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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#id2574332">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#id2574986"><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#id2575176"><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#id2575467"><span><strong class="command">include</strong></span> Statement Grammar</a></span></dt>
  62 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575484"><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#id2575576"><span><strong class="command">key</strong></span> Statement Grammar</a></span></dt>
  65 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575600"><span><strong class="command">key</strong></span> Statement Definition and Usage</a></span></dt>
  66 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575758"><span><strong class="command">logging</strong></span> Statement Grammar</a></span></dt>
  67 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575884"><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#id2577910"><span><strong class="command">lwres</strong></span> Statement Grammar</a></span></dt>
  70 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577984"><span><strong class="command">lwres</strong></span> Statement Definition and Usage</a></span></dt>
  71 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2578116"><span><strong class="command">masters</strong></span> Statement Grammar</a></span></dt>
  72 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2578160"><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#id2578174"><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#id2589481"><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#id2589689"><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#id2589736"><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#id2590162"><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#id2591713"><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#id2595116">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#id2597415">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#id2597962">Inverse Mapping in IPv4</a></span></dt>
 101 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2598157">Other Zone File Directives</a></span></dt>
 102 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2598430"><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="id2574099"></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="id2574126"></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="id2574332"></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="id2574347"></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="id2574377"></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="id2574986"></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="id2575176"></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="id2575467"></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="id2575484"></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="id2575576"></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="id2575600"></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="id2575758"></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="id2575884"></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="id2576005"></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 <tr>
1752 <td>
1753                     <p><span><strong class="command">RPZ</strong></span></p>
1754                   </td>
1755 <td>
1756                     <p>
1757                       Information about errors in response policy zone files,
1758                       rewritten responses, and at the highest
1759                       <span><strong class="command">debug</strong></span> levels, mere rewriting
1760                       attempts.
1761                     </p>
1762                   </td>
1763 </tr>
1764 </tbody>
1765 </table></div>
1766 </div>
1767 <div class="sect3" lang="en">
1768 <div class="titlepage"><div><div><h4 class="title">
1769 <a name="id2577322"></a>The <span><strong class="command">query-errors</strong></span> Category</h4></div></div></div>
1770 <p>
1771             The <span><strong class="command">query-errors</strong></span> category is
1772             specifically intended for debugging purposes: To identify
1773             why and how specific queries result in responses which
1774             indicate an error.
1775             Messages of this category are therefore only logged
1776             with <span><strong class="command">debug</strong></span> levels.
1777           </p>
1778 <p>
1779             At the debug levels of 1 or higher, each response with the
1780             rcode of SERVFAIL is logged as follows:
1781           </p>
1782 <p>
1783             <code class="computeroutput">client 127.0.0.1#61502: query failed (SERVFAIL) for www.example.com/IN/AAAA at query.c:3880</code>
1784           </p>
1785 <p>
1786             This means an error resulting in SERVFAIL was
1787             detected at line 3880 of source file
1788             <code class="filename">query.c</code>.
1789             Log messages of this level will particularly
1790             help identify the cause of SERVFAIL for an
1791             authoritative server.
1792           </p>
1793 <p>
1794             At the debug levels of 2 or higher, detailed context
1795             information of recursive resolutions that resulted in
1796             SERVFAIL is logged.
1797             The log message will look like as follows:
1798           </p>
1799 <p>
1800
1801             </p>
1802 <pre class="programlisting">
1803 fetch completed at resolver.c:2970 for www.example.com/A
1804 in 30.000183: timed out/success [domain:example.com,
1805 referral:2,restart:7,qrysent:8,timeout:5,lame:0,neterr:0,
1806 badresp:1,adberr:0,findfail:0,valfail:0]
1807             </pre>
1808 <p>
1809           </p>
1810 <p>
1811             The first part before the colon shows that a recursive
1812             resolution for AAAA records of www.example.com completed
1813             in 30.000183 seconds and the final result that led to the
1814             SERVFAIL was determined at line 2970 of source file
1815             <code class="filename">resolver.c</code>.
1816           </p>
1817 <p>
1818             The following part shows the detected final result and the
1819             latest result of DNSSEC validation.
1820             The latter is always success when no validation attempt
1821             is made.
1822             In this example, this query resulted in SERVFAIL probably
1823             because all name servers are down or unreachable, leading
1824             to a timeout in 30 seconds.
1825             DNSSEC validation was probably not attempted.
1826           </p>
1827 <p>
1828             The last part enclosed in square brackets shows statistics
1829             information collected for this particular resolution
1830             attempt.
1831             The <code class="varname">domain</code> field shows the deepest zone
1832             that the resolver reached;
1833             it is the zone where the error was finally detected.
1834             The meaning of the other fields is summarized in the
1835             following table.
1836           </p>
1837 <div class="informaltable"><table border="1">
1838 <colgroup>
1839 <col>
1840 <col>
1841 </colgroup>
1842 <tbody>
1843 <tr>
1844 <td>
1845                     <p><code class="varname">referral</code></p>
1846                   </td>
1847 <td>
1848                     <p>
1849                       The number of referrals the resolver received
1850                       throughout the resolution process.
1851                       In the above example this is 2, which are most
1852                       likely com and example.com.
1853                     </p>
1854                   </td>
1855 </tr>
1856 <tr>
1857 <td>
1858                     <p><code class="varname">restart</code></p>
1859                   </td>
1860 <td>
1861                     <p>
1862                       The number of cycles that the resolver tried
1863                       remote servers at the <code class="varname">domain</code>
1864                       zone.
1865                       In each cycle the resolver sends one query
1866                       (possibly resending it, depending on the response)
1867                       to each known name server of
1868                       the <code class="varname">domain</code> zone.
1869                     </p>
1870                   </td>
1871 </tr>
1872 <tr>
1873 <td>
1874                     <p><code class="varname">qrysent</code></p>
1875                   </td>
1876 <td>
1877                     <p>
1878                       The number of queries the resolver sent at the
1879                       <code class="varname">domain</code> zone.
1880                     </p>
1881                   </td>
1882 </tr>
1883 <tr>
1884 <td>
1885                     <p><code class="varname">timeout</code></p>
1886                   </td>
1887 <td>
1888                     <p>
1889                       The number of timeouts since the resolver
1890                       received the last response.
1891                     </p>
1892                   </td>
1893 </tr>
1894 <tr>
1895 <td>
1896                     <p><code class="varname">lame</code></p>
1897                   </td>
1898 <td>
1899                     <p>
1900                       The number of lame servers the resolver detected
1901                       at the <code class="varname">domain</code> zone.
1902                       A server is detected to be lame either by an
1903                       invalid response or as a result of lookup in
1904                       BIND9's address database (ADB), where lame
1905                       servers are cached.
1906                     </p>
1907                   </td>
1908 </tr>
1909 <tr>
1910 <td>
1911                     <p><code class="varname">neterr</code></p>
1912                   </td>
1913 <td>
1914                     <p>
1915                       The number of erroneous results that the
1916                       resolver encountered in sending queries
1917                       at the <code class="varname">domain</code> zone.
1918                       One common case is the remote server is
1919                       unreachable and the resolver receives an ICMP
1920                       unreachable error message.
1921                     </p>
1922                   </td>
1923 </tr>
1924 <tr>
1925 <td>
1926                     <p><code class="varname">badresp</code></p>
1927                   </td>
1928 <td>
1929                     <p>
1930                       The number of unexpected responses (other than
1931                       <code class="varname">lame</code>) to queries sent by the
1932                       resolver at the <code class="varname">domain</code> zone.
1933                     </p>
1934                   </td>
1935 </tr>
1936 <tr>
1937 <td>
1938                     <p><code class="varname">adberr</code></p>
1939                   </td>
1940 <td>
1941                     <p>
1942                       Failures in finding remote server addresses
1943                       of the <code class="varname">domain</code> zone in the ADB.
1944                       One common case of this is that the remote
1945                       server's name does not have any address records.
1946                     </p>
1947                   </td>
1948 </tr>
1949 <tr>
1950 <td>
1951                     <p><code class="varname">findfail</code></p>
1952                   </td>
1953 <td>
1954                     <p>
1955                       Failures of resolving remote server addresses.
1956                       This is a total number of failures throughout
1957                       the resolution process.
1958                     </p>
1959                   </td>
1960 </tr>
1961 <tr>
1962 <td>
1963                     <p><code class="varname">valfail</code></p>
1964                   </td>
1965 <td>
1966                     <p>
1967                       Failures of DNSSEC validation.
1968                       Validation failures are counted throughout
1969                       the resolution process (not limited to
1970                       the <code class="varname">domain</code> zone), but should
1971                       only happen in <code class="varname">domain</code>.
1972                     </p>
1973                   </td>
1974 </tr>
1975 </tbody>
1976 </table></div>
1977 <p>
1978             At the debug levels of 3 or higher, the same messages
1979             as those at the debug 1 level are logged for other errors
1980             than SERVFAIL.
1981             Note that negative responses such as NXDOMAIN are not
1982             regarded as errors here.
1983           </p>
1984 <p>
1985             At the debug levels of 4 or higher, the same messages
1986             as those at the debug 2 level are logged for other errors
1987             than SERVFAIL.
1988             Unlike the above case of level 3, messages are logged for
1989             negative responses.
1990             This is because any unexpected results can be difficult to
1991             debug in the recursion case.
1992           </p>
1993 </div>
1994 </div>
1995 <div class="sect2" lang="en">
1996 <div class="titlepage"><div><div><h3 class="title">
1997 <a name="id2577910"></a><span><strong class="command">lwres</strong></span> Statement Grammar</h3></div></div></div>
1998 <p>
1999            This is the grammar of the <span><strong class="command">lwres</strong></span>
2000           statement in the <code class="filename">named.conf</code> file:
2001         </p>
2002 <pre class="programlisting"><span><strong class="command">lwres</strong></span> {
2003     [<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>] ;
2004                 [<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>]
2005     [<span class="optional"> view <em class="replaceable"><code>view_name</code></em>; </span>]
2006     [<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>]
2007     [<span class="optional"> ndots <em class="replaceable"><code>number</code></em>; </span>]
2008 };
2009 </pre>
2010 </div>
2011 <div class="sect2" lang="en">
2012 <div class="titlepage"><div><div><h3 class="title">
2013 <a name="id2577984"></a><span><strong class="command">lwres</strong></span> Statement Definition and Usage</h3></div></div></div>
2014 <p>
2015           The <span><strong class="command">lwres</strong></span> statement configures the
2016           name
2017           server to also act as a lightweight resolver server. (See
2018           <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
2019           <span><strong class="command">lwres</strong></span> statements configuring
2020           lightweight resolver servers with different properties.
2021         </p>
2022 <p>
2023           The <span><strong class="command">listen-on</strong></span> statement specifies a
2024           list of
2025           addresses (and ports) that this instance of a lightweight resolver
2026           daemon
2027           should accept requests on.  If no port is specified, port 921 is
2028           used.
2029           If this statement is omitted, requests will be accepted on
2030           127.0.0.1,
2031           port 921.
2032         </p>
2033 <p>
2034           The <span><strong class="command">view</strong></span> statement binds this
2035           instance of a
2036           lightweight resolver daemon to a view in the DNS namespace, so that
2037           the
2038           response will be constructed in the same manner as a normal DNS
2039           query
2040           matching this view.  If this statement is omitted, the default view
2041           is
2042           used, and if there is no default view, an error is triggered.
2043         </p>
2044 <p>
2045           The <span><strong class="command">search</strong></span> statement is equivalent to
2046           the
2047           <span><strong class="command">search</strong></span> statement in
2048           <code class="filename">/etc/resolv.conf</code>.  It provides a
2049           list of domains
2050           which are appended to relative names in queries.
2051         </p>
2052 <p>
2053           The <span><strong class="command">ndots</strong></span> statement is equivalent to
2054           the
2055           <span><strong class="command">ndots</strong></span> statement in
2056           <code class="filename">/etc/resolv.conf</code>.  It indicates the
2057           minimum
2058           number of dots in a relative domain name that should result in an
2059           exact match lookup before search path elements are appended.
2060         </p>
2061 </div>
2062 <div class="sect2" lang="en">
2063 <div class="titlepage"><div><div><h3 class="title">
2064 <a name="id2578116"></a><span><strong class="command">masters</strong></span> Statement Grammar</h3></div></div></div>
2065 <pre class="programlisting">
2066 <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> |
2067       <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>] };
2068 </pre>
2069 </div>
2070 <div class="sect2" lang="en">
2071 <div class="titlepage"><div><div><h3 class="title">
2072 <a name="id2578160"></a><span><strong class="command">masters</strong></span> Statement Definition and
2073           Usage</h3></div></div></div>
2074 <p><span><strong class="command">masters</strong></span>
2075           lists allow for a common set of masters to be easily used by
2076           multiple stub and slave zones.
2077         </p>
2078 </div>
2079 <div class="sect2" lang="en">
2080 <div class="titlepage"><div><div><h3 class="title">
2081 <a name="id2578174"></a><span><strong class="command">options</strong></span> Statement Grammar</h3></div></div></div>
2082 <p>
2083           This is the grammar of the <span><strong class="command">options</strong></span>
2084           statement in the <code class="filename">named.conf</code> file:
2085         </p>
2086 <pre class="programlisting"><span><strong class="command">options</strong></span> {
2087     [<span class="optional"> attach-cache <em class="replaceable"><code>cache_name</code></em>; </span>]
2088     [<span class="optional"> version <em class="replaceable"><code>version_string</code></em>; </span>]
2089     [<span class="optional"> hostname <em class="replaceable"><code>hostname_string</code></em>; </span>]
2090     [<span class="optional"> server-id <em class="replaceable"><code>server_id_string</code></em>; </span>]
2091     [<span class="optional"> directory <em class="replaceable"><code>path_name</code></em>; </span>]
2092     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2093     [<span class="optional"> managed-keys-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2094     [<span class="optional"> named-xfer <em class="replaceable"><code>path_name</code></em>; </span>]
2095     [<span class="optional"> tkey-gssapi-keytab <em class="replaceable"><code>path_name</code></em>; </span>]
2096     [<span class="optional"> tkey-gssapi-credential <em class="replaceable"><code>principal</code></em>; </span>]
2097     [<span class="optional"> tkey-domain <em class="replaceable"><code>domainname</code></em>; </span>]
2098     [<span class="optional"> tkey-dhkey <em class="replaceable"><code>key_name</code></em> <em class="replaceable"><code>key_tag</code></em>; </span>]
2099     [<span class="optional"> cache-file <em class="replaceable"><code>path_name</code></em>; </span>]
2100     [<span class="optional"> dump-file <em class="replaceable"><code>path_name</code></em>; </span>]
2101     [<span class="optional"> bindkeys-file <em class="replaceable"><code>path_name</code></em>; </span>]
2102     [<span class="optional"> secroots-file <em class="replaceable"><code>path_name</code></em>; </span>]
2103     [<span class="optional"> session-keyfile <em class="replaceable"><code>path_name</code></em>; </span>]
2104     [<span class="optional"> session-keyname <em class="replaceable"><code>key_name</code></em>; </span>]
2105     [<span class="optional"> session-keyalg <em class="replaceable"><code>algorithm_id</code></em>; </span>]
2106     [<span class="optional"> memstatistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2107     [<span class="optional"> memstatistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2108     [<span class="optional"> pid-file <em class="replaceable"><code>path_name</code></em>; </span>]
2109     [<span class="optional"> recursing-file <em class="replaceable"><code>path_name</code></em>; </span>]
2110     [<span class="optional"> statistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2111     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2112     [<span class="optional"> auth-nxdomain <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2113     [<span class="optional"> deallocate-on-exit <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2114     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em>; </span>]
2115     [<span class="optional"> fake-iquery <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2116     [<span class="optional"> fetch-glue <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2117     [<span class="optional"> flush-zones-on-shutdown <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2118     [<span class="optional"> has-old-clients <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2119     [<span class="optional"> host-statistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2120     [<span class="optional"> host-statistics-max <em class="replaceable"><code>number</code></em>; </span>]
2121     [<span class="optional"> minimal-responses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2122     [<span class="optional"> multiple-cnames <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2123     [<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>]
2124     [<span class="optional"> recursion <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2125     [<span class="optional"> rfc2308-type1 <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2126     [<span class="optional"> use-id-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2127     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2128     [<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>]
2129     [<span class="optional"> dnssec-enable <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2130     [<span class="optional"> dnssec-validation (<em class="replaceable"><code>yes_or_no</code></em> | <code class="constant">auto</code>); </span>]
2131     [<span class="optional"> dnssec-lookaside ( <em class="replaceable"><code>auto</code></em> |
2132                         <em class="replaceable"><code>no</code></em> |
2133                         <em class="replaceable"><code>domain</code></em> trust-anchor <em class="replaceable"><code>domain</code></em> ); </span>]
2134     [<span class="optional"> dnssec-must-be-secure <em class="replaceable"><code>domain yes_or_no</code></em>; </span>]
2135     [<span class="optional"> dnssec-accept-expired <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2136     [<span class="optional"> forward ( <em class="replaceable"><code>only</code></em> | <em class="replaceable"><code>first</code></em> ); </span>]
2137     [<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>]
2138     [<span class="optional"> dual-stack-servers [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] {
2139         ( <em class="replaceable"><code>domain_name</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] |
2140           <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ) ;
2141         ... }; </span>]
2142     [<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> )
2143         ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2144     [<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>]
2145     [<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>]
2146     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2147     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2148     [<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>]
2149     [<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>]
2150     [<span class="optional"> check-sibling <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2151     [<span class="optional"> allow-new-zones { <em class="replaceable"><code>yes_or_no</code></em> }; </span>]
2152     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2153     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2154     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2155     [<span class="optional"> allow-query-cache { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2156     [<span class="optional"> allow-query-cache-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2157     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2158     [<span class="optional"> allow-recursion { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2159     [<span class="optional"> allow-recursion-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2160     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2161     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2162     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2163     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2164     [<span class="optional"> dnssec-secure-to-insecure <em class="replaceable"><code>yes_or_no</code></em> ;</span>]
2165     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2166     [<span class="optional"> allow-v6-synthesis { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2167     [<span class="optional"> blackhole { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2168     [<span class="optional"> use-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2169     [<span class="optional"> avoid-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2170     [<span class="optional"> use-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2171     [<span class="optional"> avoid-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2172     [<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>]
2173     [<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>]
2174     [<span class="optional"> query-source ( ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2175         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
2176         [<span class="optional"> address ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2177         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
2178     [<span class="optional"> query-source-v6 ( ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2179         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
2180         [<span class="optional"> address ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2181         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
2182     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2183     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
2184     [<span class="optional"> queryport-pool-updateinterval <em class="replaceable"><code>number</code></em>; </span>]
2185     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em>; </span>]
2186     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em>; </span>]
2187     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em>; </span>]
2188     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em>; </span>]
2189     [<span class="optional"> tcp-clients <em class="replaceable"><code>number</code></em>; </span>]
2190     [<span class="optional"> reserved-sockets <em class="replaceable"><code>number</code></em>; </span>]
2191     [<span class="optional"> recursive-clients <em class="replaceable"><code>number</code></em>; </span>]
2192     [<span class="optional"> serial-query-rate <em class="replaceable"><code>number</code></em>; </span>]
2193     [<span class="optional"> serial-queries <em class="replaceable"><code>number</code></em>; </span>]
2194     [<span class="optional"> tcp-listen-queue <em class="replaceable"><code>number</code></em>; </span>]
2195     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em>; </span>]
2196     [<span class="optional"> transfers-in  <em class="replaceable"><code>number</code></em>; </span>]
2197     [<span class="optional"> transfers-out <em class="replaceable"><code>number</code></em>; </span>]
2198     [<span class="optional"> transfers-per-ns <em class="replaceable"><code>number</code></em>; </span>]
2199     [<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>]
2200     [<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>]
2201     [<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>]
2202     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
2203                              [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
2204     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2205     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
2206     [<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>]
2207     [<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>]
2208     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2209     [<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>] ;
2210                   [<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>]
2211     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em>; </span>]
2212     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
2213     [<span class="optional"> coresize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2214     [<span class="optional"> datasize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2215     [<span class="optional"> files <em class="replaceable"><code>size_spec</code></em> ; </span>]
2216     [<span class="optional"> stacksize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2217     [<span class="optional"> cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2218     [<span class="optional"> heartbeat-interval <em class="replaceable"><code>number</code></em>; </span>]
2219     [<span class="optional"> interface-interval <em class="replaceable"><code>number</code></em>; </span>]
2220     [<span class="optional"> statistics-interval <em class="replaceable"><code>number</code></em>; </span>]
2221     [<span class="optional"> topology { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2222     [<span class="optional"> sortlist { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2223     [<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>] };
2224     [<span class="optional"> lame-ttl <em class="replaceable"><code>number</code></em>; </span>]
2225     [<span class="optional"> max-ncache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2226     [<span class="optional"> max-cache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2227     [<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>]
2228     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
2229     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
2230     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
2231     [<span class="optional"> min-roots <em class="replaceable"><code>number</code></em>; </span>]
2232     [<span class="optional"> use-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2233     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2234     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2235     [<span class="optional"> treat-cr-as-space <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2236     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2237     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2238     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2239     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2240     [<span class="optional"> port <em class="replaceable"><code>ip_port</code></em>; </span>]
2241     [<span class="optional"> additional-from-auth <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2242     [<span class="optional"> additional-from-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2243     [<span class="optional"> random-device <em class="replaceable"><code>path_name</code></em> ; </span>]
2244     [<span class="optional"> max-cache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2245     [<span class="optional"> match-mapped-addresses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2246     [<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>]
2247     [<span class="optional"> filter-aaaa { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2248     [<span class="optional"> dns64 <em class="replaceable"><code>IPv6-prefix</code></em> {
2249         [<span class="optional"> clients { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2250         [<span class="optional"> mapped { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2251         [<span class="optional"> exclude { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2252         [<span class="optional"> suffix IPv6-address; </span>]
2253         [<span class="optional"> recursive-only <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2254         [<span class="optional"> break-dnssec <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2255     }; </span>];
2256     [<span class="optional"> dns64-server <em class="replaceable"><code>name</code></em> </span>]
2257     [<span class="optional"> dns64-contact <em class="replaceable"><code>name</code></em> </span>]
2258     [<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>]
2259     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2260     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2261     [<span class="optional"> root-delegation-only [<span class="optional"> exclude { <em class="replaceable"><code>namelist</code></em> } </span>] ; </span>]
2262     [<span class="optional"> querylog <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2263     [<span class="optional"> disable-algorithms <em class="replaceable"><code>domain</code></em> { <em class="replaceable"><code>algorithm</code></em>;
2264                                 [<span class="optional"> <em class="replaceable"><code>algorithm</code></em>; </span>] }; </span>]
2265     [<span class="optional"> acache-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2266     [<span class="optional"> acache-cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2267     [<span class="optional"> max-acache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2268     [<span class="optional"> clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2269     [<span class="optional"> max-clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2270     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
2271     [<span class="optional"> empty-server <em class="replaceable"><code>name</code></em> ; </span>]
2272     [<span class="optional"> empty-contact <em class="replaceable"><code>name</code></em> ; </span>]
2273     [<span class="optional"> empty-zones-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2274     [<span class="optional"> disable-empty-zone <em class="replaceable"><code>zone_name</code></em> ; </span>]
2275     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2276     [<span class="optional"> zero-no-soa-ttl-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2277     [<span class="optional"> resolver-query-timeout <em class="replaceable"><code>number</code></em> ; </span>]
2278     [<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>]
2279     [<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>]
2280     [<span class="optional"> response-policy { <em class="replaceable"><code>zone_name</code></em> [<span class="optional"> policy given | disabled | passthru | nxdomain | nodata | cname <em class="replaceable"><code>domain</code></em> </span>] ; } ; </span>]
2281 };
2282 </pre>
2283 </div>
2284 <div class="sect2" lang="en">
2285 <div class="titlepage"><div><div><h3 class="title">
2286 <a name="options"></a><span><strong class="command">options</strong></span> Statement Definition and
2287           Usage</h3></div></div></div>
2288 <p>
2289           The <span><strong class="command">options</strong></span> statement sets up global
2290           options
2291           to be used by <acronym class="acronym">BIND</acronym>. This statement
2292           may appear only
2293           once in a configuration file. If there is no <span><strong class="command">options</strong></span>
2294           statement, an options block with each option set to its default will
2295           be used.
2296         </p>
2297 <div class="variablelist"><dl>
2298 <dt><span class="term"><span><strong class="command">attach-cache</strong></span></span></dt>
2299 <dd>
2300 <p>
2301                   Allows multiple views to share a single cache
2302                   database.
2303                   Each view has its own cache database by default, but
2304                   if multiple views have the same operational policy
2305                   for name resolution and caching, those views can
2306                   share a single cache to save memory and possibly
2307                   improve resolution efficiency by using this option.
2308                 </p>
2309 <p>
2310                   The <span><strong class="command">attach-cache</strong></span> option
2311                   may also be specified in <span><strong class="command">view</strong></span>
2312                   statements, in which case it overrides the
2313                   global <span><strong class="command">attach-cache</strong></span> option.
2314                 </p>
2315 <p>
2316                   The <em class="replaceable"><code>cache_name</code></em> specifies
2317                   the cache to be shared.
2318                   When the <span><strong class="command">named</strong></span> server configures
2319                   views which are supposed to share a cache, it
2320                   creates a cache with the specified name for the
2321                   first view of these sharing views.
2322                   The rest of the views will simply refer to the
2323                   already created cache.
2324                 </p>
2325 <p>
2326                   One common configuration to share a cache would be to
2327                   allow all views to share a single cache.
2328                   This can be done by specifying
2329                   the <span><strong class="command">attach-cache</strong></span> as a global
2330                   option with an arbitrary name.
2331                 </p>
2332 <p>
2333                   Another possible operation is to allow a subset of
2334                   all views to share a cache while the others to
2335                   retain their own caches.
2336                   For example, if there are three views A, B, and C,
2337                   and only A and B should share a cache, specify the
2338                   <span><strong class="command">attach-cache</strong></span> option as a view A (or
2339                   B)'s option, referring to the other view name:
2340                 </p>
2341 <pre class="programlisting">
2342   view "A" {
2343     // this view has its own cache
2344     ...
2345   };
2346   view "B" {
2347     // this view refers to A's cache
2348     attach-cache "A";
2349   };
2350   view "C" {
2351     // this view has its own cache
2352     ...
2353   };
2354 </pre>
2355 <p>
2356                   Views that share a cache must have the same policy
2357                   on configurable parameters that may affect caching.
2358                   The current implementation requires the following
2359                   configurable options be consistent among these
2360                   views:
2361                   <span><strong class="command">check-names</strong></span>,
2362                   <span><strong class="command">cleaning-interval</strong></span>,
2363                   <span><strong class="command">dnssec-accept-expired</strong></span>,
2364                   <span><strong class="command">dnssec-validation</strong></span>,
2365                   <span><strong class="command">max-cache-ttl</strong></span>,
2366                   <span><strong class="command">max-ncache-ttl</strong></span>,
2367                   <span><strong class="command">max-cache-size</strong></span>, and
2368                   <span><strong class="command">zero-no-soa-ttl</strong></span>.
2369                 </p>
2370 <p>
2371                   Note that there may be other parameters that may
2372                   cause confusion if they are inconsistent for
2373                   different views that share a single cache.
2374                   For example, if these views define different sets of
2375                   forwarders that can return different answers for the
2376                   same question, sharing the answer does not make
2377                   sense or could even be harmful.
2378                   It is administrator's responsibility to ensure
2379                   configuration differences in different views do
2380                   not cause disruption with a shared cache.
2381                 </p>
2382 </dd>
2383 <dt><span class="term"><span><strong class="command">directory</strong></span></span></dt>
2384 <dd><p>
2385                 The working directory of the server.
2386                 Any non-absolute pathnames in the configuration file will be
2387                 taken
2388                 as relative to this directory. The default location for most
2389                 server
2390                 output files (e.g. <code class="filename">named.run</code>)
2391                 is this directory.
2392                 If a directory is not specified, the working directory
2393                 defaults to `<code class="filename">.</code>', the directory from
2394                 which the server
2395                 was started. The directory specified should be an absolute
2396                 path.
2397               </p></dd>
2398 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
2399 <dd><p>
2400                 When performing dynamic update of secure zones, the
2401                 directory where the public and private DNSSEC key files
2402                 should be found, if different than the current working
2403                 directory.  (Note that this option has no effect on the
2404                 paths for files containing non-DNSSEC keys such as
2405                 <code class="filename">bind.keys</code>,
2406                 <code class="filename">rndc.key</code> or
2407                 <code class="filename">session.key</code>.)
2408               </p></dd>
2409 <dt><span class="term"><span><strong class="command">managed-keys-directory</strong></span></span></dt>
2410 <dd><p>
2411                 The directory used to hold the files used to track managed keys.
2412                 By default it is the working directory.  It there are no
2413                 views then the file <code class="filename">managed-keys.bind</code>
2414                 otherwise a SHA256 hash of the view name is used with
2415                 <code class="filename">.mkeys</code> extension added.
2416               </p></dd>
2417 <dt><span class="term"><span><strong class="command">named-xfer</strong></span></span></dt>
2418 <dd><p>
2419                 <span class="emphasis"><em>This option is obsolete.</em></span> It
2420                 was used in <acronym class="acronym">BIND</acronym> 8 to specify
2421                 the pathname to the <span><strong class="command">named-xfer</strong></span>
2422                 program.  In <acronym class="acronym">BIND</acronym> 9, no separate
2423                 <span><strong class="command">named-xfer</strong></span> program is needed;
2424                 its functionality is built into the name server.
2425               </p></dd>
2426 <dt><span class="term"><span><strong class="command">tkey-gssapi-keytab</strong></span></span></dt>
2427 <dd><p>
2428                 The KRB5 keytab file to use for GSS-TSIG updates. If
2429                 this option is set and tkey-gssapi-credential is not
2430                 set, then updates will be allowed with any key
2431                 matching a principal in the specified keytab.
2432               </p></dd>
2433 <dt><span class="term"><span><strong class="command">tkey-gssapi-credential</strong></span></span></dt>
2434 <dd><p>
2435                 The security credential with which the server should
2436                 authenticate keys requested by the GSS-TSIG protocol.
2437                 Currently only Kerberos 5 authentication is available
2438                 and the credential is a Kerberos principal which the
2439                 server can acquire through the default system key
2440                 file, normally <code class="filename">/etc/krb5.keytab</code>.
2441                 The location keytab file can be overridden using the
2442                 tkey-gssapi-keytab option. Normally this principal is
2443                 of the form "<strong class="userinput"><code>DNS/</code></strong><code class="varname">server.domain</code>".
2444                 To use GSS-TSIG, <span><strong class="command">tkey-domain</strong></span> must
2445                 also be set if a specific keytab is not set with
2446                 tkey-gssapi-keytab.
2447               </p></dd>
2448 <dt><span class="term"><span><strong class="command">tkey-domain</strong></span></span></dt>
2449 <dd><p>
2450                 The domain appended to the names of all shared keys
2451                 generated with <span><strong class="command">TKEY</strong></span>.  When a
2452                 client requests a <span><strong class="command">TKEY</strong></span> exchange,
2453                 it may or may not specify the desired name for the
2454                 key. If present, the name of the shared key will
2455                 be <code class="varname">client specified part</code> +
2456                 <code class="varname">tkey-domain</code>.  Otherwise, the
2457                 name of the shared key will be <code class="varname">random hex
2458                 digits</code> + <code class="varname">tkey-domain</code>.
2459                 In most cases, the <span><strong class="command">domainname</strong></span>
2460                 should be the server's domain name, or an otherwise
2461                 non-existent subdomain like
2462                 "_tkey.<code class="varname">domainname</code>".  If you are
2463                 using GSS-TSIG, this variable must be defined, unless
2464                 you specify a specific keytab using tkey-gssapi-keytab.
2465               </p></dd>
2466 <dt><span class="term"><span><strong class="command">tkey-dhkey</strong></span></span></dt>
2467 <dd><p>
2468                 The Diffie-Hellman key used by the server
2469                 to generate shared keys with clients using the Diffie-Hellman
2470                 mode
2471                 of <span><strong class="command">TKEY</strong></span>. The server must be
2472                 able to load the
2473                 public and private keys from files in the working directory.
2474                 In
2475                 most cases, the keyname should be the server's host name.
2476               </p></dd>
2477 <dt><span class="term"><span><strong class="command">cache-file</strong></span></span></dt>
2478 <dd><p>
2479                 This is for testing only.  Do not use.
2480               </p></dd>
2481 <dt><span class="term"><span><strong class="command">dump-file</strong></span></span></dt>
2482 <dd><p>
2483                 The pathname of the file the server dumps
2484                 the database to when instructed to do so with
2485                 <span><strong class="command">rndc dumpdb</strong></span>.
2486                 If not specified, the default is <code class="filename">named_dump.db</code>.
2487               </p></dd>
2488 <dt><span class="term"><span><strong class="command">memstatistics-file</strong></span></span></dt>
2489 <dd><p>
2490                 The pathname of the file the server writes memory
2491                 usage statistics to on exit. If not specified,
2492                 the default is <code class="filename">named.memstats</code>.
2493               </p></dd>
2494 <dt><span class="term"><span><strong class="command">pid-file</strong></span></span></dt>
2495 <dd><p>
2496                 The pathname of the file the server writes its process ID
2497                 in. If not specified, the default is
2498                 <code class="filename">/var/run/named/named.pid</code>.
2499                 The PID file is used by programs that want to send signals to
2500                 the running
2501                 name server. Specifying <span><strong class="command">pid-file none</strong></span> disables the
2502                 use of a PID file &#8212; no file will be written and any
2503                 existing one will be removed.  Note that <span><strong class="command">none</strong></span>
2504                 is a keyword, not a filename, and therefore is not enclosed
2505                 in
2506                 double quotes.
2507               </p></dd>
2508 <dt><span class="term"><span><strong class="command">recursing-file</strong></span></span></dt>
2509 <dd><p>
2510                 The pathname of the file the server dumps
2511                 the queries that are currently recursing when instructed
2512                 to do so with <span><strong class="command">rndc recursing</strong></span>.
2513                 If not specified, the default is <code class="filename">named.recursing</code>.
2514               </p></dd>
2515 <dt><span class="term"><span><strong class="command">statistics-file</strong></span></span></dt>
2516 <dd><p>
2517                 The pathname of the file the server appends statistics
2518                 to when instructed to do so using <span><strong class="command">rndc stats</strong></span>.
2519                 If not specified, the default is <code class="filename">named.stats</code> in the
2520                 server's current directory.  The format of the file is
2521                 described
2522                 in <a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
2523               </p></dd>
2524 <dt><span class="term"><span><strong class="command">bindkeys-file</strong></span></span></dt>
2525 <dd><p>
2526                 The pathname of a file to override the built-in trusted
2527                 keys provided by <span><strong class="command">named</strong></span>.
2528                 See the discussion of <span><strong class="command">dnssec-lookaside</strong></span>
2529                 and <span><strong class="command">dnssec-validation</strong></span> for details.
2530                 If not specified, the default is
2531                 <code class="filename">/etc/bind.keys</code>.
2532               </p></dd>
2533 <dt><span class="term"><span><strong class="command">secroots-file</strong></span></span></dt>
2534 <dd><p>
2535                 The pathname of the file the server dumps
2536                 security roots to when instructed to do so with
2537                 <span><strong class="command">rndc secroots</strong></span>.
2538                 If not specified, the default is
2539                 <code class="filename">named.secroots</code>.
2540               </p></dd>
2541 <dt><span class="term"><span><strong class="command">session-keyfile</strong></span></span></dt>
2542 <dd><p>
2543                 The pathname of the file into which to write a TSIG
2544                 session key generated by <span><strong class="command">named</strong></span> for use by
2545                 <span><strong class="command">nsupdate -l</strong></span>.  If not specified, the
2546                 default is <code class="filename">/var/run/named/session.key</code>.
2547                 (See <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>, and in
2548                 particular the discussion of the
2549                 <span><strong class="command">update-policy</strong></span> statement's
2550                 <strong class="userinput"><code>local</code></strong> option for more
2551                 information about this feature.)
2552               </p></dd>
2553 <dt><span class="term"><span><strong class="command">session-keyname</strong></span></span></dt>
2554 <dd><p>
2555                 The key name to use for the TSIG session key.
2556                 If not specified, the default is "local-ddns".
2557               </p></dd>
2558 <dt><span class="term"><span><strong class="command">session-keyalg</strong></span></span></dt>
2559 <dd><p>
2560                 The algorithm to use for the TSIG session key.
2561                 Valid values are hmac-sha1, hmac-sha224, hmac-sha256,
2562                 hmac-sha384, hmac-sha512 and hmac-md5.  If not
2563                 specified, the default is hmac-sha256.
2564               </p></dd>
2565 <dt><span class="term"><span><strong class="command">port</strong></span></span></dt>
2566 <dd><p>
2567                 The UDP/TCP port number the server uses for
2568                 receiving and sending DNS protocol traffic.
2569                 The default is 53.  This option is mainly intended for server
2570                 testing;
2571                 a server using a port other than 53 will not be able to
2572                 communicate with
2573                 the global DNS.
2574               </p></dd>
2575 <dt><span class="term"><span><strong class="command">random-device</strong></span></span></dt>
2576 <dd><p>
2577                 The source of entropy to be used by the server.  Entropy is
2578                 primarily needed
2579                 for DNSSEC operations, such as TKEY transactions and dynamic
2580                 update of signed
2581                 zones.  This options specifies the device (or file) from which
2582                 to read
2583                 entropy.  If this is a file, operations requiring entropy will
2584                 fail when the
2585                 file has been exhausted.  If not specified, the default value
2586                 is
2587                 <code class="filename">/dev/random</code>
2588                 (or equivalent) when present, and none otherwise.  The
2589                 <span><strong class="command">random-device</strong></span> option takes
2590                 effect during
2591                 the initial configuration load at server startup time and
2592                 is ignored on subsequent reloads.
2593               </p></dd>
2594 <dt><span class="term"><span><strong class="command">preferred-glue</strong></span></span></dt>
2595 <dd><p>
2596                 If specified, the listed type (A or AAAA) will be emitted
2597                 before other glue
2598                 in the additional section of a query response.
2599                 The default is not to prefer any type (NONE).
2600               </p></dd>
2601 <dt>
2602 <a name="root_delegation_only"></a><span class="term"><span><strong class="command">root-delegation-only</strong></span></span>
2603 </dt>
2604 <dd>
2605 <p>
2606                 Turn on enforcement of delegation-only in TLDs
2607                 (top level domains) and root zones with an optional
2608                 exclude list.
2609               </p>
2610 <p>
2611                 DS queries are expected to be made to and be answered by
2612                 delegation only zones.  Such queries and responses are
2613                 treated as an exception to delegation-only processing
2614                 and are not converted to NXDOMAIN responses provided
2615                 a CNAME is not discovered at the query name.
2616               </p>
2617 <p>
2618                 If a delegation only zone server also serves a child
2619                 zone it is not always possible to determine whether
2620                 an answer comes from the delegation only zone or the
2621                 child zone.  SOA NS and DNSKEY records are apex
2622                 only records and a matching response that contains
2623                 these records or DS is treated as coming from a
2624                 child zone.  RRSIG records are also examined to see
2625                 if they are signed by a child zone or not.  The
2626                 authority section is also examined to see if there
2627                 is evidence that the answer is from the child zone.
2628                 Answers that are determined to be from a child zone
2629                 are not converted to NXDOMAIN responses.  Despite
2630                 all these checks there is still a possibility of
2631                 false negatives when a child zone is being served.
2632               </p>
2633 <p>
2634                 Similarly false positives can arise from empty nodes
2635                 (no records at the name) in the delegation only zone
2636                 when the query type is not ANY.
2637               </p>
2638 <p>
2639                 Note some TLDs are not delegation only (e.g. "DE", "LV",
2640                 "US" and "MUSEUM").  This list is not exhaustive.
2641               </p>
2642 <pre class="programlisting">
2643 options {
2644         root-delegation-only exclude { "de"; "lv"; "us"; "museum"; };
2645 };
2646 </pre>
2647 </dd>
2648 <dt><span class="term"><span><strong class="command">disable-algorithms</strong></span></span></dt>
2649 <dd><p>
2650                 Disable the specified DNSSEC algorithms at and below the
2651                 specified name.
2652                 Multiple <span><strong class="command">disable-algorithms</strong></span>
2653                 statements are allowed.
2654                 Only the most specific will be applied.
2655               </p></dd>
2656 <dt><span class="term"><span><strong class="command">dnssec-lookaside</strong></span></span></dt>
2657 <dd>
2658 <p>
2659                 When set, <span><strong class="command">dnssec-lookaside</strong></span> provides the
2660                 validator with an alternate method to validate DNSKEY
2661                 records at the top of a zone.  When a DNSKEY is at or
2662                 below a domain specified by the deepest
2663                 <span><strong class="command">dnssec-lookaside</strong></span>, and the normal DNSSEC
2664                 validation has left the key untrusted, the trust-anchor
2665                 will be appended to the key name and a DLV record will be
2666                 looked up to see if it can validate the key.  If the DLV
2667                 record validates a DNSKEY (similarly to the way a DS
2668                 record does) the DNSKEY RRset is deemed to be trusted.
2669               </p>
2670 <p>
2671                 If <span><strong class="command">dnssec-lookaside</strong></span> is set to
2672                 <strong class="userinput"><code>auto</code></strong>, then built-in default
2673                 values for the DLV domain and trust anchor will be
2674                 used, along with a built-in key for validation.
2675               </p>
2676 <p>
2677                 If <span><strong class="command">dnssec-lookaside</strong></span> is set to
2678                 <strong class="userinput"><code>no</code></strong>, then dnssec-lookaside
2679                 is not used.
2680               </p>
2681 <p>
2682                 The default DLV key is stored in the file
2683                 <code class="filename">bind.keys</code>;
2684                 <span><strong class="command">named</strong></span> will load that key at
2685                 startup if <span><strong class="command">dnssec-lookaside</strong></span> is set to
2686                 <code class="constant">auto</code>.  A copy of the file is
2687                 installed along with <acronym class="acronym">BIND</acronym> 9, and is
2688                 current as of the release date.  If the DLV key expires, a
2689                 new copy of <code class="filename">bind.keys</code> can be downloaded
2690                 from <a href="" target="_top">https://www.isc.org/solutions/dlv</a>.
2691               </p>
2692 <p>
2693                 (To prevent problems if <code class="filename">bind.keys</code> is
2694                 not found, the current key is also compiled in to
2695                 <span><strong class="command">named</strong></span>.  Relying on this is not
2696                 recommended, however, as it requires <span><strong class="command">named</strong></span>
2697                 to be recompiled with a new key when the DLV key expires.)
2698               </p>
2699 <p>
2700                 NOTE: <span><strong class="command">named</strong></span> only loads certain specific
2701                 keys from <code class="filename">bind.keys</code>:  those for the
2702                 DLV zone and for the DNS root zone.  The file cannot be
2703                 used to store keys for other zones.
2704               </p>
2705 </dd>
2706 <dt><span class="term"><span><strong class="command">dnssec-must-be-secure</strong></span></span></dt>
2707 <dd><p>
2708                 Specify hierarchies which must be or may not be secure
2709                 (signed and validated).  If <strong class="userinput"><code>yes</code></strong>,
2710                 then <span><strong class="command">named</strong></span> will only accept answers if
2711                 they are secure.  If <strong class="userinput"><code>no</code></strong>, then normal
2712                 DNSSEC validation applies allowing for insecure answers to
2713                 be accepted.  The specified domain must be under a
2714                 <span><strong class="command">trusted-keys</strong></span> or
2715                 <span><strong class="command">managed-keys</strong></span> statement, or
2716                 <span><strong class="command">dnssec-lookaside</strong></span> must be active.
2717               </p></dd>
2718 <dt><span class="term"><span><strong class="command">dns64</strong></span></span></dt>
2719 <dd>
2720 <p>
2721                 This directive instructs <span><strong class="command">named</strong></span> to
2722                 return mapped IPv4 addresses to AAAA queries when
2723                 there are no AAAA records.  It is intended to be
2724                 used in conjunction with a NAT64.  Each
2725                 <span><strong class="command">dns64</strong></span> defines one DNS64 prefix.
2726                 Multiple DNS64 prefixes can be defined.
2727               </p>
2728 <p>
2729                 Compatible IPv6 prefixes have lengths of 32, 40, 48, 56,
2730                 64 and 96 as per RFC 6052.
2731               </p>
2732 <p>
2733                 Additionally a reverse IP6.ARPA zone will be created for
2734                 the prefix to provide a mapping from the IP6.ARPA names
2735                 to the corresponding IN-ADDR.ARPA names using synthesized
2736                 CNAMEs.  <span><strong class="command">dns64-server</strong></span> and
2737                 <span><strong class="command">dns64-contact</strong></span> can be used to specify
2738                 the name of the server and contact for the zones. These
2739                 are settable at the view / options level.  These are
2740                 not settable on a per-prefix basis.
2741               </p>
2742 <p>
2743                 Each <span><strong class="command">dns64</strong></span> supports an optional
2744                 <span><strong class="command">clients</strong></span> ACL that determines which
2745                 clients are affected by this directive.  If not defined,
2746                 it defaults to <strong class="userinput"><code>any;</code></strong>.
2747               </p>
2748 <p>
2749                 Each <span><strong class="command">dns64</strong></span> supports an optional
2750                 <span><strong class="command">mapped</strong></span> ACL that selects which
2751                 IPv4 addresses are to be mapped in the corresponding
2752                 A RRset.  If not defined it defaults to
2753                 <strong class="userinput"><code>any;</code></strong>.
2754               </p>
2755 <p>
2756                 Normally, DNS64 won't apply to a domain name that
2757                 owns one or more AAAA records; these records will
2758                 simply be returned.  The optional
2759                 <span><strong class="command">exclude</strong></span> ACL allows specification
2760                 of a list of IPv6 addresses that will be ignored
2761                 if they appear in a domain name's AAAA records, and
2762                 DNS64 will be applied to any A records the domain
2763                 name owns.  If not defined, <span><strong class="command">exclude</strong></span>
2764                 defaults to none.
2765               </p>
2766 <p>
2767                 A optional <span><strong class="command">suffix</strong></span> can also
2768                 be defined to set the bits trailing the mapped
2769                 IPv4 address bits.  By default these bits are
2770                 set to <strong class="userinput"><code>::</code></strong>.  The bits
2771                 matching the prefix and mapped IPv4 address
2772                 must be zero.
2773               </p>
2774 <p>
2775                 If <span><strong class="command">recursive-only</strong></span> is set to
2776                 <span><strong class="command">yes</strong></span> the DNS64 synthesis will
2777                 only happen for recursive queries.  The default
2778                 is <span><strong class="command">no</strong></span>.
2779               </p>
2780 <p>
2781                 If <span><strong class="command">break-dnssec</strong></span> is set to
2782                 <span><strong class="command">yes</strong></span> the DNS64 synthesis will
2783                 happen even if the result, if validated, would
2784                 cause a DNSSEC validation failure.  If this option
2785                 is set to <span><strong class="command">no</strong></span> (the default), the DO
2786                 is set on the incoming query, and there are RRSIGs on
2787                 the applicable records, then synthesis will not happen.
2788               </p>
2789 <pre class="programlisting">
2790         acl rfc1918 { 10/8; 192.168/16; 172.16/12; };
2791
2792         dns64 64:FF9B::/96 {
2793                 clients { any; };
2794                 mapped { !rfc1918; any; };
2795                 exclude { 64:FF9B::/96; ::ffff:0000:0000/96; };
2796                 suffix ::;
2797         };
2798 </pre>
2799 </dd>
2800 </dl></div>
2801 <div class="sect3" lang="en">
2802 <div class="titlepage"><div><div><h4 class="title">
2803 <a name="boolean_options"></a>Boolean Options</h4></div></div></div>
2804 <div class="variablelist"><dl>
2805 <dt><span class="term"><span><strong class="command">allow-new-zones</strong></span></span></dt>
2806 <dd><p>
2807                   If <strong class="userinput"><code>yes</code></strong>, then zones can be
2808                   added at runtime via <span><strong class="command">rndc addzone</strong></span>
2809                   or deleted via <span><strong class="command">rndc delzone</strong></span>.
2810                   The default is <strong class="userinput"><code>no</code></strong>.
2811                 </p></dd>
2812 <dt><span class="term"><span><strong class="command">auth-nxdomain</strong></span></span></dt>
2813 <dd><p>
2814                   If <strong class="userinput"><code>yes</code></strong>, then the <span><strong class="command">AA</strong></span> bit
2815                   is always set on NXDOMAIN responses, even if the server is
2816                   not actually
2817                   authoritative. The default is <strong class="userinput"><code>no</code></strong>;
2818                   this is
2819                   a change from <acronym class="acronym">BIND</acronym> 8. If you
2820                   are using very old DNS software, you
2821                   may need to set it to <strong class="userinput"><code>yes</code></strong>.
2822                 </p></dd>
2823 <dt><span class="term"><span><strong class="command">deallocate-on-exit</strong></span></span></dt>
2824 <dd><p>
2825                   This option was used in <acronym class="acronym">BIND</acronym>
2826                   8 to enable checking
2827                   for memory leaks on exit. <acronym class="acronym">BIND</acronym> 9 ignores the option and always performs
2828                   the checks.
2829                 </p></dd>
2830 <dt><span class="term"><span><strong class="command">memstatistics</strong></span></span></dt>
2831 <dd><p>
2832                   Write memory statistics to the file specified by
2833                   <span><strong class="command">memstatistics-file</strong></span> at exit.
2834                   The default is <strong class="userinput"><code>no</code></strong> unless
2835                   '-m record' is specified on the command line in
2836                   which case it is <strong class="userinput"><code>yes</code></strong>.
2837                 </p></dd>
2838 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
2839 <dd>
2840 <p>
2841                   If <strong class="userinput"><code>yes</code></strong>, then the
2842                   server treats all zones as if they are doing zone transfers
2843                   across
2844                   a dial-on-demand dialup link, which can be brought up by
2845                   traffic
2846                   originating from this server. This has different effects
2847                   according
2848                   to zone type and concentrates the zone maintenance so that
2849                   it all
2850                   happens in a short interval, once every <span><strong class="command">heartbeat-interval</strong></span> and
2851                   hopefully during the one call. It also suppresses some of
2852                   the normal
2853                   zone maintenance traffic. The default is <strong class="userinput"><code>no</code></strong>.
2854                 </p>
2855 <p>
2856                   The <span><strong class="command">dialup</strong></span> option
2857                   may also be specified in the <span><strong class="command">view</strong></span> and
2858                   <span><strong class="command">zone</strong></span> statements,
2859                   in which case it overrides the global <span><strong class="command">dialup</strong></span>
2860                   option.
2861                 </p>
2862 <p>
2863                   If the zone is a master zone, then the server will send out a
2864                   NOTIFY
2865                   request to all the slaves (default). This should trigger the
2866                   zone serial
2867                   number check in the slave (providing it supports NOTIFY)
2868                   allowing the slave
2869                   to verify the zone while the connection is active.
2870                   The set of servers to which NOTIFY is sent can be controlled
2871                   by
2872                   <span><strong class="command">notify</strong></span> and <span><strong class="command">also-notify</strong></span>.
2873                 </p>
2874 <p>
2875                   If the
2876                   zone is a slave or stub zone, then the server will suppress
2877                   the regular
2878                   "zone up to date" (refresh) queries and only perform them
2879                   when the
2880                   <span><strong class="command">heartbeat-interval</strong></span> expires in
2881                   addition to sending
2882                   NOTIFY requests.
2883                 </p>
2884 <p>
2885                   Finer control can be achieved by using
2886                   <strong class="userinput"><code>notify</code></strong> which only sends NOTIFY
2887                   messages,
2888                   <strong class="userinput"><code>notify-passive</code></strong> which sends NOTIFY
2889                   messages and
2890                   suppresses the normal refresh queries, <strong class="userinput"><code>refresh</code></strong>
2891                   which suppresses normal refresh processing and sends refresh
2892                   queries
2893                   when the <span><strong class="command">heartbeat-interval</strong></span>
2894                   expires, and
2895                   <strong class="userinput"><code>passive</code></strong> which just disables normal
2896                   refresh
2897                   processing.
2898                 </p>
2899 <div class="informaltable"><table border="1">
2900 <colgroup>
2901 <col>
2902 <col>
2903 <col>
2904 <col>
2905 </colgroup>
2906 <tbody>
2907 <tr>
2908 <td>
2909                           <p>
2910                             dialup mode
2911                           </p>
2912                         </td>
2913 <td>
2914                           <p>
2915                             normal refresh
2916                           </p>
2917                         </td>
2918 <td>
2919                           <p>
2920                             heart-beat refresh
2921                           </p>
2922                         </td>
2923 <td>
2924                           <p>
2925                             heart-beat notify
2926                           </p>
2927                         </td>
2928 </tr>
2929 <tr>
2930 <td>
2931                           <p><span><strong class="command">no</strong></span> (default)</p>
2932                         </td>
2933 <td>
2934                           <p>
2935                             yes
2936                           </p>
2937                         </td>
2938 <td>
2939                           <p>
2940                             no
2941                           </p>
2942                         </td>
2943 <td>
2944                           <p>
2945                             no
2946                           </p>
2947                         </td>
2948 </tr>
2949 <tr>
2950 <td>
2951                           <p><span><strong class="command">yes</strong></span></p>
2952                         </td>
2953 <td>
2954                           <p>
2955                             no
2956                           </p>
2957                         </td>
2958 <td>
2959                           <p>
2960                             yes
2961                           </p>
2962                         </td>
2963 <td>
2964                           <p>
2965                             yes
2966                           </p>
2967                         </td>
2968 </tr>
2969 <tr>
2970 <td>
2971                           <p><span><strong class="command">notify</strong></span></p>
2972                         </td>
2973 <td>
2974                           <p>
2975                             yes
2976                           </p>
2977                         </td>
2978 <td>
2979                           <p>
2980                             no
2981                           </p>
2982                         </td>
2983 <td>
2984                           <p>
2985                             yes
2986                           </p>
2987                         </td>
2988 </tr>
2989 <tr>
2990 <td>
2991                           <p><span><strong class="command">refresh</strong></span></p>
2992                         </td>
2993 <td>
2994                           <p>
2995                             no
2996                           </p>
2997                         </td>
2998 <td>
2999                           <p>
3000                             yes
3001                           </p>
3002                         </td>
3003 <td>
3004                           <p>
3005                             no
3006                           </p>
3007                         </td>
3008 </tr>
3009 <tr>
3010 <td>
3011                           <p><span><strong class="command">passive</strong></span></p>
3012                         </td>
3013 <td>
3014                           <p>
3015                             no
3016                           </p>
3017                         </td>
3018 <td>
3019                           <p>
3020                             no
3021                           </p>
3022                         </td>
3023 <td>
3024                           <p>
3025                             no
3026                           </p>
3027                         </td>
3028 </tr>
3029 <tr>
3030 <td>
3031                           <p><span><strong class="command">notify-passive</strong></span></p>
3032                         </td>
3033 <td>
3034                           <p>
3035                             no
3036                           </p>
3037                         </td>
3038 <td>
3039                           <p>
3040                             no
3041                           </p>
3042                         </td>
3043 <td>
3044                           <p>
3045                             yes
3046                           </p>
3047                         </td>
3048 </tr>
3049 </tbody>
3050 </table></div>
3051 <p>
3052                   Note that normal NOTIFY processing is not affected by
3053                   <span><strong class="command">dialup</strong></span>.
3054                 </p>
3055 </dd>
3056 <dt><span class="term"><span><strong class="command">fake-iquery</strong></span></span></dt>
3057 <dd><p>
3058                   In <acronym class="acronym">BIND</acronym> 8, this option
3059                   enabled simulating the obsolete DNS query type
3060                   IQUERY. <acronym class="acronym">BIND</acronym> 9 never does
3061                   IQUERY simulation.
3062                 </p></dd>
3063 <dt><span class="term"><span><strong class="command">fetch-glue</strong></span></span></dt>
3064 <dd><p>
3065                   This option is obsolete.
3066                   In BIND 8, <strong class="userinput"><code>fetch-glue yes</code></strong>
3067                   caused the server to attempt to fetch glue resource records
3068                   it
3069                   didn't have when constructing the additional
3070                   data section of a response.  This is now considered a bad
3071                   idea
3072                   and BIND 9 never does it.
3073                 </p></dd>
3074 <dt><span class="term"><span><strong class="command">flush-zones-on-shutdown</strong></span></span></dt>
3075 <dd><p>
3076                   When the nameserver exits due receiving SIGTERM,
3077                   flush or do not flush any pending zone writes.  The default
3078                   is
3079                   <span><strong class="command">flush-zones-on-shutdown</strong></span> <strong class="userinput"><code>no</code></strong>.
3080                 </p></dd>
3081 <dt><span class="term"><span><strong class="command">has-old-clients</strong></span></span></dt>
3082 <dd><p>
3083                   This option was incorrectly implemented
3084                   in <acronym class="acronym">BIND</acronym> 8, and is ignored by <acronym class="acronym">BIND</acronym> 9.
3085                   To achieve the intended effect
3086                   of
3087                   <span><strong class="command">has-old-clients</strong></span> <strong class="userinput"><code>yes</code></strong>, specify
3088                   the two separate options <span><strong class="command">auth-nxdomain</strong></span> <strong class="userinput"><code>yes</code></strong>
3089                   and <span><strong class="command">rfc2308-type1</strong></span> <strong class="userinput"><code>no</code></strong> instead.
3090                 </p></dd>
3091 <dt><span class="term"><span><strong class="command">host-statistics</strong></span></span></dt>
3092 <dd><p>
3093                   In BIND 8, this enables keeping of
3094                   statistics for every host that the name server interacts
3095                   with.
3096                   Not implemented in BIND 9.
3097                 </p></dd>
3098 <dt><span class="term"><span><strong class="command">maintain-ixfr-base</strong></span></span></dt>
3099 <dd><p>
3100                   <span class="emphasis"><em>This option is obsolete</em></span>.
3101                   It was used in <acronym class="acronym">BIND</acronym> 8 to
3102                   determine whether a transaction log was
3103                   kept for Incremental Zone Transfer. <acronym class="acronym">BIND</acronym> 9 maintains a transaction
3104                   log whenever possible.  If you need to disable outgoing
3105                   incremental zone
3106                   transfers, use <span><strong class="command">provide-ixfr</strong></span> <strong class="userinput"><code>no</code></strong>.
3107                 </p></dd>
3108 <dt><span class="term"><span><strong class="command">minimal-responses</strong></span></span></dt>
3109 <dd><p>
3110                   If <strong class="userinput"><code>yes</code></strong>, then when generating
3111                   responses the server will only add records to the authority
3112                   and additional data sections when they are required (e.g.
3113                   delegations, negative responses).  This may improve the
3114                   performance of the server.
3115                   The default is <strong class="userinput"><code>no</code></strong>.
3116                 </p></dd>
3117 <dt><span class="term"><span><strong class="command">multiple-cnames</strong></span></span></dt>
3118 <dd><p>
3119                   This option was used in <acronym class="acronym">BIND</acronym> 8 to allow
3120                   a domain name to have multiple CNAME records in violation of
3121                   the DNS standards.  <acronym class="acronym">BIND</acronym> 9.2 onwards
3122                   always strictly enforces the CNAME rules both in master
3123                   files and dynamic updates.
3124                 </p></dd>
3125 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
3126 <dd>
3127 <p>
3128                   If <strong class="userinput"><code>yes</code></strong> (the default),
3129                   DNS NOTIFY messages are sent when a zone the server is
3130                   authoritative for
3131                   changes, see <a href="Bv9ARM.ch04.html#notify" title="Notify">the section called &#8220;Notify&#8221;</a>.  The messages are
3132                   sent to the
3133                   servers listed in the zone's NS records (except the master
3134                   server identified
3135                   in the SOA MNAME field), and to any servers listed in the
3136                   <span><strong class="command">also-notify</strong></span> option.
3137                 </p>
3138 <p>
3139                   If <strong class="userinput"><code>master-only</code></strong>, notifies are only
3140                   sent
3141                   for master zones.
3142                   If <strong class="userinput"><code>explicit</code></strong>, notifies are sent only
3143                   to
3144                   servers explicitly listed using <span><strong class="command">also-notify</strong></span>.
3145                   If <strong class="userinput"><code>no</code></strong>, no notifies are sent.
3146                 </p>
3147 <p>
3148                   The <span><strong class="command">notify</strong></span> option may also be
3149                   specified in the <span><strong class="command">zone</strong></span>
3150                   statement,
3151                   in which case it overrides the <span><strong class="command">options notify</strong></span> statement.
3152                   It would only be necessary to turn off this option if it
3153                   caused slaves
3154                   to crash.
3155                 </p>
3156 </dd>
3157 <dt><span class="term"><span><strong class="command">notify-to-soa</strong></span></span></dt>
3158 <dd><p>
3159                   If <strong class="userinput"><code>yes</code></strong> do not check the nameservers
3160                   in the NS RRset against the SOA MNAME.  Normally a NOTIFY
3161                   message is not sent to the SOA MNAME (SOA ORIGIN) as it is
3162                   supposed to contain the name of the ultimate master.
3163                   Sometimes, however, a slave is listed as the SOA MNAME in
3164                   hidden master configurations and in that case you would
3165                   want the ultimate master to still send NOTIFY messages to
3166                   all the nameservers listed in the NS RRset.
3167                 </p></dd>
3168 <dt><span class="term"><span><strong class="command">recursion</strong></span></span></dt>
3169 <dd><p>
3170                   If <strong class="userinput"><code>yes</code></strong>, and a
3171                   DNS query requests recursion, then the server will attempt
3172                   to do
3173                   all the work required to answer the query. If recursion is
3174                   off
3175                   and the server does not already know the answer, it will
3176                   return a
3177                   referral response. The default is
3178                   <strong class="userinput"><code>yes</code></strong>.
3179                   Note that setting <span><strong class="command">recursion no</strong></span> does not prevent
3180                   clients from getting data from the server's cache; it only
3181                   prevents new data from being cached as an effect of client
3182                   queries.
3183                   Caching may still occur as an effect the server's internal
3184                   operation, such as NOTIFY address lookups.
3185                   See also <span><strong class="command">fetch-glue</strong></span> above.
3186                 </p></dd>
3187 <dt><span class="term"><span><strong class="command">rfc2308-type1</strong></span></span></dt>
3188 <dd>
3189 <p>
3190                   Setting this to <strong class="userinput"><code>yes</code></strong> will
3191                   cause the server to send NS records along with the SOA
3192                   record for negative
3193                   answers. The default is <strong class="userinput"><code>no</code></strong>.
3194                 </p>
3195 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3196 <h3 class="title">Note</h3>
3197 <p>
3198                     Not yet implemented in <acronym class="acronym">BIND</acronym>
3199                     9.
3200                   </p>
3201 </div>
3202 </dd>
3203 <dt><span class="term"><span><strong class="command">use-id-pool</strong></span></span></dt>
3204 <dd><p>
3205                   <span class="emphasis"><em>This option is obsolete</em></span>.
3206                   <acronym class="acronym">BIND</acronym> 9 always allocates query
3207                   IDs from a pool.
3208                 </p></dd>
3209 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
3210 <dd><p>
3211                   If <strong class="userinput"><code>yes</code></strong>, the server will collect
3212                   statistical data on all zones (unless specifically turned
3213                   off
3214                   on a per-zone basis by specifying <span><strong class="command">zone-statistics no</strong></span>
3215                   in the <span><strong class="command">zone</strong></span> statement).
3216                   The default is <strong class="userinput"><code>no</code></strong>.
3217                   These statistics may be accessed
3218                   using <span><strong class="command">rndc stats</strong></span>, which will
3219                   dump them to the file listed
3220                   in the <span><strong class="command">statistics-file</strong></span>.  See
3221                   also <a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
3222                 </p></dd>
3223 <dt><span class="term"><span><strong class="command">use-ixfr</strong></span></span></dt>
3224 <dd><p>
3225                   <span class="emphasis"><em>This option is obsolete</em></span>.
3226                   If you need to disable IXFR to a particular server or
3227                   servers, see
3228                   the information on the <span><strong class="command">provide-ixfr</strong></span> option
3229                   in <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3230             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3231             Usage&#8221;</a>.
3232                   See also
3233                   <a href="Bv9ARM.ch04.html#incremental_zone_transfers" title="Incremental Zone Transfers (IXFR)">the section called &#8220;Incremental Zone Transfers (IXFR)&#8221;</a>.
3234                 </p></dd>
3235 <dt><span class="term"><span><strong class="command">provide-ixfr</strong></span></span></dt>
3236 <dd><p>
3237                   See the description of
3238                   <span><strong class="command">provide-ixfr</strong></span> in
3239                   <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3240             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3241             Usage&#8221;</a>.
3242                 </p></dd>
3243 <dt><span class="term"><span><strong class="command">request-ixfr</strong></span></span></dt>
3244 <dd><p>
3245                   See the description of
3246                   <span><strong class="command">request-ixfr</strong></span> in
3247                   <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
3248             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
3249             Usage&#8221;</a>.
3250                 </p></dd>
3251 <dt><span class="term"><span><strong class="command">treat-cr-as-space</strong></span></span></dt>
3252 <dd><p>
3253                   This option was used in <acronym class="acronym">BIND</acronym>
3254                   8 to make
3255                   the server treat carriage return ("<span><strong class="command">\r</strong></span>") characters the same way
3256                   as a space or tab character,
3257                   to facilitate loading of zone files on a UNIX system that
3258                   were generated
3259                   on an NT or DOS machine. In <acronym class="acronym">BIND</acronym> 9, both UNIX "<span><strong class="command">\n</strong></span>"
3260                   and NT/DOS "<span><strong class="command">\r\n</strong></span>" newlines
3261                   are always accepted,
3262                   and the option is ignored.
3263                 </p></dd>
3264 <dt>
3265 <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>
3266 </dt>
3267 <dd>
3268 <p>
3269                   These options control the behavior of an authoritative
3270                   server when
3271                   answering queries which have additional data, or when
3272                   following CNAME
3273                   and DNAME chains.
3274                 </p>
3275 <p>
3276                   When both of these options are set to <strong class="userinput"><code>yes</code></strong>
3277                   (the default) and a
3278                   query is being answered from authoritative data (a zone
3279                   configured into the server), the additional data section of
3280                   the
3281                   reply will be filled in using data from other authoritative
3282                   zones
3283                   and from the cache.  In some situations this is undesirable,
3284                   such
3285                   as when there is concern over the correctness of the cache,
3286                   or
3287                   in servers where slave zones may be added and modified by
3288                   untrusted third parties.  Also, avoiding
3289                   the search for this additional data will speed up server
3290                   operations
3291                   at the possible expense of additional queries to resolve
3292                   what would
3293                   otherwise be provided in the additional section.
3294                 </p>
3295 <p>
3296                   For example, if a query asks for an MX record for host <code class="literal">foo.example.com</code>,
3297                   and the record found is "<code class="literal">MX 10 mail.example.net</code>", normally the address
3298                   records (A and AAAA) for <code class="literal">mail.example.net</code> will be provided as well,
3299                   if known, even though they are not in the example.com zone.
3300                   Setting these options to <span><strong class="command">no</strong></span>
3301                   disables this behavior and makes
3302                   the server only search for additional data in the zone it
3303                   answers from.
3304                 </p>
3305 <p>
3306                   These options are intended for use in authoritative-only
3307                   servers, or in authoritative-only views.  Attempts to set
3308                   them to <span><strong class="command">no</strong></span> without also
3309                   specifying
3310                   <span><strong class="command">recursion no</strong></span> will cause the
3311                   server to
3312                   ignore the options and log a warning message.
3313                 </p>
3314 <p>
3315                   Specifying <span><strong class="command">additional-from-cache no</strong></span> actually
3316                   disables the use of the cache not only for additional data
3317                   lookups
3318                   but also when looking up the answer.  This is usually the
3319                   desired
3320                   behavior in an authoritative-only server where the
3321                   correctness of
3322                   the cached data is an issue.
3323                 </p>
3324 <p>
3325                   When a name server is non-recursively queried for a name
3326                   that is not
3327                   below the apex of any served zone, it normally answers with
3328                   an
3329                   "upwards referral" to the root servers or the servers of
3330                   some other
3331                   known parent of the query name.  Since the data in an
3332                   upwards referral
3333                   comes from the cache, the server will not be able to provide
3334                   upwards
3335                   referrals when <span><strong class="command">additional-from-cache no</strong></span>
3336                   has been specified.  Instead, it will respond to such
3337                   queries
3338                   with REFUSED.  This should not cause any problems since
3339                   upwards referrals are not required for the resolution
3340                   process.
3341                 </p>
3342 </dd>
3343 <dt><span class="term"><span><strong class="command">match-mapped-addresses</strong></span></span></dt>
3344 <dd>
3345 <p>
3346                   If <strong class="userinput"><code>yes</code></strong>, then an
3347                   IPv4-mapped IPv6 address will match any address match
3348                   list entries that match the corresponding IPv4 address.
3349                 </p>
3350 <p>
3351                   This option was introduced to work around a kernel quirk
3352                   in some operating systems that causes IPv4 TCP
3353                   connections, such as zone transfers, to be accepted on an
3354                   IPv6 socket using mapped addresses.  This caused address
3355                   match lists designed for IPv4 to fail to match.  However,
3356                   <span><strong class="command">named</strong></span> now solves this problem
3357                   internally.  The use of this option is discouraged.
3358                 </p>
3359 </dd>
3360 <dt><span class="term"><span><strong class="command">filter-aaaa-on-v4</strong></span></span></dt>
3361 <dd>
3362 <p>
3363                   This option is only available when
3364                   <acronym class="acronym">BIND</acronym> 9 is compiled with the
3365                   <strong class="userinput"><code>--enable-filter-aaaa</code></strong> option on the
3366                   "configure" command line.  It is intended to help the
3367                   transition from IPv4 to IPv6 by not giving IPv6 addresses
3368                   to DNS clients unless they have connections to the IPv6
3369                   Internet.  This is not recommended unless absolutely
3370                   necessary.  The default is <strong class="userinput"><code>no</code></strong>.
3371                   The <span><strong class="command">filter-aaaa-on-v4</strong></span> option
3372                   may also be specified in <span><strong class="command">view</strong></span> statements
3373                   to override the global <span><strong class="command">filter-aaaa-on-v4</strong></span>
3374                   option.
3375                 </p>
3376 <p>
3377                   If <strong class="userinput"><code>yes</code></strong>,
3378                   the DNS client is at an IPv4 address, in <span><strong class="command">filter-aaaa</strong></span>,
3379                   and if the response does not include DNSSEC signatures,
3380                   then all AAAA records are deleted from the response.
3381                   This filtering applies to all responses and not only
3382                   authoritative responses.
3383                 </p>
3384 <p>
3385                   If <strong class="userinput"><code>break-dnssec</code></strong>,
3386                   then AAAA records are deleted even when dnssec is enabled.
3387                   As suggested by the name, this makes the response not verify,
3388                   because the DNSSEC protocol is designed detect deletions.
3389                 </p>
3390 <p>
3391                   This mechanism can erroneously cause other servers to
3392                   not give AAAA records to their clients.
3393                   A recursing server with both IPv6 and IPv4 network connections
3394                   that queries an authoritative server using this mechanism
3395                   via IPv4 will be denied AAAA records even if its client is
3396                   using IPv6.
3397                 </p>
3398 <p>
3399                   This mechanism is applied to authoritative as well as
3400                   non-authoritative records.
3401                   A client using IPv4 that is not allowed recursion can
3402                   erroneously be given AAAA records because the server is not
3403                   allowed to check for A records.
3404                 </p>
3405 <p>
3406                   Some AAAA records are given to IPv4 clients in glue records.
3407                   IPv4 clients that are servers can then erroneously
3408                   answer requests for AAAA records received via IPv4.
3409                 </p>
3410 </dd>
3411 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
3412 <dd>
3413 <p>
3414                   When <strong class="userinput"><code>yes</code></strong> and the server loads a new version of a master
3415                   zone from its zone file or receives a new version of a slave
3416                   file by a non-incremental zone transfer, it will compare
3417                   the new version to the previous one and calculate a set
3418                   of differences.  The differences are then logged in the
3419                   zone's journal file such that the changes can be transmitted
3420                   to downstream slaves as an incremental zone transfer.
3421                 </p>
3422 <p>
3423                   By allowing incremental zone transfers to be used for
3424                   non-dynamic zones, this option saves bandwidth at the
3425                   expense of increased CPU and memory consumption at the
3426                   master.
3427                   In particular, if the new version of a zone is completely
3428                   different from the previous one, the set of differences
3429                   will be of a size comparable to the combined size of the
3430                   old and new zone version, and the server will need to
3431                   temporarily allocate memory to hold this complete
3432                   difference set.
3433                 </p>
3434 <p><span><strong class="command">ixfr-from-differences</strong></span>
3435                   also accepts <span><strong class="command">master</strong></span> and
3436                   <span><strong class="command">slave</strong></span> at the view and options
3437                   levels which causes
3438                   <span><strong class="command">ixfr-from-differences</strong></span> to be enabled for
3439                   all <span><strong class="command">master</strong></span> or
3440                   <span><strong class="command">slave</strong></span> zones respectively.
3441                   It is off by default.
3442                 </p>
3443 </dd>
3444 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
3445 <dd><p>
3446                   This should be set when you have multiple masters for a zone
3447                   and the
3448                   addresses refer to different machines.  If <strong class="userinput"><code>yes</code></strong>, <span><strong class="command">named</strong></span> will
3449                   not log
3450                   when the serial number on the master is less than what <span><strong class="command">named</strong></span>
3451                   currently
3452                   has.  The default is <strong class="userinput"><code>no</code></strong>.
3453                 </p></dd>
3454 <dt><span class="term"><span><strong class="command">dnssec-enable</strong></span></span></dt>
3455 <dd><p>
3456                   Enable DNSSEC support in <span><strong class="command">named</strong></span>.  Unless set to <strong class="userinput"><code>yes</code></strong>,
3457                   <span><strong class="command">named</strong></span> behaves as if it does not support DNSSEC.
3458                   The default is <strong class="userinput"><code>yes</code></strong>.
3459                 </p></dd>
3460 <dt><span class="term"><span><strong class="command">dnssec-validation</strong></span></span></dt>
3461 <dd><p>
3462                   Enable DNSSEC validation in <span><strong class="command">named</strong></span>.
3463                   Note <span><strong class="command">dnssec-enable</strong></span> also needs to be
3464                   set to <strong class="userinput"><code>yes</code></strong> to be effective.
3465                   If set to <strong class="userinput"><code>no</code></strong>, DNSSEC validation
3466                   is disabled.  If set to <strong class="userinput"><code>auto</code></strong>,
3467                   DNSSEC validation is enabled, and a default
3468                   trust-anchor for the DNS root zone is used.  If set to
3469                   <strong class="userinput"><code>yes</code></strong>, DNSSEC validation is enabled,
3470                   but a trust anchor must be manually configured using
3471                   a <span><strong class="command">trusted-keys</strong></span> or
3472                   <span><strong class="command">managed-keys</strong></span> statement.  The default
3473                   is <strong class="userinput"><code>yes</code></strong>.
3474                 </p></dd>
3475 <dt><span class="term"><span><strong class="command">dnssec-accept-expired</strong></span></span></dt>
3476 <dd><p>
3477                   Accept expired signatures when verifying DNSSEC signatures.
3478                   The default is <strong class="userinput"><code>no</code></strong>.
3479                   Setting this option to <strong class="userinput"><code>yes</code></strong>
3480                   leaves <span><strong class="command">named</strong></span> vulnerable to
3481                   replay attacks.
3482                 </p></dd>
3483 <dt><span class="term"><span><strong class="command">querylog</strong></span></span></dt>
3484 <dd><p>
3485                   Specify whether query logging should be started when <span><strong class="command">named</strong></span>
3486                   starts.
3487                   If <span><strong class="command">querylog</strong></span> is not specified,
3488                   then the query logging
3489                   is determined by the presence of the logging category <span><strong class="command">queries</strong></span>.
3490                 </p></dd>
3491 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
3492 <dd>
3493 <p>
3494                   This option is used to restrict the character set and syntax
3495                   of
3496                   certain domain names in master files and/or DNS responses
3497                   received
3498                   from the network.  The default varies according to usage
3499                   area.  For
3500                   <span><strong class="command">master</strong></span> zones the default is <span><strong class="command">fail</strong></span>.
3501                   For <span><strong class="command">slave</strong></span> zones the default
3502                   is <span><strong class="command">warn</strong></span>.
3503                   For answers received from the network (<span><strong class="command">response</strong></span>)
3504                   the default is <span><strong class="command">ignore</strong></span>.
3505                 </p>
3506 <p>
3507                   The rules for legal hostnames and mail domains are derived
3508                   from RFC 952 and RFC 821 as modified by RFC 1123.
3509                 </p>
3510 <p><span><strong class="command">check-names</strong></span>
3511                   applies to the owner names of A, AAAA and MX records.
3512                   It also applies to the domain names in the RDATA of NS, SOA,
3513                   MX, and SRV records.
3514                   It also applies to the RDATA of PTR records where the owner
3515                   name indicated that it is a reverse lookup of a hostname
3516                   (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, or IP6.INT).
3517                 </p>
3518 </dd>
3519 <dt><span class="term"><span><strong class="command">check-dup-records</strong></span></span></dt>
3520 <dd><p>
3521                   Check master zones for records that are treated as different
3522                   by DNSSEC but are semantically equal in plain DNS.  The
3523                   default is to <span><strong class="command">warn</strong></span>.  Other possible
3524                   values are <span><strong class="command">fail</strong></span> and
3525                   <span><strong class="command">ignore</strong></span>.
3526                 </p></dd>
3527 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
3528 <dd><p>
3529                   Check whether the MX record appears to refer to a IP address.
3530                   The default is to <span><strong class="command">warn</strong></span>.  Other possible
3531                   values are <span><strong class="command">fail</strong></span> and
3532                   <span><strong class="command">ignore</strong></span>.
3533                 </p></dd>
3534 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
3535 <dd><p>
3536                   This option is used to check for non-terminal wildcards.
3537                   The use of non-terminal wildcards is almost always as a
3538                   result of a failure
3539                   to understand the wildcard matching algorithm (RFC 1034).
3540                   This option
3541                   affects master zones.  The default (<span><strong class="command">yes</strong></span>) is to check
3542                   for non-terminal wildcards and issue a warning.
3543                 </p></dd>
3544 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
3545 <dd><p>
3546                   Perform post load zone integrity checks on master
3547                   zones.  This checks that MX and SRV records refer
3548                   to address (A or AAAA) records and that glue
3549                   address records exist for delegated zones.  For
3550                   MX and SRV records only in-zone hostnames are
3551                   checked (for out-of-zone hostnames use
3552                   <span><strong class="command">named-checkzone</strong></span>).
3553                   For NS records only names below top of zone are
3554                   checked (for out-of-zone names and glue consistency
3555                   checks use <span><strong class="command">named-checkzone</strong></span>).
3556                   The default is <span><strong class="command">yes</strong></span>.
3557                 </p></dd>
3558 <dt><span class="term"><span><strong class="command">check-mx-cname</strong></span></span></dt>
3559 <dd><p>
3560                   If <span><strong class="command">check-integrity</strong></span> is set then
3561                   fail, warn or ignore MX records that refer
3562                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
3563                 </p></dd>
3564 <dt><span class="term"><span><strong class="command">check-srv-cname</strong></span></span></dt>
3565 <dd><p>
3566                   If <span><strong class="command">check-integrity</strong></span> is set then
3567                   fail, warn or ignore SRV records that refer
3568                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
3569                 </p></dd>
3570 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
3571 <dd><p>
3572                   When performing integrity checks, also check that
3573                   sibling glue exists.  The default is <span><strong class="command">yes</strong></span>.
3574                 </p></dd>
3575 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
3576 <dd><p>
3577                   When returning authoritative negative responses to
3578                   SOA queries set the TTL of the SOA record returned in
3579                   the authority section to zero.
3580                   The default is <span><strong class="command">yes</strong></span>.
3581                 </p></dd>
3582 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl-cache</strong></span></span></dt>
3583 <dd><p>
3584                   When caching a negative response to a SOA query
3585                   set the TTL to zero.
3586                   The default is <span><strong class="command">no</strong></span>.
3587                 </p></dd>
3588 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
3589 <dd>
3590 <p>
3591                   When set to the default value of <code class="literal">yes</code>,
3592                   check the KSK bit in each key to determine how the key
3593                   should be used when generating RRSIGs for a secure zone.
3594                 </p>
3595 <p>
3596                   Ordinarily, zone-signing keys (that is, keys without the
3597                   KSK bit set) are used to sign the entire zone, while
3598                   key-signing keys (keys with the KSK bit set) are only
3599                   used to sign the DNSKEY RRset at the zone apex.
3600                   However, if this option is set to <code class="literal">no</code>,
3601                   then the KSK bit is ignored; KSKs are treated as if they
3602                   were ZSKs and are used to sign the entire zone.  This is
3603                   similar to the <span><strong class="command">dnssec-signzone -z</strong></span>
3604                   command line option.
3605                 </p>
3606 <p>
3607                   When this option is set to <code class="literal">yes</code>, there
3608                   must be at least two active keys for every algorithm
3609                   represented in the DNSKEY RRset: at least one KSK and one
3610                   ZSK per algorithm.  If there is any algorithm for which
3611                   this requirement is not met, this option will be ignored
3612                   for that algorithm.
3613                 </p>
3614 </dd>
3615 <dt><span class="term"><span><strong class="command">dnssec-dnskey-kskonly</strong></span></span></dt>
3616 <dd>
3617 <p>
3618                   When this option and <span><strong class="command">update-check-ksk</strong></span>
3619                   are both set to <code class="literal">yes</code>, only key-signing
3620                   keys (that is, keys with the KSK bit set) will be used
3621                   to sign the DNSKEY RRset at the zone apex.  Zone-signing
3622                   keys (keys without the KSK bit set) will be used to sign
3623                   the remainder of the zone, but not the DNSKEY RRset.
3624                   This is similar to the
3625                   <span><strong class="command">dnssec-signzone -x</strong></span> command line option.
3626                 </p>
3627 <p>
3628                   The default is <span><strong class="command">no</strong></span>.  If
3629                   <span><strong class="command">update-check-ksk</strong></span> is set to
3630                   <code class="literal">no</code>, this option is ignored.
3631                 </p>
3632 </dd>
3633 <dt><span class="term"><span><strong class="command">try-tcp-refresh</strong></span></span></dt>
3634 <dd><p>
3635                   Try to refresh the zone using TCP if UDP queries fail.
3636                   For BIND 8 compatibility, the default is
3637                   <span><strong class="command">yes</strong></span>.
3638                 </p></dd>
3639 <dt><span class="term"><span><strong class="command">dnssec-secure-to-insecure</strong></span></span></dt>
3640 <dd>
3641 <p>
3642                   Allow a dynamic zone to transition from secure to
3643                   insecure (i.e., signed to unsigned) by deleting all
3644                   of the DNSKEY records.  The default is <span><strong class="command">no</strong></span>.
3645                   If set to <span><strong class="command">yes</strong></span>, and if the DNSKEY RRset
3646                   at the zone apex is deleted, all RRSIG and NSEC records
3647                   will be removed from the zone as well.
3648                 </p>
3649 <p>
3650                   If the zone uses NSEC3, then it is also necessary to
3651                   delete the NSEC3PARAM RRset from the zone apex; this will
3652                   cause the removal of all corresponding NSEC3 records.
3653                   (It is expected that this requirement will be eliminated
3654                   in a future release.)
3655                 </p>
3656 <p>
3657                   Note that if a zone has been configured with
3658                   <span><strong class="command">auto-dnssec maintain</strong></span> and the
3659                   private keys remain accessible in the key repository,
3660                   then the zone will be automatically signed again the
3661                   next time <span><strong class="command">named</strong></span> is started.
3662                 </p>
3663 </dd>
3664 </dl></div>
3665 </div>
3666 <div class="sect3" lang="en">
3667 <div class="titlepage"><div><div><h4 class="title">
3668 <a name="id2583643"></a>Forwarding</h4></div></div></div>
3669 <p>
3670             The forwarding facility can be used to create a large site-wide
3671             cache on a few servers, reducing traffic over links to external
3672             name servers. It can also be used to allow queries by servers that
3673             do not have direct access to the Internet, but wish to look up
3674             exterior
3675             names anyway. Forwarding occurs only on those queries for which
3676             the server is not authoritative and does not have the answer in
3677             its cache.
3678           </p>
3679 <div class="variablelist"><dl>
3680 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
3681 <dd><p>
3682                   This option is only meaningful if the
3683                   forwarders list is not empty. A value of <code class="varname">first</code>,
3684                   the default, causes the server to query the forwarders
3685                   first &#8212; and
3686                   if that doesn't answer the question, the server will then
3687                   look for
3688                   the answer itself. If <code class="varname">only</code> is
3689                   specified, the
3690                   server will only query the forwarders.
3691                 </p></dd>
3692 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
3693 <dd><p>
3694                   Specifies the IP addresses to be used
3695                   for forwarding. The default is the empty list (no
3696                   forwarding).
3697                 </p></dd>
3698 </dl></div>
3699 <p>
3700             Forwarding can also be configured on a per-domain basis, allowing
3701             for the global forwarding options to be overridden in a variety
3702             of ways. You can set particular domains to use different
3703             forwarders,
3704             or have a different <span><strong class="command">forward only/first</strong></span> behavior,
3705             or not forward at all, see <a href="Bv9ARM.ch06.html#zone_statement_grammar" title="zone
3706             Statement Grammar">the section called &#8220;<span><strong class="command">zone</strong></span>
3707             Statement Grammar&#8221;</a>.
3708           </p>
3709 </div>
3710 <div class="sect3" lang="en">
3711 <div class="titlepage"><div><div><h4 class="title">
3712 <a name="id2583702"></a>Dual-stack Servers</h4></div></div></div>
3713 <p>
3714             Dual-stack servers are used as servers of last resort to work
3715             around
3716             problems in reachability due the lack of support for either IPv4
3717             or IPv6
3718             on the host machine.
3719           </p>
3720 <div class="variablelist"><dl>
3721 <dt><span class="term"><span><strong class="command">dual-stack-servers</strong></span></span></dt>
3722 <dd><p>
3723                   Specifies host names or addresses of machines with access to
3724                   both IPv4 and IPv6 transports. If a hostname is used, the
3725                   server must be able
3726                   to resolve the name using only the transport it has.  If the
3727                   machine is dual
3728                   stacked, then the <span><strong class="command">dual-stack-servers</strong></span> have no effect unless
3729                   access to a transport has been disabled on the command line
3730                   (e.g. <span><strong class="command">named -4</strong></span>).
3731                 </p></dd>
3732 </dl></div>
3733 </div>
3734 <div class="sect3" lang="en">
3735 <div class="titlepage"><div><div><h4 class="title">
3736 <a name="access_control"></a>Access Control</h4></div></div></div>
3737 <p>
3738             Access to the server can be restricted based on the IP address
3739             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
3740             details on how to specify IP address lists.
3741           </p>
3742 <div class="variablelist"><dl>
3743 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
3744 <dd><p>
3745                   Specifies which hosts are allowed to
3746                   notify this server, a slave, of zone changes in addition
3747                   to the zone masters.
3748                   <span><strong class="command">allow-notify</strong></span> may also be
3749                   specified in the
3750                   <span><strong class="command">zone</strong></span> statement, in which case
3751                   it overrides the
3752                   <span><strong class="command">options allow-notify</strong></span>
3753                   statement.  It is only meaningful
3754                   for a slave zone.  If not specified, the default is to
3755                   process notify messages
3756                   only from a zone's master.
3757                 </p></dd>
3758 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
3759 <dd>
3760 <p>
3761                   Specifies which hosts are allowed to ask ordinary
3762                   DNS questions. <span><strong class="command">allow-query</strong></span> may
3763                   also be specified in the <span><strong class="command">zone</strong></span>
3764                   statement, in which case it overrides the
3765                   <span><strong class="command">options allow-query</strong></span> statement.
3766                   If not specified, the default is to allow queries
3767                   from all hosts.
3768                 </p>
3769 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3770 <h3 class="title">Note</h3>
3771 <p>
3772                     <span><strong class="command">allow-query-cache</strong></span> is now
3773                     used to specify access to the cache.
3774                   </p>
3775 </div>
3776 </dd>
3777 <dt><span class="term"><span><strong class="command">allow-query-on</strong></span></span></dt>
3778 <dd>
3779 <p>
3780                   Specifies which local addresses can accept ordinary
3781                   DNS questions. This makes it possible, for instance,
3782                   to allow queries on internal-facing interfaces but
3783                   disallow them on external-facing ones, without
3784                   necessarily knowing the internal network's addresses.
3785                 </p>
3786 <p>
3787                   <span><strong class="command">allow-query-on</strong></span> may
3788                   also be specified in the <span><strong class="command">zone</strong></span>
3789                   statement, in which case it overrides the
3790                   <span><strong class="command">options allow-query-on</strong></span> statement.
3791                 </p>
3792 <p>
3793                   If not specified, the default is to allow queries
3794                   on all addresses.
3795                 </p>
3796 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3797 <h3 class="title">Note</h3>
3798 <p>
3799                     <span><strong class="command">allow-query-cache</strong></span> is
3800                     used to specify access to the cache.
3801                   </p>
3802 </div>
3803 </dd>
3804 <dt><span class="term"><span><strong class="command">allow-query-cache</strong></span></span></dt>
3805 <dd><p>
3806                   Specifies which hosts are allowed to get answers
3807                   from the cache.  If <span><strong class="command">allow-query-cache</strong></span>
3808                   is not set then <span><strong class="command">allow-recursion</strong></span>
3809                   is used if set, otherwise <span><strong class="command">allow-query</strong></span>
3810                   is used if set unless <span><strong class="command">recursion no;</strong></span> is
3811                   set in which case <span><strong class="command">none;</strong></span> is used,
3812                   otherwise the default (<span><strong class="command">localnets;</strong></span>
3813                   <span><strong class="command">localhost;</strong></span>) is used.
3814                 </p></dd>
3815 <dt><span class="term"><span><strong class="command">allow-query-cache-on</strong></span></span></dt>
3816 <dd><p>
3817                   Specifies which local addresses can give answers
3818                   from the cache.  If not specified, the default is
3819                   to allow cache queries on any address,
3820                   <span><strong class="command">localnets</strong></span> and
3821                   <span><strong class="command">localhost</strong></span>.
3822                 </p></dd>
3823 <dt><span class="term"><span><strong class="command">allow-recursion</strong></span></span></dt>
3824 <dd><p>
3825                   Specifies which hosts are allowed to make recursive
3826                   queries through this server. If
3827                   <span><strong class="command">allow-recursion</strong></span> is not set
3828                   then <span><strong class="command">allow-query-cache</strong></span> is
3829                   used if set, otherwise <span><strong class="command">allow-query</strong></span>
3830                   is used if set, otherwise the default
3831                   (<span><strong class="command">localnets;</strong></span>
3832                   <span><strong class="command">localhost;</strong></span>) is used.
3833                 </p></dd>
3834 <dt><span class="term"><span><strong class="command">allow-recursion-on</strong></span></span></dt>
3835 <dd><p>
3836                   Specifies which local addresses can accept recursive
3837                   queries.  If not specified, the default is to allow
3838                   recursive queries on all addresses.
3839                 </p></dd>
3840 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
3841 <dd><p>
3842                   Specifies which hosts are allowed to
3843                   submit Dynamic DNS updates for master zones. The default is
3844                   to deny
3845                   updates from all hosts.  Note that allowing updates based
3846                   on the requestor's IP address is insecure; see
3847                   <a href="Bv9ARM.ch07.html#dynamic_update_security" title="Dynamic Update Security">the section called &#8220;Dynamic Update Security&#8221;</a> for details.
3848                 </p></dd>
3849 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
3850 <dd>
3851 <p>
3852                   Specifies which hosts are allowed to
3853                   submit Dynamic DNS updates to slave zones to be forwarded to
3854                   the
3855                   master.  The default is <strong class="userinput"><code>{ none; }</code></strong>,
3856                   which
3857                   means that no update forwarding will be performed.  To
3858                   enable
3859                   update forwarding, specify
3860                   <strong class="userinput"><code>allow-update-forwarding { any; };</code></strong>.
3861                   Specifying values other than <strong class="userinput"><code>{ none; }</code></strong> or
3862                   <strong class="userinput"><code>{ any; }</code></strong> is usually
3863                   counterproductive, since
3864                   the responsibility for update access control should rest
3865                   with the
3866                   master server, not the slaves.
3867                 </p>
3868 <p>
3869                   Note that enabling the update forwarding feature on a slave
3870                   server
3871                   may expose master servers relying on insecure IP address
3872                   based
3873                   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>
3874                   for more details.
3875                 </p>
3876 </dd>
3877 <dt><span class="term"><span><strong class="command">allow-v6-synthesis</strong></span></span></dt>
3878 <dd><p>
3879                   This option was introduced for the smooth transition from
3880                   AAAA
3881                   to A6 and from "nibble labels" to binary labels.
3882                   However, since both A6 and binary labels were then
3883                   deprecated,
3884                   this option was also deprecated.
3885                   It is now ignored with some warning messages.
3886                 </p></dd>
3887 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
3888 <dd><p>
3889                   Specifies which hosts are allowed to
3890                   receive zone transfers from the server. <span><strong class="command">allow-transfer</strong></span> may
3891                   also be specified in the <span><strong class="command">zone</strong></span>
3892                   statement, in which
3893                   case it overrides the <span><strong class="command">options allow-transfer</strong></span> statement.
3894                   If not specified, the default is to allow transfers to all
3895                   hosts.
3896                 </p></dd>
3897 <dt><span class="term"><span><strong class="command">blackhole</strong></span></span></dt>
3898 <dd><p>
3899                   Specifies a list of addresses that the
3900                   server will not accept queries from or use to resolve a
3901                   query. Queries
3902                   from these addresses will not be responded to. The default
3903                   is <strong class="userinput"><code>none</code></strong>.
3904                 </p></dd>
3905 <dt><span class="term"><span><strong class="command">filter-aaaa</strong></span></span></dt>
3906 <dd><p>
3907                   Specifies a list of addresses to which
3908                   <span><strong class="command">filter-aaaa-on-v4</strong></span>
3909                   is applies.  The default is <strong class="userinput"><code>any</code></strong>.
3910                 </p></dd>
3911 <dt><span class="term"><span><strong class="command">resolver-query-timeout</strong></span></span></dt>
3912 <dd><p>
3913                   The amount of time the resolver will spend attempting
3914                   to resolve a recursive query before failing.  The
3915                   default is <code class="literal">10</code> and the maximum is
3916                   <code class="literal">30</code>.  Setting it to <code class="literal">0</code>
3917                   will result in the default being used.
3918                 </p></dd>
3919 </dl></div>
3920 </div>
3921 <div class="sect3" lang="en">
3922 <div class="titlepage"><div><div><h4 class="title">
3923 <a name="id2584322"></a>Interfaces</h4></div></div></div>
3924 <p>
3925             The interfaces and ports that the server will answer queries
3926             from may be specified using the <span><strong class="command">listen-on</strong></span> option. <span><strong class="command">listen-on</strong></span> takes
3927             an optional port and an <code class="varname">address_match_list</code>.
3928             The server will listen on all interfaces allowed by the address
3929             match list. If a port is not specified, port 53 will be used.
3930           </p>
3931 <p>
3932             Multiple <span><strong class="command">listen-on</strong></span> statements are
3933             allowed.
3934             For example,
3935           </p>
3936 <pre class="programlisting">listen-on { 5.6.7.8; };
3937 listen-on port 1234 { !1.2.3.4; 1.2/16; };
3938 </pre>
3939 <p>
3940             will enable the name server on port 53 for the IP address
3941             5.6.7.8, and on port 1234 of an address on the machine in net
3942             1.2 that is not 1.2.3.4.
3943           </p>
3944 <p>
3945             If no <span><strong class="command">listen-on</strong></span> is specified, the
3946             server will listen on port 53 on all IPv4 interfaces.
3947           </p>
3948 <p>
3949             The <span><strong class="command">listen-on-v6</strong></span> option is used to
3950             specify the interfaces and the ports on which the server will
3951             listen
3952             for incoming queries sent using IPv6.
3953           </p>
3954 <p>
3955             When </p>
3956 <pre class="programlisting">{ any; }</pre>
3957 <p> is
3958             specified
3959             as the <code class="varname">address_match_list</code> for the
3960             <span><strong class="command">listen-on-v6</strong></span> option,
3961             the server does not bind a separate socket to each IPv6 interface
3962             address as it does for IPv4 if the operating system has enough API
3963             support for IPv6 (specifically if it conforms to RFC 3493 and RFC
3964             3542).
3965             Instead, it listens on the IPv6 wildcard address.
3966             If the system only has incomplete API support for IPv6, however,
3967             the behavior is the same as that for IPv4.
3968           </p>
3969 <p>
3970             A list of particular IPv6 addresses can also be specified, in
3971             which case
3972             the server listens on a separate socket for each specified
3973             address,
3974             regardless of whether the desired API is supported by the system.
3975           </p>
3976 <p>
3977             Multiple <span><strong class="command">listen-on-v6</strong></span> options can
3978             be used.
3979             For example,
3980           </p>
3981 <pre class="programlisting">listen-on-v6 { any; };
3982 listen-on-v6 port 1234 { !2001:db8::/32; any; };
3983 </pre>
3984 <p>
3985             will enable the name server on port 53 for any IPv6 addresses
3986             (with a single wildcard socket),
3987             and on port 1234 of IPv6 addresses that is not in the prefix
3988             2001:db8::/32 (with separate sockets for each matched address.)
3989           </p>
3990 <p>
3991             To make the server not listen on any IPv6 address, use
3992           </p>
3993 <pre class="programlisting">listen-on-v6 { none; };
3994 </pre>
3995 <p>
3996             If no <span><strong class="command">listen-on-v6</strong></span> option is
3997             specified, the server will not listen on any IPv6 address
3998             unless <span><strong class="command">-6</strong></span> is specified when <span><strong class="command">named</strong></span> is
3999             invoked.  If <span><strong class="command">-6</strong></span> is specified then
4000             <span><strong class="command">named</strong></span> will listen on port 53 on all IPv6 interfaces by default.
4001           </p>
4002 </div>
4003 <div class="sect3" lang="en">
4004 <div class="titlepage"><div><div><h4 class="title">
4005 <a name="query_address"></a>Query Address</h4></div></div></div>
4006 <p>
4007             If the server doesn't know the answer to a question, it will
4008             query other name servers. <span><strong class="command">query-source</strong></span> specifies
4009             the address and port used for such queries. For queries sent over
4010             IPv6, there is a separate <span><strong class="command">query-source-v6</strong></span> option.
4011             If <span><strong class="command">address</strong></span> is <span><strong class="command">*</strong></span> (asterisk) or is omitted,
4012             a wildcard IP address (<span><strong class="command">INADDR_ANY</strong></span>)
4013             will be used.
4014           </p>
4015 <p>
4016             If <span><strong class="command">port</strong></span> is <span><strong class="command">*</strong></span> or is omitted,
4017             a random port number from a pre-configured
4018             range is picked up and will be used for each query.
4019             The port range(s) is that specified in
4020             the <span><strong class="command">use-v4-udp-ports</strong></span> (for IPv4)
4021             and <span><strong class="command">use-v6-udp-ports</strong></span> (for IPv6)
4022             options, excluding the ranges specified in
4023             the <span><strong class="command">avoid-v4-udp-ports</strong></span>
4024             and <span><strong class="command">avoid-v6-udp-ports</strong></span> options, respectively.
4025           </p>
4026 <p>
4027             The defaults of the <span><strong class="command">query-source</strong></span> and
4028             <span><strong class="command">query-source-v6</strong></span> options
4029             are:
4030           </p>
4031 <pre class="programlisting">query-source address * port *;
4032 query-source-v6 address * port *;
4033 </pre>
4034 <p>
4035             If <span><strong class="command">use-v4-udp-ports</strong></span> or
4036             <span><strong class="command">use-v6-udp-ports</strong></span> is unspecified,
4037             <span><strong class="command">named</strong></span> will check if the operating
4038             system provides a programming interface to retrieve the
4039             system's default range for ephemeral ports.
4040             If such an interface is available,
4041             <span><strong class="command">named</strong></span> will use the corresponding system
4042             default range; otherwise, it will use its own defaults:
4043          </p>
4044 <pre class="programlisting">use-v4-udp-ports { range 1024 65535; };
4045 use-v6-udp-ports { range 1024 65535; };
4046 </pre>
4047 <p>
4048             Note: make sure the ranges be sufficiently large for
4049             security.  A desirable size depends on various parameters,
4050             but we generally recommend it contain at least 16384 ports
4051             (14 bits of entropy).
4052             Note also that the system's default range when used may be
4053             too small for this purpose, and that the range may even be
4054             changed while <span><strong class="command">named</strong></span> is running; the new
4055             range will automatically be applied when <span><strong class="command">named</strong></span>
4056             is reloaded.
4057             It is encouraged to
4058             configure <span><strong class="command">use-v4-udp-ports</strong></span> and
4059             <span><strong class="command">use-v6-udp-ports</strong></span> explicitly so that the
4060             ranges are sufficiently large and are reasonably
4061             independent from the ranges used by other applications.
4062           </p>
4063 <p>
4064             Note: the operational configuration
4065             where <span><strong class="command">named</strong></span> runs may prohibit the use
4066             of some ports.  For example, UNIX systems will not allow
4067             <span><strong class="command">named</strong></span> running without a root privilege
4068             to use ports less than 1024.
4069             If such ports are included in the specified (or detected)
4070             set of query ports, the corresponding query attempts will
4071             fail, resulting in resolution failures or delay.
4072             It is therefore important to configure the set of ports
4073             that can be safely used in the expected operational environment.
4074           </p>
4075 <p>
4076             The defaults of the <span><strong class="command">avoid-v4-udp-ports</strong></span> and
4077             <span><strong class="command">avoid-v6-udp-ports</strong></span> options
4078             are:
4079           </p>
4080 <pre class="programlisting">avoid-v4-udp-ports {};
4081 avoid-v6-udp-ports {};
4082 </pre>
4083 <p>
4084             Note: BIND 9.5.0 introduced
4085             the <span><strong class="command">use-queryport-pool</strong></span>
4086             option to support a pool of such random ports, but this
4087             option is now obsolete because reusing the same ports in
4088             the pool may not be sufficiently secure.
4089             For the same reason, it is generally strongly discouraged to
4090             specify a particular port for the
4091             <span><strong class="command">query-source</strong></span> or
4092             <span><strong class="command">query-source-v6</strong></span> options;
4093             it implicitly disables the use of randomized port numbers.
4094           </p>
4095 <div class="variablelist"><dl>
4096 <dt><span class="term"><span><strong class="command">use-queryport-pool</strong></span></span></dt>
4097 <dd><p>
4098                   This option is obsolete.
4099                 </p></dd>
4100 <dt><span class="term"><span><strong class="command">queryport-pool-ports</strong></span></span></dt>
4101 <dd><p>
4102                   This option is obsolete.
4103                 </p></dd>
4104 <dt><span class="term"><span><strong class="command">queryport-pool-updateinterval</strong></span></span></dt>
4105 <dd><p>
4106                   This option is obsolete.
4107                 </p></dd>
4108 </dl></div>
4109 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4110 <h3 class="title">Note</h3>
4111 <p>
4112               The address specified in the <span><strong class="command">query-source</strong></span> option
4113               is used for both UDP and TCP queries, but the port applies only
4114               to UDP queries.  TCP queries always use a random
4115               unprivileged port.
4116             </p>
4117 </div>
4118 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4119 <h3 class="title">Note</h3>
4120 <p>
4121               Solaris 2.5.1 and earlier does not support setting the source
4122               address for TCP sockets.
4123             </p>
4124 </div>
4125 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4126 <h3 class="title">Note</h3>
4127 <p>
4128               See also <span><strong class="command">transfer-source</strong></span> and
4129               <span><strong class="command">notify-source</strong></span>.
4130             </p>
4131 </div>
4132 </div>
4133 <div class="sect3" lang="en">
4134 <div class="titlepage"><div><div><h4 class="title">
4135 <a name="zone_transfers"></a>Zone Transfers</h4></div></div></div>
4136 <p>
4137             <acronym class="acronym">BIND</acronym> has mechanisms in place to
4138             facilitate zone transfers
4139             and set limits on the amount of load that transfers place on the
4140             system. The following options apply to zone transfers.
4141           </p>
4142 <div class="variablelist"><dl>
4143 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
4144 <dd><p>
4145                   Defines a global list of IP addresses of name servers
4146                   that are also sent NOTIFY messages whenever a fresh copy of
4147                   the
4148                   zone is loaded, in addition to the servers listed in the
4149                   zone's NS records.
4150                   This helps to ensure that copies of the zones will
4151                   quickly converge on stealth servers.
4152                   Optionally, a port may be specified with each
4153                   <span><strong class="command">also-notify</strong></span> address to send
4154                   the notify messages to a port other than the
4155                   default of 53.
4156                   If an <span><strong class="command">also-notify</strong></span> list
4157                   is given in a <span><strong class="command">zone</strong></span> statement,
4158                   it will override
4159                   the <span><strong class="command">options also-notify</strong></span>
4160                   statement. When a <span><strong class="command">zone notify</strong></span>
4161                   statement
4162                   is set to <span><strong class="command">no</strong></span>, the IP
4163                   addresses in the global <span><strong class="command">also-notify</strong></span> list will
4164                   not be sent NOTIFY messages for that zone. The default is
4165                   the empty
4166                   list (no global notification list).
4167                 </p></dd>
4168 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
4169 <dd><p>
4170                   Inbound zone transfers running longer than
4171                   this many minutes will be terminated. The default is 120
4172                   minutes
4173                   (2 hours).  The maximum value is 28 days (40320 minutes).
4174                 </p></dd>
4175 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
4176 <dd><p>
4177                   Inbound zone transfers making no progress
4178                   in this many minutes will be terminated. The default is 60
4179                   minutes
4180                   (1 hour).  The maximum value is 28 days (40320 minutes).
4181                 </p></dd>
4182 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
4183 <dd><p>
4184                   Outbound zone transfers running longer than
4185                   this many minutes will be terminated. The default is 120
4186                   minutes
4187                   (2 hours).  The maximum value is 28 days (40320 minutes).
4188                 </p></dd>
4189 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
4190 <dd><p>
4191                   Outbound zone transfers making no progress
4192                   in this many minutes will be terminated.  The default is 60
4193                   minutes (1
4194                   hour).  The maximum value is 28 days (40320 minutes).
4195                 </p></dd>
4196 <dt><span class="term"><span><strong class="command">serial-query-rate</strong></span></span></dt>
4197 <dd>
4198 <p>
4199                   Slave servers will periodically query master
4200                   servers to find out if zone serial numbers have
4201                   changed. Each such query uses a minute amount of
4202                   the slave server's network bandwidth.  To limit
4203                   the amount of bandwidth used, BIND 9 limits the
4204                   rate at which queries are sent.  The value of the
4205                   <span><strong class="command">serial-query-rate</strong></span> option, an
4206                   integer, is the maximum number of queries sent
4207                   per second.  The default is 20.
4208                 </p>
4209 <p>
4210                   In addition to controlling the rate SOA refresh
4211                   queries are issued at
4212                   <span><strong class="command">serial-query-rate</strong></span> also controls
4213                   the rate at which NOTIFY messages are sent from
4214                   both master and slave zones.
4215                 </p>
4216 </dd>
4217 <dt><span class="term"><span><strong class="command">serial-queries</strong></span></span></dt>
4218 <dd><p>
4219                   In BIND 8, the <span><strong class="command">serial-queries</strong></span>
4220                   option
4221                   set the maximum number of concurrent serial number queries
4222                   allowed to be outstanding at any given time.
4223                   BIND 9 does not limit the number of outstanding
4224                   serial queries and ignores the <span><strong class="command">serial-queries</strong></span> option.
4225                   Instead, it limits the rate at which the queries are sent
4226                   as defined using the <span><strong class="command">serial-query-rate</strong></span> option.
4227                 </p></dd>
4228 <dt><span class="term"><span><strong class="command">transfer-format</strong></span></span></dt>
4229 <dd><p>
4230                   Zone transfers can be sent using two different formats,
4231                   <span><strong class="command">one-answer</strong></span> and
4232                   <span><strong class="command">many-answers</strong></span>.
4233                   The <span><strong class="command">transfer-format</strong></span> option is used
4234                   on the master server to determine which format it sends.
4235                   <span><strong class="command">one-answer</strong></span> uses one DNS message per
4236                   resource record transferred.
4237                   <span><strong class="command">many-answers</strong></span> packs as many resource
4238                   records as possible into a message.
4239                   <span><strong class="command">many-answers</strong></span> is more efficient, but is
4240                   only supported by relatively new slave servers,
4241                   such as <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
4242                   8.x and <acronym class="acronym">BIND</acronym> 4.9.5 onwards.
4243                   The <span><strong class="command">many-answers</strong></span> format is also supported by
4244                   recent Microsoft Windows nameservers.
4245                   The default is <span><strong class="command">many-answers</strong></span>.
4246                   <span><strong class="command">transfer-format</strong></span> may be overridden on a
4247                   per-server basis by using the <span><strong class="command">server</strong></span>
4248                   statement.
4249                 </p></dd>
4250 <dt><span class="term"><span><strong class="command">transfers-in</strong></span></span></dt>
4251 <dd><p>
4252                   The maximum number of inbound zone transfers
4253                   that can be running concurrently. The default value is <code class="literal">10</code>.
4254                   Increasing <span><strong class="command">transfers-in</strong></span> may
4255                   speed up the convergence
4256                   of slave zones, but it also may increase the load on the
4257                   local system.
4258                 </p></dd>
4259 <dt><span class="term"><span><strong class="command">transfers-out</strong></span></span></dt>
4260 <dd><p>
4261                   The maximum number of outbound zone transfers
4262                   that can be running concurrently. Zone transfer requests in
4263                   excess
4264                   of the limit will be refused. The default value is <code class="literal">10</code>.
4265                 </p></dd>
4266 <dt><span class="term"><span><strong class="command">transfers-per-ns</strong></span></span></dt>
4267 <dd><p>
4268                   The maximum number of inbound zone transfers
4269                   that can be concurrently transferring from a given remote
4270                   name server.
4271                   The default value is <code class="literal">2</code>.
4272                   Increasing <span><strong class="command">transfers-per-ns</strong></span>
4273                   may
4274                   speed up the convergence of slave zones, but it also may
4275                   increase
4276                   the load on the remote name server. <span><strong class="command">transfers-per-ns</strong></span> may
4277                   be overridden on a per-server basis by using the <span><strong class="command">transfers</strong></span> phrase
4278                   of the <span><strong class="command">server</strong></span> statement.
4279                 </p></dd>
4280 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
4281 <dd>
4282 <p><span><strong class="command">transfer-source</strong></span>
4283                   determines which local address will be bound to IPv4
4284                   TCP connections used to fetch zones transferred
4285                   inbound by the server.  It also determines the
4286                   source IPv4 address, and optionally the UDP port,
4287                   used for the refresh queries and forwarded dynamic
4288                   updates.  If not set, it defaults to a system
4289                   controlled value which will usually be the address
4290                   of the interface "closest to" the remote end. This
4291                   address must appear in the remote end's
4292                   <span><strong class="command">allow-transfer</strong></span> option for the
4293                   zone being transferred, if one is specified. This
4294                   statement sets the
4295                   <span><strong class="command">transfer-source</strong></span> for all zones,
4296                   but can be overridden on a per-view or per-zone
4297                   basis by including a
4298                   <span><strong class="command">transfer-source</strong></span> statement within
4299                   the <span><strong class="command">view</strong></span> or
4300                   <span><strong class="command">zone</strong></span> block in the configuration
4301                   file.
4302                 </p>
4303 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4304 <h3 class="title">Note</h3>
4305 <p>
4306                     Solaris 2.5.1 and earlier does not support setting the
4307                     source address for TCP sockets.
4308                   </p>
4309 </div>
4310 </dd>
4311 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
4312 <dd><p>
4313                   The same as <span><strong class="command">transfer-source</strong></span>,
4314                   except zone transfers are performed using IPv6.
4315                 </p></dd>
4316 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
4317 <dd>
4318 <p>
4319                   An alternate transfer source if the one listed in
4320                   <span><strong class="command">transfer-source</strong></span> fails and
4321                   <span><strong class="command">use-alt-transfer-source</strong></span> is
4322                   set.
4323                 </p>
4324 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4325 <h3 class="title">Note</h3>
4326                   If you do not wish the alternate transfer source
4327                   to be used, you should set
4328                   <span><strong class="command">use-alt-transfer-source</strong></span>
4329                   appropriately and you should not depend upon
4330                   getting an answer back to the first refresh
4331                   query.
4332                 </div>
4333 </dd>
4334 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
4335 <dd><p>
4336                   An alternate transfer source if the one listed in
4337                   <span><strong class="command">transfer-source-v6</strong></span> fails and
4338                   <span><strong class="command">use-alt-transfer-source</strong></span> is
4339                   set.
4340                 </p></dd>
4341 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
4342 <dd><p>
4343                   Use the alternate transfer sources or not.  If views are
4344                   specified this defaults to <span><strong class="command">no</strong></span>
4345                   otherwise it defaults to
4346                   <span><strong class="command">yes</strong></span> (for BIND 8
4347                   compatibility).
4348                 </p></dd>
4349 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
4350 <dd>
4351 <p><span><strong class="command">notify-source</strong></span>
4352                   determines which local source address, and
4353                   optionally UDP port, will be used to send NOTIFY
4354                   messages.  This address must appear in the slave
4355                   server's <span><strong class="command">masters</strong></span> zone clause or
4356                   in an <span><strong class="command">allow-notify</strong></span> clause.  This
4357                   statement sets the <span><strong class="command">notify-source</strong></span>
4358                   for all zones, but can be overridden on a per-zone or
4359                   per-view basis by including a
4360                   <span><strong class="command">notify-source</strong></span> statement within
4361                   the <span><strong class="command">zone</strong></span> or
4362                   <span><strong class="command">view</strong></span> block in the configuration
4363                   file.
4364                 </p>
4365 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4366 <h3 class="title">Note</h3>
4367 <p>
4368                     Solaris 2.5.1 and earlier does not support setting the
4369                     source address for TCP sockets.
4370                   </p>
4371 </div>
4372 </dd>
4373 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
4374 <dd><p>
4375                   Like <span><strong class="command">notify-source</strong></span>,
4376                   but applies to notify messages sent to IPv6 addresses.
4377                 </p></dd>
4378 </dl></div>
4379 </div>
4380 <div class="sect3" lang="en">
4381 <div class="titlepage"><div><div><h4 class="title">
4382 <a name="id2585531"></a>UDP Port Lists</h4></div></div></div>
4383 <p>
4384             <span><strong class="command">use-v4-udp-ports</strong></span>,
4385             <span><strong class="command">avoid-v4-udp-ports</strong></span>,
4386             <span><strong class="command">use-v6-udp-ports</strong></span>, and
4387             <span><strong class="command">avoid-v6-udp-ports</strong></span>
4388             specify a list of IPv4 and IPv6 UDP ports that will be
4389             used or not used as source ports for UDP messages.
4390             See <a href="Bv9ARM.ch06.html#query_address" title="Query Address">the section called &#8220;Query Address&#8221;</a> about how the
4391             available ports are determined.
4392             For example, with the following configuration
4393           </p>
4394 <pre class="programlisting">
4395 use-v6-udp-ports { range 32768 65535; };
4396 avoid-v6-udp-ports { 40000; range 50000 60000; };
4397 </pre>
4398 <p>
4399              UDP ports of IPv6 messages sent
4400              from <span><strong class="command">named</strong></span> will be in one
4401              of the following ranges: 32768 to 39999, 40001 to 49999,
4402              and 60001 to 65535.
4403            </p>
4404 <p>
4405              <span><strong class="command">avoid-v4-udp-ports</strong></span> and
4406              <span><strong class="command">avoid-v6-udp-ports</strong></span> can be used
4407              to prevent <span><strong class="command">named</strong></span> from choosing as its random source port a
4408              port that is blocked by your firewall or a port that is
4409              used by other applications;
4410              if a query went out with a source port blocked by a
4411              firewall, the
4412              answer would not get by the firewall and the name server would
4413              have to query again.
4414              Note: the desired range can also be represented only with
4415              <span><strong class="command">use-v4-udp-ports</strong></span> and
4416              <span><strong class="command">use-v6-udp-ports</strong></span>, and the
4417              <span><strong class="command">avoid-</strong></span> options are redundant in that
4418              sense; they are provided for backward compatibility and
4419              to possibly simplify the port specification.
4420            </p>
4421 </div>
4422 <div class="sect3" lang="en">
4423 <div class="titlepage"><div><div><h4 class="title">
4424 <a name="id2585591"></a>Operating System Resource Limits</h4></div></div></div>
4425 <p>
4426             The server's usage of many system resources can be limited.
4427             Scaled values are allowed when specifying resource limits.  For
4428             example, <span><strong class="command">1G</strong></span> can be used instead of
4429             <span><strong class="command">1073741824</strong></span> to specify a limit of
4430             one
4431             gigabyte. <span><strong class="command">unlimited</strong></span> requests
4432             unlimited use, or the
4433             maximum available amount. <span><strong class="command">default</strong></span>
4434             uses the limit
4435             that was in force when the server was started. See the description
4436             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>.
4437           </p>
4438 <p>
4439             The following options set operating system resource limits for
4440             the name server process.  Some operating systems don't support
4441             some or
4442             any of the limits. On such systems, a warning will be issued if
4443             the
4444             unsupported limit is used.
4445           </p>
4446 <div class="variablelist"><dl>
4447 <dt><span class="term"><span><strong class="command">coresize</strong></span></span></dt>
4448 <dd><p>
4449                   The maximum size of a core dump. The default
4450                   is <code class="literal">default</code>.
4451                 </p></dd>
4452 <dt><span class="term"><span><strong class="command">datasize</strong></span></span></dt>
4453 <dd><p>
4454                   The maximum amount of data memory the server
4455                   may use. The default is <code class="literal">default</code>.
4456                   This is a hard limit on server memory usage.
4457                   If the server attempts to allocate memory in excess of this
4458                   limit, the allocation will fail, which may in turn leave
4459                   the server unable to perform DNS service.  Therefore,
4460                   this option is rarely useful as a way of limiting the
4461                   amount of memory used by the server, but it can be used
4462                   to raise an operating system data size limit that is
4463                   too small by default.  If you wish to limit the amount
4464                   of memory used by the server, use the
4465                   <span><strong class="command">max-cache-size</strong></span> and
4466                   <span><strong class="command">recursive-clients</strong></span>
4467                   options instead.
4468                 </p></dd>
4469 <dt><span class="term"><span><strong class="command">files</strong></span></span></dt>
4470 <dd><p>
4471                   The maximum number of files the server
4472                   may have open concurrently. The default is <code class="literal">unlimited</code>.
4473                 </p></dd>
4474 <dt><span class="term"><span><strong class="command">stacksize</strong></span></span></dt>
4475 <dd><p>
4476                   The maximum amount of stack memory the server
4477                   may use. The default is <code class="literal">default</code>.
4478                 </p></dd>
4479 </dl></div>
4480 </div>
4481 <div class="sect3" lang="en">
4482 <div class="titlepage"><div><div><h4 class="title">
4483 <a name="server_resource_limits"></a>Server  Resource Limits</h4></div></div></div>
4484 <p>
4485             The following options set limits on the server's
4486             resource consumption that are enforced internally by the
4487             server rather than the operating system.
4488           </p>
4489 <div class="variablelist"><dl>
4490 <dt><span class="term"><span><strong class="command">max-ixfr-log-size</strong></span></span></dt>
4491 <dd><p>
4492                   This option is obsolete; it is accepted
4493                   and ignored for BIND 8 compatibility.  The option
4494                   <span><strong class="command">max-journal-size</strong></span> performs a
4495                   similar function in BIND 9.
4496                 </p></dd>
4497 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
4498 <dd><p>
4499                   Sets a maximum size for each journal file
4500                   (see <a href="Bv9ARM.ch04.html#journal" title="The journal file">the section called &#8220;The journal file&#8221;</a>).  When the journal file
4501                   approaches
4502                   the specified size, some of the oldest transactions in the
4503                   journal
4504                   will be automatically removed.  The default is
4505                   <code class="literal">unlimited</code>.
4506                   This may also be set on a per-zone basis.
4507                 </p></dd>
4508 <dt><span class="term"><span><strong class="command">host-statistics-max</strong></span></span></dt>
4509 <dd><p>
4510                   In BIND 8, specifies the maximum number of host statistics
4511                   entries to be kept.
4512                   Not implemented in BIND 9.
4513                 </p></dd>
4514 <dt><span class="term"><span><strong class="command">recursive-clients</strong></span></span></dt>
4515 <dd><p>
4516                   The maximum number of simultaneous recursive lookups
4517                   the server will perform on behalf of clients.  The default
4518                   is
4519                   <code class="literal">1000</code>.  Because each recursing
4520                   client uses a fair
4521                   bit of memory, on the order of 20 kilobytes, the value of
4522                   the
4523                   <span><strong class="command">recursive-clients</strong></span> option may
4524                   have to be decreased
4525                   on hosts with limited memory.
4526                 </p></dd>
4527 <dt><span class="term"><span><strong class="command">tcp-clients</strong></span></span></dt>
4528 <dd><p>
4529                   The maximum number of simultaneous client TCP
4530                   connections that the server will accept.
4531                   The default is <code class="literal">100</code>.
4532                 </p></dd>
4533 <dt><span class="term"><span><strong class="command">reserved-sockets</strong></span></span></dt>
4534 <dd>
4535 <p>
4536                   The number of file descriptors reserved for TCP, stdio,
4537                   etc.  This needs to be big enough to cover the number of
4538                   interfaces <span><strong class="command">named</strong></span> listens on, <span><strong class="command">tcp-clients</strong></span> as well as
4539                   to provide room for outgoing TCP queries and incoming zone
4540                   transfers.  The default is <code class="literal">512</code>.
4541                   The minimum value is <code class="literal">128</code> and the
4542                   maximum value is <code class="literal">128</code> less than
4543                   maxsockets (-S).  This option may be removed in the future.
4544                 </p>
4545 <p>
4546                   This option has little effect on Windows.
4547                 </p>
4548 </dd>
4549 <dt><span class="term"><span><strong class="command">max-cache-size</strong></span></span></dt>
4550 <dd><p>
4551                   The maximum amount of memory to use for the
4552                   server's cache, in bytes.
4553                   When the amount of data in the cache
4554                   reaches this limit, the server will cause records to expire
4555                   prematurely based on an LRU based strategy so that
4556                   the limit is not exceeded.
4557                   A value of 0 is special, meaning that
4558                   records are purged from the cache only when their
4559                   TTLs expire.
4560                   Another special keyword <strong class="userinput"><code>unlimited</code></strong>
4561                   means the maximum value of 32-bit unsigned integers
4562                   (0xffffffff), which may not have the same effect as
4563                   0 on machines that support more than 32 bits of
4564                   memory space.
4565                   Any positive values less than 2MB will be ignored reset
4566                   to 2MB.
4567                   In a server with multiple views, the limit applies
4568                   separately to the cache of each view.
4569                   The default is 0.
4570                 </p></dd>
4571 <dt><span class="term"><span><strong class="command">tcp-listen-queue</strong></span></span></dt>
4572 <dd><p>
4573                   The listen queue depth.  The default and minimum is 3.
4574                   If the kernel supports the accept filter "dataready" this
4575                   also controls how
4576                   many TCP connections that will be queued in kernel space
4577                   waiting for
4578                   some data before being passed to accept.  Values less than 3
4579                   will be
4580                   silently raised.
4581                 </p></dd>
4582 </dl></div>
4583 </div>
4584 <div class="sect3" lang="en">
4585 <div class="titlepage"><div><div><h4 class="title">
4586 <a name="id2586082"></a>Periodic Task Intervals</h4></div></div></div>
4587 <div class="variablelist"><dl>
4588 <dt><span class="term"><span><strong class="command">cleaning-interval</strong></span></span></dt>
4589 <dd><p>
4590                   This interval is effectively obsolete.  Previously,
4591                   the server would remove expired resource records
4592                   from the cache every <span><strong class="command">cleaning-interval</strong></span> minutes.
4593                   <acronym class="acronym">BIND</acronym> 9 now manages cache
4594                   memory in a more sophisticated manner and does not
4595                   rely on the periodic cleaning any more.
4596                   Specifying this option therefore has no effect on
4597                   the server's behavior.
4598                 </p></dd>
4599 <dt><span class="term"><span><strong class="command">heartbeat-interval</strong></span></span></dt>
4600 <dd><p>
4601                   The server will perform zone maintenance tasks
4602                   for all zones marked as <span><strong class="command">dialup</strong></span> whenever this
4603                   interval expires. The default is 60 minutes. Reasonable
4604                   values are up
4605                   to 1 day (1440 minutes).  The maximum value is 28 days
4606                   (40320 minutes).
4607                   If set to 0, no zone maintenance for these zones will occur.
4608                 </p></dd>
4609 <dt><span class="term"><span><strong class="command">interface-interval</strong></span></span></dt>
4610 <dd><p>
4611                   The server will scan the network interface list
4612                   every <span><strong class="command">interface-interval</strong></span>
4613                   minutes. The default
4614                   is 60 minutes. The maximum value is 28 days (40320 minutes).
4615                   If set to 0, interface scanning will only occur when
4616                   the configuration file is  loaded. After the scan, the
4617                   server will
4618                   begin listening for queries on any newly discovered
4619                   interfaces (provided they are allowed by the
4620                   <span><strong class="command">listen-on</strong></span> configuration), and
4621                   will
4622                   stop listening on interfaces that have gone away.
4623                 </p></dd>
4624 <dt><span class="term"><span><strong class="command">statistics-interval</strong></span></span></dt>
4625 <dd>
4626 <p>
4627                   Name server statistics will be logged
4628                   every <span><strong class="command">statistics-interval</strong></span>
4629                   minutes. The default is
4630                   60. The maximum value is 28 days (40320 minutes).
4631                   If set to 0, no statistics will be logged.
4632                   </p>
4633 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4634 <h3 class="title">Note</h3>
4635 <p>
4636                     Not yet implemented in
4637                     <acronym class="acronym">BIND</acronym> 9.
4638                   </p>
4639 </div>
4640 </dd>
4641 </dl></div>
4642 </div>
4643 <div class="sect3" lang="en">
4644 <div class="titlepage"><div><div><h4 class="title">
4645 <a name="topology"></a>Topology</h4></div></div></div>
4646 <p>
4647             All other things being equal, when the server chooses a name
4648             server
4649             to query from a list of name servers, it prefers the one that is
4650             topologically closest to itself. The <span><strong class="command">topology</strong></span> statement
4651             takes an <span><strong class="command">address_match_list</strong></span> and
4652             interprets it
4653             in a special way. Each top-level list element is assigned a
4654             distance.
4655             Non-negated elements get a distance based on their position in the
4656             list, where the closer the match is to the start of the list, the
4657             shorter the distance is between it and the server. A negated match
4658             will be assigned the maximum distance from the server. If there
4659             is no match, the address will get a distance which is further than
4660             any non-negated list element, and closer than any negated element.
4661             For example,
4662           </p>
4663 <pre class="programlisting">topology {
4664     10/8;
4665     !1.2.3/24;
4666     { 1.2/16; 3/8; };
4667 };</pre>
4668 <p>
4669             will prefer servers on network 10 the most, followed by hosts
4670             on network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the
4671             exception of hosts on network 1.2.3 (netmask 255.255.255.0), which
4672             is preferred least of all.
4673           </p>
4674 <p>
4675             The default topology is
4676           </p>
4677 <pre class="programlisting">    topology { localhost; localnets; };
4678 </pre>
4679 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4680 <h3 class="title">Note</h3>
4681 <p>
4682               The <span><strong class="command">topology</strong></span> option
4683               is not implemented in <acronym class="acronym">BIND</acronym> 9.
4684             </p>
4685 </div>
4686 </div>
4687 <div class="sect3" lang="en">
4688 <div class="titlepage"><div><div><h4 class="title">
4689 <a name="the_sortlist_statement"></a>The <span><strong class="command">sortlist</strong></span> Statement</h4></div></div></div>
4690 <p>
4691             The response to a DNS query may consist of multiple resource
4692             records (RRs) forming a resource records set (RRset).
4693             The name server will normally return the
4694             RRs within the RRset in an indeterminate order
4695             (but see the <span><strong class="command">rrset-order</strong></span>
4696             statement in <a href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">the section called &#8220;RRset Ordering&#8221;</a>).
4697             The client resolver code should rearrange the RRs as appropriate,
4698             that is, using any addresses on the local net in preference to
4699             other addresses.
4700             However, not all resolvers can do this or are correctly
4701             configured.
4702             When a client is using a local server, the sorting can be performed
4703             in the server, based on the client's address. This only requires
4704             configuring the name servers, not all the clients.
4705           </p>
4706 <p>
4707             The <span><strong class="command">sortlist</strong></span> statement (see below)
4708             takes
4709             an <span><strong class="command">address_match_list</strong></span> and
4710             interprets it even
4711             more specifically than the <span><strong class="command">topology</strong></span>
4712             statement
4713             does (<a href="Bv9ARM.ch06.html#topology" title="Topology">the section called &#8220;Topology&#8221;</a>).
4714             Each top level statement in the <span><strong class="command">sortlist</strong></span> must
4715             itself be an explicit <span><strong class="command">address_match_list</strong></span> with
4716             one or two elements. The first element (which may be an IP
4717             address,
4718             an IP prefix, an ACL name or a nested <span><strong class="command">address_match_list</strong></span>)
4719             of each top level list is checked against the source address of
4720             the query until a match is found.
4721           </p>
4722 <p>
4723             Once the source address of the query has been matched, if
4724             the top level statement contains only one element, the actual
4725             primitive
4726             element that matched the source address is used to select the
4727             address
4728             in the response to move to the beginning of the response. If the
4729             statement is a list of two elements, then the second element is
4730             treated the same as the <span><strong class="command">address_match_list</strong></span> in
4731             a <span><strong class="command">topology</strong></span> statement. Each top
4732             level element
4733             is assigned a distance and the address in the response with the
4734             minimum
4735             distance is moved to the beginning of the response.
4736           </p>
4737 <p>
4738             In the following example, any queries received from any of
4739             the addresses of the host itself will get responses preferring
4740             addresses
4741             on any of the locally connected networks. Next most preferred are
4742             addresses
4743             on the 192.168.1/24 network, and after that either the
4744             192.168.2/24
4745             or
4746             192.168.3/24 network with no preference shown between these two
4747             networks. Queries received from a host on the 192.168.1/24 network
4748             will prefer other addresses on that network to the 192.168.2/24
4749             and
4750             192.168.3/24 networks. Queries received from a host on the
4751             192.168.4/24
4752             or the 192.168.5/24 network will only prefer other addresses on
4753             their directly connected networks.
4754           </p>
4755 <pre class="programlisting">sortlist {
4756     // IF the local host
4757     // THEN first fit on the following nets
4758     { localhost;
4759         { localnets;
4760             192.168.1/24;
4761             { 192.168.2/24; 192.168.3/24; }; }; };
4762     // IF on class C 192.168.1 THEN use .1, or .2 or .3
4763     { 192.168.1/24;
4764         { 192.168.1/24;
4765             { 192.168.2/24; 192.168.3/24; }; }; };
4766     // IF on class C 192.168.2 THEN use .2, or .1 or .3
4767     { 192.168.2/24;
4768         { 192.168.2/24;
4769             { 192.168.1/24; 192.168.3/24; }; }; };
4770     // IF on class C 192.168.3 THEN use .3, or .1 or .2
4771     { 192.168.3/24;
4772         { 192.168.3/24;
4773             { 192.168.1/24; 192.168.2/24; }; }; };
4774     // IF .4 or .5 THEN prefer that net
4775     { { 192.168.4/24; 192.168.5/24; };
4776     };
4777 };</pre>
4778 <p>
4779             The following example will give reasonable behavior for the
4780             local host and hosts on directly connected networks. It is similar
4781             to the behavior of the address sort in <acronym class="acronym">BIND</acronym> 4.9.x. Responses sent
4782             to queries from the local host will favor any of the directly
4783             connected
4784             networks. Responses sent to queries from any other hosts on a
4785             directly
4786             connected network will prefer addresses on that same network.
4787             Responses
4788             to other queries will not be sorted.
4789           </p>
4790 <pre class="programlisting">sortlist {
4791            { localhost; localnets; };
4792            { localnets; };
4793 };
4794 </pre>
4795 </div>
4796 <div class="sect3" lang="en">
4797 <div class="titlepage"><div><div><h4 class="title">
4798 <a name="rrset_ordering"></a>RRset Ordering</h4></div></div></div>
4799 <p>
4800             When multiple records are returned in an answer it may be
4801             useful to configure the order of the records placed into the
4802             response.
4803             The <span><strong class="command">rrset-order</strong></span> statement permits
4804             configuration
4805             of the ordering of the records in a multiple record response.
4806             See also the <span><strong class="command">sortlist</strong></span> statement,
4807             <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>.
4808           </p>
4809 <p>
4810             An <span><strong class="command">order_spec</strong></span> is defined as
4811             follows:
4812           </p>
4813 <p>
4814             [<span class="optional">class <em class="replaceable"><code>class_name</code></em></span>]
4815             [<span class="optional">type <em class="replaceable"><code>type_name</code></em></span>]
4816             [<span class="optional">name <em class="replaceable"><code>"domain_name"</code></em></span>]
4817             order <em class="replaceable"><code>ordering</code></em>
4818           </p>
4819 <p>
4820             If no class is specified, the default is <span><strong class="command">ANY</strong></span>.
4821             If no type is specified, the default is <span><strong class="command">ANY</strong></span>.
4822             If no name is specified, the default is "<span><strong class="command">*</strong></span>" (asterisk).
4823           </p>
4824 <p>
4825             The legal values for <span><strong class="command">ordering</strong></span> are:
4826           </p>
4827 <div class="informaltable"><table border="1">
4828 <colgroup>
4829 <col>
4830 <col>
4831 </colgroup>
4832 <tbody>
4833 <tr>
4834 <td>
4835                     <p><span><strong class="command">fixed</strong></span></p>
4836                   </td>
4837 <td>
4838                     <p>
4839                       Records are returned in the order they
4840                       are defined in the zone file.
4841                     </p>
4842                   </td>
4843 </tr>
4844 <tr>
4845 <td>
4846                     <p><span><strong class="command">random</strong></span></p>
4847                   </td>
4848 <td>
4849                     <p>
4850                       Records are returned in some random order.
4851                     </p>
4852                   </td>
4853 </tr>
4854 <tr>
4855 <td>
4856                     <p><span><strong class="command">cyclic</strong></span></p>
4857                   </td>
4858 <td>
4859                     <p>
4860                       Records are returned in a cyclic round-robin order.
4861                     </p>
4862                     <p>
4863                       If <acronym class="acronym">BIND</acronym> is configured with the
4864                       "--enable-fixed-rrset" option at compile time, then
4865                       the initial ordering of the RRset will match the
4866                       one specified in the zone file.
4867                     </p>
4868                   </td>
4869 </tr>
4870 </tbody>
4871 </table></div>
4872 <p>
4873             For example:
4874           </p>
4875 <pre class="programlisting">rrset-order {
4876    class IN type A name "host.example.com" order random;
4877    order cyclic;
4878 };
4879 </pre>
4880 <p>
4881             will cause any responses for type A records in class IN that
4882             have "<code class="literal">host.example.com</code>" as a
4883             suffix, to always be returned
4884             in random order. All other records are returned in cyclic order.
4885           </p>
4886 <p>
4887             If multiple <span><strong class="command">rrset-order</strong></span> statements
4888             appear,
4889             they are not combined &#8212; the last one applies.
4890           </p>
4891 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4892 <h3 class="title">Note</h3>
4893 <p>
4894               In this release of <acronym class="acronym">BIND</acronym> 9, the
4895               <span><strong class="command">rrset-order</strong></span> statement does not support
4896               "fixed" ordering by default.  Fixed ordering can be enabled
4897               at compile time by specifying "--enable-fixed-rrset" on
4898               the "configure" command line.
4899             </p>
4900 </div>
4901 </div>
4902 <div class="sect3" lang="en">
4903 <div class="titlepage"><div><div><h4 class="title">
4904 <a name="tuning"></a>Tuning</h4></div></div></div>
4905 <div class="variablelist"><dl>
4906 <dt><span class="term"><span><strong class="command">lame-ttl</strong></span></span></dt>
4907 <dd>
4908 <p>
4909                   Sets the number of seconds to cache a
4910                   lame server indication. 0 disables caching. (This is
4911                   <span class="bold"><strong>NOT</strong></span> recommended.)
4912                   The default is <code class="literal">600</code> (10 minutes) and the
4913                   maximum value is
4914                   <code class="literal">1800</code> (30 minutes).
4915                 </p>
4916 <p>
4917                   Lame-ttl also controls the amount of time DNSSEC
4918                   validation failures are cached.  There is a minimum
4919                   of 30 seconds applied to bad cache entries if the
4920                   lame-ttl is set to less than 30 seconds.
4921                 </p>
4922 </dd>
4923 <dt><span class="term"><span><strong class="command">max-ncache-ttl</strong></span></span></dt>
4924 <dd><p>
4925                   To reduce network traffic and increase performance,
4926                   the server stores negative answers. <span><strong class="command">max-ncache-ttl</strong></span> is
4927                   used to set a maximum retention time for these answers in
4928                   the server
4929                   in seconds. The default
4930                   <span><strong class="command">max-ncache-ttl</strong></span> is <code class="literal">10800</code> seconds (3 hours).
4931                   <span><strong class="command">max-ncache-ttl</strong></span> cannot exceed
4932                   7 days and will
4933                   be silently truncated to 7 days if set to a greater value.
4934                 </p></dd>
4935 <dt><span class="term"><span><strong class="command">max-cache-ttl</strong></span></span></dt>
4936 <dd><p>
4937                   Sets the maximum time for which the server will
4938                   cache ordinary (positive) answers. The default is
4939                   one week (7 days).
4940                   A value of zero may cause all queries to return
4941                   SERVFAIL, because of lost caches of intermediate
4942                   RRsets (such as NS and glue AAAA/A records) in the
4943                   resolution process.
4944                 </p></dd>
4945 <dt><span class="term"><span><strong class="command">min-roots</strong></span></span></dt>
4946 <dd>
4947 <p>
4948                   The minimum number of root servers that
4949                   is required for a request for the root servers to be
4950                   accepted. The default
4951                   is <strong class="userinput"><code>2</code></strong>.
4952                 </p>
4953 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4954 <h3 class="title">Note</h3>
4955 <p>
4956                     Not implemented in <acronym class="acronym">BIND</acronym> 9.
4957                   </p>
4958 </div>
4959 </dd>
4960 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
4961 <dd>
4962 <p>
4963                   Specifies the number of days into the future when
4964                   DNSSEC signatures automatically generated as a
4965                   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
4966                   is an optional second field which specifies how
4967                   long before expiry that the signatures will be
4968                   regenerated.  If not specified, the signatures will
4969                   be regenerated at 1/4 of base interval.  The second
4970                   field is specified in days if the base interval is
4971                   greater than 7 days otherwise it is specified in hours.
4972                   The default base interval is <code class="literal">30</code> days
4973                   giving a re-signing interval of 7 1/2 days.  The maximum
4974                   values are 10 years (3660 days).
4975                 </p>
4976 <p>
4977                   The signature inception time is unconditionally
4978                   set to one hour before the current time to allow
4979                   for a limited amount of clock skew.
4980                 </p>
4981 <p>
4982                   The <span><strong class="command">sig-validity-interval</strong></span>
4983                   should be, at least, several multiples of the SOA
4984                   expire interval to allow for reasonable interaction
4985                   between the various timer and expiry dates.
4986                 </p>
4987 </dd>
4988 <dt><span class="term"><span><strong class="command">sig-signing-nodes</strong></span></span></dt>
4989 <dd><p>
4990                   Specify the maximum number of nodes to be
4991                   examined in each quantum when signing a zone with
4992                   a new DNSKEY. The default is
4993                   <code class="literal">100</code>.
4994                 </p></dd>
4995 <dt><span class="term"><span><strong class="command">sig-signing-signatures</strong></span></span></dt>
4996 <dd><p>
4997                   Specify a threshold number of signatures that
4998                   will terminate processing a quantum when signing
4999                   a zone with a new DNSKEY.  The default is
5000                   <code class="literal">10</code>.
5001                 </p></dd>
5002 <dt><span class="term"><span><strong class="command">sig-signing-type</strong></span></span></dt>
5003 <dd>
5004 <p>
5005                   Specify a private RDATA type to be used when generating
5006                   key signing records.  The default is
5007                   <code class="literal">65534</code>.
5008                 </p>
5009 <p>
5010                   It is expected that this parameter may be removed
5011                   in a future version once there is a standard type.
5012                 </p>
5013 </dd>
5014 <dt>
5015 <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>
5016 </dt>
5017 <dd>
5018 <p>
5019                   These options control the server's behavior on refreshing a
5020                   zone
5021                   (querying for SOA changes) or retrying failed transfers.
5022                   Usually the SOA values for the zone are used, but these
5023                   values
5024                   are set by the master, giving slave server administrators
5025                   little
5026                   control over their contents.
5027                 </p>
5028 <p>
5029                   These options allow the administrator to set a minimum and
5030                   maximum
5031                   refresh and retry time either per-zone, per-view, or
5032                   globally.
5033                   These options are valid for slave and stub zones,
5034                   and clamp the SOA refresh and retry times to the specified
5035                   values.
5036                 </p>
5037 <p>
5038                   The following defaults apply.
5039                   <span><strong class="command">min-refresh-time</strong></span> 300 seconds,
5040                   <span><strong class="command">max-refresh-time</strong></span> 2419200 seconds
5041                   (4 weeks), <span><strong class="command">min-retry-time</strong></span> 500 seconds,
5042                   and <span><strong class="command">max-retry-time</strong></span> 1209600 seconds
5043                   (2 weeks).
5044                 </p>
5045 </dd>
5046 <dt><span class="term"><span><strong class="command">edns-udp-size</strong></span></span></dt>
5047 <dd>
5048 <p>
5049                   Sets the advertised EDNS UDP buffer size in bytes
5050                   to control the size of packets received.
5051                   Valid values are 512 to 4096 (values outside this range
5052                   will be silently adjusted).  The default value
5053                   is 4096.  The usual reason for setting
5054                   <span><strong class="command">edns-udp-size</strong></span> to a non-default
5055                   value is to get UDP answers to pass through broken
5056                   firewalls that block fragmented packets and/or
5057                   block UDP packets that are greater than 512 bytes.
5058                 </p>
5059 <p>
5060                   <span><strong class="command">named</strong></span> will fallback to using 512 bytes
5061                   if it get a series of timeout at the initial value.  512
5062                   bytes is not being offered to encourage sites to fix their
5063                   firewalls.  Small EDNS UDP sizes will result in the
5064                   excessive use of TCP.
5065                 </p>
5066 </dd>
5067 <dt><span class="term"><span><strong class="command">max-udp-size</strong></span></span></dt>
5068 <dd>
5069 <p>
5070                   Sets the maximum EDNS UDP message size
5071                   <span><strong class="command">named</strong></span> will send in bytes.
5072                   Valid values are 512 to 4096 (values outside this
5073                   range will be silently adjusted).  The default
5074                   value is 4096.  The usual reason for setting
5075                   <span><strong class="command">max-udp-size</strong></span> to a non-default
5076                   value is to get UDP answers to pass through broken
5077                   firewalls that block fragmented packets and/or
5078                   block UDP packets that are greater than 512 bytes.
5079                   This is independent of the advertised receive
5080                   buffer (<span><strong class="command">edns-udp-size</strong></span>).
5081                 </p>
5082 <p>
5083                   Setting this to a low value will encourage additional
5084                   TCP traffic to the nameserver.
5085                 </p>
5086 </dd>
5087 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
5088 <dd><p>Specifies
5089                   the file format of zone files (see
5090                   <a href="Bv9ARM.ch06.html#zonefile_format" title="Additional File Formats">the section called &#8220;Additional File Formats&#8221;</a>).
5091                   The default value is <code class="constant">text</code>, which is the
5092                   standard textual representation.  Files in other formats
5093                   than <code class="constant">text</code> are typically expected
5094                   to be generated by the <span><strong class="command">named-compilezone</strong></span> tool.
5095                   Note that when a zone file in a different format than
5096                   <code class="constant">text</code> is loaded, <span><strong class="command">named</strong></span>
5097                   may omit some of the checks which would be performed for a
5098                   file in the <code class="constant">text</code> format.  In particular,
5099                   <span><strong class="command">check-names</strong></span> checks do not apply
5100                   for the <code class="constant">raw</code> format.  This means
5101                   a zone file in the <code class="constant">raw</code> format
5102                   must be generated with the same check level as that
5103                   specified in the <span><strong class="command">named</strong></span> configuration
5104                   file.  This statement sets the
5105                   <span><strong class="command">masterfile-format</strong></span> for all zones,
5106                   but can be overridden on a per-zone or per-view basis
5107                   by including a <span><strong class="command">masterfile-format</strong></span>
5108                   statement within the <span><strong class="command">zone</strong></span> or
5109                   <span><strong class="command">view</strong></span> block in the configuration
5110                   file.
5111                 </p></dd>
5112 <dt>
5113 <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>
5114 </dt>
5115 <dd>
5116 <p>These set the
5117                   initial value (minimum) and maximum number of recursive
5118                   simultaneous clients for any given query
5119                   (&lt;qname,qtype,qclass&gt;) that the server will accept
5120                   before dropping additional clients.  <span><strong class="command">named</strong></span> will attempt to
5121                   self tune this value and changes will be logged.  The
5122                   default values are 10 and 100.
5123                 </p>
5124 <p>
5125                   This value should reflect how many queries come in for
5126                   a given name in the time it takes to resolve that name.
5127                   If the number of queries exceed this value, <span><strong class="command">named</strong></span> will
5128                   assume that it is dealing with a non-responsive zone
5129                   and will drop additional queries.  If it gets a response
5130                   after dropping queries, it will raise the estimate.  The
5131                   estimate will then be lowered in 20 minutes if it has
5132                   remained unchanged.
5133                 </p>
5134 <p>
5135                   If <span><strong class="command">clients-per-query</strong></span> is set to zero,
5136                   then there is no limit on the number of clients per query
5137                   and no queries will be dropped.
5138                 </p>
5139 <p>
5140                   If <span><strong class="command">max-clients-per-query</strong></span> is set to zero,
5141                   then there is no upper bound other than imposed by
5142                   <span><strong class="command">recursive-clients</strong></span>.
5143                 </p>
5144 </dd>
5145 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
5146 <dd>
5147 <p>
5148                   The delay, in seconds, between sending sets of notify
5149                   messages for a zone.  The default is five (5) seconds.
5150                 </p>
5151 <p>
5152                   The overall rate that NOTIFY messages are sent for all
5153                   zones is controlled by <span><strong class="command">serial-query-rate</strong></span>.
5154                 </p>
5155 </dd>
5156 </dl></div>
5157 </div>
5158 <div class="sect3" lang="en">
5159 <div class="titlepage"><div><div><h4 class="title">
5160 <a name="builtin"></a>Built-in server information zones</h4></div></div></div>
5161 <p>
5162             The server provides some helpful diagnostic information
5163             through a number of built-in zones under the
5164             pseudo-top-level-domain <code class="literal">bind</code> in the
5165             <span><strong class="command">CHAOS</strong></span> class.  These zones are part
5166             of a
5167             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
5168             class
5169             <span><strong class="command">CHAOS</strong></span> which is separate from the
5170             default view of
5171             class <span><strong class="command">IN</strong></span>; therefore, any global
5172             server options
5173             such as <span><strong class="command">allow-query</strong></span> do not apply
5174             the these zones.
5175             If you feel the need to disable these zones, use the options
5176             below, or hide the built-in <span><strong class="command">CHAOS</strong></span>
5177             view by
5178             defining an explicit view of class <span><strong class="command">CHAOS</strong></span>
5179             that matches all clients.
5180           </p>
5181 <div class="variablelist"><dl>
5182 <dt><span class="term"><span><strong class="command">version</strong></span></span></dt>
5183 <dd><p>
5184                   The version the server should report
5185                   via a query of the name <code class="literal">version.bind</code>
5186                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5187                   The default is the real version number of this server.
5188                   Specifying <span><strong class="command">version none</strong></span>
5189                   disables processing of the queries.
5190                 </p></dd>
5191 <dt><span class="term"><span><strong class="command">hostname</strong></span></span></dt>
5192 <dd><p>
5193                   The hostname the server should report via a query of
5194                   the name <code class="filename">hostname.bind</code>
5195                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5196                   This defaults to the hostname of the machine hosting the
5197                   name server as
5198                   found by the gethostname() function.  The primary purpose of such queries
5199                   is to
5200                   identify which of a group of anycast servers is actually
5201                   answering your queries.  Specifying <span><strong class="command">hostname none;</strong></span>
5202                   disables processing of the queries.
5203                 </p></dd>
5204 <dt><span class="term"><span><strong class="command">server-id</strong></span></span></dt>
5205 <dd><p>
5206                   The ID the server should report when receiving a Name
5207                   Server Identifier (NSID) query, or a query of the name
5208                   <code class="filename">ID.SERVER</code> with type
5209                   <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
5210                   The primary purpose of such queries is to
5211                   identify which of a group of anycast servers is actually
5212                   answering your queries.  Specifying <span><strong class="command">server-id none;</strong></span>
5213                   disables processing of the queries.
5214                   Specifying <span><strong class="command">server-id hostname;</strong></span> will cause <span><strong class="command">named</strong></span> to
5215                   use the hostname as found by the gethostname() function.
5216                   The default <span><strong class="command">server-id</strong></span> is <span><strong class="command">none</strong></span>.
5217                 </p></dd>
5218 </dl></div>
5219 </div>
5220 <div class="sect3" lang="en">
5221 <div class="titlepage"><div><div><h4 class="title">
5222 <a name="empty"></a>Built-in Empty Zones</h4></div></div></div>
5223 <p>
5224             Named has some built-in empty zones (SOA and NS records only).
5225             These are for zones that should normally be answered locally
5226             and which queries should not be sent to the Internet's root
5227             servers.  The official servers which cover these namespaces
5228             return NXDOMAIN responses to these queries.  In particular,
5229             these cover the reverse namespaces for addresses from
5230             RFC 1918, RFC 4193, and RFC 5737.  They also include the
5231             reverse namespace for IPv6 local address (locally assigned),
5232             IPv6 link local addresses, the IPv6 loopback address and the
5233             IPv6 unknown address.
5234           </p>
5235 <p>
5236             Named will attempt to determine if a built-in zone already exists
5237             or is active (covered by a forward-only forwarding declaration)
5238             and will not create an empty zone in that case.
5239           </p>
5240 <p>
5241             The current list of empty zones is:
5242             </p>
5243 <div class="itemizedlist"><ul type="disc">
5244 <li>10.IN-ADDR.ARPA</li>
5245 <li>16.172.IN-ADDR.ARPA</li>
5246 <li>17.172.IN-ADDR.ARPA</li>
5247 <li>18.172.IN-ADDR.ARPA</li>
5248 <li>19.172.IN-ADDR.ARPA</li>
5249 <li>20.172.IN-ADDR.ARPA</li>
5250 <li>21.172.IN-ADDR.ARPA</li>
5251 <li>22.172.IN-ADDR.ARPA</li>
5252 <li>23.172.IN-ADDR.ARPA</li>
5253 <li>24.172.IN-ADDR.ARPA</li>
5254 <li>25.172.IN-ADDR.ARPA</li>
5255 <li>26.172.IN-ADDR.ARPA</li>
5256 <li>27.172.IN-ADDR.ARPA</li>
5257 <li>28.172.IN-ADDR.ARPA</li>
5258 <li>29.172.IN-ADDR.ARPA</li>
5259 <li>30.172.IN-ADDR.ARPA</li>
5260 <li>31.172.IN-ADDR.ARPA</li>
5261 <li>168.192.IN-ADDR.ARPA</li>
5262 <li>0.IN-ADDR.ARPA</li>
5263 <li>127.IN-ADDR.ARPA</li>
5264 <li>254.169.IN-ADDR.ARPA</li>
5265 <li>2.0.192.IN-ADDR.ARPA</li>
5266 <li>100.51.198.IN-ADDR.ARPA</li>
5267 <li>113.0.203.IN-ADDR.ARPA</li>
5268 <li>255.255.255.255.IN-ADDR.ARPA</li>
5269 <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>
5270 <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>
5271 <li>8.B.D.0.1.0.0.2.IP6.ARPA</li>
5272 <li>D.F.IP6.ARPA</li>
5273 <li>8.E.F.IP6.ARPA</li>
5274 <li>9.E.F.IP6.ARPA</li>
5275 <li>A.E.F.IP6.ARPA</li>
5276 <li>B.E.F.IP6.ARPA</li>
5277 </ul></div>
5278 <p>
5279           </p>
5280 <p>
5281             Empty zones are settable at the view level and only apply to
5282             views of class IN.  Disabled empty zones are only inherited
5283             from options if there are no disabled empty zones specified
5284             at the view level.  To override the options list of disabled
5285             zones, you can disable the root zone at the view level, for example:
5286 </p>
5287 <pre class="programlisting">
5288             disable-empty-zone ".";
5289 </pre>
5290 <p>
5291           </p>
5292 <p>
5293             If you are using the address ranges covered here, you should
5294             already have reverse zones covering the addresses you use.
5295             In practice this appears to not be the case with many queries
5296             being made to the infrastructure servers for names in these
5297             spaces.  So many in fact that sacrificial servers were needed
5298             to be deployed to channel the query load away from the
5299             infrastructure servers.
5300           </p>
5301 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
5302 <h3 class="title">Note</h3>
5303             The real parent servers for these zones should disable all
5304             empty zone under the parent zone they serve.  For the real
5305             root servers, this is all built-in empty zones.  This will
5306             enable them to return referrals to deeper in the tree.
5307           </div>
5308 <div class="variablelist"><dl>
5309 <dt><span class="term"><span><strong class="command">empty-server</strong></span></span></dt>
5310 <dd><p>
5311                   Specify what server name will appear in the returned
5312                   SOA record for empty zones.  If none is specified, then
5313                   the zone's name will be used.
5314                 </p></dd>
5315 <dt><span class="term"><span><strong class="command">empty-contact</strong></span></span></dt>
5316 <dd><p>
5317                   Specify what contact name will appear in the returned
5318                   SOA record for empty zones.  If none is specified, then
5319                   "." will be used.
5320                 </p></dd>
5321 <dt><span class="term"><span><strong class="command">empty-zones-enable</strong></span></span></dt>
5322 <dd><p>
5323                   Enable or disable all empty zones.  By default, they
5324                   are enabled.
5325                 </p></dd>
5326 <dt><span class="term"><span><strong class="command">disable-empty-zone</strong></span></span></dt>
5327 <dd><p>
5328                   Disable individual empty zones.  By default, none are
5329                   disabled.  This option can be specified multiple times.
5330                 </p></dd>
5331 </dl></div>
5332 </div>
5333 <div class="sect3" lang="en">
5334 <div class="titlepage"><div><div><h4 class="title">
5335 <a name="acache"></a>Additional Section Caching</h4></div></div></div>
5336 <p>
5337             The additional section cache, also called <span><strong class="command">acache</strong></span>,
5338             is an internal cache to improve the response performance of BIND 9.
5339             When additional section caching is enabled, BIND 9 will
5340             cache an internal short-cut to the additional section content for
5341             each answer RR.
5342             Note that <span><strong class="command">acache</strong></span> is an internal caching
5343             mechanism of BIND 9, and is not related to the DNS caching
5344             server function.
5345           </p>
5346 <p>
5347             Additional section caching does not change the
5348             response content (except the RRsets ordering of the additional
5349             section, see below), but can improve the response performance
5350             significantly.
5351             It is particularly effective when BIND 9 acts as an authoritative
5352             server for a zone that has many delegations with many glue RRs.
5353           </p>
5354 <p>
5355             In order to obtain the maximum performance improvement
5356             from additional section caching, setting
5357             <span><strong class="command">additional-from-cache</strong></span>
5358             to <span><strong class="command">no</strong></span> is recommended, since the current
5359             implementation of <span><strong class="command">acache</strong></span>
5360             does not short-cut of additional section information from the
5361             DNS cache data.
5362           </p>
5363 <p>
5364             One obvious disadvantage of <span><strong class="command">acache</strong></span> is
5365             that it requires much more
5366             memory for the internal cached data.
5367             Thus, if the response performance does not matter and memory
5368             consumption is much more critical, the
5369             <span><strong class="command">acache</strong></span> mechanism can be
5370             disabled by setting <span><strong class="command">acache-enable</strong></span> to
5371             <span><strong class="command">no</strong></span>.
5372             It is also possible to specify the upper limit of memory
5373             consumption
5374             for acache by using <span><strong class="command">max-acache-size</strong></span>.
5375           </p>
5376 <p>
5377             Additional section caching also has a minor effect on the
5378             RRset ordering in the additional section.
5379             Without <span><strong class="command">acache</strong></span>,
5380             <span><strong class="command">cyclic</strong></span> order is effective for the additional
5381             section as well as the answer and authority sections.
5382             However, additional section caching fixes the ordering when it
5383             first caches an RRset for the additional section, and the same
5384             ordering will be kept in succeeding responses, regardless of the
5385             setting of <span><strong class="command">rrset-order</strong></span>.
5386             The effect of this should be minor, however, since an
5387             RRset in the additional section
5388             typically only contains a small number of RRs (and in many cases
5389             it only contains a single RR), in which case the
5390             ordering does not matter much.
5391           </p>
5392 <p>
5393             The following is a summary of options related to
5394             <span><strong class="command">acache</strong></span>.
5395           </p>
5396 <div class="variablelist"><dl>
5397 <dt><span class="term"><span><strong class="command">acache-enable</strong></span></span></dt>
5398 <dd><p>
5399                   If <span><strong class="command">yes</strong></span>, additional section caching is
5400                   enabled.  The default value is <span><strong class="command">no</strong></span>.
5401                 </p></dd>
5402 <dt><span class="term"><span><strong class="command">acache-cleaning-interval</strong></span></span></dt>
5403 <dd><p>
5404                   The server will remove stale cache entries, based on an LRU
5405                   based
5406                   algorithm, every <span><strong class="command">acache-cleaning-interval</strong></span> minutes.
5407                   The default is 60 minutes.
5408                   If set to 0, no periodic cleaning will occur.
5409                 </p></dd>
5410 <dt><span class="term"><span><strong class="command">max-acache-size</strong></span></span></dt>
5411 <dd><p>
5412                   The maximum amount of memory in bytes to use for the server's acache.
5413                   When the amount of data in the acache reaches this limit,
5414                   the server
5415                   will clean more aggressively so that the limit is not
5416                   exceeded.
5417                   In a server with multiple views, the limit applies
5418                   separately to the
5419                   acache of each view.
5420                   The default is <code class="literal">16M</code>.
5421                 </p></dd>
5422 </dl></div>
5423 </div>
5424 <div class="sect3" lang="en">
5425 <div class="titlepage"><div><div><h4 class="title">
5426 <a name="id2588188"></a>Content Filtering</h4></div></div></div>
5427 <p>
5428             <acronym class="acronym">BIND</acronym> 9 provides the ability to filter
5429             out DNS responses from external DNS servers containing
5430             certain types of data in the answer section.
5431             Specifically, it can reject address (A or AAAA) records if
5432             the corresponding IPv4 or IPv6 addresses match the given
5433             <code class="varname">address_match_list</code> of the
5434             <span><strong class="command">deny-answer-addresses</strong></span> option.
5435             It can also reject CNAME or DNAME records if the "alias"
5436             name (i.e., the CNAME alias or the substituted query name
5437             due to DNAME) matches the
5438             given <code class="varname">namelist</code> of the
5439             <span><strong class="command">deny-answer-aliases</strong></span> option, where
5440             "match" means the alias name is a subdomain of one of
5441             the <code class="varname">name_list</code> elements.
5442             If the optional <code class="varname">namelist</code> is specified
5443             with <span><strong class="command">except-from</strong></span>, records whose query name
5444             matches the list will be accepted regardless of the filter
5445             setting.
5446             Likewise, if the alias name is a subdomain of the
5447             corresponding zone, the <span><strong class="command">deny-answer-aliases</strong></span>
5448             filter will not apply;
5449             for example, even if "example.com" is specified for
5450             <span><strong class="command">deny-answer-aliases</strong></span>,
5451           </p>
5452 <pre class="programlisting">www.example.com. CNAME xxx.example.com.</pre>
5453 <p>
5454             returned by an "example.com" server will be accepted.
5455           </p>
5456 <p>
5457             In the <code class="varname">address_match_list</code> of the
5458             <span><strong class="command">deny-answer-addresses</strong></span> option, only
5459             <code class="varname">ip_addr</code>
5460             and <code class="varname">ip_prefix</code>
5461             are meaningful;
5462             any <code class="varname">key_id</code> will be silently ignored.
5463           </p>
5464 <p>
5465             If a response message is rejected due to the filtering,
5466             the entire message is discarded without being cached, and
5467             a SERVFAIL error will be returned to the client.
5468           </p>
5469 <p>
5470             This filtering is intended to prevent "DNS rebinding attacks," in
5471             which an attacker, in response to a query for a domain name the
5472             attacker controls, returns an IP address within your own network or
5473             an alias name within your own domain.
5474             A naive web browser or script could then serve as an
5475             unintended proxy, allowing the attacker
5476             to get access to an internal node of your local network
5477             that couldn't be externally accessed otherwise.
5478             See the paper available at
5479             <a href="" target="_top">
5480             http://portal.acm.org/citation.cfm?id=1315245.1315298
5481             </a>
5482             for more details about the attacks.
5483           </p>
5484 <p>
5485             For example, if you own a domain named "example.net" and
5486             your internal network uses an IPv4 prefix 192.0.2.0/24,
5487             you might specify the following rules:
5488           </p>
5489 <pre class="programlisting">deny-answer-addresses { 192.0.2.0/24; } except-from { "example.net"; };
5490 deny-answer-aliases { "example.net"; };
5491 </pre>
5492 <p>
5493             If an external attacker lets a web browser in your local
5494             network look up an IPv4 address of "attacker.example.com",
5495             the attacker's DNS server would return a response like this:
5496           </p>
5497 <pre class="programlisting">attacker.example.com. A 192.0.2.1</pre>
5498 <p>
5499             in the answer section.
5500             Since the rdata of this record (the IPv4 address) matches
5501             the specified prefix 192.0.2.0/24, this response will be
5502             ignored.
5503           </p>
5504 <p>
5505             On the other hand, if the browser looks up a legitimate
5506             internal web server "www.example.net" and the
5507             following response is returned to
5508             the <acronym class="acronym">BIND</acronym> 9 server
5509           </p>
5510 <pre class="programlisting">www.example.net. A 192.0.2.2</pre>
5511 <p>
5512             it will be accepted since the owner name "www.example.net"
5513             matches the <span><strong class="command">except-from</strong></span> element,
5514             "example.net".
5515           </p>
5516 <p>
5517             Note that this is not really an attack on the DNS per se.
5518             In fact, there is nothing wrong for an "external" name to
5519             be mapped to your "internal" IP address or domain name
5520             from the DNS point of view.
5521             It might actually be provided for a legitimate purpose,
5522             such as for debugging.
5523             As long as the mapping is provided by the correct owner,
5524             it is not possible or does not make sense to detect
5525             whether the intent of the mapping is legitimate or not
5526             within the DNS.
5527             The "rebinding" attack must primarily be protected at the
5528             application that uses the DNS.
5529             For a large site, however, it may be difficult to protect
5530             all possible applications at once.
5531             This filtering feature is provided only to help such an
5532             operational environment;
5533             it is generally discouraged to turn it on unless you are
5534             very sure you have no other choice and the attack is a
5535             real threat for your applications.
5536           </p>
5537 <p>
5538             Care should be particularly taken if you want to use this
5539             option for addresses within 127.0.0.0/8.
5540             These addresses are obviously "internal", but many
5541             applications conventionally rely on a DNS mapping from
5542             some name to such an address.
5543             Filtering out DNS records containing this address
5544             spuriously can break such applications.
5545           </p>
5546 </div>
5547 <div class="sect3" lang="en">
5548 <div class="titlepage"><div><div><h4 class="title">
5549 <a name="id2588379"></a>Response Policy Zone (RPZ) Rewriting</h4></div></div></div>
5550 <p>
5551             <acronym class="acronym">BIND</acronym> 9 includes an intentionally limited
5552             mechanism to modify DNS responses for recursive requests
5553             somewhat similar to email anti-spam DNS blacklists.
5554             Responses can be changed to deny the existence of domains(NXDOMAIN),
5555             deny the existence of IP addresses for domains (NODATA),
5556             or contain other IP addresses or data.
5557           </p>
5558 <p>
5559             The actions encoded in a response policy zone (RPZ) are applied
5560             only to queries that ask for recursion (RD=1).
5561             Response policy zones are named in the
5562             <span><strong class="command">response-policy</strong></span> option for the view or among the
5563             global options if there is no response-policy option for the view.
5564             RPZs are ordinary DNS zones containing RRsets
5565             that can be queried normally if allowed.
5566             It is usually best to restrict those queries with something like
5567             <span><strong class="command">allow-query { localhost; };</strong></span>.
5568           </p>
5569 <p>
5570             There are four kinds of RPZ records, QNAME, IP, NSIP,
5571             and NSDNAME.
5572             QNAME records are applied to query names of requests and targets
5573             of CNAME records resolved to generate the response.
5574             The owner name of a QNAME RPZ record is the query name relativized
5575             to the RPZ.
5576           </p>
5577 <p>
5578             The second kind of RPZ record, an IP policy record,
5579             is triggered by addresses in A and AAAA records
5580             for the ANSWER sections of responses.
5581             IP policy records have owner names that are
5582             subdomains of <strong class="userinput"><code>rpz-ip</code></strong> relativized to the
5583             RPZ origin name and encode an IP address or address block.
5584             IPv4 addresses are encoded as
5585             <strong class="userinput"><code>prefixlength.B4.B3.B2.B1.rpz-ip</code></strong>.
5586             The prefix length must be between 1 and 32.
5587             All four bytes, B4, B3, B2, and B1, must be present.
5588             B4 is the decimal value of the least significant byte of the
5589             IPv4 address as in IN-ADDR.ARPA.
5590             IPv6 addresses are encoded in a format similar to the standard
5591             IPv6 text representation,
5592             <strong class="userinput"><code>prefixlength.W8.W7.W6.W5.W4.W3.W2.W1.rpz-ip</code></strong>.
5593             Each of W8,...,W1 is a one to four digit hexadecimal number
5594             representing 16 bits of the IPv6 address as in the standard text
5595             representation of IPv6 addresses, but reversed as in IN-ADDR.ARPA.
5596             All 8 words must be present except when consecutive
5597             zero words are replaced with <strong class="userinput"><code>.zz.</code></strong>
5598             analogous to double colons (::) in standard IPv6 text encodings.
5599             The prefix length must be between 1 and 128.
5600           </p>
5601 <p>
5602             NSDNAME policy records match names of authoritative servers
5603             for the query name, a parent of the query name, a CNAME,
5604             or a parent of a CNAME.
5605             They are encoded as subdomains of
5606             <strong class="userinput"><code>rpz-nsdomain</code></strong> relativized
5607             to the RPZ origin name.
5608           </p>
5609 <p>
5610             NSIP policy records match IP addresses in A and AAAA RRsets
5611             for domains that can be checked against NSDNAME policy records.
5612             The are encoded like IP policies except as subdomains of
5613             <strong class="userinput"><code>rpz-nsip</code></strong>.
5614           </p>
5615 <p>
5616             The query response is checked against all RPZs, so
5617             two or more policy records can apply to a single response.
5618             Because DNS responses can be rewritten according by at most a
5619             single policy record, a single policy (other than
5620             <span><strong class="command">DISABLED</strong></span> policies) must be chosen.
5621             Policies are chosen in the following order:
5622             </p>
5623 <div class="itemizedlist"><ul type="disc">
5624 <li>Among applicable zones, use the RPZ that appears first
5625                 in the response-policy option.
5626               </li>
5627 <li>Prefer QNAME to IP to NSDNAME to NSIP policy records
5628                 in a single RPZ
5629               </li>
5630 <li>Among applicable NSDNAME policy records, prefer the
5631                 policy record that matches the lexically smallest name
5632               </li>
5633 <li>Among IP or NSIP policy records, prefer the record
5634                 with the longest prefix.
5635               </li>
5636 <li>Among records with the same prefex length,
5637                 prefer the IP or NSIP policy record that matches
5638                 the smallest IP address.
5639               </li>
5640 </ul></div>
5641 <p>
5642           </p>
5643 <p>
5644             When the processing of a response is restarted to resolve
5645             DNAME or CNAME records and an applicable policy record set has
5646             not been found,
5647             all RPZs are again consulted for the DNAME or CNAME names
5648             and addresses.
5649           </p>
5650 <p>
5651             Authority verification issues and variations in authority data
5652             can cause inconsistent results for NSIP and NSDNAME policy records.
5653             Glue NS records often differ from authoritative NS records.
5654             So they are available
5655             only when <acronym class="acronym">BIND</acronym> is built with the
5656             <strong class="userinput"><code>--enable-rpz-nsip</code></strong> or
5657             <strong class="userinput"><code>--enable-rpz-nsdname</code></strong> options
5658             on the "configure" command line.
5659           </p>
5660 <p>
5661             RPZ record sets are special CNAME records or one or more
5662             of any types of DNS record except DNAME or DNSSEC.
5663             Except when a policy record is a CNAME, there can be more
5664             more than one record and more than one type
5665             in a set of policy records.
5666             Except for three kinds of CNAME records that are illegal except
5667             in policy zones, the records in a set are used in the response as if
5668             their owner name were the query name.  They are copied to the
5669             response as dictated by their types.
5670             </p>
5671 <div class="itemizedlist"><ul type="disc">
5672 <li>A CNAME whose target is the root domain (.)
5673                 specifies the <span><strong class="command">NXDOMAIN</strong></span> policy,
5674                 which generates an NXDOMAIN response.
5675               </li>
5676 <li>A CNAME whose target is the wildcard top-level
5677                 domain (*.) specifies the <span><strong class="command">NODATA</strong></span> policy,
5678                 which rewrites the response to NODATA or ANCOUNT=1.
5679               </li>
5680 <li>A CNAME whose target is a wildcard hostname such
5681                 as *.example.com is used normally after the astrisk (*)
5682                 has been replaced with the query name.
5683                 These records are usually resolved with ordinary CNAMEs
5684                 outside the policy zones.  They can be useful for logging.
5685               </li>
5686 <li>The <span><strong class="command">PASSTHRU</strong></span> policy is specified
5687                 by a CNAME whose target is the variable part of its own
5688                 owner name.  It causes the response to not be rewritten
5689                 and is most often used to "poke holes" in policies for
5690                 CIDR blocks.
5691               </li>
5692 </ul></div>
5693 <p>
5694           </p>
5695 <p>
5696             The policies specified in individual records
5697             in an RPZ can be overridden with a <span><strong class="command">policy</strong></span> clause
5698             in the <span><strong class="command">response-policy</strong></span> option.
5699             An organization using an RPZ provided by another organization might
5700             use this mechanism to redirect domains to its own walled garden.
5701             </p>
5702 <div class="itemizedlist"><ul type="disc">
5703 <li>
5704 <span><strong class="command">GIVEN</strong></span> says "do not override."
5705               </li>
5706 <li>
5707 <span><strong class="command">DISABLED</strong></span> causes policy records to do
5708                 nothing but log what they might have done.
5709                 The response to the DNS query will be written according to
5710                 any matching policy records that are not disabled.
5711                 Policy zones overridden with <span><strong class="command">DISABLED</strong></span> should
5712                 appear first, because they will often not be logged
5713                 if a higher precedence policy is found first.
5714               </li>
5715 <li>
5716 <span><strong class="command">PASSTHRU</strong></span> causes all policy records
5717                 to act as if they were CNAME records with targets the variable
5718                 part of their owner name.  They protect the response from
5719                 being changed.
5720               </li>
5721 <li>
5722 <span><strong class="command">NXDOMAIN</strong></span> causes all RPZ records
5723                 to specify NXDOMAIN policies.
5724               </li>
5725 <li>
5726 <span><strong class="command">NODATA</strong></span> overrides with the
5727                 NODATA policy
5728               </li>
5729 <li>
5730 <span><strong class="command">CNAME domain</strong></span> causes all RPZ
5731                 policy records to act as if they were "cname domain" records.
5732               </li>
5733 </ul></div>
5734 <p>
5735           </p>
5736 <p>
5737             For example, you might use this option statement
5738           </p>
5739 <pre class="programlisting">    response-policy { zone "badlist"; };</pre>
5740 <p>
5741             and this zone statement
5742           </p>
5743 <pre class="programlisting">    zone "badlist" {type master; file "master/badlist"; allow-query {none;}; };</pre>
5744 <p>
5745             with this zone file
5746           </p>
5747 <pre class="programlisting">$TTL 1H
5748 @                       SOA LOCALHOST. named-mgr.example.com (1 1h 15m 30d 2h)
5749                         NS  LOCALHOST.
5750
5751 ; QNAME policy records.  There are no periods (.) after the owner names.
5752 nxdomain.domain.com     CNAME   .               ; NXDOMAIN policy
5753 nodata.domain.com       CNAME   *.              ; NODATA policy
5754 bad.domain.com          A       10.0.0.1        ; redirect to a walled garden
5755                         AAAA    2001:2::1
5756
5757 ; do not rewrite (PASSTHRU) OK.DOMAIN.COM
5758 ok.domain.com           CNAME   ok.domain.com.
5759
5760 bzone.domain.com        CNAME   garden.example.com.
5761
5762 ; redirect x.bzone.domain.com to x.bzone.domain.com.garden.example.com
5763 *.bzone.domain.com      CNAME   *.garden.example.com.
5764
5765
5766 ; IP policy records that rewrite all answers for 127/8 except 127.0.0.1
5767 8.0.0.0.127.rpz-ip      CNAME   .
5768 32.1.0.0.127.rpz-ip     CNAME   32.1.0.0.127.   ; PASSTHRU for 127.0.0.1
5769
5770 ; NSDNAME and NSIP policy records
5771 ns.domain.com.rpz-nsdname   CNAME   .
5772 48.zz.2.2001.rpz-nsip       CNAME   .
5773 </pre>
5774 </div>
5775 </div>
5776 <div class="sect2" lang="en">
5777 <div class="titlepage"><div><div><h3 class="title">
5778 <a name="server_statement_grammar"></a><span><strong class="command">server</strong></span> Statement Grammar</h3></div></div></div>
5779 <pre class="programlisting"><span><strong class="command">server</strong></span> <em class="replaceable"><code>ip_addr[/prefixlen]</code></em> {
5780     [<span class="optional"> bogus <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5781     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5782     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5783     [<span class="optional"> edns <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5784     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
5785     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
5786     [<span class="optional"> transfers <em class="replaceable"><code>number</code></em> ; </span>]
5787     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em> ; ]</span>]
5788     [<span class="optional"> keys <em class="replaceable"><code>{ string ; [<span class="optional"> string ; [<span class="optional">...</span>]</span>] }</code></em> ; </span>]
5789     [<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>]
5790     [<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>]
5791     [<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>]
5792     [<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>]
5793     [<span class="optional"> query-source [<span class="optional"> address ( <em class="replaceable"><code>ip_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
5794                   [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]; </span>]
5795     [<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>]
5796                      [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]; </span>]
5797     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5798     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
5799     [<span class="optional"> queryport-pool-updateinterval <em class="replaceable"><code>number</code></em>; </span>]
5800 };
5801 </pre>
5802 </div>
5803 <div class="sect2" lang="en">
5804 <div class="titlepage"><div><div><h3 class="title">
5805 <a name="server_statement_definition_and_usage"></a><span><strong class="command">server</strong></span> Statement Definition and
5806             Usage</h3></div></div></div>
5807 <p>
5808             The <span><strong class="command">server</strong></span> statement defines
5809             characteristics
5810             to be associated with a remote name server.  If a prefix length is
5811             specified, then a range of servers is covered.  Only the most
5812             specific
5813             server clause applies regardless of the order in
5814             <code class="filename">named.conf</code>.
5815           </p>
5816 <p>
5817             The <span><strong class="command">server</strong></span> statement can occur at
5818             the top level of the
5819             configuration file or inside a <span><strong class="command">view</strong></span>
5820             statement.
5821             If a <span><strong class="command">view</strong></span> statement contains
5822             one or more <span><strong class="command">server</strong></span> statements, only
5823             those
5824             apply to the view and any top-level ones are ignored.
5825             If a view contains no <span><strong class="command">server</strong></span>
5826             statements,
5827             any top-level <span><strong class="command">server</strong></span> statements are
5828             used as
5829             defaults.
5830           </p>
5831 <p>
5832             If you discover that a remote server is giving out bad data,
5833             marking it as bogus will prevent further queries to it. The
5834             default
5835             value of <span><strong class="command">bogus</strong></span> is <span><strong class="command">no</strong></span>.
5836           </p>
5837 <p>
5838             The <span><strong class="command">provide-ixfr</strong></span> clause determines
5839             whether
5840             the local server, acting as master, will respond with an
5841             incremental
5842             zone transfer when the given remote server, a slave, requests it.
5843             If set to <span><strong class="command">yes</strong></span>, incremental transfer
5844             will be provided
5845             whenever possible. If set to <span><strong class="command">no</strong></span>,
5846             all transfers
5847             to the remote server will be non-incremental. If not set, the
5848             value
5849             of the <span><strong class="command">provide-ixfr</strong></span> option in the
5850             view or
5851             global options block is used as a default.
5852           </p>
5853 <p>
5854             The <span><strong class="command">request-ixfr</strong></span> clause determines
5855             whether
5856             the local server, acting as a slave, will request incremental zone
5857             transfers from the given remote server, a master. If not set, the
5858             value of the <span><strong class="command">request-ixfr</strong></span> option in
5859             the view or
5860             global options block is used as a default.
5861           </p>
5862 <p>
5863             IXFR requests to servers that do not support IXFR will
5864             automatically
5865             fall back to AXFR.  Therefore, there is no need to manually list
5866             which servers support IXFR and which ones do not; the global
5867             default
5868             of <span><strong class="command">yes</strong></span> should always work.
5869             The purpose of the <span><strong class="command">provide-ixfr</strong></span> and
5870             <span><strong class="command">request-ixfr</strong></span> clauses is
5871             to make it possible to disable the use of IXFR even when both
5872             master
5873             and slave claim to support it, for example if one of the servers
5874             is buggy and crashes or corrupts data when IXFR is used.
5875           </p>
5876 <p>
5877             The <span><strong class="command">edns</strong></span> clause determines whether
5878             the local server will attempt to use EDNS when communicating
5879             with the remote server.  The default is <span><strong class="command">yes</strong></span>.
5880           </p>
5881 <p>
5882             The <span><strong class="command">edns-udp-size</strong></span> option sets the EDNS UDP size
5883             that is advertised by <span><strong class="command">named</strong></span> when querying the remote server.
5884             Valid values are 512 to 4096 bytes (values outside this range will be
5885             silently adjusted).  This option is useful when you wish to
5886             advertises a different value to this server than the value you
5887             advertise globally, for example, when there is a firewall at the
5888             remote site that is blocking large replies.
5889           </p>
5890 <p>
5891             The <span><strong class="command">max-udp-size</strong></span> option sets the
5892             maximum EDNS UDP message size <span><strong class="command">named</strong></span> will send.  Valid
5893             values are 512 to 4096 bytes (values outside this range will
5894             be silently adjusted).  This option is useful when you
5895             know that there is a firewall that is blocking large
5896             replies from <span><strong class="command">named</strong></span>.
5897           </p>
5898 <p>
5899             The server supports two zone transfer methods. The first, <span><strong class="command">one-answer</strong></span>,
5900             uses one DNS message per resource record transferred. <span><strong class="command">many-answers</strong></span> packs
5901             as many resource records as possible into a message. <span><strong class="command">many-answers</strong></span> is
5902             more efficient, but is only known to be understood by <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
5903             8.x, and patched versions of <acronym class="acronym">BIND</acronym>
5904             4.9.5. You can specify which method
5905             to use for a server with the <span><strong class="command">transfer-format</strong></span> option.
5906             If <span><strong class="command">transfer-format</strong></span> is not
5907             specified, the <span><strong class="command">transfer-format</strong></span>
5908             specified
5909             by the <span><strong class="command">options</strong></span> statement will be
5910             used.
5911           </p>
5912 <p><span><strong class="command">transfers</strong></span>
5913             is used to limit the number of concurrent inbound zone
5914             transfers from the specified server. If no
5915             <span><strong class="command">transfers</strong></span> clause is specified, the
5916             limit is set according to the
5917             <span><strong class="command">transfers-per-ns</strong></span> option.
5918           </p>
5919 <p>
5920             The <span><strong class="command">keys</strong></span> clause identifies a
5921             <span><strong class="command">key_id</strong></span> defined by the <span><strong class="command">key</strong></span> statement,
5922             to be used for transaction security (TSIG, <a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
5923             when talking to the remote server.
5924             When a request is sent to the remote server, a request signature
5925             will be generated using the key specified here and appended to the
5926             message. A request originating from the remote server is not
5927             required
5928             to be signed by this key.
5929           </p>
5930 <p>
5931             Although the grammar of the <span><strong class="command">keys</strong></span>
5932             clause
5933             allows for multiple keys, only a single key per server is
5934             currently
5935             supported.
5936           </p>
5937 <p>
5938             The <span><strong class="command">transfer-source</strong></span> and
5939             <span><strong class="command">transfer-source-v6</strong></span> clauses specify
5940             the IPv4 and IPv6 source
5941             address to be used for zone transfer with the remote server,
5942             respectively.
5943             For an IPv4 remote server, only <span><strong class="command">transfer-source</strong></span> can
5944             be specified.
5945             Similarly, for an IPv6 remote server, only
5946             <span><strong class="command">transfer-source-v6</strong></span> can be
5947             specified.
5948             For more details, see the description of
5949             <span><strong class="command">transfer-source</strong></span> and
5950             <span><strong class="command">transfer-source-v6</strong></span> in
5951             <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
5952           </p>
5953 <p>
5954             The <span><strong class="command">notify-source</strong></span> and
5955             <span><strong class="command">notify-source-v6</strong></span> clauses specify the
5956             IPv4 and IPv6 source address to be used for notify
5957             messages sent to remote servers, respectively.  For an
5958             IPv4 remote server, only <span><strong class="command">notify-source</strong></span>
5959             can be specified.  Similarly, for an IPv6 remote server,
5960             only <span><strong class="command">notify-source-v6</strong></span> can be specified.
5961           </p>
5962 <p>
5963             The <span><strong class="command">query-source</strong></span> and
5964             <span><strong class="command">query-source-v6</strong></span> clauses specify the
5965             IPv4 and IPv6 source address to be used for queries
5966             sent to remote servers, respectively.  For an IPv4
5967             remote server, only <span><strong class="command">query-source</strong></span> can
5968             be specified.  Similarly, for an IPv6 remote server,
5969             only <span><strong class="command">query-source-v6</strong></span> can be specified.
5970           </p>
5971 </div>
5972 <div class="sect2" lang="en">
5973 <div class="titlepage"><div><div><h3 class="title">
5974 <a name="statschannels"></a><span><strong class="command">statistics-channels</strong></span> Statement Grammar</h3></div></div></div>
5975 <pre class="programlisting"><span><strong class="command">statistics-channels</strong></span> {
5976    [ inet ( ip_addr | * ) [ port ip_port ]
5977    [ allow { <em class="replaceable"><code> address_match_list </code></em> } ]; ]
5978    [ inet ...; ]
5979 };
5980 </pre>
5981 </div>
5982 <div class="sect2" lang="en">
5983 <div class="titlepage"><div><div><h3 class="title">
5984 <a name="id2589481"></a><span><strong class="command">statistics-channels</strong></span> Statement Definition and
5985             Usage</h3></div></div></div>
5986 <p>
5987           The <span><strong class="command">statistics-channels</strong></span> statement
5988           declares communication channels to be used by system
5989           administrators to get access to statistics information of
5990           the name server.
5991         </p>
5992 <p>
5993           This statement intends to be flexible to support multiple
5994           communication protocols in the future, but currently only
5995           HTTP access is supported.
5996           It requires that BIND 9 be compiled with libxml2;
5997           the <span><strong class="command">statistics-channels</strong></span> statement is
5998           still accepted even if it is built without the library,
5999           but any HTTP access will fail with an error.
6000         </p>
6001 <p>
6002           An <span><strong class="command">inet</strong></span> control channel is a TCP socket
6003           listening at the specified <span><strong class="command">ip_port</strong></span> on the
6004           specified <span><strong class="command">ip_addr</strong></span>, which can be an IPv4 or IPv6
6005           address.  An <span><strong class="command">ip_addr</strong></span> of <code class="literal">*</code> (asterisk) is
6006           interpreted as the IPv4 wildcard address; connections will be
6007           accepted on any of the system's IPv4 addresses.
6008           To listen on the IPv6 wildcard address,
6009           use an <span><strong class="command">ip_addr</strong></span> of <code class="literal">::</code>.
6010         </p>
6011 <p>
6012           If no port is specified, port 80 is used for HTTP channels.
6013           The asterisk "<code class="literal">*</code>" cannot be used for
6014           <span><strong class="command">ip_port</strong></span>.
6015         </p>
6016 <p>
6017           The attempt of opening a statistics channel is
6018           restricted by the optional <span><strong class="command">allow</strong></span> clause.
6019           Connections to the statistics channel are permitted based on the
6020           <span><strong class="command">address_match_list</strong></span>.
6021           If no <span><strong class="command">allow</strong></span> clause is present,
6022           <span><strong class="command">named</strong></span> accepts connection
6023           attempts from any address; since the statistics may
6024           contain sensitive internal information, it is highly
6025           recommended to restrict the source of connection requests
6026           appropriately.
6027         </p>
6028 <p>
6029           If no <span><strong class="command">statistics-channels</strong></span> statement is present,
6030           <span><strong class="command">named</strong></span> will not open any communication channels.
6031         </p>
6032 </div>
6033 <div class="sect2" lang="en">
6034 <div class="titlepage"><div><div><h3 class="title">
6035 <a name="trusted-keys"></a><span><strong class="command">trusted-keys</strong></span> Statement Grammar</h3></div></div></div>
6036 <pre class="programlisting"><span><strong class="command">trusted-keys</strong></span> {
6037     <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> ;
6038     [<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>]
6039 };
6040 </pre>
6041 </div>
6042 <div class="sect2" lang="en">
6043 <div class="titlepage"><div><div><h3 class="title">
6044 <a name="id2589689"></a><span><strong class="command">trusted-keys</strong></span> Statement Definition
6045             and Usage</h3></div></div></div>
6046 <p>
6047             The <span><strong class="command">trusted-keys</strong></span> statement defines
6048             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
6049             public key for a non-authoritative zone is known, but
6050             cannot be securely obtained through DNS, either because
6051             it is the DNS root zone or because its parent zone is
6052             unsigned.  Once a key has been configured as a trusted
6053             key, it is treated as if it had been validated and
6054             proven secure. The resolver attempts DNSSEC validation
6055             on all DNS data in subdomains of a security root.
6056           </p>
6057 <p>
6058             All keys (and corresponding zones) listed in
6059             <span><strong class="command">trusted-keys</strong></span> are deemed to exist regardless
6060             of what parent zones say.  Similarly for all keys listed in
6061             <span><strong class="command">trusted-keys</strong></span> only those keys are
6062             used to validate the DNSKEY RRset.  The parent's DS RRset
6063             will not be used.
6064           </p>
6065 <p>
6066             The <span><strong class="command">trusted-keys</strong></span> statement can contain
6067             multiple key entries, each consisting of the key's
6068             domain name, flags, protocol, algorithm, and the Base-64
6069             representation of the key data.
6070             Spaces, tabs, newlines and carriage returns are ignored
6071             in the key data, so the configuration may be split up into
6072             multiple lines.
6073           </p>
6074 <p>
6075             <span><strong class="command">trusted-keys</strong></span> may be set at the top level
6076             of <code class="filename">named.conf</code> or within a view.  If it is
6077             set in both places, they are additive: keys defined at the top
6078             level are inherited by all views, but keys defined in a view
6079             are only used within that view.
6080           </p>
6081 </div>
6082 <div class="sect2" lang="en">
6083 <div class="titlepage"><div><div><h3 class="title">
6084 <a name="id2589736"></a><span><strong class="command">managed-keys</strong></span> Statement Grammar</h3></div></div></div>
6085 <pre class="programlisting"><span><strong class="command">managed-keys</strong></span> {
6086     <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> ;
6087     [<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>]
6088 };
6089 </pre>
6090 </div>
6091 <div class="sect2" lang="en">
6092 <div class="titlepage"><div><div><h3 class="title">
6093 <a name="managed-keys"></a><span><strong class="command">managed-keys</strong></span> Statement Definition
6094             and Usage</h3></div></div></div>
6095 <p>
6096             The <span><strong class="command">managed-keys</strong></span> statement, like
6097             <span><strong class="command">trusted-keys</strong></span>, defines DNSSEC
6098             security roots.  The difference is that
6099             <span><strong class="command">managed-keys</strong></span> can be kept up to date
6100             automatically, without intervention from the resolver
6101             operator.
6102           </p>
6103 <p>
6104             Suppose, for example, that a zone's key-signing
6105             key was compromised, and the zone owner had to revoke and
6106             replace the key.  A resolver which had the old key in a
6107             <span><strong class="command">trusted-keys</strong></span> statement would be
6108             unable to validate this zone any longer; it would
6109             reply with a SERVFAIL response code.  This would
6110             continue until the resolver operator had updated the
6111             <span><strong class="command">trusted-keys</strong></span> statement with the new key.
6112           </p>
6113 <p>
6114             If, however, the zone were listed in a
6115             <span><strong class="command">managed-keys</strong></span> statement instead, then the
6116             zone owner could add a "stand-by" key to the zone in advance.
6117             <span><strong class="command">named</strong></span> would store the stand-by key, and
6118             when the original key was revoked, <span><strong class="command">named</strong></span>
6119             would be able to transition smoothly to the new key.  It would
6120             also recognize that the old key had been revoked, and cease
6121             using that key to validate answers, minimizing the damage that
6122             the compromised key could do.
6123           </p>
6124 <p>
6125             A <span><strong class="command">managed-keys</strong></span> statement contains a list of
6126             the keys to be managed, along with information about how the
6127             keys are to be initialized for the first time.  The only
6128             initialization method currently supported (as of
6129             <acronym class="acronym">BIND</acronym> 9.7.0) is <code class="literal">initial-key</code>.
6130             This means the <span><strong class="command">managed-keys</strong></span> statement must
6131             contain a copy of the initializing key.  (Future releases may
6132             allow keys to be initialized by other methods, eliminating this
6133             requirement.)
6134           </p>
6135 <p>
6136             Consequently, a <span><strong class="command">managed-keys</strong></span> statement
6137             appears similar to a <span><strong class="command">trusted-keys</strong></span>, differing
6138             in the presence of the second field, containing the keyword
6139             <code class="literal">initial-key</code>.  The difference is, whereas the
6140             keys listed in a <span><strong class="command">trusted-keys</strong></span> continue to be
6141             trusted until they are removed from
6142             <code class="filename">named.conf</code>, an initializing key listed
6143             in a <span><strong class="command">managed-keys</strong></span> statement is only trusted
6144             <span class="emphasis"><em>once</em></span>: for as long as it takes to load the
6145             managed key database and start the RFC 5011 key maintenance
6146             process.
6147           </p>
6148 <p>
6149             The first time <span><strong class="command">named</strong></span> runs with a managed key
6150             configured in <code class="filename">named.conf</code>, it fetches the
6151             DNSKEY RRset directly from the zone apex, and validates it
6152             using the key specified in the <span><strong class="command">managed-keys</strong></span>
6153             statement.  If the DNSKEY RRset is validly signed, then it is
6154             used as the basis for a new managed keys database.
6155           </p>
6156 <p>
6157             From that point on, whenever <span><strong class="command">named</strong></span> runs, it
6158             sees the <span><strong class="command">managed-keys</strong></span> statement, checks to
6159             make sure RFC 5011 key maintenance has already been initialized
6160             for the specified domain, and if so, it simply moves on.  The
6161             key specified in the <span><strong class="command">managed-keys</strong></span> is not
6162             used to validate answers; it has been superseded by the key or
6163             keys stored in the managed keys database.
6164           </p>
6165 <p>
6166             The next time <span><strong class="command">named</strong></span> runs after a name
6167             has been <span class="emphasis"><em>removed</em></span> from the
6168             <span><strong class="command">managed-keys</strong></span> statement, the corresponding
6169             zone will be removed from the managed keys database,
6170             and RFC 5011 key maintenance will no longer be used for that
6171             domain.
6172           </p>
6173 <p>
6174             <span><strong class="command">named</strong></span> only maintains a single managed keys
6175             database; consequently, unlike <span><strong class="command">trusted-keys</strong></span>,
6176             <span><strong class="command">managed-keys</strong></span> may only be set at the top
6177             level of <code class="filename">named.conf</code>, not within a view.
6178           </p>
6179 <p>
6180             In the current implementation, the managed keys database is
6181             stored as a master-format zone file called
6182             <code class="filename">managed-keys.bind</code>.  When the key database
6183             is changed, the zone is updated.  As with any other dynamic
6184             zone, changes will be written into a journal file,
6185             <code class="filename">managed-keys.bind.jnl</code>.  They are committed
6186             to the master file as soon as possible afterward; in the case
6187             of the managed key database, this will usually occur within 30
6188             seconds.  So, whenever <span><strong class="command">named</strong></span> is using
6189             automatic key maintenance, those two files can be expected to
6190             exist in the working directory.  (For this reason among others,
6191             the working directory should be always be writable by
6192             <span><strong class="command">named</strong></span>.)
6193           </p>
6194 <p>
6195             If the <span><strong class="command">dnssec-lookaside</strong></span> option is
6196             set to <strong class="userinput"><code>auto</code></strong>, <span><strong class="command">named</strong></span>
6197             will automatically initialize a managed key for the
6198             zone <code class="literal">dlv.isc.org</code>.  The key that is
6199             used to initialize the key maintenance process is built
6200             into <span><strong class="command">named</strong></span>, and can be overridden
6201             from <span><strong class="command">bindkeys-file</strong></span>.
6202           </p>
6203 </div>
6204 <div class="sect2" lang="en">
6205 <div class="titlepage"><div><div><h3 class="title">
6206 <a name="view_statement_grammar"></a><span><strong class="command">view</strong></span> Statement Grammar</h3></div></div></div>
6207 <pre class="programlisting"><span><strong class="command">view</strong></span> <em class="replaceable"><code>view_name</code></em>
6208       [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6209       match-clients { <em class="replaceable"><code>address_match_list</code></em> };
6210       match-destinations { <em class="replaceable"><code>address_match_list</code></em> };
6211       match-recursive-only <em class="replaceable"><code>yes_or_no</code></em> ;
6212       [<span class="optional"> <em class="replaceable"><code>view_option</code></em>; ...</span>]
6213       [<span class="optional"> <em class="replaceable"><code>zone_statement</code></em>; ...</span>]
6214 };
6215 </pre>
6216 </div>
6217 <div class="sect2" lang="en">
6218 <div class="titlepage"><div><div><h3 class="title">
6219 <a name="id2590162"></a><span><strong class="command">view</strong></span> Statement Definition and Usage</h3></div></div></div>
6220 <p>
6221             The <span><strong class="command">view</strong></span> statement is a powerful
6222             feature
6223             of <acronym class="acronym">BIND</acronym> 9 that lets a name server
6224             answer a DNS query differently
6225             depending on who is asking. It is particularly useful for
6226             implementing
6227             split DNS setups without having to run multiple servers.
6228           </p>
6229 <p>
6230             Each <span><strong class="command">view</strong></span> statement defines a view
6231             of the
6232             DNS namespace that will be seen by a subset of clients.  A client
6233             matches
6234             a view if its source IP address matches the
6235             <code class="varname">address_match_list</code> of the view's
6236             <span><strong class="command">match-clients</strong></span> clause and its
6237             destination IP address matches
6238             the <code class="varname">address_match_list</code> of the
6239             view's
6240             <span><strong class="command">match-destinations</strong></span> clause.  If not
6241             specified, both
6242             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
6243             default to matching all addresses.  In addition to checking IP
6244             addresses
6245             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
6246             can also take <span><strong class="command">keys</strong></span> which provide an
6247             mechanism for the
6248             client to select the view.  A view can also be specified
6249             as <span><strong class="command">match-recursive-only</strong></span>, which
6250             means that only recursive
6251             requests from matching clients will match that view.
6252             The order of the <span><strong class="command">view</strong></span> statements is
6253             significant &#8212;
6254             a client request will be resolved in the context of the first
6255             <span><strong class="command">view</strong></span> that it matches.
6256           </p>
6257 <p>
6258             Zones defined within a <span><strong class="command">view</strong></span>
6259             statement will
6260             only be accessible to clients that match the <span><strong class="command">view</strong></span>.
6261             By defining a zone of the same name in multiple views, different
6262             zone data can be given to different clients, for example,
6263             "internal"
6264             and "external" clients in a split DNS setup.
6265           </p>
6266 <p>
6267             Many of the options given in the <span><strong class="command">options</strong></span> statement
6268             can also be used within a <span><strong class="command">view</strong></span>
6269             statement, and then
6270             apply only when resolving queries with that view.  When no
6271             view-specific
6272             value is given, the value in the <span><strong class="command">options</strong></span> statement
6273             is used as a default.  Also, zone options can have default values
6274             specified
6275             in the <span><strong class="command">view</strong></span> statement; these
6276             view-specific defaults
6277             take precedence over those in the <span><strong class="command">options</strong></span> statement.
6278           </p>
6279 <p>
6280             Views are class specific.  If no class is given, class IN
6281             is assumed.  Note that all non-IN views must contain a hint zone,
6282             since only the IN class has compiled-in default hints.
6283           </p>
6284 <p>
6285             If there are no <span><strong class="command">view</strong></span> statements in
6286             the config
6287             file, a default view that matches any client is automatically
6288             created
6289             in class IN. Any <span><strong class="command">zone</strong></span> statements
6290             specified on
6291             the top level of the configuration file are considered to be part
6292             of
6293             this default view, and the <span><strong class="command">options</strong></span>
6294             statement will
6295             apply to the default view. If any explicit <span><strong class="command">view</strong></span>
6296             statements are present, all <span><strong class="command">zone</strong></span>
6297             statements must
6298             occur inside <span><strong class="command">view</strong></span> statements.
6299           </p>
6300 <p>
6301             Here is an example of a typical split DNS setup implemented
6302             using <span><strong class="command">view</strong></span> statements:
6303           </p>
6304 <pre class="programlisting">view "internal" {
6305       // This should match our internal networks.
6306       match-clients { 10.0.0.0/8; };
6307
6308       // Provide recursive service to internal
6309       // clients only.
6310       recursion yes;
6311
6312       // Provide a complete view of the example.com
6313       // zone including addresses of internal hosts.
6314       zone "example.com" {
6315             type master;
6316             file "example-internal.db";
6317       };
6318 };
6319
6320 view "external" {
6321       // Match all clients not matched by the
6322       // previous view.
6323       match-clients { any; };
6324
6325       // Refuse recursive service to external clients.
6326       recursion no;
6327
6328       // Provide a restricted view of the example.com
6329       // zone containing only publicly accessible hosts.
6330       zone "example.com" {
6331            type master;
6332            file "example-external.db";
6333       };
6334 };
6335 </pre>
6336 </div>
6337 <div class="sect2" lang="en">
6338 <div class="titlepage"><div><div><h3 class="title">
6339 <a name="zone_statement_grammar"></a><span><strong class="command">zone</strong></span>
6340             Statement Grammar</h3></div></div></div>
6341 <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>] {
6342     type master;
6343     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6344     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6345     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6346     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6347     [<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>]
6348     [<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>] ;
6349                   [<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>]
6350     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
6351     [<span class="optional"> check-mx (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
6352     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6353     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6354     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
6355     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
6356     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
6357     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
6358     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
6359     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
6360     [<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>]
6361     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
6362     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6363     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
6364     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6365     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
6366     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
6367     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
6368     [<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>]
6369     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
6370     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6371     [<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>]
6372     [<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>]
6373     [<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>]
6374     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6375     [<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>]
6376     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
6377     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
6378     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
6379     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
6380     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
6381     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
6382     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
6383     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
6384     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
6385     [<span class="optional"> auto-dnssec <code class="constant">allow</code>|<code class="constant">maintain</code>|<code class="constant">off</code>; </span>]
6386     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6387 };
6388
6389 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6390     type slave;
6391     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6392     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6393     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6394     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6395     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6396     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6397     [<span class="optional"> dnssec-update-mode ( <em class="replaceable"><code>maintain</code></em> | <em class="replaceable"><code>no-resign</code></em> ); </span>]
6398     [<span class="optional"> dnssec-dnskey-kskonly <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6399     [<span class="optional"> dnssec-secure-to-insecure <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6400     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6401     [<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>] ;
6402                   [<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>]
6403     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
6404     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
6405     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
6406     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
6407     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
6408     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
6409     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
6410     [<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>]
6411     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
6412     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6413     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
6414     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6415     [<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>
6416                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
6417                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
6418     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
6419     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
6420     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
6421     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
6422     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
6423     [<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>]
6424     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
6425     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6426     [<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>]
6427     [<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>]
6428     [<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>]
6429     [<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>]
6430     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
6431                              [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6432     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6433     [<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>]
6434     [<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>]
6435     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6436     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
6437     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
6438     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
6439     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
6440     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
6441     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6442     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6443 };
6444
6445 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6446     type hint;
6447     file <em class="replaceable"><code>string</code></em> ;
6448     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6449     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>] // Not Implemented.
6450 };
6451
6452 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6453     type stub;
6454     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6455     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6456     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
6457     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
6458     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6459     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
6460     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
6461     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
6462     [<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>]
6463     [<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>
6464                               [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>]
6465                               [<span class="optional">key <em class="replaceable"><code>key</code></em></span>] ) ; [<span class="optional">...</span>] }; </span>]
6466     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
6467     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
6468     [<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>]
6469     [<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>]
6470     [<span class="optional"> transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
6471                          [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6472     [<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>]
6473     [<span class="optional"> alt-transfer-source-v6 (<em class="replaceable"><code>ip6_addr</code></em> | <code class="constant">*</code>)
6474                             [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ; </span>]
6475     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
6476     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6477     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
6478     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
6479     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
6480     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
6481     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
6482     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6483 };
6484
6485 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6486     type static-stub;
6487     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
6488     [<span class="optional"> server-addresses { [<span class="optional"> <em class="replaceable"><code>ip_addr</code></em> ; ... </span>] }; </span>]
6489     [<span class="optional"> server-names { [<span class="optional"> <em class="replaceable"><code>namelist</code></em> </span>] }; </span>]
6490     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6491 };
6492
6493 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6494     type forward;
6495     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
6496     [<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>]
6497     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
6498 };
6499
6500 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
6501     type delegation-only;
6502 };
6503
6504 </pre>
6505 </div>
6506 <div class="sect2" lang="en">
6507 <div class="titlepage"><div><div><h3 class="title">
6508 <a name="id2591713"></a><span><strong class="command">zone</strong></span> Statement Definition and Usage</h3></div></div></div>
6509 <div class="sect3" lang="en">
6510 <div class="titlepage"><div><div><h4 class="title">
6511 <a name="id2591720"></a>Zone Types</h4></div></div></div>
6512 <div class="informaltable"><table border="1">
6513 <colgroup>
6514 <col>
6515 <col>
6516 </colgroup>
6517 <tbody>
6518 <tr>
6519 <td>
6520                       <p>
6521                         <code class="varname">master</code>
6522                       </p>
6523                     </td>
6524 <td>
6525                       <p>
6526                         The server has a master copy of the data
6527                         for the zone and will be able to provide authoritative
6528                         answers for
6529                         it.
6530                       </p>
6531                     </td>
6532 </tr>
6533 <tr>
6534 <td>
6535                       <p>
6536                         <code class="varname">slave</code>
6537                       </p>
6538                     </td>
6539 <td>
6540                       <p>
6541                         A slave zone is a replica of a master
6542                         zone. The <span><strong class="command">masters</strong></span> list
6543                         specifies one or more IP addresses
6544                         of master servers that the slave contacts to update
6545                         its copy of the zone.
6546                         Masters list elements can also be names of other
6547                         masters lists.
6548                         By default, transfers are made from port 53 on the
6549                         servers; this can
6550                         be changed for all servers by specifying a port number
6551                         before the
6552                         list of IP addresses, or on a per-server basis after
6553                         the IP address.
6554                         Authentication to the master can also be done with
6555                         per-server TSIG keys.
6556                         If a file is specified, then the
6557                         replica will be written to this file whenever the zone
6558                         is changed,
6559                         and reloaded from this file on a server restart. Use
6560                         of a file is
6561                         recommended, since it often speeds server startup and
6562                         eliminates
6563                         a needless waste of bandwidth. Note that for large
6564                         numbers (in the
6565                         tens or hundreds of thousands) of zones per server, it
6566                         is best to
6567                         use a two-level naming scheme for zone filenames. For
6568                         example,
6569                         a slave server for the zone <code class="literal">example.com</code> might place
6570                         the zone contents into a file called
6571                         <code class="filename">ex/example.com</code> where <code class="filename">ex/</code> is
6572                         just the first two letters of the zone name. (Most
6573                         operating systems
6574                         behave very slowly if you put 100000 files into
6575                         a single directory.)
6576                       </p>
6577                     </td>
6578 </tr>
6579 <tr>
6580 <td>
6581                       <p>
6582                         <code class="varname">stub</code>
6583                       </p>
6584                     </td>
6585 <td>
6586                       <p>
6587                         A stub zone is similar to a slave zone,
6588                         except that it replicates only the NS records of a
6589                         master zone instead
6590                         of the entire zone. Stub zones are not a standard part
6591                         of the DNS;
6592                         they are a feature specific to the <acronym class="acronym">BIND</acronym> implementation.
6593                       </p>
6594
6595                       <p>
6596                         Stub zones can be used to eliminate the need for glue
6597                         NS record
6598                         in a parent zone at the expense of maintaining a stub
6599                         zone entry and
6600                         a set of name server addresses in <code class="filename">named.conf</code>.
6601                         This usage is not recommended for new configurations,
6602                         and BIND 9
6603                         supports it only in a limited way.
6604                         In <acronym class="acronym">BIND</acronym> 4/8, zone
6605                         transfers of a parent zone
6606                         included the NS records from stub children of that
6607                         zone. This meant
6608                         that, in some cases, users could get away with
6609                         configuring child stubs
6610                         only in the master server for the parent zone. <acronym class="acronym">BIND</acronym>
6611                         9 never mixes together zone data from different zones
6612                         in this
6613                         way. Therefore, if a <acronym class="acronym">BIND</acronym> 9 master serving a parent
6614                         zone has child stub zones configured, all the slave
6615                         servers for the
6616                         parent zone also need to have the same child stub
6617                         zones
6618                         configured.
6619                       </p>
6620
6621                       <p>
6622                         Stub zones can also be used as a way of forcing the
6623                         resolution
6624                         of a given domain to use a particular set of
6625                         authoritative servers.
6626                         For example, the caching name servers on a private
6627                         network using
6628                         RFC1918 addressing may be configured with stub zones
6629                         for
6630                         <code class="literal">10.in-addr.arpa</code>
6631                         to use a set of internal name servers as the
6632                         authoritative
6633                         servers for that domain.
6634                       </p>
6635                     </td>
6636 </tr>
6637 <tr>
6638 <td>
6639                       <p>
6640                         <code class="varname">static-stub</code>
6641                       </p>
6642                     </td>
6643 <td>
6644                       <p>
6645                         A static-stub zone is similar to a stub zone
6646                         with the following exceptions:
6647                         the zone data is statically configured, rather
6648                         than transferred from a master server;
6649                         when recursion is necessary for a query that
6650                         matches a static-stub zone, the locally
6651                         configured data (nameserver names and glue addresses)
6652                         is always used even if different authoritative
6653                         information is cached.
6654                       </p>
6655                       <p>
6656                         Zone data is configured via the
6657                         <span><strong class="command">server-addresses</strong></span> and
6658                         <span><strong class="command">server-names</strong></span> zone options.
6659                       </p>
6660                       <p>
6661                         The zone data is maintained in the form of NS
6662                         and (if necessary) glue A or AAAA RRs
6663                         internally, which can be seen by dumping zone
6664                         databases by <span><strong class="command">rndc dumpdb -all</strong></span>.
6665                         The configured RRs are considered local configuration
6666                         parameters rather than public data.
6667                         Non recursive queries (i.e., those with the RD
6668                         bit off) to a static-stub zone are therefore
6669                         prohibited and will be responded with REFUSED.
6670                       </p>
6671                       <p>
6672                         Since the data is statically configured, no
6673                         zone maintenance action takes place for a static-stub
6674                         zone.
6675                         For example, there is no periodic refresh
6676                         attempt, and an incoming notify message
6677                         will be rejected with an rcode of NOTAUTH.
6678                       </p>
6679                       <p>
6680                         Each static-stub zone is configured with
6681                         internally generated NS and (if necessary)
6682                         glue A or AAAA RRs
6683                       </p>
6684                     </td>
6685 </tr>
6686 <tr>
6687 <td>
6688                       <p>
6689                         <code class="varname">forward</code>
6690                       </p>
6691                     </td>
6692 <td>
6693                       <p>
6694                         A "forward zone" is a way to configure
6695                         forwarding on a per-domain basis.  A <span><strong class="command">zone</strong></span> statement
6696                         of type <span><strong class="command">forward</strong></span> can
6697                         contain a <span><strong class="command">forward</strong></span>
6698                         and/or <span><strong class="command">forwarders</strong></span>
6699                         statement,
6700                         which will apply to queries within the domain given by
6701                         the zone
6702                         name. If no <span><strong class="command">forwarders</strong></span>
6703                         statement is present or
6704                         an empty list for <span><strong class="command">forwarders</strong></span> is given, then no
6705                         forwarding will be done for the domain, canceling the
6706                         effects of
6707                         any forwarders in the <span><strong class="command">options</strong></span> statement. Thus
6708                         if you want to use this type of zone to change the
6709                         behavior of the
6710                         global <span><strong class="command">forward</strong></span> option
6711                         (that is, "forward first"
6712                         to, then "forward only", or vice versa, but want to
6713                         use the same
6714                         servers as set globally) you need to re-specify the
6715                         global forwarders.
6716                       </p>
6717                     </td>
6718 </tr>
6719 <tr>
6720 <td>
6721                       <p>
6722                         <code class="varname">hint</code>
6723                       </p>
6724                     </td>
6725 <td>
6726                       <p>
6727                         The initial set of root name servers is
6728                         specified using a "hint zone". When the server starts
6729                         up, it uses
6730                         the root hints to find a root name server and get the
6731                         most recent
6732                         list of root name servers. If no hint zone is
6733                         specified for class
6734                         IN, the server uses a compiled-in default set of root
6735                         servers hints.
6736                         Classes other than IN have no built-in defaults hints.
6737                       </p>
6738                     </td>
6739 </tr>
6740 <tr>
6741 <td>
6742                       <p>
6743                         <code class="varname">delegation-only</code>
6744                       </p>
6745                     </td>
6746 <td>
6747                       <p>
6748                         This is used to enforce the delegation-only
6749                         status of infrastructure zones (e.g. COM,
6750                         NET, ORG).  Any answer that is received
6751                         without an explicit or implicit delegation
6752                         in the authority section will be treated
6753                         as NXDOMAIN.  This does not apply to the
6754                         zone apex.  This should not be applied to
6755                         leaf zones.
6756                       </p>
6757                       <p>
6758                         <code class="varname">delegation-only</code> has no
6759                         effect on answers received from forwarders.
6760                       </p>
6761                       <p>
6762                         See caveats in <a href="Bv9ARM.ch06.html#root_delegation_only"><span><strong class="command">root-delegation-only</strong></span></a>.
6763                       </p>
6764                     </td>
6765 </tr>
6766 </tbody>
6767 </table></div>
6768 </div>
6769 <div class="sect3" lang="en">
6770 <div class="titlepage"><div><div><h4 class="title">
6771 <a name="id2592402"></a>Class</h4></div></div></div>
6772 <p>
6773               The zone's name may optionally be followed by a class. If
6774               a class is not specified, class <code class="literal">IN</code> (for <code class="varname">Internet</code>),
6775               is assumed. This is correct for the vast majority of cases.
6776             </p>
6777 <p>
6778               The <code class="literal">hesiod</code> class is
6779               named for an information service from MIT's Project Athena. It
6780               is
6781               used to share information about various systems databases, such
6782               as users, groups, printers and so on. The keyword
6783               <code class="literal">HS</code> is
6784               a synonym for hesiod.
6785             </p>
6786 <p>
6787               Another MIT development is Chaosnet, a LAN protocol created
6788               in the mid-1970s. Zone data for it can be specified with the <code class="literal">CHAOS</code> class.
6789             </p>
6790 </div>
6791 <div class="sect3" lang="en">
6792 <div class="titlepage"><div><div><h4 class="title">
6793 <a name="id2592503"></a>Zone Options</h4></div></div></div>
6794 <div class="variablelist"><dl>
6795 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
6796 <dd><p>
6797                     See the description of
6798                     <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>.
6799                   </p></dd>
6800 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
6801 <dd><p>
6802                     See the description of
6803                     <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>.
6804                   </p></dd>
6805 <dt><span class="term"><span><strong class="command">allow-query-on</strong></span></span></dt>
6806 <dd><p>
6807                     See the description of
6808                     <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>.
6809                   </p></dd>
6810 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
6811 <dd><p>
6812                     See the description of <span><strong class="command">allow-transfer</strong></span>
6813                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
6814                   </p></dd>
6815 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
6816 <dd><p>
6817                     See the description of <span><strong class="command">allow-update</strong></span>
6818                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
6819                   </p></dd>
6820 <dt><span class="term"><span><strong class="command">update-policy</strong></span></span></dt>
6821 <dd><p>
6822                     Specifies a "Simple Secure Update" policy. See
6823                     <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>.
6824                   </p></dd>
6825 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
6826 <dd><p>
6827                     See the description of <span><strong class="command">allow-update-forwarding</strong></span>
6828                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
6829                   </p></dd>
6830 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
6831 <dd><p>
6832                     Only meaningful if <span><strong class="command">notify</strong></span>
6833                     is
6834                     active for this zone. The set of machines that will
6835                     receive a
6836                     <code class="literal">DNS NOTIFY</code> message
6837                     for this zone is made up of all the listed name servers
6838                     (other than
6839                     the primary master) for the zone plus any IP addresses
6840                     specified
6841                     with <span><strong class="command">also-notify</strong></span>. A port
6842                     may be specified
6843                     with each <span><strong class="command">also-notify</strong></span>
6844                     address to send the notify
6845                     messages to a port other than the default of 53.
6846                     <span><strong class="command">also-notify</strong></span> is not
6847                     meaningful for stub zones.
6848                     The default is the empty list.
6849                   </p></dd>
6850 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
6851 <dd><p>
6852                     This option is used to restrict the character set and
6853                     syntax of
6854                     certain domain names in master files and/or DNS responses
6855                     received from the
6856                     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>
6857                     zones the default is <span><strong class="command">warn</strong></span>.
6858                     It is not implemented for <span><strong class="command">hint</strong></span> zones.
6859                   </p></dd>
6860 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
6861 <dd><p>
6862                     See the description of
6863                     <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>.
6864                   </p></dd>
6865 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
6866 <dd><p>
6867                     See the description of
6868                     <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>.
6869                   </p></dd>
6870 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
6871 <dd><p>
6872                     See the description of
6873                     <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>.
6874                   </p></dd>
6875 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
6876 <dd><p>
6877                     See the description of
6878                     <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>.
6879                   </p></dd>
6880 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
6881 <dd><p>
6882                     See the description of
6883                     <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>.
6884                   </p></dd>
6885 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
6886 <dd><p>
6887                     See the description of
6888                     <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>.
6889                   </p></dd>
6890 <dt><span class="term"><span><strong class="command">dnssec-dnskey-kskonly</strong></span></span></dt>
6891 <dd><p>
6892                     See the description of
6893                     <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>.
6894                   </p></dd>
6895 <dt><span class="term"><span><strong class="command">try-tcp-refresh</strong></span></span></dt>
6896 <dd><p>
6897                     See the description of
6898                     <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>.
6899                   </p></dd>
6900 <dt><span class="term"><span><strong class="command">database</strong></span></span></dt>
6901 <dd>
6902 <p>
6903                     Specify the type of database to be used for storing the
6904                     zone data.  The string following the <span><strong class="command">database</strong></span> keyword
6905                     is interpreted as a list of whitespace-delimited words.
6906                     The first word
6907                     identifies the database type, and any subsequent words are
6908                     passed
6909                     as arguments to the database to be interpreted in a way
6910                     specific
6911                     to the database type.
6912                   </p>
6913 <p>
6914                     The default is <strong class="userinput"><code>"rbt"</code></strong>, BIND 9's
6915                     native in-memory
6916                     red-black-tree database.  This database does not take
6917                     arguments.
6918                   </p>
6919 <p>
6920                     Other values are possible if additional database drivers
6921                     have been linked into the server.  Some sample drivers are
6922                     included
6923                     with the distribution but none are linked in by default.
6924                   </p>
6925 </dd>
6926 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
6927 <dd><p>
6928                     See the description of
6929                     <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>.
6930                   </p></dd>
6931 <dt><span class="term"><span><strong class="command">delegation-only</strong></span></span></dt>
6932 <dd>
6933 <p>
6934                     The flag only applies to hint and stub zones.  If set
6935                     to <strong class="userinput"><code>yes</code></strong>, then the zone will also be
6936                     treated as if it is also a delegation-only type zone.
6937                   </p>
6938 <p>
6939                     See caveats in <a href="Bv9ARM.ch06.html#root_delegation_only"><span><strong class="command">root-delegation-only</strong></span></a>.
6940                   </p>
6941 </dd>
6942 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
6943 <dd><p>
6944                     Only meaningful if the zone has a forwarders
6945                     list. The <span><strong class="command">only</strong></span> value causes
6946                     the lookup to fail
6947                     after trying the forwarders and getting no answer, while <span><strong class="command">first</strong></span> would
6948                     allow a normal lookup to be tried.
6949                   </p></dd>
6950 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
6951 <dd><p>
6952                     Used to override the list of global forwarders.
6953                     If it is not specified in a zone of type <span><strong class="command">forward</strong></span>,
6954                     no forwarding is done for the zone and the global options are
6955                     not used.
6956                   </p></dd>
6957 <dt><span class="term"><span><strong class="command">ixfr-base</strong></span></span></dt>
6958 <dd><p>
6959                     Was used in <acronym class="acronym">BIND</acronym> 8 to
6960                     specify the name
6961                     of the transaction log (journal) file for dynamic update
6962                     and IXFR.
6963                     <acronym class="acronym">BIND</acronym> 9 ignores the option
6964                     and constructs the name of the journal
6965                     file by appending "<code class="filename">.jnl</code>"
6966                     to the name of the
6967                     zone file.
6968                   </p></dd>
6969 <dt><span class="term"><span><strong class="command">ixfr-tmp-file</strong></span></span></dt>
6970 <dd><p>
6971                     Was an undocumented option in <acronym class="acronym">BIND</acronym> 8.
6972                     Ignored in <acronym class="acronym">BIND</acronym> 9.
6973                   </p></dd>
6974 <dt><span class="term"><span><strong class="command">journal</strong></span></span></dt>
6975 <dd><p>
6976                     Allow the default journal's filename to be overridden.
6977                     The default is the zone's filename with "<code class="filename">.jnl</code>" appended.
6978                     This is applicable to <span><strong class="command">master</strong></span> and <span><strong class="command">slave</strong></span> zones.
6979                   </p></dd>
6980 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
6981 <dd><p>
6982                     See the description of
6983                     <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>.
6984                   </p></dd>
6985 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
6986 <dd><p>
6987                     See the description of
6988                     <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>.
6989                   </p></dd>
6990 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
6991 <dd><p>
6992                     See the description of
6993                     <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>.
6994                   </p></dd>
6995 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
6996 <dd><p>
6997                     See the description of
6998                     <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>.
6999                   </p></dd>
7000 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
7001 <dd><p>
7002                     See the description of
7003                     <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>.
7004                   </p></dd>
7005 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
7006 <dd><p>
7007                     See the description of
7008                     <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>.
7009                   </p></dd>
7010 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
7011 <dd><p>
7012                     See the description of
7013                     <span><strong class="command">notify-delay</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
7014                   </p></dd>
7015 <dt><span class="term"><span><strong class="command">notify-to-soa</strong></span></span></dt>
7016 <dd><p>
7017                     See the description of
7018                     <span><strong class="command">notify-to-soa</strong></span> in
7019                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7020                   </p></dd>
7021 <dt><span class="term"><span><strong class="command">pubkey</strong></span></span></dt>
7022 <dd><p>
7023                     In <acronym class="acronym">BIND</acronym> 8, this option was
7024                     intended for specifying
7025                     a public zone key for verification of signatures in DNSSEC
7026                     signed
7027                     zones when they are loaded from disk. <acronym class="acronym">BIND</acronym> 9 does not verify signatures
7028                     on load and ignores the option.
7029                   </p></dd>
7030 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
7031 <dd><p>
7032                     If <strong class="userinput"><code>yes</code></strong>, the server will keep
7033                     statistical
7034                     information for this zone, which can be dumped to the
7035                     <span><strong class="command">statistics-file</strong></span> defined in
7036                     the server options.
7037                   </p></dd>
7038 <dt><span class="term"><span><strong class="command">server-addresses</strong></span></span></dt>
7039 <dd>
7040 <p>
7041                     Only meaningful for static-stub zones.
7042                     This is a list of IP addresses to which queries
7043                     should be sent in recursive resolution for the
7044                     zone.
7045                     A non empty list for this option will internally
7046                     configure the apex NS RR with associated glue A or
7047                     AAAA RRs.
7048                   </p>
7049 <p>
7050                     For example, if "example.com" is configured as a
7051                     static-stub zone with 192.0.2.1 and 2001:db8::1234
7052                     in a <span><strong class="command">server-addresses</strong></span> option,
7053                     the following RRs will be internally configured.
7054                   </p>
7055 <pre class="programlisting">example.com. NS example.com.
7056 example.com. A 192.0.2.1
7057 example.com. AAAA 2001:db8::1234</pre>
7058 <p>
7059                     These records are internally used to resolve
7060                     names under the static-stub zone.
7061                     For instance, if the server receives a query for
7062                     "www.example.com" with the RD bit on, the server
7063                     will initiate recursive resolution and send
7064                     queries to 192.0.2.1 and/or 2001:db8::1234.
7065                   </p>
7066 </dd>
7067 <dt><span class="term"><span><strong class="command">server-names</strong></span></span></dt>
7068 <dd>
7069 <p>
7070                     Only meaningful for static-stub zones.
7071                     This is a list of domain names of nameservers that
7072                     act as authoritative servers of the static-stub
7073                     zone.
7074                     These names will be resolved to IP addresses when
7075                     <span><strong class="command">named</strong></span> needs to send queries to
7076                     these servers.
7077                     To make this supplemental resolution successful,
7078                     these names must not be a subdomain of the origin
7079                     name of static-stub zone.
7080                     That is, when "example.net" is the origin of a
7081                     static-stub zone, "ns.example" and
7082                     "master.example.com" can be specified in the
7083                     <span><strong class="command">server-names</strong></span> option, but
7084                     "ns.example.net" cannot, and will be rejected by
7085                     the configuration parser.
7086                   </p>
7087 <p>
7088                     A non empty list for this option will internally
7089                     configure the apex NS RR with the specified names.
7090                     For example, if "example.com" is configured as a
7091                     static-stub zone with "ns1.example.net" and
7092                     "ns2.example.net"
7093                     in a <span><strong class="command">server-names</strong></span> option,
7094                     the following RRs will be internally configured.
7095                   </p>
7096 <pre class="programlisting">example.com. NS ns1.example.net.
7097 example.com. NS ns2.example.net.
7098 </pre>
7099 <p>
7100                     These records are internally used to resolve
7101                     names under the static-stub zone.
7102                     For instance, if the server receives a query for
7103                     "www.example.com" with the RD bit on, the server
7104                     initiate recursive resolution,
7105                     resolve "ns1.example.net" and/or
7106                     "ns2.example.net" to IP addresses, and then send
7107                     queries to (one or more of) these addresses.
7108                   </p>
7109 </dd>
7110 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
7111 <dd><p>
7112                     See the description of
7113                     <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>.
7114                   </p></dd>
7115 <dt><span class="term"><span><strong class="command">sig-signing-nodes</strong></span></span></dt>
7116 <dd><p>
7117                     See the description of
7118                     <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>.
7119                   </p></dd>
7120 <dt><span class="term"><span><strong class="command">sig-signing-signatures</strong></span></span></dt>
7121 <dd><p>
7122                     See the description of
7123                     <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>.
7124                   </p></dd>
7125 <dt><span class="term"><span><strong class="command">sig-signing-type</strong></span></span></dt>
7126 <dd><p>
7127                     See the description of
7128                     <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>.
7129                   </p></dd>
7130 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
7131 <dd><p>
7132                     See the description of
7133                     <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>.
7134                   </p></dd>
7135 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
7136 <dd><p>
7137                     See the description of
7138                     <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>.
7139                   </p></dd>
7140 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
7141 <dd><p>
7142                     See the description of
7143                     <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>.
7144                   </p></dd>
7145 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
7146 <dd><p>
7147                     See the description of
7148                     <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>.
7149                   </p></dd>
7150 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
7151 <dd><p>
7152                     See the description of
7153                     <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>.
7154                   </p></dd>
7155 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
7156 <dd><p>
7157                     See the description of
7158                     <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>.
7159                   </p></dd>
7160 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
7161 <dd><p>
7162                     See the description of
7163                     <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>.
7164                   </p></dd>
7165 <dt>
7166 <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>
7167 </dt>
7168 <dd><p>
7169                     See the description in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
7170                   </p></dd>
7171 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
7172 <dd><p>
7173                     See the description of
7174                     <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>.
7175                     (Note that the <span><strong class="command">ixfr-from-differences</strong></span>
7176                     <strong class="userinput"><code>master</code></strong> and
7177                     <strong class="userinput"><code>slave</code></strong> choices are not
7178                     available at the zone level.)
7179                   </p></dd>
7180 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
7181 <dd><p>
7182                     See the description of
7183                     <span><strong class="command">key-directory</strong></span> in <a href="Bv9ARM.ch06.html#options" title="options Statement Definition and
7184           Usage">the section called &#8220;<span><strong class="command">options</strong></span> Statement Definition and
7185           Usage&#8221;</a>.
7186                   </p></dd>
7187 <dt><span class="term"><span><strong class="command">auto-dnssec</strong></span></span></dt>
7188 <dd>
7189 <p>
7190                     Zones configured for dynamic DNS may also use this
7191                     option to allow varying levels of automatic DNSSEC key
7192                     management. There are three possible settings:
7193                   </p>
7194 <p>
7195                     <span><strong class="command">auto-dnssec allow;</strong></span> permits
7196                     keys to be updated and the zone fully re-signed
7197                     whenever the user issues the command <span><strong class="command">rndc sign
7198                     <em class="replaceable"><code>zonename</code></em></strong></span>.
7199                   </p>
7200 <p>
7201                     <span><strong class="command">auto-dnssec maintain;</strong></span> includes the
7202                     above, but also automatically adjusts the zone's DNSSEC
7203                     keys on schedule, according to the keys' timing metadata
7204                     (see <a href="man.dnssec-keygen.html" title="dnssec-keygen"><span class="refentrytitle"><span class="application">dnssec-keygen</span></span>(8)</a> and
7205                     <a href="man.dnssec-settime.html" title="dnssec-settime"><span class="refentrytitle"><span class="application">dnssec-settime</span></span>(8)</a>).  The command
7206                     <span><strong class="command">rndc sign
7207                     <em class="replaceable"><code>zonename</code></em></strong></span> causes
7208                     <span><strong class="command">named</strong></span> to load keys from the key
7209                     repository and sign the zone with all keys that are
7210                     active.
7211                     <span><strong class="command">rndc loadkeys
7212                     <em class="replaceable"><code>zonename</code></em></strong></span> causes
7213                     <span><strong class="command">named</strong></span> to load keys from the key
7214                     repository and schedule key maintenance events to occur
7215                     in the future, but it does not sign the full zone
7216                     immediately.  Note: once keys have been loaded for a
7217                     zone the first time, the repository will be searched
7218                     for changes periodically, regardless of whether
7219                     <span><strong class="command">rndc loadkeys</strong></span> is used.  The recheck
7220                     interval is hard-coded to
7221                     one hour.
7222                   </p>
7223 <p>
7224                     <span><strong class="command">auto-dnssec create;</strong></span> includes the
7225                     above, but also allows <span><strong class="command">named</strong></span>
7226                     to create new keys in the key repository when needed.
7227                     (NOTE: This option is not yet implemented; the syntax is
7228                     being reserved for future use.)
7229                   </p>
7230 <p>
7231                     The default setting is <span><strong class="command">auto-dnssec off</strong></span>.
7232                   </p>
7233 </dd>
7234 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
7235 <dd><p>
7236                     See the description of <span><strong class="command">multi-master</strong></span> in
7237                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
7238                   </p></dd>
7239 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
7240 <dd><p>
7241                     See the description of <span><strong class="command">masterfile-format</strong></span>
7242                     in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
7243                   </p></dd>
7244 <dt><span class="term"><span><strong class="command">dnssec-secure-to-insecure</strong></span></span></dt>
7245 <dd><p>
7246                     See the description of
7247                     <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>.
7248                   </p></dd>
7249 </dl></div>
7250 </div>
7251 <div class="sect3" lang="en">
7252 <div class="titlepage"><div><div><h4 class="title">
7253 <a name="dynamic_update_policies"></a>Dynamic Update Policies</h4></div></div></div>
7254 <p><acronym class="acronym">BIND</acronym> 9 supports two alternative
7255               methods of granting clients the right to perform
7256               dynamic updates to a zone, configured by the
7257               <span><strong class="command">allow-update</strong></span> and
7258               <span><strong class="command">update-policy</strong></span> option, respectively.
7259             </p>
7260 <p>
7261               The <span><strong class="command">allow-update</strong></span> clause works the
7262               same way as in previous versions of <acronym class="acronym">BIND</acronym>.
7263               It grants given clients the permission to update any
7264               record of any name in the zone.
7265             </p>
7266 <p>
7267               The <span><strong class="command">update-policy</strong></span> clause
7268               allows more fine-grained control over what updates are
7269               allowed.  A set of rules is specified, where each rule
7270               either grants or denies permissions for one or more
7271               names to be updated by one or more identities.  If
7272               the dynamic update request message is signed (that is,
7273               it includes either a TSIG or SIG(0) record), the
7274               identity of the signer can be determined.
7275             </p>
7276 <p>
7277               Rules are specified in the <span><strong class="command">update-policy</strong></span>
7278               zone option, and are only meaningful for master zones.
7279               When the <span><strong class="command">update-policy</strong></span> statement
7280               is present, it is a configuration error for the
7281               <span><strong class="command">allow-update</strong></span> statement to be
7282               present.  The <span><strong class="command">update-policy</strong></span> statement
7283               only examines the signer of a message; the source
7284               address is not relevant.
7285             </p>
7286 <p>
7287               There is a pre-defined <span><strong class="command">update-policy</strong></span>
7288               rule which can be switched on with the command
7289               <span><strong class="command">update-policy local;</strong></span>.
7290               Switching on this rule in a zone causes
7291               <span><strong class="command">named</strong></span> to generate a TSIG session
7292               key and place it in a file, and to allow that key
7293               to update the zone.  (By default, the file is
7294               <code class="filename">/var/run/named/session.key</code>, the key
7295               name is "local-ddns" and the key algorithm is HMAC-SHA256,
7296               but these values are configurable with the
7297               <span><strong class="command">session-keyfile</strong></span>,
7298               <span><strong class="command">session-keyname</strong></span> and
7299               <span><strong class="command">session-keyalg</strong></span> options, respectively).
7300             </p>
7301 <p>
7302               A client running on the local system, and with appropriate
7303               permissions, may read that file and use the key to sign update
7304               requests.  The zone's update policy will be set to allow that
7305               key to change any record within the zone.  Assuming the
7306               key name is "local-ddns", this policy is equivalent to:
7307             </p>
7308 <pre class="programlisting">update-policy { grant local-ddns zonesub any; };
7309             </pre>
7310 <p>
7311               The command <span><strong class="command">nsupdate -l</strong></span> sends update
7312               requests to localhost, and signs them using the session key.
7313             </p>
7314 <p>
7315               Other rule definitions look like this:
7316             </p>
7317 <pre class="programlisting">
7318 ( <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>]
7319 </pre>
7320 <p>
7321               Each rule grants or denies privileges.  Once a message has
7322               successfully matched a rule, the operation is immediately
7323               granted or denied and no further rules are examined.  A rule
7324               is matched when the signer matches the identity field, the
7325               name matches the name field in accordance with the nametype
7326               field, and the type matches the types specified in the type
7327               field.
7328             </p>
7329 <p>
7330               No signer is required for <em class="replaceable"><code>tcp-self</code></em>
7331               or <em class="replaceable"><code>6to4-self</code></em> however the standard
7332               reverse mapping / prefix conversion must match the identity
7333               field.
7334             </p>
7335 <p>
7336               The identity field specifies a name or a wildcard
7337               name.  Normally, this is the name of the TSIG or
7338               SIG(0) key used to sign the update request.  When a
7339               TKEY exchange has been used to create a shared secret,
7340               the identity of the shared secret is the same as the
7341               identity of the key used to authenticate the TKEY
7342               exchange.  TKEY is also the negotiation method used
7343               by GSS-TSIG, which establishes an identity that is
7344               the Kerberos principal of the client, such as
7345               <strong class="userinput"><code>"user@host.domain"</code></strong>.  When the
7346               <em class="replaceable"><code>identity</code></em> field specifies
7347               a wildcard name, it is subject to DNS wildcard
7348               expansion, so the rule will apply to multiple identities.
7349               The <em class="replaceable"><code>identity</code></em> field must
7350               contain a fully-qualified domain name.
7351             </p>
7352 <p>
7353               For nametypes <code class="varname">krb5-self</code>,
7354               <code class="varname">ms-self</code>, <code class="varname">krb5-subdomain</code>,
7355               and <code class="varname">ms-subdomain</code> the
7356               <em class="replaceable"><code>identity</code></em> field specifies
7357               the Windows or Kerberos realm of the machine belongs to.
7358             </p>
7359 <p>
7360               The <em class="replaceable"><code>nametype</code></em> field has 13
7361               values:
7362               <code class="varname">name</code>, <code class="varname">subdomain</code>,
7363               <code class="varname">wildcard</code>, <code class="varname">self</code>,
7364               <code class="varname">selfsub</code>, <code class="varname">selfwild</code>,
7365               <code class="varname">krb5-self</code>, <code class="varname">ms-self</code>,
7366               <code class="varname">krb5-subdomain</code>,
7367               <code class="varname">ms-subdomain</code>,
7368               <code class="varname">tcp-self</code>, <code class="varname">6to4-self</code>,
7369               <code class="varname">zonesub</code>, and <code class="varname">external</code>.
7370             </p>
7371 <div class="informaltable"><table border="1">
7372 <colgroup>
7373 <col>
7374 <col>
7375 </colgroup>
7376 <tbody>
7377 <tr>
7378 <td>
7379                       <p>
7380                         <code class="varname">name</code>
7381                       </p>
7382                     </td>
7383 <td>
7384                       <p>
7385                         Exact-match semantics.  This rule matches
7386                         when the name being updated is identical
7387                         to the contents of the
7388                         <em class="replaceable"><code>name</code></em> field.
7389                       </p>
7390                     </td>
7391 </tr>
7392 <tr>
7393 <td>
7394                       <p>
7395                         <code class="varname">subdomain</code>
7396                       </p>
7397                     </td>
7398 <td>
7399                       <p>
7400                         This rule matches when the name being updated
7401                         is a subdomain of, or identical to, the
7402                         contents of the <em class="replaceable"><code>name</code></em>
7403                         field.
7404                       </p>
7405                     </td>
7406 </tr>
7407 <tr>
7408 <td>
7409                       <p>
7410                         <code class="varname">zonesub</code>
7411                       </p>
7412                     </td>
7413 <td>
7414                       <p>
7415                         This rule is similar to subdomain, except that
7416                         it matches when the name being updated is a
7417                         subdomain of the zone in which the
7418                         <span><strong class="command">update-policy</strong></span> statement
7419                         appears.  This obviates the need to type the zone
7420                         name twice, and enables the use of a standard
7421                         <span><strong class="command">update-policy</strong></span> statement in
7422                         multiple zones without modification.
7423                       </p>
7424                       <p>
7425                         When this rule is used, the
7426                         <em class="replaceable"><code>name</code></em> field is omitted.
7427                       </p>
7428                     </td>
7429 </tr>
7430 <tr>
7431 <td>
7432                       <p>
7433                         <code class="varname">wildcard</code>
7434                       </p>
7435                     </td>
7436 <td>
7437                       <p>
7438                         The <em class="replaceable"><code>name</code></em> field
7439                         is subject to DNS wildcard expansion, and
7440                         this rule matches when the name being updated
7441                         name is a valid expansion of the wildcard.
7442                       </p>
7443                     </td>
7444 </tr>
7445 <tr>
7446 <td>
7447                       <p>
7448                         <code class="varname">self</code>
7449                       </p>
7450                     </td>
7451 <td>
7452                       <p>
7453                         This rule matches when the name being updated
7454                         matches the contents of the
7455                         <em class="replaceable"><code>identity</code></em> field.
7456                         The <em class="replaceable"><code>name</code></em> field
7457                         is ignored, but should be the same as the
7458                         <em class="replaceable"><code>identity</code></em> field.
7459                         The <code class="varname">self</code> nametype is
7460                         most useful when allowing using one key per
7461                         name to update, where the key has the same
7462                         name as the name to be updated.  The
7463                         <em class="replaceable"><code>identity</code></em> would
7464                         be specified as <code class="constant">*</code> (an asterisk) in
7465                         this case.
7466                       </p>
7467                     </td>
7468 </tr>
7469 <tr>
7470 <td>
7471                       <p>
7472                         <code class="varname">selfsub</code>
7473                       </p>
7474                     </td>
7475 <td>
7476                       <p>
7477                         This rule is similar to <code class="varname">self</code>
7478                         except that subdomains of <code class="varname">self</code>
7479                         can also be updated.
7480                       </p>
7481                     </td>
7482 </tr>
7483 <tr>
7484 <td>
7485                       <p>
7486                         <code class="varname">selfwild</code>
7487                       </p>
7488                     </td>
7489 <td>
7490                       <p>
7491                         This rule is similar to <code class="varname">self</code>
7492                         except that only subdomains of
7493                         <code class="varname">self</code> can be updated.
7494                       </p>
7495                     </td>
7496 </tr>
7497 <tr>
7498 <td>
7499                       <p>
7500                         <code class="varname">ms-self</code>
7501                       </p>
7502                     </td>
7503 <td>
7504                       <p>
7505                         This rule takes a Windows machine principal
7506                         (machine$@REALM) for machine in REALM and
7507                         and converts it machine.realm allowing the machine
7508                         to update machine.realm.  The REALM to be matched
7509                         is specified in the <font color="red">&lt;replacable&gt;identity&lt;/replacable&gt;</font>
7510                         field.
7511                       </p>
7512                     </td>
7513 </tr>
7514 <tr>
7515 <td>
7516                       <p>
7517                         <code class="varname">ms-subdomain</code>
7518                       </p>
7519                     </td>
7520 <td>
7521                       <p>
7522                         This rule takes a Windows machine principal
7523                         (machine$@REALM) for machine in REALM and
7524                         converts it to machine.realm allowing the machine
7525                         to update subdomains of machine.realm.  The REALM
7526                         to be matched is specified in the
7527                         <font color="red">&lt;replacable&gt;identity&lt;/replacable&gt;</font> field.
7528                       </p>
7529                     </td>
7530 </tr>
7531 <tr>
7532 <td>
7533                       <p>
7534                         <code class="varname">krb5-self</code>
7535                       </p>
7536                     </td>
7537 <td>
7538                       <p>
7539                         This rule takes a Kerberos machine principal
7540                         (host/machine@REALM) for machine in REALM and
7541                         and converts it machine.realm allowing the machine
7542                         to update machine.realm.  The REALM to be matched
7543                         is specified in the <font color="red">&lt;replacable&gt;identity&lt;/replacable&gt;</font>
7544                         field.
7545                       </p>
7546                     </td>
7547 </tr>
7548 <tr>
7549 <td>
7550                       <p>
7551                         <code class="varname">krb5-subdomain</code>
7552                       </p>
7553                     </td>
7554 <td>
7555                       <p>
7556                         This rule takes a Kerberos machine principal
7557                         (host/machine@REALM) for machine in REALM and
7558                         converts it to machine.realm allowing the machine
7559                         to update subdomains of machine.realm.  The REALM
7560                         to be matched is specified in the
7561                         <font color="red">&lt;replacable&gt;identity&lt;/replacable&gt;</font> field.
7562                       </p>
7563                     </td>
7564 </tr>
7565 <tr>
7566 <td>
7567                       <p>
7568                         <code class="varname">tcp-self</code>
7569                       </p>
7570                     </td>
7571 <td>
7572                       <p>
7573                         Allow updates that have been sent via TCP and
7574                         for which the standard mapping from the initiating
7575                         IP address into the IN-ADDR.ARPA and IP6.ARPA
7576                         namespaces match the name to be updated.
7577                       </p>
7578                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
7579 <h3 class="title">Note</h3>
7580                         It is theoretically possible to spoof these TCP
7581                         sessions.
7582                       </div>
7583                     </td>
7584 </tr>
7585 <tr>
7586 <td>
7587                       <p>
7588                         <code class="varname">6to4-self</code>
7589                       </p>
7590                     </td>
7591 <td>
7592                       <p>
7593                         Allow the 6to4 prefix to be update by any TCP
7594                         connection from the 6to4 network or from the
7595                         corresponding IPv4 address.  This is intended
7596                         to allow NS or DNAME RRsets to be added to the
7597                         reverse tree.
7598                       </p>
7599                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
7600 <h3 class="title">Note</h3>
7601                         It is theoretically possible to spoof these TCP
7602                         sessions.
7603                       </div>
7604                     </td>
7605 </tr>
7606 <tr>
7607 <td>
7608                       <p>
7609                         <code class="varname">external</code>
7610                       </p>
7611                     </td>
7612 <td>
7613                       <p>
7614                         This rule allows <span><strong class="command">named</strong></span>
7615                         to defer the decision of whether to allow a
7616                         given update to an external daemon.
7617                       </p>
7618                       <p>
7619                         The method of communicating with the daemon is
7620                         specified in the <em class="replaceable"><code>identity</code></em>
7621                         field, the format of which is
7622                         "<code class="constant">local:</code><em class="replaceable"><code>path</code></em>",
7623                         where <em class="replaceable"><code>path</code></em> is the location
7624                         of a UNIX-domain socket.  (Currently, "local" is the
7625                         only supported mechanism.)
7626                       </p>
7627                       <p>
7628                         Requests to the external daemon are sent over the
7629                         UNIX-domain socket as datagrams with the following
7630                         format:
7631                       </p>
7632                       <pre class="programlisting">
7633    Protocol version number (4 bytes, network byte order, currently 1)
7634    Request length (4 bytes, network byte order)
7635    Signer (null-terminated string)
7636    Name (null-terminated string)
7637    TCP source address (null-terminated string)
7638    Rdata type (null-terminated string)
7639    Key (null-terminated string)
7640    TKEY token length (4 bytes, network byte order)
7641    TKEY token (remainder of packet)</pre>
7642                       <p>
7643                         The daemon replies with a four-byte value in
7644                         network byte order, containing either 0 or 1; 0
7645                         indicates that the specified update is not
7646                         permitted, and 1 indicates that it is.
7647                       </p>
7648                     </td>
7649 </tr>
7650 </tbody>
7651 </table></div>
7652 <p>
7653               In all cases, the <em class="replaceable"><code>name</code></em>
7654               field must specify a fully-qualified domain name.
7655             </p>
7656 <p>
7657               If no types are explicitly specified, this rule matches
7658               all types except RRSIG, NS, SOA, NSEC and NSEC3. Types
7659               may be specified by name, including "ANY" (ANY matches
7660               all types except NSEC and NSEC3, which can never be
7661               updated).  Note that when an attempt is made to delete
7662               all records associated with a name, the rules are
7663               checked for each existing record type.
7664             </p>
7665 </div>
7666 </div>
7667 </div>
7668 <div class="sect1" lang="en">
7669 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
7670 <a name="id2595116"></a>Zone File</h2></div></div></div>
7671 <div class="sect2" lang="en">
7672 <div class="titlepage"><div><div><h3 class="title">
7673 <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>
7674 <p>
7675             This section, largely borrowed from RFC 1034, describes the
7676             concept of a Resource Record (RR) and explains when each is used.
7677             Since the publication of RFC 1034, several new RRs have been
7678             identified
7679             and implemented in the DNS. These are also included.
7680           </p>
7681 <div class="sect3" lang="en">
7682 <div class="titlepage"><div><div><h4 class="title">
7683 <a name="id2595134"></a>Resource Records</h4></div></div></div>
7684 <p>
7685               A domain name identifies a node.  Each node has a set of
7686               resource information, which may be empty.  The set of resource
7687               information associated with a particular name is composed of
7688               separate RRs. The order of RRs in a set is not significant and
7689               need not be preserved by name servers, resolvers, or other
7690               parts of the DNS. However, sorting of multiple RRs is
7691               permitted for optimization purposes, for example, to specify
7692               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>.
7693             </p>
7694 <p>
7695               The components of a Resource Record are:
7696             </p>
7697 <div class="informaltable"><table border="1">
7698 <colgroup>
7699 <col>
7700 <col>
7701 </colgroup>
7702 <tbody>
7703 <tr>
7704 <td>
7705                       <p>
7706                         owner name
7707                       </p>
7708                     </td>
7709 <td>
7710                       <p>
7711                         The domain name where the RR is found.
7712                       </p>
7713                     </td>
7714 </tr>
7715 <tr>
7716 <td>
7717                       <p>
7718                         type
7719                       </p>
7720                     </td>
7721 <td>
7722                       <p>
7723                         An encoded 16-bit value that specifies
7724                         the type of the resource record.
7725                       </p>
7726                     </td>
7727 </tr>
7728 <tr>
7729 <td>
7730                       <p>
7731                         TTL
7732                       </p>
7733                     </td>
7734 <td>
7735                       <p>
7736                         The time-to-live of the RR. This field
7737                         is a 32-bit integer in units of seconds, and is
7738                         primarily used by
7739                         resolvers when they cache RRs. The TTL describes how
7740                         long a RR can
7741                         be cached before it should be discarded.
7742                       </p>
7743                     </td>
7744 </tr>
7745 <tr>
7746 <td>
7747                       <p>
7748                         class
7749                       </p>
7750                     </td>
7751 <td>
7752                       <p>
7753                         An encoded 16-bit value that identifies
7754                         a protocol family or instance of a protocol.
7755                       </p>
7756                     </td>
7757 </tr>
7758 <tr>
7759 <td>
7760                       <p>
7761                         RDATA
7762                       </p>
7763                     </td>
7764 <td>
7765                       <p>
7766                         The resource data.  The format of the
7767                         data is type (and sometimes class) specific.
7768                       </p>
7769                     </td>
7770 </tr>
7771 </tbody>
7772 </table></div>
7773 <p>
7774               The following are <span class="emphasis"><em>types</em></span> of valid RRs:
7775             </p>
7776 <div class="informaltable"><table border="1">
7777 <colgroup>
7778 <col>
7779 <col>
7780 </colgroup>
7781 <tbody>
7782 <tr>
7783 <td>
7784                       <p>
7785                         A
7786                       </p>
7787                     </td>
7788 <td>
7789                       <p>
7790                         A host address.  In the IN class, this is a
7791                         32-bit IP address.  Described in RFC 1035.
7792                       </p>
7793                     </td>
7794 </tr>
7795 <tr>
7796 <td>
7797                       <p>
7798                         AAAA
7799                       </p>
7800                     </td>
7801 <td>
7802                       <p>
7803                         IPv6 address.  Described in RFC 1886.
7804                       </p>
7805                     </td>
7806 </tr>
7807 <tr>
7808 <td>
7809                       <p>
7810                         A6
7811                       </p>
7812                     </td>
7813 <td>
7814                       <p>
7815                         IPv6 address.  This can be a partial
7816                         address (a suffix) and an indirection to the name
7817                         where the rest of the
7818                         address (the prefix) can be found.  Experimental.
7819                         Described in RFC 2874.
7820                       </p>
7821                     </td>
7822 </tr>
7823 <tr>
7824 <td>
7825                       <p>
7826                         AFSDB
7827                       </p>
7828                     </td>
7829 <td>
7830                       <p>
7831                         Location of AFS database servers.
7832                         Experimental.  Described in RFC 1183.
7833                       </p>
7834                     </td>
7835 </tr>
7836 <tr>
7837 <td>
7838                       <p>
7839                         APL
7840                       </p>
7841                     </td>
7842 <td>
7843                       <p>
7844                         Address prefix list.  Experimental.
7845                         Described in RFC 3123.
7846                       </p>
7847                     </td>
7848 </tr>
7849 <tr>
7850 <td>
7851                       <p>
7852                         CERT
7853                       </p>
7854                     </td>
7855 <td>
7856                       <p>
7857                         Holds a digital certificate.
7858                         Described in RFC 2538.
7859                       </p>
7860                     </td>
7861 </tr>
7862 <tr>
7863 <td>
7864                       <p>
7865                         CNAME
7866                       </p>
7867                     </td>
7868 <td>
7869                       <p>
7870                         Identifies the canonical name of an alias.
7871                         Described in RFC 1035.
7872                       </p>
7873                     </td>
7874 </tr>
7875 <tr>
7876 <td>
7877                       <p>
7878                         DHCID
7879                       </p>
7880                     </td>
7881 <td>
7882                       <p>
7883                         Is used for identifying which DHCP client is
7884                         associated with this name.  Described in RFC 4701.
7885                       </p>
7886                     </td>
7887 </tr>
7888 <tr>
7889 <td>
7890                       <p>
7891                         DNAME
7892                       </p>
7893                     </td>
7894 <td>
7895                       <p>
7896                         Replaces the domain name specified with
7897                         another name to be looked up, effectively aliasing an
7898                         entire
7899                         subtree of the domain name space rather than a single
7900                         record
7901                         as in the case of the CNAME RR.
7902                         Described in RFC 2672.
7903                       </p>
7904                     </td>
7905 </tr>
7906 <tr>
7907 <td>
7908                       <p>
7909                         DNSKEY
7910                       </p>
7911                     </td>
7912 <td>
7913                       <p>
7914                         Stores a public key associated with a signed
7915                         DNS zone.  Described in RFC 4034.
7916                       </p>
7917                     </td>
7918 </tr>
7919 <tr>
7920 <td>
7921                       <p>
7922                         DS
7923                       </p>
7924                     </td>
7925 <td>
7926                       <p>
7927                         Stores the hash of a public key associated with a
7928                         signed DNS zone.  Described in RFC 4034.
7929                       </p>
7930                     </td>
7931 </tr>
7932 <tr>
7933 <td>
7934                       <p>
7935                         GPOS
7936                       </p>
7937                     </td>
7938 <td>
7939                       <p>
7940                         Specifies the global position.  Superseded by LOC.
7941                       </p>
7942                     </td>
7943 </tr>
7944 <tr>
7945 <td>
7946                       <p>
7947                         HINFO
7948                       </p>
7949                     </td>
7950 <td>
7951                       <p>
7952                         Identifies the CPU and OS used by a host.
7953                         Described in RFC 1035.
7954                       </p>
7955                     </td>
7956 </tr>
7957 <tr>
7958 <td>
7959                       <p>
7960                         IPSECKEY
7961                       </p>
7962                     </td>
7963 <td>
7964                       <p>
7965                         Provides a method for storing IPsec keying material in
7966                         DNS.  Described in RFC 4025.
7967                       </p>
7968                     </td>
7969 </tr>
7970 <tr>
7971 <td>
7972                       <p>
7973                         ISDN
7974                       </p>
7975                     </td>
7976 <td>
7977                       <p>
7978                         Representation of ISDN addresses.
7979                         Experimental.  Described in RFC 1183.
7980                       </p>
7981                     </td>
7982 </tr>
7983 <tr>
7984 <td>
7985                       <p>
7986                         KEY
7987                       </p>
7988                     </td>
7989 <td>
7990                       <p>
7991                         Stores a public key associated with a
7992                         DNS name.  Used in original DNSSEC; replaced
7993                         by DNSKEY in DNSSECbis, but still used with
7994                         SIG(0).  Described in RFCs 2535 and 2931.
7995                       </p>
7996                     </td>
7997 </tr>
7998 <tr>
7999 <td>
8000                       <p>
8001                         KX
8002                       </p>
8003                     </td>
8004 <td>
8005                       <p>
8006                         Identifies a key exchanger for this
8007                         DNS name.  Described in RFC 2230.
8008                       </p>
8009                     </td>
8010 </tr>
8011 <tr>
8012 <td>
8013                       <p>
8014                         LOC
8015                       </p>
8016                     </td>
8017 <td>
8018                       <p>
8019                         For storing GPS info.  Described in RFC 1876.
8020                         Experimental.
8021                       </p>
8022                     </td>
8023 </tr>
8024 <tr>
8025 <td>
8026                       <p>
8027                         MX
8028                       </p>
8029                     </td>
8030 <td>
8031                       <p>
8032                         Identifies a mail exchange for the domain with
8033                         a 16-bit preference value (lower is better)
8034                         followed by the host name of the mail exchange.
8035                         Described in RFC 974, RFC 1035.
8036                       </p>
8037                     </td>
8038 </tr>
8039 <tr>
8040 <td>
8041                       <p>
8042                         NAPTR
8043                       </p>
8044                     </td>
8045 <td>
8046                       <p>
8047                         Name authority pointer.  Described in RFC 2915.
8048                       </p>
8049                     </td>
8050 </tr>
8051 <tr>
8052 <td>
8053                       <p>
8054                         NSAP
8055                       </p>
8056                     </td>
8057 <td>
8058                       <p>
8059                         A network service access point.
8060                         Described in RFC 1706.
8061                       </p>
8062                     </td>
8063 </tr>
8064 <tr>
8065 <td>
8066                       <p>
8067                         NS
8068                       </p>
8069                     </td>
8070 <td>
8071                       <p>
8072                         The authoritative name server for the
8073                         domain.  Described in RFC 1035.
8074                       </p>
8075                     </td>
8076 </tr>
8077 <tr>
8078 <td>
8079                       <p>
8080                         NSEC
8081                       </p>
8082                     </td>
8083 <td>
8084                       <p>
8085                         Used in DNSSECbis to securely indicate that
8086                         RRs with an owner name in a certain name interval do
8087                         not exist in
8088                         a zone and indicate what RR types are present for an
8089                         existing name.
8090                         Described in RFC 4034.
8091                       </p>
8092                     </td>
8093 </tr>
8094 <tr>
8095 <td>
8096                       <p>
8097                         NSEC3
8098                       </p>
8099                     </td>
8100 <td>
8101                       <p>
8102                         Used in DNSSECbis to securely indicate that
8103                         RRs with an owner name in a certain name
8104                         interval do not exist in a zone and indicate
8105                         what RR types are present for an existing
8106                         name.  NSEC3 differs from NSEC in that it
8107                         prevents zone enumeration but is more
8108                         computationally expensive on both the server
8109                         and the client than NSEC.  Described in RFC
8110                         5155.
8111                       </p>
8112                     </td>
8113 </tr>
8114 <tr>
8115 <td>
8116                       <p>
8117                         NSEC3PARAM
8118                       </p>
8119                     </td>
8120 <td>
8121                       <p>
8122                         Used in DNSSECbis to tell the authoritative
8123                         server which NSEC3 chains are available to use.
8124                         Described in RFC 5155.
8125                       </p>
8126                     </td>
8127 </tr>
8128 <tr>
8129 <td>
8130                       <p>
8131                         NXT
8132                       </p>
8133                     </td>
8134 <td>
8135                       <p>
8136                         Used in DNSSEC to securely indicate that
8137                         RRs with an owner name in a certain name interval do
8138                         not exist in
8139                         a zone and indicate what RR types are present for an
8140                         existing name.
8141                         Used in original DNSSEC; replaced by NSEC in
8142                         DNSSECbis.
8143                         Described in RFC 2535.
8144                       </p>
8145                     </td>
8146 </tr>
8147 <tr>
8148 <td>
8149                       <p>
8150                         PTR
8151                       </p>
8152                     </td>
8153 <td>
8154                       <p>
8155                         A pointer to another part of the domain
8156                         name space.  Described in RFC 1035.
8157                       </p>
8158                     </td>
8159 </tr>
8160 <tr>
8161 <td>
8162                       <p>
8163                         PX
8164                       </p>
8165                     </td>
8166 <td>
8167                       <p>
8168                         Provides mappings between RFC 822 and X.400
8169                         addresses.  Described in RFC 2163.
8170                       </p>
8171                     </td>
8172 </tr>
8173 <tr>
8174 <td>
8175                       <p>
8176                         RP
8177                       </p>
8178                     </td>
8179 <td>
8180                       <p>
8181                         Information on persons responsible
8182                         for the domain.  Experimental.  Described in RFC 1183.
8183                       </p>
8184                     </td>
8185 </tr>
8186 <tr>
8187 <td>
8188                       <p>
8189                         RRSIG
8190                       </p>
8191                     </td>
8192 <td>
8193                       <p>
8194                         Contains DNSSECbis signature data.  Described
8195                         in RFC 4034.
8196                       </p>
8197                     </td>
8198 </tr>
8199 <tr>
8200 <td>
8201                       <p>
8202                         RT
8203                       </p>
8204                     </td>
8205 <td>
8206                       <p>
8207                         Route-through binding for hosts that
8208                         do not have their own direct wide area network
8209                         addresses.
8210                         Experimental.  Described in RFC 1183.
8211                       </p>
8212                     </td>
8213 </tr>
8214 <tr>
8215 <td>
8216                       <p>
8217                         SIG
8218                       </p>
8219                     </td>
8220 <td>
8221                       <p>
8222                         Contains DNSSEC signature data.  Used in
8223                         original DNSSEC; replaced by RRSIG in
8224                         DNSSECbis, but still used for SIG(0).
8225                         Described in RFCs 2535 and 2931.
8226                       </p>
8227                     </td>
8228 </tr>
8229 <tr>
8230 <td>
8231                       <p>
8232                         SOA
8233                       </p>
8234                     </td>
8235 <td>
8236                       <p>
8237                         Identifies the start of a zone of authority.
8238                         Described in RFC 1035.
8239                       </p>
8240                     </td>
8241 </tr>
8242 <tr>
8243 <td>
8244                       <p>
8245                         SPF
8246                       </p>
8247                     </td>
8248 <td>
8249                       <p>
8250                         Contains the Sender Policy Framework information
8251                         for a given email domain.  Described in RFC 4408.
8252                       </p>
8253                     </td>
8254 </tr>
8255 <tr>
8256 <td>
8257                       <p>
8258                         SRV
8259                       </p>
8260                     </td>
8261 <td>
8262                       <p>
8263                         Information about well known network
8264                         services (replaces WKS).  Described in RFC 2782.
8265                       </p>
8266                     </td>
8267 </tr>
8268 <tr>
8269 <td>
8270                       <p>
8271                         SSHFP
8272                       </p>
8273                     </td>
8274 <td>
8275                       <p>
8276                         Provides a way to securely publish a secure shell key's
8277                         fingerprint.  Described in RFC 4255.
8278                       </p>
8279                     </td>
8280 </tr>
8281 <tr>
8282 <td>
8283                       <p>
8284                         TXT
8285                       </p>
8286                     </td>
8287 <td>
8288                       <p>
8289                         Text records.  Described in RFC 1035.
8290                       </p>
8291                     </td>
8292 </tr>
8293 <tr>
8294 <td>
8295                       <p>
8296                         WKS
8297                       </p>
8298                     </td>
8299 <td>
8300                       <p>
8301                         Information about which well known
8302                         network services, such as SMTP, that a domain
8303                         supports. Historical.
8304                       </p>
8305                     </td>
8306 </tr>
8307 <tr>
8308 <td>
8309                       <p>
8310                         X25
8311                       </p>
8312                     </td>
8313 <td>
8314                       <p>
8315                         Representation of X.25 network addresses.
8316                         Experimental.  Described in RFC 1183.
8317                       </p>
8318                     </td>
8319 </tr>
8320 </tbody>
8321 </table></div>
8322 <p>
8323               The following <span class="emphasis"><em>classes</em></span> of resource records
8324               are currently valid in the DNS:
8325             </p>
8326 <div class="informaltable"><table border="1">
8327 <colgroup>
8328 <col>
8329 <col>
8330 </colgroup>
8331 <tbody>
8332 <tr>
8333 <td>
8334                       <p>
8335                         IN
8336                       </p>
8337                     </td>
8338 <td>
8339                       <p>
8340                         The Internet.
8341                       </p>
8342                     </td>
8343 </tr>
8344 <tr>
8345 <td>
8346                       <p>
8347                         CH
8348                       </p>
8349                     </td>
8350 <td>
8351                       <p>
8352                         Chaosnet, a LAN protocol created at MIT in the
8353                         mid-1970s.
8354                         Rarely used for its historical purpose, but reused for
8355                         BIND's
8356                         built-in server information zones, e.g.,
8357                         <code class="literal">version.bind</code>.
8358                       </p>
8359                     </td>
8360 </tr>
8361 <tr>
8362 <td>
8363                       <p>
8364                         HS
8365                       </p>
8366                     </td>
8367 <td>
8368                       <p>
8369                         Hesiod, an information service
8370                         developed by MIT's Project Athena. It is used to share
8371                         information
8372                         about various systems databases, such as users,
8373                         groups, printers
8374                         and so on.
8375                       </p>
8376                     </td>
8377 </tr>
8378 </tbody>
8379 </table></div>
8380 <p>
8381               The owner name is often implicit, rather than forming an
8382               integral
8383               part of the RR.  For example, many name servers internally form
8384               tree
8385               or hash structures for the name space, and chain RRs off nodes.
8386               The remaining RR parts are the fixed header (type, class, TTL)
8387               which is consistent for all RRs, and a variable part (RDATA)
8388               that
8389               fits the needs of the resource being described.
8390             </p>
8391 <p>
8392               The meaning of the TTL field is a time limit on how long an
8393               RR can be kept in a cache.  This limit does not apply to
8394               authoritative
8395               data in zones; it is also timed out, but by the refreshing
8396               policies
8397               for the zone.  The TTL is assigned by the administrator for the
8398               zone where the data originates.  While short TTLs can be used to
8399               minimize caching, and a zero TTL prohibits caching, the
8400               realities
8401               of Internet performance suggest that these times should be on
8402               the
8403               order of days for the typical host.  If a change can be
8404               anticipated,
8405               the TTL can be reduced prior to the change to minimize
8406               inconsistency
8407               during the change, and then increased back to its former value
8408               following
8409               the change.
8410             </p>
8411 <p>
8412               The data in the RDATA section of RRs is carried as a combination
8413               of binary strings and domain names.  The domain names are
8414               frequently
8415               used as "pointers" to other data in the DNS.
8416             </p>
8417 </div>
8418 <div class="sect3" lang="en">
8419 <div class="titlepage"><div><div><h4 class="title">
8420 <a name="id2596826"></a>Textual expression of RRs</h4></div></div></div>
8421 <p>
8422               RRs are represented in binary form in the packets of the DNS
8423               protocol, and are usually represented in highly encoded form
8424               when
8425               stored in a name server or resolver.  In the examples provided
8426               in
8427               RFC 1034, a style similar to that used in master files was
8428               employed
8429               in order to show the contents of RRs.  In this format, most RRs
8430               are shown on a single line, although continuation lines are
8431               possible
8432               using parentheses.
8433             </p>
8434 <p>
8435               The start of the line gives the owner of the RR.  If a line
8436               begins with a blank, then the owner is assumed to be the same as
8437               that of the previous RR.  Blank lines are often included for
8438               readability.
8439             </p>
8440 <p>
8441               Following the owner, we list the TTL, type, and class of the
8442               RR.  Class and type use the mnemonics defined above, and TTL is
8443               an integer before the type field.  In order to avoid ambiguity
8444               in
8445               parsing, type and class mnemonics are disjoint, TTLs are
8446               integers,
8447               and the type mnemonic is always last. The IN class and TTL
8448               values
8449               are often omitted from examples in the interests of clarity.
8450             </p>
8451 <p>
8452               The resource data or RDATA section of the RR are given using
8453               knowledge of the typical representation for the data.
8454             </p>
8455 <p>
8456               For example, we might show the RRs carried in a message as:
8457             </p>
8458 <div class="informaltable"><table border="1">
8459 <colgroup>
8460 <col>
8461 <col>
8462 <col>
8463 </colgroup>
8464 <tbody>
8465 <tr>
8466 <td>
8467                       <p>
8468                         <code class="literal">ISI.EDU.</code>
8469                       </p>
8470                     </td>
8471 <td>
8472                       <p>
8473                         <code class="literal">MX</code>
8474                       </p>
8475                     </td>
8476 <td>
8477                       <p>
8478                         <code class="literal">10 VENERA.ISI.EDU.</code>
8479                       </p>
8480                     </td>
8481 </tr>
8482 <tr>
8483 <td>
8484                       <p></p>
8485                     </td>
8486 <td>
8487                       <p>
8488                         <code class="literal">MX</code>
8489                       </p>
8490                     </td>
8491 <td>
8492                       <p>
8493                         <code class="literal">10 VAXA.ISI.EDU</code>
8494                       </p>
8495                     </td>
8496 </tr>
8497 <tr>
8498 <td>
8499                       <p>
8500                         <code class="literal">VENERA.ISI.EDU</code>
8501                       </p>
8502                     </td>
8503 <td>
8504                       <p>
8505                         <code class="literal">A</code>
8506                       </p>
8507                     </td>
8508 <td>
8509                       <p>
8510                         <code class="literal">128.9.0.32</code>
8511                       </p>
8512                     </td>
8513 </tr>
8514 <tr>
8515 <td>
8516                       <p></p>
8517                     </td>
8518 <td>
8519                       <p>
8520                         <code class="literal">A</code>
8521                       </p>
8522                     </td>
8523 <td>
8524                       <p>
8525                         <code class="literal">10.1.0.52</code>
8526                       </p>
8527                     </td>
8528 </tr>
8529 <tr>
8530 <td>
8531                       <p>
8532                         <code class="literal">VAXA.ISI.EDU</code>
8533                       </p>
8534                     </td>
8535 <td>
8536                       <p>
8537                         <code class="literal">A</code>
8538                       </p>
8539                     </td>
8540 <td>
8541                       <p>
8542                         <code class="literal">10.2.0.27</code>
8543                       </p>
8544                     </td>
8545 </tr>
8546 <tr>
8547 <td>
8548                       <p></p>
8549                     </td>
8550 <td>
8551                       <p>
8552                         <code class="literal">A</code>
8553                       </p>
8554                     </td>
8555 <td>
8556                       <p>
8557                         <code class="literal">128.9.0.33</code>
8558                       </p>
8559                     </td>
8560 </tr>
8561 </tbody>
8562 </table></div>
8563 <p>
8564               The MX RRs have an RDATA section which consists of a 16-bit
8565               number followed by a domain name.  The address RRs use a
8566               standard
8567               IP address format to contain a 32-bit internet address.
8568             </p>
8569 <p>
8570               The above example shows six RRs, with two RRs at each of three
8571               domain names.
8572             </p>
8573 <p>
8574               Similarly we might see:
8575             </p>
8576 <div class="informaltable"><table border="1">
8577 <colgroup>
8578 <col>
8579 <col>
8580 <col>
8581 </colgroup>
8582 <tbody>
8583 <tr>
8584 <td>
8585                       <p>
8586                         <code class="literal">XX.LCS.MIT.EDU.</code>
8587                       </p>
8588                     </td>
8589 <td>
8590                       <p>
8591                         <code class="literal">IN A</code>
8592                       </p>
8593                     </td>
8594 <td>
8595                       <p>
8596                         <code class="literal">10.0.0.44</code>
8597                       </p>
8598                     </td>
8599 </tr>
8600 <tr>
8601 <td> </td>
8602 <td>
8603                       <p>
8604                         <code class="literal">CH A</code>
8605                       </p>
8606                     </td>
8607 <td>
8608                       <p>
8609                         <code class="literal">MIT.EDU. 2420</code>
8610                       </p>
8611                     </td>
8612 </tr>
8613 </tbody>
8614 </table></div>
8615 <p>
8616               This example shows two addresses for
8617               <code class="literal">XX.LCS.MIT.EDU</code>, each of a different class.
8618             </p>
8619 </div>
8620 </div>
8621 <div class="sect2" lang="en">
8622 <div class="titlepage"><div><div><h3 class="title">
8623 <a name="id2597415"></a>Discussion of MX Records</h3></div></div></div>
8624 <p>
8625             As described above, domain servers store information as a
8626             series of resource records, each of which contains a particular
8627             piece of information about a given domain name (which is usually,
8628             but not always, a host). The simplest way to think of a RR is as
8629             a typed pair of data, a domain name matched with a relevant datum,
8630             and stored with some additional type information to help systems
8631             determine when the RR is relevant.
8632           </p>
8633 <p>
8634             MX records are used to control delivery of email. The data
8635             specified in the record is a priority and a domain name. The
8636             priority
8637             controls the order in which email delivery is attempted, with the
8638             lowest number first. If two priorities are the same, a server is
8639             chosen randomly. If no servers at a given priority are responding,
8640             the mail transport agent will fall back to the next largest
8641             priority.
8642             Priority numbers do not have any absolute meaning &#8212; they are
8643             relevant
8644             only respective to other MX records for that domain name. The
8645             domain
8646             name given is the machine to which the mail will be delivered.
8647             It <span class="emphasis"><em>must</em></span> have an associated address record
8648             (A or AAAA) &#8212; CNAME is not sufficient.
8649           </p>
8650 <p>
8651             For a given domain, if there is both a CNAME record and an
8652             MX record, the MX record is in error, and will be ignored.
8653             Instead,
8654             the mail will be delivered to the server specified in the MX
8655             record
8656             pointed to by the CNAME.
8657             For example:
8658           </p>
8659 <div class="informaltable"><table border="1">
8660 <colgroup>
8661 <col>
8662 <col>
8663 <col>
8664 <col>
8665 <col>
8666 </colgroup>
8667 <tbody>
8668 <tr>
8669 <td>
8670                     <p>
8671                       <code class="literal">example.com.</code>
8672                     </p>
8673                   </td>
8674 <td>
8675                     <p>
8676                       <code class="literal">IN</code>
8677                     </p>
8678                   </td>
8679 <td>
8680                     <p>
8681                       <code class="literal">MX</code>
8682                     </p>
8683                   </td>
8684 <td>
8685                     <p>
8686                       <code class="literal">10</code>
8687                     </p>
8688                   </td>
8689 <td>
8690                     <p>
8691                       <code class="literal">mail.example.com.</code>
8692                     </p>
8693                   </td>
8694 </tr>
8695 <tr>
8696 <td>
8697                     <p></p>
8698                   </td>
8699 <td>
8700                     <p>
8701                       <code class="literal">IN</code>
8702                     </p>
8703                   </td>
8704 <td>
8705                     <p>
8706                       <code class="literal">MX</code>
8707                     </p>
8708                   </td>
8709 <td>
8710                     <p>
8711                       <code class="literal">10</code>
8712                     </p>
8713                   </td>
8714 <td>
8715                     <p>
8716                       <code class="literal">mail2.example.com.</code>
8717                     </p>
8718                   </td>
8719 </tr>
8720 <tr>
8721 <td>
8722                     <p></p>
8723                   </td>
8724 <td>
8725                     <p>
8726                       <code class="literal">IN</code>
8727                     </p>
8728                   </td>
8729 <td>
8730                     <p>
8731                       <code class="literal">MX</code>
8732                     </p>
8733                   </td>
8734 <td>
8735                     <p>
8736                       <code class="literal">20</code>
8737                     </p>
8738                   </td>
8739 <td>
8740                     <p>
8741                       <code class="literal">mail.backup.org.</code>
8742                     </p>
8743                   </td>
8744 </tr>
8745 <tr>
8746 <td>
8747                     <p>
8748                       <code class="literal">mail.example.com.</code>
8749                     </p>
8750                   </td>
8751 <td>
8752                     <p>
8753                       <code class="literal">IN</code>
8754                     </p>
8755                   </td>
8756 <td>
8757                     <p>
8758                       <code class="literal">A</code>
8759                     </p>
8760                   </td>
8761 <td>
8762                     <p>
8763                       <code class="literal">10.0.0.1</code>
8764                     </p>
8765                   </td>
8766 <td>
8767                     <p></p>
8768                   </td>
8769 </tr>
8770 <tr>
8771 <td>
8772                     <p>
8773                       <code class="literal">mail2.example.com.</code>
8774                     </p>
8775                   </td>
8776 <td>
8777                     <p>
8778                       <code class="literal">IN</code>
8779                     </p>
8780                   </td>
8781 <td>
8782                     <p>
8783                       <code class="literal">A</code>
8784                     </p>
8785                   </td>
8786 <td>
8787                     <p>
8788                       <code class="literal">10.0.0.2</code>
8789                     </p>
8790                   </td>
8791 <td>
8792                     <p></p>
8793                   </td>
8794 </tr>
8795 </tbody>
8796 </table></div>
8797 <p>
8798             Mail delivery will be attempted to <code class="literal">mail.example.com</code> and
8799             <code class="literal">mail2.example.com</code> (in
8800             any order), and if neither of those succeed, delivery to <code class="literal">mail.backup.org</code> will
8801             be attempted.
8802           </p>
8803 </div>
8804 <div class="sect2" lang="en">
8805 <div class="titlepage"><div><div><h3 class="title">
8806 <a name="Setting_TTLs"></a>Setting TTLs</h3></div></div></div>
8807 <p>
8808             The time-to-live of the RR field is a 32-bit integer represented
8809             in units of seconds, and is primarily used by resolvers when they
8810             cache RRs. The TTL describes how long a RR can be cached before it
8811             should be discarded. The following three types of TTL are
8812             currently
8813             used in a zone file.
8814           </p>
8815 <div class="informaltable"><table border="1">
8816 <colgroup>
8817 <col>
8818 <col>
8819 </colgroup>
8820 <tbody>
8821 <tr>
8822 <td>
8823                     <p>
8824                       SOA
8825                     </p>
8826                   </td>
8827 <td>
8828                     <p>
8829                       The last field in the SOA is the negative
8830                       caching TTL. This controls how long other servers will
8831                       cache no-such-domain
8832                       (NXDOMAIN) responses from you.
8833                     </p>
8834                     <p>
8835                       The maximum time for
8836                       negative caching is 3 hours (3h).
8837                     </p>
8838                   </td>
8839 </tr>
8840 <tr>
8841 <td>
8842                     <p>
8843                       $TTL
8844                     </p>
8845                   </td>
8846 <td>
8847                     <p>
8848                       The $TTL directive at the top of the
8849                       zone file (before the SOA) gives a default TTL for every
8850                       RR without
8851                       a specific TTL set.
8852                     </p>
8853                   </td>
8854 </tr>
8855 <tr>
8856 <td>
8857                     <p>
8858                       RR TTLs
8859                     </p>
8860                   </td>
8861 <td>
8862                     <p>
8863                       Each RR can have a TTL as the second
8864                       field in the RR, which will control how long other
8865                       servers can cache
8866                       the it.
8867                     </p>
8868                   </td>
8869 </tr>
8870 </tbody>
8871 </table></div>
8872 <p>
8873             All of these TTLs default to units of seconds, though units
8874             can be explicitly specified, for example, <code class="literal">1h30m</code>.
8875           </p>
8876 </div>
8877 <div class="sect2" lang="en">
8878 <div class="titlepage"><div><div><h3 class="title">
8879 <a name="id2597962"></a>Inverse Mapping in IPv4</h3></div></div></div>
8880 <p>
8881             Reverse name resolution (that is, translation from IP address
8882             to name) is achieved by means of the <span class="emphasis"><em>in-addr.arpa</em></span> domain
8883             and PTR records. Entries in the in-addr.arpa domain are made in
8884             least-to-most significant order, read left to right. This is the
8885             opposite order to the way IP addresses are usually written. Thus,
8886             a machine with an IP address of 10.1.2.3 would have a
8887             corresponding
8888             in-addr.arpa name of
8889             3.2.1.10.in-addr.arpa. This name should have a PTR resource record
8890             whose data field is the name of the machine or, optionally,
8891             multiple
8892             PTR records if the machine has more than one name. For example,
8893             in the [<span class="optional">example.com</span>] domain:
8894           </p>
8895 <div class="informaltable"><table border="1">
8896 <colgroup>
8897 <col>
8898 <col>
8899 </colgroup>
8900 <tbody>
8901 <tr>
8902 <td>
8903                     <p>
8904                       <code class="literal">$ORIGIN</code>
8905                     </p>
8906                   </td>
8907 <td>
8908                     <p>
8909                       <code class="literal">2.1.10.in-addr.arpa</code>
8910                     </p>
8911                   </td>
8912 </tr>
8913 <tr>
8914 <td>
8915                     <p>
8916                       <code class="literal">3</code>
8917                     </p>
8918                   </td>
8919 <td>
8920                     <p>
8921                       <code class="literal">IN PTR foo.example.com.</code>
8922                     </p>
8923                   </td>
8924 </tr>
8925 </tbody>
8926 </table></div>
8927 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
8928 <h3 class="title">Note</h3>
8929 <p>
8930               The <span><strong class="command">$ORIGIN</strong></span> lines in the examples
8931               are for providing context to the examples only &#8212; they do not
8932               necessarily
8933               appear in the actual usage. They are only used here to indicate
8934               that the example is relative to the listed origin.
8935             </p>
8936 </div>
8937 </div>
8938 <div class="sect2" lang="en">
8939 <div class="titlepage"><div><div><h3 class="title">
8940 <a name="id2598157"></a>Other Zone File Directives</h3></div></div></div>
8941 <p>
8942             The Master File Format was initially defined in RFC 1035 and
8943             has subsequently been extended. While the Master File Format
8944             itself
8945             is class independent all records in a Master File must be of the
8946             same
8947             class.
8948           </p>
8949 <p>
8950             Master File Directives include <span><strong class="command">$ORIGIN</strong></span>, <span><strong class="command">$INCLUDE</strong></span>,
8951             and <span><strong class="command">$TTL.</strong></span>
8952           </p>
8953 <div class="sect3" lang="en">
8954 <div class="titlepage"><div><div><h4 class="title">
8955 <a name="id2598180"></a>The <span><strong class="command">@</strong></span> (at-sign)</h4></div></div></div>
8956 <p>
8957               When used in the label (or name) field, the asperand or
8958               at-sign (@) symbol represents the current origin.
8959               At the start of the zone file, it is the
8960               &lt;<code class="varname">zone_name</code>&gt; (followed by
8961               trailing dot).
8962             </p>
8963 </div>
8964 <div class="sect3" lang="en">
8965 <div class="titlepage"><div><div><h4 class="title">
8966 <a name="id2598196"></a>The <span><strong class="command">$ORIGIN</strong></span> Directive</h4></div></div></div>
8967 <p>
8968               Syntax: <span><strong class="command">$ORIGIN</strong></span>
8969               <em class="replaceable"><code>domain-name</code></em>
8970               [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
8971             </p>
8972 <p><span><strong class="command">$ORIGIN</strong></span>
8973               sets the domain name that will be appended to any
8974               unqualified records. When a zone is first read in there
8975               is an implicit <span><strong class="command">$ORIGIN</strong></span>
8976               &lt;<code class="varname">zone_name</code>&gt;<span><strong class="command">.</strong></span>
8977               (followed by trailing dot).
8978               The current <span><strong class="command">$ORIGIN</strong></span> is appended to
8979               the domain specified in the <span><strong class="command">$ORIGIN</strong></span>
8980               argument if it is not absolute.
8981             </p>
8982 <pre class="programlisting">
8983 $ORIGIN example.com.
8984 WWW     CNAME   MAIN-SERVER
8985 </pre>
8986 <p>
8987               is equivalent to
8988             </p>
8989 <pre class="programlisting">
8990 WWW.EXAMPLE.COM. CNAME MAIN-SERVER.EXAMPLE.COM.
8991 </pre>
8992 </div>
8993 <div class="sect3" lang="en">
8994 <div class="titlepage"><div><div><h4 class="title">
8995 <a name="id2598325"></a>The <span><strong class="command">$INCLUDE</strong></span> Directive</h4></div></div></div>
8996 <p>
8997               Syntax: <span><strong class="command">$INCLUDE</strong></span>
8998               <em class="replaceable"><code>filename</code></em>
8999               [<span class="optional">
9000 <em class="replaceable"><code>origin</code></em> </span>]
9001               [<span class="optional"> <em class="replaceable"><code>comment</code></em> </span>]
9002             </p>
9003 <p>
9004               Read and process the file <code class="filename">filename</code> as
9005               if it were included into the file at this point.  If <span><strong class="command">origin</strong></span> is
9006               specified the file is processed with <span><strong class="command">$ORIGIN</strong></span> set
9007               to that value, otherwise the current <span><strong class="command">$ORIGIN</strong></span> is
9008               used.
9009             </p>
9010 <p>
9011               The origin and the current domain name
9012               revert to the values they had prior to the <span><strong class="command">$INCLUDE</strong></span> once
9013               the file has been read.
9014             </p>
9015 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
9016 <h3 class="title">Note</h3>
9017 <p>
9018                 RFC 1035 specifies that the current origin should be restored
9019                 after
9020                 an <span><strong class="command">$INCLUDE</strong></span>, but it is silent
9021                 on whether the current
9022                 domain name should also be restored.  BIND 9 restores both of
9023                 them.
9024                 This could be construed as a deviation from RFC 1035, a
9025                 feature, or both.
9026               </p>
9027 </div>
9028 </div>
9029 <div class="sect3" lang="en">
9030 <div class="titlepage"><div><div><h4 class="title">
9031 <a name="id2598394"></a>The <span><strong class="command">$TTL</strong></span> Directive</h4></div></div></div>
9032 <p>
9033               Syntax: <span><strong class="command">$TTL</strong></span>
9034               <em class="replaceable"><code>default-ttl</code></em>
9035               [<span class="optional">
9036 <em class="replaceable"><code>comment</code></em> </span>]
9037             </p>
9038 <p>
9039               Set the default Time To Live (TTL) for subsequent records
9040               with undefined TTLs. Valid TTLs are of the range 0-2147483647
9041               seconds.
9042             </p>
9043 <p><span><strong class="command">$TTL</strong></span>
9044                is defined in RFC 2308.
9045             </p>
9046 </div>
9047 </div>
9048 <div class="sect2" lang="en">
9049 <div class="titlepage"><div><div><h3 class="title">
9050 <a name="id2598430"></a><acronym class="acronym">BIND</acronym> Master File Extension: the  <span><strong class="command">$GENERATE</strong></span> Directive</h3></div></div></div>
9051 <p>
9052             Syntax: <span><strong class="command">$GENERATE</strong></span>
9053             <em class="replaceable"><code>range</code></em>
9054             <em class="replaceable"><code>lhs</code></em>
9055             [<span class="optional"><em class="replaceable"><code>ttl</code></em></span>]
9056             [<span class="optional"><em class="replaceable"><code>class</code></em></span>]
9057             <em class="replaceable"><code>type</code></em>
9058             <em class="replaceable"><code>rhs</code></em>
9059             [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
9060           </p>
9061 <p><span><strong class="command">$GENERATE</strong></span>
9062             is used to create a series of resource records that only
9063             differ from each other by an
9064             iterator. <span><strong class="command">$GENERATE</strong></span> can be used to
9065             easily generate the sets of records required to support
9066             sub /24 reverse delegations described in RFC 2317:
9067             Classless IN-ADDR.ARPA delegation.
9068           </p>
9069 <pre class="programlisting">$ORIGIN 0.0.192.IN-ADDR.ARPA.
9070 $GENERATE 1-2 @ NS SERVER$.EXAMPLE.
9071 $GENERATE 1-127 $ CNAME $.0</pre>
9072 <p>
9073             is equivalent to
9074           </p>
9075 <pre class="programlisting">0.0.0.192.IN-ADDR.ARPA. NS SERVER1.EXAMPLE.
9076 0.0.0.192.IN-ADDR.ARPA. NS SERVER2.EXAMPLE.
9077 1.0.0.192.IN-ADDR.ARPA. CNAME 1.0.0.0.192.IN-ADDR.ARPA.
9078 2.0.0.192.IN-ADDR.ARPA. CNAME 2.0.0.0.192.IN-ADDR.ARPA.
9079 ...
9080 127.0.0.192.IN-ADDR.ARPA. CNAME 127.0.0.0.192.IN-ADDR.ARPA.
9081 </pre>
9082 <p>
9083             Generate a set of A and MX records.  Note the MX's right hand
9084             side is a quoted string.  The quotes will be stripped when the
9085             right hand side is processed.
9086            </p>
9087 <pre class="programlisting">
9088 $ORIGIN EXAMPLE.
9089 $GENERATE 1-127 HOST-$ A 1.2.3.$
9090 $GENERATE 1-127 HOST-$ MX "0 ."</pre>
9091 <p>
9092             is equivalent to
9093           </p>
9094 <pre class="programlisting">HOST-1.EXAMPLE.   A  1.2.3.1
9095 HOST-1.EXAMPLE.   MX 0 .
9096 HOST-2.EXAMPLE.   A  1.2.3.2
9097 HOST-2.EXAMPLE.   MX 0 .
9098 HOST-3.EXAMPLE.   A  1.2.3.3
9099 HOST-3.EXAMPLE.   MX 0 .
9100 ...
9101 HOST-127.EXAMPLE. A  1.2.3.127
9102 HOST-127.EXAMPLE. MX 0 .
9103 </pre>
9104 <div class="informaltable"><table border="1">
9105 <colgroup>
9106 <col>
9107 <col>
9108 </colgroup>
9109 <tbody>
9110 <tr>
9111 <td>
9112                     <p><span><strong class="command">range</strong></span></p>
9113                   </td>
9114 <td>
9115                     <p>
9116                       This can be one of two forms: start-stop
9117                       or start-stop/step. If the first form is used, then step
9118                       is set to
9119                       1. All of start, stop and step must be positive.
9120                     </p>
9121                   </td>
9122 </tr>
9123 <tr>
9124 <td>
9125                     <p><span><strong class="command">lhs</strong></span></p>
9126                   </td>
9127 <td>
9128                     <p>This
9129                       describes the owner name of the resource records
9130                       to be created.  Any single <span><strong class="command">$</strong></span>
9131                       (dollar sign)
9132                       symbols within the <span><strong class="command">lhs</strong></span> string
9133                       are replaced by the iterator value.
9134
9135                       To get a $ in the output, you need to escape the
9136                       <span><strong class="command">$</strong></span> using a backslash
9137                       <span><strong class="command">\</strong></span>,
9138                       e.g. <span><strong class="command">\$</strong></span>. The
9139                       <span><strong class="command">$</strong></span> may optionally be followed
9140                       by modifiers which change the offset from the
9141                       iterator, field width and base.
9142
9143                       Modifiers are introduced by a
9144                       <span><strong class="command">{</strong></span> (left brace) immediately following the
9145                       <span><strong class="command">$</strong></span> as
9146                       <span><strong class="command">${offset[,width[,base]]}</strong></span>.
9147                       For example, <span><strong class="command">${-20,3,d}</strong></span>
9148                       subtracts 20 from the current value, prints the
9149                       result as a decimal in a zero-padded field of
9150                       width 3.
9151
9152                       Available output forms are decimal
9153                       (<span><strong class="command">d</strong></span>), octal
9154                       (<span><strong class="command">o</strong></span>), hexadecimal
9155                       (<span><strong class="command">x</strong></span> or <span><strong class="command">X</strong></span>
9156                       for uppercase) and nibble
9157                       (<span><strong class="command">n</strong></span> or <span><strong class="command">N</strong></span>\
9158                       for uppercase).  The default modifier is
9159                       <span><strong class="command">${0,0,d}</strong></span>.  If the
9160                       <span><strong class="command">lhs</strong></span> is not absolute, the
9161                       current <span><strong class="command">$ORIGIN</strong></span> is appended
9162                       to the name.
9163                     </p>
9164                     <p>
9165                       In nibble mode the value will be treated as
9166                       if it was a reversed hexadecimal string
9167                       with each hexadecimal digit as a separate
9168                       label.  The width field includes the label
9169                       separator.
9170                     </p>
9171                     <p>
9172                       For compatibility with earlier versions,
9173                       <span><strong class="command">$$</strong></span> is still recognized as
9174                       indicating a literal $ in the output.
9175                     </p>
9176                   </td>
9177 </tr>
9178 <tr>
9179 <td>
9180                     <p><span><strong class="command">ttl</strong></span></p>
9181                   </td>
9182 <td>
9183                     <p>
9184                       Specifies the time-to-live of the generated records. If
9185                       not specified this will be inherited using the
9186                       normal TTL inheritance rules.
9187                     </p>
9188                     <p><span><strong class="command">class</strong></span>
9189                       and <span><strong class="command">ttl</strong></span> can be
9190                       entered in either order.
9191                     </p>
9192                   </td>
9193 </tr>
9194 <tr>
9195 <td>
9196                     <p><span><strong class="command">class</strong></span></p>
9197                   </td>
9198 <td>
9199                     <p>
9200                       Specifies the class of the generated records.
9201                       This must match the zone class if it is
9202                       specified.
9203                     </p>
9204                     <p><span><strong class="command">class</strong></span>
9205                       and <span><strong class="command">ttl</strong></span> can be
9206                       entered in either order.
9207                     </p>
9208                   </td>
9209 </tr>
9210 <tr>
9211 <td>
9212                     <p><span><strong class="command">type</strong></span></p>
9213                   </td>
9214 <td>
9215                     <p>
9216                       Any valid type.
9217                     </p>
9218                   </td>
9219 </tr>
9220 <tr>
9221 <td>
9222                     <p><span><strong class="command">rhs</strong></span></p>
9223                   </td>
9224 <td>
9225                     <p>
9226                       <span><strong class="command">rhs</strong></span>, optionally, quoted string.
9227                     </p>
9228                   </td>
9229 </tr>
9230 </tbody>
9231 </table></div>
9232 <p>
9233             The <span><strong class="command">$GENERATE</strong></span> directive is a <acronym class="acronym">BIND</acronym> extension
9234             and not part of the standard zone file format.
9235           </p>
9236 <p>
9237             BIND 8 does not support the optional TTL and CLASS fields.
9238           </p>
9239 </div>
9240 <div class="sect2" lang="en">
9241 <div class="titlepage"><div><div><h3 class="title">
9242 <a name="zonefile_format"></a>Additional File Formats</h3></div></div></div>
9243 <p>
9244             In addition to the standard textual format, BIND 9
9245             supports the ability to read or dump to zone files in
9246             other formats.  The <code class="constant">raw</code> format is
9247             currently available as an additional format.  It is a
9248             binary format representing BIND 9's internal data
9249             structure directly, thereby remarkably improving the
9250             loading time.
9251           </p>
9252 <p>
9253             For a primary server, a zone file in the
9254             <code class="constant">raw</code> format is expected to be
9255             generated from a textual zone file by the
9256             <span><strong class="command">named-compilezone</strong></span> command.  For a
9257             secondary server or for a dynamic zone, it is automatically
9258             generated (if this format is specified by the
9259             <span><strong class="command">masterfile-format</strong></span> option) when
9260             <span><strong class="command">named</strong></span> dumps the zone contents after
9261             zone transfer or when applying prior updates.
9262           </p>
9263 <p>
9264             If a zone file in a binary format needs manual modification,
9265             it first must be converted to a textual form by the
9266             <span><strong class="command">named-compilezone</strong></span> command.  All
9267             necessary modification should go to the text file, which
9268             should then be converted to the binary form by the
9269             <span><strong class="command">named-compilezone</strong></span> command again.
9270           </p>
9271 <p>
9272              Although the <code class="constant">raw</code> format uses the
9273              network byte order and avoids architecture-dependent
9274              data alignment so that it is as much portable as
9275              possible, it is primarily expected to be used inside
9276              the same single system.  In order to export a zone
9277              file in the <code class="constant">raw</code> format or make a
9278              portable backup of the file, it is recommended to
9279              convert the file to the standard textual representation.
9280           </p>
9281 </div>
9282 </div>
9283 <div class="sect1" lang="en">
9284 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
9285 <a name="statistics"></a>BIND9 Statistics</h2></div></div></div>
9286 <p>
9287           <acronym class="acronym">BIND</acronym> 9 maintains lots of statistics
9288           information and provides several interfaces for users to
9289           get access to the statistics.
9290           The available statistics include all statistics counters
9291           that were available in <acronym class="acronym">BIND</acronym> 8 and
9292           are meaningful in <acronym class="acronym">BIND</acronym> 9,
9293           and other information that is considered useful.
9294         </p>
9295 <p>
9296           The statistics information is categorized into the following
9297           sections.
9298         </p>
9299 <div class="informaltable"><table border="1">
9300 <colgroup>
9301 <col>
9302 <col>
9303 </colgroup>
9304 <tbody>
9305 <tr>
9306 <td>
9307                   <p>Incoming Requests</p>
9308                 </td>
9309 <td>
9310                   <p>
9311                     The number of incoming DNS requests for each OPCODE.
9312                   </p>
9313                 </td>
9314 </tr>
9315 <tr>
9316 <td>
9317                   <p>Incoming Queries</p>
9318                 </td>
9319 <td>
9320                   <p>
9321                     The number of incoming queries for each RR type.
9322                   </p>
9323                 </td>
9324 </tr>
9325 <tr>
9326 <td>
9327                   <p>Outgoing Queries</p>
9328                 </td>
9329 <td>
9330                   <p>
9331                     The number of outgoing queries for each RR
9332                     type sent from the internal resolver.
9333                     Maintained per view.
9334                   </p>
9335                 </td>
9336 </tr>
9337 <tr>
9338 <td>
9339                   <p>Name Server Statistics</p>
9340                 </td>
9341 <td>
9342                   <p>
9343                     Statistics counters about incoming request processing.
9344                   </p>
9345                 </td>
9346 </tr>
9347 <tr>
9348 <td>
9349                   <p>Zone Maintenance Statistics</p>
9350                 </td>
9351 <td>
9352                   <p>
9353                     Statistics counters regarding zone maintenance
9354                     operations such as zone transfers.
9355                   </p>
9356                 </td>
9357 </tr>
9358 <tr>
9359 <td>
9360                   <p>Resolver Statistics</p>
9361                 </td>
9362 <td>
9363                   <p>
9364                     Statistics counters about name resolution
9365                     performed in the internal resolver.
9366                     Maintained per view.
9367                   </p>
9368                 </td>
9369 </tr>
9370 <tr>
9371 <td>
9372                   <p>Cache DB RRsets</p>
9373                 </td>
9374 <td>
9375                   <p>
9376                     The number of RRsets per RR type and nonexistent
9377                     names stored in the cache database.
9378                     If the exclamation mark (!) is printed for a RR
9379                     type, it means that particular type of RRset is
9380                     known to be nonexistent (this is also known as
9381                     "NXRRSET").
9382                     Maintained per view.
9383                   </p>
9384                 </td>
9385 </tr>
9386 <tr>
9387 <td>
9388                   <p>Socket I/O Statistics</p>
9389                 </td>
9390 <td>
9391                   <p>
9392                     Statistics counters about network related events.
9393                   </p>
9394                 </td>
9395 </tr>
9396 </tbody>
9397 </table></div>
9398 <p>
9399           A subset of Name Server Statistics is collected and shown
9400           per zone for which the server has the authority when
9401           <span><strong class="command">zone-statistics</strong></span> is set to
9402           <strong class="userinput"><code>yes</code></strong>.
9403           These statistics counters are shown with their zone and view
9404           names.
9405           In some cases the view names are omitted for the default view.
9406         </p>
9407 <p>
9408           There are currently two user interfaces to get access to the
9409           statistics.
9410           One is in the plain text format dumped to the file specified
9411           by the <span><strong class="command">statistics-file</strong></span> configuration option.
9412           The other is remotely accessible via a statistics channel
9413           when the <span><strong class="command">statistics-channels</strong></span> statement
9414           is specified in the configuration file
9415           (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>.)
9416         </p>
9417 <div class="sect3" lang="en">
9418 <div class="titlepage"><div><div><h4 class="title">
9419 <a name="statsfile"></a>The Statistics File</h4></div></div></div>
9420 <p>
9421             The text format statistics dump begins with a line, like:
9422           </p>
9423 <p>
9424             <span><strong class="command">+++ Statistics Dump +++ (973798949)</strong></span>
9425           </p>
9426 <p>
9427             The number in parentheses is a standard
9428             Unix-style timestamp, measured as seconds since January 1, 1970.
9429
9430             Following
9431             that line is a set of statistics information, which is categorized
9432             as described above.
9433             Each section begins with a line, like:
9434           </p>
9435 <p>
9436             <span><strong class="command">++ Name Server Statistics ++</strong></span>
9437           </p>
9438 <p>
9439             Each section consists of lines, each containing the statistics
9440             counter value followed by its textual description.
9441             See below for available counters.
9442             For brevity, counters that have a value of 0 are not shown
9443             in the statistics file.
9444           </p>
9445 <p>
9446             The statistics dump ends with the line where the
9447             number is identical to the number in the beginning line; for example:
9448           </p>
9449 <p>
9450             <span><strong class="command">--- Statistics Dump --- (973798949)</strong></span>
9451           </p>
9452 </div>
9453 <div class="sect2" lang="en">
9454 <div class="titlepage"><div><div><h3 class="title">
9455 <a name="statistics_counters"></a>Statistics Counters</h3></div></div></div>
9456 <p>
9457             The following tables summarize statistics counters that
9458             <acronym class="acronym">BIND</acronym> 9 provides.
9459             For each row of the tables, the leftmost column is the
9460             abbreviated symbol name of that counter.
9461             These symbols are shown in the statistics information
9462             accessed via an HTTP statistics channel.
9463             The rightmost column gives the description of the counter,
9464             which is also shown in the statistics file
9465             (but, in this document, possibly with slight modification
9466             for better readability).
9467             Additional notes may also be provided in this column.
9468             When a middle column exists between these two columns,
9469             it gives the corresponding counter name of the
9470             <acronym class="acronym">BIND</acronym> 8 statistics, if applicable.
9471           </p>
9472 <div class="sect3" lang="en">
9473 <div class="titlepage"><div><div><h4 class="title">
9474 <a name="id2599384"></a>Name Server Statistics Counters</h4></div></div></div>
9475 <div class="informaltable"><table border="1">
9476 <colgroup>
9477 <col>
9478 <col>
9479 <col>
9480 </colgroup>
9481 <tbody>
9482 <tr>
9483 <td>
9484                       <p>
9485                         <span class="emphasis"><em>Symbol</em></span>
9486                       </p>
9487                     </td>
9488 <td>
9489                       <p>
9490                         <span class="emphasis"><em>BIND8 Symbol</em></span>
9491                       </p>
9492                     </td>
9493 <td>
9494                       <p>
9495                         <span class="emphasis"><em>Description</em></span>
9496                       </p>
9497                     </td>
9498 </tr>
9499 <tr>
9500 <td>
9501                       <p><span><strong class="command">Requestv4</strong></span></p>
9502                     </td>
9503 <td>
9504                       <p><span><strong class="command">RQ</strong></span></p>
9505                     </td>
9506 <td>
9507                       <p>
9508                         IPv4 requests received.
9509                         Note: this also counts non query requests.
9510                       </p>
9511                     </td>
9512 </tr>
9513 <tr>
9514 <td>
9515                       <p><span><strong class="command">Requestv6</strong></span></p>
9516                     </td>
9517 <td>
9518                       <p><span><strong class="command">RQ</strong></span></p>
9519                     </td>
9520 <td>
9521                       <p>
9522                         IPv6 requests received.
9523                         Note: this also counts non query requests.
9524                       </p>
9525                     </td>
9526 </tr>
9527 <tr>
9528 <td>
9529                       <p><span><strong class="command">ReqEdns0</strong></span></p>
9530                     </td>
9531 <td>
9532                       <p><span><strong class="command"></strong></span></p>
9533                     </td>
9534 <td>
9535                       <p>
9536                         Requests with EDNS(0) received.
9537                       </p>
9538                     </td>
9539 </tr>
9540 <tr>
9541 <td>
9542                       <p><span><strong class="command">ReqBadEDNSVer</strong></span></p>
9543                     </td>
9544 <td>
9545                       <p><span><strong class="command"></strong></span></p>
9546                     </td>
9547 <td>
9548                       <p>
9549                         Requests with unsupported EDNS version received.
9550                       </p>
9551                     </td>
9552 </tr>
9553 <tr>
9554 <td>
9555                       <p><span><strong class="command">ReqTSIG</strong></span></p>
9556                     </td>
9557 <td>
9558                       <p><span><strong class="command"></strong></span></p>
9559                     </td>
9560 <td>
9561                       <p>
9562                         Requests with TSIG received.
9563                       </p>
9564                     </td>
9565 </tr>
9566 <tr>
9567 <td>
9568                       <p><span><strong class="command">ReqSIG0</strong></span></p>
9569                     </td>
9570 <td>
9571                       <p><span><strong class="command"></strong></span></p>
9572                     </td>
9573 <td>
9574                       <p>
9575                         Requests with SIG(0) received.
9576                       </p>
9577                     </td>
9578 </tr>
9579 <tr>
9580 <td>
9581                       <p><span><strong class="command">ReqBadSIG</strong></span></p>
9582                     </td>
9583 <td>
9584                       <p><span><strong class="command"></strong></span></p>
9585                     </td>
9586 <td>
9587                       <p>
9588                         Requests with invalid (TSIG or SIG(0)) signature.
9589                       </p>
9590                     </td>
9591 </tr>
9592 <tr>
9593 <td>
9594                       <p><span><strong class="command">ReqTCP</strong></span></p>
9595                     </td>
9596 <td>
9597                       <p><span><strong class="command">RTCP</strong></span></p>
9598                     </td>
9599 <td>
9600                       <p>
9601                         TCP requests received.
9602                       </p>
9603                     </td>
9604 </tr>
9605 <tr>
9606 <td>
9607                       <p><span><strong class="command">AuthQryRej</strong></span></p>
9608                     </td>
9609 <td>
9610                       <p><span><strong class="command">RUQ</strong></span></p>
9611                     </td>
9612 <td>
9613                       <p>
9614                         Authoritative (non recursive) queries rejected.
9615                       </p>
9616                     </td>
9617 </tr>
9618 <tr>
9619 <td>
9620                       <p><span><strong class="command">RecQryRej</strong></span></p>
9621                     </td>
9622 <td>
9623                       <p><span><strong class="command">RURQ</strong></span></p>
9624                     </td>
9625 <td>
9626                       <p>
9627                         Recursive queries rejected.
9628                       </p>
9629                     </td>
9630 </tr>
9631 <tr>
9632 <td>
9633                       <p><span><strong class="command">XfrRej</strong></span></p>
9634                     </td>
9635 <td>
9636                       <p><span><strong class="command">RUXFR</strong></span></p>
9637                     </td>
9638 <td>
9639                       <p>
9640                         Zone transfer requests rejected.
9641                       </p>
9642                     </td>
9643 </tr>
9644 <tr>
9645 <td>
9646                       <p><span><strong class="command">UpdateRej</strong></span></p>
9647                     </td>
9648 <td>
9649                       <p><span><strong class="command">RUUpd</strong></span></p>
9650                     </td>
9651 <td>
9652                       <p>
9653                         Dynamic update requests rejected.
9654                       </p>
9655                     </td>
9656 </tr>
9657 <tr>
9658 <td>
9659                       <p><span><strong class="command">Response</strong></span></p>
9660                     </td>
9661 <td>
9662                       <p><span><strong class="command">SAns</strong></span></p>
9663                     </td>
9664 <td>
9665                       <p>
9666                         Responses sent.
9667                       </p>
9668                     </td>
9669 </tr>
9670 <tr>
9671 <td>
9672                       <p><span><strong class="command">RespTruncated</strong></span></p>
9673                     </td>
9674 <td>
9675                       <p><span><strong class="command"></strong></span></p>
9676                     </td>
9677 <td>
9678                       <p>
9679                         Truncated responses sent.
9680                       </p>
9681                     </td>
9682 </tr>
9683 <tr>
9684 <td>
9685                       <p><span><strong class="command">RespEDNS0</strong></span></p>
9686                     </td>
9687 <td>
9688                       <p><span><strong class="command"></strong></span></p>
9689                     </td>
9690 <td>
9691                       <p>
9692                         Responses with EDNS(0) sent.
9693                       </p>
9694                     </td>
9695 </tr>
9696 <tr>
9697 <td>
9698                       <p><span><strong class="command">RespTSIG</strong></span></p>
9699                     </td>
9700 <td>
9701                       <p><span><strong class="command"></strong></span></p>
9702                     </td>
9703 <td>
9704                       <p>
9705                         Responses with TSIG sent.
9706                       </p>
9707                     </td>
9708 </tr>
9709 <tr>
9710 <td>
9711                       <p><span><strong class="command">RespSIG0</strong></span></p>
9712                     </td>
9713 <td>
9714                       <p><span><strong class="command"></strong></span></p>
9715                     </td>
9716 <td>
9717                       <p>
9718                         Responses with SIG(0) sent.
9719                       </p>
9720                     </td>
9721 </tr>
9722 <tr>
9723 <td>
9724                       <p><span><strong class="command">QrySuccess</strong></span></p>
9725                     </td>
9726 <td>
9727                       <p><span><strong class="command"></strong></span></p>
9728                     </td>
9729 <td>
9730                       <p>
9731                         Queries resulted in a successful answer.
9732                         This means the query which returns a NOERROR response
9733                         with at least one answer RR.
9734                         This corresponds to the
9735                         <span><strong class="command">success</strong></span> counter
9736                         of previous versions of
9737                         <acronym class="acronym">BIND</acronym> 9.
9738                       </p>
9739                     </td>
9740 </tr>
9741 <tr>
9742 <td>
9743                       <p><span><strong class="command">QryAuthAns</strong></span></p>
9744                     </td>
9745 <td>
9746                       <p><span><strong class="command"></strong></span></p>
9747                     </td>
9748 <td>
9749                       <p>
9750                         Queries resulted in authoritative answer.
9751                       </p>
9752                     </td>
9753 </tr>
9754 <tr>
9755 <td>
9756                       <p><span><strong class="command">QryNoauthAns</strong></span></p>
9757                     </td>
9758 <td>
9759                       <p><span><strong class="command">SNaAns</strong></span></p>
9760                     </td>
9761 <td>
9762                       <p>
9763                         Queries resulted in non authoritative answer.
9764                       </p>
9765                     </td>
9766 </tr>
9767 <tr>
9768 <td>
9769                       <p><span><strong class="command">QryReferral</strong></span></p>
9770                     </td>
9771 <td>
9772                       <p><span><strong class="command"></strong></span></p>
9773                     </td>
9774 <td>
9775                       <p>
9776                         Queries resulted in referral answer.
9777                         This corresponds to the
9778                         <span><strong class="command">referral</strong></span> counter
9779                         of previous versions of
9780                         <acronym class="acronym">BIND</acronym> 9.
9781                       </p>
9782                     </td>
9783 </tr>
9784 <tr>
9785 <td>
9786                       <p><span><strong class="command">QryNxrrset</strong></span></p>
9787                     </td>
9788 <td>
9789                       <p><span><strong class="command"></strong></span></p>
9790                     </td>
9791 <td>
9792                       <p>
9793                         Queries resulted in NOERROR responses with no data.
9794                         This corresponds to the
9795                         <span><strong class="command">nxrrset</strong></span> counter
9796                         of previous versions of
9797                         <acronym class="acronym">BIND</acronym> 9.
9798                       </p>
9799                     </td>
9800 </tr>
9801 <tr>
9802 <td>
9803                       <p><span><strong class="command">QrySERVFAIL</strong></span></p>
9804                     </td>
9805 <td>
9806                       <p><span><strong class="command">SFail</strong></span></p>
9807                     </td>
9808 <td>
9809                       <p>
9810                         Queries resulted in SERVFAIL.
9811                       </p>
9812                     </td>
9813 </tr>
9814 <tr>
9815 <td>
9816                       <p><span><strong class="command">QryFORMERR</strong></span></p>
9817                     </td>
9818 <td>
9819                       <p><span><strong class="command">SFErr</strong></span></p>
9820                     </td>
9821 <td>
9822                       <p>
9823                         Queries resulted in FORMERR.
9824                       </p>
9825                     </td>
9826 </tr>
9827 <tr>
9828 <td>
9829                       <p><span><strong class="command">QryNXDOMAIN</strong></span></p>
9830                     </td>
9831 <td>
9832                       <p><span><strong class="command">SNXD</strong></span></p>
9833                     </td>
9834 <td>
9835                       <p>
9836                         Queries resulted in NXDOMAIN.
9837                         This corresponds to the
9838                         <span><strong class="command">nxdomain</strong></span> counter
9839                         of previous versions of
9840                         <acronym class="acronym">BIND</acronym> 9.
9841                       </p>
9842                     </td>
9843 </tr>
9844 <tr>
9845 <td>
9846                       <p><span><strong class="command">QryRecursion</strong></span></p>
9847                     </td>
9848 <td>
9849                       <p><span><strong class="command">RFwdQ</strong></span></p>
9850                     </td>
9851 <td>
9852                       <p>
9853                         Queries which caused the server
9854                         to perform recursion in order to find the final answer.
9855                         This corresponds to the
9856                         <span><strong class="command">recursion</strong></span> counter
9857                         of previous versions of
9858                         <acronym class="acronym">BIND</acronym> 9.
9859                       </p>
9860                     </td>
9861 </tr>
9862 <tr>
9863 <td>
9864                       <p><span><strong class="command">QryDuplicate</strong></span></p>
9865                     </td>
9866 <td>
9867                       <p><span><strong class="command">RDupQ</strong></span></p>
9868                     </td>
9869 <td>
9870                       <p>
9871                         Queries which the server attempted to
9872                         recurse but discovered an existing query with the same
9873                         IP address, port, query ID, name, type and class
9874                         already being processed.
9875                         This corresponds to the
9876                         <span><strong class="command">duplicate</strong></span> counter
9877                         of previous versions of
9878                         <acronym class="acronym">BIND</acronym> 9.
9879                       </p>
9880                     </td>
9881 </tr>
9882 <tr>
9883 <td>
9884                       <p><span><strong class="command">QryDropped</strong></span></p>
9885                     </td>
9886 <td>
9887                       <p><span><strong class="command"></strong></span></p>
9888                     </td>
9889 <td>
9890                       <p>
9891                         Recursive queries for which the server
9892                         discovered an excessive number of existing
9893                         recursive queries for the same name, type and
9894                         class and were subsequently dropped.
9895                         This is the number of dropped queries due to
9896                         the reason explained with the
9897                         <span><strong class="command">clients-per-query</strong></span>
9898                         and
9899                         <span><strong class="command">max-clients-per-query</strong></span>
9900                         options
9901                         (see the description about
9902                         <a href="Bv9ARM.ch06.html#clients-per-query"><span><strong class="command">clients-per-query</strong></span></a>.)
9903                         This corresponds to the
9904                         <span><strong class="command">dropped</strong></span> counter
9905                         of previous versions of
9906                         <acronym class="acronym">BIND</acronym> 9.
9907                       </p>
9908                     </td>
9909 </tr>
9910 <tr>
9911 <td>
9912                       <p><span><strong class="command">QryFailure</strong></span></p>
9913                     </td>
9914 <td>
9915                       <p><span><strong class="command"></strong></span></p>
9916                     </td>
9917 <td>
9918                       <p>
9919                         Other query failures.
9920                         This corresponds to the
9921                         <span><strong class="command">failure</strong></span> counter
9922                         of previous versions of
9923                         <acronym class="acronym">BIND</acronym> 9.
9924                         Note: this counter is provided mainly for
9925                         backward compatibility with the previous versions.
9926                         Normally a more fine-grained counters such as
9927                         <span><strong class="command">AuthQryRej</strong></span> and
9928                         <span><strong class="command">RecQryRej</strong></span>
9929                         that would also fall into this counter are provided,
9930                         and so this counter would not be of much
9931                         interest in practice.
9932                       </p>
9933                     </td>
9934 </tr>
9935 <tr>
9936 <td>
9937                       <p><span><strong class="command">XfrReqDone</strong></span></p>
9938                     </td>
9939 <td>
9940                       <p><span><strong class="command"></strong></span></p>
9941                     </td>
9942 <td>
9943                       <p>
9944                         Requested zone transfers completed.
9945                       </p>
9946                     </td>
9947 </tr>
9948 <tr>
9949 <td>
9950                       <p><span><strong class="command">UpdateReqFwd</strong></span></p>
9951                     </td>
9952 <td>
9953                       <p><span><strong class="command"></strong></span></p>
9954                     </td>
9955 <td>
9956                       <p>
9957                         Update requests forwarded.
9958                       </p>
9959                     </td>
9960 </tr>
9961 <tr>
9962 <td>
9963                       <p><span><strong class="command">UpdateRespFwd</strong></span></p>
9964                     </td>
9965 <td>
9966                       <p><span><strong class="command"></strong></span></p>
9967                     </td>
9968 <td>
9969                       <p>
9970                         Update responses forwarded.
9971                       </p>
9972                     </td>
9973 </tr>
9974 <tr>
9975 <td>
9976                       <p><span><strong class="command">UpdateFwdFail</strong></span></p>
9977                     </td>
9978 <td>
9979                       <p><span><strong class="command"></strong></span></p>
9980                     </td>
9981 <td>
9982                       <p>
9983                         Dynamic update forward failed.
9984                       </p>
9985                     </td>
9986 </tr>
9987 <tr>
9988 <td>
9989                       <p><span><strong class="command">UpdateDone</strong></span></p>
9990                     </td>
9991 <td>
9992                       <p><span><strong class="command"></strong></span></p>
9993                     </td>
9994 <td>
9995                       <p>
9996                         Dynamic updates completed.
9997                       </p>
9998                     </td>
9999 </tr>
10000 <tr>
10001 <td>
10002                       <p><span><strong class="command">UpdateFail</strong></span></p>
10003                     </td>
10004 <td>
10005                       <p><span><strong class="command"></strong></span></p>
10006                     </td>
10007 <td>
10008                       <p>
10009                         Dynamic updates failed.
10010                       </p>
10011                     </td>
10012 </tr>
10013 <tr>
10014 <td>
10015                       <p><span><strong class="command">UpdateBadPrereq</strong></span></p>
10016                     </td>
10017 <td>
10018                       <p><span><strong class="command"></strong></span></p>
10019                     </td>
10020 <td>
10021                       <p>
10022                         Dynamic updates rejected due to prerequisite failure.
10023                       </p>
10024                     </td>
10025 </tr>
10026 </tbody>
10027 </table></div>
10028 </div>
10029 <div class="sect3" lang="en">
10030 <div class="titlepage"><div><div><h4 class="title">
10031 <a name="id2600857"></a>Zone Maintenance Statistics Counters</h4></div></div></div>
10032 <div class="informaltable"><table border="1">
10033 <colgroup>
10034 <col>
10035 <col>
10036 </colgroup>
10037 <tbody>
10038 <tr>
10039 <td>
10040                       <p>
10041                         <span class="emphasis"><em>Symbol</em></span>
10042                       </p>
10043                     </td>
10044 <td>
10045                       <p>
10046                         <span class="emphasis"><em>Description</em></span>
10047                       </p>
10048                     </td>
10049 </tr>
10050 <tr>
10051 <td>
10052                       <p><span><strong class="command">NotifyOutv4</strong></span></p>
10053                     </td>
10054 <td>
10055                       <p>
10056                         IPv4 notifies sent.
10057                       </p>
10058                     </td>
10059 </tr>
10060 <tr>
10061 <td>
10062                       <p><span><strong class="command">NotifyOutv6</strong></span></p>
10063                     </td>
10064 <td>
10065                       <p>
10066                         IPv6 notifies sent.
10067                       </p>
10068                     </td>
10069 </tr>
10070 <tr>
10071 <td>
10072                       <p><span><strong class="command">NotifyInv4</strong></span></p>
10073                     </td>
10074 <td>
10075                       <p>
10076                         IPv4 notifies received.
10077                       </p>
10078                     </td>
10079 </tr>
10080 <tr>
10081 <td>
10082                       <p><span><strong class="command">NotifyInv6</strong></span></p>
10083                     </td>
10084 <td>
10085                       <p>
10086                         IPv6 notifies received.
10087                       </p>
10088                     </td>
10089 </tr>
10090 <tr>
10091 <td>
10092                       <p><span><strong class="command">NotifyRej</strong></span></p>
10093                     </td>
10094 <td>
10095                       <p>
10096                         Incoming notifies rejected.
10097                       </p>
10098                     </td>
10099 </tr>
10100 <tr>
10101 <td>
10102                       <p><span><strong class="command">SOAOutv4</strong></span></p>
10103                     </td>
10104 <td>
10105                       <p>
10106                         IPv4 SOA queries sent.
10107                       </p>
10108                     </td>
10109 </tr>
10110 <tr>
10111 <td>
10112                       <p><span><strong class="command">SOAOutv6</strong></span></p>
10113                     </td>
10114 <td>
10115                       <p>
10116                         IPv6 SOA queries sent.
10117                       </p>
10118                     </td>
10119 </tr>
10120 <tr>
10121 <td>
10122                       <p><span><strong class="command">AXFRReqv4</strong></span></p>
10123                     </td>
10124 <td>
10125                       <p>
10126                         IPv4 AXFR requested.
10127                       </p>
10128                     </td>
10129 </tr>
10130 <tr>
10131 <td>
10132                       <p><span><strong class="command">AXFRReqv6</strong></span></p>
10133                     </td>
10134 <td>
10135                       <p>
10136                         IPv6 AXFR requested.
10137                       </p>
10138                     </td>
10139 </tr>
10140 <tr>
10141 <td>
10142                       <p><span><strong class="command">IXFRReqv4</strong></span></p>
10143                     </td>
10144 <td>
10145                       <p>
10146                         IPv4 IXFR requested.
10147                       </p>
10148                     </td>
10149 </tr>
10150 <tr>
10151 <td>
10152                       <p><span><strong class="command">IXFRReqv6</strong></span></p>
10153                     </td>
10154 <td>
10155                       <p>
10156                         IPv6 IXFR requested.
10157                       </p>
10158                     </td>
10159 </tr>
10160 <tr>
10161 <td>
10162                       <p><span><strong class="command">XfrSuccess</strong></span></p>
10163                     </td>
10164 <td>
10165                       <p>
10166                         Zone transfer requests succeeded.
10167                       </p>
10168                     </td>
10169 </tr>
10170 <tr>
10171 <td>
10172                       <p><span><strong class="command">XfrFail</strong></span></p>
10173                     </td>
10174 <td>
10175                       <p>
10176                         Zone transfer requests failed.
10177                       </p>
10178                     </td>
10179 </tr>
10180 </tbody>
10181 </table></div>
10182 </div>
10183 <div class="sect3" lang="en">
10184 <div class="titlepage"><div><div><h4 class="title">
10185 <a name="id2601308"></a>Resolver Statistics Counters</h4></div></div></div>
10186 <div class="informaltable"><table border="1">
10187 <colgroup>
10188 <col>
10189 <col>
10190 <col>
10191 </colgroup>
10192 <tbody>
10193 <tr>
10194 <td>
10195                       <p>
10196                         <span class="emphasis"><em>Symbol</em></span>
10197                       </p>
10198                     </td>
10199 <td>
10200                       <p>
10201                         <span class="emphasis"><em>BIND8 Symbol</em></span>
10202                       </p>
10203                     </td>
10204 <td>
10205                       <p>
10206                         <span class="emphasis"><em>Description</em></span>
10207                       </p>
10208                     </td>
10209 </tr>
10210 <tr>
10211 <td>
10212                       <p><span><strong class="command">Queryv4</strong></span></p>
10213                     </td>
10214 <td>
10215                       <p><span><strong class="command">SFwdQ</strong></span></p>
10216                     </td>
10217 <td>
10218                       <p>
10219                         IPv4 queries sent.
10220                       </p>
10221                     </td>
10222 </tr>
10223 <tr>
10224 <td>
10225                       <p><span><strong class="command">Queryv6</strong></span></p>
10226                     </td>
10227 <td>
10228                       <p><span><strong class="command">SFwdQ</strong></span></p>
10229                     </td>
10230 <td>
10231                       <p>
10232                         IPv6 queries sent.
10233                       </p>
10234                     </td>
10235 </tr>
10236 <tr>
10237 <td>
10238                       <p><span><strong class="command">Responsev4</strong></span></p>
10239                     </td>
10240 <td>
10241                       <p><span><strong class="command">RR</strong></span></p>
10242                     </td>
10243 <td>
10244                       <p>
10245                         IPv4 responses received.
10246                       </p>
10247                     </td>
10248 </tr>
10249 <tr>
10250 <td>
10251                       <p><span><strong class="command">Responsev6</strong></span></p>
10252                     </td>
10253 <td>
10254                       <p><span><strong class="command">RR</strong></span></p>
10255                     </td>
10256 <td>
10257                       <p>
10258                         IPv6 responses received.
10259                       </p>
10260                     </td>
10261 </tr>
10262 <tr>
10263 <td>
10264                       <p><span><strong class="command">NXDOMAIN</strong></span></p>
10265                     </td>
10266 <td>
10267                       <p><span><strong class="command">RNXD</strong></span></p>
10268                     </td>
10269 <td>
10270                       <p>
10271                         NXDOMAIN received.
10272                       </p>
10273                     </td>
10274 </tr>
10275 <tr>
10276 <td>
10277                       <p><span><strong class="command">SERVFAIL</strong></span></p>
10278                     </td>
10279 <td>
10280                       <p><span><strong class="command">RFail</strong></span></p>
10281                     </td>
10282 <td>
10283                       <p>
10284                         SERVFAIL received.
10285                       </p>
10286                     </td>
10287 </tr>
10288 <tr>
10289 <td>
10290                       <p><span><strong class="command">FORMERR</strong></span></p>
10291                     </td>
10292 <td>
10293                       <p><span><strong class="command">RFErr</strong></span></p>
10294                     </td>
10295 <td>
10296                       <p>
10297                         FORMERR received.
10298                       </p>
10299                     </td>
10300 </tr>
10301 <tr>
10302 <td>
10303                       <p><span><strong class="command">OtherError</strong></span></p>
10304                     </td>
10305 <td>
10306                       <p><span><strong class="command">RErr</strong></span></p>
10307                     </td>
10308 <td>
10309                       <p>
10310                         Other errors received.
10311                       </p>
10312                     </td>
10313 </tr>
10314 <tr>
10315 <td>
10316                       <p><span><strong class="command">EDNS0Fail</strong></span></p>
10317                                                  </td>
10318 <td>
10319                       <p><span><strong class="command"></strong></span></p>
10320                     </td>
10321 <td>
10322                       <p>
10323                         EDNS(0) query failures.
10324                       </p>
10325                     </td>
10326 </tr>
10327 <tr>
10328 <td>
10329                       <p><span><strong class="command">Mismatch</strong></span></p>
10330                     </td>
10331 <td>
10332                       <p><span><strong class="command">RDupR</strong></span></p>
10333                     </td>
10334 <td>
10335                       <p>
10336                         Mismatch responses received.
10337                         The DNS ID, response's source address,
10338                         and/or the response's source port does not
10339                         match what was expected.
10340                         (The port must be 53 or as defined by
10341                         the <span><strong class="command">port</strong></span> option.)
10342                         This may be an indication of a cache
10343                         poisoning attempt.
10344                       </p>
10345                     </td>
10346 </tr>
10347 <tr>
10348 <td>
10349                       <p><span><strong class="command">Truncated</strong></span></p>
10350                     </td>
10351 <td>
10352                       <p><span><strong class="command"></strong></span></p>
10353                     </td>
10354 <td>
10355                       <p>
10356                         Truncated responses received.
10357                       </p>
10358                     </td>
10359 </tr>
10360 <tr>
10361 <td>
10362                       <p><span><strong class="command">Lame</strong></span></p>
10363                     </td>
10364 <td>
10365                       <p><span><strong class="command">RLame</strong></span></p>
10366                     </td>
10367 <td>
10368                       <p>
10369                         Lame delegations received.
10370                       </p>
10371                     </td>
10372 </tr>
10373 <tr>
10374 <td>
10375                       <p><span><strong class="command">Retry</strong></span></p>
10376                     </td>
10377 <td>
10378                       <p><span><strong class="command">SDupQ</strong></span></p>
10379                     </td>
10380 <td>
10381                       <p>
10382                         Query retries performed.
10383                       </p>
10384                     </td>
10385 </tr>
10386 <tr>
10387 <td>
10388                       <p><span><strong class="command">QueryAbort</strong></span></p>
10389                     </td>
10390 <td>
10391                       <p><span><strong class="command"></strong></span></p>
10392                     </td>
10393 <td>
10394                       <p>
10395                         Queries aborted due to quota control.
10396                       </p>
10397                     </td>
10398 </tr>
10399 <tr>
10400 <td>
10401                       <p><span><strong class="command">QuerySockFail</strong></span></p>
10402                     </td>
10403 <td>
10404                       <p><span><strong class="command"></strong></span></p>
10405                     </td>
10406 <td>
10407                       <p>
10408                         Failures in opening query sockets.
10409                         One common reason for such failures is a
10410                         failure of opening a new socket due to a
10411                         limitation on file descriptors.
10412                       </p>
10413                     </td>
10414 </tr>
10415 <tr>
10416 <td>
10417                       <p><span><strong class="command">QueryTimeout</strong></span></p>
10418                     </td>
10419 <td>
10420                       <p><span><strong class="command"></strong></span></p>
10421                     </td>
10422 <td>
10423                       <p>
10424                         Query timeouts.
10425                       </p>
10426                     </td>
10427 </tr>
10428 <tr>
10429 <td>
10430                       <p><span><strong class="command">GlueFetchv4</strong></span></p>
10431                     </td>
10432 <td>
10433                       <p><span><strong class="command">SSysQ</strong></span></p>
10434                     </td>
10435 <td>
10436                       <p>
10437                         IPv4 NS address fetches invoked.
10438                       </p>
10439                     </td>
10440 </tr>
10441 <tr>
10442 <td>
10443                       <p><span><strong class="command">GlueFetchv6</strong></span></p>
10444                     </td>
10445 <td>
10446                       <p><span><strong class="command">SSysQ</strong></span></p>
10447                     </td>
10448 <td>
10449                       <p>
10450                         IPv6 NS address fetches invoked.
10451                       </p>
10452                     </td>
10453 </tr>
10454 <tr>
10455 <td>
10456                       <p><span><strong class="command">GlueFetchv4Fail</strong></span></p>
10457                     </td>
10458 <td>
10459                       <p><span><strong class="command"></strong></span></p>
10460                     </td>
10461 <td>
10462                       <p>
10463                         IPv4 NS address fetch failed.
10464                       </p>
10465                     </td>
10466 </tr>
10467 <tr>
10468 <td>
10469                       <p><span><strong class="command">GlueFetchv6Fail</strong></span></p>
10470                     </td>
10471 <td>
10472                       <p><span><strong class="command"></strong></span></p>
10473                     </td>
10474 <td>
10475                       <p>
10476                         IPv6 NS address fetch failed.
10477                       </p>
10478                     </td>
10479 </tr>
10480 <tr>
10481 <td>
10482                       <p><span><strong class="command">ValAttempt</strong></span></p>
10483                     </td>
10484 <td>
10485                       <p><span><strong class="command"></strong></span></p>
10486                     </td>
10487 <td>
10488                       <p>
10489                         DNSSEC validation attempted.
10490                       </p>
10491                     </td>
10492 </tr>
10493 <tr>
10494 <td>
10495                       <p><span><strong class="command">ValOk</strong></span></p>
10496                     </td>
10497 <td>
10498                       <p><span><strong class="command"></strong></span></p>
10499                     </td>
10500 <td>
10501                       <p>
10502                         DNSSEC validation succeeded.
10503                       </p>
10504                     </td>
10505 </tr>
10506 <tr>
10507 <td>
10508                       <p><span><strong class="command">ValNegOk</strong></span></p>
10509                     </td>
10510 <td>
10511                       <p><span><strong class="command"></strong></span></p>
10512                     </td>
10513 <td>
10514                       <p>
10515                         DNSSEC validation on negative information succeeded.
10516                       </p>
10517                     </td>
10518 </tr>
10519 <tr>
10520 <td>
10521                       <p><span><strong class="command">ValFail</strong></span></p>
10522                     </td>
10523 <td>
10524                       <p><span><strong class="command"></strong></span></p>
10525                     </td>
10526 <td>
10527                       <p>
10528                         DNSSEC validation failed.
10529                       </p>
10530                     </td>
10531 </tr>
10532 <tr>
10533 <td>
10534                       <p><span><strong class="command">QryRTTnn</strong></span></p>
10535                     </td>
10536 <td>
10537                       <p><span><strong class="command"></strong></span></p>
10538                     </td>
10539 <td>
10540                       <p>
10541                         Frequency table on round trip times (RTTs) of
10542                         queries.
10543                         Each <span><strong class="command">nn</strong></span> specifies the corresponding
10544                         frequency.
10545                         In the sequence of
10546                         <span><strong class="command">nn_1</strong></span>,
10547                         <span><strong class="command">nn_2</strong></span>,
10548                         ...,
10549                         <span><strong class="command">nn_m</strong></span>,
10550                         the value of <span><strong class="command">nn_i</strong></span> is the
10551                         number of queries whose RTTs are between
10552                         <span><strong class="command">nn_(i-1)</strong></span> (inclusive) and
10553                         <span><strong class="command">nn_i</strong></span> (exclusive) milliseconds.
10554                         For the sake of convenience we define
10555                         <span><strong class="command">nn_0</strong></span> to be 0.
10556                         The last entry should be represented as
10557                         <span><strong class="command">nn_m+</strong></span>, which means the
10558                         number of queries whose RTTs are equal to or over
10559                         <span><strong class="command">nn_m</strong></span> milliseconds.
10560                       </p>
10561                     </td>
10562 </tr>
10563 </tbody>
10564 </table></div>
10565 </div>
10566 <div class="sect3" lang="en">
10567 <div class="titlepage"><div><div><h4 class="title">
10568 <a name="id2602398"></a>Socket I/O Statistics Counters</h4></div></div></div>
10569 <p>
10570               Socket I/O statistics counters are defined per socket
10571               types, which are
10572               <span><strong class="command">UDP4</strong></span> (UDP/IPv4),
10573               <span><strong class="command">UDP6</strong></span> (UDP/IPv6),
10574               <span><strong class="command">TCP4</strong></span> (TCP/IPv4),
10575               <span><strong class="command">TCP6</strong></span> (TCP/IPv6),
10576               <span><strong class="command">Unix</strong></span> (Unix Domain), and
10577               <span><strong class="command">FDwatch</strong></span> (sockets opened outside the
10578               socket module).
10579               In the following table <span><strong class="command">&lt;TYPE&gt;</strong></span>
10580               represents a socket type.
10581               Not all counters are available for all socket types;
10582               exceptions are noted in the description field.
10583             </p>
10584 <div class="informaltable"><table border="1">
10585 <colgroup>
10586 <col>
10587 <col>
10588 </colgroup>
10589 <tbody>
10590 <tr>
10591 <td>
10592                       <p>
10593                         <span class="emphasis"><em>Symbol</em></span>
10594                       </p>
10595                     </td>
10596 <td>
10597                       <p>
10598                         <span class="emphasis"><em>Description</em></span>
10599                       </p>
10600                     </td>
10601 </tr>
10602 <tr>
10603 <td>
10604                       <p><span><strong class="command">&lt;TYPE&gt;Open</strong></span></p>
10605                     </td>
10606 <td>
10607                       <p>
10608                         Sockets opened successfully.
10609                         This counter is not applicable to the
10610                         <span><strong class="command">FDwatch</strong></span> type.
10611                       </p>
10612                     </td>
10613 </tr>
10614 <tr>
10615 <td>
10616                       <p><span><strong class="command">&lt;TYPE&gt;OpenFail</strong></span></p>
10617                     </td>
10618 <td>
10619                       <p>
10620                         Failures of opening sockets.
10621                         This counter is not applicable to the
10622                         <span><strong class="command">FDwatch</strong></span> type.
10623                       </p>
10624                     </td>
10625 </tr>
10626 <tr>
10627 <td>
10628                       <p><span><strong class="command">&lt;TYPE&gt;Close</strong></span></p>
10629                     </td>
10630 <td>
10631                       <p>
10632                         Sockets closed.
10633                       </p>
10634                     </td>
10635 </tr>
10636 <tr>
10637 <td>
10638                       <p><span><strong class="command">&lt;TYPE&gt;BindFail</strong></span></p>
10639                     </td>
10640 <td>
10641                       <p>
10642                         Failures of binding sockets.
10643                       </p>
10644                     </td>
10645 </tr>
10646 <tr>
10647 <td>
10648                       <p><span><strong class="command">&lt;TYPE&gt;ConnFail</strong></span></p>
10649                     </td>
10650 <td>
10651                       <p>
10652                         Failures of connecting sockets.
10653                       </p>
10654                     </td>
10655 </tr>
10656 <tr>
10657 <td>
10658                       <p><span><strong class="command">&lt;TYPE&gt;Conn</strong></span></p>
10659                     </td>
10660 <td>
10661                       <p>
10662                         Connections established successfully.
10663                       </p>
10664                     </td>
10665 </tr>
10666 <tr>
10667 <td>
10668                       <p><span><strong class="command">&lt;TYPE&gt;AcceptFail</strong></span></p>
10669                     </td>
10670 <td>
10671                       <p>
10672                         Failures of accepting incoming connection requests.
10673                         This counter is not applicable to the
10674                         <span><strong class="command">UDP</strong></span> and
10675                         <span><strong class="command">FDwatch</strong></span> types.
10676                       </p>
10677                     </td>
10678 </tr>
10679 <tr>
10680 <td>
10681                       <p><span><strong class="command">&lt;TYPE&gt;Accept</strong></span></p>
10682                     </td>
10683 <td>
10684                       <p>
10685                         Incoming connections successfully accepted.
10686                         This counter is not applicable to the
10687                         <span><strong class="command">UDP</strong></span> and
10688                         <span><strong class="command">FDwatch</strong></span> types.
10689                       </p>
10690                     </td>
10691 </tr>
10692 <tr>
10693 <td>
10694                       <p><span><strong class="command">&lt;TYPE&gt;SendErr</strong></span></p>
10695                     </td>
10696 <td>
10697                       <p>
10698                         Errors in socket send operations.
10699                         This counter corresponds
10700                         to <span><strong class="command">SErr</strong></span> counter of
10701                         <span><strong class="command">BIND</strong></span> 8.
10702                       </p>
10703                     </td>
10704 </tr>
10705 <tr>
10706 <td>
10707                       <p><span><strong class="command">&lt;TYPE&gt;RecvErr</strong></span></p>
10708                     </td>
10709 <td>
10710                       <p>
10711                         Errors in socket receive operations.
10712                         This includes errors of send operations on a
10713                         connected UDP socket notified by an ICMP error
10714                         message.
10715                       </p>
10716                     </td>
10717 </tr>
10718 </tbody>
10719 </table></div>
10720 </div>
10721 <div class="sect3" lang="en">
10722 <div class="titlepage"><div><div><h4 class="title">
10723 <a name="id2602840"></a>Compatibility with <span class="emphasis"><em>BIND</em></span> 8 Counters</h4></div></div></div>
10724 <p>
10725               Most statistics counters that were available
10726               in <span><strong class="command">BIND</strong></span> 8 are also supported in
10727               <span><strong class="command">BIND</strong></span> 9 as shown in the above tables.
10728               Here are notes about other counters that do not appear
10729               in these tables.
10730             </p>
10731 <div class="variablelist"><dl>
10732 <dt><span class="term"><span><strong class="command">RFwdR,SFwdR</strong></span></span></dt>
10733 <dd><p>
10734                     These counters are not supported
10735                     because <span><strong class="command">BIND</strong></span> 9 does not adopt
10736                     the notion of <span class="emphasis"><em>forwarding</em></span>
10737                     as <span><strong class="command">BIND</strong></span> 8 did.
10738                   </p></dd>
10739 <dt><span class="term"><span><strong class="command">RAXFR</strong></span></span></dt>
10740 <dd><p>
10741                     This counter is accessible in the Incoming Queries section.
10742                   </p></dd>
10743 <dt><span class="term"><span><strong class="command">RIQ</strong></span></span></dt>
10744 <dd><p>
10745                     This counter is accessible in the Incoming Requests section.
10746                   </p></dd>
10747 <dt><span class="term"><span><strong class="command">ROpts</strong></span></span></dt>
10748 <dd><p>
10749                     This counter is not supported
10750                     because <span><strong class="command">BIND</strong></span> 9 does not care
10751                     about IP options in the first place.
10752                   </p></dd>
10753 </dl></div>
10754 </div>
10755 </div>
10756 </div>
10757 </div>
10758 <div class="navfooter">
10759 <hr>
10760 <table width="100%" summary="Navigation footer">
10761 <tr>
10762 <td width="40%" align="left">
10763 <a accesskey="p" href="Bv9ARM.ch05.html">Prev</a> </td>
10764 <td width="20%" align="center"> </td>
10765 <td width="40%" align="right"> <a accesskey="n" href="Bv9ARM.ch07.html">Next</a>
10766 </td>
10767 </tr>
10768 <tr>
10769 <td width="40%" align="left" valign="top">Chapter 5. The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver </td>
10770 <td width="20%" align="center"><a accesskey="h" href="Bv9ARM.html">Home</a></td>
10771 <td width="40%" align="right" valign="top"> Chapter 7. <acronym class="acronym">BIND</acronym> 9 Security Considerations</td>
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