191                         Described in RFC 6742.
9192                       </p>
9193                     </td>
9194 </tr>
9195 <tr>
9196 <td>
9197                       <p>
9198                         MB
9199                       </p>
9200                     </td>
9201 <td>
9202                       <p>
9203                         Mail Box.  Historical.
9204                       </p>
9205                     </td>
9206 </tr>
9207 <tr>
9208 <td>
9209                       <p>
9210                         MD
9211                       </p>
9212                     </td>
9213 <td>
9214                       <p>
9215                         Mail Destination.  Historical.
9216                       </p>
9217                     </td>
9218 </tr>
9219 <tr>
9220 <td>
9221                       <p>
9222                         MF
9223                       </p>
9224                     </td>
9225 <td>
9226                       <p>
9227                         Mail Forwarder.  Historical.
9228                       </p>
9229                     </td>
9230 </tr>
9231 <tr>
9232 <td>
9233                       <p>
9234                         MG
9235                       </p>
9236                     </td>
9237 <td>
9238                       <p>
9239                         Mail Group.  Historical.
9240                       </p>
9241                     </td>
9242 </tr>
9243 <tr>
9244 <td>
9245                       <p>
9246                         MINFO
9247                       </p>
9248                     </td>
9249 <td>
9250                       <p>
9251                         Mail Information.
9252                       </p>
9253                     </td>
9254 </tr>
9255 <tr>
9256 <td>
9257                       <p>
9258                         MR
9259                       </p>
9260                     </td>
9261 <td>
9262                       <p>
9263                         Mail Rename. Historical.
9264                       </p>
9265                     </td>
9266 </tr>
9267 <tr>
9268 <td>
9269                       <p>
9270                         MX
9271                       </p>
9272                     </td>
9273 <td>
9274                       <p>
9275                         Identifies a mail exchange for the domain with
9276                         a 16-bit preference value (lower is better)
9277                         followed by the host name of the mail exchange.
9278                         Described in RFC 974, RFC 1035.
9279                       </p>
9280                     </td>
9281 </tr>
9282 <tr>
9283 <td>
9284                       <p>
9285                         NAPTR
9286                       </p>
9287                     </td>
9288 <td>
9289                       <p>
9290                         Name authority pointer.  Described in RFC 2915.
9291                       </p>
9292                     </td>
9293 </tr>
9294 <tr>
9295 <td>
9296                       <p>
9297                         NID
9298                       </p>
9299                     </td>
9300 <td>
9301                       <p>
9302                         Holds values for Node Identifiers in
9303                         Identifier-Locator Network Protocol. Described
9304                         in RFC 6742.
9305                       </p>
9306                     </td>
9307 </tr>
9308 <tr>
9309 <td>
9310                       <p>
9311                         NIMLOC
9312                       </p>
9313                     </td>
9314 <td>
9315                       <p>
9316                         Nimrod Locator.
9317                       </p>
9318                     </td>
9319 </tr>
9320 <tr>
9321 <td>
9322                       <p>
9323                         NSAP
9324                       </p>
9325                     </td>
9326 <td>
9327                       <p>
9328                         A network service access point.
9329                         Described in RFC 1706.
9330                       </p>
9331                     </td>
9332 </tr>
9333 <tr>
9334 <td>
9335                       <p>
9336                         NSAP-PTR
9337                       </p>
9338                     </td>
9339 <td>
9340                       <p>
9341                         Historical.
9342                       </p>
9343                     </td>
9344 </tr>
9345 <tr>
9346 <td>
9347                       <p>
9348                         NS
9349                       </p>
9350                     </td>
9351 <td>
9352                       <p>
9353                         The authoritative name server for the
9354                         domain.  Described in RFC 1035.
9355                       </p>
9356                     </td>
9357 </tr>
9358 <tr>
9359 <td>
9360                       <p>
9361                         NSEC
9362                       </p>
9363                     </td>
9364 <td>
9365                       <p>
9366                         Used in DNSSECbis to securely indicate that
9367                         RRs with an owner name in a certain name interval do
9368                         not exist in
9369                         a zone and indicate what RR types are present for an
9370                         existing name.
9371                         Described in RFC 4034.
9372                       </p>
9373                     </td>
9374 </tr>
9375 <tr>
9376 <td>
9377                       <p>
9378                         NSEC3
9379                       </p>
9380                     </td>
9381 <td>
9382                       <p>
9383                         Used in DNSSECbis to securely indicate that
9384                         RRs with an owner name in a certain name
9385                         interval do not exist in a zone and indicate
9386                         what RR types are present for an existing
9387                         name.  NSEC3 differs from NSEC in that it
9388                         prevents zone enumeration but is more
9389                         computationally expensive on both the server
9390                         and the client than NSEC.  Described in RFC
9391                         5155.
9392                       </p>
9393                     </td>
9394 </tr>
9395 <tr>
9396 <td>
9397                       <p>
9398                         NSEC3PARAM
9399                       </p>
9400                     </td>
9401 <td>
9402                       <p>
9403                         Used in DNSSECbis to tell the authoritative
9404                         server which NSEC3 chains are available to use.
9405                         Described in RFC 5155.
9406                       </p>
9407                     </td>
9408 </tr>
9409 <tr>
9410 <td>
9411                       <p>
9412                         NULL
9413                       </p>
9414                     </td>
9415 <td>
9416                       <p>
9417                         This is an opaque container.
9418                       </p>
9419                     </td>
9420 </tr>
9421 <tr>
9422 <td>
9423                       <p>
9424                         NXT
9425                       </p>
9426                     </td>
9427 <td>
9428                       <p>
9429                         Used in DNSSEC to securely indicate that
9430                         RRs with an owner name in a certain name interval do
9431                         not exist in
9432                         a zone and indicate what RR types are present for an
9433                         existing name.
9434                         Used in original DNSSEC; replaced by NSEC in
9435                         DNSSECbis.
9436                         Described in RFC 2535.
9437                       </p>
9438                     </td>
9439 </tr>
9440 <tr>
9441 <td>
9442                       <p>
9443                         OPENPGPKEY
9444                       </p>
9445                     </td>
9446 <td>
9447                       <p>
9448                         Used to hold an OPENPGPKEY.
9449                       </p>
9450                     </td>
9451 </tr>
9452 <tr>
9453 <td>
9454                       <p>
9455                         PTR
9456                       </p>
9457                     </td>
9458 <td>
9459                       <p>
9460                         A pointer to another part of the domain
9461                         name space.  Described in RFC 1035.
9462                       </p>
9463                     </td>
9464 </tr>
9465 <tr>
9466 <td>
9467                       <p>
9468                         PX
9469                       </p>
9470                     </td>
9471 <td>
9472                       <p>
9473                         Provides mappings between RFC 822 and X.400
9474                         addresses.  Described in RFC 2163.
9475                       </p>
9476                     </td>
9477 </tr>
9478 <tr>
9479 <td>
9480                       <p>
9481                         RP
9482                       </p>
9483                     </td>
9484 <td>
9485                       <p>
9486                         Information on persons responsible
9487                         for the domain.  Experimental.  Described in RFC 1183.
9488                       </p>
9489                     </td>
9490 </tr>
9491 <tr>
9492 <td>
9493                       <p>
9494                         RRSIG
9495                       </p>
9496                     </td>
9497 <td>
9498                       <p>
9499                         Contains DNSSECbis signature data.  Described
9500                         in RFC 4034.
9501                       </p>
9502                     </td>
9503 </tr>
9504 <tr>
9505 <td>
9506                       <p>
9507                         RT
9508                       </p>
9509                     </td>
9510 <td>
9511                       <p>
9512                         Route-through binding for hosts that
9513                         do not have their own direct wide area network
9514                         addresses.
9515                         Experimental.  Described in RFC 1183.
9516                       </p>
9517                     </td>
9518 </tr>
9519 <tr>
9520 <td>
9521                       <p>
9522                         SIG
9523                       </p>
9524                     </td>
9525 <td>
9526                       <p>
9527                         Contains DNSSEC signature data.  Used in
9528                         original DNSSEC; replaced by RRSIG in
9529                         DNSSECbis, but still used for SIG(0).
9530                         Described in RFCs 2535 and 2931.
9531                       </p>
9532                     </td>
9533 </tr>
9534 <tr>
9535 <td>
9536                       <p>
9537                         SOA
9538                       </p>
9539                     </td>
9540 <td>
9541                       <p>
9542                         Identifies the start of a zone of authority.
9543                         Described in RFC 1035.
9544                       </p>
9545                     </td>
9546 </tr>
9547 <tr>
9548 <td>
9549                       <p>
9550                         SPF
9551                       </p>
9552                     </td>
9553 <td>
9554                       <p>
9555                         Contains the Sender Policy Framework information
9556                         for a given email domain.  Described in RFC 4408.
9557                       </p>
9558                     </td>
9559 </tr>
9560 <tr>
9561 <td>
9562                       <p>
9563                         SRV
9564                       </p>
9565                     </td>
9566 <td>
9567                       <p>
9568                         Information about well known network
9569                         services (replaces WKS).  Described in RFC 2782.
9570                       </p>
9571                     </td>
9572 </tr>
9573 <tr>
9574 <td>
9575                       <p>
9576                         SSHFP
9577                       </p>
9578                     </td>
9579 <td>
9580                       <p>
9581                         Provides a way to securely publish a secure shell key's
9582                         fingerprint.  Described in RFC 4255.
9583                       </p>
9584                     </td>
9585 </tr>
9586 <tr>
9587 <td>
9588                       <p>
9589                         TLSA
9590                       </p>
9591                     </td>
9592 <td>
9593                       <p>
9594                         Transport Layer Security Certificate Association.
9595                         Described in RFC 6698.
9596                       </p>
9597                     </td>
9598 </tr>
9599 <tr>
9600 <td>
9601                       <p>
9602                         TXT
9603                       </p>
9604                     </td>
9605 <td>
9606                       <p>
9607                         Text records.  Described in RFC 1035.
9608                       </p>
9609                     </td>
9610 </tr>
9611 <tr>
9612 <td>
9613                       <p>
9614                         UID
9615                       </p>
9616                     </td>
9617 <td>
9618                       <p>
9619                         Reserved.
9620                       </p>
9621                     </td>
9622 </tr>
9623 <tr>
9624 <td>
9625                       <p>
9626                         UINFO
9627                       </p>
9628                     </td>
9629 <td>
9630                       <p>
9631                         Reserved.
9632                       </p>
9633                     </td>
9634 </tr>
9635 <tr>
9636 <td>
9637                       <p>
9638                         UNSPEC
9639                       </p>
9640                     </td>
9641 <td>
9642                       <p>
9643                         Reserved. Historical.
9644                       </p>
9645                     </td>
9646 </tr>
9647 <tr>
9648 <td>
9649                       <p>
9650                         URI
9651                       </p>
9652                     </td>
9653 <td>
9654                       <p>
9655                         Holds a URI. Described in RFC 7553.
9656                       </p>
9657                     </td>
9658 </tr>
9659 <tr>
9660 <td>
9661                       <p>
9662                         WKS
9663                       </p>
9664                     </td>
9665 <td>
9666                       <p>
9667                         Information about which well known
9668                         network services, such as SMTP, that a domain
9669                         supports. Historical.
9670                       </p>
9671                     </td>
9672 </tr>
9673 <tr>
9674 <td>
9675                       <p>
9676                         X25
9677                       </p>
9678                     </td>
9679 <td>
9680                       <p>
9681                         Representation of X.25 network addresses.
9682                         Experimental.  Described in RFC 1183.
9683                       </p>
9684                     </td>
9685 </tr>
9686 </tbody>
9687 </table></div>
9688 <p>
9689               The following <span class="emphasis"><em>classes</em></span> of resource records
9690               are currently valid in the DNS:
9691             </p>
9692 <div class="informaltable"><table border="1">
9693 <colgroup>
9694 <col>
9695 <col>
9696 </colgroup>
9697 <tbody>
9698 <tr>
9699 <td>
9700                       <p>
9701                         IN
9702                       </p>
9703                     </td>
9704 <td>
9705                       <p>
9706                         The Internet.
9707                       </p>
9708                     </td>
9709 </tr>
9710 <tr>
9711 <td>
9712                       <p>
9713                         CH
9714                       </p>
9715                     </td>
9716 <td>
9717                       <p>
9718                         Chaosnet, a LAN protocol created at MIT in the
9719                         mid-1970s.
9720                         Rarely used for its historical purpose, but reused for
9721                         BIND's
9722                         built-in server information zones, e.g.,
9723                         <code class="literal">version.bind</code>.
9724                       </p>
9725                     </td>
9726 </tr>
9727 <tr>
9728 <td>
9729                       <p>
9730                         HS
9731                       </p>
9732                     </td>
9733 <td>
9734                       <p>
9735                         Hesiod, an information service
9736                         developed by MIT's Project Athena. It is used to share
9737                         information
9738                         about various systems databases, such as users,
9739                         groups, printers
9740                         and so on.
9741                       </p>
9742                     </td>
9743 </tr>
9744 </tbody>
9745 </table></div>
9746 <p>
9747               The owner name is often implicit, rather than forming an
9748               integral
9749               part of the RR.  For example, many name servers internally form
9750               tree
9751               or hash structures for the name space, and chain RRs off nodes.
9752               The remaining RR parts are the fixed header (type, class, TTL)
9753               which is consistent for all RRs, and a variable part (RDATA)
9754               that
9755               fits the needs of the resource being described.
9756             </p>
9757 <p>
9758               The meaning of the TTL field is a time limit on how long an
9759               RR can be kept in a cache.  This limit does not apply to
9760               authoritative
9761               data in zones; it is also timed out, but by the refreshing
9762               policies
9763               for the zone.  The TTL is assigned by the administrator for the
9764               zone where the data originates.  While short TTLs can be used to
9765               minimize caching, and a zero TTL prohibits caching, the
9766               realities
9767               of Internet performance suggest that these times should be on
9768               the
9769               order of days for the typical host.  If a change can be
9770               anticipated,
9771               the TTL can be reduced prior to the change to minimize
9772               inconsistency
9773               during the change, and then increased back to its former value
9774               following
9775               the change.
9776             </p>
9777 <p>
9778               The data in the RDATA section of RRs is carried as a combination
9779               of binary strings and domain names.  The domain names are
9780               frequently
9781               used as "pointers" to other data in the DNS.
9782             </p>
9783 </div>
9784 <div class="sect3" lang="en">
9785 <div class="titlepage"><div><div><h4 class="title">
9786 <a name="id2599413"></a>Textual expression of RRs</h4></div></div></div>
9787 <p>
9788               RRs are represented in binary form in the packets of the DNS
9789               protocol, and are usually represented in highly encoded form
9790               when
9791               stored in a name server or resolver.  In the examples provided
9792               in
9793               RFC 1034, a style similar to that used in master files was
9794               employed
9795               in order to show the contents of RRs.  In this format, most RRs
9796               are shown on a single line, although continuation lines are
9797               possible
9798               using parentheses.
9799             </p>
9800 <p>
9801               The start of the line gives the owner of the RR.  If a line
9802               begins with a blank, then the owner is assumed to be the same as
9803               that of the previous RR.  Blank lines are often included for
9804               readability.
9805             </p>
9806 <p>
9807               Following the owner, we list the TTL, type, and class of the
9808               RR.  Class and type use the mnemonics defined above, and TTL is
9809               an integer before the type field.  In order to avoid ambiguity
9810               in
9811               parsing, type and class mnemonics are disjoint, TTLs are
9812               integers,
9813               and the type mnemonic is always last. The IN class and TTL
9814               values
9815               are often omitted from examples in the interests of clarity.
9816             </p>
9817 <p>
9818               The resource data or RDATA section of the RR are given using
9819               knowledge of the typical representation for the data.
9820             </p>
9821 <p>
9822               For example, we might show the RRs carried in a message as:
9823             </p>
9824 <div class="informaltable"><table border="1">
9825 <colgroup>
9826 <col>
9827 <col>
9828 <col>
9829 </colgroup>
9830 <tbody>
9831 <tr>
9832 <td>
9833                       <p>
9834                         <code class="literal">ISI.EDU.</code>
9835                       </p>
9836                     </td>
9837 <td>
9838                       <p>
9839                         <code class="literal">MX</code>
9840                       </p>
9841                     </td>
9842 <td>
9843                       <p>
9844                         <code class="literal">10 VENERA.ISI.EDU.</code>
9845                       </p>
9846                     </td>
9847 </tr>
9848 <tr>
9849 <td>
9850                       <p></p>
9851                     </td>
9852 <td>
9853                       <p>
9854                         <code class="literal">MX</code>
9855                       </p>
9856                     </td>
9857 <td>
9858                       <p>
9859                         <code class="literal">10 VAXA.ISI.EDU</code>
9860                       </p>
9861                     </td>
9862 </tr>
9863 <tr>
9864 <td>
9865                       <p>
9866                         <code class="literal">VENERA.ISI.EDU</code>
9867                       </p>
9868                     </td>
9869 <td>
9870                       <p>
9871                         <code class="literal">A</code>
9872                       </p>
9873                     </td>
9874 <td>
9875                       <p>
9876                         <code class="literal">128.9.0.32</code>
9877                       </p>
9878                     </td>
9879 </tr>
9880 <tr>
9881 <td>
9882                       <p></p>
9883                     </td>
9884 <td>
9885                       <p>
9886                         <code class="literal">A</code>
9887                       </p>
9888                     </td>
9889 <td>
9890                       <p>
9891                         <code class="literal">10.1.0.52</code>
9892                       </p>
9893                     </td>
9894 </tr>
9895 <tr>
9896 <td>
9897                       <p>
9898                         <code class="literal">VAXA.ISI.EDU</code>
9899                       </p>
9900                     </td>
9901 <td>
9902                       <p>
9903                         <code class="literal">A</code>
9904                       </p>
9905                     </td>
9906 <td>
9907                       <p>
9908                         <code class="literal">10.2.0.27</code>
9909                       </p>
9910                     </td>
9911 </tr>
9912 <tr>
9913 <td>
9914                       <p></p>
9915                     </td>
9916 <td>
9917                       <p>
9918                         <code class="literal">A</code>
9919                       </p>
9920                     </td>
9921 <td>
9922                       <p>
9923                         <code class="literal">128.9.0.33</code>
9924                       </p>
9925                     </td>
9926 </tr>
9927 </tbody>
9928 </table></div>
9929 <p>
9930               The MX RRs have an RDATA section which consists of a 16-bit
9931               number followed by a domain name.  The address RRs use a
9932               standard
9933               IP address format to contain a 32-bit internet address.
9934             </p>
9935 <p>
9936               The above example shows six RRs, with two RRs at each of three
9937               domain names.
9938             </p>
9939 <p>
9940               Similarly we might see:
9941             </p>
9942 <div class="informaltable"><table border="1">
9943 <colgroup>
9944 <col>
9945 <col>
9946 <col>
9947 </colgroup>
9948 <tbody>
9949 <tr>
9950 <td>
9951                       <p>
9952                         <code class="literal">XX.LCS.MIT.EDU.</code>
9953                       </p>
9954                     </td>
9955 <td>
9956                       <p>
9957                         <code class="literal">IN A</code>
9958                       </p>
9959                     </td>
9960 <td>
9961                       <p>
9962                         <code class="literal">10.0.0.44</code>
9963                       </p>
9964                     </td>
9965 </tr>
9966 <tr>
9967 <td> </td>
9968 <td>
9969                       <p>
9970                         <code class="literal">CH A</code>
9971                       </p>
9972                     </td>
9973 <td>
9974                       <p>
9975                         <code class="literal">MIT.EDU. 2420</code>
9976                       </p>
9977                     </td>
9978 </tr>
9979 </tbody>
9980 </table></div>
9981 <p>
9982               This example shows two addresses for
9983               <code class="literal">XX.LCS.MIT.EDU</code>, each of a different class.
9984             </p>
9985 </div>
9986 </div>
9987 <div class="sect2" lang="en">
9988 <div class="titlepage"><div><div><h3 class="title">
9989 <a name="id2600002"></a>Discussion of MX Records</h3></div></div></div>
9990 <p>
9991             As described above, domain servers store information as a
9992             series of resource records, each of which contains a particular
9993             piece of information about a given domain name (which is usually,
9994             but not always, a host). The simplest way to think of a RR is as
9995             a typed pair of data, a domain name matched with a relevant datum,
9996             and stored with some additional type information to help systems
9997             determine when the RR is relevant.
9998           </p>
9999 <p>
10000             MX records are used to control delivery of email. The data
10001             specified in the record is a priority and a domain name. The
10002             priority
10003             controls the order in which email delivery is attempted, with the
10004             lowest number first. If two priorities are the same, a server is
10005             chosen randomly. If no servers at a given priority are responding,
10006             the mail transport agent will fall back to the next largest
10007             priority.
10008             Priority numbers do not have any absolute meaning &#8212; they are
10009             relevant
10010             only respective to other MX records for that domain name. The
10011             domain
10012             name given is the machine to which the mail will be delivered.
10013             It <span class="emphasis"><em>must</em></span> have an associated address record
10014             (A or AAAA) &#8212; CNAME is not sufficient.
10015           </p>
10016 <p>
10017             For a given domain, if there is both a CNAME record and an
10018             MX record, the MX record is in error, and will be ignored.
10019             Instead,
10020             the mail will be delivered to the server specified in the MX
10021             record
10022             pointed to by the CNAME.
10023             For example:
10024           </p>
10025 <div class="informaltable"><table border="1">
10026 <colgroup>
10027 <col>
10028 <col>
10029 <col>
10030 <col>
10031 <col>
10032 </colgroup>
10033 <tbody>
10034 <tr>
10035 <td>
10036                     <p>
10037                       <code class="literal">example.com.</code>
10038                     </p>
10039                   </td>
10040 <td>
10041                     <p>
10042                       <code class="literal">IN</code>
10043                     </p>
10044                   </td>
10045 <td>
10046                     <p>
10047                       <code class="literal">MX</code>
10048                     </p>
10049                   </td>
10050 <td>
10051                     <p>
10052                       <code class="literal">10</code>
10053                     </p>
10054                   </td>
10055 <td>
10056                     <p>
10057                       <code class="literal">mail.example.com.</code>
10058                     </p>
10059                   </td>
10060 </tr>
10061 <tr>
10062 <td>
10063                     <p></p>
10064                   </td>
10065 <td>
10066                     <p>
10067                       <code class="literal">IN</code>
10068                     </p>
10069                   </td>
10070 <td>
10071                     <p>
10072                       <code class="literal">MX</code>
10073                     </p>
10074                   </td>
10075 <td>
10076                     <p>
10077                       <code class="literal">10</code>
10078                     </p>
10079                   </td>
10080 <td>
10081                     <p>
10082                       <code class="literal">mail2.example.com.</code>
10083                     </p>
10084                   </td>
10085 </tr>
10086 <tr>
10087 <td>
10088                     <p></p>
10089                   </td>
10090 <td>
10091                     <p>
10092                       <code class="literal">IN</code>
10093                     </p>
10094                   </td>
10095 <td>
10096                     <p>
10097                       <code class="literal">MX</code>
10098                     </p>
10099                   </td>
10100 <td>
10101                     <p>
10102                       <code class="literal">20</code>
10103                     </p>
10104                   </td>
10105 <td>
10106                     <p>
10107                       <code class="literal">mail.backup.org.</code>
10108                     </p>
10109                   </td>
10110 </tr>
10111 <tr>
10112 <td>
10113                     <p>
10114                       <code class="literal">mail.example.com.</code>
10115                     </p>
10116                   </td>
10117 <td>
10118                     <p>
10119                       <code class="literal">IN</code>
10120                     </p>
10121                   </td>
10122 <td>
10123                     <p>
10124                       <code class="literal">A</code>
10125                     </p>
10126                   </td>
10127 <td>
10128                     <p>
10129                       <code class="literal">10.0.0.1</code>
10130                     </p>
10131                   </td>
10132 <td>
10133                     <p></p>
10134                   </td>
10135 </tr>
10136 <tr>
10137 <td>
10138                     <p>
10139                       <code class="literal">mail2.example.com.</code>
10140                     </p>
10141                   </td>
10142 <td>
10143                     <p>
10144                       <code class="literal">IN</code>
10145                     </p>
10146                   </td>
10147 <td>
10148                     <p>
10149                       <code class="literal">A</code>
10150                     </p>
10151                   </td>
10152 <td>
10153                     <p>
10154                       <code class="literal">10.0.0.2</code>
10155                     </p>
10156                   </td>
10157 <td>
10158                     <p></p>
10159                   </td>
10160 </tr>
10161 </tbody>
10162 </table></div>
10163 <p>
10164             Mail delivery will be attempted to <code class="literal">mail.example.com</code> and
10165             <code class="literal">mail2.example.com</code> (in
10166             any order), and if neither of those succeed, delivery to <code class="literal">mail.backup.org</code> will
10167             be attempted.
10168           </p>
10169 </div>
10170 <div class="sect2" lang="en">
10171 <div class="titlepage"><div><div><h3 class="title">
10172 <a name="Setting_TTLs"></a>Setting TTLs</h3></div></div></div>
10173 <p>
10174             The time-to-live of the RR field is a 32-bit integer represented
10175             in units of seconds, and is primarily used by resolvers when they
10176             cache RRs. The TTL describes how long a RR can be cached before it
10177             should be discarded. The following three types of TTL are
10178             currently
10179             used in a zone file.
10180           </p>
10181 <div class="informaltable"><table border="1">
10182 <colgroup>
10183 <col>
10184 <col>
10185 </colgroup>
10186 <tbody>
10187 <tr>
10188 <td>
10189                     <p>
10190                       SOA
10191                     </p>
10192                   </td>
10193 <td>
10194                     <p>
10195                       The last field in the SOA is the negative
10196                       caching TTL. This controls how long other servers will
10197                       cache no-such-domain
10198                       (NXDOMAIN) responses from you.
10199                     </p>
10200                     <p>
10201                       The maximum time for
10202                       negative caching is 3 hours (3h).
10203                     </p>
10204                   </td>
10205 </tr>
10206 <tr>
10207 <td>
10208                     <p>
10209                       $TTL
10210                     </p>
10211                   </td>
10212 <td>
10213                     <p>
10214                       The $TTL directive at the top of the
10215                       zone file (before the SOA) gives a default TTL for every
10216                       RR without
10217                       a specific TTL set.
10218                     </p>
10219                   </td>
10220 </tr>
10221 <tr>
10222 <td>
10223                     <p>
10224                       RR TTLs
10225                     </p>
10226                   </td>
10227 <td>
10228                     <p>
10229                       Each RR can have a TTL as the second
10230                       field in the RR, which will control how long other
10231                       servers can cache it.
10232                     </p>
10233                   </td>
10234 </tr>
10235 </tbody>
10236 </table></div>
10237 <p>
10238             All of these TTLs default to units of seconds, though units
10239             can be explicitly specified, for example, <code class="literal">1h30m</code>.
10240           </p>
10241 </div>
10242 <div class="sect2" lang="en">
10243 <div class="titlepage"><div><div><h3 class="title">
10244 <a name="id2600549"></a>Inverse Mapping in IPv4</h3></div></div></div>
10245 <p>
10246             Reverse name resolution (that is, translation from IP address
10247             to name) is achieved by means of the <span class="emphasis"><em>in-addr.arpa</em></span> domain
10248             and PTR records. Entries in the in-addr.arpa domain are made in
10249             least-to-most significant order, read left to right. This is the
10250             opposite order to the way IP addresses are usually written. Thus,
10251             a machine with an IP address of 10.1.2.3 would have a
10252             corresponding
10253             in-addr.arpa name of
10254             3.2.1.10.in-addr.arpa. This name should have a PTR resource record
10255             whose data field is the name of the machine or, optionally,
10256             multiple
10257             PTR records if the machine has more than one name. For example,
10258             in the [<span class="optional">example.com</span>] domain:
10259           </p>
10260 <div class="informaltable"><table border="1">
10261 <colgroup>
10262 <col>
10263 <col>
10264 </colgroup>
10265 <tbody>
10266 <tr>
10267 <td>
10268                     <p>
10269                       <code class="literal">$ORIGIN</code>
10270                     </p>
10271                   </td>
10272 <td>
10273                     <p>
10274                       <code class="literal">2.1.10.in-addr.arpa</code>
10275                     </p>
10276                   </td>
10277 </tr>
10278 <tr>
10279 <td>
10280                     <p>
10281                       <code class="literal">3</code>
10282                     </p>
10283                   </td>
10284 <td>
10285                     <p>
10286                       <code class="literal">IN PTR foo.example.com.</code>
10287                     </p>
10288                   </td>
10289 </tr>
10290 </tbody>
10291 </table></div>
10292 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
10293 <h3 class="title">Note</h3>
10294 <p>
10295               The <span><strong class="command">$ORIGIN</strong></span> lines in the examples
10296               are for providing context to the examples only &#8212; they do not
10297               necessarily
10298               appear in the actual usage. They are only used here to indicate
10299               that the example is relative to the listed origin.
10300             </p>
10301 </div>
10302 </div>
10303 <div class="sect2" lang="en">
10304 <div class="titlepage"><div><div><h3 class="title">
10305 <a name="id2600812"></a>Other Zone File Directives</h3></div></div></div>
10306 <p>
10307             The Master File Format was initially defined in RFC 1035 and
10308             has subsequently been extended. While the Master File Format
10309             itself
10310             is class independent all records in a Master File must be of the
10311             same
10312             class.
10313           </p>
10314 <p>
10315             Master File Directives include <span><strong class="command">$ORIGIN</strong></span>, <span><strong class="command">$INCLUDE</strong></span>,
10316             and <span><strong class="command">$TTL.</strong></span>
10317           </p>
10318 <div class="sect3" lang="en">
10319 <div class="titlepage"><div><div><h4 class="title">
10320 <a name="id2600835"></a>The <span><strong class="command">@</strong></span> (at-sign)</h4></div></div></div>
10321 <p>
10322               When used in the label (or name) field, the asperand or
10323               at-sign (@) symbol represents the current origin.
10324               At the start of the zone file, it is the
10325               &lt;<code class="varname">zone_name</code>&gt; (followed by
10326               trailing dot).
10327             </p>
10328 </div>
10329 <div class="sect3" lang="en">
10330 <div class="titlepage"><div><div><h4 class="title">
10331 <a name="id2600851"></a>The <span><strong class="command">$ORIGIN</strong></span> Directive</h4></div></div></div>
10332 <p>
10333               Syntax: <span><strong class="command">$ORIGIN</strong></span>
10334               <em class="replaceable"><code>domain-name</code></em>
10335               [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
10336             </p>
10337 <p><span><strong class="command">$ORIGIN</strong></span>
10338               sets the domain name that will be appended to any
10339               unqualified records. When a zone is first read in there
10340               is an implicit <span><strong class="command">$ORIGIN</strong></span>
10341               &lt;<code class="varname">zone_name</code>&gt;<span><strong class="command">.</strong></span>
10342               (followed by trailing dot).
10343               The current <span><strong class="command">$ORIGIN</strong></span> is appended to
10344               the domain specified in the <span><strong class="command">$ORIGIN</strong></span>
10345               argument if it is not absolute.
10346             </p>
10347 <pre class="programlisting">
10348 $ORIGIN example.com.
10349 WWW     CNAME   MAIN-SERVER
10350 </pre>
10351 <p>
10352               is equivalent to
10353             </p>
10354 <pre class="programlisting">
10355 WWW.EXAMPLE.COM. CNAME MAIN-SERVER.EXAMPLE.COM.
10356 </pre>
10357 </div>
10358 <div class="sect3" lang="en">
10359 <div class="titlepage"><div><div><h4 class="title">
10360 <a name="id2600912"></a>The <span><strong class="command">$INCLUDE</strong></span> Directive</h4></div></div></div>
10361 <p>
10362               Syntax: <span><strong class="command">$INCLUDE</strong></span>
10363               <em class="replaceable"><code>filename</code></em>
10364               [<span class="optional">
10365 <em class="replaceable"><code>origin</code></em> </span>]
10366               [<span class="optional"> <em class="replaceable"><code>comment</code></em> </span>]
10367             </p>
10368 <p>
10369               Read and process the file <code class="filename">filename</code> as
10370               if it were included into the file at this point.  If <span><strong class="command">origin</strong></span> is
10371               specified the file is processed with <span><strong class="command">$ORIGIN</strong></span> set
10372               to that value, otherwise the current <span><strong class="command">$ORIGIN</strong></span> is
10373               used.
10374             </p>
10375 <p>
10376               The origin and the current domain name
10377               revert to the values they had prior to the <span><strong class="command">$INCLUDE</strong></span> once
10378               the file has been read.
10379             </p>
10380 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
10381 <h3 class="title">Note</h3>
10382 <p>
10383                 RFC 1035 specifies that the current origin should be restored
10384                 after
10385                 an <span><strong class="command">$INCLUDE</strong></span>, but it is silent
10386                 on whether the current
10387                 domain name should also be restored.  BIND 9 restores both of
10388                 them.
10389                 This could be construed as a deviation from RFC 1035, a
10390                 feature, or both.
10391               </p>
10392 </div>
10393 </div>
10394 <div class="sect3" lang="en">
10395 <div class="titlepage"><div><div><h4 class="title">
10396 <a name="id2600981"></a>The <span><strong class="command">$TTL</strong></span> Directive</h4></div></div></div>
10397 <p>
10398               Syntax: <span><strong class="command">$TTL</strong></span>
10399               <em class="replaceable"><code>default-ttl</code></em>
10400               [<span class="optional">
10401 <em class="replaceable"><code>comment</code></em> </span>]
10402             </p>
10403 <p>
10404               Set the default Time To Live (TTL) for subsequent records
10405               with undefined TTLs. Valid TTLs are of the range 0-2147483647
10406               seconds.
10407             </p>
10408 <p><span><strong class="command">$TTL</strong></span>
10409                is defined in RFC 2308.
10410             </p>
10411 </div>
10412 </div>
10413 <div class="sect2" lang="en">
10414 <div class="titlepage"><div><div><h3 class="title">
10415 <a name="id2601017"></a><acronym class="acronym">BIND</acronym> Master File Extension: the  <span><strong class="command">$GENERATE</strong></span> Directive</h3></div></div></div>
10416 <p>
10417             Syntax: <span><strong class="command">$GENERATE</strong></span>
10418             <em class="replaceable"><code>range</code></em>
10419             <em class="replaceable"><code>lhs</code></em>
10420             [<span class="optional"><em class="replaceable"><code>ttl</code></em></span>]
10421             [<span class="optional"><em class="replaceable"><code>class</code></em></span>]
10422             <em class="replaceable"><code>type</code></em>
10423             <em class="replaceable"><code>rhs</code></em>
10424             [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
10425           </p>
10426 <p><span><strong class="command">$GENERATE</strong></span>
10427             is used to create a series of resource records that only
10428             differ from each other by an
10429             iterator. <span><strong class="command">$GENERATE</strong></span> can be used to
10430             easily generate the sets of records required to support
10431             sub /24 reverse delegations described in RFC 2317:
10432             Classless IN-ADDR.ARPA delegation.
10433           </p>
10434 <pre class="programlisting">$ORIGIN 0.0.192.IN-ADDR.ARPA.
10435 $GENERATE 1-2 @ NS SERVER$.EXAMPLE.
10436 $GENERATE 1-127 $ CNAME $.0</pre>
10437 <p>
10438             is equivalent to
10439           </p>
10440 <pre class="programlisting">0.0.0.192.IN-ADDR.ARPA. NS SERVER1.EXAMPLE.
10441 0.0.0.192.IN-ADDR.ARPA. NS SERVER2.EXAMPLE.
10442 1.0.0.192.IN-ADDR.ARPA. CNAME 1.0.0.0.192.IN-ADDR.ARPA.
10443 2.0.0.192.IN-ADDR.ARPA. CNAME 2.0.0.0.192.IN-ADDR.ARPA.
10444 ...
10445 127.0.0.192.IN-ADDR.ARPA. CNAME 127.0.0.0.192.IN-ADDR.ARPA.
10446 </pre>
10447 <p>
10448             Generate a set of A and MX records.  Note the MX's right hand
10449             side is a quoted string.  The quotes will be stripped when the
10450             right hand side is processed.
10451            </p>
10452 <pre class="programlisting">
10453 $ORIGIN EXAMPLE.
10454 $GENERATE 1-127 HOST-$ A 1.2.3.$
10455 $GENERATE 1-127 HOST-$ MX "0 ."</pre>
10456 <p>
10457             is equivalent to
10458           </p>
10459 <pre class="programlisting">HOST-1.EXAMPLE.   A  1.2.3.1
10460 HOST-1.EXAMPLE.   MX 0 .
10461 HOST-2.EXAMPLE.   A  1.2.3.2
10462 HOST-2.EXAMPLE.   MX 0 .
10463 HOST-3.EXAMPLE.   A  1.2.3.3
10464 HOST-3.EXAMPLE.   MX 0 .
10465 ...
10466 HOST-127.EXAMPLE. A  1.2.3.127
10467 HOST-127.EXAMPLE. MX 0 .
10468 </pre>
10469 <div class="informaltable"><table border="1">
10470 <colgroup>
10471 <col>
10472 <col>
10473 </colgroup>
10474 <tbody>
10475 <tr>
10476 <td>
10477                     <p><span><strong class="command">range</strong></span></p>
10478                   </td>
10479 <td>
10480                     <p>
10481                       This can be one of two forms: start-stop
10482                       or start-stop/step. If the first form is used, then step
10483                       is set to 1. start, stop and step must be positive
10484                       integers between 0 and (2^31)-1. start must not be
10485                       larger than stop.
10486                     </p>
10487                   </td>
10488 </tr>
10489 <tr>
10490 <td>
10491                     <p><span><strong class="command">lhs</strong></span></p>
10492                   </td>
10493 <td>
10494                     <p>This
10495                       describes the owner name of the resource records
10496                       to be created.  Any single <span><strong class="command">$</strong></span>
10497                       (dollar sign)
10498                       symbols within the <span><strong class="command">lhs</strong></span> string
10499                       are replaced by the iterator value.
10500
10501                       To get a $ in the output, you need to escape the
10502                       <span><strong class="command">$</strong></span> using a backslash
10503                       <span><strong class="command">\</strong></span>,
10504                       e.g. <span><strong class="command">\$</strong></span>. The
10505                       <span><strong class="command">$</strong></span> may optionally be followed
10506                       by modifiers which change the offset from the
10507                       iterator, field width and base.
10508
10509                       Modifiers are introduced by a
10510                       <span><strong class="command">{</strong></span> (left brace) immediately following the
10511                       <span><strong class="command">$</strong></span> as
10512                       <span><strong class="command">${offset[,width[,base]]}</strong></span>.
10513                       For example, <span><strong class="command">${-20,3,d}</strong></span>
10514                       subtracts 20 from the current value, prints the
10515                       result as a decimal in a zero-padded field of
10516                       width 3.
10517
10518                       Available output forms are decimal
10519                       (<span><strong class="command">d</strong></span>), octal
10520                       (<span><strong class="command">o</strong></span>), hexadecimal
10521                       (<span><strong class="command">x</strong></span> or <span><strong class="command">X</strong></span>
10522                       for uppercase) and nibble
10523                       (<span><strong class="command">n</strong></span> or <span><strong class="command">N</strong></span>\
10524                       for uppercase).  The default modifier is
10525                       <span><strong class="command">${0,0,d}</strong></span>.  If the
10526                       <span><strong class="command">lhs</strong></span> is not absolute, the
10527                       current <span><strong class="command">$ORIGIN</strong></span> is appended
10528                       to the name.
10529                     </p>
10530                     <p>
10531                       In nibble mode the value will be treated as
10532                       if it was a reversed hexadecimal string
10533                       with each hexadecimal digit as a separate
10534                       label.  The width field includes the label
10535                       separator.
10536                     </p>
10537                     <p>
10538                       For compatibility with earlier versions,
10539                       <span><strong class="command">$$</strong></span> is still recognized as
10540                       indicating a literal $ in the output.
10541                     </p>
10542                   </td>
10543 </tr>
10544 <tr>
10545 <td>
10546                     <p><span><strong class="command">ttl</strong></span></p>
10547                   </td>
10548 <td>
10549                     <p>
10550                       Specifies the time-to-live of the generated records. If
10551                       not specified this will be inherited using the
10552                       normal TTL inheritance rules.
10553                     </p>
10554                     <p><span><strong class="command">class</strong></span>
10555                       and <span><strong class="command">ttl</strong></span> can be
10556                       entered in either order.
10557                     </p>
10558                   </td>
10559 </tr>
10560 <tr>
10561 <td>
10562                     <p><span><strong class="command">class</strong></span></p>
10563                   </td>
10564 <td>
10565                     <p>
10566                       Specifies the class of the generated records.
10567                       This must match the zone class if it is
10568                       specified.
10569                     </p>
10570                     <p><span><strong class="command">class</strong></span>
10571                       and <span><strong class="command">ttl</strong></span> can be
10572                       entered in either order.
10573                     </p>
10574                   </td>
10575 </tr>
10576 <tr>
10577 <td>
10578                     <p><span><strong class="command">type</strong></span></p>
10579                   </td>
10580 <td>
10581                     <p>
10582                       Any valid type.
10583                     </p>
10584                   </td>
10585 </tr>
10586 <tr>
10587 <td>
10588                     <p><span><strong class="command">rhs</strong></span></p>
10589                   </td>
10590 <td>
10591                     <p>
10592                       <span><strong class="command">rhs</strong></span>, optionally, quoted string.
10593                     </p>
10594                   </td>
10595 </tr>
10596 </tbody>
10597 </table></div>
10598 <p>
10599             The <span><strong class="command">$GENERATE</strong></span> directive is a <acronym class="acronym">BIND</acronym> extension
10600             and not part of the standard zone file format.
10601           </p>
10602 <p>
10603             BIND 8 does not support the optional TTL and CLASS fields.
10604           </p>
10605 </div>
10606 <div class="sect2" lang="en">
10607 <div class="titlepage"><div><div><h3 class="title">
10608 <a name="zonefile_format"></a>Additional File Formats</h3></div></div></div>
10609 <p>
10610             In addition to the standard textual format, BIND 9
10611             supports the ability to read or dump to zone files in
10612             other formats.  The <code class="constant">raw</code> format is
10613             currently available as an additional format.  It is a
10614             binary format representing BIND 9's internal data
10615             structure directly, thereby remarkably improving the
10616             loading time.
10617           </p>
10618 <p>
10619             For a primary server, a zone file in the
10620             <code class="constant">raw</code> format is expected to be
10621             generated from a textual zone file by the
10622             <span><strong class="command">named-compilezone</strong></span> command.  For a
10623             secondary server or for a dynamic zone, it is automatically
10624             generated (if this format is specified by the
10625             <span><strong class="command">masterfile-format</strong></span> option) when
10626             <span><strong class="command">named</strong></span> dumps the zone contents after
10627             zone transfer or when applying prior updates.
10628           </p>
10629 <p>
10630             If a zone file in a binary format needs manual modification,
10631             it first must be converted to a textual form by the
10632             <span><strong class="command">named-compilezone</strong></span> command.  All
10633             necessary modification should go to the text file, which
10634             should then be converted to the binary form by the
10635             <span><strong class="command">named-compilezone</strong></span> command again.
10636           </p>
10637 <p>
10638              Although the <code class="constant">raw</code> format uses the
10639              network byte order and avoids architecture-dependent
10640              data alignment so that it is as much portable as
10641              possible, it is primarily expected to be used inside
10642              the same single system.  In order to export a zone
10643              file in the <code class="constant">raw</code> format or make a
10644              portable backup of the file, it is recommended to
10645              convert the file to the standard textual representation.
10646           </p>
10647 </div>
10648 </div>
10649 <div class="sect1" lang="en">
10650 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
10651 <a name="statistics"></a>BIND9 Statistics</h2></div></div></div>
10652 <p>
10653           <acronym class="acronym">BIND</acronym> 9 maintains lots of statistics
10654           information and provides several interfaces for users to
10655           get access to the statistics.
10656           The available statistics include all statistics counters
10657           that were available in <acronym class="acronym">BIND</acronym> 8 and
10658           are meaningful in <acronym class="acronym">BIND</acronym> 9,
10659           and other information that is considered useful.
10660         </p>
10661 <p>
10662           The statistics information is categorized into the following
10663           sections.
10664         </p>
10665 <div class="informaltable"><table border="1">
10666 <colgroup>
10667 <col>
10668 <col>
10669 </colgroup>
10670 <tbody>
10671 <tr>
10672 <td>
10673                   <p>Incoming Requests</p>
10674                 </td>
10675 <td>
10676                   <p>
10677                     The number of incoming DNS requests for each OPCODE.
10678                   </p>
10679                 </td>
10680 </tr>
10681 <tr>
10682 <td>
10683                   <p>Incoming Queries</p>
10684                 </td>
10685 <td>
10686                   <p>
10687                     The number of incoming queries for each RR type.
10688                   </p>
10689                 </td>
10690 </tr>
10691 <tr>
10692 <td>
10693                   <p>Outgoing Queries</p>
10694                 </td>
10695 <td>
10696                   <p>
10697                     The number of outgoing queries for each RR
10698                     type sent from the internal resolver.
10699                     Maintained per view.
10700                   </p>
10701                 </td>
10702 </tr>
10703 <tr>
10704 <td>
10705                   <p>Name Server Statistics</p>
10706                 </td>
10707 <td>
10708                   <p>
10709                     Statistics counters about incoming request processing.
10710                   </p>
10711                 </td>
10712 </tr>
10713 <tr>
10714 <td>
10715                   <p>Zone Maintenance Statistics</p>
10716                 </td>
10717 <td>
10718                   <p>
10719                     Statistics counters regarding zone maintenance
10720                     operations such as zone transfers.
10721                   </p>
10722                 </td>
10723 </tr>
10724 <tr>
10725 <td>
10726                   <p>Resolver Statistics</p>
10727                 </td>
10728 <td>
10729                   <p>
10730                     Statistics counters about name resolution
10731                     performed in the internal resolver.
10732                     Maintained per view.
10733                   </p>
10734                 </td>
10735 </tr>
10736 <tr>
10737 <td>
10738                   <p>Cache DB RRsets</p>
10739                 </td>
10740 <td>
10741                   <p>
10742                     The number of RRsets per RR type and nonexistent
10743                     names stored in the cache database.
10744                     If the exclamation mark (!) is printed for a RR
10745                     type, it means that particular type of RRset is
10746                     known to be nonexistent (this is also known as
10747                     "NXRRSET").
10748                     Maintained per view.
10749                   </p>
10750                 </td>
10751 </tr>
10752 <tr>
10753 <td>
10754                   <p>Socket I/O Statistics</p>
10755                 </td>
10756 <td>
10757                   <p>
10758                     Statistics counters about network related events.
10759                   </p>
10760                 </td>
10761 </tr>
10762 </tbody>
10763 </table></div>
10764 <p>
10765           A subset of Name Server Statistics is collected and shown
10766           per zone for which the server has the authority when
10767           <span><strong class="command">zone-statistics</strong></span> is set to
10768           <strong class="userinput"><code>yes</code></strong>.
10769           These statistics counters are shown with their zone and view
10770           names.
10771           In some cases the view names are omitted for the default view.
10772         </p>
10773 <p>
10774           There are currently two user interfaces to get access to the
10775           statistics.
10776           One is in the plain text format dumped to the file specified
10777           by the <span><strong class="command">statistics-file</strong></span> configuration option.
10778           The other is remotely accessible via a statistics channel
10779           when the <span><strong class="command">statistics-channels</strong></span> statement
10780           is specified in the configuration file
10781           (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>.)
10782         </p>
10783 <div class="sect3" lang="en">
10784 <div class="titlepage"><div><div><h4 class="title">
10785 <a name="statsfile"></a>The Statistics File</h4></div></div></div>
10786 <p>
10787             The text format statistics dump begins with a line, like:
10788           </p>
10789 <p>
10790             <span><strong class="command">+++ Statistics Dump +++ (973798949)</strong></span>
10791           </p>
10792 <p>
10793             The number in parentheses is a standard
10794             Unix-style timestamp, measured as seconds since January 1, 1970.
10795
10796             Following
10797             that line is a set of statistics information, which is categorized
10798             as described above.
10799             Each section begins with a line, like:
10800           </p>
10801 <p>
10802             <span><strong class="command">++ Name Server Statistics ++</strong></span>
10803           </p>
10804 <p>
10805             Each section consists of lines, each containing the statistics
10806             counter value followed by its textual description.
10807             See below for available counters.
10808             For brevity, counters that have a value of 0 are not shown
10809             in the statistics file.
10810           </p>
10811 <p>
10812             The statistics dump ends with the line where the
10813             number is identical to the number in the beginning line; for example:
10814           </p>
10815 <p>
10816             <span><strong class="command">--- Statistics Dump --- (973798949)</strong></span>
10817           </p>
10818 </div>
10819 <div class="sect2" lang="en">
10820 <div class="titlepage"><div><div><h3 class="title">
10821 <a name="statistics_counters"></a>Statistics Counters</h3></div></div></div>
10822 <p>
10823             The following tables summarize statistics counters that
10824             <acronym class="acronym">BIND</acronym> 9 provides.
10825             For each row of the tables, the leftmost column is the
10826             abbreviated symbol name of that counter.
10827             These symbols are shown in the statistics information
10828             accessed via an HTTP statistics channel.
10829             The rightmost column gives the description of the counter,
10830             which is also shown in the statistics file
10831             (but, in this document, possibly with slight modification
10832             for better readability).
10833             Additional notes may also be provided in this column.
10834             When a middle column exists between these two columns,
10835             it gives the corresponding counter name of the
10836             <acronym class="acronym">BIND</acronym> 8 statistics, if applicable.
10837           </p>
10838 <div class="sect3" lang="en">
10839 <div class="titlepage"><div><div><h4 class="title">
10840 <a name="id2602039"></a>Name Server Statistics Counters</h4></div></div></div>
10841 <div class="informaltable"><table border="1">
10842 <colgroup>
10843 <col>
10844 <col>
10845 <col>
10846 </colgroup>
10847 <tbody>
10848 <tr>
10849 <td>
10850                       <p>
10851                         <span class="emphasis"><em>Symbol</em></span>
10852                       </p>
10853                     </td>
10854 <td>
10855                       <p>
10856                         <span class="emphasis"><em>BIND8 Symbol</em></span>
10857                       </p>
10858                     </td>
10859 <td>
10860                       <p>
10861                         <span class="emphasis"><em>Description</em></span>
10862                       </p>
10863                     </td>
10864 </tr>
10865 <tr>
10866 <td>
10867                       <p><span><strong class="command">Requestv4</strong></span></p>
10868                     </td>
10869 <td>
10870                       <p><span><strong class="command">RQ</strong></span></p>
10871                     </td>
10872 <td>
10873                       <p>
10874                         IPv4 requests received.
10875                         Note: this also counts non query requests.
10876                       </p>
10877                     </td>
10878 </tr>
10879 <tr>
10880 <td>
10881                       <p><span><strong class="command">Requestv6</strong></span></p>
10882                     </td>
10883 <td>
10884                       <p><span><strong class="command">RQ</strong></span></p>
10885                     </td>
10886 <td>
10887                       <p>
10888                         IPv6 requests received.
10889                         Note: this also counts non query requests.
10890                       </p>
10891                     </td>
10892 </tr>
10893 <tr>
10894 <td>
10895                       <p><span><strong class="command">ReqEdns0</strong></span></p>
10896                     </td>
10897 <td>
10898                       <p><span><strong class="command"></strong></span></p>
10899                     </td>
10900 <td>
10901                       <p>
10902                         Requests with EDNS(0) received.
10903                       </p>
10904                     </td>
10905 </tr>
10906 <tr>
10907 <td>
10908                       <p><span><strong class="command">ReqBadEDNSVer</strong></span></p>
10909                     </td>
10910 <td>
10911                       <p><span><strong class="command"></strong></span></p>
10912                     </td>
10913 <td>
10914                       <p>
10915                         Requests with unsupported EDNS version received.
10916                       </p>
10917                     </td>
10918 </tr>
10919 <tr>
10920 <td>
10921                       <p><span><strong class="command">ReqTSIG</strong></span></p>
10922                     </td>
10923 <td>
10924                       <p><span><strong class="command"></strong></span></p>
10925                     </td>
10926 <td>
10927                       <p>
10928                         Requests with TSIG received.
10929                       </p>
10930                     </td>
10931 </tr>
10932 <tr>
10933 <td>
10934                       <p><span><strong class="command">ReqSIG0</strong></span></p>
10935                     </td>
10936 <td>
10937                       <p><span><strong class="command"></strong></span></p>
10938                     </td>
10939 <td>
10940                       <p>
10941                         Requests with SIG(0) received.
10942                       </p>
10943                     </td>
10944 </tr>
10945 <tr>
10946 <td>
10947                       <p><span><strong class="command">ReqBadSIG</strong></span></p>
10948                     </td>
10949 <td>
10950                       <p><span><strong class="command"></strong></span></p>
10951                     </td>
10952 <td>
10953                       <p>
10954                         Requests with invalid (TSIG or SIG(0)) signature.
10955                       </p>
10956                     </td>
10957 </tr>
10958 <tr>
10959 <td>
10960                       <p><span><strong class="command">ReqTCP</strong></span></p>
10961                     </td>
10962 <td>
10963                       <p><span><strong class="command">RTCP</strong></span></p>
10964                     </td>
10965 <td>
10966                       <p>
10967                         TCP requests received.
10968                       </p>
10969                     </td>
10970 </tr>
10971 <tr>
10972 <td>
10973                       <p><span><strong class="command">AuthQryRej</strong></span></p>
10974                     </td>
10975 <td>
10976                       <p><span><strong class="command">RUQ</strong></span></p>
10977                     </td>
10978 <td>
10979                       <p>
10980                         Authoritative (non recursive) queries rejected.
10981                       </p>
10982                     </td>
10983 </tr>
10984 <tr>
10985 <td>
10986                       <p><span><strong class="command">RecQryRej</strong></span></p>
10987                     </td>
10988 <td>
10989                       <p><span><strong class="command">RURQ</strong></span></p>
10990                     </td>
10991 <td>
10992                       <p>
10993                         Recursive queries rejected.
10994                       </p>
10995                     </td>
10996 </tr>
10997 <tr>
10998 <td>
10999                       <p><span><strong class="command">XfrRej</strong></span></p>
11000                     </td>
11001 <td>
11002                       <p><span><strong class="command">RUXFR</strong></span></p>
11003                     </td>
11004 <td>
11005                       <p>
11006                         Zone transfer requests rejected.
11007                       </p>
11008                     </td>
11009 </tr>
11010 <tr>
11011 <td>
11012                       <p><span><strong class="command">UpdateRej</strong></span></p>
11013                     </td>
11014 <td>
11015                       <p><span><strong class="command">RUUpd</strong></span></p>
11016                     </td>
11017 <td>
11018                       <p>
11019                         Dynamic update requests rejected.
11020                       </p>
11021                     </td>
11022 </tr>
11023 <tr>
11024 <td>
11025                       <p><span><strong class="command">Response</strong></span></p>
11026                     </td>
11027 <td>
11028                       <p><span><strong class="command">SAns</strong></span></p>
11029                     </td>
11030 <td>
11031                       <p>
11032                         Responses sent.
11033                       </p>
11034                     </td>
11035 </tr>
11036 <tr>
11037 <td>
11038                       <p><span><strong class="command">RespTruncated</strong></span></p>
11039                     </td>
11040 <td>
11041                       <p><span><strong class="command"></strong></span></p>
11042                     </td>
11043 <td>
11044                       <p>
11045                         Truncated responses sent.
11046                       </p>
11047                     </td>
11048 </tr>
11049 <tr>
11050 <td>
11051                       <p><span><strong class="command">RespEDNS0</strong></span></p>
11052                     </td>
11053 <td>
11054                       <p><span><strong class="command"></strong></span></p>
11055                     </td>
11056 <td>
11057                       <p>
11058                         Responses with EDNS(0) sent.
11059                       </p>
11060                     </td>
11061 </tr>
11062 <tr>
11063 <td>
11064                       <p><span><strong class="command">RespTSIG</strong></span></p>
11065                     </td>
11066 <td>
11067                       <p><span><strong class="command"></strong></span></p>
11068                     </td>
11069 <td>
11070                       <p>
11071                         Responses with TSIG sent.
11072                       </p>
11073                     </td>
11074 </tr>
11075 <tr>
11076 <td>
11077                       <p><span><strong class="command">RespSIG0</strong></span></p>
11078                     </td>
11079 <td>
11080                       <p><span><strong class="command"></strong></span></p>
11081                     </td>
11082 <td>
11083                       <p>
11084                         Responses with SIG(0) sent.
11085                       </p>
11086                     </td>
11087 </tr>
11088 <tr>
11089 <td>
11090                       <p><span><strong class="command">QrySuccess</strong></span></p>
11091                     </td>
11092 <td>
11093                       <p><span><strong class="command"></strong></span></p>
11094                     </td>
11095 <td>
11096                       <p>
11097                         Queries resulted in a successful answer.
11098                         This means the query which returns a NOERROR response
11099                         with at least one answer RR.
11100                         This corresponds to the
11101                         <span><strong class="command">success</strong></span> counter
11102                         of previous versions of
11103                         <acronym class="acronym">BIND</acronym> 9.
11104                       </p>
11105                     </td>
11106 </tr>
11107 <tr>
11108 <td>
11109                       <p><span><strong class="command">QryAuthAns</strong></span></p>
11110                     </td>
11111 <td>
11112                       <p><span><strong class="command"></strong></span></p>
11113                     </td>
11114 <td>
11115                       <p>
11116                         Queries resulted in authoritative answer.
11117                       </p>
11118                     </td>
11119 </tr>
11120 <tr>
11121 <td>
11122                       <p><span><strong class="command">QryNoauthAns</strong></span></p>
11123                     </td>
11124 <td>
11125                       <p><span><strong class="command">SNaAns</strong></span></p>
11126                     </td>
11127 <td>
11128                       <p>
11129                         Queries resulted in non authoritative answer.
11130                       </p>
11131                     </td>
11132 </tr>
11133 <tr>
11134 <td>
11135                       <p><span><strong class="command">QryReferral</strong></span></p>
11136                     </td>
11137 <td>
11138                       <p><span><strong class="command"></strong></span></p>
11139                     </td>
11140 <td>
11141                       <p>
11142                         Queries resulted in referral answer.
11143                         This corresponds to the
11144                         <span><strong class="command">referral</strong></span> counter
11145                         of previous versions of
11146                         <acronym class="acronym">BIND</acronym> 9.
11147                       </p>
11148                     </td>
11149 </tr>
11150 <tr>
11151 <td>
11152                       <p><span><strong class="command">QryNxrrset</strong></span></p>
11153                     </td>
11154 <td>
11155                       <p><span><strong class="command"></strong></span></p>
11156                     </td>
11157 <td>
11158                       <p>
11159                         Queries resulted in NOERROR responses with no data.
11160                         This corresponds to the
11161                         <span><strong class="command">nxrrset</strong></span> counter
11162                         of previous versions of
11163                         <acronym class="acronym">BIND</acronym> 9.
11164                       </p>
11165                     </td>
11166 </tr>
11167 <tr>
11168 <td>
11169                       <p><span><strong class="command">QrySERVFAIL</strong></span></p>
11170                     </td>
11171 <td>
11172                       <p><span><strong class="command">SFail</strong></span></p>
11173                     </td>
11174 <td>
11175                       <p>
11176                         Queries resulted in SERVFAIL.
11177                       </p>
11178                     </td>
11179 </tr>
11180 <tr>
11181 <td>
11182                       <p><span><strong class="command">QryFORMERR</strong></span></p>
11183                     </td>
11184 <td>
11185                       <p><span><strong class="command">SFErr</strong></span></p>
11186                     </td>
11187 <td>
11188                       <p>
11189                         Queries resulted in FORMERR.
11190                       </p>
11191                     </td>
11192 </tr>
11193 <tr>
11194 <td>
11195                       <p><span><strong class="command">QryNXDOMAIN</strong></span></p>
11196                     </td>
11197 <td>
11198                       <p><span><strong class="command">SNXD</strong></span></p>
11199                     </td>
11200 <td>
11201                       <p>
11202                         Queries resulted in NXDOMAIN.
11203                         This corresponds to the
11204                         <span><strong class="command">nxdomain</strong></span> counter
11205                         of previous versions of
11206                         <acronym class="acronym">BIND</acronym> 9.
11207                       </p>
11208                     </td>
11209 </tr>
11210 <tr>
11211 <td>
11212                       <p><span><strong class="command">QryRecursion</strong></span></p>
11213                     </td>
11214 <td>
11215                       <p><span><strong class="command">RFwdQ</strong></span></p>
11216                     </td>
11217 <td>
11218                       <p>
11219                         Queries which caused the server
11220                         to perform recursion in order to find the final answer.
11221                         This corresponds to the
11222                         <span><strong class="command">recursion</strong></span> counter
11223                         of previous versions of
11224                         <acronym class="acronym">BIND</acronym> 9.
11225                       </p>
11226                     </td>
11227 </tr>
11228 <tr>
11229 <td>
11230                       <p><span><strong class="command">QryDuplicate</strong></span></p>
11231                     </td>
11232 <td>
11233                       <p><span><strong class="command">RDupQ</strong></span></p>
11234                     </td>
11235 <td>
11236                       <p>
11237                         Queries which the server attempted to
11238                         recurse but discovered an existing query with the same
11239                         IP address, port, query ID, name, type and class
11240                         already being processed.
11241                         This corresponds to the
11242                         <span><strong class="command">duplicate</strong></span> counter
11243                         of previous versions of
11244                         <acronym class="acronym">BIND</acronym> 9.
11245                       </p>
11246                     </td>
11247 </tr>
11248 <tr>
11249 <td>
11250                       <p><span><strong class="command">QryDropped</strong></span></p>
11251                     </td>
11252 <td>
11253                       <p><span><strong class="command"></strong></span></p>
11254                     </td>
11255 <td>
11256                       <p>
11257                         Recursive queries for which the server
11258                         discovered an excessive number of existing
11259                         recursive queries for the same name, type and
11260                         class and were subsequently dropped.
11261                         This is the number of dropped queries due to
11262                         the reason explained with the
11263                         <span><strong class="command">clients-per-query</strong></span>
11264                         and
11265                         <span><strong class="command">max-clients-per-query</strong></span>
11266                         options
11267                         (see the description about
11268                         <a href="Bv9ARM.ch06.html#clients-per-query"><span><strong class="command">clients-per-query</strong></span></a>.)
11269                         This corresponds to the
11270                         <span><strong class="command">dropped</strong></span> counter
11271                         of previous versions of
11272                         <acronym class="acronym">BIND</acronym> 9.
11273                       </p>
11274                     </td>
11275 </tr>
11276 <tr>
11277 <td>
11278                       <p><span><strong class="command">QryFailure</strong></span></p>
11279                     </td>
11280 <td>
11281                       <p><span><strong class="command"></strong></span></p>
11282                     </td>
11283 <td>
11284                       <p>
11285                         Other query failures.
11286                         This corresponds to the
11287                         <span><strong class="command">failure</strong></span> counter
11288                         of previous versions of
11289                         <acronym class="acronym">BIND</acronym> 9.
11290                         Note: this counter is provided mainly for
11291                         backward compatibility with the previous versions.
11292                         Normally a more fine-grained counters such as
11293                         <span><strong class="command">AuthQryRej</strong></span> and
11294                         <span><strong class="command">RecQryRej</strong></span>
11295                         that would also fall into this counter are provided,
11296                         and so this counter would not be of much
11297                         interest in practice.
11298                       </p>
11299                     </td>
11300 </tr>
11301 <tr>
11302 <td>
11303                       <p><span><strong class="command">XfrReqDone</strong></span></p>
11304                     </td>
11305 <td>
11306                       <p><span><strong class="command"></strong></span></p>
11307                     </td>
11308 <td>
11309                       <p>
11310                         Requested zone transfers completed.
11311                       </p>
11312                     </td>
11313 </tr>
11314 <tr>
11315 <td>
11316                       <p><span><strong class="command">UpdateReqFwd</strong></span></p>
11317                     </td>
11318 <td>
11319                       <p><span><strong class="command"></strong></span></p>
11320                     </td>
11321 <td>
11322                       <p>
11323                         Update requests forwarded.
11324                       </p>
11325                     </td>
11326 </tr>
11327 <tr>
11328 <td>
11329                       <p><span><strong class="command">UpdateRespFwd</strong></span></p>
11330                     </td>
11331 <td>
11332                       <p><span><strong class="command"></strong></span></p>
11333                     </td>
11334 <td>
11335                       <p>
11336                         Update responses forwarded.
11337                       </p>
11338                     </td>
11339 </tr>
11340 <tr>
11341 <td>
11342                       <p><span><strong class="command">UpdateFwdFail</strong></span></p>
11343                     </td>
11344 <td>
11345                       <p><span><strong class="command"></strong></span></p>
11346                     </td>
11347 <td>
11348                       <p>
11349                         Dynamic update forward failed.
11350                       </p>
11351                     </td>
11352 </tr>
11353 <tr>
11354 <td>
11355                       <p><span><strong class="command">UpdateDone</strong></span></p>
11356                     </td>
11357 <td>
11358                       <p><span><strong class="command"></strong></span></p>
11359                     </td>
11360 <td>
11361                       <p>
11362                         Dynamic updates completed.
11363                       </p>
11364                     </td>
11365 </tr>
11366 <tr>
11367 <td>
11368                       <p><span><strong class="command">UpdateFail</strong></span></p>
11369                     </td>
11370 <td>
11371                       <p><span><strong class="command"></strong></span></p>
11372                     </td>
11373 <td>
11374                       <p>
11375                         Dynamic updates failed.
11376                       </p>
11377                     </td>
11378 </tr>
11379 <tr>
11380 <td>
11381                       <p><span><strong class="command">UpdateBadPrereq</strong></span></p>
11382                     </td>
11383 <td>
11384                       <p><span><strong class="command"></strong></span></p>
11385                     </td>
11386 <td>
11387                       <p>
11388                         Dynamic updates rejected due to prerequisite failure.
11389                       </p>
11390                     </td>
11391 </tr>
11392 <tr>
11393 <td>
11394                       <p><span><strong class="command">RPZRewrites</strong></span></p>
11395                     </td>
11396 <td>
11397                       <p><span><strong class="command"></strong></span></p>
11398                     </td>
11399 <td>
11400                       <p>
11401                         Response policy zone rewrites.
11402                       </p>
11403                     </td>
11404 </tr>
11405 <tr>
11406 <td>
11407                       <p><span><strong class="command">RateDropped</strong></span></p>
11408                     </td>
11409 <td>
11410                       <p><span><strong class="command"></strong></span></p>
11411                     </td>
11412 <td>
11413                       <p>
11414                         Responses dropped by rate limits.
11415                       </p>
11416                     </td>
11417 </tr>
11418 <tr>
11419 <td>
11420                       <p><span><strong class="command">RateSlipped</strong></span></p>
11421                     </td>
11422 <td>
11423                       <p><span><strong class="command"></strong></span></p>
11424                     </td>
11425 <td>
11426                       <p>
11427                         Responses truncated by rate limits.
11428                       </p>
11429                     </td>
11430 </tr>
11431 </tbody>
11432 </table></div>
11433 </div>
11434 <div class="sect3" lang="en">
11435 <div class="titlepage"><div><div><h4 class="title">
11436 <a name="id2603745"></a>Zone Maintenance Statistics Counters</h4></div></div></div>
11437 <div class="informaltable"><table border="1">
11438 <colgroup>
11439 <col>
11440 <col>
11441 </colgroup>
11442 <tbody>
11443 <tr>
11444 <td>
11445                       <p>
11446                         <span class="emphasis"><em>Symbol</em></span>
11447                       </p>
11448                     </td>
11449 <td>
11450                       <p>
11451                         <span class="emphasis"><em>Description</em></span>
11452                       </p>
11453                     </td>
11454 </tr>
11455 <tr>
11456 <td>
11457                       <p><span><strong class="command">NotifyOutv4</strong></span></p>
11458                     </td>
11459 <td>
11460                       <p>
11461                         IPv4 notifies sent.
11462                       </p>
11463                     </td>
11464 </tr>
11465 <tr>
11466 <td>
11467                       <p><span><strong class="command">NotifyOutv6</strong></span></p>
11468                     </td>
11469 <td>
11470                       <p>
11471                         IPv6 notifies sent.
11472                       </p>
11473                     </td>
11474 </tr>
11475 <tr>
11476 <td>
11477                       <p><span><strong class="command">NotifyInv4</strong></span></p>
11478                     </td>
11479 <td>
11480                       <p>
11481                         IPv4 notifies received.
11482                       </p>
11483                     </td>
11484 </tr>
11485 <tr>
11486 <td>
11487                       <p><span><strong class="command">NotifyInv6</strong></span></p>
11488                     </td>
11489 <td>
11490                       <p>
11491                         IPv6 notifies received.
11492                       </p>
11493                     </td>
11494 </tr>
11495 <tr>
11496 <td>
11497                       <p><span><strong class="command">NotifyRej</strong></span></p>
11498                     </td>
11499 <td>
11500                       <p>
11501                         Incoming notifies rejected.
11502                       </p>
11503                     </td>
11504 </tr>
11505 <tr>
11506 <td>
11507                       <p><span><strong class="command">SOAOutv4</strong></span></p>
11508                     </td>
11509 <td>
11510                       <p>
11511                         IPv4 SOA queries sent.
11512                       </p>
11513                     </td>
11514 </tr>
11515 <tr>
11516 <td>
11517                       <p><span><strong class="command">SOAOutv6</strong></span></p>
11518                     </td>
11519 <td>
11520                       <p>
11521                         IPv6 SOA queries sent.
11522                       </p>
11523                     </td>
11524 </tr>
11525 <tr>
11526 <td>
11527                       <p><span><strong class="command">AXFRReqv4</strong></span></p>
11528                     </td>
11529 <td>
11530                       <p>
11531                         IPv4 AXFR requested.
11532                       </p>
11533                     </td>
11534 </tr>
11535 <tr>
11536 <td>
11537                       <p><span><strong class="command">AXFRReqv6</strong></span></p>
11538                     </td>
11539 <td>
11540                       <p>
11541                         IPv6 AXFR requested.
11542                       </p>
11543                     </td>
11544 </tr>
11545 <tr>
11546 <td>
11547                       <p><span><strong class="command">IXFRReqv4</strong></span></p>
11548                     </td>
11549 <td>
11550                       <p>
11551                         IPv4 IXFR requested.
11552                       </p>
11553                     </td>
11554 </tr>
11555 <tr>
11556 <td>
11557                       <p><span><strong class="command">IXFRReqv6</strong></span></p>
11558                     </td>
11559 <td>
11560                       <p>
11561                         IPv6 IXFR requested.
11562                       </p>
11563                     </td>
11564 </tr>
11565 <tr>
11566 <td>
11567                       <p><span><strong class="command">XfrSuccess</strong></span></p>
11568                     </td>
11569 <td>
11570                       <p>
11571                         Zone transfer requests succeeded.
11572                       </p>
11573                     </td>
11574 </tr>
11575 <tr>
11576 <td>
11577                       <p><span><strong class="command">XfrFail</strong></span></p>
11578                     </td>
11579 <td>
11580                       <p>
11581                         Zone transfer requests failed.
11582                       </p>
11583                     </td>
11584 </tr>
11585 </tbody>
11586 </table></div>
11587 </div>
11588 <div class="sect3" lang="en">
11589 <div class="titlepage"><div><div><h4 class="title">
11590 <a name="id2604128"></a>Resolver Statistics Counters</h4></div></div></div>
11591 <div class="informaltable"><table border="1">
11592 <colgroup>
11593 <col>
11594 <col>
11595 <col>
11596 </colgroup>
11597 <tbody>
11598 <tr>
11599 <td>
11600                       <p>
11601                         <span class="emphasis"><em>Symbol</em></span>
11602                       </p>
11603                     </td>
11604 <td>
11605                       <p>
11606                         <span class="emphasis"><em>BIND8 Symbol</em></span>
11607                       </p>
11608                     </td>
11609 <td>
11610                       <p>
11611                         <span class="emphasis"><em>Description</em></span>
11612                       </p>
11613                     </td>
11614 </tr>
11615 <tr>
11616 <td>
11617                       <p><span><strong class="command">Queryv4</strong></span></p>
11618                     </td>
11619 <td>
11620                       <p><span><strong class="command">SFwdQ</strong></span></p>
11621                     </td>
11622 <td>
11623                       <p>
11624                         IPv4 queries sent.
11625                       </p>
11626                     </td>
11627 </tr>
11628 <tr>
11629 <td>
11630                       <p><span><strong class="command">Queryv6</strong></span></p>
11631                     </td>
11632 <td>
11633                       <p><span><strong class="command">SFwdQ</strong></span></p>
11634                     </td>
11635 <td>
11636                       <p>
11637                         IPv6 queries sent.
11638                       </p>
11639                     </td>
11640 </tr>
11641 <tr>
11642 <td>
11643                       <p><span><strong class="command">Responsev4</strong></span></p>
11644                     </td>
11645 <td>
11646                       <p><span><strong class="command">RR</strong></span></p>
11647                     </td>
11648 <td>
11649                       <p>
11650                         IPv4 responses received.
11651                       </p>
11652                     </td>
11653 </tr>
11654 <tr>
11655 <td>
11656                       <p><span><strong class="command">Responsev6</strong></span></p>
11657                     </td>
11658 <td>
11659                       <p><span><strong class="command">RR</strong></span></p>
11660                     </td>
11661 <td>
11662                       <p>
11663                         IPv6 responses received.
11664                       </p>
11665                     </td>
11666 </tr>
11667 <tr>
11668 <td>
11669                       <p><span><strong class="command">NXDOMAIN</strong></span></p>
11670                     </td>
11671 <td>
11672                       <p><span><strong class="command">RNXD</strong></span></p>
11673                     </td>
11674 <td>
11675                       <p>
11676                         NXDOMAIN received.
11677                       </p>
11678                     </td>
11679 </tr>
11680 <tr>
11681 <td>
11682                       <p><span><strong class="command">SERVFAIL</strong></span></p>
11683                     </td>
11684 <td>
11685                       <p><span><strong class="command">RFail</strong></span></p>
11686                     </td>
11687 <td>
11688                       <p>
11689                         SERVFAIL received.
11690                       </p>
11691                     </td>
11692 </tr>
11693 <tr>
11694 <td>
11695                       <p><span><strong class="command">FORMERR</strong></span></p>
11696                     </td>
11697 <td>
11698                       <p><span><strong class="command">RFErr</strong></span></p>
11699                     </td>
11700 <td>
11701                       <p>
11702                         FORMERR received.
11703                       </p>
11704                     </td>
11705 </tr>
11706 <tr>
11707 <td>
11708                       <p><span><strong class="command">OtherError</strong></span></p>
11709                     </td>
11710 <td>
11711                       <p><span><strong class="command">RErr</strong></span></p>
11712                     </td>
11713 <td>
11714                       <p>
11715                         Other errors received.
11716                       </p>
11717                     </td>
11718 </tr>
11719 <tr>
11720 <td>
11721                       <p><span><strong class="command">EDNS0Fail</strong></span></p>
11722                                                  </td>
11723 <td>
11724                       <p><span><strong class="command"></strong></span></p>
11725                     </td>
11726 <td>
11727                       <p>
11728                         EDNS(0) query failures.
11729                       </p>
11730                     </td>
11731 </tr>
11732 <tr>
11733 <td>
11734                       <p><span><strong class="command">Mismatch</strong></span></p>
11735                     </td>
11736 <td>
11737                       <p><span><strong class="command">RDupR</strong></span></p>
11738                     </td>
11739 <td>
11740                       <p>
11741                         Mismatch responses received.
11742                         The DNS ID, response's source address,
11743                         and/or the response's source port does not
11744                         match what was expected.
11745                         (The port must be 53 or as defined by
11746                         the <span><strong class="command">port</strong></span> option.)
11747                         This may be an indication of a cache
11748                         poisoning attempt.
11749                       </p>
11750                     </td>
11751 </tr>
11752 <tr>
11753 <td>
11754                       <p><span><strong class="command">Truncated</strong></span></p>
11755                     </td>
11756 <td>
11757                       <p><span><strong class="command"></strong></span></p>
11758                     </td>
11759 <td>
11760                       <p>
11761                         Truncated responses received.
11762                       </p>
11763                     </td>
11764 </tr>
11765 <tr>
11766 <td>
11767                       <p><span><strong class="command">Lame</strong></span></p>
11768                     </td>
11769 <td>
11770                       <p><span><strong class="command">RLame</strong></span></p>
11771                     </td>
11772 <td>
11773                       <p>
11774                         Lame delegations received.
11775                       </p>
11776                     </td>
11777 </tr>
11778 <tr>
11779 <td>
11780                       <p><span><strong class="command">Retry</strong></span></p>
11781                     </td>
11782 <td>
11783                       <p><span><strong class="command">SDupQ</strong></span></p>
11784                     </td>
11785 <td>
11786                       <p>
11787                         Query retries performed.
11788                       </p>
11789                     </td>
11790 </tr>
11791 <tr>
11792 <td>
11793                       <p><span><strong class="command">QueryAbort</strong></span></p>
11794                     </td>
11795 <td>
11796                       <p><span><strong class="command"></strong></span></p>
11797                     </td>
11798 <td>
11799                       <p>
11800                         Queries aborted due to quota control.
11801                       </p>
11802                     </td>
11803 </tr>
11804 <tr>
11805 <td>
11806                       <p><span><strong class="command">QuerySockFail</strong></span></p>
11807                     </td>
11808 <td>
11809                       <p><span><strong class="command"></strong></span></p>
11810                     </td>
11811 <td>
11812                       <p>
11813                         Failures in opening query sockets.
11814                         One common reason for such failures is a
11815                         failure of opening a new socket due to a
11816                         limitation on file descriptors.
11817                       </p>
11818                     </td>
11819 </tr>
11820 <tr>
11821 <td>
11822                       <p><span><strong class="command">QueryTimeout</strong></span></p>
11823                     </td>
11824 <td>
11825                       <p><span><strong class="command"></strong></span></p>
11826                     </td>
11827 <td>
11828                       <p>
11829                         Query timeouts.
11830                       </p>
11831                     </td>
11832 </tr>
11833 <tr>
11834 <td>
11835                       <p><span><strong class="command">GlueFetchv4</strong></span></p>
11836                     </td>
11837 <td>
11838                       <p><span><strong class="command">SSysQ</strong></span></p>
11839                     </td>
11840 <td>
11841                       <p>
11842                         IPv4 NS address fetches invoked.
11843                       </p>
11844                     </td>
11845 </tr>
11846 <tr>
11847 <td>
11848                       <p><span><strong class="command">GlueFetchv6</strong></span></p>
11849                     </td>
11850 <td>
11851                       <p><span><strong class="command">SSysQ</strong></span></p>
11852                     </td>
11853 <td>
11854                       <p>
11855                         IPv6 NS address fetches invoked.
11856                       </p>
11857                     </td>
11858 </tr>
11859 <tr>
11860 <td>
11861                       <p><span><strong class="command">GlueFetchv4Fail</strong></span></p>
11862                     </td>
11863 <td>
11864                       <p><span><strong class="command"></strong></span></p>
11865                     </td>
11866 <td>
11867                       <p>
11868                         IPv4 NS address fetch failed.
11869                       </p>
11870                     </td>
11871 </tr>
11872 <tr>
11873 <td>
11874                       <p><span><strong class="command">GlueFetchv6Fail</strong></span></p>
11875                     </td>
11876 <td>
11877                       <p><span><strong class="command"></strong></span></p>
11878                     </td>
11879 <td>
11880                       <p>
11881                         IPv6 NS address fetch failed.
11882                       </p>
11883                     </td>
11884 </tr>
11885 <tr>
11886 <td>
11887                       <p><span><strong class="command">ValAttempt</strong></span></p>
11888                     </td>
11889 <td>
11890                       <p><span><strong class="command"></strong></span></p>
11891                     </td>
11892 <td>
11893                       <p>
11894                         DNSSEC validation attempted.
11895                       </p>
11896                     </td>
11897 </tr>
11898 <tr>
11899 <td>
11900                       <p><span><strong class="command">ValOk</strong></span></p>
11901                     </td>
11902 <td>
11903                       <p><span><strong class="command"></strong></span></p>
11904                     </td>
11905 <td>
11906                       <p>
11907                         DNSSEC validation succeeded.
11908                       </p>
11909                     </td>
11910 </tr>
11911 <tr>
11912 <td>
11913                       <p><span><strong class="command">ValNegOk</strong></span></p>
11914                     </td>
11915 <td>
11916                       <p><span><strong class="command"></strong></span></p>
11917                     </td>
11918 <td>
11919                       <p>
11920                         DNSSEC validation on negative information succeeded.
11921                       </p>
11922                     </td>
11923 </tr>
11924 <tr>
11925 <td>
11926                       <p><span><strong class="command">ValFail</strong></span></p>
11927                     </td>
11928 <td>
11929                       <p><span><strong class="command"></strong></span></p>
11930                     </td>
11931 <td>
11932                       <p>
11933                         DNSSEC validation failed.
11934                       </p>
11935                     </td>
11936 </tr>
11937 <tr>
11938 <td>
11939                       <p><span><strong class="command">QryRTTnn</strong></span></p>
11940                     </td>
11941 <td>
11942                       <p><span><strong class="command"></strong></span></p>
11943                     </td>
11944 <td>
11945                       <p>
11946                         Frequency table on round trip times (RTTs) of
11947                         queries.
11948                         Each <span><strong class="command">nn</strong></span> specifies the corresponding
11949                         frequency.
11950                         In the sequence of
11951                         <span><strong class="command">nn_1</strong></span>,
11952                         <span><strong class="command">nn_2</strong></span>,
11953                         ...,
11954                         <span><strong class="command">nn_m</strong></span>,
11955                         the value of <span><strong class="command">nn_i</strong></span> is the
11956                         number of queries whose RTTs are between
11957                         <span><strong class="command">nn_(i-1)</strong></span> (inclusive) and
11958                         <span><strong class="command">nn_i</strong></span> (exclusive) milliseconds.
11959                         For the sake of convenience we define
11960                         <span><strong class="command">nn_0</strong></span> to be 0.
11961                         The last entry should be represented as
11962                         <span><strong class="command">nn_m+</strong></span>, which means the
11963                         number of queries whose RTTs are equal to or over
11964                         <span><strong class="command">nn_m</strong></span> milliseconds.
11965                       </p>
11966                     </td>
11967 </tr>
11968 </tbody>
11969 </table></div>
11970 </div>
11971 <div class="sect3" lang="en">
11972 <div class="titlepage"><div><div><h4 class="title">
11973 <a name="id2605149"></a>Socket I/O Statistics Counters</h4></div></div></div>
11974 <p>
11975               Socket I/O statistics counters are defined per socket
11976               types, which are
11977               <span><strong class="command">UDP4</strong></span> (UDP/IPv4),
11978               <span><strong class="command">UDP6</strong></span> (UDP/IPv6),
11979               <span><strong class="command">TCP4</strong></span> (TCP/IPv4),
11980               <span><strong class="command">TCP6</strong></span> (TCP/IPv6),
11981               <span><strong class="command">Unix</strong></span> (Unix Domain), and
11982               <span><strong class="command">FDwatch</strong></span> (sockets opened outside the
11983               socket module).
11984               In the following table <span><strong class="command">&lt;TYPE&gt;</strong></span>
11985               represents a socket type.
11986               Not all counters are available for all socket types;
11987               exceptions are noted in the description field.
11988             </p>
11989 <div class="informaltable"><table border="1">
11990 <colgroup>
11991 <col>
11992 <col>
11993 </colgroup>
11994 <tbody>
11995 <tr>
11996 <td>
11997                       <p>
11998                         <span class="emphasis"><em>Symbol</em></span>
11999                       </p>
12000                     </td>
12001 <td>
12002                       <p>
12003                         <span class="emphasis"><em>Description</em></span>
12004                       </p>
12005                     </td>
12006 </tr>
12007 <tr>
12008 <td>
12009                       <p><span><strong class="command">&lt;TYPE&gt;Open</strong></span></p>
12010                     </td>
12011 <td>
12012                       <p>
12013                         Sockets opened successfully.
12014                         This counter is not applicable to the
12015                         <span><strong class="command">FDwatch</strong></span> type.
12016                       </p>
12017                     </td>
12018 </tr>
12019 <tr>
12020 <td>
12021                       <p><span><strong class="command">&lt;TYPE&gt;OpenFail</strong></span></p>
12022                     </td>
12023 <td>
12024                       <p>
12025                         Failures of opening sockets.
12026                         This counter is not applicable to the
12027                         <span><strong class="command">FDwatch</strong></span> type.
12028                       </p>
12029                     </td>
12030 </tr>
12031 <tr>
12032 <td>
12033                       <p><span><strong class="command">&lt;TYPE&gt;Close</strong></span></p>
12034                     </td>
12035 <td>
12036                       <p>
12037                         Sockets closed.
12038                       </p>
12039                     </td>
12040 </tr>
12041 <tr>
12042 <td>
12043                       <p><span><strong class="command">&lt;TYPE&gt;BindFail</strong></span></p>
12044                     </td>
12045 <td>
12046                       <p>
12047                         Failures of binding sockets.
12048                       </p>
12049                     </td>
12050 </tr>
12051 <tr>
12052 <td>
12053                       <p><span><strong class="command">&lt;TYPE&gt;ConnFail</strong></span></p>
12054                     </td>
12055 <td>
12056                       <p>
12057                         Failures of connecting sockets.
12058                       </p>
12059                     </td>
12060 </tr>
12061 <tr>
12062 <td>
12063                       <p><span><strong class="command">&lt;TYPE&gt;Conn</strong></span></p>
12064                     </td>
12065 <td>
12066                       <p>
12067                         Connections established successfully.
12068                       </p>
12069                     </td>
12070 </tr>
12071 <tr>
12072 <td>
12073                       <p><span><strong class="command">&lt;TYPE&gt;AcceptFail</strong></span></p>
12074                     </td>
12075 <td>
12076                       <p>
12077                         Failures of accepting incoming connection requests.
12078                         This counter is not applicable to the
12079                         <span><strong class="command">UDP</strong></span> and
12080                         <span><strong class="command">FDwatch</strong></span> types.
12081                       </p>
12082                     </td>
12083 </tr>
12084 <tr>
12085 <td>
12086                       <p><span><strong class="command">&lt;TYPE&gt;Accept</strong></span></p>
12087                     </td>
12088 <td>
12089                       <p>
12090                         Incoming connections successfully accepted.
12091                         This counter is not applicable to the
12092                         <span><strong class="command">UDP</strong></span> and
12093                         <span><strong class="command">FDwatch</strong></span> types.
12094                       </p>
12095                     </td>
12096 </tr>
12097 <tr>
12098 <td>
12099                       <p><span><strong class="command">&lt;TYPE&gt;SendErr</strong></span></p>
12100                     </td>
12101 <td>
12102                       <p>
12103                         Errors in socket send operations.
12104                         This counter corresponds
12105                         to <span><strong class="command">SErr</strong></span> counter of
12106                         <span><strong class="command">BIND</strong></span> 8.
12107                       </p>
12108                     </td>
12109 </tr>
12110 <tr>
12111 <td>
12112                       <p><span><strong class="command">&lt;TYPE&gt;RecvErr</strong></span></p>
12113                     </td>
12114 <td>
12115                       <p>
12116                         Errors in socket receive operations.
12117                         This includes errors of send operations on a
12118                         connected UDP socket notified by an ICMP error
12119                         message.
12120                       </p>
12121                     </td>
12122 </tr>
12123 </tbody>
12124 </table></div>
12125 </div>
12126 <div class="sect3" lang="en">
12127 <div class="titlepage"><div><div><h4 class="title">
12128 <a name="id2605523"></a>Compatibility with <span class="emphasis"><em>BIND</em></span> 8 Counters</h4></div></div></div>
12129 <p>
12130               Most statistics counters that were available
12131               in <span><strong class="command">BIND</strong></span> 8 are also supported in
12132               <span><strong class="command">BIND</strong></span> 9 as shown in the above tables.
12133               Here are notes about other counters that do not appear
12134               in these tables.
12135             </p>
12136 <div class="variablelist"><dl>
12137 <dt><span class="term"><span><strong class="command">RFwdR,SFwdR</strong></span></span></dt>
12138 <dd><p>
12139                     These counters are not supported
12140                     because <span><strong class="command">BIND</strong></span> 9 does not adopt
12141                     the notion of <span class="emphasis"><em>forwarding</em></span>
12142                     as <span><strong class="command">BIND</strong></span> 8 did.
12143                   </p></dd>
12144 <dt><span class="term"><span><strong class="command">RAXFR</strong></span></span></dt>
12145 <dd><p>
12146                     This counter is accessible in the Incoming Queries section.
12147                   </p></dd>
12148 <dt><span class="term"><span><strong class="command">RIQ</strong></span></span></dt>
12149 <dd><p>
12150                     This counter is accessible in the Incoming Requests section.
12151                   </p></dd>
12152 <dt><span class="term"><span><strong class="command">ROpts</strong></span></span></dt>
12153 <dd><p>
12154                     This counter is not supported
12155                     because <span><strong class="command">BIND</strong></span> 9 does not care
12156                     about IP options in the first place.
12157                   </p></dd>
12158 </dl></div>
12159 </div>
12160 </div>
12161 </div>
12162 </div>
12163 <div class="navfooter">
12164 <hr>
12165 <table width="100%" summary="Navigation footer">
12166 <tr>
12167 <td width="40%" align="left">
12168 <a accesskey="p" href="Bv9ARM.ch05.html">Prev</a> </td>
12169 <td width="20%" align="center"> </td>
12170 <td width="40%" align="right"> <a accesskey="n" href="Bv9ARM.ch07.html">Next</a>
12171 </td>
12172 </tr>
12173 <tr>
12174 <td width="40%" align="left" valign="top">Chapter 5. The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver </td>
12175 <td width="20%" align="center"><a accesskey="h" href="Bv9ARM.html">Home</a></td>
12176 <td width="40%" align="right" valign="top"> Chapter 7. <acronym class="acronym">BIND</acronym> 9 Security Considerations</td>
12177 </tr>
12178 </table>
12179 </div>
12180 <p style="text-align: center;">BIND 9.9.8-P3 (Extended Support Version)</p>
12181 </body>
12182 </html>