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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#id2574283">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#id2574937"><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#id2575127"><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#id2575418"><span><strong class="command">include</strong></span> Statement Grammar</a></span></dt>
  62 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575504"><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#id2575527"><span><strong class="command">key</strong></span> Statement Grammar</a></span></dt>
  65 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575550"><span><strong class="command">key</strong></span> Statement Definition and Usage</a></span></dt>
  66 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575709"><span><strong class="command">logging</strong></span> Statement Grammar</a></span></dt>
  67 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575835"><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#id2577834"><span><strong class="command">lwres</strong></span> Statement Grammar</a></span></dt>
  70 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577908"><span><strong class="command">lwres</strong></span> Statement Definition and Usage</a></span></dt>
  71 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2578040"><span><strong class="command">masters</strong></span> Statement Grammar</a></span></dt>
  72 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2578084"><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#id2578099"><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#id2589395"><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#id2589534"><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#id2589581"><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#id2590007"><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#id2591558"><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#id2595030">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#id2597260">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#id2597876">Inverse Mapping in IPv4</a></span></dt>
 101 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2598003">Other Zone File Directives</a></span></dt>
 102 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2598276"><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 number, the word <strong class="userinput"><code>unlimited</code></strong>,
 413                   or the word <strong class="userinput"><code>default</code></strong>.
 414                 </p>
 415                 <p>
 416                   An <code class="varname">unlimited</code> <code class="varname">size_spec</code> requests unlimited
 417                   use, or the maximum available amount. A <code class="varname">default size_spec</code> uses
 418                   the limit that was in force when the server was started.
 419                 </p>
 420                 <p>
 421                   A <code class="varname">number</code> can optionally be
 422                   followed by a scaling factor:
 423                   <strong class="userinput"><code>K</code></strong> or <strong class="userinput"><code>k</code></strong>
 424                   for kilobytes,
 425                   <strong class="userinput"><code>M</code></strong> or <strong class="userinput"><code>m</code></strong>
 426                   for megabytes, and
 427                   <strong class="userinput"><code>G</code></strong> or <strong class="userinput"><code>g</code></strong> for gigabytes,
 428                   which scale by 1024, 1024*1024, and 1024*1024*1024
 429                   respectively.
 430                 </p>
 431                 <p>
 432                   The value must be representable as a 64-bit unsigned integer
 433                   (0 to 18446744073709551615, inclusive).
 434                   Using <code class="varname">unlimited</code> is the best
 435                   way
 436                   to safely set a really large number.
 437                 </p>
 438               </td>
 439 </tr>
 440 <tr>
 441 <td>
 442                 <p>
 443                   <code class="varname">yes_or_no</code>
 444                 </p>
 445               </td>
 446 <td>
 447                 <p>
 448                   Either <strong class="userinput"><code>yes</code></strong> or <strong class="userinput"><code>no</code></strong>.
 449                   The words <strong class="userinput"><code>true</code></strong> and <strong class="userinput"><code>false</code></strong> are
 450                   also accepted, as are the numbers <strong class="userinput"><code>1</code></strong>
 451                   and <strong class="userinput"><code>0</code></strong>.
 452                 </p>
 453               </td>
 454 </tr>
 455 <tr>
 456 <td>
 457                 <p>
 458                   <code class="varname">dialup_option</code>
 459                 </p>
 460               </td>
 461 <td>
 462                 <p>
 463                   One of <strong class="userinput"><code>yes</code></strong>,
 464                   <strong class="userinput"><code>no</code></strong>, <strong class="userinput"><code>notify</code></strong>,
 465                   <strong class="userinput"><code>notify-passive</code></strong>, <strong class="userinput"><code>refresh</code></strong> or
 466                   <strong class="userinput"><code>passive</code></strong>.
 467                   When used in a zone, <strong class="userinput"><code>notify-passive</code></strong>,
 468                   <strong class="userinput"><code>refresh</code></strong>, and <strong class="userinput"><code>passive</code></strong>
 469                   are restricted to slave and stub zones.
 470                 </p>
 471               </td>
 472 </tr>
 473 </tbody>
 474 </table></div>
 475 <div class="sect2" lang="en">
 476 <div class="titlepage"><div><div><h3 class="title">
 477 <a name="address_match_lists"></a>Address Match Lists</h3></div></div></div>
 478 <div class="sect3" lang="en">
 479 <div class="titlepage"><div><div><h4 class="title">
 480 <a name="id2574050"></a>Syntax</h4></div></div></div>
 481 <pre class="programlisting"><code class="varname">address_match_list</code> = address_match_list_element ;
 482   [<span class="optional"> address_match_list_element; ... </span>]
 483 <code class="varname">address_match_list_element</code> = [<span class="optional"> ! </span>] (ip_address [<span class="optional">/length</span>] |
 484    key key_id | acl_name | { address_match_list } )
 485 </pre>
 486 </div>
 487 <div class="sect3" lang="en">
 488 <div class="titlepage"><div><div><h4 class="title">
 489 <a name="id2574077"></a>Definition and Usage</h4></div></div></div>
 490 <p>
 491             Address match lists are primarily used to determine access
 492             control for various server operations. They are also used in
 493             the <span><strong class="command">listen-on</strong></span> and <span><strong class="command">sortlist</strong></span>
 494             statements. The elements which constitute an address match
 495             list can be any of the following:
 496           </p>
 497 <div class="itemizedlist"><ul type="disc">
 498 <li>an IP address (IPv4 or IPv6)</li>
 499 <li>an IP prefix (in `/' notation)</li>
 500 <li>
 501                 a key ID, as defined by the <span><strong class="command">key</strong></span>
 502                 statement
 503               </li>
 504 <li>the name of an address match list defined with
 505                 the <span><strong class="command">acl</strong></span> statement
 506               </li>
 507 <li>a nested address match list enclosed in braces</li>
 508 </ul></div>
 509 <p>
 510             Elements can be negated with a leading exclamation mark (`!'),
 511             and the match list names "any", "none", "localhost", and
 512             "localnets" are predefined. More information on those names
 513             can be found in the description of the acl statement.
 514           </p>
 515 <p>
 516             The addition of the key clause made the name of this syntactic
 517             element something of a misnomer, since security keys can be used
 518             to validate access without regard to a host or network address.
 519             Nonetheless, the term "address match list" is still used
 520             throughout the documentation.
 521           </p>
 522 <p>
 523             When a given IP address or prefix is compared to an address
 524             match list, the comparison takes place in approximately O(1)
 525             time.  However, key comparisons require that the list of keys
 526             be traversed until a matching key is found, and therefore may
 527             be somewhat slower.
 528           </p>
 529 <p>
 530             The interpretation of a match depends on whether the list is being
 531             used for access control, defining <span><strong class="command">listen-on</strong></span> ports, or in a
 532             <span><strong class="command">sortlist</strong></span>, and whether the element was negated.
 533           </p>
 534 <p>
 535             When used as an access control list, a non-negated match
 536             allows access and a negated match denies access. If
 537             there is no match, access is denied. The clauses
 538             <span><strong class="command">allow-notify</strong></span>,
 539             <span><strong class="command">allow-recursion</strong></span>,
 540             <span><strong class="command">allow-recursion-on</strong></span>,
 541             <span><strong class="command">allow-query</strong></span>,
 542             <span><strong class="command">allow-query-on</strong></span>,
 543             <span><strong class="command">allow-query-cache</strong></span>,
 544             <span><strong class="command">allow-query-cache-on</strong></span>,
 545             <span><strong class="command">allow-transfer</strong></span>,
 546             <span><strong class="command">allow-update</strong></span>,
 547             <span><strong class="command">allow-update-forwarding</strong></span>, and
 548             <span><strong class="command">blackhole</strong></span> all use address match
 549             lists.  Similarly, the <span><strong class="command">listen-on</strong></span> option will cause the
 550             server to refuse queries on any of the machine's
 551             addresses which do not match the list.
 552           </p>
 553 <p>
 554             Order of insertion is significant.  If more than one element
 555             in an ACL is found to match a given IP address or prefix,
 556             preference will be given to the one that came
 557             <span class="emphasis"><em>first</em></span> in the ACL definition.
 558             Because of this first-match behavior, an element that
 559             defines a subset of another element in the list should
 560             come before the broader element, regardless of whether
 561             either is negated. For example, in
 562             <span><strong class="command">1.2.3/24; ! 1.2.3.13;</strong></span>
 563             the 1.2.3.13 element is completely useless because the
 564             algorithm will match any lookup for 1.2.3.13 to the 1.2.3/24
 565             element.  Using <span><strong class="command">! 1.2.3.13; 1.2.3/24</strong></span> fixes
 566             that problem by having 1.2.3.13 blocked by the negation, but
 567             all other 1.2.3.* hosts fall through.
 568           </p>
 569 </div>
 570 </div>
 571 <div class="sect2" lang="en">
 572 <div class="titlepage"><div><div><h3 class="title">
 573 <a name="id2574283"></a>Comment Syntax</h3></div></div></div>
 574 <p>
 575           The <acronym class="acronym">BIND</acronym> 9 comment syntax allows for
 576           comments to appear
 577           anywhere that whitespace may appear in a <acronym class="acronym">BIND</acronym> configuration
 578           file. To appeal to programmers of all kinds, they can be written
 579           in the C, C++, or shell/perl style.
 580         </p>
 581 <div class="sect3" lang="en">
 582 <div class="titlepage"><div><div><h4 class="title">
 583 <a name="id2574298"></a>Syntax</h4></div></div></div>
 584 <p>
 585             </p>
 586 <pre class="programlisting">/* This is a <acronym class="acronym">BIND</acronym> comment as in C */</pre>
 587 <p>
 588             </p>
 589 <pre class="programlisting">// This is a <acronym class="acronym">BIND</acronym> comment as in C++</pre>
 590 <p>
 591             </p>
 592 <pre class="programlisting"># This is a <acronym class="acronym">BIND</acronym> comment as in common UNIX shells
 593 # and perl</pre>
 594 <p>
 595           </p>
 596 </div>
 597 <div class="sect3" lang="en">
 598 <div class="titlepage"><div><div><h4 class="title">
 599 <a name="id2574328"></a>Definition and Usage</h4></div></div></div>
 600 <p>
 601             Comments may appear anywhere that whitespace may appear in
 602             a <acronym class="acronym">BIND</acronym> configuration file.
 603           </p>
 604 <p>
 605             C-style comments start with the two characters /* (slash,
 606             star) and end with */ (star, slash). Because they are completely
 607             delimited with these characters, they can be used to comment only
 608             a portion of a line or to span multiple lines.
 609           </p>
 610 <p>
 611             C-style comments cannot be nested. For example, the following
 612             is not valid because the entire comment ends with the first */:
 613           </p>
 614 <p>
 615
 616 </p>
 617 <pre class="programlisting">/* This is the start of a comment.
 618    This is still part of the comment.
 619 /* This is an incorrect attempt at nesting a comment. */
 620    This is no longer in any comment. */
 621 </pre>
 622 <p>
 623
 624           </p>
 625 <p>
 626             C++-style comments start with the two characters // (slash,
 627             slash) and continue to the end of the physical line. They cannot
 628             be continued across multiple physical lines; to have one logical
 629             comment span multiple lines, each line must use the // pair.
 630             For example:
 631           </p>
 632 <p>
 633
 634 </p>
 635 <pre class="programlisting">// This is the start of a comment.  The next line
 636 // is a new comment, even though it is logically
 637 // part of the previous comment.
 638 </pre>
 639 <p>
 640
 641           </p>
 642 <p>
 643             Shell-style (or perl-style, if you prefer) comments start
 644             with the character <code class="literal">#</code> (number sign)
 645             and continue to the end of the
 646             physical line, as in C++ comments.
 647             For example:
 648           </p>
 649 <p>
 650
 651 </p>
 652 <pre class="programlisting"># This is the start of a comment.  The next line
 653 # is a new comment, even though it is logically
 654 # part of the previous comment.
 655 </pre>
 656 <p>
 657
 658           </p>
 659 <div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
 660 <h3 class="title">Warning</h3>
 661 <p>
 662               You cannot use the semicolon (`;') character
 663               to start a comment such as you would in a zone file. The
 664               semicolon indicates the end of a configuration
 665               statement.
 666             </p>
 667 </div>
 668 </div>
 669 </div>
 670 </div>
 671 <div class="sect1" lang="en">
 672 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
 673 <a name="Configuration_File_Grammar"></a>Configuration File Grammar</h2></div></div></div>
 674 <p>
 675         A <acronym class="acronym">BIND</acronym> 9 configuration consists of
 676         statements and comments.
 677         Statements end with a semicolon. Statements and comments are the
 678         only elements that can appear without enclosing braces. Many
 679         statements contain a block of sub-statements, which are also
 680         terminated with a semicolon.
 681       </p>
 682 <p>
 683         The following statements are supported:
 684       </p>
 685 <div class="informaltable"><table border="1">
 686 <colgroup>
 687 <col>
 688 <col>
 689 </colgroup>
 690 <tbody>
 691 <tr>
 692 <td>
 693                 <p><span><strong class="command">acl</strong></span></p>
 694               </td>
 695 <td>
 696                 <p>
 697                   defines a named IP address
 698                   matching list, for access control and other uses.
 699                 </p>
 700               </td>
 701 </tr>
 702 <tr>
 703 <td>
 704                 <p><span><strong class="command">controls</strong></span></p>
 705               </td>
 706 <td>
 707                 <p>
 708                   declares control channels to be used
 709                   by the <span><strong class="command">rndc</strong></span> utility.
 710                 </p>
 711               </td>
 712 </tr>
 713 <tr>
 714 <td>
 715                 <p><span><strong class="command">include</strong></span></p>
 716               </td>
 717 <td>
 718                 <p>
 719                   includes a file.
 720                 </p>
 721               </td>
 722 </tr>
 723 <tr>
 724 <td>
 725                 <p><span><strong class="command">key</strong></span></p>
 726               </td>
 727 <td>
 728                 <p>
 729                   specifies key information for use in
 730                   authentication and authorization using TSIG.
 731                 </p>
 732               </td>
 733 </tr>
 734 <tr>
 735 <td>
 736                 <p><span><strong class="command">logging</strong></span></p>
 737               </td>
 738 <td>
 739                 <p>
 740                   specifies what the server logs, and where
 741                   the log messages are sent.
 742                 </p>
 743               </td>
 744 </tr>
 745 <tr>
 746 <td>
 747                 <p><span><strong class="command">lwres</strong></span></p>
 748               </td>
 749 <td>
 750                 <p>
 751                   configures <span><strong class="command">named</strong></span> to
 752                   also act as a light-weight resolver daemon (<span><strong class="command">lwresd</strong></span>).
 753                 </p>
 754               </td>
 755 </tr>
 756 <tr>
 757 <td>
 758                 <p><span><strong class="command">masters</strong></span></p>
 759               </td>
 760 <td>
 761                 <p>
 762                   defines a named masters list for
 763                   inclusion in stub and slave zone masters clauses.
 764                 </p>
 765               </td>
 766 </tr>
 767 <tr>
 768 <td>
 769                 <p><span><strong class="command">options</strong></span></p>
 770               </td>
 771 <td>
 772                 <p>
 773                   controls global server configuration
 774                   options and sets defaults for other statements.
 775                 </p>
 776               </td>
 777 </tr>
 778 <tr>
 779 <td>
 780                 <p><span><strong class="command">server</strong></span></p>
 781               </td>
 782 <td>
 783                 <p>
 784                   sets certain configuration options on
 785                   a per-server basis.
 786                 </p>
 787               </td>
 788 </tr>
 789 <tr>
 790 <td>
 791                 <p><span><strong class="command">statistics-channels</strong></span></p>
 792               </td>
 793 <td>
 794                 <p>
 795                   declares communication channels to get access to
 796                   <span><strong class="command">named</strong></span> statistics.
 797                 </p>
 798               </td>
 799 </tr>
 800 <tr>
 801 <td>
 802                 <p><span><strong class="command">trusted-keys</strong></span></p>
 803               </td>
 804 <td>
 805                 <p>
 806                   defines trusted DNSSEC keys.
 807                 </p>
 808               </td>
 809 </tr>
 810 <tr>
 811 <td>
 812                 <p><span><strong class="command">managed-keys</strong></span></p>
 813               </td>
 814 <td>
 815                 <p>
 816                   lists DNSSEC keys to be kept up to date
 817                   using RFC 5011 trust anchor maintenance.
 818                 </p>
 819               </td>
 820 </tr>
 821 <tr>
 822 <td>
 823                 <p><span><strong class="command">view</strong></span></p>
 824               </td>
 825 <td>
 826                 <p>
 827                   defines a view.
 828                 </p>
 829               </td>
 830 </tr>
 831 <tr>
 832 <td>
 833                 <p><span><strong class="command">zone</strong></span></p>
 834               </td>
 835 <td>
 836                 <p>
 837                   defines a zone.
 838                 </p>
 839               </td>
 840 </tr>
 841 </tbody>
 842 </table></div>
 843 <p>
 844         The <span><strong class="command">logging</strong></span> and
 845         <span><strong class="command">options</strong></span> statements may only occur once
 846         per
 847         configuration.
 848       </p>
 849 <div class="sect2" lang="en">
 850 <div class="titlepage"><div><div><h3 class="title">
 851 <a name="id2574937"></a><span><strong class="command">acl</strong></span> Statement Grammar</h3></div></div></div>
 852 <pre class="programlisting"><span><strong class="command">acl</strong></span> acl-name {
 853     address_match_list
 854 };
 855 </pre>
 856 </div>
 857 <div class="sect2" lang="en">
 858 <div class="titlepage"><div><div><h3 class="title">
 859 <a name="acl"></a><span><strong class="command">acl</strong></span> Statement Definition and
 860           Usage</h3></div></div></div>
 861 <p>
 862           The <span><strong class="command">acl</strong></span> statement assigns a symbolic
 863           name to an address match list. It gets its name from a primary
 864           use of address match lists: Access Control Lists (ACLs).
 865         </p>
 866 <p>
 867           Note that an address match list's name must be defined
 868           with <span><strong class="command">acl</strong></span> before it can be used
 869           elsewhere; no forward references are allowed.
 870         </p>
 871 <p>
 872           The following ACLs are built-in:
 873         </p>
 874 <div class="informaltable"><table border="1">
 875 <colgroup>
 876 <col>
 877 <col>
 878 </colgroup>
 879 <tbody>
 880 <tr>
 881 <td>
 882                   <p><span><strong class="command">any</strong></span></p>
 883                 </td>
 884 <td>
 885                   <p>
 886                     Matches all hosts.
 887                   </p>
 888                 </td>
 889 </tr>
 890 <tr>
 891 <td>
 892                   <p><span><strong class="command">none</strong></span></p>
 893                 </td>
 894 <td>
 895                   <p>
 896                     Matches no hosts.
 897                   </p>
 898                 </td>
 899 </tr>
 900 <tr>
 901 <td>
 902                   <p><span><strong class="command">localhost</strong></span></p>
 903                 </td>
 904 <td>
 905                   <p>
 906                     Matches the IPv4 and IPv6 addresses of all network
 907                     interfaces on the system.
 908                   </p>
 909                 </td>
 910 </tr>
 911 <tr>
 912 <td>
 913                   <p><span><strong class="command">localnets</strong></span></p>
 914                 </td>
 915 <td>
 916                   <p>
 917                     Matches any host on an IPv4 or IPv6 network
 918                     for which the system has an interface.
 919                     Some systems do not provide a way to determine the prefix
 920                     lengths of
 921                     local IPv6 addresses.
 922                     In such a case, <span><strong class="command">localnets</strong></span>
 923                     only matches the local
 924                     IPv6 addresses, just like <span><strong class="command">localhost</strong></span>.
 925                   </p>
 926                 </td>
 927 </tr>
 928 </tbody>
 929 </table></div>
 930 </div>
 931 <div class="sect2" lang="en">
 932 <div class="titlepage"><div><div><h3 class="title">
 933 <a name="id2575127"></a><span><strong class="command">controls</strong></span> Statement Grammar</h3></div></div></div>
 934 <pre class="programlisting"><span><strong class="command">controls</strong></span> {
 935    [ inet ( ip_addr | * ) [ port ip_port ]
 936                 allow { <em class="replaceable"><code> address_match_list </code></em> }
 937                 keys { <em class="replaceable"><code>key_list</code></em> }; ]
 938    [ inet ...; ]
 939    [ 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>
 940      keys { <em class="replaceable"><code>key_list</code></em> }; ]
 941    [ unix ...; ]
 942 };
 943 </pre>
 944 </div>
 945 <div class="sect2" lang="en">
 946 <div class="titlepage"><div><div><h3 class="title">
 947 <a name="controls_statement_definition_and_usage"></a><span><strong class="command">controls</strong></span> Statement Definition and
 948           Usage</h3></div></div></div>
 949 <p>
 950           The <span><strong class="command">controls</strong></span> statement declares control
 951           channels to be used by system administrators to control the
 952           operation of the name server. These control channels are
 953           used by the <span><strong class="command">rndc</strong></span> utility to send
 954           commands to and retrieve non-DNS results from a name server.
 955         </p>
 956 <p>
 957           An <span><strong class="command">inet</strong></span> control channel is a TCP socket
 958           listening at the specified <span><strong class="command">ip_port</strong></span> on the
 959           specified <span><strong class="command">ip_addr</strong></span>, which can be an IPv4 or IPv6
 960           address.  An <span><strong class="command">ip_addr</strong></span> of <code class="literal">*</code> (asterisk) is
 961           interpreted as the IPv4 wildcard address; connections will be
 962           accepted on any of the system's IPv4 addresses.
 963           To listen on the IPv6 wildcard address,
 964           use an <span><strong class="command">ip_addr</strong></span> of <code class="literal">::</code>.
 965           If you will only use <span><strong class="command">rndc</strong></span> on the local host,
 966           using the loopback address (<code class="literal">127.0.0.1</code>
 967           or <code class="literal">::1</code>) is recommended for maximum security.
 968         </p>
 969 <p>
 970           If no port is specified, port 953 is used. The asterisk
 971           "<code class="literal">*</code>" cannot be used for <span><strong class="command">ip_port</strong></span>.
 972         </p>
 973 <p>
 974           The ability to issue commands over the control channel is
 975           restricted by the <span><strong class="command">allow</strong></span> and
 976           <span><strong class="command">keys</strong></span> clauses.
 977           Connections to the control channel are permitted based on the
 978           <span><strong class="command">address_match_list</strong></span>.  This is for simple
 979           IP address based filtering only; any <span><strong class="command">key_id</strong></span>
 980           elements of the <span><strong class="command">address_match_list</strong></span>
 981           are ignored.
 982         </p>
 983 <p>
 984           A <span><strong class="command">unix</strong></span> control channel is a UNIX domain
 985           socket listening at the specified path in the file system.
 986           Access to the socket is specified by the <span><strong class="command">perm</strong></span>,
 987           <span><strong class="command">owner</strong></span> and <span><strong class="command">group</strong></span> clauses.
 988           Note on some platforms (SunOS and Solaris) the permissions
 989           (<span><strong class="command">perm</strong></span>) are applied to the parent directory
 990           as the permissions on the socket itself are ignored.
 991         </p>
 992 <p>
 993           The primary authorization mechanism of the command
 994           channel is the <span><strong class="command">key_list</strong></span>, which
 995           contains a list of <span><strong class="command">key_id</strong></span>s.
 996           Each <span><strong class="command">key_id</strong></span> in the <span><strong class="command">key_list</strong></span>
 997           is authorized to execute commands over the control channel.
 998           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>)
 999           for information about configuring keys in <span><strong class="command">rndc</strong></span>.
1000         </p>
1001 <p>
1002           If no <span><strong class="command">controls</strong></span> statement is present,
1003           <span><strong class="command">named</strong></span> will set up a default
1004           control channel listening on the loopback address 127.0.0.1
1005           and its IPv6 counterpart ::1.
1006           In this case, and also when the <span><strong class="command">controls</strong></span> statement
1007           is present but does not have a <span><strong class="command">keys</strong></span> clause,
1008           <span><strong class="command">named</strong></span> will attempt to load the command channel key
1009           from the file <code class="filename">rndc.key</code> in
1010           <code class="filename">/etc</code> (or whatever <code class="varname">sysconfdir</code>
1011           was specified as when <acronym class="acronym">BIND</acronym> was built).
1012           To create a <code class="filename">rndc.key</code> file, run
1013           <strong class="userinput"><code>rndc-confgen -a</code></strong>.
1014         </p>
1015 <p>
1016           The <code class="filename">rndc.key</code> feature was created to
1017           ease the transition of systems from <acronym class="acronym">BIND</acronym> 8,
1018           which did not have digital signatures on its command channel
1019           messages and thus did not have a <span><strong class="command">keys</strong></span> clause.
1020
1021           It makes it possible to use an existing <acronym class="acronym">BIND</acronym> 8
1022           configuration file in <acronym class="acronym">BIND</acronym> 9 unchanged,
1023           and still have <span><strong class="command">rndc</strong></span> work the same way
1024           <span><strong class="command">ndc</strong></span> worked in BIND 8, simply by executing the
1025           command <strong class="userinput"><code>rndc-confgen -a</code></strong> after BIND 9 is
1026           installed.
1027         </p>
1028 <p>
1029           Since the <code class="filename">rndc.key</code> feature
1030           is only intended to allow the backward-compatible usage of
1031           <acronym class="acronym">BIND</acronym> 8 configuration files, this
1032           feature does not
1033           have a high degree of configurability.  You cannot easily change
1034           the key name or the size of the secret, so you should make a
1035           <code class="filename">rndc.conf</code> with your own key if you
1036           wish to change
1037           those things.  The <code class="filename">rndc.key</code> file
1038           also has its
1039           permissions set such that only the owner of the file (the user that
1040           <span><strong class="command">named</strong></span> is running as) can access it.
1041           If you
1042           desire greater flexibility in allowing other users to access
1043           <span><strong class="command">rndc</strong></span> commands, then you need to create
1044           a
1045           <code class="filename">rndc.conf</code> file and make it group
1046           readable by a group
1047           that contains the users who should have access.
1048         </p>
1049 <p>
1050           To disable the command channel, use an empty
1051           <span><strong class="command">controls</strong></span> statement:
1052           <span><strong class="command">controls { };</strong></span>.
1053         </p>
1054 </div>
1055 <div class="sect2" lang="en">
1056 <div class="titlepage"><div><div><h3 class="title">
1057 <a name="id2575418"></a><span><strong class="command">include</strong></span> Statement Grammar</h3></div></div></div>
1058 <pre class="programlisting"><span><strong class="command">include</strong></span> <em class="replaceable"><code>filename</code></em>;</pre>
1059 </div>
1060 <div class="sect2" lang="en">
1061 <div class="titlepage"><div><div><h3 class="title">
1062 <a name="id2575504"></a><span><strong class="command">include</strong></span> Statement Definition and
1063           Usage</h3></div></div></div>
1064 <p>
1065           The <span><strong class="command">include</strong></span> statement inserts the
1066           specified file at the point where the <span><strong class="command">include</strong></span>
1067           statement is encountered. The <span><strong class="command">include</strong></span>
1068                 statement facilitates the administration of configuration
1069           files
1070           by permitting the reading or writing of some things but not
1071           others. For example, the statement could include private keys
1072           that are readable only by the name server.
1073         </p>
1074 </div>
1075 <div class="sect2" lang="en">
1076 <div class="titlepage"><div><div><h3 class="title">
1077 <a name="id2575527"></a><span><strong class="command">key</strong></span> Statement Grammar</h3></div></div></div>
1078 <pre class="programlisting"><span><strong class="command">key</strong></span> <em class="replaceable"><code>key_id</code></em> {
1079     algorithm <em class="replaceable"><code>string</code></em>;
1080     secret <em class="replaceable"><code>string</code></em>;
1081 };
1082 </pre>
1083 </div>
1084 <div class="sect2" lang="en">
1085 <div class="titlepage"><div><div><h3 class="title">
1086 <a name="id2575550"></a><span><strong class="command">key</strong></span> Statement Definition and Usage</h3></div></div></div>
1087 <p>
1088           The <span><strong class="command">key</strong></span> statement defines a shared
1089           secret key for use with TSIG (see <a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
1090           or the command channel
1091           (see <a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and
1092           Usage">the section called &#8220;<span><strong class="command">controls</strong></span> Statement Definition and
1093           Usage&#8221;</a>).
1094         </p>
1095 <p>
1096           The <span><strong class="command">key</strong></span> statement can occur at the
1097           top level
1098           of the configuration file or inside a <span><strong class="command">view</strong></span>
1099           statement.  Keys defined in top-level <span><strong class="command">key</strong></span>
1100           statements can be used in all views.  Keys intended for use in
1101           a <span><strong class="command">controls</strong></span> statement
1102           (see <a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and
1103           Usage">the section called &#8220;<span><strong class="command">controls</strong></span> Statement Definition and
1104           Usage&#8221;</a>)
1105           must be defined at the top level.
1106         </p>
1107 <p>
1108           The <em class="replaceable"><code>key_id</code></em>, also known as the
1109           key name, is a domain name uniquely identifying the key. It can
1110           be used in a <span><strong class="command">server</strong></span>
1111           statement to cause requests sent to that
1112           server to be signed with this key, or in address match lists to
1113           verify that incoming requests have been signed with a key
1114           matching this name, algorithm, and secret.
1115         </p>
1116 <p>
1117           The <em class="replaceable"><code>algorithm_id</code></em> is a string
1118           that specifies a security/authentication algorithm.  Named
1119           supports <code class="literal">hmac-md5</code>,
1120           <code class="literal">hmac-sha1</code>, <code class="literal">hmac-sha224</code>,
1121           <code class="literal">hmac-sha256</code>, <code class="literal">hmac-sha384</code>
1122           and <code class="literal">hmac-sha512</code> TSIG authentication.
1123           Truncated hashes are supported by appending the minimum
1124           number of required bits preceded by a dash, e.g.
1125           <code class="literal">hmac-sha1-80</code>.  The
1126           <em class="replaceable"><code>secret_string</code></em> is the secret
1127           to be used by the algorithm, and is treated as a base-64
1128           encoded string.
1129         </p>
1130 </div>
1131 <div class="sect2" lang="en">
1132 <div class="titlepage"><div><div><h3 class="title">
1133 <a name="id2575709"></a><span><strong class="command">logging</strong></span> Statement Grammar</h3></div></div></div>
1134 <pre class="programlisting"><span><strong class="command">logging</strong></span> {
1135    [ <span><strong class="command">channel</strong></span> <em class="replaceable"><code>channel_name</code></em> {
1136      ( <span><strong class="command">file</strong></span> <em class="replaceable"><code>path_name</code></em>
1137          [ <span><strong class="command">versions</strong></span> ( <em class="replaceable"><code>number</code></em> | <span><strong class="command">unlimited</strong></span> ) ]
1138          [ <span><strong class="command">size</strong></span> <em class="replaceable"><code>size spec</code></em> ]
1139        | <span><strong class="command">syslog</strong></span> <em class="replaceable"><code>syslog_facility</code></em>
1140        | <span><strong class="command">stderr</strong></span>
1141        | <span><strong class="command">null</strong></span> );
1142      [ <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> |
1143                  <code class="option">info</code> | <code class="option">debug</code> [ <em class="replaceable"><code>level</code></em> ] | <code class="option">dynamic</code> ); ]
1144      [ <span><strong class="command">print-category</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1145      [ <span><strong class="command">print-severity</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1146      [ <span><strong class="command">print-time</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1147    }; ]
1148    [ <span><strong class="command">category</strong></span> <em class="replaceable"><code>category_name</code></em> {
1149      <em class="replaceable"><code>channel_name</code></em> ; [ <em class="replaceable"><code>channel_name</code></em> ; ... ]
1150    }; ]
1151    ...
1152 };
1153 </pre>
1154 </div>
1155 <div class="sect2" lang="en">
1156 <div class="titlepage"><div><div><h3 class="title">
1157 <a name="id2575835"></a><span><strong class="command">logging</strong></span> Statement Definition and
1158           Usage</h3></div></div></div>
1159 <p>
1160           The <span><strong class="command">logging</strong></span> statement configures a
1161           wide
1162           variety of logging options for the name server. Its <span><strong class="command">channel</strong></span> phrase
1163           associates output methods, format options and severity levels with
1164           a name that can then be used with the <span><strong class="command">category</strong></span> phrase
1165           to select how various classes of messages are logged.
1166         </p>
1167 <p>
1168           Only one <span><strong class="command">logging</strong></span> statement is used to
1169           define
1170           as many channels and categories as are wanted. If there is no <span><strong class="command">logging</strong></span> statement,
1171           the logging configuration will be:
1172         </p>
1173 <pre class="programlisting">logging {
1174      category default { default_syslog; default_debug; };
1175      category unmatched { null; };
1176 };
1177 </pre>
1178 <p>
1179           In <acronym class="acronym">BIND</acronym> 9, the logging configuration
1180           is only established when
1181           the entire configuration file has been parsed.  In <acronym class="acronym">BIND</acronym> 8, it was
1182           established as soon as the <span><strong class="command">logging</strong></span>
1183           statement
1184           was parsed. When the server is starting up, all logging messages
1185           regarding syntax errors in the configuration file go to the default
1186           channels, or to standard error if the "<code class="option">-g</code>" option
1187           was specified.
1188         </p>
1189 <div class="sect3" lang="en">
1190 <div class="titlepage"><div><div><h4 class="title">
1191 <a name="id2575888"></a>The <span><strong class="command">channel</strong></span> Phrase</h4></div></div></div>
1192 <p>
1193             All log output goes to one or more <span class="emphasis"><em>channels</em></span>;
1194             you can make as many of them as you want.
1195           </p>
1196 <p>
1197             Every channel definition must include a destination clause that
1198             says whether messages selected for the channel go to a file, to a
1199             particular syslog facility, to the standard error stream, or are
1200             discarded. It can optionally also limit the message severity level
1201             that will be accepted by the channel (the default is
1202             <span><strong class="command">info</strong></span>), and whether to include a
1203             <span><strong class="command">named</strong></span>-generated time stamp, the
1204             category name
1205             and/or severity level (the default is not to include any).
1206           </p>
1207 <p>
1208             The <span><strong class="command">null</strong></span> destination clause
1209             causes all messages sent to the channel to be discarded;
1210             in that case, other options for the channel are meaningless.
1211           </p>
1212 <p>
1213             The <span><strong class="command">file</strong></span> destination clause directs
1214             the channel
1215             to a disk file.  It can include limitations
1216             both on how large the file is allowed to become, and how many
1217             versions
1218             of the file will be saved each time the file is opened.
1219           </p>
1220 <p>
1221             If you use the <span><strong class="command">versions</strong></span> log file
1222             option, then
1223             <span><strong class="command">named</strong></span> will retain that many backup
1224             versions of the file by
1225             renaming them when opening.  For example, if you choose to keep
1226             three old versions
1227             of the file <code class="filename">lamers.log</code>, then just
1228             before it is opened
1229             <code class="filename">lamers.log.1</code> is renamed to
1230             <code class="filename">lamers.log.2</code>, <code class="filename">lamers.log.0</code> is renamed
1231             to <code class="filename">lamers.log.1</code>, and <code class="filename">lamers.log</code> is
1232             renamed to <code class="filename">lamers.log.0</code>.
1233             You can say <span><strong class="command">versions unlimited</strong></span> to
1234             not limit
1235             the number of versions.
1236             If a <span><strong class="command">size</strong></span> option is associated with
1237             the log file,
1238             then renaming is only done when the file being opened exceeds the
1239             indicated size.  No backup versions are kept by default; any
1240             existing
1241             log file is simply appended.
1242           </p>
1243 <p>
1244             The <span><strong class="command">size</strong></span> option for files is used
1245             to limit log
1246             growth. If the file ever exceeds the size, then <span><strong class="command">named</strong></span> will
1247             stop writing to the file unless it has a <span><strong class="command">versions</strong></span> option
1248             associated with it.  If backup versions are kept, the files are
1249             rolled as
1250             described above and a new one begun.  If there is no
1251             <span><strong class="command">versions</strong></span> option, no more data will
1252             be written to the log
1253             until some out-of-band mechanism removes or truncates the log to
1254             less than the
1255             maximum size.  The default behavior is not to limit the size of
1256             the
1257             file.
1258           </p>
1259 <p>
1260             Example usage of the <span><strong class="command">size</strong></span> and
1261             <span><strong class="command">versions</strong></span> options:
1262           </p>
1263 <pre class="programlisting">channel an_example_channel {
1264     file "example.log" versions 3 size 20m;
1265     print-time yes;
1266     print-category yes;
1267 };
1268 </pre>
1269 <p>
1270             The <span><strong class="command">syslog</strong></span> destination clause
1271             directs the
1272             channel to the system log.  Its argument is a
1273             syslog facility as described in the <span><strong class="command">syslog</strong></span> man
1274             page. Known facilities are <span><strong class="command">kern</strong></span>, <span><strong class="command">user</strong></span>,
1275             <span><strong class="command">mail</strong></span>, <span><strong class="command">daemon</strong></span>, <span><strong class="command">auth</strong></span>,
1276             <span><strong class="command">syslog</strong></span>, <span><strong class="command">lpr</strong></span>, <span><strong class="command">news</strong></span>,
1277             <span><strong class="command">uucp</strong></span>, <span><strong class="command">cron</strong></span>, <span><strong class="command">authpriv</strong></span>,
1278             <span><strong class="command">ftp</strong></span>, <span><strong class="command">local0</strong></span>, <span><strong class="command">local1</strong></span>,
1279             <span><strong class="command">local2</strong></span>, <span><strong class="command">local3</strong></span>, <span><strong class="command">local4</strong></span>,
1280             <span><strong class="command">local5</strong></span>, <span><strong class="command">local6</strong></span> and
1281             <span><strong class="command">local7</strong></span>, however not all facilities
1282             are supported on
1283             all operating systems.
1284             How <span><strong class="command">syslog</strong></span> will handle messages
1285             sent to
1286             this facility is described in the <span><strong class="command">syslog.conf</strong></span> man
1287             page. If you have a system which uses a very old version of <span><strong class="command">syslog</strong></span> that
1288             only uses two arguments to the <span><strong class="command">openlog()</strong></span> function,
1289             then this clause is silently ignored.
1290           </p>
1291 <p>
1292             The <span><strong class="command">severity</strong></span> clause works like <span><strong class="command">syslog</strong></span>'s
1293             "priorities", except that they can also be used if you are writing
1294             straight to a file rather than using <span><strong class="command">syslog</strong></span>.
1295             Messages which are not at least of the severity level given will
1296             not be selected for the channel; messages of higher severity
1297             levels
1298             will be accepted.
1299           </p>
1300 <p>
1301             If you are using <span><strong class="command">syslog</strong></span>, then the <span><strong class="command">syslog.conf</strong></span> priorities
1302             will also determine what eventually passes through. For example,
1303             defining a channel facility and severity as <span><strong class="command">daemon</strong></span> and <span><strong class="command">debug</strong></span> but
1304             only logging <span><strong class="command">daemon.warning</strong></span> via <span><strong class="command">syslog.conf</strong></span> will
1305             cause messages of severity <span><strong class="command">info</strong></span> and
1306             <span><strong class="command">notice</strong></span> to
1307             be dropped. If the situation were reversed, with <span><strong class="command">named</strong></span> writing
1308             messages of only <span><strong class="command">warning</strong></span> or higher,
1309             then <span><strong class="command">syslogd</strong></span> would
1310             print all messages it received from the channel.
1311           </p>
1312 <p>
1313             The <span><strong class="command">stderr</strong></span> destination clause
1314             directs the
1315             channel to the server's standard error stream.  This is intended
1316             for
1317             use when the server is running as a foreground process, for
1318             example
1319             when debugging a configuration.
1320           </p>
1321 <p>
1322             The server can supply extensive debugging information when
1323             it is in debugging mode. If the server's global debug level is
1324             greater
1325             than zero, then debugging mode will be active. The global debug
1326             level is set either by starting the <span><strong class="command">named</strong></span> server
1327             with the <code class="option">-d</code> flag followed by a positive integer,
1328             or by running <span><strong class="command">rndc trace</strong></span>.
1329             The global debug level
1330             can be set to zero, and debugging mode turned off, by running <span><strong class="command">rndc
1331 notrace</strong></span>. All debugging messages in the server have a debug
1332             level, and higher debug levels give more detailed output. Channels
1333             that specify a specific debug severity, for example:
1334           </p>
1335 <pre class="programlisting">channel specific_debug_level {
1336     file "foo";
1337     severity debug 3;
1338 };
1339 </pre>
1340 <p>
1341             will get debugging output of level 3 or less any time the
1342             server is in debugging mode, regardless of the global debugging
1343             level. Channels with <span><strong class="command">dynamic</strong></span>
1344             severity use the
1345             server's global debug level to determine what messages to print.
1346           </p>
1347 <p>
1348             If <span><strong class="command">print-time</strong></span> has been turned on,
1349             then
1350             the date and time will be logged. <span><strong class="command">print-time</strong></span> may
1351             be specified for a <span><strong class="command">syslog</strong></span> channel,
1352             but is usually
1353             pointless since <span><strong class="command">syslog</strong></span> also logs
1354             the date and
1355             time. If <span><strong class="command">print-category</strong></span> is
1356             requested, then the
1357             category of the message will be logged as well. Finally, if <span><strong class="command">print-severity</strong></span> is
1358             on, then the severity level of the message will be logged. The <span><strong class="command">print-</strong></span> options may
1359             be used in any combination, and will always be printed in the
1360             following
1361             order: time, category, severity. Here is an example where all
1362             three <span><strong class="command">print-</strong></span> options
1363             are on:
1364           </p>
1365 <p>
1366             <code class="computeroutput">28-Feb-2000 15:05:32.863 general: notice: running</code>
1367           </p>
1368 <p>
1369             There are four predefined channels that are used for
1370             <span><strong class="command">named</strong></span>'s default logging as follows.
1371             How they are
1372             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>.
1373           </p>
1374 <pre class="programlisting">channel default_syslog {
1375     // send to syslog's daemon facility
1376     syslog daemon;
1377     // only send priority info and higher
1378     severity info;
1379
1380 channel default_debug {
1381     // write to named.run in the working directory
1382     // Note: stderr is used instead of "named.run" if
1383     // the server is started with the '-f' option.
1384     file "named.run";
1385     // log at the server's current debug level
1386     severity dynamic;
1387 };
1388
1389 channel default_stderr {
1390     // writes to stderr
1391     stderr;
1392     // only send priority info and higher
1393     severity info;
1394 };
1395
1396 channel null {
1397    // toss anything sent to this channel
1398    null;
1399 };
1400 </pre>
1401 <p>
1402             The <span><strong class="command">default_debug</strong></span> channel has the
1403             special
1404             property that it only produces output when the server's debug
1405             level is
1406             nonzero.  It normally writes to a file called <code class="filename">named.run</code>
1407             in the server's working directory.
1408           </p>
1409 <p>
1410             For security reasons, when the "<code class="option">-u</code>"
1411             command line option is used, the <code class="filename">named.run</code> file
1412             is created only after <span><strong class="command">named</strong></span> has
1413             changed to the
1414             new UID, and any debug output generated while <span><strong class="command">named</strong></span> is
1415             starting up and still running as root is discarded.  If you need
1416             to capture this output, you must run the server with the "<code class="option">-g</code>"
1417             option and redirect standard error to a file.
1418           </p>
1419 <p>
1420             Once a channel is defined, it cannot be redefined. Thus you
1421             cannot alter the built-in channels directly, but you can modify
1422             the default logging by pointing categories at channels you have
1423             defined.
1424           </p>
1425 </div>
1426 <div class="sect3" lang="en">
1427 <div class="titlepage"><div><div><h4 class="title">
1428 <a name="the_category_phrase"></a>The <span><strong class="command">category</strong></span> Phrase</h4></div></div></div>
1429 <p>
1430             There are many categories, so you can send the logs you want
1431             to see wherever you want, without seeing logs you don't want. If
1432             you don't specify a list of channels for a category, then log
1433             messages
1434             in that category will be sent to the <span><strong class="command">default</strong></span> category
1435             instead. If you don't specify a default category, the following
1436             "default default" is used:
1437           </p>
1438 <pre class="programlisting">category default { default_syslog; default_debug; };
1439 </pre>
1440 <p>
1441             As an example, let's say you want to log security events to
1442             a file, but you also want keep the default logging behavior. You'd
1443             specify the following:
1444           </p>
1445 <pre class="programlisting">channel my_security_channel {
1446     file "my_security_file";
1447     severity info;
1448 };
1449 category security {
1450     my_security_channel;
1451     default_syslog;
1452     default_debug;
1453 };</pre>
1454 <p>
1455             To discard all messages in a category, specify the <span><strong class="command">null</strong></span> channel:
1456           </p>
1457 <pre class="programlisting">category xfer-out { null; };
1458 category notify { null; };
1459 </pre>
1460 <p>
1461             Following are the available categories and brief descriptions
1462             of the types of log information they contain. More
1463             categories may be added in future <acronym class="acronym">BIND</acronym> releases.
1464           </p>
1465 <div class="informaltable"><table border="1">
1466 <colgroup>
1467 <col>
1468 <col>
1469 </colgroup>
1470 <tbody>
1471 <tr>
1472 <td>
1473                     <p><span><strong class="command">default</strong></span></p>
1474                   </td>
1475 <td>
1476                     <p>
1477                       The default category defines the logging
1478                       options for those categories where no specific
1479                       configuration has been
1480                       defined.
1481                     </p>
1482                   </td>
1483 </tr>
1484 <tr>
1485 <td>
1486                     <p><span><strong class="command">general</strong></span></p>
1487                   </td>
1488 <td>
1489                     <p>
1490                       The catch-all. Many things still aren't
1491                       classified into categories, and they all end up here.
1492                     </p>
1493                   </td>
1494 </tr>
1495 <tr>
1496 <td>
1497                     <p><span><strong class="command">database</strong></span></p>
1498                   </td>
1499 <td>
1500                     <p>
1501                       Messages relating to the databases used
1502                       internally by the name server to store zone and cache
1503                       data.
1504                     </p>
1505                   </td>
1506 </tr>
1507 <tr>
1508 <td>
1509                     <p><span><strong class="command">security</strong></span></p>
1510                   </td>
1511 <td>
1512                     <p>
1513                       Approval and denial of requests.
1514                     </p>
1515                   </td>
1516 </tr>
1517 <tr>
1518 <td>
1519                     <p><span><strong class="command">config</strong></span></p>
1520                   </td>
1521 <td>
1522                     <p>
1523                       Configuration file parsing and processing.
1524                     </p>
1525                   </td>
1526 </tr>
1527 <tr>
1528 <td>
1529                     <p><span><strong class="command">resolver</strong></span></p>
1530                   </td>
1531 <td>
1532                     <p>
1533                       DNS resolution, such as the recursive
1534                       lookups performed on behalf of clients by a caching name
1535                       server.
1536                     </p>
1537                   </td>
1538 </tr>
1539 <tr>
1540 <td>
1541                     <p><span><strong class="command">xfer-in</strong></span></p>
1542                   </td>
1543 <td>
1544                     <p>
1545                       Zone transfers the server is receiving.
1546                     </p>
1547                   </td>
1548 </tr>
1549 <tr>
1550 <td>
1551                     <p><span><strong class="command">xfer-out</strong></span></p>
1552                   </td>
1553 <td>
1554                     <p>
1555                       Zone transfers the server is sending.
1556                     </p>
1557                   </td>
1558 </tr>
1559 <tr>
1560 <td>
1561                     <p><span><strong class="command">notify</strong></span></p>
1562                   </td>
1563 <td>
1564                     <p>
1565                       The NOTIFY protocol.
1566                     </p>
1567                   </td>
1568 </tr>
1569 <tr>
1570 <td>
1571                     <p><span><strong class="command">client</strong></span></p>
1572                   </td>
1573 <td>
1574                     <p>
1575                       Processing of client requests.
1576                     </p>
1577                   </td>
1578 </tr>
1579 <tr>
1580 <td>
1581                     <p><span><strong class="command">unmatched</strong></span></p>
1582                   </td>
1583 <td>
1584                     <p>
1585                       Messages that <span><strong class="command">named</strong></span> was unable to determine the
1586                       class of or for which there was no matching <span><strong class="command">view</strong></span>.
1587                       A one line summary is also logged to the <span><strong class="command">client</strong></span> category.
1588                       This category is best sent to a file or stderr, by
1589                       default it is sent to
1590                       the <span><strong class="command">null</strong></span> channel.
1591                     </p>
1592                   </td>
1593 </tr>
1594 <tr>
1595 <td>
1596                     <p><span><strong class="command">network</strong></span></p>
1597                   </td>
1598 <td>
1599                     <p>
1600                       Network operations.
1601                     </p>
1602                   </td>
1603 </tr>
1604 <tr>
1605 <td>
1606                     <p><span><strong class="command">update</strong></span></p>
1607                   </td>
1608 <td>
1609                     <p>
1610                       Dynamic updates.
1611                     </p>
1612                   </td>
1613 </tr>
1614 <tr>
1615 <td>
1616                     <p><span><strong class="command">update-security</strong></span></p>
1617                   </td>
1618 <td>
1619                     <p>
1620                       Approval and denial of update requests.
1621                     </p>
1622                   </td>
1623 </tr>
1624 <tr>
1625 <td>
1626                     <p><span><strong class="command">queries</strong></span></p>
1627                   </td>
1628 <td>
1629                     <p>
1630                       Specify where queries should be logged to.
1631                     </p>
1632                     <p>
1633                       At startup, specifying the category <span><strong class="command">queries</strong></span> will also
1634                       enable query logging unless <span><strong class="command">querylog</strong></span> option has been
1635                       specified.
1636                     </p>
1637
1638                     <p>
1639                       The query log entry reports the client's IP
1640                       address and port number, and the query name,
1641                       class and type.  Next it reports whether the
1642                       Recursion Desired flag was set (+ if set, -
1643                       if not set), if the query was signed (S),
1644                       EDNS was in use (E), if TCP was used (T), if
1645                       DO (DNSSEC Ok) was set (D), or if CD (Checking
1646                       Disabled) was set (C).  After this the
1647                       destination address the query was sent to is
1648                       reported.
1649                     </p>
1650
1651                     <p>
1652                       <code class="computeroutput">client 127.0.0.1#62536: query: www.example.com IN AAAA +SE</code>
1653                     </p>
1654                     <p>
1655                       <code class="computeroutput">client ::1#62537: query: www.example.net IN AAAA -SE</code>
1656                     </p>
1657                   </td>
1658 </tr>
1659 <tr>
1660 <td>
1661                     <p><span><strong class="command">query-errors</strong></span></p>
1662                   </td>
1663 <td>
1664                     <p>
1665                       Information about queries that resulted in some
1666                       failure.
1667                     </p>
1668                   </td>
1669 </tr>
1670 <tr>
1671 <td>
1672                     <p><span><strong class="command">dispatch</strong></span></p>
1673                   </td>
1674 <td>
1675                     <p>
1676                       Dispatching of incoming packets to the
1677                       server modules where they are to be processed.
1678                     </p>
1679                   </td>
1680 </tr>
1681 <tr>
1682 <td>
1683                     <p><span><strong class="command">dnssec</strong></span></p>
1684                   </td>
1685 <td>
1686                     <p>
1687                       DNSSEC and TSIG protocol processing.
1688                     </p>
1689                   </td>
1690 </tr>
1691 <tr>
1692 <td>
1693                     <p><span><strong class="command">lame-servers</strong></span></p>
1694                   </td>
1695 <td>
1696                     <p>
1697                       Lame servers.  These are misconfigurations
1698                       in remote servers, discovered by BIND 9 when trying to
1699                       query those servers during resolution.
1700                     </p>
1701                   </td>
1702 </tr>
1703 <tr>
1704 <td>
1705                     <p><span><strong class="command">delegation-only</strong></span></p>
1706                   </td>
1707 <td>
1708                     <p>
1709                       Delegation only.  Logs queries that have been
1710                       forced to NXDOMAIN as the result of a
1711                       delegation-only zone or a
1712                       <span><strong class="command">delegation-only</strong></span> in a hint
1713                       or stub zone declaration.
1714                     </p>
1715                   </td>
1716 </tr>
1717 <tr>
1718 <td>
1719                     <p><span><strong class="command">edns-disabled</strong></span></p>
1720                   </td>
1721 <td>
1722                     <p>
1723                       Log queries that have been forced to use plain
1724                       DNS due to timeouts.  This is often due to
1725                       the remote servers not being RFC 1034 compliant
1726                       (not always returning FORMERR or similar to
1727                       EDNS queries and other extensions to the DNS
1728                       when they are not understood).  In other words, this is
1729                       targeted at servers that fail to respond to
1730                       DNS queries that they don't understand.
1731                     </p>
1732                     <p>
1733                       Note: the log message can also be due to
1734                       packet loss.  Before reporting servers for
1735                       non-RFC 1034 compliance they should be re-tested
1736                       to determine the nature of the non-compliance.
1737                       This testing should prevent or reduce the
1738                       number of false-positive reports.
1739                     </p>
1740                     <p>
1741                       Note: eventually <span><strong class="command">named</strong></span> will have to stop
1742                       treating such timeouts as due to RFC 1034 non
1743                       compliance and start treating it as plain
1744                       packet loss.  Falsely classifying packet
1745                       loss as due to RFC 1034 non compliance impacts
1746                       on DNSSEC validation which requires EDNS for
1747                       the DNSSEC records to be returned.
1748                     </p>
1749                   </td>
1750 </tr>
1751 </tbody>
1752 </table></div>
1753 </div>
1754 <div class="sect3" lang="en">
1755 <div class="titlepage"><div><div><h4 class="title">
1756 <a name="id2577315"></a>The <span><strong class="command">query-errors</strong></span> Category</h4></div></div></div>
1757 <p>
1758             The <span><strong class="command">query-errors</strong></span> category is
1759             specifically intended for debugging purposes: To identify
1760             why and how specific queries result in responses which
1761             indicate an error.
1762             Messages of this category are therefore only logged
1763             with <span><strong class="command">debug</strong></span> levels.
1764           </p>
1765 <p>
1766             At the debug levels of 1 or higher, each response with the
1767             rcode of SERVFAIL is logged as follows:
1768           </p>
1769 <p>
1770             <code class="computeroutput">client 127.0.0.1#61502: query failed (SERVFAIL) for www.example.com/IN/AAAA at query.c:3880</code>
1771           </p>
1772 <p>
1773             This means an error resulting in SERVFAIL was
1774             detected at line 3880 of source file
1775             <code class="filename">query.c</code>.
1776             Log messages of this level will particularly
1777             help identify the cause of SERVFAIL for an
1778             authoritative server.
1779           </p>
1780 <p>
1781             At the debug levels of 2 or higher, detailed context
1782             information of recursive resolutions that resulted in
1783             SERVFAIL is logged.
1784             The log message will look like as follows:
1785           </p>
1786 <p>
1787
1788             </p>
1789 <pre class="programlisting">
1790 fetch completed at resolver.c:2970 for www.example.com/A
1791 in 30.000183: timed out/success [domain:example.com,
1792 referral:2,restart:7,qrysent:8,timeout:5,lame:0,neterr:0,
1793 badresp:1,adberr:0,findfail:0,valfail:0]
1794             </pre>
1795 <p>
1796           </p>
1797 <p>
1798             The first part before the colon shows that a recursive
1799             resolution for AAAA records of www.example.com completed
1800             in 30.000183 seconds and the final result that led to the
1801             SERVFAIL was determined at line 2970 of source file
1802             <code class="filename">resolver.c</code>.
1803           </p>
1804 <p>
1805             The following part shows the detected final result and the
1806             latest result of DNSSEC validation.
1807             The latter is always success when no validation attempt
1808             is made.
1809             In this example, this query resulted in SERVFAIL probably
1810             because all name servers are down or unreachable, leading
1811             to a timeout in 30 seconds.
1812             DNSSEC validation was probably not attempted.
1813           </p>
1814 <p>
1815             The last part enclosed in square brackets shows statistics
1816             information collected for this particular resolution
1817             attempt.
1818             The <code class="varname">domain</code> field shows the deepest zone
1819             that the resolver reached;
1820             it is the zone where the error was finally detected.
1821             The meaning of the other fields is summarized in the
1822             following table.
1823           </p>
1824 <div class="informaltable"><table border="1">
1825 <colgroup>
1826 <col>
1827 <col>
1828 </colgroup>
1829 <tbody>
1830 <tr>
1831 <td>
1832                     <p><code class="varname">referral</code></p>
1833                   </td>
1834 <td>
1835                     <p>
1836                       The number of referrals the resolver received
1837                       throughout the resolution process.
1838                       In the above example this is 2, which are most
1839                       likely com and example.com.
1840                     </p>
1841                   </td>
1842 </tr>
1843 <tr>
1844 <td>
1845                     <p><code class="varname">restart</code></p>
1846                   </td>
1847 <td>
1848                     <p>
1849                       The number of cycles that the resolver tried
1850                       remote servers at the <code class="varname">domain</code>
1851                       zone.
1852                       In each cycle the resolver sends one query
1853                       (possibly resending it, depending on the response)
1854                       to each known name server of
1855                       the <code class="varname">domain</code> zone.
1856                     </p>
1857                   </td>
1858 </tr>
1859 <tr>
1860 <td>
1861                     <p><code class="varname">qrysent</code></p>
1862                   </td>
1863 <td>
1864                     <p>
1865                       The number of queries the resolver sent at the
1866                       <code class="varname">domain</code> zone.
1867                     </p>
1868                   </td>
1869 </tr>
1870 <tr>
1871 <td>
1872                     <p><code class="varname">timeout</code></p>
1873                   </td>
1874 <td>
1875                     <p>
1876                       The number of timeouts since the resolver
1877                       received the last response.
1878                     </p>
1879                   </td>
1880 </tr>
1881 <tr>
1882 <td>
1883                     <p><code class="varname">lame</code></p>
1884                   </td>
1885 <td>
1886                     <p>
1887                       The number of lame servers the resolver detected
1888                       at the <code class="varname">domain</code> zone.
1889                       A server is detected to be lame either by an
1890                       invalid response or as a result of lookup in
1891                       BIND9's address database (ADB), where lame
1892                       servers are cached.
1893                     </p>
1894                   </td>
1895 </tr>
1896 <tr>
1897 <td>
1898                     <p><code class="varname">neterr</code></p>
1899                   </td>
1900 <td>
1901                     <p>
1902                       The number of erroneous results that the
1903                       resolver encountered in sending queries
1904                       at the <code class="varname">domain</code> zone.
1905                       One common case is the remote server is
1906                       unreachable and the resolver receives an ICMP
1907                       unreachable error message.
1908                     </p>
1909                   </td>
1910 </tr>
1911 <tr>
1912 <td>
1913                     <p><code class="varname">badresp</code></p>
1914                   </td>
1915 <td>
1916                     <p>
1917                       The number of unexpected responses (other than
1918                       <code class="varname">lame</code>) to queries sent by the
1919                       resolver at the <code class="varname">domain</code> zone.
1920                     </p>
1921                   </td>
1922 </tr>
1923 <tr>
1924 <td>
1925                     <p><code class="varname">adberr</code></p>
1926                   </td>
1927 <td>
1928                     <p>
1929                       Failures in finding remote server addresses
1930                       of the <code class="varname">domain</code> zone in the ADB.
1931                       One common case of this is that the remote
1932                       server's name does not have any address records.
1933                     </p>
1934                   </td>
1935 </tr>
1936 <tr>
1937 <td>
1938                     <p><code class="varname">findfail</code></p>
1939                   </td>
1940 <td>
1941                     <p>
1942                       Failures of resolving remote server addresses.
1943                       This is a total number of failures throughout
1944                       the resolution process.
1945                     </p>
1946                   </td>
1947 </tr>
1948 <tr>
1949 <td>
1950                     <p><code class="varname">valfail</code></p>
1951                   </td>
1952 <td>
1953                     <p>
1954                       Failures of DNSSEC validation.
1955                       Validation failures are counted throughout
1956                       the resolution process (not limited to
1957                       the <code class="varname">domain</code> zone), but should
1958                       only happen in <code class="varname">domain</code>.
1959                     </p>
1960                   </td>
1961 </tr>
1962 </tbody>
1963 </table></div>
1964 <p>
1965             At the debug levels of 3 or higher, the same messages
1966             as those at the debug 1 level are logged for other errors
1967             than SERVFAIL.
1968             Note that negative responses such as NXDOMAIN are not
1969             regarded as errors here.
1970           </p>
1971 <p>
1972             At the debug levels of 4 or higher, the same messages
1973             as those at the debug 2 level are logged for other errors
1974             than SERVFAIL.
1975             Unlike the above case of level 3, messages are logged for
1976             negative responses.
1977             This is because any unexpected results can be difficult to
1978             debug in the recursion case.
1979           </p>
1980 </div>
1981 </div>
1982 <div class="sect2" lang="en">
1983 <div class="titlepage"><div><div><h3 class="title">
1984 <a name="id2577834"></a><span><strong class="command">lwres</strong></span> Statement Grammar</h3></div></div></div>
1985 <p>
1986            This is the grammar of the <span><strong class="command">lwres</strong></span>
1987           statement in the <code class="filename">named.conf</code> file:
1988         </p>
1989 <pre class="programlisting"><span><strong class="command">lwres</strong></span> {
1990     [<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>] ;
1991                 [<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>]
1992     [<span class="optional"> view <em class="replaceable"><code>view_name</code></em>; </span>]
1993     [<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>]
1994     [<span class="optional"> ndots <em class="replaceable"><code>number</code></em>; </span>]
1995 };
1996 </pre>
1997 </div>
1998 <div class="sect2" lang="en">
1999 <div class="titlepage"><div><div><h3 class="title">
2000 <a name="id2577908"></a><span><strong class="command">lwres</strong></span> Statement Definition and Usage</h3></div></div></div>
2001 <p>
2002           The <span><strong class="command">lwres</strong></span> statement configures the
2003           name
2004           server to also act as a lightweight resolver server. (See
2005           <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
2006           <span><strong class="command">lwres</strong></span> statements configuring
2007           lightweight resolver servers with different properties.
2008         </p>
2009 <p>
2010           The <span><strong class="command">listen-on</strong></span> statement specifies a
2011           list of
2012           addresses (and ports) that this instance of a lightweight resolver
2013           daemon
2014           should accept requests on.  If no port is specified, port 921 is
2015           used.
2016           If this statement is omitted, requests will be accepted on
2017           127.0.0.1,
2018           port 921.
2019         </p>
2020 <p>
2021           The <span><strong class="command">view</strong></span> statement binds this
2022           instance of a
2023           lightweight resolver daemon to a view in the DNS namespace, so that
2024           the
2025           response will be constructed in the same manner as a normal DNS
2026           query
2027           matching this view.  If this statement is omitted, the default view
2028           is
2029           used, and if there is no default view, an error is triggered.
2030         </p>
2031 <p>
2032           The <span><strong class="command">search</strong></span> statement is equivalent to
2033           the
2034           <span><strong class="command">search</strong></span> statement in
2035           <code class="filename">/etc/resolv.conf</code>.  It provides a
2036           list of domains
2037           which are appended to relative names in queries.
2038         </p>
2039 <p>
2040           The <span><strong class="command">ndots</strong></span> statement is equivalent to
2041           the
2042           <span><strong class="command">ndots</strong></span> statement in
2043           <code class="filename">/etc/resolv.conf</code>.  It indicates the
2044           minimum
2045           number of dots in a relative domain name that should result in an
2046           exact match lookup before search path elements are appended.
2047         </p>
2048 </div>
2049 <div class="sect2" lang="en">
2050 <div class="titlepage"><div><div><h3 class="title">
2051 <a name="id2578040"></a><span><strong class="command">masters</strong></span> Statement Grammar</h3></div></div></div>
2052 <pre class="programlisting">
2053 <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> |
2054       <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>] };
2055 </pre>
2056 </div>
2057 <div class="sect2" lang="en">
2058 <div class="titlepage"><div><div><h3 class="title">
2059 <a name="id2578084"></a><span><strong class="command">masters</strong></span> Statement Definition and
2060           Usage</h3></div></div></div>
2061 <p><span><strong class="command">masters</strong></span>
2062           lists allow for a common set of masters to be easily used by
2063           multiple stub and slave zones.
2064         </p>
2065 </div>
2066 <div class="sect2" lang="en">
2067 <div class="titlepage"><div><div><h3 class="title">
2068 <a name="id2578099"></a><span><strong class="command">options</strong></span> Statement Grammar</h3></div></div></div>
2069 <p>
2070           This is the grammar of the <span><strong class="command">options</strong></span>
2071           statement in the <code class="filename">named.conf</code> file:
2072         </p>
2073 <pre class="programlisting"><span><strong class="command">options</strong></span> {
2074     [<span class="optional"> attach-cache <em class="replaceable"><code>cache_name</code></em>; </span>]
2075     [<span class="optional"> version <em class="replaceable"><code>version_string</code></em>; </span>]
2076     [<span class="optional"> hostname <em class="replaceable"><code>hostname_string</code></em>; </span>]
2077     [<span class="optional"> server-id <em class="replaceable"><code>server_id_string</code></em>; </span>]
2078     [<span class="optional"> directory <em class="replaceable"><code>path_name</code></em>; </span>]
2079     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2080     [<span class="optional"> managed-keys-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2081     [<span class="optional"> named-xfer <em class="replaceable"><code>path_name</code></em>; </span>]
2082     [<span class="optional"> tkey-gssapi-keytab <em class="replaceable"><code>path_name</code></em>; </span>]
2083     [<span class="optional"> tkey-gssapi-credential <em class="replaceable"><code>principal</code></em>; </span>]
2084     [<span class="optional"> tkey-domain <em class="replaceable"><code>domainname</code></em>; </span>]
2085     [<span class="optional"> tkey-dhkey <em class="replaceable"><code>key_name</code></em> <em class="replaceable"><code>key_tag</code></em>; </span>]
2086     [<span class="optional"> cache-file <em class="replaceable"><code>path_name</code></em>; </span>]
2087     [<span class="optional"> dump-file <em class="replaceable"><code>path_name</code></em>; </span>]
2088     [<span class="optional"> bindkeys-file <em class="replaceable"><code>path_name</code></em>; </span>]
2089     [<span class="optional"> memstatistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2090     [<span class="optional"> memstatistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2091     [<span class="optional"> pid-file <em class="replaceable"><code>path_name</code></em>; </span>]
2092     [<span class="optional"> recursing-file <em class="replaceable"><code>path_name</code></em>; </span>]
2093     [<span class="optional"> statistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2094     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2095     [<span class="optional"> auth-nxdomain <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2096     [<span class="optional"> deallocate-on-exit <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2097     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em>; </span>]
2098     [<span class="optional"> fake-iquery <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2099     [<span class="optional"> fetch-glue <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2100     [<span class="optional"> flush-zones-on-shutdown <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2101     [<span class="optional"> has-old-clients <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2102     [<span class="optional"> host-statistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2103     [<span class="optional"> host-statistics-max <em class="replaceable"><code>number</code></em>; </span>]
2104     [<span class="optional"> minimal-responses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2105     [<span class="optional"> multiple-cnames <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2106     [<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>]
2107     [<span class="optional"> recursion <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2108     [<span class="optional"> rfc2308-type1 <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2109     [<span class="optional"> use-id-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2110     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2111     [<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>]
2112     [<span class="optional"> dnssec-enable <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2113     [<span class="optional"> dnssec-validation (<em class="replaceable"><code>yes_or_no</code></em> | <code class="constant">auto</code>); </span>]
2114     [<span class="optional"> dnssec-lookaside ( <em class="replaceable"><code>auto</code></em> |
2115                         <em class="replaceable"><code>domain</code></em> trust-anchor <em class="replaceable"><code>domain</code></em> ); </span>]
2116     [<span class="optional"> dnssec-must-be-secure <em class="replaceable"><code>domain yes_or_no</code></em>; </span>]
2117     [<span class="optional"> dnssec-accept-expired <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2118     [<span class="optional"> forward ( <em class="replaceable"><code>only</code></em> | <em class="replaceable"><code>first</code></em> ); </span>]
2119     [<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>]
2120     [<span class="optional"> dual-stack-servers [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] {
2121         ( <em class="replaceable"><code>domain_name</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] |
2122           <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ) ;
2123         ... }; </span>]
2124     [<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> )
2125         ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2126     [<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>]
2127     [<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>]
2128     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2129     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2130     [<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>]
2131     [<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>]
2132     [<span class="optional"> check-sibling <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2133     [<span class="optional"> allow-new-zones { <em class="replaceable"><code>yes_or_no</code></em> }; </span>]
2134     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2135     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2136     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2137     [<span class="optional"> allow-query-cache { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2138     [<span class="optional"> allow-query-cache-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2139     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2140     [<span class="optional"> allow-recursion { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2141     [<span class="optional"> allow-recursion-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2142     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2143     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2144     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2145     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2146     [<span class="optional"> dnssec-secure-to-insecure <em class="replaceable"><code>yes_or_no</code></em> ;</span>]
2147     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2148     [<span class="optional"> allow-v6-synthesis { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2149     [<span class="optional"> blackhole { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2150     [<span class="optional"> use-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2151     [<span class="optional"> avoid-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2152     [<span class="optional"> use-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2153     [<span class="optional"> avoid-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2154     [<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>]
2155     [<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>]
2156     [<span class="optional"> query-source ( ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2157         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
2158         [<span class="optional"> address ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2159         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
2160     [<span class="optional"> query-source-v6 ( ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2161         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
2162         [<span class="optional"> address ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2163         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
2164     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2165     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
2166     [<span class="optional"> queryport-pool-updateinterval <em class="replaceable"><code>number</code></em>; </span>]
2167     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em>; </span>]
2168     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em>; </span>]
2169     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em>; </span>]
2170     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em>; </span>]
2171     [<span class="optional"> tcp-clients <em class="replaceable"><code>number</code></em>; </span>]
2172     [<span class="optional"> reserved-sockets <em class="replaceable"><code>number</code></em>; </span>]
2173     [<span class="optional"> recursive-clients <em class="replaceable"><code>number</code></em>; </span>]
2174     [<span class="optional"> serial-query-rate <em class="replaceable"><code>number</code></em>; </span>]
2175     [<span class="optional"> serial-queries <em class="replaceable"><code>number</code></em>; </span>]
2176     [<span class="optional"> tcp-listen-queue <em class="replaceable"><code>number</code></em>; </span>]
2177     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em>; </span>]
2178     [<span class="optional"> transfers-in  <em class="replaceable"><code>number</code></em>; </span>]
2179     [<span class="optional"> transfers-out <em class="replaceable"><code>number</code></em>; </span>]
2180     [<span class="optional"> transfers-per-ns <em class="replaceable"><code>number</code></em>; </span>]
2181     [<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>]
2182     [<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>]
2183     [<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>]
2184     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
2185                              [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
2186     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2187     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
2188     [<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>]
2189     [<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>]
2190     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2191     [<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>] ;
2192                   [<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>]
2193     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em>; </span>]
2194     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
2195     [<span class="optional"> coresize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2196     [<span class="optional"> datasize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2197     [<span class="optional"> files <em class="replaceable"><code>size_spec</code></em> ; </span>]
2198     [<span class="optional"> stacksize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2199     [<span class="optional"> cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2200     [<span class="optional"> heartbeat-interval <em class="replaceable"><code>number</code></em>; </span>]
2201     [<span class="optional"> interface-interval <em class="replaceable"><code>number</code></em>; </span>]
2202     [<span class="optional"> statistics-interval <em class="replaceable"><code>number</code></em>; </span>]
2203     [<span class="optional"> topology { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2204     [<span class="optional"> sortlist { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2205     [<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>] };
2206     [<span class="optional"> lame-ttl <em class="replaceable"><code>number</code></em>; </span>]
2207     [<span class="optional"> max-ncache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2208     [<span class="optional"> max-cache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2209     [<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>]
2210     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
2211     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
2212     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
2213     [<span class="optional"> min-roots <em class="replaceable"><code>number</code></em>; </span>]
2214     [<span class="optional"> use-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2215     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2216     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2217     [<span class="optional"> treat-cr-as-space <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2218     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2219     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2220     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2221     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2222     [<span class="optional"> port <em class="replaceable"><code>ip_port</code></em>; </span>]
2223     [<span class="optional"> additional-from-auth <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2224     [<span class="optional"> additional-from-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2225     [<span class="optional"> random-device <em class="replaceable"><code>path_name</code></em> ; </span>]
2226     [<span class="optional"> max-cache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2227     [<span class="optional"> match-mapped-addresses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2228     [<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>]
2229     [<span class="optional"> filter-aaaa { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2230     [<span class="optional"> dns64 <em class="replaceable"><code>IPv6-prefix</code></em> {
2231         [<span class="optional"> clients { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2232         [<span class="optional"> mapped { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2233         [<span class="optional"> exclude { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2234         [<span class="optional"> suffix IPv6-address; </span>]
2235         [<span class="optional"> recursive-only <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2236         [<span class="optional"> break-dnssec <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2237     }; </span>];
2238     [<span class="optional"> dns64-server <em class="replaceable"><code>name</code></em> </span>]
2239     [<span class="optional"> dns64-contact <em class="replaceable"><code>name</code></em> </span>]
2240     [<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>]
2241     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2242     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2243     [<span class="optional"> root-delegation-only [<span class="optional"> exclude { <em class="replaceable"><code>namelist</code></em> } </span>] ; </span>]
2244     [<span class="optional"> querylog <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2245     [<span class="optional"> disable-algorithms <em class="replaceable"><code>domain</code></em> { <em class="replaceable"><code>algorithm</code></em>;
2246                                 [<span class="optional"> <em class="replaceable"><code>algorithm</code></em>; </span>] }; </span>]
2247     [<span class="optional"> acache-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2248     [<span class="optional"> acache-cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2249     [<span class="optional"> max-acache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2250     [<span class="optional"> clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2251     [<span class="optional"> max-clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2252     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
2253     [<span class="optional"> empty-server <em class="replaceable"><code>name</code></em> ; </span>]
2254     [<span class="optional"> empty-contact <em class="replaceable"><code>name</code></em> ; </span>]
2255     [<span class="optional"> empty-zones-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2256     [<span class="optional"> disable-empty-zone <em class="replaceable"><code>zone_name</code></em> ; </span>]
2257     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2258     [<span class="optional"> zero-no-soa-ttl-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2259     [<span class="optional"> resolver-query-timeout <em class="replaceable"><code>number</code></em> ; </span>]
2260     [<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>]
2261     [<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>]
2262     [<span class="optional"> response-policy { <em class="replaceable"><code>zone_name</code></em> [<span class="optional"> policy <em class="replaceable"><code>given</code></em> | <em class="replaceable"><code>no-op</code></em> | <em class="replaceable"><code>nxdomain</code></em> | <em class="replaceable"><code>nodata</code></em> | <em class="replaceable"><code>cname domain</code></em> </span>] ; } ; </span>]
2263 };
2264 </pre>
2265 </div>
2266 <div class="sect2" lang="en">
2267 <div class="titlepage"><div><div><h3 class="title">
2268 <a name="options"></a><span><strong class="command">options</strong></span> Statement Definition and
2269           Usage</h3></div></div></div>
2270 <p>
2271           The <span><strong class="command">options</strong></span> statement sets up global
2272           options
2273           to be used by <acronym class="acronym">BIND</acronym>. This statement
2274           may appear only
2275           once in a configuration file. If there is no <span><strong class="command">options</strong></span>
2276           statement, an options block with each option set to its default will
2277           be used.
2278         </p>
2279 <div class="variablelist"><dl>
2280 <dt><span class="term"><span><strong class="command">attach-cache</strong></span></span></dt>
2281 <dd>
2282 <p>
2283                   Allows multiple views to share a single cache
2284                   database.
2285                   Each view has its own cache database by default, but
2286                   if multiple views have the same operational policy
2287                   for name resolution and caching, those views can
2288                   share a single cache to save memory and possibly
2289                   improve resolution efficiency by using this option.
2290                 </p>
2291 <p>
2292                   The <span><strong class="command">attach-cache</strong></span> option
2293                   may also be specified in <span><strong class="command">view</strong></span>
2294                   statements, in which case it overrides the
2295                   global <span><strong class="command">attach-cache</strong></span> option.
2296                 </p>
2297 <p>
2298                   The <em class="replaceable"><code>cache_name</code></em> specifies
2299                   the cache to be shared.
2300                   When the <span><strong class="command">named</strong></span> server configures
2301                   views which are supposed to share a cache, it
2302                   creates a cache with the specified name for the
2303                   first view of these sharing views.
2304                   The rest of the views will simply refer to the
2305                   already created cache.
2306                 </p>
2307 <p>
2308                   One common configuration to share a cache would be to
2309                   allow all views to share a single cache.
2310                   This can be done by specifying
2311                   the <span><strong class="command">attach-cache</strong></span> as a global
2312                   option with an arbitrary name.
2313                 </p>
2314 <p>
2315                   Another possible operation is to allow a subset of
2316                   all views to share a cache while the others to
2317                   retain their own caches.
2318                   For example, if there are three views A, B, and C,
2319                   and only A and B should share a cache, specify the
2320                   <span><strong class="command">attach-cache</strong></span> option as a view A (or
2321                   B)'s option, referring to the other view name:
2322                 </p>
2323 <pre class="programlisting">
2324   view "A" {
2325     // this view has its own cache
2326     ...
2327   };
2328   view "B" {
2329     // this view refers to A's cache
2330     attach-cache "A";
2331   };
2332   view "C" {
2333     // this view has its own cache
2334     ...
2335   };
2336 </pre>
2337 <p>
2338                   Views that share a cache must have the same policy
2339                   on configurable parameters that may affect caching.
2340                   The current implementation requires the following
2341                   configurable options be consistent among these
2342                   views:
2343                   <span><strong class="command">check-names</strong></span>,
2344                   <span><strong class="command">cleaning-interval</strong></span>,
2345                   <span><strong class="command">dnssec-accept-expired</strong></span>,
2346                   <span><strong class="command">dnssec-validation</strong></span>,
2347                   <span><strong class="command">max-cache-ttl</strong></span>,
2348                   <span><strong class="command">max-ncache-ttl</strong></span>,
2349                   <span><strong class="command">max-cache-size</strong></span>, and
2350                   <span><strong class="command">zero-no-soa-ttl</strong></span>.
2351                 </p>
2352 <p>
2353                   Note that there may be other parameters that may
2354                   cause confusion if they are inconsistent for
2355                   different views that share a single cache.
2356                   For example, if these views define different sets of
2357                   forwarders that can return different answers for the
2358                   same question, sharing the answer does not make
2359                   sense or could even be harmful.
2360                   It is administrator's responsibility to ensure
2361                   configuration differences in different views do
2362                   not cause disruption with a shared cache.
2363                 </p>
2364 </dd>
2365 <dt><span class="term"><span><strong class="command">directory</strong></span></span></dt>
2366 <dd><p>
2367                 The working directory of the server.
2368                 Any non-absolute pathnames in the configuration file will be
2369                 taken
2370                 as relative to this directory. The default location for most
2371                 server
2372                 output files (e.g. <code class="filename">named.run</code>)
2373                 is this directory.
2374                 If a directory is not specified, the working directory
2375                 defaults to `<code class="filename">.</code>', the directory from
2376                 which the server
2377                 was started. The directory specified should be an absolute
2378                 path.
2379               </p></dd>
2380 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
2381 <dd><p>
2382                 When performing dynamic update of secure zones, the
2383                 directory where the public and private DNSSEC key files
2384                 should be found, if different than the current working
2385                 directory.  (Note that this option has no effect on the
2386                 paths for files containing non-DNSSEC keys such as
2387                 <code class="filename">bind.keys</code>,
2388                 <code class="filename">rndc.key</code> or
2389                 <code class="filename">session.key</code>.)
2390               </p></dd>
2391 <dt><span class="term"><span><strong class="command">managed-keys-directory</strong></span></span></dt>
2392 <dd><p>
2393                 The directory used to hold the files used to track managed keys.
2394                 By default it is the working directory.  It there are no
2395                 views then the file <code class="filename">managed-keys.bind</code>
2396                 otherwise a SHA256 hash of the view name is used with
2397                 <code class="filename">.mkeys</code> extension added.
2398               </p></dd>
2399 <dt><span class="term"><span><strong class="command">named-xfer</strong></span></span></dt>
2400 <dd><p>
2401                 <span class="emphasis"><em>This option is obsolete.</em></span> It
2402                 was used in <acronym class="acronym">BIND</acronym> 8 to specify
2403                 the pathname to the <span><strong class="command">named-xfer</strong></span>
2404                 program.  In <acronym class="acronym">BIND</acronym> 9, no separate
2405                 <span><strong class="command">named-xfer</strong></span> program is needed;
2406                 its functionality is built into the name server.
2407               </p></dd>
2408 <dt><span class="term"><span><strong class="command">tkey-gssapi-keytab</strong></span></span></dt>
2409 <dd><p>
2410                 The KRB5 keytab file to use for GSS-TSIG updates. If
2411                 this option is set and tkey-gssapi-credential is not
2412                 set, then updates will be allowed with any key
2413                 matching a principal in the specified keytab.
2414               </p></dd>
2415 <dt><span class="term"><span><strong class="command">tkey-gssapi-credential</strong></span></span></dt>
2416 <dd><p>
2417                 The security credential with which the server should
2418                 authenticate keys requested by the GSS-TSIG protocol.
2419                 Currently only Kerberos 5 authentication is available
2420                 and the credential is a Kerberos principal which the
2421                 server can acquire through the default system key
2422                 file, normally <code class="filename">/etc/krb5.keytab</code>.
2423                 The location keytab file can be overridden using the
2424                 tkey-gssapi-keytab option. Normally this principal is
2425                 of the form "<strong class="userinput"><code>DNS/</code></strong><code class="varname">server.domain</code>".
2426                 To use GSS-TSIG, <span><strong class="command">tkey-domain</strong></span> must
2427                 also be set if a specific keytab is not set with
2428                 tkey-gssapi-keytab.
2429               </p></dd>
2430 <dt><span class="term"><span><strong class="command">tkey-domain</strong></span></span></dt>
2431 <dd><p>
2432                 The domain appended to the names of all shared keys
2433                 generated with <span><strong class="command">TKEY</strong></span>.  When a
2434                 client requests a <span><strong class="command">TKEY</strong></span> exchange,
2435                 it may or may not specify the desired name for the
2436                 key. If present, the name of the shared key will
2437                 be <code class="varname">client specified part</code> +
2438                 <code class="varname">tkey-domain</code>.  Otherwise, the
2439                 name of the shared key will be <code class="varname">random hex
2440                 digits</code> + <code class="varname">tkey-domain</code>.
2441                 In most cases, the <span><strong class="command">domainname</strong></span>
2442                 should be the server's domain name, or an otherwise
2443                 non-existent subdomain like
2444                 "_tkey.<code class="varname">domainname</code>".  If you are
2445                 using GSS-TSIG, this variable must be defined, unless
2446                 you specify a specific keytab using tkey-gssapi-keytab.
2447               </p></dd>
2448 <dt><span class="term"><span><strong class="command">tkey-dhkey</strong></span></span></dt>
2449 <dd><p>
2450                 The Diffie-Hellman key used by the server
2451                 to generate shared keys with clients using the Diffie-Hellman
2452                 mode
2453                 of <span><strong class="command">TKEY</strong></span>. The server must be
2454                 able to load the
2455                 public and private keys from files in the working directory.
2456                 In
2457                 most cases, the keyname should be the server's host name.
2458               </p></dd>
2459 <dt><span class="term"><span><strong class="command">cache-file</strong></span></span></dt>
2460 <dd><p>
2461                 This is for testing only.  Do not use.
2462               </p></dd>
2463 <dt><span class="term"><span><strong class="command">dump-file</strong></span></span></dt>
2464 <dd><p>
2465                 The pathname of the file the server dumps
2466                 the database to when instructed to do so with
2467                 <span><strong class="command">rndc dumpdb</strong></span>.
2468                 If not specified, the default is <code class="filename">named_dump.db</code>.
2469               </p></dd>
2470 <dt><span class="term"><span><strong class="command">memstatistics-file</strong></span></span></dt>
2471 <dd><p>
2472                 The pathname of the file the server writes memory
2473                 usage statistics to on exit. If not specified,
2474                 the default is <code class="filename">named.memstats</code>.
2475               </p></dd>
2476 <dt><span class="term"><span><strong class="command">pid-file</strong></span></span></dt>
2477 <dd><p>
2478                 The pathname of the file the server writes its process ID
2479                 in. If not specified, the default is
2480                 <code class="filename">/var/run/named/named.pid</code>.
2481                 The PID file is used by programs that want to send signals to
2482                 the running
2483                 name server. Specifying <span><strong class="command">pid-file none</strong></span> disables the
2484                 use of a PID file &#8212; no file will be written and any
2485                 existing one will be removed.  Note that <span><strong class="command">none</strong></span>
2486                 is a keyword, not a filename, and therefore is not enclosed
2487                 in
2488                 double quotes.
2489               </p></dd>
2490 <dt><span class="term"><span><strong class="command">recursing-file</strong></span></span></dt>
2491 <dd><p>
2492                 The pathname of the file the server dumps
2493                 the queries that are currently recursing when instructed
2494                 to do so with <span><strong class="command">rndc recursing</strong></span>.
2495                 If not specified, the default is <code class="filename">named.recursing</code>.
2496               </p></dd>
2497 <dt><span class="term"><span><strong class="command">statistics-file</strong></span></span></dt>
2498 <dd><p>
2499                 The pathname of the file the server appends statistics
2500                 to when instructed to do so using <span><strong class="command">rndc stats</strong></span>.
2501                 If not specified, the default is <code class="filename">named.stats</code> in the
2502                 server's current directory.  The format of the file is
2503                 described
2504                 in <a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
2505               </p></dd>
2506 <dt><span class="term"><span><strong class="command">bindkeys-file</strong></span></span></dt>
2507 <dd><p>
2508                 The pathname of a file to override the built-in trusted
2509                 keys provided by <span><strong class="command">named</strong></span>.
2510                 See the discussion of <span><strong class="command">dnssec-lookaside</strong></span>
2511                 and <span><strong class="command">dnssec-validation</strong></span> for details.
2512                 If not specified, the default is
2513                 <code class="filename">/etc/bind.keys</code>.
2514               </p></dd>
2515 <dt><span class="term"><span><strong class="command">secroots-file</strong></span></span></dt>
2516 <dd><p>
2517                 The pathname of the file the server dumps
2518                 security roots to when instructed to do so with
2519                 <span><strong class="command">rndc secroots</strong></span>.
2520                 If not specified, the default is <code class="filename">named.secroots</code>.
2521               </p></dd>
2522 <dt><span class="term"><span><strong class="command">session-keyfile</strong></span></span></dt>
2523 <dd><p>
2524                 The pathname of the file into which to write a TSIG
2525                 session key generated by <span><strong class="command">named</strong></span> for use by
2526                 <span><strong class="command">nsupdate -l</strong></span>.  If not specified, the
2527                 default is <code class="filename">/var/run/named/session.key</code>.
2528                 (See <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>, and in
2529                 particular the discussion of the
2530                 <span><strong class="command">update-policy</strong></span> statement's
2531                 <strong class="userinput"><code>local</code></strong> option for more
2532                 information about this feature.)
2533               </p></dd>
2534 <dt><span class="term"><span><strong class="command">session-keyname</strong></span></span></dt>
2535 <dd><p>
2536                 The key name to use for the TSIG session key.
2537                 If not specified, the default is "local-ddns".
2538               </p></dd>
2539 <dt><span class="term"><span><strong class="command">session-keyalg</strong></span></span></dt>
2540 <dd><p>
2541                 The algorithm to use for the TSIG session key.
2542                 Valid values are hmac-sha1, hmac-sha224, hmac-sha256,
2543                 hmac-sha384, hmac-sha512 and hmac-md5.  If not
2544                 specified, the default is hmac-sha256.
2545               </p></dd>
2546 <dt><span class="term"><span><strong class="command">session-keyfile</strong></span></span></dt>
2547 <dd><p>
2548                 The pathname of the file into which to write a session TSIG
2549                 key for use by <span><strong class="command">nsupdate -l</strong></span>.  (See the
2550                 discussion of the <span><strong class="command">update-policy</strong></span>
2551                 statement's <strong class="userinput"><code>local</code></strong> option for more
2552                 details on this feature.)
2553               </p></dd>
2554 <dt><span class="term"><span><strong class="command">port</strong></span></span></dt>
2555 <dd><p>
2556                 The UDP/TCP port number the server uses for
2557                 receiving and sending DNS protocol traffic.
2558                 The default is 53.  This option is mainly intended for server
2559                 testing;
2560                 a server using a port other than 53 will not be able to
2561                 communicate with
2562                 the global DNS.
2563               </p></dd>
2564 <dt><span class="term"><span><strong class="command">random-device</strong></span></span></dt>
2565 <dd><p>
2566                 The source of entropy to be used by the server.  Entropy is
2567                 primarily needed
2568                 for DNSSEC operations, such as TKEY transactions and dynamic
2569                 update of signed
2570                 zones.  This options specifies the device (or file) from which
2571                 to read
2572                 entropy.  If this is a file, operations requiring entropy will
2573                 fail when the
2574                 file has been exhausted.  If not specified, the default value
2575                 is
2576                 <code class="filename">/dev/random</code>
2577                 (or equivalent) when present, and none otherwise.  The
2578                 <span><strong class="command">random-device</strong></span> option takes
2579                 effect during
2580                 the initial configuration load at server startup time and
2581                 is ignored on subsequent reloads.
2582               </p></dd>
2583 <dt><span class="term"><span><strong class="command">preferred-glue</strong></span></span></dt>
2584 <dd><p>
2585                 If specified, the listed type (A or AAAA) will be emitted
2586                 before other glue
2587                 in the additional section of a query response.
2588                 The default is not to prefer any type (NONE).
2589               </p></dd>
2590 <dt>
2591 <a name="root_delegation_only"></a><span class="term"><span><strong class="command">root-delegation-only</strong></span></span>
2592 </dt>
2593 <dd>
2594 <p>
2595                 Turn on enforcement of delegation-only in TLDs
2596                 (top level domains) and root zones with an optional
2597                 exclude list.
2598               </p>
2599 <p>
2600                 DS queries are expected to be made to and be answered by
2601                 delegation only zones.  Such queries and responses are
2602                 treated as an exception to delegation-only processing
2603                 and are not converted to NXDOMAIN responses provided
2604                 a CNAME is not discovered at the query name.
2605               </p>
2606 <p>
2607                 If a delegation only zone server also serves a child
2608                 zone it is not always possible to determine whether
2609                 an answer comes from the delegation only zone or the
2610                 child zone.  SOA NS and DNSKEY records are apex
2611                 only records and a matching response that contains
2612                 these records or DS is treated as coming from a
2613                 child zone.  RRSIG records are also examined to see
2614                 if they are signed by a child zone or not.  The
2615                 authority section is also examined to see if there
2616                 is evidence that the answer is from the child zone.
2617                 Answers that are determined to be from a child zone
2618                 are not converted to NXDOMAIN responses.  Despite
2619                 all these checks there is still a possibility of
2620                 false negatives when a child zone is being served.
2621               </p>
2622 <p>
2623                 Similarly false positives can arise from empty nodes
2624                 (no records at the name) in the delegation only zone
2625                 when the query type is not ANY.
2626               </p>
2627 <p>
2628                 Note some TLDs are not delegation only (e.g. "DE", "LV",
2629                 "US" and "MUSEUM").  This list is not exhaustive.
2630               </p>
2631 <pre class="programlisting">
2632 options {
2633         root-delegation-only exclude { "de"; "lv"; "us"; "museum"; };
2634 };
2635 </pre>
2636 </dd>
2637 <dt><span class="term"><span><strong class="command">disable-algorithms</strong></span></span></dt>
2638 <dd><p>
2639                 Disable the specified DNSSEC algorithms at and below the
2640                 specified name.
2641                 Multiple <span><strong class="command">disable-algorithms</strong></span>
2642                 statements are allowed.
2643                 Only the most specific will be applied.
2644               </p></dd>
2645 <dt><span class="term"><span><strong class="command">dnssec-lookaside</strong></span></span></dt>
2646 <dd>
2647 <p>
2648                 When set, <span><strong class="command">dnssec-lookaside</strong></span> provides the
2649                 validator with an alternate method to validate DNSKEY
2650                 records at the top of a zone.  When a DNSKEY is at or
2651                 below a domain specified by the deepest
2652                 <span><strong class="command">dnssec-lookaside</strong></span>, and the normal DNSSEC
2653                 validation has left the key untrusted, the trust-anchor
2654                 will be appended to the key name and a DLV record will be
2655                 looked up to see if it can validate the key.  If the DLV
2656                 record validates a DNSKEY (similarly to the way a DS
2657                 record does) the DNSKEY RRset is deemed to be trusted.
2658               </p>
2659 <p>
2660                 If <span><strong class="command">dnssec-lookaside</strong></span> is set to
2661                 <strong class="userinput"><code>auto</code></strong>, then built-in default
2662                 values for the DLV domain and trust anchor will be
2663                 used, along with a built-in key for validation.
2664               </p>
2665 <p>
2666                 The default DLV key is stored in the file
2667                 <code class="filename">bind.keys</code>;
2668                 <span><strong class="command">named</strong></span> will load that key at
2669                 startup if <span><strong class="command">dnssec-lookaside</strong></span> is set to
2670                 <code class="constant">auto</code>.  A copy of the file is
2671                 installed along with <acronym class="acronym">BIND</acronym> 9, and is
2672                 current as of the release date.  If the DLV key expires, a
2673                 new copy of <code class="filename">bind.keys</code> can be downloaded
2674                 from <a href="" target="_top">https://www.isc.org/solutions/dlv</a>.
2675               </p>
2676 <p>
2677                 (To prevent problems if <code class="filename">bind.keys</code> is
2678                 not found, the current key is also compiled in to
2679                 <span><strong class="command">named</strong></span>.  Relying on this is not
2680                 recommended, however, as it requires <span><strong class="command">named</strong></span>
2681                 to be recompiled with a new key when the DLV key expires.)
2682               </p>
2683 <p>
2684                 NOTE: <span><strong class="command">named</strong></span> only loads certain specific
2685                 keys from <code class="filename">bind.keys</code>:  those for the
2686                 DLV zone and for the DNS root zone.  The file cannot be
2687                 used to store keys for other zones.
2688               </p>
2689 </dd>
2690 <dt><span class="term"><span><strong class="command">dnssec-must-be-secure</strong></span></span></dt>
2691 <dd><p>
2692                 Specify hierarchies which must be or may not be secure
2693                 (signed and validated).  If <strong class="userinput"><code>yes</code></strong>,
2694                 then <span><strong class="command">named</strong></span> will only accept answers if
2695                 they are secure.  If <strong class="userinput"><code>no</code></strong>, then normal
2696                 DNSSEC validation applies allowing for insecure answers to
2697                 be accepted.  The specified domain must be under a
2698                 <span><strong class="command">trusted-keys</strong></span> or
2699                 <span><strong class="command">managed-keys</strong></span> statement, or
2700                 <span><strong class="command">dnssec-lookaside</strong></span> must be active.
2701               </p></dd>
2702 <dt><span class="term"><span><strong class="command">dns64</strong></span></span></dt>
2703 <dd>
2704 <p>
2705                 This directive instructs <span><strong class="command">named</strong></span> to
2706                 return mapped IPv4 addresses to AAAA queries when
2707                 there are no AAAA records.  It is intended to be
2708                 used in conjunction with a NAT64.  Each
2709                 <span><strong class="command">dns64</strong></span> defines one DNS64 prefix.
2710                 Multiple DNS64 prefixes can be defined.
2711               </p>
2712 <p>
2713                 Compatible IPv6 prefixes have lengths of 32, 40, 48, 56,
2714                 64 and 96 as per RFC 6052.
2715               </p>
2716 <p>
2717                 Additionally a reverse IP6.ARPA zone will be created for
2718                 the prefix to provide a mapping from the IP6.ARPA names
2719                 to the corresponding IN-ADDR.ARPA names using synthesized
2720                 CNAMEs.  <span><strong class="command">dns64-server</strong></span> and
2721                 <span><strong class="command">dns64-contact</strong></span> can be used to specify
2722                 the name of the server and contact for the zones. These
2723                 are settable at the view / options level.  These are
2724                 not settable on a per-prefix basis.
2725               </p>
2726 <p>
2727                 Each <span><strong class="command">dns64</strong></span> supports an optional
2728                 <span><strong class="command">clients</strong></span> ACL that determines which
2729                 clients are affected by this directive.  If not defined,
2730                 it defaults to <strong class="userinput"><code>any;</code></strong>.
2731               </p>
2732 <p>
2733                 Each <span><strong class="command">dns64</strong></span> supports an optional
2734                 <span><strong class="command">mapped</strong></span> ACL that selects which
2735                 IPv4 addresses are to be mapped in the corresponding
2736                 A RRset.  If not defined it defaults to
2737                 <strong class="userinput"><code>any;</code></strong>.
2738               </p>
2739 <p>
2740                 Normally, DNS64 won't apply to a domain name that
2741                 owns one or more AAAA records; these records will
2742                 simply be returned.  The optional
2743                 <span><strong class="command">exclude</strong></span> ACL allows specification
2744                 of a list of IPv6 addresses that will be ignored
2745                 if they appear in a domain name's AAAA records, and
2746                 DNS64 will be applied to any A records the domain
2747                 name owns.  If not defined, <span><strong class="command">exclude</strong></span>
2748                 defaults to none.
2749               </p>
2750 <p>
2751                 A optional <span><strong class="command">suffix</strong></span> can also
2752                 be defined to set the bits trailing the mapped
2753                 IPv4 address bits.  By default these bits are
2754                 set to <strong class="userinput"><code>::</code></strong>.  The bits
2755                 matching the prefix and mapped IPv4 address
2756                 must be zero.
2757               </p>
2758 <p>
2759                 If <span><strong class="command">recursive-only</strong></span> is set to
2760                 <span><strong class="command">yes</strong></span> the DNS64 synthesis will
2761                 only happen for recursive queries.  The default
2762                 is <span><strong class="command">no</strong></span>.
2763               </p>
2764 <p>
2765                 If <span><strong class="command">break-dnssec</strong></span> is set to
2766                 <span><strong class="command">yes</strong></span> the DNS64 synthesis will
2767                 happen even if the result, if validated, would
2768                 cause a DNSSEC validation failure.  If this option
2769                 is set to <span><strong class="command">no</strong></span> (the default), the DO
2770                 is set on the incoming query, and there are RRSIGs on
2771                 the applicable records, then synthesis will not happen.
2772               </p>
2773 <pre class="programlisting">
2774         acl rfc1918 { 10/8; 192.168/16; 172.16/12; };
2775
2776         dns64 64:FF9B::/96 {
2777                 clients { any; };
2778                 mapped { !rfc1918; any; };
2779                 exclude { 64:FF9B::/96; ::ffff:0000:0000/96; };
2780                 suffix ::;
2781         };
2782 </pre>
2783 </dd>
2784 </dl></div>
2785 <div class="sect3" lang="en">
2786 <div class="titlepage"><div><div><h4 class="title">
2787 <a name="boolean_options"></a>Boolean Options</h4></div></div></div>
2788 <div class="variablelist"><dl>
2789 <dt><span class="term"><span><strong class="command">allow-new-zones</strong></span></span></dt>
2790 <dd><p>
2791                   If <strong class="userinput"><code>yes</code></strong>, then zones can be
2792                   added at runtime via <span><strong class="command">rndc addzone</strong></span>
2793                   or deleted via <span><strong class="command">rndc delzone</strong></span>.
2794                   The default is <strong class="userinput"><code>no</code></strong>.
2795                 </p></dd>
2796 <dt><span class="term"><span><strong class="command">auth-nxdomain</strong></span></span></dt>
2797 <dd><p>
2798                   If <strong class="userinput"><code>yes</code></strong>, then the <span><strong class="command">AA</strong></span> bit
2799                   is always set on NXDOMAIN responses, even if the server is
2800                   not actually
2801                   authoritative. The default is <strong class="userinput"><code>no</code></strong>;
2802                   this is
2803                   a change from <acronym class="acronym">BIND</acronym> 8. If you
2804                   are using very old DNS software, you
2805                   may need to set it to <strong class="userinput"><code>yes</code></strong>.
2806                 </p></dd>
2807 <dt><span class="term"><span><strong class="command">deallocate-on-exit</strong></span></span></dt>
2808 <dd><p>
2809                   This option was used in <acronym class="acronym">BIND</acronym>
2810                   8 to enable checking
2811                   for memory leaks on exit. <acronym class="acronym">BIND</acronym> 9 ignores the option and always performs
2812                   the checks.
2813                 </p></dd>
2814 <dt><span class="term"><span><strong class="command">memstatistics</strong></span></span></dt>
2815 <dd><p>
2816                   Write memory statistics to the file specified by
2817                   <span><strong class="command">memstatistics-file</strong></span> at exit.
2818                   The default is <strong class="userinput"><code>no</code></strong> unless
2819                   '-m record' is specified on the command line in
2820                   which case it is <strong class="userinput"><code>yes</code></strong>.
2821                 </p></dd>
2822 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
2823 <dd>
2824 <p>
2825                   If <strong class="userinput"><code>yes</code></strong>, then the
2826                   server treats all zones as if they are doing zone transfers
2827                   across
2828                   a dial-on-demand dialup link, which can be brought up by
2829                   traffic
2830                   originating from this server. This has different effects
2831                   according
2832                   to zone type and concentrates the zone maintenance so that
2833                   it all
2834                   happens in a short interval, once every <span><strong class="command">heartbeat-interval</strong></span> and
2835                   hopefully during the one call. It also suppresses some of
2836                   the normal
2837                   zone maintenance traffic. The default is <strong class="userinput"><code>no</code></strong>.
2838                 </p>
2839 <p>
2840                   The <span><strong class="command">dialup</strong></span> option
2841                   may also be specified in the <span><strong class="command">view</strong></span> and
2842                   <span><strong class="command">zone</strong></span> statements,
2843                   in which case it overrides the global <span><strong class="command">dialup</strong></span>
2844                   option.
2845                 </p>
2846 <p>
2847                   If the zone is a master zone, then the server will send out a
2848                   NOTIFY
2849                   request to all the slaves (default). This should trigger the
2850                   zone serial
2851                   number check in the slave (providing it supports NOTIFY)
2852                   allowing the slave
2853                   to verify the zone while the connection is active.
2854                   The set of servers to which NOTIFY is sent can be controlled
2855                   by
2856                   <span><strong class="command">notify</strong></span> and <span><strong class="command">also-notify</strong></span>.
2857                 </p>
2858 <p>
2859                   If the
2860                   zone is a slave or stub zone, then the server will suppress
2861                   the regular
2862                   "zone up to date" (refresh) queries and only perform them
2863                   when the
2864                   <span><strong class="command">heartbeat-interval</strong></span> expires in
2865                   addition to sending
2866                   NOTIFY requests.
2867                 </p>
2868 <p>
2869                   Finer control can be achieved by using
2870                   <strong class="userinput"><code>notify</code></strong> which only sends NOTIFY
2871                   messages,
2872                   <strong class="userinput"><code>notify-passive</code></strong> which sends NOTIFY
2873                   messages and
2874                   suppresses the normal refresh queries, <strong class="userinput"><code>refresh</code></strong>
2875                   which suppresses normal refresh processing and sends refresh
2876                   queries
2877                   when the <span><strong class="command">heartbeat-interval</strong></span>
2878                   expires, and
2879                   <strong class="userinput"><code>passive</code></strong> which just disables normal
2880                   refresh
2881                   processing.
2882                 </p>
2883 <div class="informaltable"><table border="1">
2884 <colgroup>
2885 <col>
2886 <col>
2887 <col>
2888 <col>
2889 </colgroup>
2890 <tbody>
2891 <tr>
2892 <td>
2893                           <p>
2894                             dialup mode
2895                           </p>
2896                         </td>
2897 <td>
2898                           <p>
2899                             normal refresh
2900                           </p>
2901                         </td>
2902 <td>
2903                           <p>
2904                             heart-beat refresh
2905                           </p>
2906                         </td>
2907 <td>
2908                           <p>
2909                             heart-beat notify
2910                           </p>
2911                         </td>
2912 </tr>
2913 <tr>
2914 <td>
2915                           <p><span><strong class="command">no</strong></span> (default)</p>
2916                         </td>
2917 <td>
2918                           <p>
2919                             yes
2920                           </p>
2921                         </td>
2922 <td>
2923                           <p>
2924                             no
2925                           </p>
2926                         </td>
2927 <td>
2928                           <p>
2929                             no
2930                           </p>
2931                         </td>
2932 </tr>
2933 <tr>
2934 <td>
2935                           <p><span><strong class="command">yes</strong></span></p>
2936                         </td>
2937 <td>
2938                           <p>
2939                             no
2940                           </p>
2941                         </td>
2942 <td>
2943                           <p>
2944                             yes
2945                           </p>
2946                         </td>
2947 <td>
2948                           <p>
2949                             yes
2950                           </p>
2951                         </td>
2952 </tr>
2953 <tr>
2954 <td>
2955                           <p><span><strong class="command">notify</strong></span></p>
2956                         </td>
2957 <td>
2958                           <p>
2959                             yes
2960                           </p>
2961                         </td>
2962 <td>
2963                           <p>
2964                             no
2965                           </p>
2966                         </td>
2967 <td>
2968                           <p>
2969                             yes
2970                           </p>
2971                         </td>
2972 </tr>
2973 <tr>
2974 <td>
2975                           <p><span><strong class="command">refresh</strong></span></p>
2976                         </td>
2977 <td>
2978                           <p>
2979                             no
2980                           </p>
2981                         </td>
2982 <td>
2983                           <p>
2984                             yes
2985                           </p>
2986                         </td>
2987 <td>
2988                           <p>
2989                             no
2990                           </p>
2991                         </td>
2992 </tr>
2993 <tr>
2994 <td>
2995                           <p><span><strong class="command">passive</strong></span></p>
2996                         </td>
2997 <td>
2998                           <p>
2999                             no
3000                           </p>
3001                         </td>
3002 <td>
3003                           <p>
3004                             no
3005                           </p>
3006                         </td>
3007 <td>
3008                           <p>
3009                             no
3010                           </p>
3011                         </td>
3012 </tr>
3013 <tr>
3014 <td>
3015                           <p><span><strong class="command">notify-passive</strong></span></p>
3016                         </td>
3017 <td>
3018                           <p>
3019                             no
3020                           </p>
3021                         </td>
3022 <td>
3023                           <p>
3024                             no
3025                           </p>
3026                         </td>
3027 <td>
3028                           <p>
3029                             yes
3030                           </p>
3031                         </td>
3032 </tr>
3033 </tbody>
3034 </table></div>
3035 <p>
3036                   Note that normal NOTIFY processing is not affected by
3037                   <span><strong class="command">dialup</strong></span>.
3038                 </p>
3039 </dd>
3040 <dt><span class="term"><span><strong class="command">fake-iquery</strong></span></span></dt>
3041 <dd><p>
3042                   In <acronym class="acronym">BIND</acronym> 8, this option
3043                   enabled simulating the obsolete DNS query type
3044                   IQUERY. <acronym class="acronym">BIND</acronym> 9 never does
3045                   IQUERY simulation.
3046                 </p></dd>
3047 <dt><span class="term"><span><strong class="command">fetch-glue</strong></span></span></dt>
3048 <dd><p>
3049                   This option is obsolete.
3050                   In BIND 8, <strong class="userinput"><code>fetch-glue yes</code></strong>
3051                   caused the server to attempt to fetch glue resource records
3052                   it
3053                   didn't have when constructing the additional
3054                   data section of a response.  This is now considered a bad
3055                   idea
3056                   and BIND 9 never does it.
3057                 </p></dd>
3058 <dt><span class="term"><span><strong class="command">flush-zones-on-shutdown</strong></span></span></dt>
3059 <dd><p>
3060                   When the nameserver exits due receiving SIGTERM,
3061                   flush or do not flush any pending zone writes.  The default
3062                   is
3063                   <span><strong class="command">flush-zones-on-shutdown</strong></span> <strong class="userinput"><code>no</code></strong>.
3064                 </p></dd>
3065 <dt><span class="term"><span><strong class="command">has-old-clients</strong></span></span></dt>
3066 <dd><p>
3067                   This option was incorrectly implemented
3068                   in <acronym class="acronym">BIND</acronym> 8, and is ignored by <acronym class="acronym">BIND</acronym> 9.
3069                   To achieve the intended effect
3070                   of
3071                   <span><strong class="command">has-old-clients</strong></span> <strong class="userinput"><code>yes</code></strong>, specify
3072                   the two separate options <span><strong class="command">auth-nxdomain</strong></span> <strong class="userinput"><code>yes</code></strong>
3073                   and <span><strong class="command">rfc2308-type1</strong></span> <strong class="userinput"><code>no</code></strong> instead.
3074                 </p></dd>
3075 <dt><span class="term"><span><strong class="command">host-statistics</strong></span></span></dt>
3076 <dd><p>
3077                   In BIND 8, this enables keeping of
3078                   statistics for every host that the name server interacts
3079                   with.
3080                   Not implemented in BIND 9.
3081                 </p></dd>
3082 <dt><span class="term"><span><strong class="command">maintain-ixfr-base</strong></span></span></dt>
3083 <dd><p>
3084                   <span class="emphasis"><em>This option is obsolete</em></span>.
3085                   It was used in <acronym class="acronym">BIND</acronym> 8 to
3086                   determine whether a transaction log was
3087                   kept for Incremental Zone Transfer. <acronym class="acronym">BIND</acronym> 9 maintains a transaction
3088                   log whenever possible.  If you need to disable outgoing
3089                   incremental zone
3090                   transfers, use <span><strong class="command">provide-ixfr</strong></span> <strong class="userinput"><code>no</code></strong>.
3091                 </p></dd>
3092 <dt><span class="term"><span><strong class="command">minimal-responses</strong></span></span></dt>
3093 <dd><p>
3094                   If <strong class="userinput"><code>yes</code></strong>, then when generating
3095                   responses the server will only add records to the authority
3096                   and additional data sections when they are required (e.g.
3097                   delegations, negative responses).  This may improve the
3098                   performance of the server.
3099                   The default is <strong class="userinput"><code>no</code></strong>.
3100                 </p></dd>
3101 <dt><span class="term"><span><strong class="command">multiple-cnames</strong></span></span></dt>
3102 <dd><p>
3103                   This option was used in <acronym class="acronym">BIND</acronym> 8 to allow
3104                   a domain name to have multiple CNAME records in violation of
3105                   the DNS standards.  <acronym class="acronym">BIND</acronym> 9.2 onwards
3106                   always strictly enforces the CNAME rules both in master
3107                   files and dynamic updates.
3108                 </p></dd>
3109 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
3110 <dd>
3111 <p>
3112                   If <strong class="userinput"><code>yes</code></strong> (the default),
3113                   DNS NOTIFY messages are sent when a zone the server is
3114                   authoritative for
3115                   changes, see <a href="Bv9ARM.ch04.html#notify" title="Notify">the section called &#8220;Notify&#8221;</a>.  The messages are
3116                   sent to the
3117                   servers listed in the zone's NS records (except the master
3118                   server identified
3119                   in the SOA MNAME field), and to any servers listed in the
3120                   <span><strong class="command">also-notify</strong></span> option.
3121                 </p>
3122 <p>
3123                   If <strong class="userinput"><code>master-only</code></strong>, notifies are only
3124                   sent
3125                   for master zones.
3126                   If <strong class="userinput"><code>explicit</code></strong>, notifies are sent only
3127                   to
3128                   servers explicitly listed using <span><strong class="command">also-notify</strong></span>.
3129                   If <strong class="userinput"><code>no</code></strong>, no notifies are sent.
3130                 </p>
3131 <p>
3132                   The <span><strong class="command">notify</strong></span> option may also be
3133                   specified in the <span><strong class="command">zone</strong></span>
3134                   statement,
3135                   in which case it overrides the <span><strong class="command">options notify</strong></span> statement.
3136                   It would only be necessary to turn off this option if it
3137                   caused slaves
3138                   to crash.
3139                 </p>
3140 </dd>
3141 <dt><span class="term"><span><strong class="command">notify-to-soa</strong></span></span></dt>
3142 <dd><p>
3143                   If <strong class="userinput"><code>yes</code></strong> do not check the nameservers
3144                   in the NS RRset against the SOA MNAME.  Normally a NOTIFY
3145                   message is not sent to the SOA MNAME (SOA ORIGIN) as it is
3146                   supposed to contain the name of the ultimate master.
3147                   Sometimes, however, a slave is listed as the SOA MNAME in
3148                   hidden master configurations and in that case you would
3149                   want the ultimate master to still send NOTIFY messages to
3150                   all the nameservers listed in the NS RRset.
3151                 </p></dd>
3152 <dt><span class="term"><span><strong class="command">recursion</strong></span></span></dt>
3153 <dd><p>
3154                   If <strong class="userinput"><code>yes</code></strong>, and a
3155                   DNS query requests recursion, then the server will attempt
3156                   to do
3157                   all the work required to answer the query. If recursion is
3158                   off
3159                   and the server does not already know the answer, it will
3160                   return a
3161                   referral response. The default is
3162                   <strong class="userinput"><code>yes</code></strong>.
3163                   Note that setting <span><strong class="command">recursion no</strong></span> does not prevent
3164                   clients from getting data from the server's cache; it only
3165                   prevents new data from being cached as an effect of client
3166                   queries.
3167                   Caching may still occur as an effect the server's internal
3168                   operation, such as NOTIFY address lookups.
3169                   See also <span><strong class="command">fetch-glue</strong></span> above.
3170                 </p></dd>
3171 <dt><span class="term"><span><strong class="command">rfc2308-type1</strong></span></span></dt>
3172 <dd>
3173 <p>
3174                   Setting this to <strong class="userinput"><code>yes</code></strong> will
3175                   cause the server to send NS records along with the SOA
3176                   record for negative
3177                   answers. The default is <strong class="userinput"><code>no</code></strong>.
3178                 </p>
3179 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3180 <h3 class="title">Note</h3>
3181 <p>
3182                     Not yet implemented in <acronym class="acronym">BIND</acronym>
3183                     9.
3184                   </p>
3185 </div>
3186 </dd>
3187 <dt><span class="term"><span><strong class="command">use-id-pool</strong></span></span></dt>
3188 <dd><p>
3189                   <span class="emphasis"><em>This option is obsolete</em></span>.
3190                   <acronym class="acronym">BIND</acronym> 9 always allocates query
3191                   IDs from a pool.
3192                 </p></dd>
3193 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
3194 <dd><p>
3195                   If <strong class="userinput"><code>yes</code></strong>, the server will collect
3196                   statistical data on all zones (unless specifically turned
3197                   off
3198                   on a per-zone basis by specifying <span><strong class="command">zone-statistics no</strong></span>
3199                   in the <span><strong class="command">zone</strong></span> statement).
3200                   The default is <strong class="userinput"><code>no</code></strong>.
3201                   These statistics may be accessed
3202                   using <span><strong class="command">rndc stats</strong></span>, which will
3203                   dump them to the file listed
3204                   in the <span><strong class="command">statistics-file</strong></span>.  See
3205                   also <a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
3206                 </p></dd>
3207 <dt><span class="term"><span><strong class="command">use-ixfr</strong></span></span></dt>
3208 <dd><p>
3209                   <span class="emphasis"><em>This option is obsolete</em></span>.
3210                   If you need to disable IXFR to a particular server or
3211                   servers, see
3212                   the information on the <span><strong class="command">provide-ixfr</strong></span> option
3213                   in <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3214             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3215             Usage&#8221;</a>.
3216                   See also
3217                   <a href="Bv9ARM.ch04.html#incremental_zone_transfers" title="Incremental Zone Transfers (IXFR)">the section called &#8220;Incremental Zone Transfers (IXFR)&#8221;</a>.
3218                 </p></dd>
3219 <dt><span class="term"><span><strong class="command">provide-ixfr</strong></span></span></dt>
3220 <dd><p>
3221                   See the description of
3222                   <span><strong class="command">provide-ixfr</strong></span> in
3223                   <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3224             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3225             Usage&#8221;</a>.
3226                 </p></dd>
3227 <dt><span class="term"><span><strong class="command">request-ixfr</strong></span></span></dt>
3228 <dd><p>
3229                   See the description of
3230                   <span><strong class="command">request-ixfr</strong></span> in
3231                   <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3232             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3233             Usage&#8221;</a>.
3234                 </p></dd>
3235 <dt><span class="term"><span><strong class="command">treat-cr-as-space</strong></span></span></dt>
3236 <dd><p>
3237                   This option was used in <acronym class="acronym">BIND</acronym>
3238                   8 to make
3239                   the server treat carriage return ("<span><strong class="command">\r</strong></span>") characters the same way
3240                   as a space or tab character,
3241                   to facilitate loading of zone files on a UNIX system that
3242                   were generated
3243                   on an NT or DOS machine. In <acronym class="acronym">BIND</acronym> 9, both UNIX "<span><strong class="command">\n</strong></span>"
3244                   and NT/DOS "<span><strong class="command">\r\n</strong></span>" newlines
3245                   are always accepted,
3246                   and the option is ignored.
3247                 </p></dd>
3248 <dt>
3249 <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>
3250 </dt>
3251 <dd>
3252 <p>
3253                   These options control the behavior of an authoritative
3254                   server when
3255                   answering queries which have additional data, or when
3256                   following CNAME
3257                   and DNAME chains.
3258                 </p>
3259 <p>
3260                   When both of these options are set to <strong class="userinput"><code>yes</code></strong>
3261                   (the default) and a
3262                   query is being answered from authoritative data (a zone
3263                   configured into the server), the additional data section of
3264                   the
3265                   reply will be filled in using data from other authoritative
3266                   zones
3267                   and from the cache.  In some situations this is undesirable,
3268                   such
3269                   as when there is concern over the correctness of the cache,
3270                   or
3271                   in servers where slave zones may be added and modified by
3272                   untrusted third parties.  Also, avoiding
3273                   the search for this additional data will speed up server
3274                   operations
3275                   at the possible expense of additional queries to resolve
3276                   what would
3277                   otherwise be provided in the additional section.
3278                 </p>
3279 <p>
3280                   For example, if a query asks for an MX record for host <code class="literal">foo.example.com</code>,
3281                   and the record found is "<code class="literal">MX 10 mail.example.net</code>", normally the address
3282                   records (A and AAAA) for <code class="literal">mail.example.net</code> will be provided as well,
3283                   if known, even though they are not in the example.com zone.
3284                   Setting these options to <span><strong class="command">no</strong></span>
3285                   disables this behavior and makes
3286                   the server only search for additional data in the zone it
3287                   answers from.
3288                 </p>
3289 <p>
3290                   These options are intended for use in authoritative-only
3291                   servers, or in authoritative-only views.  Attempts to set
3292                   them to <span><strong class="command">no</strong></span> without also
3293                   specifying
3294                   <span><strong class="command">recursion no</strong></span> will cause the
3295                   server to
3296                   ignore the options and log a warning message.
3297                 </p>
3298 <p>
3299                   Specifying <span><strong class="command">additional-from-cache no</strong></span> actually
3300                   disables the use of the cache not only for additional data
3301                   lookups
3302                   but also when looking up the answer.  This is usually the
3303                   desired
3304                   behavior in an authoritative-only server where the
3305                   correctness of
3306                   the cached data is an issue.
3307                 </p>
3308 <p>
3309                   When a name server is non-recursively queried for a name
3310                   that is not
3311                   below the apex of any served zone, it normally answers with
3312                   an
3313                   "upwards referral" to the root servers or the servers of
3314                   some other
3315                   known parent of the query name.  Since the data in an
3316                   upwards referral
3317                   comes from the cache, the server will not be able to provide
3318                   upwards
3319                   referrals when <span><strong class="command">additional-from-cache no</strong></span>
3320                   has been specified.  Instead, it will respond to such
3321                   queries
3322                   with REFUSED.  This should not cause any problems since
3323                   upwards referrals are not required for the resolution
3324                   process.
3325                 </p>
3326 </dd>
3327 <dt><span class="term"><span><strong class="command">match-mapped-addresses</strong></span></span></dt>
3328 <dd>
3329 <p>
3330                   If <strong class="userinput"><code>yes</code></strong>, then an
3331                   IPv4-mapped IPv6 address will match any address match
3332                   list entries that match the corresponding IPv4 address.
3333                 </p>
3334 <p>
3335                   This option was introduced to work around a kernel quirk
3336                   in some operating systems that causes IPv4 TCP
3337                   connections, such as zone transfers, to be accepted on an
3338                   IPv6 socket using mapped addresses.  This caused address
3339                   match lists designed for IPv4 to fail to match.  However,
3340                   <span><strong class="command">named</strong></span> now solves this problem
3341                   internally.  The use of this option is discouraged.
3342                 </p>
3343 </dd>
3344 <dt><span class="term"><span><strong class="command">filter-aaaa-on-v4</strong></span></span></dt>
3345 <dd>
3346 <p>
3347                   This option is only available when
3348                   <acronym class="acronym">BIND</acronym> 9 is compiled with the
3349                   <strong class="userinput"><code>--enable-filter-aaaa</code></strong> option on the
3350                   "configure" command line.  It is intended to help the
3351                   transition from IPv4 to IPv6 by not giving IPv6 addresses
3352                   to DNS clients unless they have connections to the IPv6
3353                   Internet.  This is not recommended unless absolutely
3354                   necessary.  The default is <strong class="userinput"><code>no</code></strong>.
3355                   The <span><strong class="command">filter-aaaa-on-v4</strong></span> option
3356                   may also be specified in <span><strong class="command">view</strong></span> statements
3357                   to override the global <span><strong class="command">filter-aaaa-on-v4</strong></span>
3358                   option.
3359                 </p>
3360 <p>
3361                   If <strong class="userinput"><code>yes</code></strong>,
3362                   the DNS client is at an IPv4 address, in <span><strong class="command">filter-aaaa</strong></span>,
3363                   and if the response does not include DNSSEC signatures,
3364                   then all AAAA records are deleted from the response.
3365                   This filtering applies to all responses and not only
3366                   authoritative responses.
3367                 </p>
3368 <p>
3369                   If <strong class="userinput"><code>break-dnssec</code></strong>,
3370                   then AAAA records are deleted even when dnssec is enabled.
3371                   As suggested by the name, this makes the response not verify,
3372                   because the DNSSEC protocol is designed detect deletions.
3373                 </p>
3374 <p>
3375                   This mechanism can erroneously cause other servers to
3376                   not give AAAA records to their clients.
3377                   A recursing server with both IPv6 and IPv4 network connections
3378                   that queries an authoritative server using this mechanism
3379                   via IPv4 will be denied AAAA records even if its client is
3380                   using IPv6.
3381                 </p>
3382 <p>
3383                   This mechanism is applied to authoritative as well as
3384                   non-authoritative records.
3385                   A client using IPv4 that is not allowed recursion can
3386                   erroneously be given AAAA records because the server is not
3387                   allowed to check for A records.
3388                 </p>
3389 <p>
3390                   Some AAAA records are given to IPv4 clients in glue records.
3391                   IPv4 clients that are servers can then erroneously
3392                   answer requests for AAAA records received via IPv4.
3393                 </p>
3394 </dd>
3395 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
3396 <dd>
3397 <p>
3398                   When <strong class="userinput"><code>yes</code></strong> and the server loads a new version of a master
3399                   zone from its zone file or receives a new version of a slave
3400                   file by a non-incremental zone transfer, it will compare
3401                   the new version to the previous one and calculate a set
3402                   of differences.  The differences are then logged in the
3403                   zone's journal file such that the changes can be transmitted
3404                   to downstream slaves as an incremental zone transfer.
3405                 </p>
3406 <p>
3407                   By allowing incremental zone transfers to be used for
3408                   non-dynamic zones, this option saves bandwidth at the
3409                   expense of increased CPU and memory consumption at the
3410                   master.
3411                   In particular, if the new version of a zone is completely
3412                   different from the previous one, the set of differences
3413                   will be of a size comparable to the combined size of the
3414                   old and new zone version, and the server will need to
3415                   temporarily allocate memory to hold this complete
3416                   difference set.
3417                 </p>
3418 <p><span><strong class="command">ixfr-from-differences</strong></span>
3419                   also accepts <span><strong class="command">master</strong></span> and
3420                   <span><strong class="command">slave</strong></span> at the view and options
3421                   levels which causes
3422                   <span><strong class="command">ixfr-from-differences</strong></span> to be enabled for
3423                   all <span><strong class="command">master</strong></span> or
3424                   <span><strong class="command">slave</strong></span> zones respectively.
3425                   It is off by default.
3426                 </p>
3427 </dd>
3428 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
3429 <dd><p>
3430                   This should be set when you have multiple masters for a zone
3431                   and the
3432                   addresses refer to different machines.  If <strong class="userinput"><code>yes</code></strong>, <span><strong class="command">named</strong></span> will
3433                   not log
3434                   when the serial number on the master is less than what <span><strong class="command">named</strong></span>
3435                   currently
3436                   has.  The default is <strong class="userinput"><code>no</code></strong>.
3437                 </p></dd>
3438 <dt><span class="term"><span><strong class="command">dnssec-enable</strong></span></span></dt>
3439 <dd><p>
3440                   Enable DNSSEC support in <span><strong class="command">named</strong></span>.  Unless set to <strong class="userinput"><code>yes</code></strong>,
3441                   <span><strong class="command">named</strong></span> behaves as if it does not support DNSSEC.
3442                   The default is <strong class="userinput"><code>yes</code></strong>.
3443                 </p></dd>
3444 <dt><span class="term"><span><strong class="command">dnssec-validation</strong></span></span></dt>
3445 <dd><p>
3446                   Enable DNSSEC validation in <span><strong class="command">named</strong></span>.
3447                   Note <span><strong class="command">dnssec-enable</strong></span> also needs to be
3448                   set to <strong class="userinput"><code>yes</code></strong> to be effective.
3449                   If set to <strong class="userinput"><code>no</code></strong>, DNSSEC validation
3450                   is disabled.  If set to <strong class="userinput"><code>auto</code></strong>,
3451                   DNSSEC validation is enabled, and a default
3452                   trust-anchor for the DNS root zone is used.  If set to
3453                   <strong class="userinput"><code>yes</code></strong>, DNSSEC validation is enabled,
3454                   but a trust anchor must be manually configured using
3455                   a <span><strong class="command">trusted-keys</strong></span> or
3456                   <span><strong class="command">managed-keys</strong></span> statement.  The default
3457                   is <strong class="userinput"><code>yes</code></strong>.
3458                 </p></dd>
3459 <dt><span class="term"><span><strong class="command">dnssec-accept-expired</strong></span></span></dt>
3460 <dd><p>
3461                   Accept expired signatures when verifying DNSSEC signatures.
3462                   The default is <strong class="userinput"><code>no</code></strong>.
3463                   Setting this option to <strong class="userinput"><code>yes</code></strong>
3464                   leaves <span><strong class="command">named</strong></span> vulnerable to
3465                   replay attacks.
3466                 </p></dd>
3467 <dt><span class="term"><span><strong class="command">querylog</strong></span></span></dt>
3468 <dd><p>
3469                   Specify whether query logging should be started when <span><strong class="command">named</strong></span>
3470                   starts.
3471                   If <span><strong class="command">querylog</strong></span> is not specified,
3472                   then the query logging
3473                   is determined by the presence of the logging category <span><strong class="command">queries</strong></span>.
3474                 </p></dd>
3475 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
3476 <dd>
3477 <p>
3478                   This option is used to restrict the character set and syntax
3479                   of
3480                   certain domain names in master files and/or DNS responses
3481                   received
3482                   from the network.  The default varies according to usage
3483                   area.  For
3484                   <span><strong class="command">master</strong></span> zones the default is <span><strong class="command">fail</strong></span>.
3485                   For <span><strong class="command">slave</strong></span> zones the default
3486                   is <span><strong class="command">warn</strong></span>.
3487                   For answers received from the network (<span><strong class="command">response</strong></span>)
3488                   the default is <span><strong class="command">ignore</strong></span>.
3489                 </p>
3490 <p>
3491                   The rules for legal hostnames and mail domains are derived
3492                   from RFC 952 and RFC 821 as modified by RFC 1123.
3493                 </p>
3494 <p><span><strong class="command">check-names</strong></span>
3495                   applies to the owner names of A, AAAA and MX records.
3496                   It also applies to the domain names in the RDATA of NS, SOA,
3497                   MX, and SRV records.
3498                   It also applies to the RDATA of PTR records where the owner
3499                   name indicated that it is a reverse lookup of a hostname
3500                   (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, or IP6.INT).
3501                 </p>
3502 </dd>
3503 <dt><span class="term"><span><strong class="command">check-dup-records</strong></span></span></dt>
3504 <dd><p>
3505                   Check master zones for records that are treated as different
3506                   by DNSSEC but are semantically equal in plain DNS.  The
3507                   default is to <span><strong class="command">warn</strong></span>.  Other possible
3508                   values are <span><strong class="command">fail</strong></span> and
3509                   <span><strong class="command">ignore</strong></span>.
3510                 </p></dd>
3511 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
3512 <dd><p>
3513                   Check whether the MX record appears to refer to a IP address.
3514                   The default is to <span><strong class="command">warn</strong></span>.  Other possible
3515                   values are <span><strong class="command">fail</strong></span> and
3516                   <span><strong class="command">ignore</strong></span>.
3517                 </p></dd>
3518 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
3519 <dd><p>
3520                   This option is used to check for non-terminal wildcards.
3521                   The use of non-terminal wildcards is almost always as a
3522                   result of a failure
3523                   to understand the wildcard matching algorithm (RFC 1034).
3524                   This option
3525                   affects master zones.  The default (<span><strong class="command">yes</strong></span>) is to check
3526                   for non-terminal wildcards and issue a warning.
3527                 </p></dd>
3528 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
3529 <dd><p>
3530                   Perform post load zone integrity checks on master
3531                   zones.  This checks that MX and SRV records refer
3532                   to address (A or AAAA) records and that glue
3533                   address records exist for delegated zones.  For
3534                   MX and SRV records only in-zone hostnames are
3535                   checked (for out-of-zone hostnames use
3536                   <span><strong class="command">named-checkzone</strong></span>).
3537                   For NS records only names below top of zone are
3538                   checked (for out-of-zone names and glue consistency
3539                   checks use <span><strong class="command">named-checkzone</strong></span>).
3540                   The default is <span><strong class="command">yes</strong></span>.
3541                 </p></dd>
3542 <dt><span class="term"><span><strong class="command">check-mx-cname</strong></span></span></dt>
3543 <dd><p>
3544                   If <span><strong class="command">check-integrity</strong></span> is set then
3545                   fail, warn or ignore MX records that refer
3546                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
3547                 </p></dd>
3548 <dt><span class="term"><span><strong class="command">check-srv-cname</strong></span></span></dt>
3549 <dd><p>
3550                   If <span><strong class="command">check-integrity</strong></span> is set then
3551                   fail, warn or ignore SRV records that refer
3552                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
3553                 </p></dd>
3554 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
3555 <dd><p>
3556                   When performing integrity checks, also check that
3557                   sibling glue exists.  The default is <span><strong class="command">yes</strong></span>.
3558                 </p></dd>
3559 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
3560 <dd><p>
3561                   When returning authoritative negative responses to
3562                   SOA queries set the TTL of the SOA record returned in
3563                   the authority section to zero.
3564                   The default is <span><strong class="command">yes</strong></span>.
3565                 </p></dd>
3566 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl-cache</strong></span></span></dt>
3567 <dd><p>
3568                   When caching a negative response to a SOA query
3569                   set the TTL to zero.
3570                   The default is <span><strong class="command">no</strong></span>.
3571                 </p></dd>
3572 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
3573 <dd>
3574 <p>
3575                   When set to the default value of <code class="literal">yes</code>,
3576                   check the KSK bit in each key to determine how the key
3577                   should be used when generating RRSIGs for a secure zone.
3578                 </p>
3579 <p>
3580                   Ordinarily, zone-signing keys (that is, keys without the
3581                   KSK bit set) are used to sign the entire zone, while
3582                   key-signing keys (keys with the KSK bit set) are only
3583                   used to sign the DNSKEY RRset at the zone apex.
3584                   However, if this option is set to <code class="literal">no</code>,
3585                   then the KSK bit is ignored; KSKs are treated as if they
3586                   were ZSKs and are used to sign the entire zone.  This is
3587                   similar to the <span><strong class="command">dnssec-signzone -z</strong></span>
3588                   command line option.
3589                 </p>
3590 <p>
3591                   When this option is set to <code class="literal">yes</code>, there
3592                   must be at least two active keys for every algorithm
3593                   represented in the DNSKEY RRset: at least one KSK and one
3594                   ZSK per algorithm.  If there is any algorithm for which
3595                   this requirement is not met, this option will be ignored
3596                   for that algorithm.
3597                 </p>
3598 </dd>
3599 <dt><span class="term"><span><strong class="command">dnssec-dnskey-kskonly</strong></span></span></dt>
3600 <dd>
3601 <p>
3602                   When this option and <span><strong class="command">update-check-ksk</strong></span>
3603                   are both set to <code class="literal">yes</code>, only key-signing
3604                   keys (that is, keys with the KSK bit set) will be used
3605                   to sign the DNSKEY RRset at the zone apex.  Zone-signing
3606                   keys (keys without the KSK bit set) will be used to sign
3607                   the remainder of the zone, but not the DNSKEY RRset.
3608                   This is similar to the
3609                   <span><strong class="command">dnssec-signzone -x</strong></span> command line option.
3610                 </p>
3611 <p>
3612                   The default is <span><strong class="command">no</strong></span>.  If
3613                   <span><strong class="command">update-check-ksk</strong></span> is set to
3614                   <code class="literal">no</code>, this option is ignored.
3615                 </p>
3616 </dd>
3617 <dt><span class="term"><span><strong class="command">try-tcp-refresh</strong></span></span></dt>
3618 <dd><p>
3619                   Try to refresh the zone using TCP if UDP queries fail.
3620                   For BIND 8 compatibility, the default is
3621                   <span><strong class="command">yes</strong></span>.
3622                 </p></dd>
3623 <dt><span class="term"><span><strong class="command">dnssec-secure-to-insecure</strong></span></span></dt>
3624 <dd>
3625 <p>
3626                   Allow a dynamic zone to transition from secure to
3627                   insecure (i.e., signed to unsigned) by deleting all
3628                   of the DNSKEY records.  The default is <span><strong class="command">no</strong></span>.
3629                   If set to <span><strong class="command">yes</strong></span>, and if the DNSKEY RRset
3630                   at the zone apex is deleted, all RRSIG and NSEC records
3631                   will be removed from the zone as well.
3632                 </p>
3633 <p>
3634                   If the zone uses NSEC3, then it is also necessary to
3635                   delete the NSEC3PARAM RRset from the zone apex; this will
3636                   cause the removal of all corresponding NSEC3 records.
3637                   (It is expected that this requirement will be eliminated
3638                   in a future release.)
3639                 </p>
3640 <p>
3641                   Note that if a zone has been configured with
3642                   <span><strong class="command">auto-dnssec maintain</strong></span> and the
3643                   private keys remain accessible in the key repository,
3644                   then the zone will be automatically signed again the
3645                   next time <span><strong class="command">named</strong></span> is started.
3646                 </p>
3647 </dd>
3648 </dl></div>
3649 </div>
3650 <div class="sect3" lang="en">
3651 <div class="titlepage"><div><div><h4 class="title">
3652 <a name="id2583636"></a>Forwarding</h4></div></div></div>
3653 <p>
3654             The forwarding facility can be used to create a large site-wide
3655             cache on a few servers, reducing traffic over links to external
3656             name servers. It can also be used to allow queries by servers that
3657             do not have direct access to the Internet, but wish to look up
3658             exterior
3659             names anyway. Forwarding occurs only on those queries for which
3660             the server is not authoritative and does not have the answer in
3661             its cache.
3662           </p>
3663 <div class="variablelist"><dl>
3664 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
3665 <dd><p>
3666                   This option is only meaningful if the
3667                   forwarders list is not empty. A value of <code class="varname">first</code>,
3668                   the default, causes the server to query the forwarders
3669                   first &#8212; and
3670                   if that doesn't answer the question, the server will then
3671                   look for
3672                   the answer itself. If <code class="varname">only</code> is
3673                   specified, the
3674                   server will only query the forwarders.
3675                 </p></dd>
3676 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
3677 <dd><p>
3678                   Specifies the IP addresses to be used
3679                   for forwarding. The default is the empty list (no
3680                   forwarding).
3681                 </p></dd>
3682 </dl></div>
3683 <p>
3684             Forwarding can also be configured on a per-domain basis, allowing
3685             for the global forwarding options to be overridden in a variety
3686             of ways. You can set particular domains to use different
3687             forwarders,
3688             or have a different <span><strong class="command">forward only/first</strong></span> behavior,
3689             or not forward at all, see <a href="Bv9ARM.ch06.html#zone_statement_grammar" title="zone
3690             Statement Grammar">the section called &#8220;<span><strong class="command">zone</strong></span>
3691             Statement Grammar&#8221;</a>.
3692           </p>
3693 </div>
3694 <div class="sect3" lang="en">
3695 <div class="titlepage"><div><div><h4 class="title">
3696 <a name="id2583763"></a>Dual-stack Servers</h4></div></div></div>
3697 <p>
3698             Dual-stack servers are used as servers of last resort to work
3699             around
3700             problems in reachability due the lack of support for either IPv4
3701             or IPv6
3702             on the host machine.
3703           </p>
3704 <div class="variablelist"><dl>
3705 <dt><span class="term"><span><strong class="command">dual-stack-servers</strong></span></span></dt>
3706 <dd><p>
3707                   Specifies host names or addresses of machines with access to
3708                   both IPv4 and IPv6 transports. If a hostname is used, the
3709                   server must be able
3710                   to resolve the name using only the transport it has.  If the
3711                   machine is dual
3712                   stacked, then the <span><strong class="command">dual-stack-servers</strong></span> have no effect unless
3713                   access to a transport has been disabled on the command line
3714                   (e.g. <span><strong class="command">named -4</strong></span>).
3715                 </p></dd>
3716 </dl></div>
3717 </div>
3718 <div class="sect3" lang="en">
3719 <div class="titlepage"><div><div><h4 class="title">
3720 <a name="access_control"></a>Access Control</h4></div></div></div>
3721 <p>
3722             Access to the server can be restricted based on the IP address
3723             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
3724             details on how to specify IP address lists.
3725           </p>
3726 <div class="variablelist"><dl>
3727 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
3728 <dd><p>
3729                   Specifies which hosts are allowed to
3730                   notify this server, a slave, of zone changes in addition
3731                   to the zone masters.
3732                   <span><strong class="command">allow-notify</strong></span> may also be
3733                   specified in the
3734                   <span><strong class="command">zone</strong></span> statement, in which case
3735                   it overrides the
3736                   <span><strong class="command">options allow-notify</strong></span>
3737                   statement.  It is only meaningful
3738                   for a slave zone.  If not specified, the default is to
3739                   process notify messages
3740                   only from a zone's master.
3741                 </p></dd>
3742 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
3743 <dd>
3744 <p>
3745                   Specifies which hosts are allowed to ask ordinary
3746                   DNS questions. <span><strong class="command">allow-query</strong></span> may
3747                   also be specified in the <span><strong class="command">zone</strong></span>
3748                   statement, in which case it overrides the
3749                   <span><strong class="command">options allow-query</strong></span> statement.
3750                   If not specified, the default is to allow queries
3751                   from all hosts.
3752                 </p>
3753 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3754 <h3 class="title">Note</h3>
3755 <p>
3756                     <span><strong class="command">allow-query-cache</strong></span> is now
3757                     used to specify access to the cache.
3758                   </p>
3759 </div>
3760 </dd>
3761 <dt><span class="term"><span><strong class="command">allow-query-on</strong></span></span></dt>
3762 <dd>
3763 <p>
3764                   Specifies which local addresses can accept ordinary
3765                   DNS questions. This makes it possible, for instance,
3766                   to allow queries on internal-facing interfaces but
3767                   disallow them on external-facing ones, without
3768                   necessarily knowing the internal network's addresses.
3769                 </p>
3770 <p>
3771                   <span><strong class="command">allow-query-on</strong></span> may
3772                   also be specified in the <span><strong class="command">zone</strong></span>
3773                   statement, in which case it overrides the
3774                   <span><strong class="command">options allow-query-on</strong></span> statement.
3775                 </p>
3776 <p>
3777                   If not specified, the default is to allow queries
3778                   on all addresses.
3779                 </p>
3780 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3781 <h3 class="title">Note</h3>
3782 <p>
3783                     <span><strong class="command">allow-query-cache</strong></span> is
3784                     used to specify access to the cache.
3785                   </p>
3786 </div>
3787 </dd>
3788 <dt><span class="term"><span><strong class="command">allow-query-cache</strong></span></span></dt>
3789 <dd><p>
3790                   Specifies which hosts are allowed to get answers
3791                   from the cache.  If <span><strong class="command">allow-query-cache</strong></span>
3792                   is not set then <span><strong class="command">allow-recursion</strong></span>
3793                   is used if set, otherwise <span><strong class="command">allow-query</strong></span>
3794                   is used if set unless <span><strong class="command">recursion no;</strong></span> is
3795                   set in which case <span><strong class="command">none;</strong></span> is used,
3796                   otherwise the default (<span><strong class="command">localnets;</strong></span>
3797                   <span><strong class="command">localhost;</strong></span>) is used.
3798                 </p></dd>
3799 <dt><span class="term"><span><strong class="command">allow-query-cache-on</strong></span></span></dt>
3800 <dd><p>
3801                   Specifies which local addresses can give answers
3802                   from the cache.  If not specified, the default is
3803                   to allow cache queries on any address,
3804                   <span><strong class="command">localnets</strong></span> and
3805                   <span><strong class="command">localhost</strong></span>.
3806                 </p></dd>
3807 <dt><span class="term"><span><strong class="command">allow-recursion</strong></span></span></dt>
3808 <dd><p>
3809                   Specifies which hosts are allowed to make recursive
3810                   queries through this server. If
3811                   <span><strong class="command">allow-recursion</strong></span> is not set
3812                   then <span><strong class="command">allow-query-cache</strong></span> is
3813                   used if set, otherwise <span><strong class="command">allow-query</strong></span>
3814                   is used if set, otherwise the default
3815                   (<span><strong class="command">localnets;</strong></span>
3816                   <span><strong class="command">localhost;</strong></span>) is used.
3817                 </p></dd>
3818 <dt><span class="term"><span><strong class="command">allow-recursion-on</strong></span></span></dt>
3819 <dd><p>
3820                   Specifies which local addresses can accept recursive
3821                   queries.  If not specified, the default is to allow
3822                   recursive queries on all addresses.
3823                 </p></dd>
3824 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
3825 <dd><p>
3826                   Specifies which hosts are allowed to
3827                   submit Dynamic DNS updates for master zones. The default is
3828                   to deny
3829                   updates from all hosts.  Note that allowing updates based
3830                   on the requestor's IP address is insecure; see
3831                   <a href="Bv9ARM.ch07.html#dynamic_update_security" title="Dynamic Update Security">the section called &#8220;Dynamic Update Security&#8221;</a> for details.
3832                 </p></dd>
3833 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
3834 <dd>
3835 <p>
3836                   Specifies which hosts are allowed to
3837                   submit Dynamic DNS updates to slave zones to be forwarded to
3838                   the
3839                   master.  The default is <strong class="userinput"><code>{ none; }</code></strong>,
3840                   which
3841                   means that no update forwarding will be performed.  To
3842                   enable
3843                   update forwarding, specify
3844                   <strong class="userinput"><code>allow-update-forwarding { any; };</code></strong>.
3845                   Specifying values other than <strong class="userinput"><code>{ none; }</code></strong> or
3846                   <strong class="userinput"><code>{ any; }</code></strong> is usually
3847                   counterproductive, since
3848                   the responsibility for update access control should rest
3849                   with the
3850                   master server, not the slaves.
3851                 </p>
3852 <p>
3853                   Note that enabling the update forwarding feature on a slave
3854                   server
3855                   may expose master servers relying on insecure IP address
3856                   based
3857                   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>
3858                   for more details.
3859                 </p>
3860 </dd>
3861 <dt><span class="term"><span><strong class="command">allow-v6-synthesis</strong></span></span></dt>
3862 <dd><p>
3863                   This option was introduced for the smooth transition from
3864                   AAAA
3865                   to A6 and from "nibble labels" to binary labels.
3866                   However, since both A6 and binary labels were then
3867                   deprecated,
3868                   this option was also deprecated.
3869                   It is now ignored with some warning messages.
3870                 </p></dd>
3871 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
3872 <dd><p>
3873                   Specifies which hosts are allowed to
3874                   receive zone transfers from the server. <span><strong class="command">allow-transfer</strong></span> may
3875                   also be specified in the <span><strong class="command">zone</strong></span>
3876                   statement, in which
3877                   case it overrides the <span><strong class="command">options allow-transfer</strong></span> statement.
3878                   If not specified, the default is to allow transfers to all
3879                   hosts.
3880                 </p></dd>
3881 <dt><span class="term"><span><strong class="command">blackhole</strong></span></span></dt>
3882 <dd><p>
3883                   Specifies a list of addresses that the
3884                   server will not accept queries from or use to resolve a
3885                   query. Queries
3886                   from these addresses will not be responded to. The default
3887                   is <strong class="userinput"><code>none</code></strong>.
3888                 </p></dd>
3889 <dt><span class="term"><span><strong class="command">filter-aaaa</strong></span></span></dt>
3890 <dd><p>
3891                   Specifies a list of addresses to which
3892                   <span><strong class="command">filter-aaaa-on-v4</strong></span>
3893                   is applies.  The default is <strong class="userinput"><code>any</code></strong>.
3894                 </p></dd>
3895 <dt><span class="term"><span><strong class="command">resolver-query-timeout</strong></span></span></dt>
3896 <dd><p>
3897                   The amount of time the resolver will spend attempting
3898                   to resolve a recursive query before failing.  The
3899                   default is <code class="literal">10</code> and the maximum is
3900                   <code class="literal">30</code>.  Setting it to <code class="literal">0</code>
3901                   will result in the default being used.
3902                 </p></dd>
3903 </dl></div>
3904 </div>
3905 <div class="sect3" lang="en">
3906 <div class="titlepage"><div><div><h4 class="title">
3907 <a name="id2584382"></a>Interfaces</h4></div></div></div>
3908 <p>
3909             The interfaces and ports that the server will answer queries
3910             from may be specified using the <span><strong class="command">listen-on</strong></span> option. <span><strong class="command">listen-on</strong></span> takes
3911             an optional port and an <code class="varname">address_match_list</code>.
3912             The server will listen on all interfaces allowed by the address
3913             match list. If a port is not specified, port 53 will be used.
3914           </p>
3915 <p>
3916             Multiple <span><strong class="command">listen-on</strong></span> statements are
3917             allowed.
3918             For example,
3919           </p>
3920 <pre class="programlisting">listen-on { 5.6.7.8; };
3921 listen-on port 1234 { !1.2.3.4; 1.2/16; };
3922 </pre>
3923 <p>
3924             will enable the name server on port 53 for the IP address
3925             5.6.7.8, and on port 1234 of an address on the machine in net
3926             1.2 that is not 1.2.3.4.
3927           </p>
3928 <p>
3929             If no <span><strong class="command">listen-on</strong></span> is specified, the
3930             server will listen on port 53 on all IPv4 interfaces.
3931           </p>
3932 <p>
3933             The <span><strong class="command">listen-on-v6</strong></span> option is used to
3934             specify the interfaces and the ports on which the server will
3935             listen
3936             for incoming queries sent using IPv6.
3937           </p>
3938 <p>
3939             When </p>
3940 <pre class="programlisting">{ any; }</pre>
3941 <p> is
3942             specified
3943             as the <code class="varname">address_match_list</code> for the
3944             <span><strong class="command">listen-on-v6</strong></span> option,
3945             the server does not bind a separate socket to each IPv6 interface
3946             address as it does for IPv4 if the operating system has enough API
3947             support for IPv6 (specifically if it conforms to RFC 3493 and RFC
3948             3542).
3949             Instead, it listens on the IPv6 wildcard address.
3950             If the system only has incomplete API support for IPv6, however,
3951             the behavior is the same as that for IPv4.
3952           </p>
3953 <p>
3954             A list of particular IPv6 addresses can also be specified, in
3955             which case
3956             the server listens on a separate socket for each specified
3957             address,
3958             regardless of whether the desired API is supported by the system.
3959           </p>
3960 <p>
3961             Multiple <span><strong class="command">listen-on-v6</strong></span> options can
3962             be used.
3963             For example,
3964           </p>
3965 <pre class="programlisting">listen-on-v6 { any; };
3966 listen-on-v6 port 1234 { !2001:db8::/32; any; };
3967 </pre>
3968 <p>
3969             will enable the name server on port 53 for any IPv6 addresses
3970             (with a single wildcard socket),
3971             and on port 1234 of IPv6 addresses that is not in the prefix
3972             2001:db8::/32 (with separate sockets for each matched address.)
3973           </p>
3974 <p>
3975             To make the server not listen on any IPv6 address, use
3976           </p>
3977 <pre class="programlisting">listen-on-v6 { none; };
3978 </pre>
3979 <p>
3980             If no <span><strong class="command">listen-on-v6</strong></span> option is
3981             specified, the server will not listen on any IPv6 address
3982             unless <span><strong class="command">-6</strong></span> is specified when <span><strong class="command">named</strong></span> is
3983             invoked.  If <span><strong class="command">-6</strong></span> is specified then
3984             <span><strong class="command">named</strong></span> will listen on port 53 on all IPv6 interfaces by default.
3985           </p>
3986 </div>
3987 <div class="sect3" lang="en">
3988 <div class="titlepage"><div><div><h4 class="title">
3989 <a name="query_address"></a>Query Address</h4></div></div></div>
3990 <p>
3991             If the server doesn't know the answer to a question, it will
3992             query other name servers. <span><strong class="command">query-source</strong></span> specifies
3993             the address and port used for such queries. For queries sent over
3994             IPv6, there is a separate <span><strong class="command">query-source-v6</strong></span> option.
3995             If <span><strong class="command">address</strong></span> is <span><strong class="command">*</strong></span> (asterisk) or is omitted,
3996             a wildcard IP address (<span><strong class="command">INADDR_ANY</strong></span>)
3997             will be used.
3998           </p>
3999 <p>
4000             If <span><strong class="command">port</strong></span> is <span><strong class="command">*</strong></span> or is omitted,
4001             a random port number from a pre-configured
4002             range is picked up and will be used for each query.
4003             The port range(s) is that specified in
4004             the <span><strong class="command">use-v4-udp-ports</strong></span> (for IPv4)
4005             and <span><strong class="command">use-v6-udp-ports</strong></span> (for IPv6)
4006             options, excluding the ranges specified in
4007             the <span><strong class="command">avoid-v4-udp-ports</strong></span>
4008             and <span><strong class="command">avoid-v6-udp-ports</strong></span> options, respectively.
4009           </p>
4010 <p>
4011             The defaults of the <span><strong class="command">query-source</strong></span> and
4012             <span><strong class="command">query-source-v6</strong></span> options
4013             are:
4014           </p>
4015 <pre class="programlisting">query-source address * port *;
4016 query-source-v6 address * port *;
4017 </pre>
4018 <p>
4019             If <span><strong class="command">use-v4-udp-ports</strong></span> or
4020             <span><strong class="command">use-v6-udp-ports</strong></span> is unspecified,
4021             <span><strong class="command">named</strong></span> will check if the operating
4022             system provides a programming interface to retrieve the
4023             system's default range for ephemeral ports.
4024             If such an interface is available,
4025             <span><strong class="command">named</strong></span> will use the corresponding system
4026             default range; otherwise, it will use its own defaults:
4027          </p>
4028 <pre class="programlisting">use-v4-udp-ports { range 1024 65535; };
4029 use-v6-udp-ports { range 1024 65535; };
4030 </pre>
4031 <p>
4032             Note: make sure the ranges be sufficiently large for
4033             security.  A desirable size depends on various parameters,
4034             but we generally recommend it contain at least 16384 ports
4035             (14 bits of entropy).
4036             Note also that the system's default range when used may be
4037             too small for this purpose, and that the range may even be
4038             changed while <span><strong class="command">named</strong></span> is running; the new
4039             range will automatically be applied when <span><strong class="command">named</strong></span>
4040             is reloaded.
4041             It is encouraged to
4042             configure <span><strong class="command">use-v4-udp-ports</strong></span> and
4043             <span><strong class="command">use-v6-udp-ports</strong></span> explicitly so that the
4044             ranges are sufficiently large and are reasonably
4045             independent from the ranges used by other applications.
4046           </p>
4047 <p>
4048             Note: the operational configuration
4049             where <span><strong class="command">named</strong></span> runs may prohibit the use
4050             of some ports.  For example, UNIX systems will not allow
4051             <span><strong class="command">named</strong></span> running without a root privilege
4052             to use ports less than 1024.
4053             If such ports are included in the specified (or detected)
4054             set of query ports, the corresponding query attempts will
4055             fail, resulting in resolution failures or delay.
4056             It is therefore important to configure the set of ports
4057             that can be safely used in the expected operational environment.
4058           </p>
4059 <p>
4060             The defaults of the <span><strong class="command">avoid-v4-udp-ports</strong></span> and
4061             <span><strong class="command">avoid-v6-udp-ports</strong></span> options
4062             are:
4063           </p>
4064 <pre class="programlisting">avoid-v4-udp-ports {};
4065 avoid-v6-udp-ports {};
4066 </pre>
4067 <p>
4068             Note: BIND 9.5.0 introduced
4069             the <span><strong class="command">use-queryport-pool</strong></span>
4070             option to support a pool of such random ports, but this
4071             option is now obsolete because reusing the same ports in
4072             the pool may not be sufficiently secure.
4073             For the same reason, it is generally strongly discouraged to
4074             specify a particular port for the
4075             <span><strong class="command">query-source</strong></span> or
4076             <span><strong class="command">query-source-v6</strong></span> options;
4077             it implicitly disables the use of randomized port numbers.
4078           </p>
4079 <div class="variablelist"><dl>
4080 <dt><span class="term"><span><strong class="command">use-queryport-pool</strong></span></span></dt>
4081 <dd><p>
4082                   This option is obsolete.
4083                 </p></dd>
4084 <dt><span class="term"><span><strong class="command">queryport-pool-ports</strong></span></span></dt>
4085 <dd><p>
4086                   This option is obsolete.
4087                 </p></dd>
4088 <dt><span class="term"><span><strong class="command">queryport-pool-updateinterval</strong></span></span></dt>
4089 <dd><p>
4090                   This option is obsolete.
4091                 </p></dd>
4092 </dl></div>
4093 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4094 <h3 class="title">Note</h3>
4095 <p>
4096               The address specified in the <span><strong class="command">query-source</strong></span> option
4097               is used for both UDP and TCP queries, but the port applies only
4098               to UDP queries.  TCP queries always use a random
4099               unprivileged port.
4100             </p>
4101 </div>
4102 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4103 <h3 class="title">Note</h3>
4104 <p>
4105               Solaris 2.5.1 and earlier does not support setting the source
4106               address for TCP sockets.
4107             </p>
4108 </div>
4109 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4110 <h3 class="title">Note</h3>
4111 <p>
4112               See also <span><strong class="command">transfer-source</strong></span> and
4113               <span><strong class="command">notify-source</strong></span>.
4114             </p>
4115 </div>
4116 </div>
4117 <div class="sect3" lang="en">
4118 <div class="titlepage"><div><div><h4 class="title">
4119 <a name="zone_transfers"></a>Zone Transfers</h4></div></div></div>
4120 <p>
4121             <acronym class="acronym">BIND</acronym> has mechanisms in place to
4122             facilitate zone transfers
4123             and set limits on the amount of load that transfers place on the
4124             system. The following options apply to zone transfers.
4125           </p>
4126 <div class="variablelist"><dl>
4127 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
4128 <dd><p>
4129                   Defines a global list of IP addresses of name servers
4130                   that are also sent NOTIFY messages whenever a fresh copy of
4131                   the
4132                   zone is loaded, in addition to the servers listed in the
4133                   zone's NS records.
4134                   This helps to ensure that copies of the zones will
4135                   quickly converge on stealth servers.
4136                   Optionally, a port may be specified with each
4137                   <span><strong class="command">also-notify</strong></span> address to send
4138                   the notify messages to a port other than the
4139                   default of 53.
4140                   If an <span><strong class="command">also-notify</strong></span> list
4141                   is given in a <span><strong class="command">zone</strong></span> statement,
4142                   it will override
4143                   the <span><strong class="command">options also-notify</strong></span>
4144                   statement. When a <span><strong class="command">zone notify</strong></span>
4145                   statement
4146                   is set to <span><strong class="command">no</strong></span>, the IP
4147                   addresses in the global <span><strong class="command">also-notify</strong></span> list will
4148                   not be sent NOTIFY messages for that zone. The default is
4149                   the empty
4150                   list (no global notification list).
4151                 </p></dd>
4152 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
4153 <dd><p>
4154                   Inbound zone transfers running longer than
4155                   this many minutes will be terminated. The default is 120
4156                   minutes
4157                   (2 hours).  The maximum value is 28 days (40320 minutes).
4158                 </p></dd>
4159 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
4160 <dd><p>
4161                   Inbound zone transfers making no progress
4162                   in this many minutes will be terminated. The default is 60
4163                   minutes
4164                   (1 hour).  The maximum value is 28 days (40320 minutes).
4165                 </p></dd>
4166 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
4167 <dd><p>
4168                   Outbound zone transfers running longer than
4169                   this many minutes will be terminated. The default is 120
4170                   minutes
4171                   (2 hours).  The maximum value is 28 days (40320 minutes).
4172                 </p></dd>
4173 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
4174 <dd><p>
4175                   Outbound zone transfers making no progress
4176                   in this many minutes will be terminated.  The default is 60
4177                   minutes (1
4178                   hour).  The maximum value is 28 days (40320 minutes).
4179                 </p></dd>
4180 <dt><span class="term"><span><strong class="command">serial-query-rate</strong></span></span></dt>
4181 <dd>
4182 <p>
4183                   Slave servers will periodically query master
4184                   servers to find out if zone serial numbers have
4185                   changed. Each such query uses a minute amount of
4186                   the slave server's network bandwidth.  To limit
4187                   the amount of bandwidth used, BIND 9 limits the
4188                   rate at which queries are sent.  The value of the
4189                   <span><strong class="command">serial-query-rate</strong></span> option, an
4190                   integer, is the maximum number of queries sent
4191                   per second.  The default is 20.
4192                 </p>
4193 <p>
4194                   In addition to controlling the rate SOA refresh
4195                   queries are issued at
4196                   <span><strong class="command">serial-query-rate</strong></span> also controls
4197                   the rate at which NOTIFY messages are sent from
4198                   both master and slave zones.
4199                 </p>
4200 </dd>
4201 <dt><span class="term"><span><strong class="command">serial-queries</strong></span></span></dt>
4202 <dd><p>
4203                   In BIND 8, the <span><strong class="command">serial-queries</strong></span>
4204                   option
4205                   set the maximum number of concurrent serial number queries
4206                   allowed to be outstanding at any given time.
4207                   BIND 9 does not limit the number of outstanding
4208                   serial queries and ignores the <span><strong class="command">serial-queries</strong></span> option.
4209                   Instead, it limits the rate at which the queries are sent
4210                   as defined using the <span><strong class="command">serial-query-rate</strong></span> option.
4211                 </p></dd>
4212 <dt><span class="term"><span><strong class="command">transfer-format</strong></span></span></dt>
4213 <dd><p>
4214                   Zone transfers can be sent using two different formats,
4215                   <span><strong class="command">one-answer</strong></span> and
4216                   <span><strong class="command">many-answers</strong></span>.
4217                   The <span><strong class="command">transfer-format</strong></span> option is used
4218                   on the master server to determine which format it sends.
4219                   <span><strong class="command">one-answer</strong></span> uses one DNS message per
4220                   resource record transferred.
4221                   <span><strong class="command">many-answers</strong></span> packs as many resource
4222                   records as possible into a message.
4223                   <span><strong class="command">many-answers</strong></span> is more efficient, but is
4224                   only supported by relatively new slave servers,
4225                   such as <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
4226                   8.x and <acronym class="acronym">BIND</acronym> 4.9.5 onwards.
4227                   The <span><strong class="command">many-answers</strong></span> format is also supported by
4228                   recent Microsoft Windows nameservers.
4229                   The default is <span><strong class="command">many-answers</strong></span>.
4230                   <span><strong class="command">transfer-format</strong></span> may be overridden on a
4231                   per-server basis by using the <span><strong class="command">server</strong></span>
4232                   statement.
4233                 </p></dd>
4234 <dt><span class="term"><span><strong class="command">transfers-in</strong></span></span></dt>
4235 <dd><p>
4236                   The maximum number of inbound zone transfers
4237                   that can be running concurrently. The default value is <code class="literal">10</code>.
4238                   Increasing <span><strong class="command">transfers-in</strong></span> may
4239                   speed up the convergence
4240                   of slave zones, but it also may increase the load on the
4241                   local system.
4242                 </p></dd>
4243 <dt><span class="term"><span><strong class="command">transfers-out</strong></span></span></dt>
4244 <dd><p>
4245                   The maximum number of outbound zone transfers
4246                   that can be running concurrently. Zone transfer requests in
4247                   excess
4248                   of the limit will be refused. The default value is <code class="literal">10</code>.
4249                 </p></dd>
4250 <dt><span class="term"><span><strong class="command">transfers-per-ns</strong></span></span></dt>
4251 <dd><p>
4252                   The maximum number of inbound zone transfers
4253                   that can be concurrently transferring from a given remote
4254                   name server.
4255                   The default value is <code class="literal">2</code>.
4256                   Increasing <span><strong class="command">transfers-per-ns</strong></span>
4257                   may
4258                   speed up the convergence of slave zones, but it also may
4259                   increase
4260                   the load on the remote name server. <span><strong class="command">transfers-per-ns</strong></span> may
4261                   be overridden on a per-server basis by using the <span><strong class="command">transfers</strong></span> phrase
4262                   of the <span><strong class="command">server</strong></span> statement.
4263                 </p></dd>
4264 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
4265 <dd>
4266 <p><span><strong class="command">transfer-source</strong></span>
4267                   determines which local address will be bound to IPv4
4268                   TCP connections used to fetch zones transferred
4269                   inbound by the server.  It also determines the
4270                   source IPv4 address, and optionally the UDP port,
4271                   used for the refresh queries and forwarded dynamic
4272                   updates.  If not set, it defaults to a system
4273                   controlled value which will usually be the address
4274                   of the interface "closest to" the remote end. This
4275                   address must appear in the remote end's
4276                   <span><strong class="command">allow-transfer</strong></span> option for the
4277                   zone being transferred, if one is specified. This
4278                   statement sets the
4279                   <span><strong class="command">transfer-source</strong></span> for all zones,
4280                   but can be overridden on a per-view or per-zone
4281                   basis by including a
4282                   <span><strong class="command">transfer-source</strong></span> statement within
4283                   the <span><strong class="command">view</strong></span> or
4284                   <span><strong class="command">zone</strong></span> block in the configuration
4285                   file.
4286                 </p>
4287 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4288 <h3 class="title">Note</h3>
4289 <p>
4290                     Solaris 2.5.1 and earlier does not support setting the
4291                     source address for TCP sockets.
4292                   </p>
4293 </div>
4294 </dd>
4295 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
4296 <dd><p>
4297                   The same as <span><strong class="command">transfer-source</strong></span>,
4298                   except zone transfers are performed using IPv6.
4299                 </p></dd>
4300 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
4301 <dd>
4302 <p>
4303                   An alternate transfer source if the one listed in
4304                   <span><strong class="command">transfer-source</strong></span> fails and
4305                   <span><strong class="command">use-alt-transfer-source</strong></span> is
4306                   set.
4307                 </p>
4308 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4309 <h3 class="title">Note</h3>
4310                   If you do not wish the alternate transfer source
4311                   to be used, you should set
4312                   <span><strong class="command">use-alt-transfer-source</strong></span>
4313                   appropriately and you should not depend upon
4314                   getting an answer back to the first refresh
4315                   query.
4316                 </div>
4317 </dd>
4318 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
4319 <dd><p>
4320                   An alternate transfer source if the one listed in
4321                   <span><strong class="command">transfer-source-v6</strong></span> fails and
4322                   <span><strong class="command">use-alt-transfer-source</strong></span> is
4323                   set.
4324                 </p></dd>
4325 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
4326 <dd><p>
4327                   Use the alternate transfer sources or not.  If views are
4328                   specified this defaults to <span><strong class="command">no</strong></span>
4329                   otherwise it defaults to
4330                   <span><strong class="command">yes</strong></span> (for BIND 8
4331                   compatibility).
4332                 </p></dd>
4333 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
4334 <dd>
4335 <p><span><strong class="command">notify-source</strong></span>
4336                   determines which local source address, and
4337                   optionally UDP port, will be used to send NOTIFY
4338                   messages.  This address must appear in the slave
4339                   server's <span><strong class="command">masters</strong></span> zone clause or
4340                   in an <span><strong class="command">allow-notify</strong></span> clause.  This
4341                   statement sets the <span><strong class="command">notify-source</strong></span>
4342                   for all zones, but can be overridden on a per-zone or
4343                   per-view basis by including a
4344                   <span><strong class="command">notify-source</strong></span> statement within
4345                   the <span><strong class="command">zone</strong></span> or
4346                   <span><strong class="command">view</strong></span> block in the configuration
4347                   file.
4348                 </p>
4349 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4350 <h3 class="title">Note</h3>
4351 <p>
4352                     Solaris 2.5.1 and earlier does not support setting the
4353                     source address for TCP sockets.
4354                   </p>
4355 </div>
4356 </dd>
4357 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
4358 <dd><p>
4359                   Like <span><strong class="command">notify-source</strong></span>,
4360                   but applies to notify messages sent to IPv6 addresses.
4361                 </p></dd>
4362 </dl></div>
4363 </div>
4364 <div class="sect3" lang="en">
4365 <div class="titlepage"><div><div><h4 class="title">
4366 <a name="id2585456"></a>UDP Port Lists</h4></div></div></div>
4367 <p>
4368             <span><strong class="command">use-v4-udp-ports</strong></span>,
4369             <span><strong class="command">avoid-v4-udp-ports</strong></span>,
4370             <span><strong class="command">use-v6-udp-ports</strong></span>, and
4371             <span><strong class="command">avoid-v6-udp-ports</strong></span>
4372             specify a list of IPv4 and IPv6 UDP ports that will be
4373             used or not used as source ports for UDP messages.
4374             See <a href="Bv9ARM.ch06.html#query_address" title="Query Address">the section called &#8220;Query Address&#8221;</a> about how the
4375             available ports are determined.
4376             For example, with the following configuration
4377           </p>
4378 <pre class="programlisting">
4379 use-v6-udp-ports { range 32768 65535; };
4380 avoid-v6-udp-ports { 40000; range 50000 60000; };
4381 </pre>
4382 <p>
4383              UDP ports of IPv6 messages sent
4384              from <span><strong class="command">named</strong></span> will be in one
4385              of the following ranges: 32768 to 39999, 40001 to 49999,
4386              and 60001 to 65535.
4387            </p>
4388 <p>
4389              <span><strong class="command">avoid-v4-udp-ports</strong></span> and
4390              <span><strong class="command">avoid-v6-udp-ports</strong></span> can be used
4391              to prevent <span><strong class="command">named</strong></span> from choosing as its random source port a
4392              port that is blocked by your firewall or a port that is
4393              used by other applications;
4394              if a query went out with a source port blocked by a
4395              firewall, the
4396              answer would not get by the firewall and the name server would
4397              have to query again.
4398              Note: the desired range can also be represented only with
4399              <span><strong class="command">use-v4-udp-ports</strong></span> and
4400              <span><strong class="command">use-v6-udp-ports</strong></span>, and the
4401              <span><strong class="command">avoid-</strong></span> options are redundant in that
4402              sense; they are provided for backward compatibility and
4403              to possibly simplify the port specification.
4404            </p>
4405 </div>
4406 <div class="sect3" lang="en">
4407 <div class="titlepage"><div><div><h4 class="title">
4408 <a name="id2585584"></a>Operating System Resource Limits</h4></div></div></div>
4409 <p>
4410             The server's usage of many system resources can be limited.
4411             Scaled values are allowed when specifying resource limits.  For
4412             example, <span><strong class="command">1G</strong></span> can be used instead of
4413             <span><strong class="command">1073741824</strong></span> to specify a limit of
4414             one
4415             gigabyte. <span><strong class="command">unlimited</strong></span> requests
4416             unlimited use, or the
4417             maximum available amount. <span><strong class="command">default</strong></span>
4418             uses the limit
4419             that was in force when the server was started. See the description
4420             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>.
4421           </p>
4422 <p>
4423             The following options set operating system resource limits for
4424             the name server process.  Some operating systems don't support
4425             some or
4426             any of the limits. On such systems, a warning will be issued if
4427             the
4428             unsupported limit is used.
4429           </p>
4430 <div class="variablelist"><dl>
4431 <dt><span class="term"><span><strong class="command">coresize</strong></span></span></dt>
4432 <dd><p>
4433                   The maximum size of a core dump. The default
4434                   is <code class="literal">default</code>.
4435                 </p></dd>
4436 <dt><span class="term"><span><strong class="command">datasize</strong></span></span></dt>
4437 <dd><p>
4438                   The maximum amount of data memory the server
4439                   may use. The default is <code class="literal">default</code>.
4440                   This is a hard limit on server memory usage.
4441                   If the server attempts to allocate memory in excess of this
4442                   limit, the allocation will fail, which may in turn leave
4443                   the server unable to perform DNS service.  Therefore,
4444                   this option is rarely useful as a way of limiting the
4445                   amount of memory used by the server, but it can be used
4446                   to raise an operating system data size limit that is
4447                   too small by default.  If you wish to limit the amount
4448                   of memory used by the server, use the
4449                   <span><strong class="command">max-cache-size</strong></span> and
4450                   <span><strong class="command">recursive-clients</strong></span>
4451                   options instead.
4452                 </p></dd>
4453 <dt><span class="term"><span><strong class="command">files</strong></span></span></dt>
4454 <dd><p>
4455                   The maximum number of files the server
4456                   may have open concurrently. The default is <code class="literal">unlimited</code>.
4457                 </p></dd>
4458 <dt><span class="term"><span><strong class="command">stacksize</strong></span></span></dt>
4459 <dd><p>
4460                   The maximum amount of stack memory the server
4461                   may use. The default is <code class="literal">default</code>.
4462                 </p></dd>
4463 </dl></div>
4464 </div>
4465 <div class="sect3" lang="en">
4466 <div class="titlepage"><div><div><h4 class="title">
4467 <a name="server_resource_limits"></a>Server  Resource Limits</h4></div></div></div>
4468 <p>
4469             The following options set limits on the server's
4470             resource consumption that are enforced internally by the
4471             server rather than the operating system.
4472           </p>
4473 <div class="variablelist"><dl>
4474 <dt><span class="term"><span><strong class="command">max-ixfr-log-size</strong></span></span></dt>
4475 <dd><p>
4476                   This option is obsolete; it is accepted
4477                   and ignored for BIND 8 compatibility.  The option
4478                   <span><strong class="command">max-journal-size</strong></span> performs a
4479                   similar function in BIND 9.
4480                 </p></dd>
4481 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
4482 <dd><p>
4483                   Sets a maximum size for each journal file
4484                   (see <a href="Bv9ARM.ch04.html#journal" title="The journal file">the section called &#8220;The journal file&#8221;</a>).  When the journal file
4485                   approaches
4486                   the specified size, some of the oldest transactions in the
4487                   journal
4488                   will be automatically removed.  The default is
4489                   <code class="literal">unlimited</code>.
4490                   This may also be set on a per-zone basis.
4491                 </p></dd>
4492 <dt><span class="term"><span><strong class="command">host-statistics-max</strong></span></span></dt>
4493 <dd><p>
4494                   In BIND 8, specifies the maximum number of host statistics
4495                   entries to be kept.
4496                   Not implemented in BIND 9.
4497                 </p></dd>
4498 <dt><span class="term"><span><strong class="command">recursive-clients</strong></span></span></dt>
4499 <dd><p>
4500                   The maximum number of simultaneous recursive lookups
4501                   the server will perform on behalf of clients.  The default
4502                   is
4503                   <code class="literal">1000</code>.  Because each recursing
4504                   client uses a fair
4505                   bit of memory, on the order of 20 kilobytes, the value of
4506                   the
4507                   <span><strong class="command">recursive-clients</strong></span> option may
4508                   have to be decreased
4509                   on hosts with limited memory.
4510                 </p></dd>
4511 <dt><span class="term"><span><strong class="command">tcp-clients</strong></span></span></dt>
4512 <dd><p>
4513                   The maximum number of simultaneous client TCP
4514                   connections that the server will accept.
4515                   The default is <code class="literal">100</code>.
4516                 </p></dd>
4517 <dt><span class="term"><span><strong class="command">reserved-sockets</strong></span></span></dt>
4518 <dd>
4519 <p>
4520                   The number of file descriptors reserved for TCP, stdio,
4521                   etc.  This needs to be big enough to cover the number of
4522                   interfaces <span><strong class="command">named</strong></span> listens on, <span><strong class="command">tcp-clients</strong></span> as well as
4523                   to provide room for outgoing TCP queries and incoming zone
4524                   transfers.  The default is <code class="literal">512</code>.
4525                   The minimum value is <code class="literal">128</code> and the
4526                   maximum value is <code class="literal">128</code> less than
4527                   maxsockets (-S).  This option may be removed in the future.
4528                 </p>
4529 <p>
4530                   This option has little effect on Windows.
4531                 </p>
4532 </dd>
4533 <dt><span class="term"><span><strong class="command">max-cache-size</strong></span></span></dt>
4534 <dd><p>
4535                   The maximum amount of memory to use for the
4536                   server's cache, in bytes.
4537                   When the amount of data in the cache
4538                   reaches this limit, the server will cause records to expire
4539                   prematurely based on an LRU based strategy so that
4540                   the limit is not exceeded.
4541                   A value of 0 is special, meaning that
4542                   records are purged from the cache only when their
4543                   TTLs expire.
4544                   Another special keyword <strong class="userinput"><code>unlimited</code></strong>
4545                   means the maximum value of 32-bit unsigned integers
4546                   (0xffffffff), which may not have the same effect as
4547                   0 on machines that support more than 32 bits of
4548                   memory space.
4549                   Any positive values less than 2MB will be ignored reset
4550                   to 2MB.
4551                   In a server with multiple views, the limit applies
4552                   separately to the cache of each view.
4553                   The default is 0.
4554                 </p></dd>
4555 <dt><span class="term"><span><strong class="command">tcp-listen-queue</strong></span></span></dt>
4556 <dd><p>
4557                   The listen queue depth.  The default and minimum is 3.
4558                   If the kernel supports the accept filter "dataready" this
4559                   also controls how
4560                   many TCP connections that will be queued in kernel space
4561                   waiting for
4562                   some data before being passed to accept.  Values less than 3
4563                   will be
4564                   silently raised.
4565                 </p></dd>
4566 </dl></div>
4567 </div>
4568 <div class="sect3" lang="en">
4569 <div class="titlepage"><div><div><h4 class="title">
4570 <a name="id2585869"></a>Periodic Task Intervals</h4></div></div></div>
4571 <div class="variablelist"><dl>
4572 <dt><span class="term"><span><strong class="command">cleaning-interval</strong></span></span></dt>
4573 <dd><p>
4574                   This interval is effectively obsolete.  Previously,
4575                   the server would remove expired resource records
4576                   from the cache every <span><strong class="command">cleaning-interval</strong></span> minutes.
4577                   <acronym class="acronym">BIND</acronym> 9 now manages cache
4578                   memory in a more sophisticated manner and does not
4579                   rely on the periodic cleaning any more.
4580                   Specifying this option therefore has no effect on
4581                   the server's behavior.
4582                 </p></dd>
4583 <dt><span class="term"><span><strong class="command">heartbeat-interval</strong></span></span></dt>
4584 <dd><p>
4585                   The server will perform zone maintenance tasks
4586                   for all zones marked as <span><strong class="command">dialup</strong></span> whenever this
4587                   interval expires. The default is 60 minutes. Reasonable
4588                   values are up
4589                   to 1 day (1440 minutes).  The maximum value is 28 days
4590                   (40320 minutes).
4591                   If set to 0, no zone maintenance for these zones will occur.
4592                 </p></dd>
4593 <dt><span class="term"><span><strong class="command">interface-interval</strong></span></span></dt>
4594 <dd><p>
4595                   The server will scan the network interface list
4596                   every <span><strong class="command">interface-interval</strong></span>
4597                   minutes. The default
4598                   is 60 minutes. The maximum value is 28 days (40320 minutes).
4599                   If set to 0, interface scanning will only occur when
4600                   the configuration file is  loaded. After the scan, the
4601                   server will
4602                   begin listening for queries on any newly discovered
4603                   interfaces (provided they are allowed by the
4604                   <span><strong class="command">listen-on</strong></span> configuration), and
4605                   will
4606                   stop listening on interfaces that have gone away.
4607                 </p></dd>
4608 <dt><span class="term"><span><strong class="command">statistics-interval</strong></span></span></dt>
4609 <dd>
4610 <p>
4611                   Name server statistics will be logged
4612                   every <span><strong class="command">statistics-interval</strong></span>
4613                   minutes. The default is
4614                   60. The maximum value is 28 days (40320 minutes).
4615                   If set to 0, no statistics will be logged.
4616                   </p>
4617 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4618 <h3 class="title">Note</h3>
4619 <p>
4620                     Not yet implemented in
4621                     <acronym class="acronym">BIND</acronym> 9.
4622                   </p>
4623 </div>
4624 </dd>
4625 </dl></div>
4626 </div>
4627 <div class="sect3" lang="en">
4628 <div class="titlepage"><div><div><h4 class="title">
4629 <a name="topology"></a>Topology</h4></div></div></div>
4630 <p>
4631             All other things being equal, when the server chooses a name
4632             server
4633             to query from a list of name servers, it prefers the one that is
4634             topologically closest to itself. The <span><strong class="command">topology</strong></span> statement
4635             takes an <span><strong class="command">address_match_list</strong></span> and
4636             interprets it
4637             in a special way. Each top-level list element is assigned a
4638             distance.
4639             Non-negated elements get a distance based on their position in the
4640             list, where the closer the match is to the start of the list, the
4641             shorter the distance is between it and the server. A negated match
4642             will be assigned the maximum distance from the server. If there
4643             is no match, the address will get a distance which is further than
4644             any non-negated list element, and closer than any negated element.
4645             For example,
4646           </p>
4647 <pre class="programlisting">topology {
4648     10/8;
4649     !1.2.3/24;
4650     { 1.2/16; 3/8; };
4651 };</pre>
4652 <p>
4653             will prefer servers on network 10 the most, followed by hosts
4654             on network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the
4655             exception of hosts on network 1.2.3 (netmask 255.255.255.0), which
4656             is preferred least of all.
4657           </p>
4658 <p>
4659             The default topology is
4660           </p>
4661 <pre class="programlisting">    topology { localhost; localnets; };
4662 </pre>
4663 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4664 <h3 class="title">Note</h3>
4665 <p>
4666               The <span><strong class="command">topology</strong></span> option
4667               is not implemented in <acronym class="acronym">BIND</acronym> 9.
4668             </p>
4669 </div>
4670 </div>
4671 <div class="sect3" lang="en">
4672 <div class="titlepage"><div><div><h4 class="title">
4673 <a name="the_sortlist_statement"></a>The <span><strong class="command">sortlist</strong></span> Statement</h4></div></div></div>
4674 <p>
4675             The response to a DNS query may consist of multiple resource
4676             records (RRs) forming a resource records set (RRset).
4677             The name server will normally return the
4678             RRs within the RRset in an indeterminate order
4679             (but see the <span><strong class="command">rrset-order</strong></span>
4680             statement in <a href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">the section called &#8220;RRset Ordering&#8221;</a>).
4681             The client resolver code should rearrange the RRs as appropriate,
4682             that is, using any addresses on the local net in preference to
4683             other addresses.
4684             However, not all resolvers can do this or are correctly
4685             configured.
4686             When a client is using a local server, the sorting can be performed
4687             in the server, based on the client's address. This only requires
4688             configuring the name servers, not all the clients.
4689           </p>
4690 <p>
4691             The <span><strong class="command">sortlist</strong></span> statement (see below)
4692             takes
4693             an <span><strong class="command">address_match_list</strong></span> and
4694             interprets it even
4695             more specifically than the <span><strong class="command">topology</strong></span>
4696             statement
4697             does (<a href="Bv9ARM.ch06.html#topology" title="Topology">the section called &#8220;Topology&#8221;</a>).
4698             Each top level statement in the <span><strong class="command">sortlist</strong></span> must
4699             itself be an explicit <span><strong class="command">address_match_list</strong></span> with
4700             one or two elements. The first element (which may be an IP
4701             address,
4702             an IP prefix, an ACL name or a nested <span><strong class="command">address_match_list</strong></span>)
4703             of each top level list is checked against the source address of
4704             the query until a match is found.
4705           </p>
4706 <p>
4707             Once the source address of the query has been matched, if
4708             the top level statement contains only one element, the actual
4709             primitive
4710             element that matched the source address is used to select the
4711             address
4712             in the response to move to the beginning of the response. If the
4713             statement is a list of two elements, then the second element is
4714             treated the same as the <span><strong class="command">address_match_list</strong></span> in
4715             a <span><strong class="command">topology</strong></span> statement. Each top
4716             level element
4717             is assigned a distance and the address in the response with the
4718             minimum
4719             distance is moved to the beginning of the response.
4720           </p>
4721 <p>
4722             In the following example, any queries received from any of
4723             the addresses of the host itself will get responses preferring
4724             addresses
4725             on any of the locally connected networks. Next most preferred are
4726             addresses
4727             on the 192.168.1/24 network, and after that either the
4728             192.168.2/24
4729             or
4730             192.168.3/24 network with no preference shown between these two
4731             networks. Queries received from a host on the 192.168.1/24 network
4732             will prefer other addresses on that network to the 192.168.2/24
4733             and
4734             192.168.3/24 networks. Queries received from a host on the
4735             192.168.4/24
4736             or the 192.168.5/24 network will only prefer other addresses on
4737             their directly connected networks.
4738           </p>
4739 <pre class="programlisting">sortlist {
4740     // IF the local host
4741     // THEN first fit on the following nets
4742     { localhost;
4743         { localnets;
4744             192.168.1/24;
4745             { 192.168.2/24; 192.168.3/24; }; }; };
4746     // IF on class C 192.168.1 THEN use .1, or .2 or .3
4747     { 192.168.1/24;
4748         { 192.168.1/24;
4749             { 192.168.2/24; 192.168.3/24; }; }; };
4750     // IF on class C 192.168.2 THEN use .2, or .1 or .3
4751     { 192.168.2/24;
4752         { 192.168.2/24;
4753             { 192.168.1/24; 192.168.3/24; }; }; };
4754     // IF on class C 192.168.3 THEN use .3, or .1 or .2
4755     { 192.168.3/24;
4756         { 192.168.3/24;
4757             { 192.168.1/24; 192.168.2/24; }; }; };
4758     // IF .4 or .5 THEN prefer that net
4759     { { 192.168.4/24; 192.168.5/24; };
4760     };
4761 };</pre>
4762 <p>
4763             The following example will give reasonable behavior for the
4764             local host and hosts on directly connected networks. It is similar
4765             to the behavior of the address sort in <acronym class="acronym">BIND</acronym> 4.9.x. Responses sent
4766             to queries from the local host will favor any of the directly
4767             connected
4768             networks. Responses sent to queries from any other hosts on a
4769             directly
4770             connected network will prefer addresses on that same network.
4771             Responses
4772             to other queries will not be sorted.
4773           </p>
4774 <pre class="programlisting">sortlist {
4775            { localhost; localnets; };
4776            { localnets; };
4777 };
4778 </pre>
4779 </div>
4780 <div class="sect3" lang="en">
4781 <div class="titlepage"><div><div><h4 class="title">
4782 <a name="rrset_ordering"></a>RRset Ordering</h4></div></div></div>
4783 <p>
4784             When multiple records are returned in an answer it may be
4785             useful to configure the order of the records placed into the
4786             response.
4787             The <span><strong class="command">rrset-order</strong></span> statement permits
4788             configuration
4789             of the ordering of the records in a multiple record response.
4790             See also the <span><strong class="command">sortlist</strong></span> statement,
4791             <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>.
4792           </p>
4793 <p>
4794             An <span><strong class="command">order_spec</strong></span> is defined as
4795             follows:
4796           </p>
4797 <p>
4798             [<span class="optional">class <em class="replaceable"><code>class_name</code></em></span>]
4799             [<span class="optional">type <em class="replaceable"><code>type_name</code></em></span>]
4800             [<span class="optional">name <em class="replaceable"><code>"domain_name"</code></em></span>]
4801             order <em class="replaceable"><code>ordering</code></em>
4802           </p>
4803 <p>
4804             If no class is specified, the default is <span><strong class="command">ANY</strong></span>.
4805             If no type is specified, the default is <span><strong class="command">ANY</strong></span>.
4806             If no name is specified, the default is "<span><strong class="command">*</strong></span>" (asterisk).
4807           </p>
4808 <p>
4809             The legal values for <span><strong class="command">ordering</strong></span> are:
4810           </p>
4811 <div class="informaltable"><table border="1">
4812 <colgroup>
4813 <col>
4814 <col>
4815 </colgroup>
4816 <tbody>
4817 <tr>
4818 <td>
4819                     <p><span><strong class="command">fixed</strong></span></p>
4820                   </td>
4821 <td>
4822                     <p>
4823                       Records are returned in the order they
4824                       are defined in the zone file.
4825                     </p>
4826                   </td>
4827 </tr>
4828 <tr>
4829 <td>
4830                     <p><span><strong class="command">random</strong></span></p>
4831                   </td>
4832 <td>
4833                     <p>
4834                       Records are returned in some random order.
4835                     </p>
4836                   </td>
4837 </tr>
4838 <tr>
4839 <td>
4840                     <p><span><strong class="command">cyclic</strong></span></p>
4841                   </td>
4842 <td>
4843                     <p>
4844                       Records are returned in a cyclic round-robin order.
4845                     </p>
4846                     <p>
4847                       If <acronym class="acronym">BIND</acronym> is configured with the
4848                       "--enable-fixed-rrset" option at compile time, then
4849                       the initial ordering of the RRset will match the
4850                       one specified in the zone file.
4851                     </p>
4852                   </td>
4853 </tr>
4854 </tbody>
4855 </table></div>
4856 <p>
4857             For example:
4858           </p>
4859 <pre class="programlisting">rrset-order {
4860    class IN type A name "host.example.com" order random;
4861    order cyclic;
4862 };
4863 </pre>
4864 <p>
4865             will cause any responses for type A records in class IN that
4866             have "<code class="literal">host.example.com</code>" as a
4867             suffix, to always be returned
4868             in random order. All other records are returned in cyclic order.
4869           </p>
4870 <p>
4871             If multiple <span><strong class="command">rrset-order</strong></span> statements
4872             appear,
4873             they are not combined &#8212; the last one applies.
4874           </p>
4875 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4876 <h3 class="title">Note</h3>
4877 <p>
4878               In this release of <acronym class="acronym">BIND</acronym> 9, the
4879               <span><strong class="command">rrset-order</strong></span> statement does not support
4880               "fixed" ordering by default.  Fixed ordering can be enabled
4881               at compile time by specifying "--enable-fixed-rrset" on
4882               the "configure" command line.
4883             </p>
4884 </div>
4885 </div>
4886 <div class="sect3" lang="en">
4887 <div class="titlepage"><div><div><h4 class="title">
4888 <a name="tuning"></a>Tuning</h4></div></div></div>
4889 <div class="variablelist"><dl>
4890 <dt><span class="term"><span><strong class="command">lame-ttl</strong></span></span></dt>
4891 <dd>
4892 <p>
4893                   Sets the number of seconds to cache a
4894                   lame server indication. 0 disables caching. (This is
4895                   <span class="bold"><strong>NOT</strong></span> recommended.)
4896                   The default is <code class="literal">600</code> (10 minutes) and the
4897                   maximum value is
4898                   <code class="literal">1800</code> (30 minutes).
4899                 </p>
4900 <p>
4901                   Lame-ttl also controls the amount of time DNSSEC
4902                   validation failures are cached.  There is a minimum
4903                   of 30 seconds applied to bad cache entries if the
4904                   lame-ttl is set to less than 30 seconds.
4905                 </p>
4906 </dd>
4907 <dt><span class="term"><span><strong class="command">max-ncache-ttl</strong></span></span></dt>
4908 <dd><p>
4909                   To reduce network traffic and increase performance,
4910                   the server stores negative answers. <span><strong class="command">max-ncache-ttl</strong></span> is
4911                   used to set a maximum retention time for these answers in
4912                   the server
4913                   in seconds. The default
4914                   <span><strong class="command">max-ncache-ttl</strong></span> is <code class="literal">10800</code> seconds (3 hours).
4915                   <span><strong class="command">max-ncache-ttl</strong></span> cannot exceed
4916                   7 days and will
4917                   be silently truncated to 7 days if set to a greater value.
4918                 </p></dd>
4919 <dt><span class="term"><span><strong class="command">max-cache-ttl</strong></span></span></dt>
4920 <dd><p>
4921                   Sets the maximum time for which the server will
4922                   cache ordinary (positive) answers. The default is
4923                   one week (7 days).
4924                   A value of zero may cause all queries to return
4925                   SERVFAIL, because of lost caches of intermediate
4926                   RRsets (such as NS and glue AAAA/A records) in the
4927                   resolution process.
4928                 </p></dd>
4929 <dt><span class="term"><span><strong class="command">min-roots</strong></span></span></dt>
4930 <dd>
4931 <p>
4932                   The minimum number of root servers that
4933                   is required for a request for the root servers to be
4934                   accepted. The default
4935                   is <strong class="userinput"><code>2</code></strong>.
4936                 </p>
4937 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4938 <h3 class="title">Note</h3>
4939 <p>
4940                     Not implemented in <acronym class="acronym">BIND</acronym> 9.
4941                   </p>
4942 </div>
4943 </dd>
4944 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
4945 <dd>
4946 <p>
4947                   Specifies the number of days into the future when
4948                   DNSSEC signatures automatically generated as a
4949                   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
4950                   is an optional second field which specifies how
4951                   long before expiry that the signatures will be
4952                   regenerated.  If not specified, the signatures will
4953                   be regenerated at 1/4 of base interval.  The second
4954                   field is specified in days if the base interval is
4955                   greater than 7 days otherwise it is specified in hours.
4956                   The default base interval is <code class="literal">30</code> days
4957                   giving a re-signing interval of 7 1/2 days.  The maximum
4958                   values are 10 years (3660 days).
4959                 </p>
4960 <p>
4961                   The signature inception time is unconditionally
4962                   set to one hour before the current time to allow
4963                   for a limited amount of clock skew.
4964                 </p>
4965 <p>
4966                   The <span><strong class="command">sig-validity-interval</strong></span>
4967                   should be, at least, several multiples of the SOA
4968                   expire interval to allow for reasonable interaction
4969                   between the various timer and expiry dates.
4970                 </p>
4971 </dd>
4972 <dt><span class="term"><span><strong class="command">sig-signing-nodes</strong></span></span></dt>
4973 <dd><p>
4974                   Specify the maximum number of nodes to be
4975                   examined in each quantum when signing a zone with
4976                   a new DNSKEY. The default is
4977                   <code class="literal">100</code>.
4978                 </p></dd>
4979 <dt><span class="term"><span><strong class="command">sig-signing-signatures</strong></span></span></dt>
4980 <dd><p>
4981                   Specify a threshold number of signatures that
4982                   will terminate processing a quantum when signing
4983                   a zone with a new DNSKEY.  The default is
4984                   <code class="literal">10</code>.
4985                 </p></dd>
4986 <dt><span class="term"><span><strong class="command">sig-signing-type</strong></span></span></dt>
4987 <dd>
4988 <p>
4989                   Specify a private RDATA type to be used when generating
4990                   key signing records.  The default is
4991                   <code class="literal">65535</code>.
4992                 </p>
4993 <p>
4994                   It is expected that this parameter may be removed
4995                   in a future version once there is a standard type.
4996                 </p>
4997 </dd>
4998 <dt>
4999 <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>
5000 </dt>
5001 <dd>
5002 <p>
5003                   These options control the server's behavior on refreshing a
5004                   zone
5005                   (querying for SOA changes) or retrying failed transfers.
5006                   Usually the SOA values for the zone are used, but these
5007                   values
5008                   are set by the master, giving slave server administrators
5009                   little
5010                   control over their contents.
5011                 </p>
5012 <p>
5013                   These options allow the administrator to set a minimum and
5014                   maximum
5015                   refresh and retry time either per-zone, per-view, or
5016                   globally.
5017                   These options are valid for slave and stub zones,
5018                   and clamp the SOA refresh and retry times to the specified
5019                   values.
5020                 </p>
5021 <p>
5022                   The following defaults apply.
5023                   <span><strong class="command">min-refresh-time</strong></span> 300 seconds,
5024                   <span><strong class="command">max-refresh-time</strong></span> 2419200 seconds
5025                   (4 weeks), <span><strong class="command">min-retry-time</strong></span> 500 seconds,
5026                   and <span><strong class="command">max-retry-time</strong></span> 1209600 seconds
5027                   (2 weeks).
5028                 </p>
5029 </dd>
5030 <dt><span class="term"><span><strong class="command">edns-udp-size</strong></span></span></dt>
5031 <dd>
5032 <p>
5033                   Sets the advertised EDNS UDP buffer size in bytes
5034                   to control the size of packets received.
5035                   Valid values are 512 to 4096 (values outside this range
5036                   will be silently adjusted).  The default value
5037                   is 4096.  The usual reason for setting
5038                   <span><strong class="command">edns-udp-size</strong></span> to a non-default
5039                   value is to get UDP answers to pass through broken
5040                   firewalls that block fragmented packets and/or
5041                   block UDP packets that are greater than 512 bytes.
5042                 </p>
5043 <p>
5044                   <span><strong class="command">named</strong></span> will fallback to using 512 bytes
5045                   if it get a series of timeout at the initial value.  512
5046                   bytes is not being offered to encourage sites to fix their
5047                   firewalls.  Small EDNS UDP sizes will result in the
5048                   excessive use of TCP.
5049                 </p>
5050 </dd>
5051 <dt><span class="term"><span><strong class="command">max-udp-size</strong></span></span></dt>
5052 <dd>
5053 <p>
5054                   Sets the maximum EDNS UDP message size
5055                   <span><strong class="command">named</strong></span> will send in bytes.
5056                   Valid values are 512 to 4096 (values outside this
5057                   range will be silently adjusted).  The default
5058                   value is 4096.  The usual reason for setting
5059                   <span><strong class="command">max-udp-size</strong></span> to a non-default
5060                   value is to get UDP answers to pass through broken
5061                   firewalls that block fragmented packets and/or
5062                   block UDP packets that are greater than 512 bytes.
5063                   This is independent of the advertised receive
5064                   buffer (<span><strong class="command">edns-udp-size</strong></span>).
5065                 </p>
5066 <p>
5067                   Setting this to a low value will encourage additional
5068                   TCP traffic to the nameserver.
5069                 </p>
5070 </dd>
5071 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
5072 <dd><p>Specifies
5073                   the file format of zone files (see
5074                   <a href="Bv9ARM.ch06.html#zonefile_format" title="Additional File Formats">the section called &#8220;Additional File Formats&#8221;</a>).
5075                   The default value is <code class="constant">text</code>, which is the
5076                   standard textual representation.  Files in other formats
5077                   than <code class="constant">text</code> are typically expected
5078                   to be generated by the <span><strong class="command">named-compilezone</strong></span> tool.
5079                   Note that when a zone file in a different format than
5080                   <code class="constant">text</code> is loaded, <span><strong class="command">named</strong></span>
5081                   may omit some of the checks which would be performed for a
5082                   file in the <code class="constant">text</code> format.  In particular,
5083                   <span><strong class="command">check-names</strong></span> checks do not apply
5084                   for the <code class="constant">raw</code> format.  This means
5085                   a zone file in the <code class="constant">raw</code> format
5086                   must be generated with the same check level as that
5087                   specified in the <span><strong class="command">named</strong></span> configuration
5088                   file.  This statement sets the
5089                   <span><strong class="command">masterfile-format</strong></span> for all zones,
5090                   but can be overridden on a per-zone or per-view basis
5091                   by including a <span><strong class="command">masterfile-format</strong></span>
5092                   statement within the <span><strong class="command">zone</strong></span> or
5093                   <span><strong class="command">view</strong></span> block in the configuration
5094                   file.
5095                 </p></dd>
5096 <dt>
5097 <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>
5098 </dt>
5099 <dd>
5100 <p>These set the
5101                   initial value (minimum) and maximum number of recursive
5102                   simultaneous clients for any given query
5103                   (&lt;qname,qtype,qclass&gt;) that the server will accept
5104                   before dropping additional clients.  <span><strong class="command">named</strong></span> will attempt to
5105                   self tune this value and changes will be logged.  The
5106                   default values are 10 and 100.
5107                 </p>
5108 <p>
5109                   This value should reflect how many queries come in for
5110                   a given name in the time it takes to resolve that name.
5111                   If the number of queries exceed this value, <span><strong class="command">named</strong></span> will
5112                   assume that it is dealing with a non-responsive zone
5113                   and will drop additional queries.  If it gets a response
5114                   after dropping queries, it will raise the estimate.  The
5115                   estimate will then be lowered in 20 minutes if it has
5116                   remained unchanged.
5117                 </p>
5118 <p>
5119                   If <span><strong class="command">clients-per-query</strong></span> is set to zero,
5120                   then there is no limit on the number of clients per query
5121                   and no queries will be dropped.
5122                 </p>
5123 <p>
5124                   If <span><strong class="command">max-clients-per-query</strong></span> is set to zero,
5125                   then there is no upper bound other than imposed by
5126                   <span><strong class="command">recursive-clients</strong></span>.
5127                 </p>
5128 </dd>
5129 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
5130 <dd>
5131 <p>
5132                   The delay, in seconds, between sending sets of notify
5133                   messages for a zone.  The default is five (5) seconds.
5134                 </p>
5135 <p>
5136                   The overall rate that NOTIFY messages are sent for all
5137                   zones is controlled by <span><strong class="command">serial-query-rate</strong></span>.
5138                 </p>
5139 </dd>
5140 </dl></div>
5141 </div>
5142 <div class="sect3" lang="en">
5143 <div class="titlepage"><div><div><h4 class="title">
5144 <a name="builtin"></a>Built-in server information zones</h4></div></div></div>
5145 <p>
5146             The server provides some helpful diagnostic information
5147             through a number of built-in zones under the
5148             pseudo-top-level-domain <code class="literal">bind</code> in the
5149             <span><strong class="command">CHAOS</strong></span> class.  These zones are part
5150             of a
5151             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
5152             class
5153             <span><strong class="command">CHAOS</strong></span> which is separate from the
5154             default view of
5155             class <span><strong class="command">IN</strong></span>; therefore, any global
5156             server options
5157             such as <span><strong class="command">allow-query</strong></span> do not apply
5158             the these zones.
5159             If you feel the need to disable these zones, use the options
5160             below, or hide the built-in <span><strong class="command">CHAOS</strong></span>
5161             view by
5162             defining an explicit view of class <span><strong class="command">CHAOS</strong></span>
5163             that matches all clients.
5164           </p>
5165 <div class="variablelist"><dl>
5166 <dt><span class="term"><span><strong class="command">version</strong></span></span></dt>
5167 <dd><p>
5168                   The version the server should report
5169                   via a query of the name <code class="literal">version.bind</code>
5170                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5171                   The default is the real version number of this server.
5172                   Specifying <span><strong class="command">version none</strong></span>
5173                   disables processing of the queries.
5174                 </p></dd>
5175 <dt><span class="term"><span><strong class="command">hostname</strong></span></span></dt>
5176 <dd><p>
5177                   The hostname the server should report via a query of
5178                   the name <code class="filename">hostname.bind</code>
5179                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5180                   This defaults to the hostname of the machine hosting the
5181                   name server as
5182                   found by the gethostname() function.  The primary purpose of such queries
5183                   is to
5184                   identify which of a group of anycast servers is actually
5185                   answering your queries.  Specifying <span><strong class="command">hostname none;</strong></span>
5186                   disables processing of the queries.
5187                 </p></dd>
5188 <dt><span class="term"><span><strong class="command">server-id</strong></span></span></dt>
5189 <dd><p>
5190                   The ID the server should report when receiving a Name
5191                   Server Identifier (NSID) query, or a query of the name
5192                   <code class="filename">ID.SERVER</code> with type
5193                   <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5194                   The primary purpose of such queries is to
5195                   identify which of a group of anycast servers is actually
5196                   answering your queries.  Specifying <span><strong class="command">server-id none;</strong></span>
5197                   disables processing of the queries.
5198                   Specifying <span><strong class="command">server-id hostname;</strong></span> will cause <span><strong class="command">named</strong></span> to
5199                   use the hostname as found by the gethostname() function.
5200                   The default <span><strong class="command">server-id</strong></span> is <span><strong class="command">none</strong></span>.
5201                 </p></dd>
5202 </dl></div>
5203 </div>
5204 <div class="sect3" lang="en">
5205 <div class="titlepage"><div><div><h4 class="title">
5206 <a name="empty"></a>Built-in Empty Zones</h4></div></div></div>
5207 <p>
5208             Named has some built-in empty zones (SOA and NS records only).
5209             These are for zones that should normally be answered locally
5210             and which queries should not be sent to the Internet's root
5211             servers.  The official servers which cover these namespaces
5212             return NXDOMAIN responses to these queries.  In particular,
5213             these cover the reverse namespace for addresses from RFC 1918 and
5214             RFC 3330.  They also include the reverse namespace for IPv6 local
5215             address (locally assigned), IPv6 link local addresses, the IPv6
5216             loopback address and the IPv6 unknown address.
5217           </p>
5218 <p>
5219             Named will attempt to determine if a built-in zone already exists
5220             or is active (covered by a forward-only forwarding declaration)
5221             and will not create an empty zone in that case.
5222           </p>
5223 <p>
5224             The current list of empty zones is:
5225             </p>
5226 <div class="itemizedlist"><ul type="disc">
5227 <li>10.IN-ADDR.ARPA</li>
5228 <li>16.172.IN-ADDR.ARPA</li>
5229 <li>17.172.IN-ADDR.ARPA</li>
5230 <li>18.172.IN-ADDR.ARPA</li>
5231 <li>19.172.IN-ADDR.ARPA</li>
5232 <li>20.172.IN-ADDR.ARPA</li>
5233 <li>21.172.IN-ADDR.ARPA</li>
5234 <li>22.172.IN-ADDR.ARPA</li>
5235 <li>23.172.IN-ADDR.ARPA</li>
5236 <li>24.172.IN-ADDR.ARPA</li>
5237 <li>25.172.IN-ADDR.ARPA</li>
5238 <li>26.172.IN-ADDR.ARPA</li>
5239 <li>27.172.IN-ADDR.ARPA</li>
5240 <li>28.172.IN-ADDR.ARPA</li>
5241 <li>29.172.IN-ADDR.ARPA</li>
5242 <li>30.172.IN-ADDR.ARPA</li>
5243 <li>31.172.IN-ADDR.ARPA</li>
5244 <li>168.192.IN-ADDR.ARPA</li>
5245 <li>0.IN-ADDR.ARPA</li>
5246 <li>127.IN-ADDR.ARPA</li>
5247 <li>254.169.IN-ADDR.ARPA</li>
5248 <li>2.0.192.IN-ADDR.ARPA</li>
5249 <li>100.51.198.IN-ADDR.ARPA</li>
5250 <li>113.0.203.IN-ADDR.ARPA</li>
5251 <li>255.255.255.255.IN-ADDR.ARPA</li>
5252 <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>
5253 <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>
5254 <li>8.B.D.0.1.0.0.2.IP6.ARPA</li>
5255 <li>D.F.IP6.ARPA</li>
5256 <li>8.E.F.IP6.ARPA</li>
5257 <li>9.E.F.IP6.ARPA</li>
5258 <li>A.E.F.IP6.ARPA</li>
5259 <li>B.E.F.IP6.ARPA</li>
5260 </ul></div>
5261 <p>
5262           </p>
5263 <p>
5264             Empty zones are settable at the view level and only apply to
5265             views of class IN.  Disabled empty zones are only inherited
5266             from options if there are no disabled empty zones specified
5267             at the view level.  To override the options list of disabled
5268             zones, you can disable the root zone at the view level, for example:
5269 </p>
5270 <pre class="programlisting">
5271             disable-empty-zone ".";
5272 </pre>
5273 <p>
5274           </p>
5275 <p>
5276             If you are using the address ranges covered here, you should
5277             already have reverse zones covering the addresses you use.
5278             In practice this appears to not be the case with many queries
5279             being made to the infrastructure servers for names in these
5280             spaces.  So many in fact that sacrificial servers were needed
5281             to be deployed to channel the query load away from the
5282             infrastructure servers.
5283           </p>
5284 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5285 <h3 class="title">Note</h3>
5286             The real parent servers for these zones should disable all
5287             empty zone under the parent zone they serve.  For the real
5288             root servers, this is all built-in empty zones.  This will
5289             enable them to return referrals to deeper in the tree.
5290           </div>
5291 <div class="variablelist"><dl>
5292 <dt><span class="term"><span><strong class="command">empty-server</strong></span></span></dt>
5293 <dd><p>
5294                   Specify what server name will appear in the returned
5295                   SOA record for empty zones.  If none is specified, then
5296                   the zone's name will be used.
5297                 </p></dd>
5298 <dt><span class="term"><span><strong class="command">empty-contact</strong></span></span></dt>
5299 <dd><p>
5300                   Specify what contact name will appear in the returned
5301                   SOA record for empty zones.  If none is specified, then
5302                   "." will be used.
5303                 </p></dd>
5304 <dt><span class="term"><span><strong class="command">empty-zones-enable</strong></span></span></dt>
5305 <dd><p>
5306                   Enable or disable all empty zones.  By default, they
5307                   are enabled.
5308                 </p></dd>
5309 <dt><span class="term"><span><strong class="command">disable-empty-zone</strong></span></span></dt>
5310 <dd><p>
5311                   Disable individual empty zones.  By default, none are
5312                   disabled.  This option can be specified multiple times.
5313                 </p></dd>
5314 </dl></div>
5315 </div>
5316 <div class="sect3" lang="en">
5317 <div class="titlepage"><div><div><h4 class="title">
5318 <a name="acache"></a>Additional Section Caching</h4></div></div></div>
5319 <p>
5320             The additional section cache, also called <span><strong class="command">acache</strong></span>,
5321             is an internal cache to improve the response performance of BIND 9.
5322             When additional section caching is enabled, BIND 9 will
5323             cache an internal short-cut to the additional section content for
5324             each answer RR.
5325             Note that <span><strong class="command">acache</strong></span> is an internal caching
5326             mechanism of BIND 9, and is not related to the DNS caching
5327             server function.
5328           </p>
5329 <p>
5330             Additional section caching does not change the
5331             response content (except the RRsets ordering of the additional
5332             section, see below), but can improve the response performance
5333             significantly.
5334             It is particularly effective when BIND 9 acts as an authoritative
5335             server for a zone that has many delegations with many glue RRs.
5336           </p>
5337 <p>
5338             In order to obtain the maximum performance improvement
5339             from additional section caching, setting
5340             <span><strong class="command">additional-from-cache</strong></span>
5341             to <span><strong class="command">no</strong></span> is recommended, since the current
5342             implementation of <span><strong class="command">acache</strong></span>
5343             does not short-cut of additional section information from the
5344             DNS cache data.
5345           </p>
5346 <p>
5347             One obvious disadvantage of <span><strong class="command">acache</strong></span> is
5348             that it requires much more
5349             memory for the internal cached data.
5350             Thus, if the response performance does not matter and memory
5351             consumption is much more critical, the
5352             <span><strong class="command">acache</strong></span> mechanism can be
5353             disabled by setting <span><strong class="command">acache-enable</strong></span> to
5354             <span><strong class="command">no</strong></span>.
5355             It is also possible to specify the upper limit of memory
5356             consumption
5357             for acache by using <span><strong class="command">max-acache-size</strong></span>.
5358           </p>
5359 <p>
5360             Additional section caching also has a minor effect on the
5361             RRset ordering in the additional section.
5362             Without <span><strong class="command">acache</strong></span>,
5363             <span><strong class="command">cyclic</strong></span> order is effective for the additional
5364             section as well as the answer and authority sections.
5365             However, additional section caching fixes the ordering when it
5366             first caches an RRset for the additional section, and the same
5367             ordering will be kept in succeeding responses, regardless of the
5368             setting of <span><strong class="command">rrset-order</strong></span>.
5369             The effect of this should be minor, however, since an
5370             RRset in the additional section
5371             typically only contains a small number of RRs (and in many cases
5372             it only contains a single RR), in which case the
5373             ordering does not matter much.
5374           </p>
5375 <p>
5376             The following is a summary of options related to
5377             <span><strong class="command">acache</strong></span>.
5378           </p>
5379 <div class="variablelist"><dl>
5380 <dt><span class="term"><span><strong class="command">acache-enable</strong></span></span></dt>
5381 <dd><p>
5382                   If <span><strong class="command">yes</strong></span>, additional section caching is
5383                   enabled.  The default value is <span><strong class="command">no</strong></span>.
5384                 </p></dd>
5385 <dt><span class="term"><span><strong class="command">acache-cleaning-interval</strong></span></span></dt>
5386 <dd><p>
5387                   The server will remove stale cache entries, based on an LRU
5388                   based
5389                   algorithm, every <span><strong class="command">acache-cleaning-interval</strong></span> minutes.
5390                   The default is 60 minutes.
5391                   If set to 0, no periodic cleaning will occur.
5392                 </p></dd>
5393 <dt><span class="term"><span><strong class="command">max-acache-size</strong></span></span></dt>
5394 <dd><p>
5395                   The maximum amount of memory in bytes to use for the server's acache.
5396                   When the amount of data in the acache reaches this limit,
5397                   the server
5398                   will clean more aggressively so that the limit is not
5399                   exceeded.
5400                   In a server with multiple views, the limit applies
5401                   separately to the
5402                   acache of each view.
5403                   The default is <code class="literal">16M</code>.
5404                 </p></dd>
5405 </dl></div>
5406 </div>
5407 <div class="sect3" lang="en">
5408 <div class="titlepage"><div><div><h4 class="title">
5409 <a name="id2588113"></a>Content Filtering</h4></div></div></div>
5410 <p>
5411             <acronym class="acronym">BIND</acronym> 9 provides the ability to filter
5412             out DNS responses from external DNS servers containing
5413             certain types of data in the answer section.
5414             Specifically, it can reject address (A or AAAA) records if
5415             the corresponding IPv4 or IPv6 addresses match the given
5416             <code class="varname">address_match_list</code> of the
5417             <span><strong class="command">deny-answer-addresses</strong></span> option.
5418             It can also reject CNAME or DNAME records if the "alias"
5419             name (i.e., the CNAME alias or the substituted query name
5420             due to DNAME) matches the
5421             given <code class="varname">namelist</code> of the
5422             <span><strong class="command">deny-answer-aliases</strong></span> option, where
5423             "match" means the alias name is a subdomain of one of
5424             the <code class="varname">name_list</code> elements.
5425             If the optional <code class="varname">namelist</code> is specified
5426             with <span><strong class="command">except-from</strong></span>, records whose query name
5427             matches the list will be accepted regardless of the filter
5428             setting.
5429             Likewise, if the alias name is a subdomain of the
5430             corresponding zone, the <span><strong class="command">deny-answer-aliases</strong></span>
5431             filter will not apply;
5432             for example, even if "example.com" is specified for
5433             <span><strong class="command">deny-answer-aliases</strong></span>,
5434           </p>
5435 <pre class="programlisting">www.example.com. CNAME xxx.example.com.</pre>
5436 <p>
5437             returned by an "example.com" server will be accepted.
5438           </p>
5439 <p>
5440             In the <code class="varname">address_match_list</code> of the
5441             <span><strong class="command">deny-answer-addresses</strong></span> option, only
5442             <code class="varname">ip_addr</code>
5443             and <code class="varname">ip_prefix</code>
5444             are meaningful;
5445             any <code class="varname">key_id</code> will be silently ignored.
5446           </p>
5447 <p>
5448             If a response message is rejected due to the filtering,
5449             the entire message is discarded without being cached, and
5450             a SERVFAIL error will be returned to the client.
5451           </p>
5452 <p>
5453             This filtering is intended to prevent "DNS rebinding attacks," in
5454             which an attacker, in response to a query for a domain name the
5455             attacker controls, returns an IP address within your own network or
5456             an alias name within your own domain.
5457             A naive web browser or script could then serve as an
5458             unintended proxy, allowing the attacker
5459             to get access to an internal node of your local network
5460             that couldn't be externally accessed otherwise.
5461             See the paper available at
5462             <a href="" target="_top">
5463             http://portal.acm.org/citation.cfm?id=1315245.1315298
5464             </a>
5465             for more details about the attacks.
5466           </p>
5467 <p>
5468             For example, if you own a domain named "example.net" and
5469             your internal network uses an IPv4 prefix 192.0.2.0/24,
5470             you might specify the following rules:
5471           </p>
5472 <pre class="programlisting">deny-answer-addresses { 192.0.2.0/24; } except-from { "example.net"; };
5473 deny-answer-aliases { "example.net"; };
5474 </pre>
5475 <p>
5476             If an external attacker lets a web browser in your local
5477             network look up an IPv4 address of "attacker.example.com",
5478             the attacker's DNS server would return a response like this:
5479           </p>
5480 <pre class="programlisting">attacker.example.com. A 192.0.2.1</pre>
5481 <p>
5482             in the answer section.
5483             Since the rdata of this record (the IPv4 address) matches
5484             the specified prefix 192.0.2.0/24, this response will be
5485             ignored.
5486           </p>
5487 <p>
5488             On the other hand, if the browser looks up a legitimate
5489             internal web server "www.example.net" and the
5490             following response is returned to
5491             the <acronym class="acronym">BIND</acronym> 9 server
5492           </p>
5493 <pre class="programlisting">www.example.net. A 192.0.2.2</pre>
5494 <p>
5495             it will be accepted since the owner name "www.example.net"
5496             matches the <span><strong class="command">except-from</strong></span> element,
5497             "example.net".
5498           </p>
5499 <p>
5500             Note that this is not really an attack on the DNS per se.
5501             In fact, there is nothing wrong for an "external" name to
5502             be mapped to your "internal" IP address or domain name
5503             from the DNS point of view.
5504             It might actually be provided for a legitimate purpose,
5505             such as for debugging.
5506             As long as the mapping is provided by the correct owner,
5507             it is not possible or does not make sense to detect
5508             whether the intent of the mapping is legitimate or not
5509             within the DNS.
5510             The "rebinding" attack must primarily be protected at the
5511             application that uses the DNS.
5512             For a large site, however, it may be difficult to protect
5513             all possible applications at once.
5514             This filtering feature is provided only to help such an
5515             operational environment;
5516             it is generally discouraged to turn it on unless you are
5517             very sure you have no other choice and the attack is a
5518             real threat for your applications.
5519           </p>
5520 <p>
5521             Care should be particularly taken if you want to use this
5522             option for addresses within 127.0.0.0/8.
5523             These addresses are obviously "internal", but many
5524             applications conventionally rely on a DNS mapping from
5525             some name to such an address.
5526             Filtering out DNS records containing this address
5527             spuriously can break such applications.
5528           </p>
5529 </div>
5530 <div class="sect3" lang="en">
5531 <div class="titlepage"><div><div><h4 class="title">
5532 <a name="id2588372"></a>Response Policy Zone (RPZ) Rewriting</h4></div></div></div>
5533 <p>
5534             <acronym class="acronym">BIND</acronym> 9 includes an intentionally limited
5535             mechanism to modify DNS responses for recursive requests
5536             similar to email anti-spam DNS blacklists.
5537             All response policy zones are named in the
5538             <span><strong class="command">response-policy</strong></span> option for the view or among the
5539             global options if there is no response-policy option for the view.
5540           </p>
5541 <p>
5542             The rules encoded in a response policy zone (RPZ) are applied
5543             only to responses to queries that ask for recursion (RD=1).
5544             RPZs are normal DNS zones containing RRsets
5545             that can be queried normally if allowed.
5546             It is usually best to restrict those queries with something like
5547             <span><strong class="command">allow-query {none; };</strong></span> or
5548             <span><strong class="command">allow-query { 127.0.0.1; };</strong></span>.
5549           </p>
5550 <p>
5551             There are four kinds of RPZ rewrite rules.  QNAME rules are
5552             applied to query names in requests and to targets of CNAME
5553             records resolved in the process of generating the response.
5554             The owner name of a QNAME rule is the query name relativized
5555             to the RPZ.
5556             The records in a rewrite rule are usually A, AAAA, or special
5557             CNAMEs, but can be any type except DNAME.
5558           </p>
5559 <p>
5560             IP rules are triggered by addresses in A and AAAA records.
5561             All IP addresses in A or AAAA RRsets are tested and the rule
5562             longest prefix is applied.  Ties between rules with equal prefixes
5563             are broken in favor of the first RPZ mentioned in the
5564             response-policy option.
5565             The rule matching the smallest IP address is chosen among equal
5566             prefix rules from a single RPZ.
5567             IP rules are expressed in RRsets with owner names that are
5568             subdomains of rpz-ip and encoding an IP address block, reversed
5569             as in IN-ARPA.
5570             prefix.B.B.B.B with prefix between 1 and 32 and B between 1 and 255
5571             encodes an IPv4 address.
5572             IPv6 addresses are encoded by with prefix.W.W.W.W.W.W.W.W or
5573             prefix.WORDS.zz.WORDS.  The words in the standard IPv6 text
5574             representation are reversed, "::" is replaced with ".zz.",
5575             and ":" becomes ".".
5576           </p>
5577 <p>
5578             NSDNAME rules match names in NS RRsets for the response or a
5579             parent.  They are encoded as subdomains of rpz-nsdomain relativized
5580             to the RPZ origin name.
5581           </p>
5582 <p>
5583             NSIP rules match IP addresses in A and AAAA RRsets for names of
5584             responsible servers or the names that can be matched by NSDNAME
5585             rules.  The are encoded like IP rules except as subdomains of
5586             rpz-nsip.
5587           </p>
5588 <p>
5589             Authority verification issues and variations in authority data in
5590             the current version of <acronym class="acronym">BIND</acronym> 9 can cause
5591             inconsistent results from NSIP and NSDNAME.  So they are available
5592             only when <acronym class="acronym">BIND</acronym> is built with the
5593             <strong class="userinput"><code>--enable-rpz-nsip</code></strong> or
5594             <strong class="userinput"><code>--enable-rpz-nsdname</code></strong> options
5595             on the "configure" command line.
5596           </p>
5597 <p>
5598             Four policies can be expressed.
5599             The <span><strong class="command">NXDOMAIN</strong></span> policy causes a NXDOMAIN response
5600             and is expressed with an RRset consisting of a single CNAME
5601             whose target is the root domain (.).
5602             <span><strong class="command">NODATA</strong></span> generates NODATA or ANCOUNT=1 regardless
5603             of query type.
5604             It is expressed with a CNAME whose target is the wildcard
5605             top-level domain (*.).
5606             The <span><strong class="command">NO-OP</strong></span> policy does not change the response
5607             and is used to "poke holes" in policies for larger CIDR blocks or in
5608             zones named later in the <span><strong class="command">response-policy</strong></span> option.
5609             The NO-OP policy is expressed by a CNAME with a target consisting
5610             of the variable part of the owner name, such as "example.com." for
5611             a QNAME rule or "128.1.0.0.127." for an IP rule.
5612             The <span><strong class="command">CNAME</strong></span> policy is used to replace the RRsets
5613             of response.
5614             A and AAAA RRsets are most common and useful to capture
5615             an evil domain in a walled garden, but any valid set of RRsets
5616             is possible.
5617           </p>
5618 <p>
5619             All of the policies in an RPZ can be overridden with a
5620             <span><strong class="command">policy</strong></span> clause.
5621             <span><strong class="command">given</strong></span> says "do not override."
5622             <span><strong class="command">no-op</strong></span> says "do nothing" regardless of the policy
5623             in RPZ records.
5624             <span><strong class="command">nxdomain</strong></span> causes all RPZ rules to generate
5625             NXDOMAIN results.
5626             <span><strong class="command">nodata</strong></span> gives nodata.
5627             <span><strong class="command">cname domain</strong></span> causes all RPZ rules to act as if
5628             the consisted of a "cname domain" record.
5629           </p>
5630 <p>
5631             For example, you might use this option statement
5632           </p>
5633 <pre class="programlisting">response-policy { zone "bl"; };</pre>
5634 <p>
5635             and this zone statement
5636           </p>
5637 <pre class="programlisting">zone "bl" {type master; file "example/bl"; allow-query {none;}; };</pre>
5638 <p>
5639             with this zone file
5640           </p>
5641 <pre class="programlisting">$TTL 1H
5642 @                   SOA LOCALHOST. named-mgr.example.com (1 1h 15m 30d 2h)
5643
5644 ; QNAME rules
5645 nxdomain.domain.com         CNAME   .
5646 nodata.domain.com           CNAME   *.
5647 bad.domain.com              A       10.0.0.1
5648                             AAAA    2001:2::1
5649 ok.domain.com               CNAME   ok.domain.com.
5650 *.badzone.domain.com        CNAME   garden.example.com.
5651
5652 ; IP rules rewriting all answers for 127/8 except 127.0.0.1
5653 8.0.0.0.127.ip              CNAME   .
5654 32.1.0.0.127.ip             CNAME   32.1.0.0.127.
5655
5656 ; NSDNAME and NSIP rules
5657 ns.domain.com.rpz-nsdname   CNAME   .
5658 48.zz.2.2001.rpz-nsip       CNAME   .
5659 </pre>
5660 </div>
5661 </div>
5662 <div class="sect2" lang="en">
5663 <div class="titlepage"><div><div><h3 class="title">
5664 <a name="server_statement_grammar"></a><span><strong class="command">server</strong></span> Statement Grammar</h3></div></div></div>
5665 <pre class="programlisting"><span><strong class="command">server</strong></span> <em class="replaceable"><code>ip_addr[/prefixlen]</code></em> {
5666     [<span class="optional"> bogus <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5667     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5668     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5669     [<span class="optional"> edns <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5670     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
5671     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
5672     [<span class="optional"> transfers <em class="replaceable"><code>number</code></em> ; </span>]
5673     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em> ; ]</span>]
5674     [<span class="optional"> keys <em class="replaceable"><code>{ string ; [<span class="optional"> string ; [<span class="optional">...</span>]</span>] }</code></em> ; </span>]
5675     [<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>]
5676     [<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>]
5677     [<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>]
5678     [<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>]
5679     [<span class="optional"> query-source [<span class="optional"> address ( <em class="replaceable"><code>ip_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
5680                   [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]; </span>]
5681     [<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>]
5682                      [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]; </span>]
5683     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5684     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
5685     [<span class="optional"> queryport-pool-updateinterval <em class="replaceable"><code>number</code></em>; </span>]
5686 };
5687 </pre>
5688 </div>
5689 <div class="sect2" lang="en">
5690 <div class="titlepage"><div><div><h3 class="title">
5691 <a name="server_statement_definition_and_usage"></a><span><strong class="command">server</strong></span> Statement Definition and
5692             Usage</h3></div></div></div>
5693 <p>
5694             The <span><strong class="command">server</strong></span> statement defines
5695             characteristics
5696             to be associated with a remote name server.  If a prefix length is
5697             specified, then a range of servers is covered.  Only the most
5698             specific
5699             server clause applies regardless of the order in
5700             <code class="filename">named.conf</code>.
5701           </p>
5702 <p>
5703             The <span><strong class="command">server</strong></span> statement can occur at
5704             the top level of the
5705             configuration file or inside a <span><strong class="command">view</strong></span>
5706             statement.
5707             If a <span><strong class="command">view</strong></span> statement contains
5708             one or more <span><strong class="command">server</strong></span> statements, only
5709             those
5710             apply to the view and any top-level ones are ignored.
5711             If a view contains no <span><strong class="command">server</strong></span>
5712             statements,
5713             any top-level <span><strong class="command">server</strong></span> statements are
5714             used as
5715             defaults.
5716           </p>
5717 <p>
5718             If you discover that a remote server is giving out bad data,
5719             marking it as bogus will prevent further queries to it. The
5720             default
5721             value of <span><strong class="command">bogus</strong></span> is <span><strong class="command">no</strong></span>.
5722           </p>
5723 <p>
5724             The <span><strong class="command">provide-ixfr</strong></span> clause determines
5725             whether
5726             the local server, acting as master, will respond with an
5727             incremental
5728             zone transfer when the given remote server, a slave, requests it.
5729             If set to <span><strong class="command">yes</strong></span>, incremental transfer
5730             will be provided
5731             whenever possible. If set to <span><strong class="command">no</strong></span>,
5732             all transfers
5733             to the remote server will be non-incremental. If not set, the
5734             value
5735             of the <span><strong class="command">provide-ixfr</strong></span> option in the
5736             view or
5737             global options block is used as a default.
5738           </p>
5739 <p>
5740             The <span><strong class="command">request-ixfr</strong></span> clause determines
5741             whether
5742             the local server, acting as a slave, will request incremental zone
5743             transfers from the given remote server, a master. If not set, the
5744             value of the <span><strong class="command">request-ixfr</strong></span> option in
5745             the view or
5746             global options block is used as a default.
5747           </p>
5748 <p>
5749             IXFR requests to servers that do not support IXFR will
5750             automatically
5751             fall back to AXFR.  Therefore, there is no need to manually list
5752             which servers support IXFR and which ones do not; the global
5753             default
5754             of <span><strong class="command">yes</strong></span> should always work.
5755             The purpose of the <span><strong class="command">provide-ixfr</strong></span> and
5756             <span><strong class="command">request-ixfr</strong></span> clauses is
5757             to make it possible to disable the use of IXFR even when both
5758             master
5759             and slave claim to support it, for example if one of the servers
5760             is buggy and crashes or corrupts data when IXFR is used.
5761           </p>
5762 <p>
5763             The <span><strong class="command">edns</strong></span> clause determines whether
5764             the local server will attempt to use EDNS when communicating
5765             with the remote server.  The default is <span><strong class="command">yes</strong></span>.
5766           </p>
5767 <p>
5768             The <span><strong class="command">edns-udp-size</strong></span> option sets the EDNS UDP size
5769             that is advertised by <span><strong class="command">named</strong></span> when querying the remote server.
5770             Valid values are 512 to 4096 bytes (values outside this range will be
5771             silently adjusted).  This option is useful when you wish to
5772             advertises a different value to this server than the value you
5773             advertise globally, for example, when there is a firewall at the
5774             remote site that is blocking large replies.
5775           </p>
5776 <p>
5777             The <span><strong class="command">max-udp-size</strong></span> option sets the
5778             maximum EDNS UDP message size <span><strong class="command">named</strong></span> will send.  Valid
5779             values are 512 to 4096 bytes (values outside this range will
5780             be silently adjusted).  This option is useful when you
5781             know that there is a firewall that is blocking large
5782             replies from <span><strong class="command">named</strong></span>.
5783           </p>
5784 <p>
5785             The server supports two zone transfer methods. The first, <span><strong class="command">one-answer</strong></span>,
5786             uses one DNS message per resource record transferred. <span><strong class="command">many-answers</strong></span> packs
5787             as many resource records as possible into a message. <span><strong class="command">many-answers</strong></span> is
5788             more efficient, but is only known to be understood by <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
5789             8.x, and patched versions of <acronym class="acronym">BIND</acronym>
5790             4.9.5. You can specify which method
5791             to use for a server with the <span><strong class="command">transfer-format</strong></span> option.
5792             If <span><strong class="command">transfer-format</strong></span> is not
5793             specified, the <span><strong class="command">transfer-format</strong></span>
5794             specified
5795             by the <span><strong class="command">options</strong></span> statement will be
5796             used.
5797           </p>
5798 <p><span><strong class="command">transfers</strong></span>
5799             is used to limit the number of concurrent inbound zone
5800             transfers from the specified server. If no
5801             <span><strong class="command">transfers</strong></span> clause is specified, the
5802             limit is set according to the
5803             <span><strong class="command">transfers-per-ns</strong></span> option.
5804           </p>
5805 <p>
5806             The <span><strong class="command">keys</strong></span> clause identifies a
5807             <span><strong class="command">key_id</strong></span> defined by the <span><strong class="command">key</strong></span> statement,
5808             to be used for transaction security (TSIG, <a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
5809             when talking to the remote server.
5810             When a request is sent to the remote server, a request signature
5811             will be generated using the key specified here and appended to the
5812             message. A request originating from the remote server is not
5813             required
5814             to be signed by this key.
5815           </p>
5816 <p>
5817             Although the grammar of the <span><strong class="command">keys</strong></span>
5818             clause
5819             allows for multiple keys, only a single key per server is
5820             currently
5821             supported.
5822           </p>
5823 <p>
5824             The <span><strong class="command">transfer-source</strong></span> and
5825             <span><strong class="command">transfer-source-v6</strong></span> clauses specify
5826             the IPv4 and IPv6 source
5827             address to be used for zone transfer with the remote server,
5828             respectively.
5829             For an IPv4 remote server, only <span><strong class="command">transfer-source</strong></span> can
5830             be specified.
5831             Similarly, for an IPv6 remote server, only
5832             <span><strong class="command">transfer-source-v6</strong></span> can be
5833             specified.
5834             For more details, see the description of
5835             <span><strong class="command">transfer-source</strong></span> and
5836             <span><strong class="command">transfer-source-v6</strong></span> in
5837             <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
5838           </p>
5839 <p>
5840             The <span><strong class="command">notify-source</strong></span> and
5841             <span><strong class="command">notify-source-v6</strong></span> clauses specify the
5842             IPv4 and IPv6 source address to be used for notify
5843             messages sent to remote servers, respectively.  For an
5844             IPv4 remote server, only <span><strong class="command">notify-source</strong></span>
5845             can be specified.  Similarly, for an IPv6 remote server,
5846             only <span><strong class="command">notify-source-v6</strong></span> can be specified.
5847           </p>
5848 <p>
5849             The <span><strong class="command">query-source</strong></span> and
5850             <span><strong class="command">query-source-v6</strong></span> clauses specify the
5851             IPv4 and IPv6 source address to be used for queries
5852             sent to remote servers, respectively.  For an IPv4
5853             remote server, only <span><strong class="command">query-source</strong></span> can
5854             be specified.  Similarly, for an IPv6 remote server,
5855             only <span><strong class="command">query-source-v6</strong></span> can be specified.
5856           </p>
5857 </div>
5858 <div class="sect2" lang="en">
5859 <div class="titlepage"><div><div><h3 class="title">
5860 <a name="statschannels"></a><span><strong class="command">statistics-channels</strong></span> Statement Grammar</h3></div></div></div>
5861 <pre class="programlisting"><span><strong class="command">statistics-channels</strong></span> {
5862    [ inet ( ip_addr | * ) [ port ip_port ]
5863    [ allow { <em class="replaceable"><code> address_match_list </code></em> } ]; ]
5864    [ inet ...; ]
5865 };
5866 </pre>
5867 </div>
5868 <div class="sect2" lang="en">
5869 <div class="titlepage"><div><div><h3 class="title">
5870 <a name="id2589395"></a><span><strong class="command">statistics-channels</strong></span> Statement Definition and
5871             Usage</h3></div></div></div>
5872 <p>
5873           The <span><strong class="command">statistics-channels</strong></span> statement
5874           declares communication channels to be used by system
5875           administrators to get access to statistics information of
5876           the name server.
5877         </p>
5878 <p>
5879           This statement intends to be flexible to support multiple
5880           communication protocols in the future, but currently only
5881           HTTP access is supported.
5882           It requires that BIND 9 be compiled with libxml2;
5883           the <span><strong class="command">statistics-channels</strong></span> statement is
5884           still accepted even if it is built without the library,
5885           but any HTTP access will fail with an error.
5886         </p>
5887 <p>
5888           An <span><strong class="command">inet</strong></span> control channel is a TCP socket
5889           listening at the specified <span><strong class="command">ip_port</strong></span> on the
5890           specified <span><strong class="command">ip_addr</strong></span>, which can be an IPv4 or IPv6
5891           address.  An <span><strong class="command">ip_addr</strong></span> of <code class="literal">*</code> (asterisk) is
5892           interpreted as the IPv4 wildcard address; connections will be
5893           accepted on any of the system's IPv4 addresses.
5894           To listen on the IPv6 wildcard address,
5895           use an <span><strong class="command">ip_addr</strong></span> of <code class="literal">::</code>.
5896         </p>
5897 <p>
5898           If no port is specified, port 80 is used for HTTP channels.
5899           The asterisk "<code class="literal">*</code>" cannot be used for
5900           <span><strong class="command">ip_port</strong></span>.
5901         </p>
5902 <p>
5903           The attempt of opening a statistics channel is
5904           restricted by the optional <span><strong class="command">allow</strong></span> clause.
5905           Connections to the statistics channel are permitted based on the
5906           <span><strong class="command">address_match_list</strong></span>.
5907           If no <span><strong class="command">allow</strong></span> clause is present,
5908           <span><strong class="command">named</strong></span> accepts connection
5909           attempts from any address; since the statistics may
5910           contain sensitive internal information, it is highly
5911           recommended to restrict the source of connection requests
5912           appropriately.
5913         </p>
5914 <p>
5915           If no <span><strong class="command">statistics-channels</strong></span> statement is present,
5916           <span><strong class="command">named</strong></span> will not open any communication channels.
5917         </p>
5918 </div>
5919 <div class="sect2" lang="en">
5920 <div class="titlepage"><div><div><h3 class="title">
5921 <a name="trusted-keys"></a><span><strong class="command">trusted-keys</strong></span> Statement Grammar</h3></div></div></div>
5922 <pre class="programlisting"><span><strong class="command">trusted-keys</strong></span> {
5923     <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> ;
5924     [<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>]
5925 };
5926 </pre>
5927 </div>
5928 <div class="sect2" lang="en">
5929 <div class="titlepage"><div><div><h3 class="title">
5930 <a name="id2589534"></a><span><strong class="command">trusted-keys</strong></span> Statement Definition
5931             and Usage</h3></div></div></div>
5932 <p>
5933             The <span><strong class="command">trusted-keys</strong></span> statement defines
5934             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
5935             public key for a non-authoritative zone is known, but
5936             cannot be securely obtained through DNS, either because
5937             it is the DNS root zone or because its parent zone is
5938             unsigned.  Once a key has been configured as a trusted
5939             key, it is treated as if it had been validated and
5940             proven secure. The resolver attempts DNSSEC validation
5941             on all DNS data in subdomains of a security root.
5942           </p>
5943 <p>
5944             All keys (and corresponding zones) listed in
5945             <span><strong class="command">trusted-keys</strong></span> are deemed to exist regardless
5946             of what parent zones say.  Similarly for all keys listed in
5947             <span><strong class="command">trusted-keys</strong></span> only those keys are
5948             used to validate the DNSKEY RRset.  The parent's DS RRset
5949             will not be used.
5950           </p>
5951 <p>
5952             The <span><strong class="command">trusted-keys</strong></span> statement can contain
5953             multiple key entries, each consisting of the key's
5954             domain name, flags, protocol, algorithm, and the Base-64
5955             representation of the key data.
5956             Spaces, tabs, newlines and carriage returns are ignored
5957             in the key data, so the configuration may be split up into
5958             multiple lines.
5959           </p>
5960 <p>
5961             <span><strong class="command">trusted-keys</strong></span> may be set at the top level
5962             of <code class="filename">named.conf</code> or within a view.  If it is
5963             set in both places, they are additive: keys defined at the top
5964             level are inherited by all views, but keys defined in a view
5965             are only used within that view.
5966           </p>
5967 </div>
5968 <div class="sect2" lang="en">
5969 <div class="titlepage"><div><div><h3 class="title">
5970 <a name="id2589581"></a><span><strong class="command">managed-keys</strong></span> Statement Grammar</h3></div></div></div>
5971 <pre class="programlisting"><span><strong class="command">managed-keys</strong></span> {
5972     <em class="replaceable"><code>string</code></em> initial-key <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> ;
5973     [<span class="optional"> <em class="replaceable"><code>string</code></em> initial-key <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>]
5974 };
5975 </pre>
5976 </div>
5977 <div class="sect2" lang="en">
5978 <div class="titlepage"><div><div><h3 class="title">
5979 <a name="managed-keys"></a><span><strong class="command">managed-keys</strong></span> Statement Definition
5980             and Usage</h3></div></div></div>
5981 <p>
5982             The <span><strong class="command">managed-keys</strong></span> statement, like
5983             <span><strong class="command">trusted-keys</strong></span>, defines DNSSEC
5984             security roots.  The difference is that
5985             <span><strong class="command">managed-keys</strong></span> can be kept up to date
5986             automatically, without intervention from the resolver
5987             operator.
5988           </p>
5989 <p>
5990             Suppose, for example, that a zone's key-signing
5991             key was compromised, and the zone owner had to revoke and
5992             replace the key.  A resolver which had the old key in a
5993             <span><strong class="command">trusted-keys</strong></span> statement would be
5994             unable to validate this zone any longer; it would
5995             reply with a SERVFAIL response code.  This would
5996             continue until the resolver operator had updated the
5997             <span><strong class="command">trusted-keys</strong></span> statement with the new key.
5998           </p>
5999 <p>
6000             If, however, the zone were listed in a
6001             <span><strong class="command">managed-keys</strong></span> statement instead, then the
6002             zone owner could add a "stand-by" key to the zone in advance.
6003             <span><strong class="command">named</strong></span> would store the stand-by key, and
6004             when the original key was revoked, <span><strong class="command">named</strong></span>
6005             would be able to transition smoothly to the new key.  It would
6006             also recognize that the old key had been revoked, and cease
6007             using that key to validate answers, minimizing the damage that
6008             the compromised key could do.
6009           </p>
6010 <p>
6011             A <span><strong class="command">managed-keys</strong></span> statement contains a list of
6012             the keys to be managed, along with information about how the
6013             keys are to be initialized for the first time.  The only
6014             initialization method currently supported (as of
6015             <acronym class="acronym">BIND</acronym> 9.7.0) is <code class="literal">initial-key</code>.
6016             This means the <span><strong class="command">managed-keys</strong></span> statement must
6017             contain a copy of the initializing key.  (Future releases may
6018             allow keys to be initialized by other methods, eliminating this
6019             requirement.)
6020           </p>
6021 <p>
6022             Consequently, a <span><strong class="command">managed-keys</strong></span> statement
6023             appears similar to a <span><strong class="command">trusted-keys</strong></span>, differing
6024             in the presence of the second field, containing the keyword
6025             <code class="literal">initial-key</code>.  The difference is, whereas the
6026             keys listed in a <span><strong class="command">trusted-keys</strong></span> continue to be
6027             trusted until they are removed from
6028             <code class="filename">named.conf</code>, an initializing key listed
6029             in a <span><strong class="command">managed-keys</strong></span> statement is only trusted
6030             <span class="emphasis"><em>once</em></span>: for as long as it takes to load the
6031             managed key database and start the RFC 5011 key maintenance
6032             process.
6033           </p>
6034 <p>
6035             The first time <span><strong class="command">named</strong></span> runs with a managed key
6036             configured in <code class="filename">named.conf</code>, it fetches the
6037             DNSKEY RRset directly from the zone apex, and validates it
6038             using the key specified in the <span><strong class="command">managed-keys</strong></span>
6039             statement.  If the DNSKEY RRset is validly signed, then it is
6040             used as the basis for a new managed keys database.
6041           </p>
6042 <p>
6043             From that point on, whenever <span><strong class="command">named</strong></span> runs, it
6044             sees the <span><strong class="command">managed-keys</strong></span> statement, checks to
6045             make sure RFC 5011 key maintenance has already been initialized
6046             for the specified domain, and if so, it simply moves on.  The
6047             key specified in the <span><strong class="command">managed-keys</strong></span> is not
6048             used to validate answers; it has been superseded by the key or
6049             keys stored in the managed keys database.
6050           </p>
6051 <p>
6052             The next time <span><strong class="command">named</strong></span> runs after a name
6053             has been <span class="emphasis"><em>removed</em></span> from the
6054             <span><strong class="command">managed-keys</strong></span> statement, the corresponding
6055             zone will be removed from the managed keys database,
6056             and RFC 5011 key maintenance will no longer be used for that
6057             domain.
6058           </p>
6059 <p>
6060             <span><strong class="command">named</strong></span> only maintains a single managed keys
6061             database; consequently, unlike <span><strong class="command">trusted-keys</strong></span>,
6062             <span><strong class="command">managed-keys</strong></span> may only be set at the top
6063             level of <code class="filename">named.conf</code>, not within a view.
6064           </p>
6065 <p>
6066             In the current implementation, the managed keys database is
6067             stored as a master-format zone file called
6068             <code class="filename">managed-keys.bind</code>.  When the key database
6069             is changed, the zone is updated.  As with any other dynamic
6070             zone, changes will be written into a journal file,
6071             <code class="filename">managed-keys.bind.jnl</code>.  They are committed
6072             to the master file as soon as possible afterward; in the case
6073             of the managed key database, this will usually occur within 30
6074             seconds.  So, whenever <span><strong class="command">named</strong></span> is using
6075             automatic key maintenance, those two files can be expected to
6076             exist in the working directory.  (For this reason among others,
6077             the working directory should be always be writable by
6078             <span><strong class="command">named</strong></span>.)
6079           </p>
6080 <p>
6081             If the <span><strong class="command">dnssec-lookaside</strong></span> option is
6082             set to <strong class="userinput"><code>auto</code></strong>, <span><strong class="command">named</strong></span>
6083             will automatically initialize a managed key for the
6084             zone <code class="literal">dlv.isc.org</code>.  The key that is
6085             used to initialize the key maintenance process is built
6086             into <span><strong class="command">named</strong></span>, and can be overridden
6087             from <span><strong class="command">bindkeys-file</strong></span>.
6088           </p>
6089 </div>
6090 <div class="sect2" lang="en">
6091 <div class="titlepage"><div><div><h3 class="title">
6092 <a name="view_statement_grammar"></a><span><strong class="command">view</strong></span> Statement Grammar</h3></div></div></div>
6093 <pre class="programlisting"><span><strong class="command">view</strong></span> <em class="replaceable"><code>view_name</code></em>
6094       [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6095       match-clients { <em class="replaceable"><code>address_match_list</code></em> };
6096       match-destinations { <em class="replaceable"><code>address_match_list</code></em> };
6097       match-recursive-only <em class="replaceable"><code>yes_or_no</code></em> ;
6098       [<span class="optional"> <em class="replaceable"><code>view_option</code></em>; ...</span>]
6099       [<span class="optional"> <em class="replaceable"><code>zone_statement</code></em>; ...</span>]
6100 };
6101 </pre>
6102 </div>
6103 <div class="sect2" lang="en">
6104 <div class="titlepage"><div><div><h3 class="title">
6105 <a name="id2590007"></a><span><strong class="command">view</strong></span> Statement Definition and Usage</h3></div></div></div>
6106 <p>
6107             The <span><strong class="command">view</strong></span> statement is a powerful
6108             feature
6109             of <acronym class="acronym">BIND</acronym> 9 that lets a name server
6110             answer a DNS query differently
6111             depending on who is asking. It is particularly useful for
6112             implementing
6113             split DNS setups without having to run multiple servers.
6114           </p>
6115 <p>
6116             Each <span><strong class="command">view</strong></span> statement defines a view
6117             of the
6118             DNS namespace that will be seen by a subset of clients.  A client
6119             matches
6120             a view if its source IP address matches the
6121             <code class="varname">address_match_list</code> of the view's
6122             <span><strong class="command">match-clients</strong></span> clause and its
6123             destination IP address matches
6124             the <code class="varname">address_match_list</code> of the
6125             view's
6126             <span><strong class="command">match-destinations</strong></span> clause.  If not
6127             specified, both
6128             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
6129             default to matching all addresses.  In addition to checking IP
6130             addresses
6131             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
6132             can also take <span><strong class="command">keys</strong></span> which provide an
6133             mechanism for the
6134             client to select the view.  A view can also be specified
6135             as <span><strong class="command">match-recursive-only</strong></span>, which
6136             means that only recursive
6137             requests from matching clients will match that view.
6138             The order of the <span><strong class="command">view</strong></span> statements is
6139             significant &#8212;
6140             a client request will be resolved in the context of the first
6141             <span><strong class="command">view</strong></span> that it matches.
6142           </p>
6143 <p>
6144             Zones defined within a <span><strong class="command">view</strong></span>
6145             statement will
6146             only be accessible to clients that match the <span><strong class="command">view</strong></span>.
6147             By defining a zone of the same name in multiple views, different
6148             zone data can be given to different clients, for example,
6149             "internal"
6150             and "external" clients in a split DNS setup.
6151           </p>
6152 <p>
6153             Many of the options given in the <span><strong class="command">options</strong></span> statement
6154             can also be used within a <span><strong class="command">view</strong></span>
6155             statement, and then
6156             apply only when resolving queries with that view.  When no
6157             view-specific
6158             value is given, the value in the <span><strong class="command">options</strong></span> statement
6159             is used as a default.  Also, zone options can have default values
6160             specified
6161             in the <span><strong class="command">view</strong></span> statement; these
6162             view-specific defaults
6163             take precedence over those in the <span><strong class="command">options</strong></span> statement.
6164           </p>
6165 <p>
6166             Views are class specific.  If no class is given, class IN
6167             is assumed.  Note that all non-IN views must contain a hint zone,
6168             since only the IN class has compiled-in default hints.
6169           </p>
6170 <p>
6171             If there are no <span><strong class="command">view</strong></span> statements in
6172             the config
6173             file, a default view that matches any client is automatically
6174             created
6175             in class IN. Any <span><strong class="command">zone</strong></span> statements
6176             specified on
6177             the top level of the configuration file are considered to be part
6178             of
6179             this default view, and the <span><strong class="command">options</strong></span>
6180             statement will
6181             apply to the default view. If any explicit <span><strong class="command">view</strong></span>
6182             statements are present, all <span><strong class="command">zone</strong></span>
6183             statements must
6184             occur inside <span><strong class="command">view</strong></span> statements.
6185           </p>
6186 <p>
6187             Here is an example of a typical split DNS setup implemented
6188             using <span><strong class="command">view</strong></span> statements:
6189           </p>
6190 <pre class="programlisting">view "internal" {
6191       // This should match our internal networks.
6192       match-clients { 10.0.0.0/8; };
6193
6194       // Provide recursive service to internal
6195       // clients only.
6196       recursion yes;
6197
6198       // Provide a complete view of the example.com
6199       // zone including addresses of internal hosts.
6200       zone "example.com" {
6201             type master;
6202             file "example-internal.db";
6203       };
6204 };
6205
6206 view "external" {
6207       // Match all clients not matched by the
6208       // previous view.
6209       match-clients { any; };
6210
6211       // Refuse recursive service to external clients.
6212       recursion no;
6213
6214       // Provide a restricted view of the example.com
6215       // zone containing only publicly accessible hosts.
6216       zone "example.com" {
6217            type master;
6218            file "example-external.db";
6219       };
6220 };
6221 </pre>
6222 </div>
6223 <div class="sect2" lang="en">
6224 <div class="titlepage"><div><div><h3 class="title">
6225 <a name="zone_statement_grammar"></a><span><strong class="command">zone</strong></span>
6226             Statement Grammar</h3></div></div></div>
6227 <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>] {
6228     type master;
6229     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6230     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6231     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6232     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6233     [<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>]
6234     [<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>] ;
6235                   [<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>]
6236     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
6237     [<span class="optional"> check-mx (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
6238     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6239     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6240     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
6241     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
6242     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
6243     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
6244     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
6245     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
6246     [<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>]
6247     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
6248     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6249     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
6250     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6251     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
6252     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
6253     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
6254     [<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>]
6255     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
6256     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6257     [<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>]
6258     [<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>]
6259     [<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>]
6260     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6261     [<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>]
6262     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
6263     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
6264     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
6265     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
6266     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
6267     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
6268     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
6269     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
6270     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
6271     [<span class="optional"> auto-dnssec <code class="constant">allow</code>|<code class="constant">maintain</code>|<code class="constant">off</code>; </span>]
6272     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6273 };
6274
6275 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6276     type slave;
6277     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6278     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6279     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6280     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6281     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6282     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6283     [<span class="optional"> dnssec-update-mode ( <em class="replaceable"><code>maintain</code></em> | <em class="replaceable"><code>no-resign</code></em> ); </span>]
6284     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6285     [<span class="optional"> dnssec-secure-to-insecure <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6286     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6287     [<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>] ;
6288                   [<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>]
6289     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
6290     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
6291     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
6292     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
6293     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
6294     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
6295     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
6296     [<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>]
6297     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
6298     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6299     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
6300     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6301     [<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>
6302                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
6303                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
6304     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
6305     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
6306     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
6307     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
6308     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
6309     [<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>]
6310     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
6311     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6312     [<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>]
6313     [<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>]
6314     [<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>]
6315     [<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>]
6316     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
6317                              [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6318     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6319     [<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>]
6320     [<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>]
6321     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6322     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
6323     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
6324     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
6325     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
6326     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
6327     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6328     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6329 };
6330
6331 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6332     type hint;
6333     file <em class="replaceable"><code>string</code></em> ;
6334     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6335     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>] // Not Implemented.
6336 };
6337
6338 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6339     type stub;
6340     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6341     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6342     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
6343     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
6344     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6345     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
6346     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
6347     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
6348     [<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>]
6349     [<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>
6350                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
6351                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
6352     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
6353     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
6354     [<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>]
6355     [<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>]
6356     [<span class="optional"> transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
6357                          [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6358     [<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>]
6359     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
6360                             [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6361     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6362     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6363     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
6364     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
6365     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
6366     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
6367     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
6368     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6369 };
6370
6371 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6372     type static-stub;
6373     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6374     [<span class="optional"> server-addresses { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> ; ... </span>] }; </span>]
6375     [<span class="optional"> server-names { [<span class="optional"> <em class="replaceable"><code>namelist</code></em> </span>] }; </span>]
6376     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6377 };
6378
6379 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6380     type forward;
6381     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
6382     [<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>]
6383     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6384 };
6385
6386 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6387     type delegation-only;
6388 };
6389
6390 </pre>
6391 </div>
6392 <div class="sect2" lang="en">
6393 <div class="titlepage"><div><div><h3 class="title">
6394 <a name="id2591558"></a><span><strong class="command">zone</strong></span> Statement Definition and Usage</h3></div></div></div>
6395 <div class="sect3" lang="en">
6396 <div class="titlepage"><div><div><h4 class="title">
6397 <a name="id2591565"></a>Zone Types</h4></div></div></div>
6398 <div class="informaltable"><table border="1">
6399 <colgroup>
6400 <col>
6401 <col>
6402 </colgroup>
6403 <tbody>
6404 <tr>
6405 <td>
6406                       <p>
6407                         <code class="varname">master</code>
6408                       </p>
6409                     </td>
6410 <td>
6411                       <p>
6412                         The server has a master copy of the data
6413                         for the zone and will be able to provide authoritative
6414                         answers for
6415                         it.
6416                       </p>
6417                     </td>
6418 </tr>
6419 <tr>
6420 <td>
6421                       <p>
6422                         <code class="varname">slave</code>
6423                       </p>
6424                     </td>
6425 <td>
6426                       <p>
6427                         A slave zone is a replica of a master
6428                         zone. The <span><strong class="command">masters</strong></span> list
6429                         specifies one or more IP addresses
6430                         of master servers that the slave contacts to update
6431                         its copy of the zone.
6432                         Masters list elements can also be names of other
6433                         masters lists.
6434                         By default, transfers are made from port 53 on the
6435                         servers; this can
6436                         be changed for all servers by specifying a port number
6437                         before the
6438                         list of IP addresses, or on a per-server basis after
6439                         the IP address.
6440                         Authentication to the master can also be done with
6441                         per-server TSIG keys.
6442                         If a file is specified, then the
6443                         replica will be written to this file whenever the zone
6444                         is changed,
6445                         and reloaded from this file on a server restart. Use
6446                         of a file is
6447                         recommended, since it often speeds server startup and
6448                         eliminates
6449                         a needless waste of bandwidth. Note that for large
6450                         numbers (in the
6451                         tens or hundreds of thousands) of zones per server, it
6452                         is best to
6453                         use a two-level naming scheme for zone filenames. For
6454                         example,
6455                         a slave server for the zone <code class="literal">example.com</code> might place
6456                         the zone contents into a file called
6457                         <code class="filename">ex/example.com</code> where <code class="filename">ex/</code> is
6458                         just the first two letters of the zone name. (Most
6459                         operating systems
6460                         behave very slowly if you put 100000 files into
6461                         a single directory.)
6462                       </p>
6463                     </td>
6464 </tr>
6465 <tr>
6466 <td>
6467                       <p>
6468                         <code class="varname">stub</code>
6469                       </p>
6470                     </td>
6471 <td>
6472                       <p>
6473                         A stub zone is similar to a slave zone,
6474                         except that it replicates only the NS records of a
6475                         master zone instead
6476                         of the entire zone. Stub zones are not a standard part
6477                         of the DNS;
6478                         they are a feature specific to the <acronym class="acronym">BIND</acronym> implementation.
6479                       </p>
6480
6481                       <p>
6482                         Stub zones can be used to eliminate the need for glue
6483                         NS record
6484                         in a parent zone at the expense of maintaining a stub
6485                         zone entry and
6486                         a set of name server addresses in <code class="filename">named.conf</code>.
6487                         This usage is not recommended for new configurations,
6488                         and BIND 9
6489                         supports it only in a limited way.
6490                         In <acronym class="acronym">BIND</acronym> 4/8, zone
6491                         transfers of a parent zone
6492                         included the NS records from stub children of that
6493                         zone. This meant
6494                         that, in some cases, users could get away with
6495                         configuring child stubs
6496                         only in the master server for the parent zone. <acronym class="acronym">BIND</acronym>
6497                         9 never mixes together zone data from different zones
6498                         in this
6499                         way. Therefore, if a <acronym class="acronym">BIND</acronym> 9 master serving a parent
6500                         zone has child stub zones configured, all the slave
6501                         servers for the
6502                         parent zone also need to have the same child stub
6503                         zones
6504                         configured.
6505                       </p>
6506
6507                       <p>
6508                         Stub zones can also be used as a way of forcing the
6509                         resolution
6510                         of a given domain to use a particular set of
6511                         authoritative servers.
6512                         For example, the caching name servers on a private
6513                         network using
6514                         RFC1918 addressing may be configured with stub zones
6515                         for
6516                         <code class="literal">10.in-addr.arpa</code>
6517                         to use a set of internal name servers as the
6518                         authoritative
6519                         servers for that domain.
6520                       </p>
6521                     </td>
6522 </tr>
6523 <tr>
6524 <td>
6525                       <p>
6526                         <code class="varname">static-stub</code>
6527                       </p>
6528                     </td>
6529 <td>
6530                       <p>
6531                         A static-stub zone is similar to a stub zone
6532                         with the following exceptions:
6533                         the zone data is statically configured, rather
6534                         than transferred from a master server;
6535                         when recursion is necessary for a query that
6536                         matches a static-stub zone, the locally
6537                         configured data (nameserver names and glue addresses)
6538                         is always used even if different authoritative
6539                         information is cached.
6540                       </p>
6541                       <p>
6542                         Zone data is configured via the
6543                         <span><strong class="command">server-addresses</strong></span> and
6544                         <span><strong class="command">server-names</strong></span> zone options.
6545                       </p>
6546                       <p>
6547                         The zone data is maintained in the form of NS
6548                         and (if necessary) glue A or AAAA RRs
6549                         internally, which can be seen by dumping zone
6550                         databases by <span><strong class="command">rndc dumpdb -all</strong></span>.
6551                         The configured RRs are considered local configuration
6552                         parameters rather than public data.
6553                         Non recursive queries (i.e., those with the RD
6554                         bit off) to a static-stub zone are therefore
6555                         prohibited and will be responded with REFUSED.
6556                       </p>
6557                       <p>
6558                         Since the data is statically configured, no
6559                         zone maintenance action takes place for a static-stub
6560                         zone.
6561                         For example, there is no periodic refresh
6562                         attempt, and an incoming notify message
6563                         will be rejected with an rcode of NOTAUTH.
6564                       </p>
6565                       <p>
6566                         Each static-stub zone is configured with
6567                         internally generated NS and (if necessary)
6568                         glue A or AAAA RRs
6569                       </p>
6570                     </td>
6571 </tr>
6572 <tr>
6573 <td>
6574                       <p>
6575                         <code class="varname">forward</code>
6576                       </p>
6577                     </td>
6578 <td>
6579                       <p>
6580                         A "forward zone" is a way to configure
6581                         forwarding on a per-domain basis.  A <span><strong class="command">zone</strong></span> statement
6582                         of type <span><strong class="command">forward</strong></span> can
6583                         contain a <span><strong class="command">forward</strong></span>
6584                         and/or <span><strong class="command">forwarders</strong></span>
6585                         statement,
6586                         which will apply to queries within the domain given by
6587                         the zone
6588                         name. If no <span><strong class="command">forwarders</strong></span>
6589                         statement is present or
6590                         an empty list for <span><strong class="command">forwarders</strong></span> is given, then no
6591                         forwarding will be done for the domain, canceling the
6592                         effects of
6593                         any forwarders in the <span><strong class="command">options</strong></span> statement. Thus
6594                         if you want to use this type of zone to change the
6595                         behavior of the
6596                         global <span><strong class="command">forward</strong></span> option
6597                         (that is, "forward first"
6598                         to, then "forward only", or vice versa, but want to
6599                         use the same
6600                         servers as set globally) you need to re-specify the
6601                         global forwarders.
6602                       </p>
6603                     </td>
6604 </tr>
6605 <tr>
6606 <td>
6607                       <p>
6608                         <code class="varname">hint</code>
6609                       </p>
6610                     </td>
6611 <td>
6612                       <p>
6613                         The initial set of root name servers is
6614                         specified using a "hint zone". When the server starts
6615                         up, it uses
6616                         the root hints to find a root name server and get the
6617                         most recent
6618                         list of root name servers. If no hint zone is
6619                         specified for class
6620                         IN, the server uses a compiled-in default set of root
6621                         servers hints.
6622                         Classes other than IN have no built-in defaults hints.
6623                       </p>
6624                     </td>
6625 </tr>
6626 <tr>
6627 <td>
6628                       <p>
6629                         <code class="varname">delegation-only</code>
6630                       </p>
6631                     </td>
6632 <td>
6633                       <p>
6634                         This is used to enforce the delegation-only
6635                         status of infrastructure zones (e.g. COM,
6636                         NET, ORG).  Any answer that is received
6637                         without an explicit or implicit delegation
6638                         in the authority section will be treated
6639                         as NXDOMAIN.  This does not apply to the
6640                         zone apex.  This should not be applied to
6641                         leaf zones.
6642                       </p>
6643                       <p>
6644                         <code class="varname">delegation-only</code> has no
6645                         effect on answers received from forwarders.
6646                       </p>
6647                       <p>
6648                         See caveats in <a href="Bv9ARM.ch06.html#root_delegation_only"><span><strong class="command">root-delegation-only</strong></span></a>.
6649                       </p>
6650                     </td>
6651 </tr>
6652 </tbody>
6653 </table></div>
6654 </div>
6655 <div class="sect3" lang="en">
6656 <div class="titlepage"><div><div><h4 class="title">
6657 <a name="id2592179"></a>Class</h4></div></div></div>
6658 <p>
6659               The zone's name may optionally be followed by a class. If
6660               a class is not specified, class <code class="literal">IN</code> (for <code class="varname">Internet</code>),
6661               is assumed. This is correct for the vast majority of cases.
6662             </p>
6663 <p>
6664               The <code class="literal">hesiod</code> class is
6665               named for an information service from MIT's Project Athena. It
6666               is
6667               used to share information about various systems databases, such
6668               as users, groups, printers and so on. The keyword
6669               <code class="literal">HS</code> is
6670               a synonym for hesiod.
6671             </p>
6672 <p>
6673               Another MIT development is Chaosnet, a LAN protocol created
6674               in the mid-1970s. Zone data for it can be specified with the <code class="literal">CHAOS</code> class.
6675             </p>
6676 </div>
6677 <div class="sect3" lang="en">
6678 <div class="titlepage"><div><div><h4 class="title">
6679 <a name="id2592212"></a>Zone Options</h4></div></div></div>
6680 <div class="variablelist"><dl>
6681 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
6682 <dd><p>
6683                     See the description of
6684                     <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>.
6685                   </p></dd>
6686 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
6687 <dd><p>
6688                     See the description of
6689                     <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>.
6690                   </p></dd>
6691 <dt><span class="term"><span><strong class="command">allow-query-on</strong></span></span></dt>
6692 <dd><p>
6693                     See the description of
6694                     <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>.
6695                   </p></dd>
6696 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
6697 <dd><p>
6698                     See the description of <span><strong class="command">allow-transfer</strong></span>
6699                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
6700                   </p></dd>
6701 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
6702 <dd><p>
6703                     See the description of <span><strong class="command">allow-update</strong></span>
6704                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
6705                   </p></dd>
6706 <dt><span class="term"><span><strong class="command">update-policy</strong></span></span></dt>
6707 <dd><p>
6708                     Specifies a "Simple Secure Update" policy. See
6709                     <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>.
6710                   </p></dd>
6711 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
6712 <dd><p>
6713                     See the description of <span><strong class="command">allow-update-forwarding</strong></span>
6714                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
6715                   </p></dd>
6716 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
6717 <dd><p>
6718                     Only meaningful if <span><strong class="command">notify</strong></span>
6719                     is
6720                     active for this zone. The set of machines that will
6721                     receive a
6722                     <code class="literal">DNS NOTIFY</code> message
6723                     for this zone is made up of all the listed name servers
6724                     (other than
6725                     the primary master) for the zone plus any IP addresses
6726                     specified
6727                     with <span><strong class="command">also-notify</strong></span>. A port
6728                     may be specified
6729                     with each <span><strong class="command">also-notify</strong></span>
6730                     address to send the notify
6731                     messages to a port other than the default of 53.
6732                     <span><strong class="command">also-notify</strong></span> is not
6733                     meaningful for stub zones.
6734                     The default is the empty list.
6735                   </p></dd>
6736 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
6737 <dd><p>
6738                     This option is used to restrict the character set and
6739                     syntax of
6740                     certain domain names in master files and/or DNS responses
6741                     received from the
6742                     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>
6743                     zones the default is <span><strong class="command">warn</strong></span>.
6744                     It is not implemented for <span><strong class="command">hint</strong></span> zones.
6745                   </p></dd>
6746 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
6747 <dd><p>
6748                     See the description of
6749                     <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>.
6750                   </p></dd>
6751 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
6752 <dd><p>
6753                     See the description of
6754                     <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>.
6755                   </p></dd>
6756 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
6757 <dd><p>
6758                     See the description of
6759                     <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>.
6760                   </p></dd>
6761 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
6762 <dd><p>
6763                     See the description of
6764                     <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>.
6765                   </p></dd>
6766 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
6767 <dd><p>
6768                     See the description of
6769                     <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>.
6770                   </p></dd>
6771 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
6772 <dd><p>
6773                     See the description of
6774                     <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>.
6775                   </p></dd>
6776 <dt><span class="term"><span><strong class="command">dnssec-dnskey-kskonly</strong></span></span></dt>
6777 <dd><p>
6778                     See the description of
6779                     <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>.
6780                   </p></dd>
6781 <dt><span class="term"><span><strong class="command">try-tcp-refresh</strong></span></span></dt>
6782 <dd><p>
6783                     See the description of
6784                     <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>.
6785                   </p></dd>
6786 <dt><span class="term"><span><strong class="command">database</strong></span></span></dt>
6787 <dd>
6788 <p>
6789                     Specify the type of database to be used for storing the
6790                     zone data.  The string following the <span><strong class="command">database</strong></span> keyword
6791                     is interpreted as a list of whitespace-delimited words.
6792                     The first word
6793                     identifies the database type, and any subsequent words are
6794                     passed
6795                     as arguments to the database to be interpreted in a way
6796                     specific
6797                     to the database type.
6798                   </p>
6799 <p>
6800                     The default is <strong class="userinput"><code>"rbt"</code></strong>, BIND 9's
6801                     native in-memory
6802                     red-black-tree database.  This database does not take
6803                     arguments.
6804                   </p>
6805 <p>
6806                     Other values are possible if additional database drivers
6807                     have been linked into the server.  Some sample drivers are
6808                     included
6809                     with the distribution but none are linked in by default.
6810                   </p>
6811 </dd>
6812 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
6813 <dd><p>
6814                     See the description of
6815                     <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>.
6816                   </p></dd>
6817 <dt><span class="term"><span><strong class="command">delegation-only</strong></span></span></dt>
6818 <dd>
6819 <p>
6820                     The flag only applies to hint and stub zones.  If set
6821                     to <strong class="userinput"><code>yes</code></strong>, then the zone will also be
6822                     treated as if it is also a delegation-only type zone.
6823                   </p>
6824 <p>
6825                     See caveats in <a href="Bv9ARM.ch06.html#root_delegation_only"><span><strong class="command">root-delegation-only</strong></span></a>.
6826                   </p>
6827 </dd>
6828 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
6829 <dd><p>
6830                     Only meaningful if the zone has a forwarders
6831                     list. The <span><strong class="command">only</strong></span> value causes
6832                     the lookup to fail
6833                     after trying the forwarders and getting no answer, while <span><strong class="command">first</strong></span> would
6834                     allow a normal lookup to be tried.
6835                   </p></dd>
6836 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
6837 <dd><p>
6838                     Used to override the list of global forwarders.
6839                     If it is not specified in a zone of type <span><strong class="command">forward</strong></span>,
6840                     no forwarding is done for the zone and the global options are
6841                     not used.
6842                   </p></dd>
6843 <dt><span class="term"><span><strong class="command">ixfr-base</strong></span></span></dt>
6844 <dd><p>
6845                     Was used in <acronym class="acronym">BIND</acronym> 8 to
6846                     specify the name
6847                     of the transaction log (journal) file for dynamic update
6848                     and IXFR.
6849                     <acronym class="acronym">BIND</acronym> 9 ignores the option
6850                     and constructs the name of the journal
6851                     file by appending "<code class="filename">.jnl</code>"
6852                     to the name of the
6853                     zone file.
6854                   </p></dd>
6855 <dt><span class="term"><span><strong class="command">ixfr-tmp-file</strong></span></span></dt>
6856 <dd><p>
6857                     Was an undocumented option in <acronym class="acronym">BIND</acronym> 8.
6858                     Ignored in <acronym class="acronym">BIND</acronym> 9.
6859                   </p></dd>
6860 <dt><span class="term"><span><strong class="command">journal</strong></span></span></dt>
6861 <dd><p>
6862                     Allow the default journal's filename to be overridden.
6863                     The default is the zone's filename with "<code class="filename">.jnl</code>" appended.
6864                     This is applicable to <span><strong class="command">master</strong></span> and <span><strong class="command">slave</strong></span> zones.
6865                   </p></dd>
6866 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
6867 <dd><p>
6868                     See the description of
6869                     <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>.
6870                   </p></dd>
6871 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
6872 <dd><p>
6873                     See the description of
6874                     <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>.
6875                   </p></dd>
6876 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
6877 <dd><p>
6878                     See the description of
6879                     <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>.
6880                   </p></dd>
6881 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
6882 <dd><p>
6883                     See the description of
6884                     <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>.
6885                   </p></dd>
6886 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
6887 <dd><p>
6888                     See the description of
6889                     <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>.
6890                   </p></dd>
6891 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
6892 <dd><p>
6893                     See the description of
6894                     <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>.
6895                   </p></dd>
6896 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
6897 <dd><p>
6898                     See the description of
6899                     <span><strong class="command">notify-delay</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
6900                   </p></dd>
6901 <dt><span class="term"><span><strong class="command">notify-to-soa</strong></span></span></dt>
6902 <dd><p>
6903                     See the description of
6904                     <span><strong class="command">notify-to-soa</strong></span> in
6905                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
6906                   </p></dd>
6907 <dt><span class="term"><span><strong class="command">pubkey</strong></span></span></dt>
6908 <dd><p>
6909                     In <acronym class="acronym">BIND</acronym> 8, this option was
6910                     intended for specifying
6911                     a public zone key for verification of signatures in DNSSEC
6912                     signed
6913                     zones when they are loaded from disk. <acronym class="acronym">BIND</acronym> 9 does not verify signatures
6914                     on load and ignores the option.
6915                   </p></dd>
6916 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
6917 <dd><p>
6918                     If <strong class="userinput"><code>yes</code></strong>, the server will keep
6919                     statistical
6920                     information for this zone, which can be dumped to the
6921                     <span><strong class="command">statistics-file</strong></span> defined in
6922                     the server options.
6923                   </p></dd>
6924 <dt><span class="term"><span><strong class="command">server-addresses</strong></span></span></dt>
6925 <dd>
6926 <p>
6927                     Only meaningful for static-stub zones.
6928                     This is a list of IP addresses to which queries
6929                     should be sent in recursive resolution for the
6930                     zone.
6931                     A non empty list for this option will internally
6932                     configure the apex NS RR with associated glue A or
6933                     AAAA RRs.
6934                   </p>
6935 <p>
6936                     For example, if "example.com" is configured as a
6937                     static-stub zone with 192.0.2.1 and 2001:db8::1234
6938                     in a <span><strong class="command">server-addresses</strong></span> option,
6939                     the following RRs will be internally configured.
6940                   </p>
6941 <pre class="programlisting">example.com. NS example.com.
6942 example.com. A 192.0.2.1
6943 example.com. AAAA 2001:db8::1234</pre>
6944 <p>
6945                     These records are internally used to resolve
6946                     names under the static-stub zone.
6947                     For instance, if the server receives a query for
6948                     "www.example.com" with the RD bit on, the server
6949                     will initiate recursive resolution and send
6950                     queries to 192.0.2.1 and/or 2001:db8::1234.
6951                   </p>
6952 </dd>
6953 <dt><span class="term"><span><strong class="command">server-names</strong></span></span></dt>
6954 <dd>
6955 <p>
6956                     Only meaningful for static-stub zones.
6957                     This is a list of domain names of nameservers that
6958                     act as authoritative servers of the static-stub
6959                     zone.
6960                     These names will be resolved to IP addresses when
6961                     <span><strong class="command">named</strong></span> needs to send queries to
6962                     these servers.
6963                     To make this supplemental resolution successful,
6964                     these names must not be a subdomain of the origin
6965                     name of static-stub zone.
6966                     That is, when "example.net" is the origin of a
6967                     static-stub zone, "ns.example" and
6968                     "master.example.com" can be specified in the
6969                     <span><strong class="command">server-names</strong></span> option, but
6970                     "ns.example.net" cannot, and will be rejected by
6971                     the configuration parser.
6972                   </p>
6973 <p>
6974                     A non empty list for this option will internally
6975                     configure the apex NS RR with the specified names.
6976                     For example, if "example.com" is configured as a
6977                     static-stub zone with "ns1.example.net" and
6978                     "ns2.example.net"
6979                     in a <span><strong class="command">server-names</strong></span> option,
6980                     the following RRs will be internally configured.
6981                   </p>
6982 <pre class="programlisting">example.com. NS ns1.example.net.
6983 example.com. NS ns2.example.net.
6984 </pre>
6985 <p>
6986                     These records are internally used to resolve
6987                     names under the static-stub zone.
6988                     For instance, if the server receives a query for
6989                     "www.example.com" with the RD bit on, the server
6990                     initiate recursive resolution,
6991                     resolve "ns1.example.net" and/or
6992                     "ns2.example.net" to IP addresses, and then send
6993                     queries to (one or more of) these addresses.
6994                   </p>
6995 </dd>
6996 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
6997 <dd><p>
6998                     See the description of
6999                     <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>.
7000                   </p></dd>
7001 <dt><span class="term"><span><strong class="command">sig-signing-nodes</strong></span></span></dt>
7002 <dd><p>
7003                     See the description of
7004                     <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>.
7005                   </p></dd>
7006 <dt><span class="term"><span><strong class="command">sig-signing-signatures</strong></span></span></dt>
7007 <dd><p>
7008                     See the description of
7009                     <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>.
7010                   </p></dd>
7011 <dt><span class="term"><span><strong class="command">sig-signing-type</strong></span></span></dt>
7012 <dd><p>
7013                     See the description of
7014                     <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>.
7015                   </p></dd>
7016 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
7017 <dd><p>
7018                     See the description of
7019                     <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>.
7020                   </p></dd>
7021 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
7022 <dd><p>
7023                     See the description of
7024                     <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>.
7025                   </p></dd>
7026 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
7027 <dd><p>
7028                     See the description of
7029                     <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>.
7030                   </p></dd>
7031 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
7032 <dd><p>
7033                     See the description of
7034                     <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>.
7035                   </p></dd>
7036 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
7037 <dd><p>
7038                     See the description of
7039                     <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>.
7040                   </p></dd>
7041 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
7042 <dd><p>
7043                     See the description of
7044                     <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>.
7045                   </p></dd>
7046 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
7047 <dd><p>
7048                     See the description of
7049                     <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>.
7050                   </p></dd>
7051 <dt>
7052 <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>
7053 </dt>
7054 <dd><p>
7055                     See the description in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
7056                   </p></dd>
7057 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
7058 <dd><p>
7059                     See the description of
7060                     <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>.
7061                     (Note that the <span><strong class="command">ixfr-from-differences</strong></span>
7062                     <strong class="userinput"><code>master</code></strong> and
7063                     <strong class="userinput"><code>slave</code></strong> choices are not
7064                     available at the zone level.)
7065                   </p></dd>
7066 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
7067 <dd><p>
7068                     See the description of
7069                     <span><strong class="command">key-directory</strong></span> in <a href="Bv9ARM.ch06.html#options" title="options Statement Definition and
7070           Usage">the section called &#8220;<span><strong class="command">options</strong></span> Statement Definition and
7071           Usage&#8221;</a>.
7072                   </p></dd>
7073 <dt><span class="term"><span><strong class="command">auto-dnssec</strong></span></span></dt>
7074 <dd>
7075 <p>
7076                     Zones configured for dynamic DNS may also use this
7077                     option to allow varying levels of automatic DNSSEC key
7078                     management. There are three possible settings:
7079                   </p>
7080 <p>
7081                     <span><strong class="command">auto-dnssec allow;</strong></span> permits
7082                     keys to be updated and the zone fully re-signed
7083                     whenever the user issues the command <span><strong class="command">rndc sign
7084                     <em class="replaceable"><code>zonename</code></em></strong></span>.
7085                   </p>
7086 <p>
7087                     <span><strong class="command">auto-dnssec maintain;</strong></span> includes the
7088                     above, but also automatically adjusts the zone's DNSSEC
7089                     keys on schedule, according to the keys' timing metadata
7090                     (see <a href="man.dnssec-keygen.html" title="dnssec-keygen"><span class="refentrytitle"><span class="application">dnssec-keygen</span></span>(8)</a> and
7091                     <a href="man.dnssec-settime.html" title="dnssec-settime"><span class="refentrytitle"><span class="application">dnssec-settime</span></span>(8)</a>).  The command
7092                     <span><strong class="command">rndc sign
7093                     <em class="replaceable"><code>zonename</code></em></strong></span> causes
7094                     <span><strong class="command">named</strong></span> to load keys from the key
7095                     repository and sign the zone with all keys that are
7096                     active.
7097                     <span><strong class="command">rndc loadkeys
7098                     <em class="replaceable"><code>zonename</code></em></strong></span> causes
7099                     <span><strong class="command">named</strong></span> to load keys from the key
7100                     repository and schedule key maintenance events to occur
7101                     in the future, but it does not sign the full zone
7102                     immediately.  Note: once keys have been loaded for a
7103                     zone the first time, the repository will be searched
7104                     for changes periodically, regardless of whether
7105                     <span><strong class="command">rndc loadkeys</strong></span> is used.  The recheck
7106                     interval is hard-coded to
7107                     one hour.
7108                   </p>
7109 <p>
7110                     <span><strong class="command">auto-dnssec create;</strong></span> includes the
7111                     above, but also allows <span><strong class="command">named</strong></span>
7112                     to create new keys in the key repository when needed.
7113                     (NOTE: This option is not yet implemented; the syntax is
7114                     being reserved for future use.)
7115                   </p>
7116 <p>
7117                     The default setting is <span><strong class="command">auto-dnssec off</strong></span>.
7118                   </p>
7119 </dd>
7120 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
7121 <dd><p>
7122                     See the description of <span><strong class="command">multi-master</strong></span> in
7123                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7124                   </p></dd>
7125 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
7126 <dd><p>
7127                     See the description of <span><strong class="command">masterfile-format</strong></span>
7128                     in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
7129                   </p></dd>
7130 <dt><span class="term"><span><strong class="command">dnssec-secure-to-insecure</strong></span></span></dt>
7131 <dd><p>
7132                     See the description of
7133                     <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>.
7134                   </p></dd>
7135 </dl></div>
7136 </div>
7137 <div class="sect3" lang="en">
7138 <div class="titlepage"><div><div><h4 class="title">
7139 <a name="dynamic_update_policies"></a>Dynamic Update Policies</h4></div></div></div>
7140 <p><acronym class="acronym">BIND</acronym> 9 supports two alternative
7141               methods of granting clients the right to perform
7142               dynamic updates to a zone, configured by the
7143               <span><strong class="command">allow-update</strong></span> and
7144               <span><strong class="command">update-policy</strong></span> option, respectively.
7145             </p>
7146 <p>
7147               The <span><strong class="command">allow-update</strong></span> clause works the
7148               same way as in previous versions of <acronym class="acronym">BIND</acronym>.
7149               It grants given clients the permission to update any
7150               record of any name in the zone.
7151             </p>
7152 <p>
7153               The <span><strong class="command">update-policy</strong></span> clause
7154               allows more fine-grained control over what updates are
7155               allowed.  A set of rules is specified, where each rule
7156               either grants or denies permissions for one or more
7157               names to be updated by one or more identities.  If
7158               the dynamic update request message is signed (that is,
7159               it includes either a TSIG or SIG(0) record), the
7160               identity of the signer can be determined.
7161             </p>
7162 <p>
7163               Rules are specified in the <span><strong class="command">update-policy</strong></span>
7164               zone option, and are only meaningful for master zones.
7165               When the <span><strong class="command">update-policy</strong></span> statement
7166               is present, it is a configuration error for the
7167               <span><strong class="command">allow-update</strong></span> statement to be
7168               present.  The <span><strong class="command">update-policy</strong></span> statement
7169               only examines the signer of a message; the source
7170               address is not relevant.
7171             </p>
7172 <p>
7173               There is a pre-defined <span><strong class="command">update-policy</strong></span>
7174               rule which can be switched on with the command
7175               <span><strong class="command">update-policy local;</strong></span>.
7176               Switching on this rule in a zone causes
7177               <span><strong class="command">named</strong></span> to generate a TSIG session
7178               key and place it in a file, and to allow that key
7179               to update the zone.  (By default, the file is
7180               <code class="filename">/var/run/named/session.key</code>, the key
7181               name is "local-ddns" and the key algorithm is HMAC-SHA256,
7182               but these values are configurable with the
7183               <span><strong class="command">session-keyfile</strong></span>,
7184               <span><strong class="command">session-keyname</strong></span> and
7185               <span><strong class="command">session-keyalg</strong></span> options, respectively).
7186             </p>
7187 <p>
7188               A client running on the local system, and with appropriate
7189               permissions, may read that file and use the key to sign update
7190               requests.  The zone's update policy will be set to allow that
7191               key to change any record within the zone.  Assuming the
7192               key name is "local-ddns", this policy is equivalent to:
7193             </p>
7194 <pre class="programlisting">update-policy { grant local-ddns zonesub any; };
7195             </pre>
7196 <p>
7197               The command <span><strong class="command">nsupdate -l</strong></span> sends update
7198               requests to localhost, and signs them using the session key.
7199             </p>
7200 <p>
7201               Other rule definitions look like this:
7202             </p>
7203 <pre class="programlisting">
7204 ( <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>]
7205 </pre>
7206 <p>
7207               Each rule grants or denies privileges.  Once a message has
7208               successfully matched a rule, the operation is immediately
7209               granted or denied and no further rules are examined.  A rule
7210               is matched when the signer matches the identity field, the
7211               name matches the name field in accordance with the nametype
7212               field, and the type matches the types specified in the type
7213               field.
7214             </p>
7215 <p>
7216               No signer is required for <em class="replaceable"><code>tcp-self</code></em>
7217               or <em class="replaceable"><code>6to4-self</code></em> however the standard
7218               reverse mapping / prefix conversion must match the identity
7219               field.
7220             </p>
7221 <p>
7222               The identity field specifies a name or a wildcard
7223               name.  Normally, this is the name of the TSIG or
7224               SIG(0) key used to sign the update request.  When a
7225               TKEY exchange has been used to create a shared secret,
7226               the identity of the shared secret is the same as the
7227               identity of the key used to authenticate the TKEY
7228               exchange.  TKEY is also the negotiation method used
7229               by GSS-TSIG, which establishes an identity that is
7230               the Kerberos principal of the client, such as
7231               <strong class="userinput"><code>"user@host.domain"</code></strong>.  When the
7232               <em class="replaceable"><code>identity</code></em> field specifies
7233               a wildcard name, it is subject to DNS wildcard
7234               expansion, so the rule will apply to multiple identities.
7235               The <em class="replaceable"><code>identity</code></em> field must
7236               contain a fully-qualified domain name.
7237             </p>
7238 <p>
7239               For nametypes <code class="varname">krb5-self</code>,
7240               <code class="varname">ms-self</code>, <code class="varname">krb5-subdomain</code>,
7241               and <code class="varname">ms-subdomain</code> the
7242               <em class="replaceable"><code>identity</code></em> field specifies
7243               the Windows or Kerberos realm of the machine belongs to.
7244             </p>
7245 <p>
7246               The <em class="replaceable"><code>nametype</code></em> field has 13
7247               values:
7248               <code class="varname">name</code>, <code class="varname">subdomain</code>,
7249               <code class="varname">wildcard</code>, <code class="varname">self</code>,
7250               <code class="varname">selfsub</code>, <code class="varname">selfwild</code>,
7251               <code class="varname">krb5-self</code>, <code class="varname">ms-self</code>,
7252               <code class="varname">krb5-subdomain</code>,
7253               <code class="varname">ms-subdomain</code>,
7254               <code class="varname">tcp-self</code>, <code class="varname">6to4-self</code>,
7255               <code class="varname">zonesub</code>, and <code class="varname">external</code>.
7256             </p>
7257 <div class="informaltable"><table border="1">
7258 <colgroup>
7259 <col>
7260 <col>
7261 </colgroup>
7262 <tbody>
7263 <tr>
7264 <td>
7265                       <p>
7266                         <code class="varname">name</code>
7267                       </p>
7268                     </td>
7269 <td>
7270                       <p>
7271                         Exact-match semantics.  This rule matches
7272                         when the name being updated is identical
7273                         to the contents of the
7274                         <em class="replaceable"><code>name</code></em> field.
7275                       </p>
7276                     </td>
7277 </tr>
7278 <tr>
7279 <td>
7280                       <p>
7281                         <code class="varname">subdomain</code>
7282                       </p>
7283                     </td>
7284 <td>
7285                       <p>
7286                         This rule matches when the name being updated
7287                         is a subdomain of, or identical to, the
7288                         contents of the <em class="replaceable"><code>name</code></em>
7289                         field.
7290                       </p>
7291                     </td>
7292 </tr>
7293 <tr>
7294 <td>
7295                       <p>
7296                         <code class="varname">zonesub</code>
7297                       </p>
7298                     </td>
7299 <td>
7300                       <p>
7301                         This rule is similar to subdomain, except that
7302                         it matches when the name being updated is a
7303                         subdomain of the zone in which the
7304                         <span><strong class="command">update-policy</strong></span> statement
7305                         appears.  This obviates the need to type the zone
7306                         name twice, and enables the use of a standard
7307                         <span><strong class="command">update-policy</strong></span> statement in
7308                         multiple zones without modification.
7309                       </p>
7310                       <p>
7311                         When this rule is used, the
7312                         <em class="replaceable"><code>name</code></em> field is omitted.
7313                       </p>
7314                     </td>
7315 </tr>
7316 <tr>
7317 <td>
7318                       <p>
7319                         <code class="varname">wildcard</code>
7320                       </p>
7321                     </td>
7322 <td>
7323                       <p>
7324                         The <em class="replaceable"><code>name</code></em> field
7325                         is subject to DNS wildcard expansion, and
7326                         this rule matches when the name being updated
7327                         name is a valid expansion of the wildcard.
7328                       </p>
7329                     </td>
7330 </tr>
7331 <tr>
7332 <td>
7333                       <p>
7334                         <code class="varname">self</code>
7335                       </p>
7336                     </td>
7337 <td>
7338                       <p>
7339                         This rule matches when the name being updated
7340                         matches the contents of the
7341                         <em class="replaceable"><code>identity</code></em> field.
7342                         The <em class="replaceable"><code>name</code></em> field
7343                         is ignored, but should be the same as the
7344                         <em class="replaceable"><code>identity</code></em> field.
7345                         The <code class="varname">self</code> nametype is
7346                         most useful when allowing using one key per
7347                         name to update, where the key has the same
7348                         name as the name to be updated.  The
7349                         <em class="replaceable"><code>identity</code></em> would
7350                         be specified as <code class="constant">*</code> (an asterisk) in
7351                         this case.
7352                       </p>
7353                     </td>
7354 </tr>
7355 <tr>
7356 <td>
7357                       <p>
7358                         <code class="varname">selfsub</code>
7359                       </p>
7360                     </td>
7361 <td>
7362                       <p>
7363                         This rule is similar to <code class="varname">self</code>
7364                         except that subdomains of <code class="varname">self</code>
7365                         can also be updated.
7366                       </p>
7367                     </td>
7368 </tr>
7369 <tr>
7370 <td>
7371                       <p>
7372                         <code class="varname">selfwild</code>
7373                       </p>
7374                     </td>
7375 <td>
7376                       <p>
7377                         This rule is similar to <code class="varname">self</code>
7378                         except that only subdomains of
7379                         <code class="varname">self</code> can be updated.
7380                       </p>
7381                     </td>
7382 </tr>
7383 <tr>
7384 <td>
7385                       <p>
7386                         <code class="varname">ms-self</code>
7387                       </p>
7388                     </td>
7389 <td>
7390                       <p>
7391                         This rule takes a Windows machine principal
7392                         (machine$@REALM) for machine in REALM and
7393                         and converts it machine.realm allowing the machine
7394                         to update machine.realm.  The REALM to be matched
7395                         is specified in the <font color="red">&lt;replacable&gt;identity&lt;/replacable&gt;</font>
7396                         field.
7397                       </p>
7398                     </td>
7399 </tr>
7400 <tr>
7401 <td>
7402                       <p>
7403                         <code class="varname">ms-subdomain</code>
7404                       </p>
7405                     </td>
7406 <td>
7407                       <p>
7408                         This rule takes a Windows machine principal
7409                         (machine$@REALM) for machine in REALM and
7410                         converts it to machine.realm allowing the machine
7411                         to update subdomains of machine.realm.  The REALM
7412                         to be matched is specified in the
7413                         <font color="red">&lt;replacable&gt;identity&lt;/replacable&gt;</font> field.
7414                       </p>
7415                     </td>
7416 </tr>
7417 <tr>
7418 <td>
7419                       <p>
7420                         <code class="varname">krb5-self</code>
7421                       </p>
7422                     </td>
7423 <td>
7424                       <p>
7425                         This rule takes a Kerberos machine principal
7426                         (host/machine@REALM) for machine in REALM and
7427                         and converts it machine.realm allowing the machine
7428                         to update machine.realm.  The REALM to be matched
7429                         is specified in the <font color="red">&lt;replacable&gt;identity&lt;/replacable&gt;</font>
7430                         field.
7431                       </p>
7432                     </td>
7433 </tr>
7434 <tr>
7435 <td>
7436                       <p>
7437                         <code class="varname">krb5-subdomain</code>
7438                       </p>
7439                     </td>
7440 <td>
7441                       <p>
7442                         This rule takes a Kerberos machine principal
7443                         (host/machine@REALM) for machine in REALM and
7444                         converts it to machine.realm allowing the machine
7445                         to update subdomains of machine.realm.  The REALM
7446                         to be matched is specified in the
7447                         <font color="red">&lt;replacable&gt;identity&lt;/replacable&gt;</font> field.
7448                       </p>
7449                     </td>
7450 </tr>
7451 <tr>
7452 <td>
7453                       <p>
7454                         <code class="varname">tcp-self</code>
7455                       </p>
7456                     </td>
7457 <td>
7458                       <p>
7459                         Allow updates that have been sent via TCP and
7460                         for which the standard mapping from the initiating
7461                         IP address into the IN-ADDR.ARPA and IP6.ARPA
7462                         namespaces match the name to be updated.
7463                       </p>
7464                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
7465 <h3 class="title">Note</h3>
7466                         It is theoretically possible to spoof these TCP
7467                         sessions.
7468                       </div>
7469                     </td>
7470 </tr>
7471 <tr>
7472 <td>
7473                       <p>
7474                         <code class="varname">6to4-self</code>
7475                       </p>
7476                     </td>
7477 <td>
7478                       <p>
7479                         Allow the 6to4 prefix to be update by any TCP
7480                         connection from the 6to4 network or from the
7481                         corresponding IPv4 address.  This is intended
7482                         to allow NS or DNAME RRsets to be added to the
7483                         reverse tree.
7484                       </p>
7485                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
7486 <h3 class="title">Note</h3>
7487                         It is theoretically possible to spoof these TCP
7488                         sessions.
7489                       </div>
7490                     </td>
7491 </tr>
7492 <tr>
7493 <td>
7494                       <p>
7495                         <code class="varname">external</code>
7496                       </p>
7497                     </td>
7498 <td>
7499                       <p>
7500                         This rule allows <span><strong class="command">named</strong></span>
7501                         to defer the decision of whether to allow a
7502                         given update to an external daemon.
7503                       </p>
7504                       <p>
7505                         The method of communicating with the daemon is
7506                         specified in the <em class="replaceable"><code>identity</code></em>
7507                         field, the format of which is
7508                         "<code class="constant">local:</code><em class="replaceable"><code>path</code></em>",
7509                         where <em class="replaceable"><code>path</code></em> is the location
7510                         of a UNIX-domain socket.  (Currently, "local" is the
7511                         only supported mechanism.)
7512                       </p>
7513                       <p>
7514                         Requests to the external daemon are sent over the
7515                         UNIX-domain socket as datagrams with the following
7516                         format:
7517                       </p>
7518                       <pre class="programlisting">
7519    Protocol version number (4 bytes, network byte order, currently 1)
7520    Request length (4 bytes, network byte order)
7521    Signer (null-terminated string)
7522    Name (null-terminated string)
7523    TCP source address (null-terminated string)
7524    Rdata type (null-terminated string)
7525    Key (null-terminated string)
7526    TKEY token length (4 bytes, network byte order)
7527    TKEY token (remainder of packet)</pre>
7528                       <p>
7529                         The daemon replies with a four-byte value in
7530                         network byte order, containing either 0 or 1; 0
7531                         indicates that the specified update is not
7532                         permitted, and 1 indicates that it is.
7533                       </p>
7534                     </td>
7535 </tr>
7536 </tbody>
7537 </table></div>
7538 <p>
7539               In all cases, the <em class="replaceable"><code>name</code></em>
7540               field must specify a fully-qualified domain name.
7541             </p>
7542 <p>
7543               If no types are explicitly specified, this rule matches
7544               all types except RRSIG, NS, SOA, NSEC and NSEC3. Types
7545               may be specified by name, including "ANY" (ANY matches
7546               all types except NSEC and NSEC3, which can never be
7547               updated).  Note that when an attempt is made to delete
7548               all records associated with a name, the rules are
7549               checked for each existing record type.
7550             </p>
7551 </div>
7552 </div>
7553 </div>
7554 <div class="sect1" lang="en">
7555 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
7556 <a name="id2595030"></a>Zone File</h2></div></div></div>
7557 <div class="sect2" lang="en">
7558 <div class="titlepage"><div><div><h3 class="title">
7559 <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>
7560 <p>
7561             This section, largely borrowed from RFC 1034, describes the
7562             concept of a Resource Record (RR) and explains when each is used.
7563             Since the publication of RFC 1034, several new RRs have been
7564             identified
7565             and implemented in the DNS. These are also included.
7566           </p>
7567 <div class="sect3" lang="en">
7568 <div class="titlepage"><div><div><h4 class="title">
7569 <a name="id2595048"></a>Resource Records</h4></div></div></div>
7570 <p>
7571               A domain name identifies a node.  Each node has a set of
7572               resource information, which may be empty.  The set of resource
7573               information associated with a particular name is composed of
7574               separate RRs. The order of RRs in a set is not significant and
7575               need not be preserved by name servers, resolvers, or other
7576               parts of the DNS. However, sorting of multiple RRs is
7577               permitted for optimization purposes, for example, to specify
7578               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>.
7579             </p>
7580 <p>
7581               The components of a Resource Record are:
7582             </p>
7583 <div class="informaltable"><table border="1">
7584 <colgroup>
7585 <col>
7586 <col>
7587 </colgroup>
7588 <tbody>
7589 <tr>
7590 <td>
7591                       <p>
7592                         owner name
7593                       </p>
7594                     </td>
7595 <td>
7596                       <p>
7597                         The domain name where the RR is found.
7598                       </p>
7599                     </td>
7600 </tr>
7601 <tr>
7602 <td>
7603                       <p>
7604                         type
7605                       </p>
7606                     </td>
7607 <td>
7608                       <p>
7609                         An encoded 16-bit value that specifies
7610                         the type of the resource record.
7611                       </p>
7612                     </td>
7613 </tr>
7614 <tr>
7615 <td>
7616                       <p>
7617                         TTL
7618                       </p>
7619                     </td>
7620 <td>
7621                       <p>
7622                         The time-to-live of the RR. This field
7623                         is a 32-bit integer in units of seconds, and is
7624                         primarily used by
7625                         resolvers when they cache RRs. The TTL describes how
7626                         long a RR can
7627                         be cached before it should be discarded.
7628                       </p>
7629                     </td>
7630 </tr>
7631 <tr>
7632 <td>
7633                       <p>
7634                         class
7635                       </p>
7636                     </td>
7637 <td>
7638                       <p>
7639                         An encoded 16-bit value that identifies
7640                         a protocol family or instance of a protocol.
7641                       </p>
7642                     </td>
7643 </tr>
7644 <tr>
7645 <td>
7646                       <p>
7647                         RDATA
7648                       </p>
7649                     </td>
7650 <td>
7651                       <p>
7652                         The resource data.  The format of the
7653                         data is type (and sometimes class) specific.
7654                       </p>
7655                     </td>
7656 </tr>
7657 </tbody>
7658 </table></div>
7659 <p>
7660               The following are <span class="emphasis"><em>types</em></span> of valid RRs:
7661             </p>
7662 <div class="informaltable"><table border="1">
7663 <colgroup>
7664 <col>
7665 <col>
7666 </colgroup>
7667 <tbody>
7668 <tr>
7669 <td>
7670                       <p>
7671                         A
7672                       </p>
7673                     </td>
7674 <td>
7675                       <p>
7676                         A host address.  In the IN class, this is a
7677                         32-bit IP address.  Described in RFC 1035.
7678                       </p>
7679                     </td>
7680 </tr>
7681 <tr>
7682 <td>
7683                       <p>
7684                         AAAA
7685                       </p>
7686                     </td>
7687 <td>
7688                       <p>
7689                         IPv6 address.  Described in RFC 1886.
7690                       </p>
7691                     </td>
7692 </tr>
7693 <tr>
7694 <td>
7695                       <p>
7696                         A6
7697                       </p>
7698                     </td>
7699 <td>
7700                       <p>
7701                         IPv6 address.  This can be a partial
7702                         address (a suffix) and an indirection to the name
7703                         where the rest of the
7704                         address (the prefix) can be found.  Experimental.
7705                         Described in RFC 2874.
7706                       </p>
7707                     </td>
7708 </tr>
7709 <tr>
7710 <td>
7711                       <p>
7712                         AFSDB
7713                       </p>
7714                     </td>
7715 <td>
7716                       <p>
7717                         Location of AFS database servers.
7718                         Experimental.  Described in RFC 1183.
7719                       </p>
7720                     </td>
7721 </tr>
7722 <tr>
7723 <td>
7724                       <p>
7725                         APL
7726                       </p>
7727                     </td>
7728 <td>
7729                       <p>
7730                         Address prefix list.  Experimental.
7731                         Described in RFC 3123.
7732                       </p>
7733                     </td>
7734 </tr>
7735 <tr>
7736 <td>
7737                       <p>
7738                         CERT
7739                       </p>
7740                     </td>
7741 <td>
7742                       <p>
7743                         Holds a digital certificate.
7744                         Described in RFC 2538.
7745                       </p>
7746                     </td>
7747 </tr>
7748 <tr>
7749 <td>
7750                       <p>
7751                         CNAME
7752                       </p>
7753                     </td>
7754 <td>
7755                       <p>
7756                         Identifies the canonical name of an alias.
7757                         Described in RFC 1035.
7758                       </p>
7759                     </td>
7760 </tr>
7761 <tr>
7762 <td>
7763                       <p>
7764                         DHCID
7765                       </p>
7766                     </td>
7767 <td>
7768                       <p>
7769                         Is used for identifying which DHCP client is
7770                         associated with this name.  Described in RFC 4701.
7771                       </p>
7772                     </td>
7773 </tr>
7774 <tr>
7775 <td>
7776                       <p>
7777                         DNAME
7778                       </p>
7779                     </td>
7780 <td>
7781                       <p>
7782                         Replaces the domain name specified with
7783                         another name to be looked up, effectively aliasing an
7784                         entire
7785                         subtree of the domain name space rather than a single
7786                         record
7787                         as in the case of the CNAME RR.
7788                         Described in RFC 2672.
7789                       </p>
7790                     </td>
7791 </tr>
7792 <tr>
7793 <td>
7794                       <p>
7795                         DNSKEY
7796                       </p>
7797                     </td>
7798 <td>
7799                       <p>
7800                         Stores a public key associated with a signed
7801                         DNS zone.  Described in RFC 4034.
7802                       </p>
7803                     </td>
7804 </tr>
7805 <tr>
7806 <td>
7807                       <p>
7808                         DS
7809                       </p>
7810                     </td>
7811 <td>
7812                       <p>
7813                         Stores the hash of a public key associated with a
7814                         signed DNS zone.  Described in RFC 4034.
7815                       </p>
7816                     </td>
7817 </tr>
7818 <tr>
7819 <td>
7820                       <p>
7821                         GPOS
7822                       </p>
7823                     </td>
7824 <td>
7825                       <p>
7826                         Specifies the global position.  Superseded by LOC.
7827                       </p>
7828                     </td>
7829 </tr>
7830 <tr>
7831 <td>
7832                       <p>
7833                         HINFO
7834                       </p>
7835                     </td>
7836 <td>
7837                       <p>
7838                         Identifies the CPU and OS used by a host.
7839                         Described in RFC 1035.
7840                       </p>
7841                     </td>
7842 </tr>
7843 <tr>
7844 <td>
7845                       <p>
7846                         IPSECKEY
7847                       </p>
7848                     </td>
7849 <td>
7850                       <p>
7851                         Provides a method for storing IPsec keying material in
7852                         DNS.  Described in RFC 4025.
7853                       </p>
7854                     </td>
7855 </tr>
7856 <tr>
7857 <td>
7858                       <p>
7859                         ISDN
7860                       </p>
7861                     </td>
7862 <td>
7863                       <p>
7864                         Representation of ISDN addresses.
7865                         Experimental.  Described in RFC 1183.
7866                       </p>
7867                     </td>
7868 </tr>
7869 <tr>
7870 <td>
7871                       <p>
7872                         KEY
7873                       </p>
7874                     </td>
7875 <td>
7876                       <p>
7877                         Stores a public key associated with a
7878                         DNS name.  Used in original DNSSEC; replaced
7879                         by DNSKEY in DNSSECbis, but still used with
7880                         SIG(0).  Described in RFCs 2535 and 2931.
7881                       </p>
7882                     </td>
7883 </tr>
7884 <tr>
7885 <td>
7886                       <p>
7887                         KX
7888                       </p>
7889                     </td>
7890 <td>
7891                       <p>
7892                         Identifies a key exchanger for this
7893                         DNS name.  Described in RFC 2230.
7894                       </p>
7895                     </td>
7896 </tr>
7897 <tr>
7898 <td>
7899                       <p>
7900                         LOC
7901                       </p>
7902                     </td>
7903 <td>
7904                       <p>
7905                         For storing GPS info.  Described in RFC 1876.
7906                         Experimental.
7907                       </p>
7908                     </td>
7909 </tr>
7910 <tr>
7911 <td>
7912                       <p>
7913                         MX
7914                       </p>
7915                     </td>
7916 <td>
7917                       <p>
7918                         Identifies a mail exchange for the domain with
7919                         a 16-bit preference value (lower is better)
7920                         followed by the host name of the mail exchange.
7921                         Described in RFC 974, RFC 1035.
7922                       </p>
7923                     </td>
7924 </tr>
7925 <tr>
7926 <td>
7927                       <p>
7928                         NAPTR
7929                       </p>
7930                     </td>
7931 <td>
7932                       <p>
7933                         Name authority pointer.  Described in RFC 2915.
7934                       </p>
7935                     </td>
7936 </tr>
7937 <tr>
7938 <td>
7939                       <p>
7940                         NSAP
7941                       </p>
7942                     </td>
7943 <td>
7944                       <p>
7945                         A network service access point.
7946                         Described in RFC 1706.
7947                       </p>
7948                     </td>
7949 </tr>
7950 <tr>
7951 <td>
7952                       <p>
7953                         NS
7954                       </p>
7955                     </td>
7956 <td>
7957                       <p>
7958                         The authoritative name server for the
7959                         domain.  Described in RFC 1035.
7960                       </p>
7961                     </td>
7962 </tr>
7963 <tr>
7964 <td>
7965                       <p>
7966                         NSEC
7967                       </p>
7968                     </td>
7969 <td>
7970                       <p>
7971                         Used in DNSSECbis to securely indicate that
7972                         RRs with an owner name in a certain name interval do
7973                         not exist in
7974                         a zone and indicate what RR types are present for an
7975                         existing name.
7976                         Described in RFC 4034.
7977                       </p>
7978                     </td>
7979 </tr>
7980 <tr>
7981 <td>
7982                       <p>
7983                         NSEC3
7984                       </p>
7985                     </td>
7986 <td>
7987                       <p>
7988                         Used in DNSSECbis to securely indicate that
7989                         RRs with an owner name in a certain name
7990                         interval do not exist in a zone and indicate
7991                         what RR types are present for an existing
7992                         name.  NSEC3 differs from NSEC in that it
7993                         prevents zone enumeration but is more
7994                         computationally expensive on both the server
7995                         and the client than NSEC.  Described in RFC
7996                         5155.
7997                       </p>
7998                     </td>
7999 </tr>
8000 <tr>
8001 <td>
8002                       <p>
8003                         NSEC3PARAM
8004                       </p>
8005                     </td>
8006 <td>
8007                       <p>
8008                         Used in DNSSECbis to tell the authoritative
8009                         server which NSEC3 chains are available to use.
8010                         Described in RFC 5155.
8011                       </p>
8012                     </td>
8013 </tr>
8014 <tr>
8015 <td>
8016                       <p>
8017                         NXT
8018                       </p>
8019                     </td>
8020 <td>
8021                       <p>
8022                         Used in DNSSEC to securely indicate that
8023                         RRs with an owner name in a certain name interval do
8024                         not exist in
8025                         a zone and indicate what RR types are present for an
8026                         existing name.
8027                         Used in original DNSSEC; replaced by NSEC in
8028                         DNSSECbis.
8029                         Described in RFC 2535.
8030                       </p>
8031                     </td>
8032 </tr>
8033 <tr>
8034 <td>
8035                       <p>
8036                         PTR
8037                       </p>
8038                     </td>
8039 <td>
8040                       <p>
8041                         A pointer to another part of the domain
8042                         name space.  Described in RFC 1035.
8043                       </p>
8044                     </td>
8045 </tr>
8046 <tr>
8047 <td>
8048                       <p>
8049                         PX
8050                       </p>
8051                     </td>
8052 <td>
8053                       <p>
8054                         Provides mappings between RFC 822 and X.400
8055                         addresses.  Described in RFC 2163.
8056                       </p>
8057                     </td>
8058 </tr>
8059 <tr>
8060 <td>
8061                       <p>
8062                         RP
8063                       </p>
8064                     </td>
8065 <td>
8066                       <p>
8067                         Information on persons responsible
8068                         for the domain.  Experimental.  Described in RFC 1183.
8069                       </p>
8070                     </td>
8071 </tr>
8072 <tr>
8073 <td>
8074                       <p>
8075                         RRSIG
8076                       </p>
8077                     </td>
8078 <td>
8079                       <p>
8080                         Contains DNSSECbis signature data.  Described
8081                         in RFC 4034.
8082                       </p>
8083                     </td>
8084 </tr>
8085 <tr>
8086 <td>
8087                       <p>
8088                         RT
8089                       </p>
8090                     </td>
8091 <td>
8092                       <p>
8093                         Route-through binding for hosts that
8094                         do not have their own direct wide area network
8095                         addresses.
8096                         Experimental.  Described in RFC 1183.
8097                       </p>
8098                     </td>
8099 </tr>
8100 <tr>
8101 <td>
8102                       <p>
8103                         SIG
8104                       </p>
8105                     </td>
8106 <td>
8107                       <p>
8108                         Contains DNSSEC signature data.  Used in
8109                         original DNSSEC; replaced by RRSIG in
8110                         DNSSECbis, but still used for SIG(0).
8111                         Described in RFCs 2535 and 2931.
8112                       </p>
8113                     </td>
8114 </tr>
8115 <tr>
8116 <td>
8117                       <p>
8118                         SOA
8119                       </p>
8120                     </td>
8121 <td>
8122                       <p>
8123                         Identifies the start of a zone of authority.
8124                         Described in RFC 1035.
8125                       </p>
8126                     </td>
8127 </tr>
8128 <tr>
8129 <td>
8130                       <p>
8131                         SPF
8132                       </p>
8133                     </td>
8134 <td>
8135                       <p>
8136                         Contains the Sender Policy Framework information
8137                         for a given email domain.  Described in RFC 4408.
8138                       </p>
8139                     </td>
8140 </tr>
8141 <tr>
8142 <td>
8143                       <p>
8144                         SRV
8145                       </p>
8146                     </td>
8147 <td>
8148                       <p>
8149                         Information about well known network
8150                         services (replaces WKS).  Described in RFC 2782.
8151                       </p>
8152                     </td>
8153 </tr>
8154 <tr>
8155 <td>
8156                       <p>
8157                         SSHFP
8158                       </p>
8159                     </td>
8160 <td>
8161                       <p>
8162                         Provides a way to securely publish a secure shell key's
8163                         fingerprint.  Described in RFC 4255.
8164                       </p>
8165                     </td>
8166 </tr>
8167 <tr>
8168 <td>
8169                       <p>
8170                         TXT
8171                       </p>
8172                     </td>
8173 <td>
8174                       <p>
8175                         Text records.  Described in RFC 1035.
8176                       </p>
8177                     </td>
8178 </tr>
8179 <tr>
8180 <td>
8181                       <p>
8182                         WKS
8183                       </p>
8184                     </td>
8185 <td>
8186                       <p>
8187                         Information about which well known
8188                         network services, such as SMTP, that a domain
8189                         supports. Historical.
8190                       </p>
8191                     </td>
8192 </tr>
8193 <tr>
8194 <td>
8195                       <p>
8196                         X25
8197                       </p>
8198                     </td>
8199 <td>
8200                       <p>
8201                         Representation of X.25 network addresses.
8202                         Experimental.  Described in RFC 1183.
8203                       </p>
8204                     </td>
8205 </tr>
8206 </tbody>
8207 </table></div>
8208 <p>
8209               The following <span class="emphasis"><em>classes</em></span> of resource records
8210               are currently valid in the DNS:
8211             </p>
8212 <div class="informaltable"><table border="1">
8213 <colgroup>
8214 <col>
8215 <col>
8216 </colgroup>
8217 <tbody>
8218 <tr>
8219 <td>
8220                       <p>
8221                         IN
8222                       </p>
8223                     </td>
8224 <td>
8225                       <p>
8226                         The Internet.
8227                       </p>
8228                     </td>
8229 </tr>
8230 <tr>
8231 <td>
8232                       <p>
8233                         CH
8234                       </p>
8235                     </td>
8236 <td>
8237                       <p>
8238                         Chaosnet, a LAN protocol created at MIT in the
8239                         mid-1970s.
8240                         Rarely used for its historical purpose, but reused for
8241                         BIND's
8242                         built-in server information zones, e.g.,
8243                         <code class="literal">version.bind</code>.
8244                       </p>
8245                     </td>
8246 </tr>
8247 <tr>
8248 <td>
8249                       <p>
8250                         HS
8251                       </p>
8252                     </td>
8253 <td>
8254                       <p>
8255                         Hesiod, an information service
8256                         developed by MIT's Project Athena. It is used to share
8257                         information
8258                         about various systems databases, such as users,
8259                         groups, printers
8260                         and so on.
8261                       </p>
8262                     </td>
8263 </tr>
8264 </tbody>
8265 </table></div>
8266 <p>
8267               The owner name is often implicit, rather than forming an
8268               integral
8269               part of the RR.  For example, many name servers internally form
8270               tree
8271               or hash structures for the name space, and chain RRs off nodes.
8272               The remaining RR parts are the fixed header (type, class, TTL)
8273               which is consistent for all RRs, and a variable part (RDATA)
8274               that
8275               fits the needs of the resource being described.
8276             </p>
8277 <p>
8278               The meaning of the TTL field is a time limit on how long an
8279               RR can be kept in a cache.  This limit does not apply to
8280               authoritative
8281               data in zones; it is also timed out, but by the refreshing
8282               policies
8283               for the zone.  The TTL is assigned by the administrator for the
8284               zone where the data originates.  While short TTLs can be used to
8285               minimize caching, and a zero TTL prohibits caching, the
8286               realities
8287               of Internet performance suggest that these times should be on
8288               the
8289               order of days for the typical host.  If a change can be
8290               anticipated,
8291               the TTL can be reduced prior to the change to minimize
8292               inconsistency
8293               during the change, and then increased back to its former value
8294               following
8295               the change.
8296             </p>
8297 <p>
8298               The data in the RDATA section of RRs is carried as a combination
8299               of binary strings and domain names.  The domain names are
8300               frequently
8301               used as "pointers" to other data in the DNS.
8302             </p>
8303 </div>
8304 <div class="sect3" lang="en">
8305 <div class="titlepage"><div><div><h4 class="title">
8306 <a name="id2596603"></a>Textual expression of RRs</h4></div></div></div>
8307 <p>
8308               RRs are represented in binary form in the packets of the DNS
8309               protocol, and are usually represented in highly encoded form
8310               when
8311               stored in a name server or resolver.  In the examples provided
8312               in
8313               RFC 1034, a style similar to that used in master files was
8314               employed
8315               in order to show the contents of RRs.  In this format, most RRs
8316               are shown on a single line, although continuation lines are
8317               possible
8318               using parentheses.
8319             </p>
8320 <p>
8321               The start of the line gives the owner of the RR.  If a line
8322               begins with a blank, then the owner is assumed to be the same as
8323               that of the previous RR.  Blank lines are often included for
8324               readability.
8325             </p>
8326 <p>
8327               Following the owner, we list the TTL, type, and class of the
8328               RR.  Class and type use the mnemonics defined above, and TTL is
8329               an integer before the type field.  In order to avoid ambiguity
8330               in
8331               parsing, type and class mnemonics are disjoint, TTLs are
8332               integers,
8333               and the type mnemonic is always last. The IN class and TTL
8334               values
8335               are often omitted from examples in the interests of clarity.
8336             </p>
8337 <p>
8338               The resource data or RDATA section of the RR are given using
8339               knowledge of the typical representation for the data.
8340             </p>
8341 <p>
8342               For example, we might show the RRs carried in a message as:
8343             </p>
8344 <div class="informaltable"><table border="1">
8345 <colgroup>
8346 <col>
8347 <col>
8348 <col>
8349 </colgroup>
8350 <tbody>
8351 <tr>
8352 <td>
8353                       <p>
8354                         <code class="literal">ISI.EDU.</code>
8355                       </p>
8356                     </td>
8357 <td>
8358                       <p>
8359                         <code class="literal">MX</code>
8360                       </p>
8361                     </td>
8362 <td>
8363                       <p>
8364                         <code class="literal">10 VENERA.ISI.EDU.</code>
8365                       </p>
8366                     </td>
8367 </tr>
8368 <tr>
8369 <td>
8370                       <p></p>
8371                     </td>
8372 <td>
8373                       <p>
8374                         <code class="literal">MX</code>
8375                       </p>
8376                     </td>
8377 <td>
8378                       <p>
8379                         <code class="literal">10 VAXA.ISI.EDU</code>
8380                       </p>
8381                     </td>
8382 </tr>
8383 <tr>
8384 <td>
8385                       <p>
8386                         <code class="literal">VENERA.ISI.EDU</code>
8387                       </p>
8388                     </td>
8389 <td>
8390                       <p>
8391                         <code class="literal">A</code>
8392                       </p>
8393                     </td>
8394 <td>
8395                       <p>
8396                         <code class="literal">128.9.0.32</code>
8397                       </p>
8398                     </td>
8399 </tr>
8400 <tr>
8401 <td>
8402                       <p></p>
8403                     </td>
8404 <td>
8405                       <p>
8406                         <code class="literal">A</code>
8407                       </p>
8408                     </td>
8409 <td>
8410                       <p>
8411                         <code class="literal">10.1.0.52</code>
8412                       </p>
8413                     </td>
8414 </tr>
8415 <tr>
8416 <td>
8417                       <p>
8418                         <code class="literal">VAXA.ISI.EDU</code>
8419                       </p>
8420                     </td>
8421 <td>
8422                       <p>
8423                         <code class="literal">A</code>
8424                       </p>
8425                     </td>
8426 <td>
8427                       <p>
8428                         <code class="literal">10.2.0.27</code>
8429                       </p>
8430                     </td>
8431 </tr>
8432 <tr>
8433 <td>
8434                       <p></p>
8435                     </td>
8436 <td>
8437                       <p>
8438                         <code class="literal">A</code>
8439                       </p>
8440                     </td>
8441 <td>
8442                       <p>
8443                         <code class="literal">128.9.0.33</code>
8444                       </p>
8445                     </td>
8446 </tr>
8447 </tbody>
8448 </table></div>
8449 <p>
8450               The MX RRs have an RDATA section which consists of a 16-bit
8451               number followed by a domain name.  The address RRs use a
8452               standard
8453               IP address format to contain a 32-bit internet address.
8454             </p>
8455 <p>
8456               The above example shows six RRs, with two RRs at each of three
8457               domain names.
8458             </p>
8459 <p>
8460               Similarly we might see:
8461             </p>
8462 <div class="informaltable"><table border="1">
8463 <colgroup>
8464 <col>
8465 <col>
8466 <col>
8467 </colgroup>
8468 <tbody>
8469 <tr>
8470 <td>
8471                       <p>
8472                         <code class="literal">XX.LCS.MIT.EDU.</code>
8473                       </p>
8474                     </td>
8475 <td>
8476                       <p>
8477                         <code class="literal">IN A</code>
8478                       </p>
8479                     </td>
8480 <td>
8481                       <p>
8482                         <code class="literal">10.0.0.44</code>
8483                       </p>
8484                     </td>
8485 </tr>
8486 <tr>
8487 <td> </td>
8488 <td>
8489                       <p>
8490                         <code class="literal">CH A</code>
8491                       </p>
8492                     </td>
8493 <td>
8494                       <p>
8495                         <code class="literal">MIT.EDU. 2420</code>
8496                       </p>
8497                     </td>
8498 </tr>
8499 </tbody>
8500 </table></div>
8501 <p>
8502               This example shows two addresses for
8503               <code class="literal">XX.LCS.MIT.EDU</code>, each of a different class.
8504             </p>
8505 </div>
8506 </div>
8507 <div class="sect2" lang="en">
8508 <div class="titlepage"><div><div><h3 class="title">
8509 <a name="id2597260"></a>Discussion of MX Records</h3></div></div></div>
8510 <p>
8511             As described above, domain servers store information as a
8512             series of resource records, each of which contains a particular
8513             piece of information about a given domain name (which is usually,
8514             but not always, a host). The simplest way to think of a RR is as
8515             a typed pair of data, a domain name matched with a relevant datum,
8516             and stored with some additional type information to help systems
8517             determine when the RR is relevant.
8518           </p>
8519 <p>
8520             MX records are used to control delivery of email. The data
8521             specified in the record is a priority and a domain name. The
8522             priority
8523             controls the order in which email delivery is attempted, with the
8524             lowest number first. If two priorities are the same, a server is
8525             chosen randomly. If no servers at a given priority are responding,
8526             the mail transport agent will fall back to the next largest
8527             priority.
8528             Priority numbers do not have any absolute meaning &#8212; they are
8529             relevant
8530             only respective to other MX records for that domain name. The
8531             domain
8532             name given is the machine to which the mail will be delivered.
8533             It <span class="emphasis"><em>must</em></span> have an associated address record
8534             (A or AAAA) &#8212; CNAME is not sufficient.
8535           </p>
8536 <p>
8537             For a given domain, if there is both a CNAME record and an
8538             MX record, the MX record is in error, and will be ignored.
8539             Instead,
8540             the mail will be delivered to the server specified in the MX
8541             record
8542             pointed to by the CNAME.
8543             For example:
8544           </p>
8545 <div class="informaltable"><table border="1">
8546 <colgroup>
8547 <col>
8548 <col>
8549 <col>
8550 <col>
8551 <col>
8552 </colgroup>
8553 <tbody>
8554 <tr>
8555 <td>
8556                     <p>
8557                       <code class="literal">example.com.</code>
8558                     </p>
8559                   </td>
8560 <td>
8561                     <p>
8562                       <code class="literal">IN</code>
8563                     </p>
8564                   </td>
8565 <td>
8566                     <p>
8567                       <code class="literal">MX</code>
8568                     </p>
8569                   </td>
8570 <td>
8571                     <p>
8572                       <code class="literal">10</code>
8573                     </p>
8574                   </td>
8575 <td>
8576                     <p>
8577                       <code class="literal">mail.example.com.</code>
8578                     </p>
8579                   </td>
8580 </tr>
8581 <tr>
8582 <td>
8583                     <p></p>
8584                   </td>
8585 <td>
8586                     <p>
8587                       <code class="literal">IN</code>
8588                     </p>
8589                   </td>
8590 <td>
8591                     <p>
8592                       <code class="literal">MX</code>
8593                     </p>
8594                   </td>
8595 <td>
8596                     <p>
8597                       <code class="literal">10</code>
8598                     </p>
8599                   </td>
8600 <td>
8601                     <p>
8602                       <code class="literal">mail2.example.com.</code>
8603                     </p>
8604                   </td>
8605 </tr>
8606 <tr>
8607 <td>
8608                     <p></p>
8609                   </td>
8610 <td>
8611                     <p>
8612                       <code class="literal">IN</code>
8613                     </p>
8614                   </td>
8615 <td>
8616                     <p>
8617                       <code class="literal">MX</code>
8618                     </p>
8619                   </td>
8620 <td>
8621                     <p>
8622                       <code class="literal">20</code>
8623                     </p>
8624                   </td>
8625 <td>
8626                     <p>
8627                       <code class="literal">mail.backup.org.</code>
8628                     </p>
8629                   </td>
8630 </tr>
8631 <tr>
8632 <td>
8633                     <p>
8634                       <code class="literal">mail.example.com.</code>
8635                     </p>
8636                   </td>
8637 <td>
8638                     <p>
8639                       <code class="literal">IN</code>
8640                     </p>
8641                   </td>
8642 <td>
8643                     <p>
8644                       <code class="literal">A</code>
8645                     </p>
8646                   </td>
8647 <td>
8648                     <p>
8649                       <code class="literal">10.0.0.1</code>
8650                     </p>
8651                   </td>
8652 <td>
8653                     <p></p>
8654                   </td>
8655 </tr>
8656 <tr>
8657 <td>
8658                     <p>
8659                       <code class="literal">mail2.example.com.</code>
8660                     </p>
8661                   </td>
8662 <td>
8663                     <p>
8664                       <code class="literal">IN</code>
8665                     </p>
8666                   </td>
8667 <td>
8668                     <p>
8669                       <code class="literal">A</code>
8670                     </p>
8671                   </td>
8672 <td>
8673                     <p>
8674                       <code class="literal">10.0.0.2</code>
8675                     </p>
8676                   </td>
8677 <td>
8678                     <p></p>
8679                   </td>
8680 </tr>
8681 </tbody>
8682 </table></div>
8683 <p>
8684             Mail delivery will be attempted to <code class="literal">mail.example.com</code> and
8685             <code class="literal">mail2.example.com</code> (in
8686             any order), and if neither of those succeed, delivery to <code class="literal">mail.backup.org</code> will
8687             be attempted.
8688           </p>
8689 </div>
8690 <div class="sect2" lang="en">
8691 <div class="titlepage"><div><div><h3 class="title">
8692 <a name="Setting_TTLs"></a>Setting TTLs</h3></div></div></div>
8693 <p>
8694             The time-to-live of the RR field is a 32-bit integer represented
8695             in units of seconds, and is primarily used by resolvers when they
8696             cache RRs. The TTL describes how long a RR can be cached before it
8697             should be discarded. The following three types of TTL are
8698             currently
8699             used in a zone file.
8700           </p>
8701 <div class="informaltable"><table border="1">
8702 <colgroup>
8703 <col>
8704 <col>
8705 </colgroup>
8706 <tbody>
8707 <tr>
8708 <td>
8709                     <p>
8710                       SOA
8711                     </p>
8712                   </td>
8713 <td>
8714                     <p>
8715                       The last field in the SOA is the negative
8716                       caching TTL. This controls how long other servers will
8717                       cache no-such-domain
8718                       (NXDOMAIN) responses from you.
8719                     </p>
8720                     <p>
8721                       The maximum time for
8722                       negative caching is 3 hours (3h).
8723                     </p>
8724                   </td>
8725 </tr>
8726 <tr>
8727 <td>
8728                     <p>
8729                       $TTL
8730                     </p>
8731                   </td>
8732 <td>
8733                     <p>
8734                       The $TTL directive at the top of the
8735                       zone file (before the SOA) gives a default TTL for every
8736                       RR without
8737                       a specific TTL set.
8738                     </p>
8739                   </td>
8740 </tr>
8741 <tr>
8742 <td>
8743                     <p>
8744                       RR TTLs
8745                     </p>
8746                   </td>
8747 <td>
8748                     <p>
8749                       Each RR can have a TTL as the second
8750                       field in the RR, which will control how long other
8751                       servers can cache
8752                       the it.
8753                     </p>
8754                   </td>
8755 </tr>
8756 </tbody>
8757 </table></div>
8758 <p>
8759             All of these TTLs default to units of seconds, though units
8760             can be explicitly specified, for example, <code class="literal">1h30m</code>.
8761           </p>
8762 </div>
8763 <div class="sect2" lang="en">
8764 <div class="titlepage"><div><div><h3 class="title">
8765 <a name="id2597876"></a>Inverse Mapping in IPv4</h3></div></div></div>
8766 <p>
8767             Reverse name resolution (that is, translation from IP address
8768             to name) is achieved by means of the <span class="emphasis"><em>in-addr.arpa</em></span> domain
8769             and PTR records. Entries in the in-addr.arpa domain are made in
8770             least-to-most significant order, read left to right. This is the
8771             opposite order to the way IP addresses are usually written. Thus,
8772             a machine with an IP address of 10.1.2.3 would have a
8773             corresponding
8774             in-addr.arpa name of
8775             3.2.1.10.in-addr.arpa. This name should have a PTR resource record
8776             whose data field is the name of the machine or, optionally,
8777             multiple
8778             PTR records if the machine has more than one name. For example,
8779             in the [<span class="optional">example.com</span>] domain:
8780           </p>
8781 <div class="informaltable"><table border="1">
8782 <colgroup>
8783 <col>
8784 <col>
8785 </colgroup>
8786 <tbody>
8787 <tr>
8788 <td>
8789                     <p>
8790                       <code class="literal">$ORIGIN</code>
8791                     </p>
8792                   </td>
8793 <td>
8794                     <p>
8795                       <code class="literal">2.1.10.in-addr.arpa</code>
8796                     </p>
8797                   </td>
8798 </tr>
8799 <tr>
8800 <td>
8801                     <p>
8802                       <code class="literal">3</code>
8803                     </p>
8804                   </td>
8805 <td>
8806                     <p>
8807                       <code class="literal">IN PTR foo.example.com.</code>
8808                     </p>
8809                   </td>
8810 </tr>
8811 </tbody>
8812 </table></div>
8813 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
8814 <h3 class="title">Note</h3>
8815 <p>
8816               The <span><strong class="command">$ORIGIN</strong></span> lines in the examples
8817               are for providing context to the examples only &#8212; they do not
8818               necessarily
8819               appear in the actual usage. They are only used here to indicate
8820               that the example is relative to the listed origin.
8821             </p>
8822 </div>
8823 </div>
8824 <div class="sect2" lang="en">
8825 <div class="titlepage"><div><div><h3 class="title">
8826 <a name="id2598003"></a>Other Zone File Directives</h3></div></div></div>
8827 <p>
8828             The Master File Format was initially defined in RFC 1035 and
8829             has subsequently been extended. While the Master File Format
8830             itself
8831             is class independent all records in a Master File must be of the
8832             same
8833             class.
8834           </p>
8835 <p>
8836             Master File Directives include <span><strong class="command">$ORIGIN</strong></span>, <span><strong class="command">$INCLUDE</strong></span>,
8837             and <span><strong class="command">$TTL.</strong></span>
8838           </p>
8839 <div class="sect3" lang="en">
8840 <div class="titlepage"><div><div><h4 class="title">
8841 <a name="id2598093"></a>The <span><strong class="command">@</strong></span> (at-sign)</h4></div></div></div>
8842 <p>
8843               When used in the label (or name) field, the asperand or
8844               at-sign (@) symbol represents the current origin.
8845               At the start of the zone file, it is the
8846               &lt;<code class="varname">zone_name</code>&gt; (followed by
8847               trailing dot).
8848             </p>
8849 </div>
8850 <div class="sect3" lang="en">
8851 <div class="titlepage"><div><div><h4 class="title">
8852 <a name="id2598109"></a>The <span><strong class="command">$ORIGIN</strong></span> Directive</h4></div></div></div>
8853 <p>
8854               Syntax: <span><strong class="command">$ORIGIN</strong></span>
8855               <em class="replaceable"><code>domain-name</code></em>
8856               [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
8857             </p>
8858 <p><span><strong class="command">$ORIGIN</strong></span>
8859               sets the domain name that will be appended to any
8860               unqualified records. When a zone is first read in there
8861               is an implicit <span><strong class="command">$ORIGIN</strong></span>
8862               &lt;<code class="varname">zone_name</code>&gt;<span><strong class="command">.</strong></span>
8863               (followed by trailing dot).
8864               The current <span><strong class="command">$ORIGIN</strong></span> is appended to
8865               the domain specified in the <span><strong class="command">$ORIGIN</strong></span>
8866               argument if it is not absolute.
8867             </p>
8868 <pre class="programlisting">
8869 $ORIGIN example.com.
8870 WWW     CNAME   MAIN-SERVER
8871 </pre>
8872 <p>
8873               is equivalent to
8874             </p>
8875 <pre class="programlisting">
8876 WWW.EXAMPLE.COM. CNAME MAIN-SERVER.EXAMPLE.COM.
8877 </pre>
8878 </div>
8879 <div class="sect3" lang="en">
8880 <div class="titlepage"><div><div><h4 class="title">
8881 <a name="id2598170"></a>The <span><strong class="command">$INCLUDE</strong></span> Directive</h4></div></div></div>
8882 <p>
8883               Syntax: <span><strong class="command">$INCLUDE</strong></span>
8884               <em class="replaceable"><code>filename</code></em>
8885               [<span class="optional">
8886 <em class="replaceable"><code>origin</code></em> </span>]
8887               [<span class="optional"> <em class="replaceable"><code>comment</code></em> </span>]
8888             </p>
8889 <p>
8890               Read and process the file <code class="filename">filename</code> as
8891               if it were included into the file at this point.  If <span><strong class="command">origin</strong></span> is
8892               specified the file is processed with <span><strong class="command">$ORIGIN</strong></span> set
8893               to that value, otherwise the current <span><strong class="command">$ORIGIN</strong></span> is
8894               used.
8895             </p>
8896 <p>
8897               The origin and the current domain name
8898               revert to the values they had prior to the <span><strong class="command">$INCLUDE</strong></span> once
8899               the file has been read.
8900             </p>
8901 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
8902 <h3 class="title">Note</h3>
8903 <p>
8904                 RFC 1035 specifies that the current origin should be restored
8905                 after
8906                 an <span><strong class="command">$INCLUDE</strong></span>, but it is silent
8907                 on whether the current
8908                 domain name should also be restored.  BIND 9 restores both of
8909                 them.
8910                 This could be construed as a deviation from RFC 1035, a
8911                 feature, or both.
8912               </p>
8913 </div>
8914 </div>
8915 <div class="sect3" lang="en">
8916 <div class="titlepage"><div><div><h4 class="title">
8917 <a name="id2598240"></a>The <span><strong class="command">$TTL</strong></span> Directive</h4></div></div></div>
8918 <p>
8919               Syntax: <span><strong class="command">$TTL</strong></span>
8920               <em class="replaceable"><code>default-ttl</code></em>
8921               [<span class="optional">
8922 <em class="replaceable"><code>comment</code></em> </span>]
8923             </p>
8924 <p>
8925               Set the default Time To Live (TTL) for subsequent records
8926               with undefined TTLs. Valid TTLs are of the range 0-2147483647
8927               seconds.
8928             </p>
8929 <p><span><strong class="command">$TTL</strong></span>
8930                is defined in RFC 2308.
8931             </p>
8932 </div>
8933 </div>
8934 <div class="sect2" lang="en">
8935 <div class="titlepage"><div><div><h3 class="title">
8936 <a name="id2598276"></a><acronym class="acronym">BIND</acronym> Master File Extension: the  <span><strong class="command">$GENERATE</strong></span> Directive</h3></div></div></div>
8937 <p>
8938             Syntax: <span><strong class="command">$GENERATE</strong></span>
8939             <em class="replaceable"><code>range</code></em>
8940             <em class="replaceable"><code>lhs</code></em>
8941             [<span class="optional"><em class="replaceable"><code>ttl</code></em></span>]
8942             [<span class="optional"><em class="replaceable"><code>class</code></em></span>]
8943             <em class="replaceable"><code>type</code></em>
8944             <em class="replaceable"><code>rhs</code></em>
8945             [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
8946           </p>
8947 <p><span><strong class="command">$GENERATE</strong></span>
8948             is used to create a series of resource records that only
8949             differ from each other by an
8950             iterator. <span><strong class="command">$GENERATE</strong></span> can be used to
8951             easily generate the sets of records required to support
8952             sub /24 reverse delegations described in RFC 2317:
8953             Classless IN-ADDR.ARPA delegation.
8954           </p>
8955 <pre class="programlisting">$ORIGIN 0.0.192.IN-ADDR.ARPA.
8956 $GENERATE 1-2 @ NS SERVER$.EXAMPLE.
8957 $GENERATE 1-127 $ CNAME $.0</pre>
8958 <p>
8959             is equivalent to
8960           </p>
8961 <pre class="programlisting">0.0.0.192.IN-ADDR.ARPA. NS SERVER1.EXAMPLE.
8962 0.0.0.192.IN-ADDR.ARPA. NS SERVER2.EXAMPLE.
8963 1.0.0.192.IN-ADDR.ARPA. CNAME 1.0.0.0.192.IN-ADDR.ARPA.
8964 2.0.0.192.IN-ADDR.ARPA. CNAME 2.0.0.0.192.IN-ADDR.ARPA.
8965 ...
8966 127.0.0.192.IN-ADDR.ARPA. CNAME 127.0.0.0.192.IN-ADDR.ARPA.
8967 </pre>
8968 <p>
8969             Generate a set of A and MX records.  Note the MX's right hand
8970             side is a quoted string.  The quotes will be stripped when the
8971             right hand side is processed.
8972            </p>
8973 <pre class="programlisting">
8974 $ORIGIN EXAMPLE.
8975 $GENERATE 1-127 HOST-$ A 1.2.3.$
8976 $GENERATE 1-127 HOST-$ MX "0 ."</pre>
8977 <p>
8978             is equivalent to
8979           </p>
8980 <pre class="programlisting">HOST-1.EXAMPLE.   A  1.2.3.1
8981 HOST-1.EXAMPLE.   MX 0 .
8982 HOST-2.EXAMPLE.   A  1.2.3.2
8983 HOST-2.EXAMPLE.   MX 0 .
8984 HOST-3.EXAMPLE.   A  1.2.3.3
8985 HOST-3.EXAMPLE.   MX 0 .
8986 ...
8987 HOST-127.EXAMPLE. A  1.2.3.127
8988 HOST-127.EXAMPLE. MX 0 .
8989 </pre>
8990 <div class="informaltable"><table border="1">
8991 <colgroup>
8992 <col>
8993 <col>
8994 </colgroup>
8995 <tbody>
8996 <tr>
8997 <td>
8998                     <p><span><strong class="command">range</strong></span></p>
8999                   </td>
9000 <td>
9001                     <p>
9002                       This can be one of two forms: start-stop
9003                       or start-stop/step. If the first form is used, then step
9004                       is set to
9005                       1. All of start, stop and step must be positive.
9006                     </p>
9007                   </td>
9008 </tr>
9009 <tr>
9010 <td>
9011                     <p><span><strong class="command">lhs</strong></span></p>
9012                   </td>
9013 <td>
9014                     <p>This
9015                       describes the owner name of the resource records
9016                       to be created.  Any single <span><strong class="command">$</strong></span>
9017                       (dollar sign)
9018                       symbols within the <span><strong class="command">lhs</strong></span> string
9019                       are replaced by the iterator value.
9020
9021                       To get a $ in the output, you need to escape the
9022                       <span><strong class="command">$</strong></span> using a backslash
9023                       <span><strong class="command">\</strong></span>,
9024                       e.g. <span><strong class="command">\$</strong></span>. The
9025                       <span><strong class="command">$</strong></span> may optionally be followed
9026                       by modifiers which change the offset from the
9027                       iterator, field width and base.
9028
9029                       Modifiers are introduced by a
9030                       <span><strong class="command">{</strong></span> (left brace) immediately following the
9031                       <span><strong class="command">$</strong></span> as
9032                       <span><strong class="command">${offset[,width[,base]]}</strong></span>.
9033                       For example, <span><strong class="command">${-20,3,d}</strong></span>
9034                       subtracts 20 from the current value, prints the
9035                       result as a decimal in a zero-padded field of
9036                       width 3.
9037
9038                       Available output forms are decimal
9039                       (<span><strong class="command">d</strong></span>), octal
9040                       (<span><strong class="command">o</strong></span>), hexadecimal
9041                       (<span><strong class="command">x</strong></span> or <span><strong class="command">X</strong></span>
9042                       for uppercase) and nibble
9043                       (<span><strong class="command">n</strong></span> or <span><strong class="command">N</strong></span>\
9044                       for uppercase).  The default modifier is
9045                       <span><strong class="command">${0,0,d}</strong></span>.  If the
9046                       <span><strong class="command">lhs</strong></span> is not absolute, the
9047                       current <span><strong class="command">$ORIGIN</strong></span> is appended
9048                       to the name.
9049                     </p>
9050                     <p>
9051                       In nibble mode the value will be treated as
9052                       if it was a reversed hexadecimal string
9053                       with each hexadecimal digit as a separate
9054                       label.  The width field includes the label
9055                       separator.
9056                     </p>
9057                     <p>
9058                       For compatibility with earlier versions,
9059                       <span><strong class="command">$$</strong></span> is still recognized as
9060                       indicating a literal $ in the output.
9061                     </p>
9062                   </td>
9063 </tr>
9064 <tr>
9065 <td>
9066                     <p><span><strong class="command">ttl</strong></span></p>
9067                   </td>
9068 <td>
9069                     <p>
9070                       Specifies the time-to-live of the generated records. If
9071                       not specified this will be inherited using the
9072                       normal TTL inheritance rules.
9073                     </p>
9074                     <p><span><strong class="command">class</strong></span>
9075                       and <span><strong class="command">ttl</strong></span> can be
9076                       entered in either order.
9077                     </p>
9078                   </td>
9079 </tr>
9080 <tr>
9081 <td>
9082                     <p><span><strong class="command">class</strong></span></p>
9083                   </td>
9084 <td>
9085                     <p>
9086                       Specifies the class of the generated records.
9087                       This must match the zone class if it is
9088                       specified.
9089                     </p>
9090                     <p><span><strong class="command">class</strong></span>
9091                       and <span><strong class="command">ttl</strong></span> can be
9092                       entered in either order.
9093                     </p>
9094                   </td>
9095 </tr>
9096 <tr>
9097 <td>
9098                     <p><span><strong class="command">type</strong></span></p>
9099                   </td>
9100 <td>
9101                     <p>
9102                       Any valid type.
9103                     </p>
9104                   </td>
9105 </tr>
9106 <tr>
9107 <td>
9108                     <p><span><strong class="command">rhs</strong></span></p>
9109                   </td>
9110 <td>
9111                     <p>
9112                       <span><strong class="command">rhs</strong></span>, optionally, quoted string.
9113                     </p>
9114                   </td>
9115 </tr>
9116 </tbody>
9117 </table></div>
9118 <p>
9119             The <span><strong class="command">$GENERATE</strong></span> directive is a <acronym class="acronym">BIND</acronym> extension
9120             and not part of the standard zone file format.
9121           </p>
9122 <p>
9123             BIND 8 does not support the optional TTL and CLASS fields.
9124           </p>
9125 </div>
9126 <div class="sect2" lang="en">
9127 <div class="titlepage"><div><div><h3 class="title">
9128 <a name="zonefile_format"></a>Additional File Formats</h3></div></div></div>
9129 <p>
9130             In addition to the standard textual format, BIND 9
9131             supports the ability to read or dump to zone files in
9132             other formats.  The <code class="constant">raw</code> format is
9133             currently available as an additional format.  It is a
9134             binary format representing BIND 9's internal data
9135             structure directly, thereby remarkably improving the
9136             loading time.
9137           </p>
9138 <p>
9139             For a primary server, a zone file in the
9140             <code class="constant">raw</code> format is expected to be
9141             generated from a textual zone file by the
9142             <span><strong class="command">named-compilezone</strong></span> command.  For a
9143             secondary server or for a dynamic zone, it is automatically
9144             generated (if this format is specified by the
9145             <span><strong class="command">masterfile-format</strong></span> option) when
9146             <span><strong class="command">named</strong></span> dumps the zone contents after
9147             zone transfer or when applying prior updates.
9148           </p>
9149 <p>
9150             If a zone file in a binary format needs manual modification,
9151             it first must be converted to a textual form by the
9152             <span><strong class="command">named-compilezone</strong></span> command.  All
9153             necessary modification should go to the text file, which
9154             should then be converted to the binary form by the
9155             <span><strong class="command">named-compilezone</strong></span> command again.
9156           </p>
9157 <p>
9158              Although the <code class="constant">raw</code> format uses the
9159              network byte order and avoids architecture-dependent
9160              data alignment so that it is as much portable as
9161              possible, it is primarily expected to be used inside
9162              the same single system.  In order to export a zone
9163              file in the <code class="constant">raw</code> format or make a
9164              portable backup of the file, it is recommended to
9165              convert the file to the standard textual representation.
9166           </p>
9167 </div>
9168 </div>
9169 <div class="sect1" lang="en">
9170 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
9171 <a name="statistics"></a>BIND9 Statistics</h2></div></div></div>
9172 <p>
9173           <acronym class="acronym">BIND</acronym> 9 maintains lots of statistics
9174           information and provides several interfaces for users to
9175           get access to the statistics.
9176           The available statistics include all statistics counters
9177           that were available in <acronym class="acronym">BIND</acronym> 8 and
9178           are meaningful in <acronym class="acronym">BIND</acronym> 9,
9179           and other information that is considered useful.
9180         </p>
9181 <p>
9182           The statistics information is categorized into the following
9183           sections.
9184         </p>
9185 <div class="informaltable"><table border="1">
9186 <colgroup>
9187 <col>
9188 <col>
9189 </colgroup>
9190 <tbody>
9191 <tr>
9192 <td>
9193                   <p>Incoming Requests</p>
9194                 </td>
9195 <td>
9196                   <p>
9197                     The number of incoming DNS requests for each OPCODE.
9198                   </p>
9199                 </td>
9200 </tr>
9201 <tr>
9202 <td>
9203                   <p>Incoming Queries</p>
9204                 </td>
9205 <td>
9206                   <p>
9207                     The number of incoming queries for each RR type.
9208                   </p>
9209                 </td>
9210 </tr>
9211 <tr>
9212 <td>
9213                   <p>Outgoing Queries</p>
9214                 </td>
9215 <td>
9216                   <p>
9217                     The number of outgoing queries for each RR
9218                     type sent from the internal resolver.
9219                     Maintained per view.
9220                   </p>
9221                 </td>
9222 </tr>
9223 <tr>
9224 <td>
9225                   <p>Name Server Statistics</p>
9226                 </td>
9227 <td>
9228                   <p>
9229                     Statistics counters about incoming request processing.
9230                   </p>
9231                 </td>
9232 </tr>
9233 <tr>
9234 <td>
9235                   <p>Zone Maintenance Statistics</p>
9236                 </td>
9237 <td>
9238                   <p>
9239                     Statistics counters regarding zone maintenance
9240                     operations such as zone transfers.
9241                   </p>
9242                 </td>
9243 </tr>
9244 <tr>
9245 <td>
9246                   <p>Resolver Statistics</p>
9247                 </td>
9248 <td>
9249                   <p>
9250                     Statistics counters about name resolution
9251                     performed in the internal resolver.
9252                     Maintained per view.
9253                   </p>
9254                 </td>
9255 </tr>
9256 <tr>
9257 <td>
9258                   <p>Cache DB RRsets</p>
9259                 </td>
9260 <td>
9261                   <p>
9262                     The number of RRsets per RR type and nonexistent
9263                     names stored in the cache database.
9264                     If the exclamation mark (!) is printed for a RR
9265                     type, it means that particular type of RRset is
9266                     known to be nonexistent (this is also known as
9267                     "NXRRSET").
9268                     Maintained per view.
9269                   </p>
9270                 </td>
9271 </tr>
9272 <tr>
9273 <td>
9274                   <p>Socket I/O Statistics</p>
9275                 </td>
9276 <td>
9277                   <p>
9278                     Statistics counters about network related events.
9279                   </p>
9280                 </td>
9281 </tr>
9282 </tbody>
9283 </table></div>
9284 <p>
9285           A subset of Name Server Statistics is collected and shown
9286           per zone for which the server has the authority when
9287           <span><strong class="command">zone-statistics</strong></span> is set to
9288           <strong class="userinput"><code>yes</code></strong>.
9289           These statistics counters are shown with their zone and view
9290           names.
9291           In some cases the view names are omitted for the default view.
9292         </p>
9293 <p>
9294           There are currently two user interfaces to get access to the
9295           statistics.
9296           One is in the plain text format dumped to the file specified
9297           by the <span><strong class="command">statistics-file</strong></span> configuration option.
9298           The other is remotely accessible via a statistics channel
9299           when the <span><strong class="command">statistics-channels</strong></span> statement
9300           is specified in the configuration file
9301           (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>.)
9302         </p>
9303 <div class="sect3" lang="en">
9304 <div class="titlepage"><div><div><h4 class="title">
9305 <a name="statsfile"></a>The Statistics File</h4></div></div></div>
9306 <p>
9307             The text format statistics dump begins with a line, like:
9308           </p>
9309 <p>
9310             <span><strong class="command">+++ Statistics Dump +++ (973798949)</strong></span>
9311           </p>
9312 <p>
9313             The number in parentheses is a standard
9314             Unix-style timestamp, measured as seconds since January 1, 1970.
9315
9316             Following
9317             that line is a set of statistics information, which is categorized
9318             as described above.
9319             Each section begins with a line, like:
9320           </p>
9321 <p>
9322             <span><strong class="command">++ Name Server Statistics ++</strong></span>
9323           </p>
9324 <p>
9325             Each section consists of lines, each containing the statistics
9326             counter value followed by its textual description.
9327             See below for available counters.
9328             For brevity, counters that have a value of 0 are not shown
9329             in the statistics file.
9330           </p>
9331 <p>
9332             The statistics dump ends with the line where the
9333             number is identical to the number in the beginning line; for example:
9334           </p>
9335 <p>
9336             <span><strong class="command">--- Statistics Dump --- (973798949)</strong></span>
9337           </p>
9338 </div>
9339 <div class="sect2" lang="en">
9340 <div class="titlepage"><div><div><h3 class="title">
9341 <a name="statistics_counters"></a>Statistics Counters</h3></div></div></div>
9342 <p>
9343             The following tables summarize statistics counters that
9344             <acronym class="acronym">BIND</acronym> 9 provides.
9345             For each row of the tables, the leftmost column is the
9346             abbreviated symbol name of that counter.
9347             These symbols are shown in the statistics information
9348             accessed via an HTTP statistics channel.
9349             The rightmost column gives the description of the counter,
9350             which is also shown in the statistics file
9351             (but, in this document, possibly with slight modification
9352             for better readability).
9353             Additional notes may also be provided in this column.
9354             When a middle column exists between these two columns,
9355             it gives the corresponding counter name of the
9356             <acronym class="acronym">BIND</acronym> 8 statistics, if applicable.
9357           </p>
9358 <div class="sect3" lang="en">
9359 <div class="titlepage"><div><div><h4 class="title">
9360 <a name="id2599229"></a>Name Server Statistics Counters</h4></div></div></div>
9361 <div class="informaltable"><table border="1">
9362 <colgroup>
9363 <col>
9364 <col>
9365 <col>
9366 </colgroup>
9367 <tbody>
9368 <tr>
9369 <td>
9370                       <p>
9371                         <span class="emphasis"><em>Symbol</em></span>
9372                       </p>
9373                     </td>
9374 <td>
9375                       <p>
9376                         <span class="emphasis"><em>BIND8 Symbol</em></span>
9377                       </p>
9378                     </td>
9379 <td>
9380                       <p>
9381                         <span class="emphasis"><em>Description</em></span>
9382                       </p>
9383                     </td>
9384 </tr>
9385 <tr>
9386 <td>
9387                       <p><span><strong class="command">Requestv4</strong></span></p>
9388                     </td>
9389 <td>
9390                       <p><span><strong class="command">RQ</strong></span></p>
9391                     </td>
9392 <td>
9393                       <p>
9394                         IPv4 requests received.
9395                         Note: this also counts non query requests.
9396                       </p>
9397                     </td>
9398 </tr>
9399 <tr>
9400 <td>
9401                       <p><span><strong class="command">Requestv6</strong></span></p>
9402                     </td>
9403 <td>
9404                       <p><span><strong class="command">RQ</strong></span></p>
9405                     </td>
9406 <td>
9407                       <p>
9408                         IPv6 requests received.
9409                         Note: this also counts non query requests.
9410                       </p>
9411                     </td>
9412 </tr>
9413 <tr>
9414 <td>
9415                       <p><span><strong class="command">ReqEdns0</strong></span></p>
9416                     </td>
9417 <td>
9418                       <p><span><strong class="command"></strong></span></p>
9419                     </td>
9420 <td>
9421                       <p>
9422                         Requests with EDNS(0) received.
9423                       </p>
9424                     </td>
9425 </tr>
9426 <tr>
9427 <td>
9428                       <p><span><strong class="command">ReqBadEDNSVer</strong></span></p>
9429                     </td>
9430 <td>
9431                       <p><span><strong class="command"></strong></span></p>
9432                     </td>
9433 <td>
9434                       <p>
9435                         Requests with unsupported EDNS version received.
9436                       </p>
9437                     </td>
9438 </tr>
9439 <tr>
9440 <td>
9441                       <p><span><strong class="command">ReqTSIG</strong></span></p>
9442                     </td>
9443 <td>
9444                       <p><span><strong class="command"></strong></span></p>
9445                     </td>
9446 <td>
9447                       <p>
9448                         Requests with TSIG received.
9449                       </p>
9450                     </td>
9451 </tr>
9452 <tr>
9453 <td>
9454                       <p><span><strong class="command">ReqSIG0</strong></span></p>
9455                     </td>
9456 <td>
9457                       <p><span><strong class="command"></strong></span></p>
9458                     </td>
9459 <td>
9460                       <p>
9461                         Requests with SIG(0) received.
9462                       </p>
9463                     </td>
9464 </tr>
9465 <tr>
9466 <td>
9467                       <p><span><strong class="command">ReqBadSIG</strong></span></p>
9468                     </td>
9469 <td>
9470                       <p><span><strong class="command"></strong></span></p>
9471                     </td>
9472 <td>
9473                       <p>
9474                         Requests with invalid (TSIG or SIG(0)) signature.
9475                       </p>
9476                     </td>
9477 </tr>
9478 <tr>
9479 <td>
9480                       <p><span><strong class="command">ReqTCP</strong></span></p>
9481                     </td>
9482 <td>
9483                       <p><span><strong class="command">RTCP</strong></span></p>
9484                     </td>
9485 <td>
9486                       <p>
9487                         TCP requests received.
9488                       </p>
9489                     </td>
9490 </tr>
9491 <tr>
9492 <td>
9493                       <p><span><strong class="command">AuthQryRej</strong></span></p>
9494                     </td>
9495 <td>
9496                       <p><span><strong class="command">RUQ</strong></span></p>
9497                     </td>
9498 <td>
9499                       <p>
9500                         Authoritative (non recursive) queries rejected.
9501                       </p>
9502                     </td>
9503 </tr>
9504 <tr>
9505 <td>
9506                       <p><span><strong class="command">RecQryRej</strong></span></p>
9507                     </td>
9508 <td>
9509                       <p><span><strong class="command">RURQ</strong></span></p>
9510                     </td>
9511 <td>
9512                       <p>
9513                         Recursive queries rejected.
9514                       </p>
9515                     </td>
9516 </tr>
9517 <tr>
9518 <td>
9519                       <p><span><strong class="command">XfrRej</strong></span></p>
9520                     </td>
9521 <td>
9522                       <p><span><strong class="command">RUXFR</strong></span></p>
9523                     </td>
9524 <td>
9525                       <p>
9526                         Zone transfer requests rejected.
9527                       </p>
9528                     </td>
9529 </tr>
9530 <tr>
9531 <td>
9532                       <p><span><strong class="command">UpdateRej</strong></span></p>
9533                     </td>
9534 <td>
9535                       <p><span><strong class="command">RUUpd</strong></span></p>
9536                     </td>
9537 <td>
9538                       <p>
9539                         Dynamic update requests rejected.
9540                       </p>
9541                     </td>
9542 </tr>
9543 <tr>
9544 <td>
9545                       <p><span><strong class="command">Response</strong></span></p>
9546                     </td>
9547 <td>
9548                       <p><span><strong class="command">SAns</strong></span></p>
9549                     </td>
9550 <td>
9551                       <p>
9552                         Responses sent.
9553                       </p>
9554                     </td>
9555 </tr>
9556 <tr>
9557 <td>
9558                       <p><span><strong class="command">RespTruncated</strong></span></p>
9559                     </td>
9560 <td>
9561                       <p><span><strong class="command"></strong></span></p>
9562                     </td>
9563 <td>
9564                       <p>
9565                         Truncated responses sent.
9566                       </p>
9567                     </td>
9568 </tr>
9569 <tr>
9570 <td>
9571                       <p><span><strong class="command">RespEDNS0</strong></span></p>
9572                     </td>
9573 <td>
9574                       <p><span><strong class="command"></strong></span></p>
9575                     </td>
9576 <td>
9577                       <p>
9578                         Responses with EDNS(0) sent.
9579                       </p>
9580                     </td>
9581 </tr>
9582 <tr>
9583 <td>
9584                       <p><span><strong class="command">RespTSIG</strong></span></p>
9585                     </td>
9586 <td>
9587                       <p><span><strong class="command"></strong></span></p>
9588                     </td>
9589 <td>
9590                       <p>
9591                         Responses with TSIG sent.
9592                       </p>
9593                     </td>
9594 </tr>
9595 <tr>
9596 <td>
9597                       <p><span><strong class="command">RespSIG0</strong></span></p>
9598                     </td>
9599 <td>
9600                       <p><span><strong class="command"></strong></span></p>
9601                     </td>
9602 <td>
9603                       <p>
9604                         Responses with SIG(0) sent.
9605                       </p>
9606                     </td>
9607 </tr>
9608 <tr>
9609 <td>
9610                       <p><span><strong class="command">QrySuccess</strong></span></p>
9611                     </td>
9612 <td>
9613                       <p><span><strong class="command"></strong></span></p>
9614                     </td>
9615 <td>
9616                       <p>
9617                         Queries resulted in a successful answer.
9618                         This means the query which returns a NOERROR response
9619                         with at least one answer RR.
9620                         This corresponds to the
9621                         <span><strong class="command">success</strong></span> counter
9622                         of previous versions of
9623                         <acronym class="acronym">BIND</acronym> 9.
9624                       </p>
9625                     </td>
9626 </tr>
9627 <tr>
9628 <td>
9629                       <p><span><strong class="command">QryAuthAns</strong></span></p>
9630                     </td>
9631 <td>
9632                       <p><span><strong class="command"></strong></span></p>
9633                     </td>
9634 <td>
9635                       <p>
9636                         Queries resulted in authoritative answer.
9637                       </p>
9638                     </td>
9639 </tr>
9640 <tr>
9641 <td>
9642                       <p><span><strong class="command">QryNoauthAns</strong></span></p>
9643                     </td>
9644 <td>
9645                       <p><span><strong class="command">SNaAns</strong></span></p>
9646                     </td>
9647 <td>
9648                       <p>
9649                         Queries resulted in non authoritative answer.
9650                       </p>
9651                     </td>
9652 </tr>
9653 <tr>
9654 <td>
9655                       <p><span><strong class="command">QryReferral</strong></span></p>
9656                     </td>
9657 <td>
9658                       <p><span><strong class="command"></strong></span></p>
9659                     </td>
9660 <td>
9661                       <p>
9662                         Queries resulted in referral answer.
9663                         This corresponds to the
9664                         <span><strong class="command">referral</strong></span> counter
9665                         of previous versions of
9666                         <acronym class="acronym">BIND</acronym> 9.
9667                       </p>
9668                     </td>
9669 </tr>
9670 <tr>
9671 <td>
9672                       <p><span><strong class="command">QryNxrrset</strong></span></p>
9673                     </td>
9674 <td>
9675                       <p><span><strong class="command"></strong></span></p>
9676                     </td>
9677 <td>
9678                       <p>
9679                         Queries resulted in NOERROR responses with no data.
9680                         This corresponds to the
9681                         <span><strong class="command">nxrrset</strong></span> counter
9682                         of previous versions of
9683                         <acronym class="acronym">BIND</acronym> 9.
9684                       </p>
9685                     </td>
9686 </tr>
9687 <tr>
9688 <td>
9689                       <p><span><strong class="command">QrySERVFAIL</strong></span></p>
9690                     </td>
9691 <td>
9692                       <p><span><strong class="command">SFail</strong></span></p>
9693                     </td>
9694 <td>
9695                       <p>
9696                         Queries resulted in SERVFAIL.
9697                       </p>
9698                     </td>
9699 </tr>
9700 <tr>
9701 <td>
9702                       <p><span><strong class="command">QryFORMERR</strong></span></p>
9703                     </td>
9704 <td>
9705                       <p><span><strong class="command">SFErr</strong></span></p>
9706                     </td>
9707 <td>
9708                       <p>
9709                         Queries resulted in FORMERR.
9710                       </p>
9711                     </td>
9712 </tr>
9713 <tr>
9714 <td>
9715                       <p><span><strong class="command">QryNXDOMAIN</strong></span></p>
9716                     </td>
9717 <td>
9718                       <p><span><strong class="command">SNXD</strong></span></p>
9719                     </td>
9720 <td>
9721                       <p>
9722                         Queries resulted in NXDOMAIN.
9723                         This corresponds to the
9724                         <span><strong class="command">nxdomain</strong></span> counter
9725                         of previous versions of
9726                         <acronym class="acronym">BIND</acronym> 9.
9727                       </p>
9728                     </td>
9729 </tr>
9730 <tr>
9731 <td>
9732                       <p><span><strong class="command">QryRecursion</strong></span></p>
9733                     </td>
9734 <td>
9735                       <p><span><strong class="command">RFwdQ</strong></span></p>
9736                     </td>
9737 <td>
9738                       <p>
9739                         Queries which caused the server
9740                         to perform recursion in order to find the final answer.
9741                         This corresponds to the
9742                         <span><strong class="command">recursion</strong></span> counter
9743                         of previous versions of
9744                         <acronym class="acronym">BIND</acronym> 9.
9745                       </p>
9746                     </td>
9747 </tr>
9748 <tr>
9749 <td>
9750                       <p><span><strong class="command">QryDuplicate</strong></span></p>
9751                     </td>
9752 <td>
9753                       <p><span><strong class="command">RDupQ</strong></span></p>
9754                     </td>
9755 <td>
9756                       <p>
9757                         Queries which the server attempted to
9758                         recurse but discovered an existing query with the same
9759                         IP address, port, query ID, name, type and class
9760                         already being processed.
9761                         This corresponds to the
9762                         <span><strong class="command">duplicate</strong></span> counter
9763                         of previous versions of
9764                         <acronym class="acronym">BIND</acronym> 9.
9765                       </p>
9766                     </td>
9767 </tr>
9768 <tr>
9769 <td>
9770                       <p><span><strong class="command">QryDropped</strong></span></p>
9771                     </td>
9772 <td>
9773                       <p><span><strong class="command"></strong></span></p>
9774                     </td>
9775 <td>
9776                       <p>
9777                         Recursive queries for which the server
9778                         discovered an excessive number of existing
9779                         recursive queries for the same name, type and
9780                         class and were subsequently dropped.
9781                         This is the number of dropped queries due to
9782                         the reason explained with the
9783                         <span><strong class="command">clients-per-query</strong></span>
9784                         and
9785                         <span><strong class="command">max-clients-per-query</strong></span>
9786                         options
9787                         (see the description about
9788                         <a href="Bv9ARM.ch06.html#clients-per-query"><span><strong class="command">clients-per-query</strong></span></a>.)
9789                         This corresponds to the
9790                         <span><strong class="command">dropped</strong></span> counter
9791                         of previous versions of
9792                         <acronym class="acronym">BIND</acronym> 9.
9793                       </p>
9794                     </td>
9795 </tr>
9796 <tr>
9797 <td>
9798                       <p><span><strong class="command">QryFailure</strong></span></p>
9799                     </td>
9800 <td>
9801                       <p><span><strong class="command"></strong></span></p>
9802                     </td>
9803 <td>
9804                       <p>
9805                         Other query failures.
9806                         This corresponds to the
9807                         <span><strong class="command">failure</strong></span> counter
9808                         of previous versions of
9809                         <acronym class="acronym">BIND</acronym> 9.
9810                         Note: this counter is provided mainly for
9811                         backward compatibility with the previous versions.
9812                         Normally a more fine-grained counters such as
9813                         <span><strong class="command">AuthQryRej</strong></span> and
9814                         <span><strong class="command">RecQryRej</strong></span>
9815                         that would also fall into this counter are provided,
9816                         and so this counter would not be of much
9817                         interest in practice.
9818                       </p>
9819                     </td>
9820 </tr>
9821 <tr>
9822 <td>
9823                       <p><span><strong class="command">XfrReqDone</strong></span></p>
9824                     </td>
9825 <td>
9826                       <p><span><strong class="command"></strong></span></p>
9827                     </td>
9828 <td>
9829                       <p>
9830                         Requested zone transfers completed.
9831                       </p>
9832                     </td>
9833 </tr>
9834 <tr>
9835 <td>
9836                       <p><span><strong class="command">UpdateReqFwd</strong></span></p>
9837                     </td>
9838 <td>
9839                       <p><span><strong class="command"></strong></span></p>
9840                     </td>
9841 <td>
9842                       <p>
9843                         Update requests forwarded.
9844                       </p>
9845                     </td>
9846 </tr>
9847 <tr>
9848 <td>
9849                       <p><span><strong class="command">UpdateRespFwd</strong></span></p>
9850                     </td>
9851 <td>
9852                       <p><span><strong class="command"></strong></span></p>
9853                     </td>
9854 <td>
9855                       <p>
9856                         Update responses forwarded.
9857                       </p>
9858                     </td>
9859 </tr>
9860 <tr>
9861 <td>
9862                       <p><span><strong class="command">UpdateFwdFail</strong></span></p>
9863                     </td>
9864 <td>
9865                       <p><span><strong class="command"></strong></span></p>
9866                     </td>
9867 <td>
9868                       <p>
9869                         Dynamic update forward failed.
9870                       </p>
9871                     </td>
9872 </tr>
9873 <tr>
9874 <td>
9875                       <p><span><strong class="command">UpdateDone</strong></span></p>
9876                     </td>
9877 <td>
9878                       <p><span><strong class="command"></strong></span></p>
9879                     </td>
9880 <td>
9881                       <p>
9882                         Dynamic updates completed.
9883                       </p>
9884                     </td>
9885 </tr>
9886 <tr>
9887 <td>
9888                       <p><span><strong class="command">UpdateFail</strong></span></p>
9889                     </td>
9890 <td>
9891                       <p><span><strong class="command"></strong></span></p>
9892                     </td>
9893 <td>
9894                       <p>
9895                         Dynamic updates failed.
9896                       </p>
9897                     </td>
9898 </tr>
9899 <tr>
9900 <td>
9901                       <p><span><strong class="command">UpdateBadPrereq</strong></span></p>
9902                     </td>
9903 <td>
9904                       <p><span><strong class="command"></strong></span></p>
9905                     </td>
9906 <td>
9907                       <p>
9908                         Dynamic updates rejected due to prerequisite failure.
9909                       </p>
9910                     </td>
9911 </tr>
9912 </tbody>
9913 </table></div>
9914 </div>
9915 <div class="sect3" lang="en">
9916 <div class="titlepage"><div><div><h4 class="title">
9917 <a name="id2600702"></a>Zone Maintenance Statistics Counters</h4></div></div></div>
9918 <div class="informaltable"><table border="1">
9919 <colgroup>
9920 <col>
9921 <col>
9922 </colgroup>
9923 <tbody>
9924 <tr>
9925 <td>
9926                       <p>
9927                         <span class="emphasis"><em>Symbol</em></span>
9928                       </p>
9929                     </td>
9930 <td>
9931                       <p>
9932                         <span class="emphasis"><em>Description</em></span>
9933                       </p>
9934                     </td>
9935 </tr>
9936 <tr>
9937 <td>
9938                       <p><span><strong class="command">NotifyOutv4</strong></span></p>
9939                     </td>
9940 <td>
9941                       <p>
9942                         IPv4 notifies sent.
9943                       </p>
9944                     </td>
9945 </tr>
9946 <tr>
9947 <td>
9948                       <p><span><strong class="command">NotifyOutv6</strong></span></p>
9949                     </td>
9950 <td>
9951                       <p>
9952                         IPv6 notifies sent.
9953                       </p>
9954                     </td>
9955 </tr>
9956 <tr>
9957 <td>
9958                       <p><span><strong class="command">NotifyInv4</strong></span></p>
9959                     </td>
9960 <td>
9961                       <p>
9962                         IPv4 notifies received.
9963                       </p>
9964                     </td>
9965 </tr>
9966 <tr>
9967 <td>
9968                       <p><span><strong class="command">NotifyInv6</strong></span></p>
9969                     </td>
9970 <td>
9971                       <p>
9972                         IPv6 notifies received.
9973                       </p>
9974                     </td>
9975 </tr>
9976 <tr>
9977 <td>
9978                       <p><span><strong class="command">NotifyRej</strong></span></p>
9979                     </td>
9980 <td>
9981                       <p>
9982                         Incoming notifies rejected.
9983                       </p>
9984                     </td>
9985 </tr>
9986 <tr>
9987 <td>
9988                       <p><span><strong class="command">SOAOutv4</strong></span></p>
9989                     </td>
9990 <td>
9991                       <p>
9992                         IPv4 SOA queries sent.
9993                       </p>
9994                     </td>
9995 </tr>
9996 <tr>
9997 <td>
9998                       <p><span><strong class="command">SOAOutv6</strong></span></p>
9999                     </td>
10000 <td>
10001                       <p>
10002                         IPv6 SOA queries sent.
10003                       </p>
10004                     </td>
10005 </tr>
10006 <tr>
10007 <td>
10008                       <p><span><strong class="command">AXFRReqv4</strong></span></p>
10009                     </td>
10010 <td>
10011                       <p>
10012                         IPv4 AXFR requested.
10013                       </p>
10014                     </td>
10015 </tr>
10016 <tr>
10017 <td>
10018                       <p><span><strong class="command">AXFRReqv6</strong></span></p>
10019                     </td>
10020 <td>
10021                       <p>
10022                         IPv6 AXFR requested.
10023                       </p>
10024                     </td>
10025 </tr>
10026 <tr>
10027 <td>
10028                       <p><span><strong class="command">IXFRReqv4</strong></span></p>
10029                     </td>
10030 <td>
10031                       <p>
10032                         IPv4 IXFR requested.
10033                       </p>
10034                     </td>
10035 </tr>
10036 <tr>
10037 <td>
10038                       <p><span><strong class="command">IXFRReqv6</strong></span></p>
10039                     </td>
10040 <td>
10041                       <p>
10042                         IPv6 IXFR requested.
10043                       </p>
10044                     </td>
10045 </tr>
10046 <tr>
10047 <td>
10048                       <p><span><strong class="command">XfrSuccess</strong></span></p>
10049                     </td>
10050 <td>
10051                       <p>
10052                         Zone transfer requests succeeded.
10053                       </p>
10054                     </td>
10055 </tr>
10056 <tr>
10057 <td>
10058                       <p><span><strong class="command">XfrFail</strong></span></p>
10059                     </td>
10060 <td>
10061                       <p>
10062                         Zone transfer requests failed.
10063                       </p>
10064                     </td>
10065 </tr>
10066 </tbody>
10067 </table></div>
10068 </div>
10069 <div class="sect3" lang="en">
10070 <div class="titlepage"><div><div><h4 class="title">
10071 <a name="id2601154"></a>Resolver Statistics Counters</h4></div></div></div>
10072 <div class="informaltable"><table border="1">
10073 <colgroup>
10074 <col>
10075 <col>
10076 <col>
10077 </colgroup>
10078 <tbody>
10079 <tr>
10080 <td>
10081                       <p>
10082                         <span class="emphasis"><em>Symbol</em></span>
10083                       </p>
10084                     </td>
10085 <td>
10086                       <p>
10087                         <span class="emphasis"><em>BIND8 Symbol</em></span>
10088                       </p>
10089                     </td>
10090 <td>
10091                       <p>
10092                         <span class="emphasis"><em>Description</em></span>
10093                       </p>
10094                     </td>
10095 </tr>
10096 <tr>
10097 <td>
10098                       <p><span><strong class="command">Queryv4</strong></span></p>
10099                     </td>
10100 <td>
10101                       <p><span><strong class="command">SFwdQ</strong></span></p>
10102                     </td>
10103 <td>
10104                       <p>
10105                         IPv4 queries sent.
10106                       </p>
10107                     </td>
10108 </tr>
10109 <tr>
10110 <td>
10111                       <p><span><strong class="command">Queryv6</strong></span></p>
10112                     </td>
10113 <td>
10114                       <p><span><strong class="command">SFwdQ</strong></span></p>
10115                     </td>
10116 <td>
10117                       <p>
10118                         IPv6 queries sent.
10119                       </p>
10120                     </td>
10121 </tr>
10122 <tr>
10123 <td>
10124                       <p><span><strong class="command">Responsev4</strong></span></p>
10125                     </td>
10126 <td>
10127                       <p><span><strong class="command">RR</strong></span></p>
10128                     </td>
10129 <td>
10130                       <p>
10131                         IPv4 responses received.
10132                       </p>
10133                     </td>
10134 </tr>
10135 <tr>
10136 <td>
10137                       <p><span><strong class="command">Responsev6</strong></span></p>
10138                     </td>
10139 <td>
10140                       <p><span><strong class="command">RR</strong></span></p>
10141                     </td>
10142 <td>
10143                       <p>
10144                         IPv6 responses received.
10145                       </p>
10146                     </td>
10147 </tr>
10148 <tr>
10149 <td>
10150                       <p><span><strong class="command">NXDOMAIN</strong></span></p>
10151                     </td>
10152 <td>
10153                       <p><span><strong class="command">RNXD</strong></span></p>
10154                     </td>
10155 <td>
10156                       <p>
10157                         NXDOMAIN received.
10158                       </p>
10159                     </td>
10160 </tr>
10161 <tr>
10162 <td>
10163                       <p><span><strong class="command">SERVFAIL</strong></span></p>
10164                     </td>
10165 <td>
10166                       <p><span><strong class="command">RFail</strong></span></p>
10167                     </td>
10168 <td>
10169                       <p>
10170                         SERVFAIL received.
10171                       </p>
10172                     </td>
10173 </tr>
10174 <tr>
10175 <td>
10176                       <p><span><strong class="command">FORMERR</strong></span></p>
10177                     </td>
10178 <td>
10179                       <p><span><strong class="command">RFErr</strong></span></p>
10180                     </td>
10181 <td>
10182                       <p>
10183                         FORMERR received.
10184                       </p>
10185                     </td>
10186 </tr>
10187 <tr>
10188 <td>
10189                       <p><span><strong class="command">OtherError</strong></span></p>
10190                     </td>
10191 <td>
10192                       <p><span><strong class="command">RErr</strong></span></p>
10193                     </td>
10194 <td>
10195                       <p>
10196                         Other errors received.
10197                       </p>
10198                     </td>
10199 </tr>
10200 <tr>
10201 <td>
10202                       <p><span><strong class="command">EDNS0Fail</strong></span></p>
10203                                                  </td>
10204 <td>
10205                       <p><span><strong class="command"></strong></span></p>
10206                     </td>
10207 <td>
10208                       <p>
10209                         EDNS(0) query failures.
10210                       </p>
10211                     </td>
10212 </tr>
10213 <tr>
10214 <td>
10215                       <p><span><strong class="command">Mismatch</strong></span></p>
10216                     </td>
10217 <td>
10218                       <p><span><strong class="command">RDupR</strong></span></p>
10219                     </td>
10220 <td>
10221                       <p>
10222                         Mismatch responses received.
10223                         The DNS ID, response's source address,
10224                         and/or the response's source port does not
10225                         match what was expected.
10226                         (The port must be 53 or as defined by
10227                         the <span><strong class="command">port</strong></span> option.)
10228                         This may be an indication of a cache
10229                         poisoning attempt.
10230                       </p>
10231                     </td>
10232 </tr>
10233 <tr>
10234 <td>
10235                       <p><span><strong class="command">Truncated</strong></span></p>
10236                     </td>
10237 <td>
10238                       <p><span><strong class="command"></strong></span></p>
10239                     </td>
10240 <td>
10241                       <p>
10242                         Truncated responses received.
10243                       </p>
10244                     </td>
10245 </tr>
10246 <tr>
10247 <td>
10248                       <p><span><strong class="command">Lame</strong></span></p>
10249                     </td>
10250 <td>
10251                       <p><span><strong class="command">RLame</strong></span></p>
10252                     </td>
10253 <td>
10254                       <p>
10255                         Lame delegations received.
10256                       </p>
10257                     </td>
10258 </tr>
10259 <tr>
10260 <td>
10261                       <p><span><strong class="command">Retry</strong></span></p>
10262                     </td>
10263 <td>
10264                       <p><span><strong class="command">SDupQ</strong></span></p>
10265                     </td>
10266 <td>
10267                       <p>
10268                         Query retries performed.
10269                       </p>
10270                     </td>
10271 </tr>
10272 <tr>
10273 <td>
10274                       <p><span><strong class="command">QueryAbort</strong></span></p>
10275                     </td>
10276 <td>
10277                       <p><span><strong class="command"></strong></span></p>
10278                     </td>
10279 <td>
10280                       <p>
10281                         Queries aborted due to quota control.
10282                       </p>
10283                     </td>
10284 </tr>
10285 <tr>
10286 <td>
10287                       <p><span><strong class="command">QuerySockFail</strong></span></p>
10288                     </td>
10289 <td>
10290                       <p><span><strong class="command"></strong></span></p>
10291                     </td>
10292 <td>
10293                       <p>
10294                         Failures in opening query sockets.
10295                         One common reason for such failures is a
10296                         failure of opening a new socket due to a
10297                         limitation on file descriptors.
10298                       </p>
10299                     </td>
10300 </tr>
10301 <tr>
10302 <td>
10303                       <p><span><strong class="command">QueryTimeout</strong></span></p>
10304                     </td>
10305 <td>
10306                       <p><span><strong class="command"></strong></span></p>
10307                     </td>
10308 <td>
10309                       <p>
10310                         Query timeouts.
10311                       </p>
10312                     </td>
10313 </tr>
10314 <tr>
10315 <td>
10316                       <p><span><strong class="command">GlueFetchv4</strong></span></p>
10317                     </td>
10318 <td>
10319                       <p><span><strong class="command">SSysQ</strong></span></p>
10320                     </td>
10321 <td>
10322                       <p>
10323                         IPv4 NS address fetches invoked.
10324                       </p>
10325                     </td>
10326 </tr>
10327 <tr>
10328 <td>
10329                       <p><span><strong class="command">GlueFetchv6</strong></span></p>
10330                     </td>
10331 <td>
10332                       <p><span><strong class="command">SSysQ</strong></span></p>
10333                     </td>
10334 <td>
10335                       <p>
10336                         IPv6 NS address fetches invoked.
10337                       </p>
10338                     </td>
10339 </tr>
10340 <tr>
10341 <td>
10342                       <p><span><strong class="command">GlueFetchv4Fail</strong></span></p>
10343                     </td>
10344 <td>
10345                       <p><span><strong class="command"></strong></span></p>
10346                     </td>
10347 <td>
10348                       <p>
10349                         IPv4 NS address fetch failed.
10350                       </p>
10351                     </td>
10352 </tr>
10353 <tr>
10354 <td>
10355                       <p><span><strong class="command">GlueFetchv6Fail</strong></span></p>
10356                     </td>
10357 <td>
10358                       <p><span><strong class="command"></strong></span></p>
10359                     </td>
10360 <td>
10361                       <p>
10362                         IPv6 NS address fetch failed.
10363                       </p>
10364                     </td>
10365 </tr>
10366 <tr>
10367 <td>
10368                       <p><span><strong class="command">ValAttempt</strong></span></p>
10369                     </td>
10370 <td>
10371                       <p><span><strong class="command"></strong></span></p>
10372                     </td>
10373 <td>
10374                       <p>
10375                         DNSSEC validation attempted.
10376                       </p>
10377                     </td>
10378 </tr>
10379 <tr>
10380 <td>
10381                       <p><span><strong class="command">ValOk</strong></span></p>
10382                     </td>
10383 <td>
10384                       <p><span><strong class="command"></strong></span></p>
10385                     </td>
10386 <td>
10387                       <p>
10388                         DNSSEC validation succeeded.
10389                       </p>
10390                     </td>
10391 </tr>
10392 <tr>
10393 <td>
10394                       <p><span><strong class="command">ValNegOk</strong></span></p>
10395                     </td>
10396 <td>
10397                       <p><span><strong class="command"></strong></span></p>
10398                     </td>
10399 <td>
10400                       <p>
10401                         DNSSEC validation on negative information succeeded.
10402                       </p>
10403                     </td>
10404 </tr>
10405 <tr>
10406 <td>
10407                       <p><span><strong class="command">ValFail</strong></span></p>
10408                     </td>
10409 <td>
10410                       <p><span><strong class="command"></strong></span></p>
10411                     </td>
10412 <td>
10413                       <p>
10414                         DNSSEC validation failed.
10415                       </p>
10416                     </td>
10417 </tr>
10418 <tr>
10419 <td>
10420                       <p><span><strong class="command">QryRTTnn</strong></span></p>
10421                     </td>
10422 <td>
10423                       <p><span><strong class="command"></strong></span></p>
10424                     </td>
10425 <td>
10426                       <p>
10427                         Frequency table on round trip times (RTTs) of
10428                         queries.
10429                         Each <span><strong class="command">nn</strong></span> specifies the corresponding
10430                         frequency.
10431                         In the sequence of
10432                         <span><strong class="command">nn_1</strong></span>,
10433                         <span><strong class="command">nn_2</strong></span>,
10434                         ...,
10435                         <span><strong class="command">nn_m</strong></span>,
10436                         the value of <span><strong class="command">nn_i</strong></span> is the
10437                         number of queries whose RTTs are between
10438                         <span><strong class="command">nn_(i-1)</strong></span> (inclusive) and
10439                         <span><strong class="command">nn_i</strong></span> (exclusive) milliseconds.
10440                         For the sake of convenience we define
10441                         <span><strong class="command">nn_0</strong></span> to be 0.
10442                         The last entry should be represented as
10443                         <span><strong class="command">nn_m+</strong></span>, which means the
10444                         number of queries whose RTTs are equal to or over
10445                         <span><strong class="command">nn_m</strong></span> milliseconds.
10446                       </p>
10447                     </td>
10448 </tr>
10449 </tbody>
10450 </table></div>
10451 </div>
10452 <div class="sect3" lang="en">
10453 <div class="titlepage"><div><div><h4 class="title">
10454 <a name="id2602312"></a>Socket I/O Statistics Counters</h4></div></div></div>
10455 <p>
10456               Socket I/O statistics counters are defined per socket
10457               types, which are
10458               <span><strong class="command">UDP4</strong></span> (UDP/IPv4),
10459               <span><strong class="command">UDP6</strong></span> (UDP/IPv6),
10460               <span><strong class="command">TCP4</strong></span> (TCP/IPv4),
10461               <span><strong class="command">TCP6</strong></span> (TCP/IPv6),
10462               <span><strong class="command">Unix</strong></span> (Unix Domain), and
10463               <span><strong class="command">FDwatch</strong></span> (sockets opened outside the
10464               socket module).
10465               In the following table <span><strong class="command">&lt;TYPE&gt;</strong></span>
10466               represents a socket type.
10467               Not all counters are available for all socket types;
10468               exceptions are noted in the description field.
10469             </p>
10470 <div class="informaltable"><table border="1">
10471 <colgroup>
10472 <col>
10473 <col>
10474 </colgroup>
10475 <tbody>
10476 <tr>
10477 <td>
10478                       <p>
10479                         <span class="emphasis"><em>Symbol</em></span>
10480                       </p>
10481                     </td>
10482 <td>
10483                       <p>
10484                         <span class="emphasis"><em>Description</em></span>
10485                       </p>
10486                     </td>
10487 </tr>
10488 <tr>
10489 <td>
10490                       <p><span><strong class="command">&lt;TYPE&gt;Open</strong></span></p>
10491                     </td>
10492 <td>
10493                       <p>
10494                         Sockets opened successfully.
10495                         This counter is not applicable to the
10496                         <span><strong class="command">FDwatch</strong></span> type.
10497                       </p>
10498                     </td>
10499 </tr>
10500 <tr>
10501 <td>
10502                       <p><span><strong class="command">&lt;TYPE&gt;OpenFail</strong></span></p>
10503                     </td>
10504 <td>
10505                       <p>
10506                         Failures of opening sockets.
10507                         This counter is not applicable to the
10508                         <span><strong class="command">FDwatch</strong></span> type.
10509                       </p>
10510                     </td>
10511 </tr>
10512 <tr>
10513 <td>
10514                       <p><span><strong class="command">&lt;TYPE&gt;Close</strong></span></p>
10515                     </td>
10516 <td>
10517                       <p>
10518                         Sockets closed.
10519                       </p>
10520                     </td>
10521 </tr>
10522 <tr>
10523 <td>
10524                       <p><span><strong class="command">&lt;TYPE&gt;BindFail</strong></span></p>
10525                     </td>
10526 <td>
10527                       <p>
10528                         Failures of binding sockets.
10529                       </p>
10530                     </td>
10531 </tr>
10532 <tr>
10533 <td>
10534                       <p><span><strong class="command">&lt;TYPE&gt;ConnFail</strong></span></p>
10535                     </td>
10536 <td>
10537                       <p>
10538                         Failures of connecting sockets.
10539                       </p>
10540                     </td>
10541 </tr>
10542 <tr>
10543 <td>
10544                       <p><span><strong class="command">&lt;TYPE&gt;Conn</strong></span></p>
10545                     </td>
10546 <td>
10547                       <p>
10548                         Connections established successfully.
10549                       </p>
10550                     </td>
10551 </tr>
10552 <tr>
10553 <td>
10554                       <p><span><strong class="command">&lt;TYPE&gt;AcceptFail</strong></span></p>
10555                     </td>
10556 <td>
10557                       <p>
10558                         Failures of accepting incoming connection requests.
10559                         This counter is not applicable to the
10560                         <span><strong class="command">UDP</strong></span> and
10561                         <span><strong class="command">FDwatch</strong></span> types.
10562                       </p>
10563                     </td>
10564 </tr>
10565 <tr>
10566 <td>
10567                       <p><span><strong class="command">&lt;TYPE&gt;Accept</strong></span></p>
10568                     </td>
10569 <td>
10570                       <p>
10571                         Incoming connections successfully accepted.
10572                         This counter is not applicable to the
10573                         <span><strong class="command">UDP</strong></span> and
10574                         <span><strong class="command">FDwatch</strong></span> types.
10575                       </p>
10576                     </td>
10577 </tr>
10578 <tr>
10579 <td>
10580                       <p><span><strong class="command">&lt;TYPE&gt;SendErr</strong></span></p>
10581                     </td>
10582 <td>
10583                       <p>
10584                         Errors in socket send operations.
10585                         This counter corresponds
10586                         to <span><strong class="command">SErr</strong></span> counter of
10587                         <span><strong class="command">BIND</strong></span> 8.
10588                       </p>
10589                     </td>
10590 </tr>
10591 <tr>
10592 <td>
10593                       <p><span><strong class="command">&lt;TYPE&gt;RecvErr</strong></span></p>
10594                     </td>
10595 <td>
10596                       <p>
10597                         Errors in socket receive operations.
10598                         This includes errors of send operations on a
10599                         connected UDP socket notified by an ICMP error
10600                         message.
10601                       </p>
10602                     </td>
10603 </tr>
10604 </tbody>
10605 </table></div>
10606 </div>
10607 <div class="sect3" lang="en">
10608 <div class="titlepage"><div><div><h4 class="title">
10609 <a name="id2602685"></a>Compatibility with <span class="emphasis"><em>BIND</em></span> 8 Counters</h4></div></div></div>
10610 <p>
10611               Most statistics counters that were available
10612               in <span><strong class="command">BIND</strong></span> 8 are also supported in
10613               <span><strong class="command">BIND</strong></span> 9 as shown in the above tables.
10614               Here are notes about other counters that do not appear
10615               in these tables.
10616             </p>
10617 <div class="variablelist"><dl>
10618 <dt><span class="term"><span><strong class="command">RFwdR,SFwdR</strong></span></span></dt>
10619 <dd><p>
10620                     These counters are not supported
10621                     because <span><strong class="command">BIND</strong></span> 9 does not adopt
10622                     the notion of <span class="emphasis"><em>forwarding</em></span>
10623                     as <span><strong class="command">BIND</strong></span> 8 did.
10624                   </p></dd>
10625 <dt><span class="term"><span><strong class="command">RAXFR</strong></span></span></dt>
10626 <dd><p>
10627                     This counter is accessible in the Incoming Queries section.
10628                   </p></dd>
10629 <dt><span class="term"><span><strong class="command">RIQ</strong></span></span></dt>
10630 <dd><p>
10631                     This counter is accessible in the Incoming Requests section.
10632                   </p></dd>
10633 <dt><span class="term"><span><strong class="command">ROpts</strong></span></span></dt>
10634 <dd><p>
10635                     This counter is not supported
10636                     because <span><strong class="command">BIND</strong></span> 9 does not care
10637                     about IP options in the first place.
10638                   </p></dd>
10639 </dl></div>
10640 </div>
10641 </div>
10642 </div>
10643 </div>
10644 <div class="navfooter">
10645 <hr>
10646 <table width="100%" summary="Navigation footer">
10647 <tr>
10648 <td width="40%" align="left">
10649 <a accesskey="p" href="Bv9ARM.ch05.html">Prev</a> </td>
10650 <td width="20%" align="center"> </td>
10651 <td width="40%" align="right"> <a accesskey="n" href="Bv9ARM.ch07.html">Next</a>
10652 </td>
10653 </tr>
10654 <tr>
10655 <td width="40%" align="left" valign="top">Chapter 5. The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver </td>
10656 <td width="20%" align="center"><a accesskey="h" href="Bv9ARM.html">Home</a></td>
10657 <td width="40%" align="right" valign="top"> Chapter 7. <acronym class="acronym">BIND</acronym> 9 Security Considerations</td>
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