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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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  40 <hr>
  41 </div>
  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#id2573480">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#id2574092"><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#id2574282"><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#id2574711"><span><strong class="command">include</strong></span> Statement Grammar</a></span></dt>
  62 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574726"><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#id2574749"><span><strong class="command">key</strong></span> Statement Grammar</a></span></dt>
  65 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574771"><span><strong class="command">key</strong></span> Statement Definition and Usage</a></span></dt>
  66 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574930"><span><strong class="command">logging</strong></span> Statement Grammar</a></span></dt>
  67 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575056"><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#id2576406"><span><strong class="command">lwres</strong></span> Statement Grammar</a></span></dt>
  70 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2576480"><span><strong class="command">lwres</strong></span> Statement Definition and Usage</a></span></dt>
  71 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2576544"><span><strong class="command">masters</strong></span> Statement Grammar</a></span></dt>
  72 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2576587"><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#id2576602"><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#id2585361"><span><strong class="command">trusted-keys</strong></span> Statement Grammar</a></span></dt>
  81 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2585410"><span><strong class="command">trusted-keys</strong></span> Statement Definition
  82             and Usage</a></span></dt>
  83 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#view_statement_grammar"><span><strong class="command">view</strong></span> Statement Grammar</a></span></dt>
  84 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2585490"><span><strong class="command">view</strong></span> Statement Definition and Usage</a></span></dt>
  85 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#zone_statement_grammar"><span><strong class="command">zone</strong></span>
  86             Statement Grammar</a></span></dt>
  87 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2586798"><span><strong class="command">zone</strong></span> Statement Definition and Usage</a></span></dt>
  88 </dl></dd>
  89 <dt><span class="sect1"><a href="Bv9ARM.ch06.html#id2589080">Zone File</a></span></dt>
  90 <dd><dl>
  91 <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>
  92 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2591101">Discussion of MX Records</a></span></dt>
  93 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#Setting_TTLs">Setting TTLs</a></span></dt>
  94 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2591653">Inverse Mapping in IPv4</a></span></dt>
  95 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2591848">Other Zone File Directives</a></span></dt>
  96 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2592173"><acronym class="acronym">BIND</acronym> Master File Extension: the  <span><strong class="command">$GENERATE</strong></span> Directive</a></span></dt>
  97 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#zonefile_format">Additional File Formats</a></span></dt>
  98 </dl></dd>
  99 </dl>
 100 </div>
 101 <p>
 102       <acronym class="acronym">BIND</acronym> 9 configuration is broadly similar
 103       to <acronym class="acronym">BIND</acronym> 8; however, there are a few new
 104       areas
 105       of configuration, such as views. <acronym class="acronym">BIND</acronym>
 106       8 configuration files should work with few alterations in <acronym class="acronym">BIND</acronym>
 107       9, although more complex configurations should be reviewed to check
 108       if they can be more efficiently implemented using the new features
 109       found in <acronym class="acronym">BIND</acronym> 9.
 110     </p>
 111 <p>
 112       <acronym class="acronym">BIND</acronym> 4 configuration files can be
 113       converted to the new format
 114       using the shell script
 115       <code class="filename">contrib/named-bootconf/named-bootconf.sh</code>.
 116     </p>
 117 <div class="sect1" lang="en">
 118 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
 119 <a name="configuration_file_elements"></a>Configuration File Elements</h2></div></div></div>
 120 <p>
 121         Following is a list of elements used throughout the <acronym class="acronym">BIND</acronym> configuration
 122         file documentation:
 123       </p>
 124 <div class="informaltable"><table border="1">
 125 <colgroup>
 126 <col>
 127 <col>
 128 </colgroup>
 129 <tbody>
 130 <tr>
 131 <td>
 132                 <p>
 133                   <code class="varname">acl_name</code>
 134                 </p>
 135               </td>
 136 <td>
 137                 <p>
 138                   The name of an <code class="varname">address_match_list</code> as
 139                   defined by the <span><strong class="command">acl</strong></span> statement.
 140                 </p>
 141               </td>
 142 </tr>
 143 <tr>
 144 <td>
 145                 <p>
 146                   <code class="varname">address_match_list</code>
 147                 </p>
 148               </td>
 149 <td>
 150                 <p>
 151                   A list of one or more
 152                   <code class="varname">ip_addr</code>,
 153                   <code class="varname">ip_prefix</code>, <code class="varname">key_id</code>,
 154                   or <code class="varname">acl_name</code> elements, see
 155                   <a href="Bv9ARM.ch06.html#address_match_lists" title="Address Match Lists">the section called &#8220;Address Match Lists&#8221;</a>.
 156                 </p>
 157               </td>
 158 </tr>
 159 <tr>
 160 <td>
 161                 <p>
 162                   <code class="varname">masters_list</code>
 163                 </p>
 164               </td>
 165 <td>
 166                 <p>
 167                   A named list of one or more <code class="varname">ip_addr</code>
 168                   with optional <code class="varname">key_id</code> and/or
 169                   <code class="varname">ip_port</code>.
 170                   A <code class="varname">masters_list</code> may include other
 171                   <code class="varname">masters_lists</code>.
 172                 </p>
 173               </td>
 174 </tr>
 175 <tr>
 176 <td>
 177                 <p>
 178                   <code class="varname">domain_name</code>
 179                 </p>
 180               </td>
 181 <td>
 182                 <p>
 183                   A quoted string which will be used as
 184                   a DNS name, for example "<code class="literal">my.test.domain</code>".
 185                 </p>
 186               </td>
 187 </tr>
 188 <tr>
 189 <td>
 190                 <p>
 191                   <code class="varname">dotted_decimal</code>
 192                 </p>
 193               </td>
 194 <td>
 195                 <p>
 196                   One to four integers valued 0 through
 197                   255 separated by dots (`.'), such as <span><strong class="command">123</strong></span>,
 198                   <span><strong class="command">45.67</strong></span> or <span><strong class="command">89.123.45.67</strong></span>.
 199                 </p>
 200               </td>
 201 </tr>
 202 <tr>
 203 <td>
 204                 <p>
 205                   <code class="varname">ip4_addr</code>
 206                 </p>
 207               </td>
 208 <td>
 209                 <p>
 210                   An IPv4 address with exactly four elements
 211                   in <code class="varname">dotted_decimal</code> notation.
 212                 </p>
 213               </td>
 214 </tr>
 215 <tr>
 216 <td>
 217                 <p>
 218                   <code class="varname">ip6_addr</code>
 219                 </p>
 220               </td>
 221 <td>
 222                 <p>
 223                   An IPv6 address, such as <span><strong class="command">2001:db8::1234</strong></span>.
 224                   IPv6 scoped addresses that have ambiguity on their scope
 225                   zones must be
 226                   disambiguated by an appropriate zone ID with the percent
 227                   character
 228                   (`%') as delimiter.
 229                   It is strongly recommended to use string zone names rather
 230                   than
 231                   numeric identifiers, in order to be robust against system
 232                   configuration changes.
 233                   However, since there is no standard mapping for such names
 234                   and
 235                   identifier values, currently only interface names as link
 236                   identifiers
 237                   are supported, assuming one-to-one mapping between
 238                   interfaces and links.
 239                   For example, a link-local address <span><strong class="command">fe80::1</strong></span> on the
 240                   link attached to the interface <span><strong class="command">ne0</strong></span>
 241                   can be specified as <span><strong class="command">fe80::1%ne0</strong></span>.
 242                   Note that on most systems link-local addresses always have
 243                   the
 244                   ambiguity, and need to be disambiguated.
 245                 </p>
 246               </td>
 247 </tr>
 248 <tr>
 249 <td>
 250                 <p>
 251                   <code class="varname">ip_addr</code>
 252                 </p>
 253               </td>
 254 <td>
 255                 <p>
 256                   An <code class="varname">ip4_addr</code> or <code class="varname">ip6_addr</code>.
 257                 </p>
 258               </td>
 259 </tr>
 260 <tr>
 261 <td>
 262                 <p>
 263                   <code class="varname">ip_port</code>
 264                 </p>
 265               </td>
 266 <td>
 267                 <p>
 268                   An IP port <code class="varname">number</code>.
 269                   The <code class="varname">number</code> is limited to 0
 270                   through 65535, with values
 271                   below 1024 typically restricted to use by processes running
 272                   as root.
 273                   In some cases, an asterisk (`*') character can be used as a
 274                   placeholder to
 275                   select a random high-numbered port.
 276                 </p>
 277               </td>
 278 </tr>
 279 <tr>
 280 <td>
 281                 <p>
 282                   <code class="varname">ip_prefix</code>
 283                 </p>
 284               </td>
 285 <td>
 286                 <p>
 287                   An IP network specified as an <code class="varname">ip_addr</code>,
 288                   followed by a slash (`/') and then the number of bits in the
 289                   netmask.
 290                   Trailing zeros in a <code class="varname">ip_addr</code>
 291                   may omitted.
 292                   For example, <span><strong class="command">127/8</strong></span> is the
 293                   network <span><strong class="command">127.0.0.0</strong></span> with
 294                   netmask <span><strong class="command">255.0.0.0</strong></span> and <span><strong class="command">1.2.3.0/28</strong></span> is
 295                   network <span><strong class="command">1.2.3.0</strong></span> with netmask <span><strong class="command">255.255.255.240</strong></span>.
 296                 </p>
 297               </td>
 298 </tr>
 299 <tr>
 300 <td>
 301                 <p>
 302                   <code class="varname">key_id</code>
 303                 </p>
 304               </td>
 305 <td>
 306                 <p>
 307                   A <code class="varname">domain_name</code> representing
 308                   the name of a shared key, to be used for transaction
 309                   security.
 310                 </p>
 311               </td>
 312 </tr>
 313 <tr>
 314 <td>
 315                 <p>
 316                   <code class="varname">key_list</code>
 317                 </p>
 318               </td>
 319 <td>
 320                 <p>
 321                   A list of one or more
 322                   <code class="varname">key_id</code>s,
 323                   separated by semicolons and ending with a semicolon.
 324                 </p>
 325               </td>
 326 </tr>
 327 <tr>
 328 <td>
 329                 <p>
 330                   <code class="varname">number</code>
 331                 </p>
 332               </td>
 333 <td>
 334                 <p>
 335                   A non-negative 32-bit integer
 336                   (i.e., a number between 0 and 4294967295, inclusive).
 337                   Its acceptable value might further
 338                   be limited by the context in which it is used.
 339                 </p>
 340               </td>
 341 </tr>
 342 <tr>
 343 <td>
 344                 <p>
 345                   <code class="varname">path_name</code>
 346                 </p>
 347               </td>
 348 <td>
 349                 <p>
 350                   A quoted string which will be used as
 351                   a pathname, such as <code class="filename">zones/master/my.test.domain</code>.
 352                 </p>
 353               </td>
 354 </tr>
 355 <tr>
 356 <td>
 357                 <p>
 358                   <code class="varname">size_spec</code>
 359                 </p>
 360               </td>
 361 <td>
 362                 <p>
 363                   A number, the word <strong class="userinput"><code>unlimited</code></strong>,
 364                   or the word <strong class="userinput"><code>default</code></strong>.
 365                 </p>
 366                 <p>
 367                   An <code class="varname">unlimited</code> <code class="varname">size_spec</code> requests unlimited
 368                   use, or the maximum available amount. A <code class="varname">default size_spec</code> uses
 369                   the limit that was in force when the server was started.
 370                 </p>
 371                 <p>
 372                   A <code class="varname">number</code> can optionally be
 373                   followed by a scaling factor:
 374                   <strong class="userinput"><code>K</code></strong> or <strong class="userinput"><code>k</code></strong>
 375                   for kilobytes,
 376                   <strong class="userinput"><code>M</code></strong> or <strong class="userinput"><code>m</code></strong>
 377                   for megabytes, and
 378                   <strong class="userinput"><code>G</code></strong> or <strong class="userinput"><code>g</code></strong> for gigabytes,
 379                   which scale by 1024, 1024*1024, and 1024*1024*1024
 380                   respectively.
 381                 </p>
 382                 <p>
 383                   The value must be representable as a 64-bit unsigned integer
 384                   (0 to 18446744073709551615, inclusive).
 385                   Using <code class="varname">unlimited</code> is the best
 386                   way
 387                   to safely set a really large number.
 388                 </p>
 389               </td>
 390 </tr>
 391 <tr>
 392 <td>
 393                 <p>
 394                   <code class="varname">yes_or_no</code>
 395                 </p>
 396               </td>
 397 <td>
 398                 <p>
 399                   Either <strong class="userinput"><code>yes</code></strong> or <strong class="userinput"><code>no</code></strong>.
 400                   The words <strong class="userinput"><code>true</code></strong> and <strong class="userinput"><code>false</code></strong> are
 401                   also accepted, as are the numbers <strong class="userinput"><code>1</code></strong>
 402                   and <strong class="userinput"><code>0</code></strong>.
 403                 </p>
 404               </td>
 405 </tr>
 406 <tr>
 407 <td>
 408                 <p>
 409                   <code class="varname">dialup_option</code>
 410                 </p>
 411               </td>
 412 <td>
 413                 <p>
 414                   One of <strong class="userinput"><code>yes</code></strong>,
 415                   <strong class="userinput"><code>no</code></strong>, <strong class="userinput"><code>notify</code></strong>,
 416                   <strong class="userinput"><code>notify-passive</code></strong>, <strong class="userinput"><code>refresh</code></strong> or
 417                   <strong class="userinput"><code>passive</code></strong>.
 418                   When used in a zone, <strong class="userinput"><code>notify-passive</code></strong>,
 419                   <strong class="userinput"><code>refresh</code></strong>, and <strong class="userinput"><code>passive</code></strong>
 420                   are restricted to slave and stub zones.
 421                 </p>
 422               </td>
 423 </tr>
 424 </tbody>
 425 </table></div>
 426 <div class="sect2" lang="en">
 427 <div class="titlepage"><div><div><h3 class="title">
 428 <a name="address_match_lists"></a>Address Match Lists</h3></div></div></div>
 429 <div class="sect3" lang="en">
 430 <div class="titlepage"><div><div><h4 class="title">
 431 <a name="id2573277"></a>Syntax</h4></div></div></div>
 432 <pre class="programlisting"><code class="varname">address_match_list</code> = address_match_list_element ;
 433   [<span class="optional"> address_match_list_element; ... </span>]
 434 <code class="varname">address_match_list_element</code> = [<span class="optional"> ! </span>] (ip_address [<span class="optional">/length</span>] |
 435    key key_id | acl_name | { address_match_list } )
 436 </pre>
 437 </div>
 438 <div class="sect3" lang="en">
 439 <div class="titlepage"><div><div><h4 class="title">
 440 <a name="id2573305"></a>Definition and Usage</h4></div></div></div>
 441 <p>
 442             Address match lists are primarily used to determine access
 443             control for various server operations. They are also used in
 444             the <span><strong class="command">listen-on</strong></span> and <span><strong class="command">sortlist</strong></span>
 445             statements. The elements
 446             which constitute an address match list can be any of the
 447             following:
 448           </p>
 449 <div class="itemizedlist"><ul type="disc">
 450 <li>an IP address (IPv4 or IPv6)</li>
 451 <li>an IP prefix (in `/' notation)</li>
 452 <li>
 453                 a key ID, as defined by the <span><strong class="command">key</strong></span>
 454                 statement
 455               </li>
 456 <li>the name of an address match list defined with
 457                 the <span><strong class="command">acl</strong></span> statement
 458               </li>
 459 <li>a nested address match list enclosed in braces</li>
 460 </ul></div>
 461 <p>
 462             Elements can be negated with a leading exclamation mark (`!'),
 463             and the match list names "any", "none", "localhost", and
 464             "localnets"
 465             are predefined. More information on those names can be found in
 466             the description of the acl statement.
 467           </p>
 468 <p>
 469             The addition of the key clause made the name of this syntactic
 470             element something of a misnomer, since security keys can be used
 471             to validate access without regard to a host or network address.
 472             Nonetheless,
 473             the term "address match list" is still used throughout the
 474             documentation.
 475           </p>
 476 <p>
 477             When a given IP address or prefix is compared to an address
 478             match list, the list is traversed in order until an element
 479             matches.
 480             The interpretation of a match depends on whether the list is being
 481             used
 482             for access control, defining listen-on ports, or in a sortlist,
 483             and whether the element was negated.
 484           </p>
 485 <p>
 486             When used as an access control list, a non-negated match
 487             allows access and a negated match denies access. If
 488             there is no match, access is denied. The clauses
 489             <span><strong class="command">allow-notify</strong></span>,
 490             <span><strong class="command">allow-query</strong></span>,
 491             <span><strong class="command">allow-query-cache</strong></span>,
 492             <span><strong class="command">allow-transfer</strong></span>,
 493             <span><strong class="command">allow-update</strong></span>,
 494             <span><strong class="command">allow-update-forwarding</strong></span>, and
 495             <span><strong class="command">blackhole</strong></span> all use address match
 496             lists.  Similarly, the listen-on option will cause the
 497             server to not accept queries on any of the machine's
 498             addresses which do not match the list.
 499           </p>
 500 <p>
 501             Because of the first-match aspect of the algorithm, an element
 502             that defines a subset of another element in the list should come
 503             before the broader element, regardless of whether either is
 504             negated. For
 505             example, in
 506             <span><strong class="command">1.2.3/24; ! 1.2.3.13;</strong></span> the 1.2.3.13
 507             element is
 508             completely useless because the algorithm will match any lookup for
 509             1.2.3.13 to the 1.2.3/24 element.
 510             Using <span><strong class="command">! 1.2.3.13; 1.2.3/24</strong></span> fixes
 511             that problem by having 1.2.3.13 blocked by the negation but all
 512             other 1.2.3.* hosts fall through.
 513           </p>
 514 </div>
 515 </div>
 516 <div class="sect2" lang="en">
 517 <div class="titlepage"><div><div><h3 class="title">
 518 <a name="id2573480"></a>Comment Syntax</h3></div></div></div>
 519 <p>
 520           The <acronym class="acronym">BIND</acronym> 9 comment syntax allows for
 521           comments to appear
 522           anywhere that whitespace may appear in a <acronym class="acronym">BIND</acronym> configuration
 523           file. To appeal to programmers of all kinds, they can be written
 524           in the C, C++, or shell/perl style.
 525         </p>
 526 <div class="sect3" lang="en">
 527 <div class="titlepage"><div><div><h4 class="title">
 528 <a name="id2573495"></a>Syntax</h4></div></div></div>
 529 <p>
 530             </p>
 531 <pre class="programlisting">/* This is a <acronym class="acronym">BIND</acronym> comment as in C */</pre>
 532 <p>
 533             </p>
 534 <pre class="programlisting">// This is a <acronym class="acronym">BIND</acronym> comment as in C++</pre>
 535 <p>
 536             </p>
 537 <pre class="programlisting"># This is a <acronym class="acronym">BIND</acronym> comment as in common UNIX shells and perl</pre>
 538 <p>
 539           </p>
 540 </div>
 541 <div class="sect3" lang="en">
 542 <div class="titlepage"><div><div><h4 class="title">
 543 <a name="id2573525"></a>Definition and Usage</h4></div></div></div>
 544 <p>
 545             Comments may appear anywhere that whitespace may appear in
 546             a <acronym class="acronym">BIND</acronym> configuration file.
 547           </p>
 548 <p>
 549             C-style comments start with the two characters /* (slash,
 550             star) and end with */ (star, slash). Because they are completely
 551             delimited with these characters, they can be used to comment only
 552             a portion of a line or to span multiple lines.
 553           </p>
 554 <p>
 555             C-style comments cannot be nested. For example, the following
 556             is not valid because the entire comment ends with the first */:
 557           </p>
 558 <p>
 559
 560 </p>
 561 <pre class="programlisting">/* This is the start of a comment.
 562    This is still part of the comment.
 563 /* This is an incorrect attempt at nesting a comment. */
 564    This is no longer in any comment. */
 565 </pre>
 566 <p>
 567
 568           </p>
 569 <p>
 570             C++-style comments start with the two characters // (slash,
 571             slash) and continue to the end of the physical line. They cannot
 572             be continued across multiple physical lines; to have one logical
 573             comment span multiple lines, each line must use the // pair.
 574           </p>
 575 <p>
 576             For example:
 577           </p>
 578 <p>
 579
 580 </p>
 581 <pre class="programlisting">// This is the start of a comment.  The next line
 582 // is a new comment, even though it is logically
 583 // part of the previous comment.
 584 </pre>
 585 <p>
 586
 587           </p>
 588 <p>
 589             Shell-style (or perl-style, if you prefer) comments start
 590             with the character <code class="literal">#</code> (number sign)
 591             and continue to the end of the
 592             physical line, as in C++ comments.
 593           </p>
 594 <p>
 595             For example:
 596           </p>
 597 <p>
 598
 599 </p>
 600 <pre class="programlisting"># This is the start of a comment.  The next line
 601 # is a new comment, even though it is logically
 602 # part of the previous comment.
 603 </pre>
 604 <p>
 605
 606           </p>
 607 <div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
 608 <h3 class="title">Warning</h3>
 609 <p>
 610               You cannot use the semicolon (`;') character
 611               to start a comment such as you would in a zone file. The
 612               semicolon indicates the end of a configuration
 613               statement.
 614             </p>
 615 </div>
 616 </div>
 617 </div>
 618 </div>
 619 <div class="sect1" lang="en">
 620 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
 621 <a name="Configuration_File_Grammar"></a>Configuration File Grammar</h2></div></div></div>
 622 <p>
 623         A <acronym class="acronym">BIND</acronym> 9 configuration consists of
 624         statements and comments.
 625         Statements end with a semicolon. Statements and comments are the
 626         only elements that can appear without enclosing braces. Many
 627         statements contain a block of sub-statements, which are also
 628         terminated with a semicolon.
 629       </p>
 630 <p>
 631         The following statements are supported:
 632       </p>
 633 <div class="informaltable"><table border="1">
 634 <colgroup>
 635 <col>
 636 <col>
 637 </colgroup>
 638 <tbody>
 639 <tr>
 640 <td>
 641                 <p><span><strong class="command">acl</strong></span></p>
 642               </td>
 643 <td>
 644                 <p>
 645                   defines a named IP address
 646                   matching list, for access control and other uses.
 647                 </p>
 648               </td>
 649 </tr>
 650 <tr>
 651 <td>
 652                 <p><span><strong class="command">controls</strong></span></p>
 653               </td>
 654 <td>
 655                 <p>
 656                   declares control channels to be used
 657                   by the <span><strong class="command">rndc</strong></span> utility.
 658                 </p>
 659               </td>
 660 </tr>
 661 <tr>
 662 <td>
 663                 <p><span><strong class="command">include</strong></span></p>
 664               </td>
 665 <td>
 666                 <p>
 667                   includes a file.
 668                 </p>
 669               </td>
 670 </tr>
 671 <tr>
 672 <td>
 673                 <p><span><strong class="command">key</strong></span></p>
 674               </td>
 675 <td>
 676                 <p>
 677                   specifies key information for use in
 678                   authentication and authorization using TSIG.
 679                 </p>
 680               </td>
 681 </tr>
 682 <tr>
 683 <td>
 684                 <p><span><strong class="command">logging</strong></span></p>
 685               </td>
 686 <td>
 687                 <p>
 688                   specifies what the server logs, and where
 689                   the log messages are sent.
 690                 </p>
 691               </td>
 692 </tr>
 693 <tr>
 694 <td>
 695                 <p><span><strong class="command">lwres</strong></span></p>
 696               </td>
 697 <td>
 698                 <p>
 699                   configures <span><strong class="command">named</strong></span> to
 700                   also act as a light-weight resolver daemon (<span><strong class="command">lwresd</strong></span>).
 701                 </p>
 702               </td>
 703 </tr>
 704 <tr>
 705 <td>
 706                 <p><span><strong class="command">masters</strong></span></p>
 707               </td>
 708 <td>
 709                 <p>
 710                   defines a named masters list for
 711                   inclusion in stub and slave zone masters clauses.
 712                 </p>
 713               </td>
 714 </tr>
 715 <tr>
 716 <td>
 717                 <p><span><strong class="command">options</strong></span></p>
 718               </td>
 719 <td>
 720                 <p>
 721                   controls global server configuration
 722                   options and sets defaults for other statements.
 723                 </p>
 724               </td>
 725 </tr>
 726 <tr>
 727 <td>
 728                 <p><span><strong class="command">server</strong></span></p>
 729               </td>
 730 <td>
 731                 <p>
 732                   sets certain configuration options on
 733                   a per-server basis.
 734                 </p>
 735               </td>
 736 </tr>
 737 <tr>
 738 <td>
 739                 <p><span><strong class="command">trusted-keys</strong></span></p>
 740               </td>
 741 <td>
 742                 <p>
 743                   defines trusted DNSSEC keys.
 744                 </p>
 745               </td>
 746 </tr>
 747 <tr>
 748 <td>
 749                 <p><span><strong class="command">view</strong></span></p>
 750               </td>
 751 <td>
 752                 <p>
 753                   defines a view.
 754                 </p>
 755               </td>
 756 </tr>
 757 <tr>
 758 <td>
 759                 <p><span><strong class="command">zone</strong></span></p>
 760               </td>
 761 <td>
 762                 <p>
 763                   defines a zone.
 764                 </p>
 765               </td>
 766 </tr>
 767 </tbody>
 768 </table></div>
 769 <p>
 770         The <span><strong class="command">logging</strong></span> and
 771         <span><strong class="command">options</strong></span> statements may only occur once
 772         per
 773         configuration.
 774       </p>
 775 <div class="sect2" lang="en">
 776 <div class="titlepage"><div><div><h3 class="title">
 777 <a name="id2574092"></a><span><strong class="command">acl</strong></span> Statement Grammar</h3></div></div></div>
 778 <pre class="programlisting"><span><strong class="command">acl</strong></span> acl-name {
 779     address_match_list
 780 };
 781 </pre>
 782 </div>
 783 <div class="sect2" lang="en">
 784 <div class="titlepage"><div><div><h3 class="title">
 785 <a name="acl"></a><span><strong class="command">acl</strong></span> Statement Definition and
 786           Usage</h3></div></div></div>
 787 <p>
 788           The <span><strong class="command">acl</strong></span> statement assigns a symbolic
 789           name to an address match list. It gets its name from a primary
 790           use of address match lists: Access Control Lists (ACLs).
 791         </p>
 792 <p>
 793           Note that an address match list's name must be defined
 794           with <span><strong class="command">acl</strong></span> before it can be used
 795           elsewhere; no
 796           forward references are allowed.
 797         </p>
 798 <p>
 799           The following ACLs are built-in:
 800         </p>
 801 <div class="informaltable"><table border="1">
 802 <colgroup>
 803 <col>
 804 <col>
 805 </colgroup>
 806 <tbody>
 807 <tr>
 808 <td>
 809                   <p><span><strong class="command">any</strong></span></p>
 810                 </td>
 811 <td>
 812                   <p>
 813                     Matches all hosts.
 814                   </p>
 815                 </td>
 816 </tr>
 817 <tr>
 818 <td>
 819                   <p><span><strong class="command">none</strong></span></p>
 820                 </td>
 821 <td>
 822                   <p>
 823                     Matches no hosts.
 824                   </p>
 825                 </td>
 826 </tr>
 827 <tr>
 828 <td>
 829                   <p><span><strong class="command">localhost</strong></span></p>
 830                 </td>
 831 <td>
 832                   <p>
 833                     Matches the IPv4 and IPv6 addresses of all network
 834                     interfaces on the system.
 835                   </p>
 836                 </td>
 837 </tr>
 838 <tr>
 839 <td>
 840                   <p><span><strong class="command">localnets</strong></span></p>
 841                 </td>
 842 <td>
 843                   <p>
 844                     Matches any host on an IPv4 or IPv6 network
 845                     for which the system has an interface.
 846                     Some systems do not provide a way to determine the prefix
 847                     lengths of
 848                     local IPv6 addresses.
 849                     In such a case, <span><strong class="command">localnets</strong></span>
 850                     only matches the local
 851                     IPv6 addresses, just like <span><strong class="command">localhost</strong></span>.
 852                   </p>
 853                 </td>
 854 </tr>
 855 </tbody>
 856 </table></div>
 857 </div>
 858 <div class="sect2" lang="en">
 859 <div class="titlepage"><div><div><h3 class="title">
 860 <a name="id2574282"></a><span><strong class="command">controls</strong></span> Statement Grammar</h3></div></div></div>
 861 <pre class="programlisting"><span><strong class="command">controls</strong></span> {
 862    [ inet ( ip_addr | * ) [ port ip_port ] allow { <em class="replaceable"><code> address_match_list </code></em> }
 863                 keys { <em class="replaceable"><code>key_list</code></em> }; ]
 864    [ inet ...; ]
 865    [ 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> keys { <em class="replaceable"><code>key_list</code></em> }; ]
 866    [ unix ...; ]
 867 };
 868 </pre>
 869 </div>
 870 <div class="sect2" lang="en">
 871 <div class="titlepage"><div><div><h3 class="title">
 872 <a name="controls_statement_definition_and_usage"></a><span><strong class="command">controls</strong></span> Statement Definition and
 873           Usage</h3></div></div></div>
 874 <p>
 875           The <span><strong class="command">controls</strong></span> statement declares control
 876           channels to be used by system administrators to control the
 877           operation of the name server. These control channels are
 878           used by the <span><strong class="command">rndc</strong></span> utility to send
 879           commands to and retrieve non-DNS results from a name server.
 880         </p>
 881 <p>
 882           An <span><strong class="command">inet</strong></span> control channel is a TCP socket
 883           listening at the specified <span><strong class="command">ip_port</strong></span> on the
 884           specified <span><strong class="command">ip_addr</strong></span>, which can be an IPv4 or IPv6
 885           address.  An <span><strong class="command">ip_addr</strong></span> of <code class="literal">*</code> (asterisk) is
 886           interpreted as the IPv4 wildcard address; connections will be
 887           accepted on any of the system's IPv4 addresses.
 888           To listen on the IPv6 wildcard address,
 889           use an <span><strong class="command">ip_addr</strong></span> of <code class="literal">::</code>.
 890           If you will only use <span><strong class="command">rndc</strong></span> on the local host,
 891           using the loopback address (<code class="literal">127.0.0.1</code>
 892           or <code class="literal">::1</code>) is recommended for maximum security.
 893         </p>
 894 <p>
 895           If no port is specified, port 953 is used. The asterisk
 896           "<code class="literal">*</code>" cannot be used for <span><strong class="command">ip_port</strong></span>.
 897         </p>
 898 <p>
 899           The ability to issue commands over the control channel is
 900           restricted by the <span><strong class="command">allow</strong></span> and
 901           <span><strong class="command">keys</strong></span> clauses.
 902           Connections to the control channel are permitted based on the
 903           <span><strong class="command">address_match_list</strong></span>.  This is for simple
 904           IP address based filtering only; any <span><strong class="command">key_id</strong></span>
 905           elements of the <span><strong class="command">address_match_list</strong></span>
 906           are ignored.
 907         </p>
 908 <p>
 909           A <span><strong class="command">unix</strong></span> control channel is a UNIX domain
 910           socket listening at the specified path in the file system.
 911           Access to the socket is specified by the <span><strong class="command">perm</strong></span>,
 912           <span><strong class="command">owner</strong></span> and <span><strong class="command">group</strong></span> clauses.
 913           Note on some platforms (SunOS and Solaris) the permissions
 914           (<span><strong class="command">perm</strong></span>) are applied to the parent directory
 915           as the permissions on the socket itself are ignored.
 916         </p>
 917 <p>
 918           The primary authorization mechanism of the command
 919           channel is the <span><strong class="command">key_list</strong></span>, which
 920           contains a list of <span><strong class="command">key_id</strong></span>s.
 921           Each <span><strong class="command">key_id</strong></span> in the <span><strong class="command">key_list</strong></span>
 922           is authorized to execute commands over the control channel.
 923           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>)
 924           for information about configuring keys in <span><strong class="command">rndc</strong></span>.
 925         </p>
 926 <p>
 927           If no <span><strong class="command">controls</strong></span> statement is present,
 928           <span><strong class="command">named</strong></span> will set up a default
 929           control channel listening on the loopback address 127.0.0.1
 930           and its IPv6 counterpart ::1.
 931           In this case, and also when the <span><strong class="command">controls</strong></span> statement
 932           is present but does not have a <span><strong class="command">keys</strong></span> clause,
 933           <span><strong class="command">named</strong></span> will attempt to load the command channel key
 934           from the file <code class="filename">rndc.key</code> in
 935           <code class="filename">/etc</code> (or whatever <code class="varname">sysconfdir</code>
 936           was specified as when <acronym class="acronym">BIND</acronym> was built).
 937           To create a <code class="filename">rndc.key</code> file, run
 938           <strong class="userinput"><code>rndc-confgen -a</code></strong>.
 939         </p>
 940 <p>
 941           The <code class="filename">rndc.key</code> feature was created to
 942           ease the transition of systems from <acronym class="acronym">BIND</acronym> 8,
 943           which did not have digital signatures on its command channel
 944           messages and thus did not have a <span><strong class="command">keys</strong></span> clause.
 945
 946           It makes it possible to use an existing <acronym class="acronym">BIND</acronym> 8
 947           configuration file in <acronym class="acronym">BIND</acronym> 9 unchanged,
 948           and still have <span><strong class="command">rndc</strong></span> work the same way
 949           <span><strong class="command">ndc</strong></span> worked in BIND 8, simply by executing the
 950           command <strong class="userinput"><code>rndc-confgen -a</code></strong> after BIND 9 is
 951           installed.
 952         </p>
 953 <p>
 954           Since the <code class="filename">rndc.key</code> feature
 955           is only intended to allow the backward-compatible usage of
 956           <acronym class="acronym">BIND</acronym> 8 configuration files, this
 957           feature does not
 958           have a high degree of configurability.  You cannot easily change
 959           the key name or the size of the secret, so you should make a
 960           <code class="filename">rndc.conf</code> with your own key if you
 961           wish to change
 962           those things.  The <code class="filename">rndc.key</code> file
 963           also has its
 964           permissions set such that only the owner of the file (the user that
 965           <span><strong class="command">named</strong></span> is running as) can access it.
 966           If you
 967           desire greater flexibility in allowing other users to access
 968           <span><strong class="command">rndc</strong></span> commands, then you need to create
 969           a
 970           <code class="filename">rndc.conf</code> file and make it group
 971           readable by a group
 972           that contains the users who should have access.
 973         </p>
 974 <p>
 975           To disable the command channel, use an empty
 976           <span><strong class="command">controls</strong></span> statement:
 977           <span><strong class="command">controls { };</strong></span>.
 978         </p>
 979 </div>
 980 <div class="sect2" lang="en">
 981 <div class="titlepage"><div><div><h3 class="title">
 982 <a name="id2574711"></a><span><strong class="command">include</strong></span> Statement Grammar</h3></div></div></div>
 983 <pre class="programlisting">include <em class="replaceable"><code>filename</code></em>;</pre>
 984 </div>
 985 <div class="sect2" lang="en">
 986 <div class="titlepage"><div><div><h3 class="title">
 987 <a name="id2574726"></a><span><strong class="command">include</strong></span> Statement Definition and
 988           Usage</h3></div></div></div>
 989 <p>
 990           The <span><strong class="command">include</strong></span> statement inserts the
 991           specified file at the point where the <span><strong class="command">include</strong></span>
 992           statement is encountered. The <span><strong class="command">include</strong></span>
 993                 statement facilitates the administration of configuration
 994           files
 995           by permitting the reading or writing of some things but not
 996           others. For example, the statement could include private keys
 997           that are readable only by the name server.
 998         </p>
 999 </div>
1000 <div class="sect2" lang="en">
1001 <div class="titlepage"><div><div><h3 class="title">
1002 <a name="id2574749"></a><span><strong class="command">key</strong></span> Statement Grammar</h3></div></div></div>
1003 <pre class="programlisting">key <em class="replaceable"><code>key_id</code></em> {
1004     algorithm <em class="replaceable"><code>string</code></em>;
1005     secret <em class="replaceable"><code>string</code></em>;
1006 };
1007 </pre>
1008 </div>
1009 <div class="sect2" lang="en">
1010 <div class="titlepage"><div><div><h3 class="title">
1011 <a name="id2574771"></a><span><strong class="command">key</strong></span> Statement Definition and Usage</h3></div></div></div>
1012 <p>
1013           The <span><strong class="command">key</strong></span> statement defines a shared
1014           secret key for use with TSIG (see <a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
1015           or the command channel
1016           (see <a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and
1017           Usage">the section called &#8220;<span><strong class="command">controls</strong></span> Statement Definition and
1018           Usage&#8221;</a>).
1019         </p>
1020 <p>
1021           The <span><strong class="command">key</strong></span> statement can occur at the
1022           top level
1023           of the configuration file or inside a <span><strong class="command">view</strong></span>
1024           statement.  Keys defined in top-level <span><strong class="command">key</strong></span>
1025           statements can be used in all views.  Keys intended for use in
1026           a <span><strong class="command">controls</strong></span> statement
1027           (see <a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and
1028           Usage">the section called &#8220;<span><strong class="command">controls</strong></span> Statement Definition and
1029           Usage&#8221;</a>)
1030           must be defined at the top level.
1031         </p>
1032 <p>
1033           The <em class="replaceable"><code>key_id</code></em>, also known as the
1034           key name, is a domain name uniquely identifying the key. It can
1035           be used in a <span><strong class="command">server</strong></span>
1036           statement to cause requests sent to that
1037           server to be signed with this key, or in address match lists to
1038           verify that incoming requests have been signed with a key
1039           matching this name, algorithm, and secret.
1040         </p>
1041 <p>
1042           The <em class="replaceable"><code>algorithm_id</code></em> is a string
1043           that specifies a security/authentication algorithm.  Named
1044           supports <code class="literal">hmac-md5</code>,
1045           <code class="literal">hmac-sha1</code>, <code class="literal">hmac-sha224</code>,
1046           <code class="literal">hmac-sha256</code>, <code class="literal">hmac-sha384</code>
1047           and <code class="literal">hmac-sha512</code> TSIG authentication.
1048           Truncated hashes are supported by appending the minimum
1049           number of required bits preceded by a dash, e.g.
1050           <code class="literal">hmac-sha1-80</code>.  The
1051           <em class="replaceable"><code>secret_string</code></em> is the secret
1052           to be used by the algorithm, and is treated as a base-64
1053           encoded string.
1054         </p>
1055 </div>
1056 <div class="sect2" lang="en">
1057 <div class="titlepage"><div><div><h3 class="title">
1058 <a name="id2574930"></a><span><strong class="command">logging</strong></span> Statement Grammar</h3></div></div></div>
1059 <pre class="programlisting"><span><strong class="command">logging</strong></span> {
1060    [ <span><strong class="command">channel</strong></span> <em class="replaceable"><code>channel_name</code></em> {
1061      ( <span><strong class="command">file</strong></span> <em class="replaceable"><code>path name</code></em>
1062          [ <span><strong class="command">versions</strong></span> ( <em class="replaceable"><code>number</code></em> | <span><strong class="command">unlimited</strong></span> ) ]
1063          [ <span><strong class="command">size</strong></span> <em class="replaceable"><code>size spec</code></em> ]
1064        | <span><strong class="command">syslog</strong></span> <em class="replaceable"><code>syslog_facility</code></em>
1065        | <span><strong class="command">stderr</strong></span>
1066        | <span><strong class="command">null</strong></span> );
1067      [ <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> |
1068                  <code class="option">info</code> | <code class="option">debug</code> [ <em class="replaceable"><code>level</code></em> ] | <code class="option">dynamic</code> ); ]
1069      [ <span><strong class="command">print-category</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1070      [ <span><strong class="command">print-severity</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1071      [ <span><strong class="command">print-time</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1072    }; ]
1073    [ <span><strong class="command">category</strong></span> <em class="replaceable"><code>category_name</code></em> {
1074      <em class="replaceable"><code>channel_name</code></em> ; [ <em class="replaceable"><code>channel_name</code></em> ; ... ]
1075    }; ]
1076    ...
1077 };
1078 </pre>
1079 </div>
1080 <div class="sect2" lang="en">
1081 <div class="titlepage"><div><div><h3 class="title">
1082 <a name="id2575056"></a><span><strong class="command">logging</strong></span> Statement Definition and
1083           Usage</h3></div></div></div>
1084 <p>
1085           The <span><strong class="command">logging</strong></span> statement configures a
1086           wide
1087           variety of logging options for the name server. Its <span><strong class="command">channel</strong></span> phrase
1088           associates output methods, format options and severity levels with
1089           a name that can then be used with the <span><strong class="command">category</strong></span> phrase
1090           to select how various classes of messages are logged.
1091         </p>
1092 <p>
1093           Only one <span><strong class="command">logging</strong></span> statement is used to
1094           define
1095           as many channels and categories as are wanted. If there is no <span><strong class="command">logging</strong></span> statement,
1096           the logging configuration will be:
1097         </p>
1098 <pre class="programlisting">logging {
1099      category default { default_syslog; default_debug; };
1100      category unmatched { null; };
1101 };
1102 </pre>
1103 <p>
1104           In <acronym class="acronym">BIND</acronym> 9, the logging configuration
1105           is only established when
1106           the entire configuration file has been parsed.  In <acronym class="acronym">BIND</acronym> 8, it was
1107           established as soon as the <span><strong class="command">logging</strong></span>
1108           statement
1109           was parsed. When the server is starting up, all logging messages
1110           regarding syntax errors in the configuration file go to the default
1111           channels, or to standard error if the "<code class="option">-g</code>" option
1112           was specified.
1113         </p>
1114 <div class="sect3" lang="en">
1115 <div class="titlepage"><div><div><h4 class="title">
1116 <a name="id2575108"></a>The <span><strong class="command">channel</strong></span> Phrase</h4></div></div></div>
1117 <p>
1118             All log output goes to one or more <span class="emphasis"><em>channels</em></span>;
1119             you can make as many of them as you want.
1120           </p>
1121 <p>
1122             Every channel definition must include a destination clause that
1123             says whether messages selected for the channel go to a file, to a
1124             particular syslog facility, to the standard error stream, or are
1125             discarded. It can optionally also limit the message severity level
1126             that will be accepted by the channel (the default is
1127             <span><strong class="command">info</strong></span>), and whether to include a
1128             <span><strong class="command">named</strong></span>-generated time stamp, the
1129             category name
1130             and/or severity level (the default is not to include any).
1131           </p>
1132 <p>
1133             The <span><strong class="command">null</strong></span> destination clause
1134             causes all messages sent to the channel to be discarded;
1135             in that case, other options for the channel are meaningless.
1136           </p>
1137 <p>
1138             The <span><strong class="command">file</strong></span> destination clause directs
1139             the channel
1140             to a disk file.  It can include limitations
1141             both on how large the file is allowed to become, and how many
1142             versions
1143             of the file will be saved each time the file is opened.
1144           </p>
1145 <p>
1146             If you use the <span><strong class="command">versions</strong></span> log file
1147             option, then
1148             <span><strong class="command">named</strong></span> will retain that many backup
1149             versions of the file by
1150             renaming them when opening.  For example, if you choose to keep
1151             three old versions
1152             of the file <code class="filename">lamers.log</code>, then just
1153             before it is opened
1154             <code class="filename">lamers.log.1</code> is renamed to
1155             <code class="filename">lamers.log.2</code>, <code class="filename">lamers.log.0</code> is renamed
1156             to <code class="filename">lamers.log.1</code>, and <code class="filename">lamers.log</code> is
1157             renamed to <code class="filename">lamers.log.0</code>.
1158             You can say <span><strong class="command">versions unlimited</strong></span> to
1159             not limit
1160             the number of versions.
1161             If a <span><strong class="command">size</strong></span> option is associated with
1162             the log file,
1163             then renaming is only done when the file being opened exceeds the
1164             indicated size.  No backup versions are kept by default; any
1165             existing
1166             log file is simply appended.
1167           </p>
1168 <p>
1169             The <span><strong class="command">size</strong></span> option for files is used
1170             to limit log
1171             growth. If the file ever exceeds the size, then <span><strong class="command">named</strong></span> will
1172             stop writing to the file unless it has a <span><strong class="command">versions</strong></span> option
1173             associated with it.  If backup versions are kept, the files are
1174             rolled as
1175             described above and a new one begun.  If there is no
1176             <span><strong class="command">versions</strong></span> option, no more data will
1177             be written to the log
1178             until some out-of-band mechanism removes or truncates the log to
1179             less than the
1180             maximum size.  The default behavior is not to limit the size of
1181             the
1182             file.
1183           </p>
1184 <p>
1185             Example usage of the <span><strong class="command">size</strong></span> and
1186             <span><strong class="command">versions</strong></span> options:
1187           </p>
1188 <pre class="programlisting">channel an_example_channel {
1189     file "example.log" versions 3 size 20m;
1190     print-time yes;
1191     print-category yes;
1192 };
1193 </pre>
1194 <p>
1195             The <span><strong class="command">syslog</strong></span> destination clause
1196             directs the
1197             channel to the system log.  Its argument is a
1198             syslog facility as described in the <span><strong class="command">syslog</strong></span> man
1199             page. Known facilities are <span><strong class="command">kern</strong></span>, <span><strong class="command">user</strong></span>,
1200             <span><strong class="command">mail</strong></span>, <span><strong class="command">daemon</strong></span>, <span><strong class="command">auth</strong></span>,
1201             <span><strong class="command">syslog</strong></span>, <span><strong class="command">lpr</strong></span>, <span><strong class="command">news</strong></span>,
1202             <span><strong class="command">uucp</strong></span>, <span><strong class="command">cron</strong></span>, <span><strong class="command">authpriv</strong></span>,
1203             <span><strong class="command">ftp</strong></span>, <span><strong class="command">local0</strong></span>, <span><strong class="command">local1</strong></span>,
1204             <span><strong class="command">local2</strong></span>, <span><strong class="command">local3</strong></span>, <span><strong class="command">local4</strong></span>,
1205             <span><strong class="command">local5</strong></span>, <span><strong class="command">local6</strong></span> and
1206             <span><strong class="command">local7</strong></span>, however not all facilities
1207             are supported on
1208             all operating systems.
1209             How <span><strong class="command">syslog</strong></span> will handle messages
1210             sent to
1211             this facility is described in the <span><strong class="command">syslog.conf</strong></span> man
1212             page. If you have a system which uses a very old version of <span><strong class="command">syslog</strong></span> that
1213             only uses two arguments to the <span><strong class="command">openlog()</strong></span> function,
1214             then this clause is silently ignored.
1215           </p>
1216 <p>
1217             The <span><strong class="command">severity</strong></span> clause works like <span><strong class="command">syslog</strong></span>'s
1218             "priorities", except that they can also be used if you are writing
1219             straight to a file rather than using <span><strong class="command">syslog</strong></span>.
1220             Messages which are not at least of the severity level given will
1221             not be selected for the channel; messages of higher severity
1222             levels
1223             will be accepted.
1224           </p>
1225 <p>
1226             If you are using <span><strong class="command">syslog</strong></span>, then the <span><strong class="command">syslog.conf</strong></span> priorities
1227             will also determine what eventually passes through. For example,
1228             defining a channel facility and severity as <span><strong class="command">daemon</strong></span> and <span><strong class="command">debug</strong></span> but
1229             only logging <span><strong class="command">daemon.warning</strong></span> via <span><strong class="command">syslog.conf</strong></span> will
1230             cause messages of severity <span><strong class="command">info</strong></span> and
1231             <span><strong class="command">notice</strong></span> to
1232             be dropped. If the situation were reversed, with <span><strong class="command">named</strong></span> writing
1233             messages of only <span><strong class="command">warning</strong></span> or higher,
1234             then <span><strong class="command">syslogd</strong></span> would
1235             print all messages it received from the channel.
1236           </p>
1237 <p>
1238             The <span><strong class="command">stderr</strong></span> destination clause
1239             directs the
1240             channel to the server's standard error stream.  This is intended
1241             for
1242             use when the server is running as a foreground process, for
1243             example
1244             when debugging a configuration.
1245           </p>
1246 <p>
1247             The server can supply extensive debugging information when
1248             it is in debugging mode. If the server's global debug level is
1249             greater
1250             than zero, then debugging mode will be active. The global debug
1251             level is set either by starting the <span><strong class="command">named</strong></span> server
1252             with the <code class="option">-d</code> flag followed by a positive integer,
1253             or by running <span><strong class="command">rndc trace</strong></span>.
1254             The global debug level
1255             can be set to zero, and debugging mode turned off, by running <span><strong class="command">rndc
1256 notrace</strong></span>. All debugging messages in the server have a debug
1257             level, and higher debug levels give more detailed output. Channels
1258             that specify a specific debug severity, for example:
1259           </p>
1260 <pre class="programlisting">channel specific_debug_level {
1261     file "foo";
1262     severity debug 3;
1263 };
1264 </pre>
1265 <p>
1266             will get debugging output of level 3 or less any time the
1267             server is in debugging mode, regardless of the global debugging
1268             level. Channels with <span><strong class="command">dynamic</strong></span>
1269             severity use the
1270             server's global debug level to determine what messages to print.
1271           </p>
1272 <p>
1273             If <span><strong class="command">print-time</strong></span> has been turned on,
1274             then
1275             the date and time will be logged. <span><strong class="command">print-time</strong></span> may
1276             be specified for a <span><strong class="command">syslog</strong></span> channel,
1277             but is usually
1278             pointless since <span><strong class="command">syslog</strong></span> also prints
1279             the date and
1280             time. If <span><strong class="command">print-category</strong></span> is
1281             requested, then the
1282             category of the message will be logged as well. Finally, if <span><strong class="command">print-severity</strong></span> is
1283             on, then the severity level of the message will be logged. The <span><strong class="command">print-</strong></span> options may
1284             be used in any combination, and will always be printed in the
1285             following
1286             order: time, category, severity. Here is an example where all
1287             three <span><strong class="command">print-</strong></span> options
1288             are on:
1289           </p>
1290 <p>
1291             <code class="computeroutput">28-Feb-2000 15:05:32.863 general: notice: running</code>
1292           </p>
1293 <p>
1294             There are four predefined channels that are used for
1295             <span><strong class="command">named</strong></span>'s default logging as follows.
1296             How they are
1297             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>.
1298           </p>
1299 <pre class="programlisting">channel default_syslog {
1300     syslog daemon;                      // send to syslog's daemon
1301                                         // facility
1302     severity info;                      // only send priority info
1303                                         // and higher
1304 };
1305
1306 channel default_debug {
1307     file "named.run";                   // write to named.run in
1308                                         // the working directory
1309                                         // Note: stderr is used instead
1310                                         // of "named.run"
1311                                         // if the server is started
1312                                         // with the '-f' option.
1313     severity dynamic;                   // log at the server's
1314                                         // current debug level
1315 };
1316
1317 channel default_stderr {
1318     stderr;                             // writes to stderr
1319     severity info;                      // only send priority info
1320                                         // and higher
1321 };
1322
1323 channel null {
1324    null;                                // toss anything sent to
1325                                         // this channel
1326 };
1327 </pre>
1328 <p>
1329             The <span><strong class="command">default_debug</strong></span> channel has the
1330             special
1331             property that it only produces output when the server's debug
1332             level is
1333             nonzero.  It normally writes to a file called <code class="filename">named.run</code>
1334             in the server's working directory.
1335           </p>
1336 <p>
1337             For security reasons, when the "<code class="option">-u</code>"
1338             command line option is used, the <code class="filename">named.run</code> file
1339             is created only after <span><strong class="command">named</strong></span> has
1340             changed to the
1341             new UID, and any debug output generated while <span><strong class="command">named</strong></span> is
1342             starting up and still running as root is discarded.  If you need
1343             to capture this output, you must run the server with the "<code class="option">-g</code>"
1344             option and redirect standard error to a file.
1345           </p>
1346 <p>
1347             Once a channel is defined, it cannot be redefined. Thus you
1348             cannot alter the built-in channels directly, but you can modify
1349             the default logging by pointing categories at channels you have
1350             defined.
1351           </p>
1352 </div>
1353 <div class="sect3" lang="en">
1354 <div class="titlepage"><div><div><h4 class="title">
1355 <a name="the_category_phrase"></a>The <span><strong class="command">category</strong></span> Phrase</h4></div></div></div>
1356 <p>
1357             There are many categories, so you can send the logs you want
1358             to see wherever you want, without seeing logs you don't want. If
1359             you don't specify a list of channels for a category, then log
1360             messages
1361             in that category will be sent to the <span><strong class="command">default</strong></span> category
1362             instead. If you don't specify a default category, the following
1363             "default default" is used:
1364           </p>
1365 <pre class="programlisting">category default { default_syslog; default_debug; };
1366 </pre>
1367 <p>
1368             As an example, let's say you want to log security events to
1369             a file, but you also want keep the default logging behavior. You'd
1370             specify the following:
1371           </p>
1372 <pre class="programlisting">channel my_security_channel {
1373     file "my_security_file";
1374     severity info;
1375 };
1376 category security {
1377     my_security_channel;
1378     default_syslog;
1379     default_debug;
1380 };</pre>
1381 <p>
1382             To discard all messages in a category, specify the <span><strong class="command">null</strong></span> channel:
1383           </p>
1384 <pre class="programlisting">category xfer-out { null; };
1385 category notify { null; };
1386 </pre>
1387 <p>
1388             Following are the available categories and brief descriptions
1389             of the types of log information they contain. More
1390             categories may be added in future <acronym class="acronym">BIND</acronym> releases.
1391           </p>
1392 <div class="informaltable"><table border="1">
1393 <colgroup>
1394 <col>
1395 <col>
1396 </colgroup>
1397 <tbody>
1398 <tr>
1399 <td>
1400                     <p><span><strong class="command">default</strong></span></p>
1401                   </td>
1402 <td>
1403                     <p>
1404                       The default category defines the logging
1405                       options for those categories where no specific
1406                       configuration has been
1407                       defined.
1408                     </p>
1409                   </td>
1410 </tr>
1411 <tr>
1412 <td>
1413                     <p><span><strong class="command">general</strong></span></p>
1414                   </td>
1415 <td>
1416                     <p>
1417                       The catch-all. Many things still aren't
1418                       classified into categories, and they all end up here.
1419                     </p>
1420                   </td>
1421 </tr>
1422 <tr>
1423 <td>
1424                     <p><span><strong class="command">database</strong></span></p>
1425                   </td>
1426 <td>
1427                     <p>
1428                       Messages relating to the databases used
1429                       internally by the name server to store zone and cache
1430                       data.
1431                     </p>
1432                   </td>
1433 </tr>
1434 <tr>
1435 <td>
1436                     <p><span><strong class="command">security</strong></span></p>
1437                   </td>
1438 <td>
1439                     <p>
1440                       Approval and denial of requests.
1441                     </p>
1442                   </td>
1443 </tr>
1444 <tr>
1445 <td>
1446                     <p><span><strong class="command">config</strong></span></p>
1447                   </td>
1448 <td>
1449                     <p>
1450                       Configuration file parsing and processing.
1451                     </p>
1452                   </td>
1453 </tr>
1454 <tr>
1455 <td>
1456                     <p><span><strong class="command">resolver</strong></span></p>
1457                   </td>
1458 <td>
1459                     <p>
1460                       DNS resolution, such as the recursive
1461                       lookups performed on behalf of clients by a caching name
1462                       server.
1463                     </p>
1464                   </td>
1465 </tr>
1466 <tr>
1467 <td>
1468                     <p><span><strong class="command">xfer-in</strong></span></p>
1469                   </td>
1470 <td>
1471                     <p>
1472                       Zone transfers the server is receiving.
1473                     </p>
1474                   </td>
1475 </tr>
1476 <tr>
1477 <td>
1478                     <p><span><strong class="command">xfer-out</strong></span></p>
1479                   </td>
1480 <td>
1481                     <p>
1482                       Zone transfers the server is sending.
1483                     </p>
1484                   </td>
1485 </tr>
1486 <tr>
1487 <td>
1488                     <p><span><strong class="command">notify</strong></span></p>
1489                   </td>
1490 <td>
1491                     <p>
1492                       The NOTIFY protocol.
1493                     </p>
1494                   </td>
1495 </tr>
1496 <tr>
1497 <td>
1498                     <p><span><strong class="command">client</strong></span></p>
1499                   </td>
1500 <td>
1501                     <p>
1502                       Processing of client requests.
1503                     </p>
1504                   </td>
1505 </tr>
1506 <tr>
1507 <td>
1508                     <p><span><strong class="command">unmatched</strong></span></p>
1509                   </td>
1510 <td>
1511                     <p>
1512                       Messages that named was unable to determine the
1513                       class of or for which there was no matching <span><strong class="command">view</strong></span>.
1514                       A one line summary is also logged to the <span><strong class="command">client</strong></span> category.
1515                       This category is best sent to a file or stderr, by
1516                       default it is sent to
1517                       the <span><strong class="command">null</strong></span> channel.
1518                     </p>
1519                   </td>
1520 </tr>
1521 <tr>
1522 <td>
1523                     <p><span><strong class="command">network</strong></span></p>
1524                   </td>
1525 <td>
1526                     <p>
1527                       Network operations.
1528                     </p>
1529                   </td>
1530 </tr>
1531 <tr>
1532 <td>
1533                     <p><span><strong class="command">update</strong></span></p>
1534                   </td>
1535 <td>
1536                     <p>
1537                       Dynamic updates.
1538                     </p>
1539                   </td>
1540 </tr>
1541 <tr>
1542 <td>
1543                     <p><span><strong class="command">update-security</strong></span></p>
1544                   </td>
1545 <td>
1546                     <p>
1547                       Approval and denial of update requests.
1548                     </p>
1549                   </td>
1550 </tr>
1551 <tr>
1552 <td>
1553                     <p><span><strong class="command">queries</strong></span></p>
1554                   </td>
1555 <td>
1556                     <p>
1557                       Specify where queries should be logged to.
1558                     </p>
1559                     <p>
1560                       At startup, specifying the category <span><strong class="command">queries</strong></span> will also
1561                       enable query logging unless <span><strong class="command">querylog</strong></span> option has been
1562                       specified.
1563                     </p>
1564                     <p>
1565                       The query log entry reports the client's IP address and
1566                       port number, and the
1567                       query name, class and type.  It also reports whether the
1568                       Recursion Desired
1569                       flag was set (+ if set, - if not set), EDNS was in use
1570                       (E) or if the
1571                       query was signed (S).
1572                     </p>
1573                     <p>
1574                       <code class="computeroutput">client 127.0.0.1#62536: query: www.example.com IN AAAA +SE</code>
1575                     </p>
1576                     <p>
1577                       <code class="computeroutput">client ::1#62537: query: www.example.net IN AAAA -SE</code>
1578                     </p>
1579                   </td>
1580 </tr>
1581 <tr>
1582 <td>
1583                     <p><span><strong class="command">dispatch</strong></span></p>
1584                   </td>
1585 <td>
1586                     <p>
1587                       Dispatching of incoming packets to the
1588                       server modules where they are to be processed.
1589                     </p>
1590                   </td>
1591 </tr>
1592 <tr>
1593 <td>
1594                     <p><span><strong class="command">dnssec</strong></span></p>
1595                   </td>
1596 <td>
1597                     <p>
1598                       DNSSEC and TSIG protocol processing.
1599                     </p>
1600                   </td>
1601 </tr>
1602 <tr>
1603 <td>
1604                     <p><span><strong class="command">lame-servers</strong></span></p>
1605                   </td>
1606 <td>
1607                     <p>
1608                       Lame servers.  These are misconfigurations
1609                       in remote servers, discovered by BIND 9 when trying to
1610                       query
1611                       those servers during resolution.
1612                     </p>
1613                   </td>
1614 </tr>
1615 <tr>
1616 <td>
1617                     <p><span><strong class="command">delegation-only</strong></span></p>
1618                   </td>
1619 <td>
1620                     <p>
1621                       Delegation only.  Logs queries that have have
1622                       been forced to NXDOMAIN as the result of a
1623                       delegation-only zone or
1624                       a <span><strong class="command">delegation-only</strong></span> in a
1625                       hint or stub zone declaration.
1626                     </p>
1627                   </td>
1628 </tr>
1629 </tbody>
1630 </table></div>
1631 </div>
1632 </div>
1633 <div class="sect2" lang="en">
1634 <div class="titlepage"><div><div><h3 class="title">
1635 <a name="id2576406"></a><span><strong class="command">lwres</strong></span> Statement Grammar</h3></div></div></div>
1636 <p>
1637            This is the grammar of the <span><strong class="command">lwres</strong></span>
1638           statement in the <code class="filename">named.conf</code> file:
1639         </p>
1640 <pre class="programlisting"><span><strong class="command">lwres</strong></span> {
1641     [<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>] ; [<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>]
1642     [<span class="optional"> view <em class="replaceable"><code>view_name</code></em>; </span>]
1643     [<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>]
1644     [<span class="optional"> ndots <em class="replaceable"><code>number</code></em>; </span>]
1645 };
1646 </pre>
1647 </div>
1648 <div class="sect2" lang="en">
1649 <div class="titlepage"><div><div><h3 class="title">
1650 <a name="id2576480"></a><span><strong class="command">lwres</strong></span> Statement Definition and Usage</h3></div></div></div>
1651 <p>
1652           The <span><strong class="command">lwres</strong></span> statement configures the
1653           name
1654           server to also act as a lightweight resolver server. (See
1655           <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
1656           <span><strong class="command">lwres</strong></span> statements configuring
1657           lightweight resolver servers with different properties.
1658         </p>
1659 <p>
1660           The <span><strong class="command">listen-on</strong></span> statement specifies a
1661           list of
1662           addresses (and ports) that this instance of a lightweight resolver
1663           daemon
1664           should accept requests on.  If no port is specified, port 921 is
1665           used.
1666           If this statement is omitted, requests will be accepted on
1667           127.0.0.1,
1668           port 921.
1669         </p>
1670 <p>
1671           The <span><strong class="command">view</strong></span> statement binds this
1672           instance of a
1673           lightweight resolver daemon to a view in the DNS namespace, so that
1674           the
1675           response will be constructed in the same manner as a normal DNS
1676           query
1677           matching this view.  If this statement is omitted, the default view
1678           is
1679           used, and if there is no default view, an error is triggered.
1680         </p>
1681 <p>
1682           The <span><strong class="command">search</strong></span> statement is equivalent to
1683           the
1684           <span><strong class="command">search</strong></span> statement in
1685           <code class="filename">/etc/resolv.conf</code>.  It provides a
1686           list of domains
1687           which are appended to relative names in queries.
1688         </p>
1689 <p>
1690           The <span><strong class="command">ndots</strong></span> statement is equivalent to
1691           the
1692           <span><strong class="command">ndots</strong></span> statement in
1693           <code class="filename">/etc/resolv.conf</code>.  It indicates the
1694           minimum
1695           number of dots in a relative domain name that should result in an
1696           exact match lookup before search path elements are appended.
1697         </p>
1698 </div>
1699 <div class="sect2" lang="en">
1700 <div class="titlepage"><div><div><h3 class="title">
1701 <a name="id2576544"></a><span><strong class="command">masters</strong></span> Statement Grammar</h3></div></div></div>
1702 <pre class="programlisting">
1703 <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> | <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>] };
1704 </pre>
1705 </div>
1706 <div class="sect2" lang="en">
1707 <div class="titlepage"><div><div><h3 class="title">
1708 <a name="id2576587"></a><span><strong class="command">masters</strong></span> Statement Definition and
1709           Usage</h3></div></div></div>
1710 <p><span><strong class="command">masters</strong></span>
1711           lists allow for a common set of masters to be easily used by
1712           multiple stub and slave zones.
1713         </p>
1714 </div>
1715 <div class="sect2" lang="en">
1716 <div class="titlepage"><div><div><h3 class="title">
1717 <a name="id2576602"></a><span><strong class="command">options</strong></span> Statement Grammar</h3></div></div></div>
1718 <p>
1719           This is the grammar of the <span><strong class="command">options</strong></span>
1720           statement in the <code class="filename">named.conf</code> file:
1721         </p>
1722 <pre class="programlisting">options {
1723     [<span class="optional"> version <em class="replaceable"><code>version_string</code></em>; </span>]
1724     [<span class="optional"> hostname <em class="replaceable"><code>hostname_string</code></em>; </span>]
1725     [<span class="optional"> server-id <em class="replaceable"><code>server_id_string</code></em>; </span>]
1726     [<span class="optional"> directory <em class="replaceable"><code>path_name</code></em>; </span>]
1727     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
1728     [<span class="optional"> named-xfer <em class="replaceable"><code>path_name</code></em>; </span>]
1729     [<span class="optional"> tkey-domain <em class="replaceable"><code>domainname</code></em>; </span>]
1730     [<span class="optional"> tkey-dhkey <em class="replaceable"><code>key_name</code></em> <em class="replaceable"><code>key_tag</code></em>; </span>]
1731     [<span class="optional"> cache-file <em class="replaceable"><code>path_name</code></em>; </span>]
1732     [<span class="optional"> dump-file <em class="replaceable"><code>path_name</code></em>; </span>]
1733     [<span class="optional"> memstatistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
1734     [<span class="optional"> pid-file <em class="replaceable"><code>path_name</code></em>; </span>]
1735     [<span class="optional"> recursing-file <em class="replaceable"><code>path_name</code></em>; </span>]
1736     [<span class="optional"> statistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
1737     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1738     [<span class="optional"> auth-nxdomain <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1739     [<span class="optional"> deallocate-on-exit <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1740     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em>; </span>]
1741     [<span class="optional"> fake-iquery <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1742     [<span class="optional"> fetch-glue <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1743     [<span class="optional"> flush-zones-on-shutdown <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1744     [<span class="optional"> has-old-clients <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1745     [<span class="optional"> host-statistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1746     [<span class="optional"> host-statistics-max <em class="replaceable"><code>number</code></em>; </span>]
1747     [<span class="optional"> minimal-responses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1748     [<span class="optional"> multiple-cnames <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1749     [<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>]
1750     [<span class="optional"> recursion <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1751     [<span class="optional"> rfc2308-type1 <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1752     [<span class="optional"> use-id-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1753     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1754     [<span class="optional"> dnssec-enable <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1755     [<span class="optional"> dnssec-validation <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1756     [<span class="optional"> dnssec-lookaside <em class="replaceable"><code>domain</code></em> trust-anchor <em class="replaceable"><code>domain</code></em>; </span>]
1757     [<span class="optional"> dnssec-must-be-secure <em class="replaceable"><code>domain yes_or_no</code></em>; </span>]
1758     [<span class="optional"> dnssec-accept-expired <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1759     [<span class="optional"> forward ( <em class="replaceable"><code>only</code></em> | <em class="replaceable"><code>first</code></em> ); </span>]
1760     [<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>]
1761     [<span class="optional"> dual-stack-servers [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] {
1762         ( <em class="replaceable"><code>domain_name</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] |
1763           <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ) ;
1764         ... }; </span>]
1765     [<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> )
1766         ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
1767     [<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>]
1768     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1769     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1770     [<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>]
1771     [<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>]
1772     [<span class="optional"> check-sibling <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1773     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
1774     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
1775     [<span class="optional"> allow-query-cache { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
1776     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
1777     [<span class="optional"> allow-recursion { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
1778     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
1779     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
1780     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1781     [<span class="optional"> allow-v6-synthesis { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
1782     [<span class="optional"> blackhole { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
1783     [<span class="optional"> avoid-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
1784     [<span class="optional"> avoid-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
1785     [<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>]
1786     [<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>]
1787     [<span class="optional"> query-source ( ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> )
1788         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
1789         [<span class="optional"> address ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
1790         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
1791     [<span class="optional"> query-source-v6 ( ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> )
1792         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
1793         [<span class="optional"> address ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
1794         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
1795     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em>; </span>]
1796     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em>; </span>]
1797     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em>; </span>]
1798     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em>; </span>]
1799     [<span class="optional"> tcp-clients <em class="replaceable"><code>number</code></em>; </span>]
1800     [<span class="optional"> recursive-clients <em class="replaceable"><code>number</code></em>; </span>]
1801     [<span class="optional"> serial-query-rate <em class="replaceable"><code>number</code></em>; </span>]
1802     [<span class="optional"> serial-queries <em class="replaceable"><code>number</code></em>; </span>]
1803     [<span class="optional"> tcp-listen-queue <em class="replaceable"><code>number</code></em>; </span>]
1804     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em>; </span>]
1805     [<span class="optional"> transfers-in  <em class="replaceable"><code>number</code></em>; </span>]
1806     [<span class="optional"> transfers-out <em class="replaceable"><code>number</code></em>; </span>]
1807     [<span class="optional"> transfers-per-ns <em class="replaceable"><code>number</code></em>; </span>]
1808     [<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>]
1809     [<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>]
1810     [<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>]
1811     [<span class="optional"> alt-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>]
1812     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1813     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
1814     [<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>]
1815     [<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>]
1816     [<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>] ; [<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>]
1817     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em>; </span>]
1818     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
1819     [<span class="optional"> coresize <em class="replaceable"><code>size_spec</code></em> ; </span>]
1820     [<span class="optional"> datasize <em class="replaceable"><code>size_spec</code></em> ; </span>]
1821     [<span class="optional"> files <em class="replaceable"><code>size_spec</code></em> ; </span>]
1822     [<span class="optional"> stacksize <em class="replaceable"><code>size_spec</code></em> ; </span>]
1823     [<span class="optional"> cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
1824     [<span class="optional"> heartbeat-interval <em class="replaceable"><code>number</code></em>; </span>]
1825     [<span class="optional"> interface-interval <em class="replaceable"><code>number</code></em>; </span>]
1826     [<span class="optional"> statistics-interval <em class="replaceable"><code>number</code></em>; </span>]
1827     [<span class="optional"> topology { <em class="replaceable"><code>address_match_list</code></em> }</span>];
1828     [<span class="optional"> sortlist { <em class="replaceable"><code>address_match_list</code></em> }</span>];
1829     [<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>] };
1830     [<span class="optional"> lame-ttl <em class="replaceable"><code>number</code></em>; </span>]
1831     [<span class="optional"> max-ncache-ttl <em class="replaceable"><code>number</code></em>; </span>]
1832     [<span class="optional"> max-cache-ttl <em class="replaceable"><code>number</code></em>; </span>]
1833     [<span class="optional"> sig-validity-interval <em class="replaceable"><code>number</code></em> ; </span>]
1834     [<span class="optional"> min-roots <em class="replaceable"><code>number</code></em>; </span>]
1835     [<span class="optional"> use-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
1836     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1837     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1838     [<span class="optional"> treat-cr-as-space <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
1839     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
1840     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
1841     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
1842     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
1843     [<span class="optional"> port <em class="replaceable"><code>ip_port</code></em>; </span>]
1844     [<span class="optional"> additional-from-auth <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
1845     [<span class="optional"> additional-from-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
1846     [<span class="optional"> random-device <em class="replaceable"><code>path_name</code></em> ; </span>]
1847     [<span class="optional"> max-cache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
1848     [<span class="optional"> match-mapped-addresses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
1849     [<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>]
1850     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em>; </span>]
1851     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em>; </span>]
1852     [<span class="optional"> root-delegation-only [<span class="optional"> exclude { <em class="replaceable"><code>namelist</code></em> } </span>] ; </span>]
1853     [<span class="optional"> querylog <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
1854     [<span class="optional"> disable-algorithms <em class="replaceable"><code>domain</code></em> { <em class="replaceable"><code>algorithm</code></em>; [<span class="optional"> <em class="replaceable"><code>algorithm</code></em>; </span>] }; </span>]
1855     [<span class="optional"> acache-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
1856     [<span class="optional"> acache-cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
1857     [<span class="optional"> max-acache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
1858     [<span class="optional"> clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
1859     [<span class="optional"> max-clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
1860     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
1861     [<span class="optional"> empty-server <em class="replaceable"><code>name</code></em> ; </span>]
1862     [<span class="optional"> empty-contact <em class="replaceable"><code>name</code></em> ; </span>]
1863     [<span class="optional"> empty-zones-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
1864     [<span class="optional"> disable-empty-zone <em class="replaceable"><code>zone_name</code></em> ; </span>]
1865     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
1866     [<span class="optional"> zero-no-soa-ttl-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
1867 };
1868 </pre>
1869 </div>
1870 <div class="sect2" lang="en">
1871 <div class="titlepage"><div><div><h3 class="title">
1872 <a name="options"></a><span><strong class="command">options</strong></span> Statement Definition and
1873           Usage</h3></div></div></div>
1874 <p>
1875           The <span><strong class="command">options</strong></span> statement sets up global
1876           options
1877           to be used by <acronym class="acronym">BIND</acronym>. This statement
1878           may appear only
1879           once in a configuration file. If there is no <span><strong class="command">options</strong></span>
1880           statement, an options block with each option set to its default will
1881           be used.
1882         </p>
1883 <div class="variablelist"><dl>
1884 <dt><span class="term"><span><strong class="command">directory</strong></span></span></dt>
1885 <dd><p>
1886                 The working directory of the server.
1887                 Any non-absolute pathnames in the configuration file will be
1888                 taken
1889                 as relative to this directory. The default location for most
1890                 server
1891                 output files (e.g. <code class="filename">named.run</code>)
1892                 is this directory.
1893                 If a directory is not specified, the working directory
1894                 defaults to `<code class="filename">.</code>', the directory from
1895                 which the server
1896                 was started. The directory specified should be an absolute
1897                 path.
1898               </p></dd>
1899 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
1900 <dd><p>
1901                 When performing dynamic update of secure zones, the
1902                 directory where the public and private key files should be
1903                 found,
1904                 if different than the current working directory.  The
1905                 directory specified
1906                 must be an absolute path.
1907               </p></dd>
1908 <dt><span class="term"><span><strong class="command">named-xfer</strong></span></span></dt>
1909 <dd><p>
1910                 <span class="emphasis"><em>This option is obsolete.</em></span>
1911                 It was used in <acronym class="acronym">BIND</acronym> 8 to
1912                 specify the pathname to the <span><strong class="command">named-xfer</strong></span> program.
1913                 In <acronym class="acronym">BIND</acronym> 9, no separate <span><strong class="command">named-xfer</strong></span> program is
1914                 needed; its functionality is built into the name server.
1915               </p></dd>
1916 <dt><span class="term"><span><strong class="command">tkey-domain</strong></span></span></dt>
1917 <dd><p>
1918                 The domain appended to the names of all
1919                 shared keys generated with
1920                 <span><strong class="command">TKEY</strong></span>. When a client
1921                 requests a <span><strong class="command">TKEY</strong></span> exchange, it
1922                 may or may not specify
1923                 the desired name for the key. If present, the name of the
1924                 shared
1925                 key will be "<code class="varname">client specified part</code>" +
1926                 "<code class="varname">tkey-domain</code>".
1927                 Otherwise, the name of the shared key will be "<code class="varname">random hex
1928 digits</code>" + "<code class="varname">tkey-domain</code>". In most cases,
1929                 the <span><strong class="command">domainname</strong></span> should be the
1930                 server's domain
1931                 name.
1932               </p></dd>
1933 <dt><span class="term"><span><strong class="command">tkey-dhkey</strong></span></span></dt>
1934 <dd><p>
1935                 The Diffie-Hellman key used by the server
1936                 to generate shared keys with clients using the Diffie-Hellman
1937                 mode
1938                 of <span><strong class="command">TKEY</strong></span>. The server must be
1939                 able to load the
1940                 public and private keys from files in the working directory.
1941                 In
1942                 most cases, the keyname should be the server's host name.
1943               </p></dd>
1944 <dt><span class="term"><span><strong class="command">cache-file</strong></span></span></dt>
1945 <dd><p>
1946                 This is for testing only.  Do not use.
1947               </p></dd>
1948 <dt><span class="term"><span><strong class="command">dump-file</strong></span></span></dt>
1949 <dd><p>
1950                 The pathname of the file the server dumps
1951                 the database to when instructed to do so with
1952                 <span><strong class="command">rndc dumpdb</strong></span>.
1953                 If not specified, the default is <code class="filename">named_dump.db</code>.
1954               </p></dd>
1955 <dt><span class="term"><span><strong class="command">memstatistics-file</strong></span></span></dt>
1956 <dd>
1957 <p>
1958                 The pathname of the file the server writes memory
1959                 usage statistics to on exit.  If specified the
1960                 statistics will be written to the file on exit.
1961               </p>
1962 <p>
1963                 In <acronym class="acronym">BIND</acronym> 9.5 and later this will
1964                 default to <code class="filename">named.memstats</code>.
1965                 <acronym class="acronym">BIND</acronym> 9.5 will also introduce
1966                 <span><strong class="command">memstatistics</strong></span> to control the
1967                 writing.
1968               </p>
1969 </dd>
1970 <dt><span class="term"><span><strong class="command">pid-file</strong></span></span></dt>
1971 <dd><p>
1972                 The pathname of the file the server writes its process ID
1973                 in. If not specified, the default is <code class="filename">/var/run/named.pid</code>.
1974                 The pid-file is used by programs that want to send signals to
1975                 the running
1976                 name server. Specifying <span><strong class="command">pid-file none</strong></span> disables the
1977                 use of a PID file &#8212; no file will be written and any
1978                 existing one will be removed.  Note that <span><strong class="command">none</strong></span>
1979                 is a keyword, not a filename, and therefore is not enclosed
1980                 in
1981                 double quotes.
1982               </p></dd>
1983 <dt><span class="term"><span><strong class="command">recursing-file</strong></span></span></dt>
1984 <dd><p>
1985                 The pathname of the file the server dumps
1986                 the queries that are currently recursing when instructed
1987                 to do so with <span><strong class="command">rndc recursing</strong></span>.
1988                 If not specified, the default is <code class="filename">named.recursing</code>.
1989               </p></dd>
1990 <dt><span class="term"><span><strong class="command">statistics-file</strong></span></span></dt>
1991 <dd><p>
1992                 The pathname of the file the server appends statistics
1993                 to when instructed to do so using <span><strong class="command">rndc stats</strong></span>.
1994                 If not specified, the default is <code class="filename">named.stats</code> in the
1995                 server's current directory.  The format of the file is
1996                 described
1997                 in <a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
1998               </p></dd>
1999 <dt><span class="term"><span><strong class="command">port</strong></span></span></dt>
2000 <dd><p>
2001                 The UDP/TCP port number the server uses for
2002                 receiving and sending DNS protocol traffic.
2003                 The default is 53.  This option is mainly intended for server
2004                 testing;
2005                 a server using a port other than 53 will not be able to
2006                 communicate with
2007                 the global DNS.
2008               </p></dd>
2009 <dt><span class="term"><span><strong class="command">random-device</strong></span></span></dt>
2010 <dd><p>
2011                 The source of entropy to be used by the server.  Entropy is
2012                 primarily needed
2013                 for DNSSEC operations, such as TKEY transactions and dynamic
2014                 update of signed
2015                 zones.  This options specifies the device (or file) from which
2016                 to read
2017                 entropy.  If this is a file, operations requiring entropy will
2018                 fail when the
2019                 file has been exhausted.  If not specified, the default value
2020                 is
2021                 <code class="filename">/dev/random</code>
2022                 (or equivalent) when present, and none otherwise.  The
2023                 <span><strong class="command">random-device</strong></span> option takes
2024                 effect during
2025                 the initial configuration load at server startup time and
2026                 is ignored on subsequent reloads.
2027               </p></dd>
2028 <dt><span class="term"><span><strong class="command">preferred-glue</strong></span></span></dt>
2029 <dd><p>
2030                 If specified, the listed type (A or AAAA) will be emitted
2031                 before other glue
2032                 in the additional section of a query response.
2033                 The default is not to prefer any type (NONE).
2034               </p></dd>
2035 <dt><span class="term"><span><strong class="command">root-delegation-only</strong></span></span></dt>
2036 <dd>
2037 <p>
2038                 Turn on enforcement of delegation-only in TLDs (top level domains) and root zones
2039                 with an optional
2040                 exclude list.
2041               </p>
2042 <p>
2043                 Note some TLDs are not delegation only (e.g. "DE", "LV", "US"
2044                 and "MUSEUM").
2045               </p>
2046 <pre class="programlisting">
2047 options {
2048         root-delegation-only exclude { "de"; "lv"; "us"; "museum"; };
2049 };
2050 </pre>
2051 </dd>
2052 <dt><span class="term"><span><strong class="command">disable-algorithms</strong></span></span></dt>
2053 <dd><p>
2054                 Disable the specified DNSSEC algorithms at and below the
2055                 specified name.
2056                 Multiple <span><strong class="command">disable-algorithms</strong></span>
2057                 statements are allowed.
2058                 Only the most specific will be applied.
2059               </p></dd>
2060 <dt><span class="term"><span><strong class="command">dnssec-lookaside</strong></span></span></dt>
2061 <dd><p>
2062                 When set, <span><strong class="command">dnssec-lookaside</strong></span>
2063                 provides the
2064                 validator with an alternate method to validate DNSKEY records
2065                 at the
2066                 top of a zone.  When a DNSKEY is at or below a domain
2067                 specified by the
2068                 deepest <span><strong class="command">dnssec-lookaside</strong></span>, and
2069                 the normal dnssec validation
2070                 has left the key untrusted, the trust-anchor will be append to
2071                 the key
2072                 name and a DLV record will be looked up to see if it can
2073                 validate the
2074                 key.  If the DLV record validates a DNSKEY (similarly to the
2075                 way a DS
2076                 record does) the DNSKEY RRset is deemed to be trusted.
2077               </p></dd>
2078 <dt><span class="term"><span><strong class="command">dnssec-must-be-secure</strong></span></span></dt>
2079 <dd><p>
2080                 Specify hierarchies which must be or may not be secure (signed and
2081                 validated).
2082                 If <strong class="userinput"><code>yes</code></strong>, then named will only accept
2083                 answers if they
2084                 are secure.
2085                 If <strong class="userinput"><code>no</code></strong>, then normal dnssec validation
2086                 applies
2087                 allowing for insecure answers to be accepted.
2088                 The specified domain must be under a <span><strong class="command">trusted-key</strong></span> or
2089                 <span><strong class="command">dnssec-lookaside</strong></span> must be
2090                 active.
2091               </p></dd>
2092 </dl></div>
2093 <div class="sect3" lang="en">
2094 <div class="titlepage"><div><div><h4 class="title">
2095 <a name="boolean_options"></a>Boolean Options</h4></div></div></div>
2096 <div class="variablelist"><dl>
2097 <dt><span class="term"><span><strong class="command">auth-nxdomain</strong></span></span></dt>
2098 <dd><p>
2099                   If <strong class="userinput"><code>yes</code></strong>, then the <span><strong class="command">AA</strong></span> bit
2100                   is always set on NXDOMAIN responses, even if the server is
2101                   not actually
2102                   authoritative. The default is <strong class="userinput"><code>no</code></strong>;
2103                   this is
2104                   a change from <acronym class="acronym">BIND</acronym> 8. If you
2105                   are using very old DNS software, you
2106                   may need to set it to <strong class="userinput"><code>yes</code></strong>.
2107                 </p></dd>
2108 <dt><span class="term"><span><strong class="command">deallocate-on-exit</strong></span></span></dt>
2109 <dd><p>
2110                   This option was used in <acronym class="acronym">BIND</acronym>
2111                   8 to enable checking
2112                   for memory leaks on exit. <acronym class="acronym">BIND</acronym> 9 ignores the option and always performs
2113                   the checks.
2114                 </p></dd>
2115 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
2116 <dd>
2117 <p>
2118                   If <strong class="userinput"><code>yes</code></strong>, then the
2119                   server treats all zones as if they are doing zone transfers
2120                   across
2121                   a dial-on-demand dialup link, which can be brought up by
2122                   traffic
2123                   originating from this server. This has different effects
2124                   according
2125                   to zone type and concentrates the zone maintenance so that
2126                   it all
2127                   happens in a short interval, once every <span><strong class="command">heartbeat-interval</strong></span> and
2128                   hopefully during the one call. It also suppresses some of
2129                   the normal
2130                   zone maintenance traffic. The default is <strong class="userinput"><code>no</code></strong>.
2131                 </p>
2132 <p>
2133                   The <span><strong class="command">dialup</strong></span> option
2134                   may also be specified in the <span><strong class="command">view</strong></span> and
2135                   <span><strong class="command">zone</strong></span> statements,
2136                   in which case it overrides the global <span><strong class="command">dialup</strong></span>
2137                   option.
2138                 </p>
2139 <p>
2140                   If the zone is a master zone, then the server will send out a
2141                   NOTIFY
2142                   request to all the slaves (default). This should trigger the
2143                   zone serial
2144                   number check in the slave (providing it supports NOTIFY)
2145                   allowing the slave
2146                   to verify the zone while the connection is active.
2147                   The set of servers to which NOTIFY is sent can be controlled
2148                   by
2149                   <span><strong class="command">notify</strong></span> and <span><strong class="command">also-notify</strong></span>.
2150                 </p>
2151 <p>
2152                   If the
2153                   zone is a slave or stub zone, then the server will suppress
2154                   the regular
2155                   "zone up to date" (refresh) queries and only perform them
2156                   when the
2157                   <span><strong class="command">heartbeat-interval</strong></span> expires in
2158                   addition to sending
2159                   NOTIFY requests.
2160                 </p>
2161 <p>
2162                   Finer control can be achieved by using
2163                   <strong class="userinput"><code>notify</code></strong> which only sends NOTIFY
2164                   messages,
2165                   <strong class="userinput"><code>notify-passive</code></strong> which sends NOTIFY
2166                   messages and
2167                   suppresses the normal refresh queries, <strong class="userinput"><code>refresh</code></strong>
2168                   which suppresses normal refresh processing and sends refresh
2169                   queries
2170                   when the <span><strong class="command">heartbeat-interval</strong></span>
2171                   expires, and
2172                   <strong class="userinput"><code>passive</code></strong> which just disables normal
2173                   refresh
2174                   processing.
2175                 </p>
2176 <div class="informaltable"><table border="1">
2177 <colgroup>
2178 <col>
2179 <col>
2180 <col>
2181 <col>
2182 </colgroup>
2183 <tbody>
2184 <tr>
2185 <td>
2186                           <p>
2187                             dialup mode
2188                           </p>
2189                         </td>
2190 <td>
2191                           <p>
2192                             normal refresh
2193                           </p>
2194                         </td>
2195 <td>
2196                           <p>
2197                             heart-beat refresh
2198                           </p>
2199                         </td>
2200 <td>
2201                           <p>
2202                             heart-beat notify
2203                           </p>
2204                         </td>
2205 </tr>
2206 <tr>
2207 <td>
2208                           <p><span><strong class="command">no</strong></span> (default)</p>
2209                         </td>
2210 <td>
2211                           <p>
2212                             yes
2213                           </p>
2214                         </td>
2215 <td>
2216                           <p>
2217                             no
2218                           </p>
2219                         </td>
2220 <td>
2221                           <p>
2222                             no
2223                           </p>
2224                         </td>
2225 </tr>
2226 <tr>
2227 <td>
2228                           <p><span><strong class="command">yes</strong></span></p>
2229                         </td>
2230 <td>
2231                           <p>
2232                             no
2233                           </p>
2234                         </td>
2235 <td>
2236                           <p>
2237                             yes
2238                           </p>
2239                         </td>
2240 <td>
2241                           <p>
2242                             yes
2243                           </p>
2244                         </td>
2245 </tr>
2246 <tr>
2247 <td>
2248                           <p><span><strong class="command">notify</strong></span></p>
2249                         </td>
2250 <td>
2251                           <p>
2252                             yes
2253                           </p>
2254                         </td>
2255 <td>
2256                           <p>
2257                             no
2258                           </p>
2259                         </td>
2260 <td>
2261                           <p>
2262                             yes
2263                           </p>
2264                         </td>
2265 </tr>
2266 <tr>
2267 <td>
2268                           <p><span><strong class="command">refresh</strong></span></p>
2269                         </td>
2270 <td>
2271                           <p>
2272                             no
2273                           </p>
2274                         </td>
2275 <td>
2276                           <p>
2277                             yes
2278                           </p>
2279                         </td>
2280 <td>
2281                           <p>
2282                             no
2283                           </p>
2284                         </td>
2285 </tr>
2286 <tr>
2287 <td>
2288                           <p><span><strong class="command">passive</strong></span></p>
2289                         </td>
2290 <td>
2291                           <p>
2292                             no
2293                           </p>
2294                         </td>
2295 <td>
2296                           <p>
2297                             no
2298                           </p>
2299                         </td>
2300 <td>
2301                           <p>
2302                             no
2303                           </p>
2304                         </td>
2305 </tr>
2306 <tr>
2307 <td>
2308                           <p><span><strong class="command">notify-passive</strong></span></p>
2309                         </td>
2310 <td>
2311                           <p>
2312                             no
2313                           </p>
2314                         </td>
2315 <td>
2316                           <p>
2317                             no
2318                           </p>
2319                         </td>
2320 <td>
2321                           <p>
2322                             yes
2323                           </p>
2324                         </td>
2325 </tr>
2326 </tbody>
2327 </table></div>
2328 <p>
2329                   Note that normal NOTIFY processing is not affected by
2330                   <span><strong class="command">dialup</strong></span>.
2331                 </p>
2332 </dd>
2333 <dt><span class="term"><span><strong class="command">fake-iquery</strong></span></span></dt>
2334 <dd><p>
2335                   In <acronym class="acronym">BIND</acronym> 8, this option
2336                   enabled simulating the obsolete DNS query type
2337                   IQUERY. <acronym class="acronym">BIND</acronym> 9 never does
2338                   IQUERY simulation.
2339                 </p></dd>
2340 <dt><span class="term"><span><strong class="command">fetch-glue</strong></span></span></dt>
2341 <dd><p>
2342                   This option is obsolete.
2343                   In BIND 8, <strong class="userinput"><code>fetch-glue yes</code></strong>
2344                   caused the server to attempt to fetch glue resource records
2345                   it
2346                   didn't have when constructing the additional
2347                   data section of a response.  This is now considered a bad
2348                   idea
2349                   and BIND 9 never does it.
2350                 </p></dd>
2351 <dt><span class="term"><span><strong class="command">flush-zones-on-shutdown</strong></span></span></dt>
2352 <dd><p>
2353                   When the nameserver exits due receiving SIGTERM,
2354                   flush or do not flush any pending zone writes.  The default
2355                   is
2356                   <span><strong class="command">flush-zones-on-shutdown</strong></span> <strong class="userinput"><code>no</code></strong>.
2357                 </p></dd>
2358 <dt><span class="term"><span><strong class="command">has-old-clients</strong></span></span></dt>
2359 <dd><p>
2360                   This option was incorrectly implemented
2361                   in <acronym class="acronym">BIND</acronym> 8, and is ignored by <acronym class="acronym">BIND</acronym> 9.
2362                   To achieve the intended effect
2363                   of
2364                   <span><strong class="command">has-old-clients</strong></span> <strong class="userinput"><code>yes</code></strong>, specify
2365                   the two separate options <span><strong class="command">auth-nxdomain</strong></span> <strong class="userinput"><code>yes</code></strong>
2366                   and <span><strong class="command">rfc2308-type1</strong></span> <strong class="userinput"><code>no</code></strong> instead.
2367                 </p></dd>
2368 <dt><span class="term"><span><strong class="command">host-statistics</strong></span></span></dt>
2369 <dd><p>
2370                   In BIND 8, this enables keeping of
2371                   statistics for every host that the name server interacts
2372                   with.
2373                   Not implemented in BIND 9.
2374                 </p></dd>
2375 <dt><span class="term"><span><strong class="command">maintain-ixfr-base</strong></span></span></dt>
2376 <dd><p>
2377                   <span class="emphasis"><em>This option is obsolete</em></span>.
2378                   It was used in <acronym class="acronym">BIND</acronym> 8 to
2379                   determine whether a transaction log was
2380                   kept for Incremental Zone Transfer. <acronym class="acronym">BIND</acronym> 9 maintains a transaction
2381                   log whenever possible.  If you need to disable outgoing
2382                   incremental zone
2383                   transfers, use <span><strong class="command">provide-ixfr</strong></span> <strong class="userinput"><code>no</code></strong>.
2384                 </p></dd>
2385 <dt><span class="term"><span><strong class="command">minimal-responses</strong></span></span></dt>
2386 <dd><p>
2387                   If <strong class="userinput"><code>yes</code></strong>, then when generating
2388                   responses the server will only add records to the authority
2389                   and additional data sections when they are required (e.g.
2390                   delegations, negative responses).  This may improve the
2391                   performance of the server.
2392                   The default is <strong class="userinput"><code>no</code></strong>.
2393                 </p></dd>
2394 <dt><span class="term"><span><strong class="command">multiple-cnames</strong></span></span></dt>
2395 <dd><p>
2396                   This option was used in <acronym class="acronym">BIND</acronym> 8 to allow
2397                   a domain name to have multiple CNAME records in violation of
2398                   the DNS standards.  <acronym class="acronym">BIND</acronym> 9.2 onwards
2399                   always strictly enforces the CNAME rules both in master
2400                   files and dynamic updates.
2401                 </p></dd>
2402 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
2403 <dd>
2404 <p>
2405                   If <strong class="userinput"><code>yes</code></strong> (the default),
2406                   DNS NOTIFY messages are sent when a zone the server is
2407                   authoritative for
2408                   changes, see <a href="Bv9ARM.ch04.html#notify" title="Notify">the section called &#8220;Notify&#8221;</a>.  The messages are
2409                   sent to the
2410                   servers listed in the zone's NS records (except the master
2411                   server identified
2412                   in the SOA MNAME field), and to any servers listed in the
2413                   <span><strong class="command">also-notify</strong></span> option.
2414                 </p>
2415 <p>
2416                   If <strong class="userinput"><code>master-only</code></strong>, notifies are only
2417                   sent
2418                   for master zones.
2419                   If <strong class="userinput"><code>explicit</code></strong>, notifies are sent only
2420                   to
2421                   servers explicitly listed using <span><strong class="command">also-notify</strong></span>.
2422                   If <strong class="userinput"><code>no</code></strong>, no notifies are sent.
2423                 </p>
2424 <p>
2425                   The <span><strong class="command">notify</strong></span> option may also be
2426                   specified in the <span><strong class="command">zone</strong></span>
2427                   statement,
2428                   in which case it overrides the <span><strong class="command">options notify</strong></span> statement.
2429                   It would only be necessary to turn off this option if it
2430                   caused slaves
2431                   to crash.
2432                 </p>
2433 </dd>
2434 <dt><span class="term"><span><strong class="command">recursion</strong></span></span></dt>
2435 <dd><p>
2436                   If <strong class="userinput"><code>yes</code></strong>, and a
2437                   DNS query requests recursion, then the server will attempt
2438                   to do
2439                   all the work required to answer the query. If recursion is
2440                   off
2441                   and the server does not already know the answer, it will
2442                   return a
2443                   referral response. The default is
2444                   <strong class="userinput"><code>yes</code></strong>.
2445                   Note that setting <span><strong class="command">recursion no</strong></span> does not prevent
2446                   clients from getting data from the server's cache; it only
2447                   prevents new data from being cached as an effect of client
2448                   queries.
2449                   Caching may still occur as an effect the server's internal
2450                   operation, such as NOTIFY address lookups.
2451                   See also <span><strong class="command">fetch-glue</strong></span> above.
2452                 </p></dd>
2453 <dt><span class="term"><span><strong class="command">rfc2308-type1</strong></span></span></dt>
2454 <dd>
2455 <p>
2456                   Setting this to <strong class="userinput"><code>yes</code></strong> will
2457                   cause the server to send NS records along with the SOA
2458                   record for negative
2459                   answers. The default is <strong class="userinput"><code>no</code></strong>.
2460                 </p>
2461 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
2462 <h3 class="title">Note</h3>
2463 <p>
2464                     Not yet implemented in <acronym class="acronym">BIND</acronym>
2465                     9.
2466                   </p>
2467 </div>
2468 </dd>
2469 <dt><span class="term"><span><strong class="command">use-id-pool</strong></span></span></dt>
2470 <dd><p>
2471                   <span class="emphasis"><em>This option is obsolete</em></span>.
2472                   <acronym class="acronym">BIND</acronym> 9 always allocates query
2473                   IDs from a pool.
2474                 </p></dd>
2475 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
2476 <dd><p>
2477                   If <strong class="userinput"><code>yes</code></strong>, the server will collect
2478                   statistical data on all zones (unless specifically turned
2479                   off
2480                   on a per-zone basis by specifying <span><strong class="command">zone-statistics no</strong></span>
2481                   in the <span><strong class="command">zone</strong></span> statement).
2482                   These statistics may be accessed
2483                   using <span><strong class="command">rndc stats</strong></span>, which will
2484                   dump them to the file listed
2485                   in the <span><strong class="command">statistics-file</strong></span>.  See
2486                   also <a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
2487                 </p></dd>
2488 <dt><span class="term"><span><strong class="command">use-ixfr</strong></span></span></dt>
2489 <dd><p>
2490                   <span class="emphasis"><em>This option is obsolete</em></span>.
2491                   If you need to disable IXFR to a particular server or
2492                   servers, see
2493                   the information on the <span><strong class="command">provide-ixfr</strong></span> option
2494                   in <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
2495             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
2496             Usage&#8221;</a>.
2497                   See also
2498                   <a href="Bv9ARM.ch04.html#incremental_zone_transfers" title="Incremental Zone Transfers (IXFR)">the section called &#8220;Incremental Zone Transfers (IXFR)&#8221;</a>.
2499                 </p></dd>
2500 <dt><span class="term"><span><strong class="command">provide-ixfr</strong></span></span></dt>
2501 <dd><p>
2502                   See the description of
2503                   <span><strong class="command">provide-ixfr</strong></span> in
2504                   <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
2505             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
2506             Usage&#8221;</a>.
2507                 </p></dd>
2508 <dt><span class="term"><span><strong class="command">request-ixfr</strong></span></span></dt>
2509 <dd><p>
2510                   See the description of
2511                   <span><strong class="command">request-ixfr</strong></span> in
2512                   <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
2513             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
2514             Usage&#8221;</a>.
2515                 </p></dd>
2516 <dt><span class="term"><span><strong class="command">treat-cr-as-space</strong></span></span></dt>
2517 <dd><p>
2518                   This option was used in <acronym class="acronym">BIND</acronym>
2519                   8 to make
2520                   the server treat carriage return ("<span><strong class="command">\r</strong></span>") characters the same way
2521                   as a space or tab character,
2522                   to facilitate loading of zone files on a UNIX system that
2523                   were generated
2524                   on an NT or DOS machine. In <acronym class="acronym">BIND</acronym> 9, both UNIX "<span><strong class="command">\n</strong></span>"
2525                   and NT/DOS "<span><strong class="command">\r\n</strong></span>" newlines
2526                   are always accepted,
2527                   and the option is ignored.
2528                 </p></dd>
2529 <dt>
2530 <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>
2531 </dt>
2532 <dd>
2533 <p>
2534                   These options control the behavior of an authoritative
2535                   server when
2536                   answering queries which have additional data, or when
2537                   following CNAME
2538                   and DNAME chains.
2539                 </p>
2540 <p>
2541                   When both of these options are set to <strong class="userinput"><code>yes</code></strong>
2542                   (the default) and a
2543                   query is being answered from authoritative data (a zone
2544                   configured into the server), the additional data section of
2545                   the
2546                   reply will be filled in using data from other authoritative
2547                   zones
2548                   and from the cache.  In some situations this is undesirable,
2549                   such
2550                   as when there is concern over the correctness of the cache,
2551                   or
2552                   in servers where slave zones may be added and modified by
2553                   untrusted third parties.  Also, avoiding
2554                   the search for this additional data will speed up server
2555                   operations
2556                   at the possible expense of additional queries to resolve
2557                   what would
2558                   otherwise be provided in the additional section.
2559                 </p>
2560 <p>
2561                   For example, if a query asks for an MX record for host <code class="literal">foo.example.com</code>,
2562                   and the record found is "<code class="literal">MX 10 mail.example.net</code>", normally the address
2563                   records (A and AAAA) for <code class="literal">mail.example.net</code> will be provided as well,
2564                   if known, even though they are not in the example.com zone.
2565                   Setting these options to <span><strong class="command">no</strong></span>
2566                   disables this behavior and makes
2567                   the server only search for additional data in the zone it
2568                   answers from.
2569                 </p>
2570 <p>
2571                   These options are intended for use in authoritative-only
2572                   servers, or in authoritative-only views.  Attempts to set
2573                   them to <span><strong class="command">no</strong></span> without also
2574                   specifying
2575                   <span><strong class="command">recursion no</strong></span> will cause the
2576                   server to
2577                   ignore the options and log a warning message.
2578                 </p>
2579 <p>
2580                   Specifying <span><strong class="command">additional-from-cache no</strong></span> actually
2581                   disables the use of the cache not only for additional data
2582                   lookups
2583                   but also when looking up the answer.  This is usually the
2584                   desired
2585                   behavior in an authoritative-only server where the
2586                   correctness of
2587                   the cached data is an issue.
2588                 </p>
2589 <p>
2590                   When a name server is non-recursively queried for a name
2591                   that is not
2592                   below the apex of any served zone, it normally answers with
2593                   an
2594                   "upwards referral" to the root servers or the servers of
2595                   some other
2596                   known parent of the query name.  Since the data in an
2597                   upwards referral
2598                   comes from the cache, the server will not be able to provide
2599                   upwards
2600                   referrals when <span><strong class="command">additional-from-cache no</strong></span>
2601                   has been specified.  Instead, it will respond to such
2602                   queries
2603                   with REFUSED.  This should not cause any problems since
2604                   upwards referrals are not required for the resolution
2605                   process.
2606                 </p>
2607 </dd>
2608 <dt><span class="term"><span><strong class="command">match-mapped-addresses</strong></span></span></dt>
2609 <dd><p>
2610                   If <strong class="userinput"><code>yes</code></strong>, then an
2611                   IPv4-mapped IPv6 address will match any address match
2612                   list entries that match the corresponding IPv4 address.
2613                   Enabling this option is sometimes useful on IPv6-enabled
2614                   Linux
2615                   systems, to work around a kernel quirk that causes IPv4
2616                   TCP connections such as zone transfers to be accepted
2617                   on an IPv6 socket using mapped addresses, causing
2618                   address match lists designed for IPv4 to fail to match.
2619                   The use of this option for any other purpose is discouraged.
2620                 </p></dd>
2621 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
2622 <dd>
2623 <p>
2624                   When <strong class="userinput"><code>yes</code></strong> and the server loads a new version of a master
2625                   zone from its zone file or receives a new version of a slave
2626                   file by a non-incremental zone transfer, it will compare
2627                   the new version to the previous one and calculate a set
2628                   of differences.  The differences are then logged in the
2629                   zone's journal file such that the changes can be transmitted
2630                   to downstream slaves as an incremental zone transfer.
2631                 </p>
2632 <p>
2633                   By allowing incremental zone transfers to be used for
2634                   non-dynamic zones, this option saves bandwidth at the
2635                   expense of increased CPU and memory consumption at the
2636                   master.
2637                   In particular, if the new version of a zone is completely
2638                   different from the previous one, the set of differences
2639                   will be of a size comparable to the combined size of the
2640                   old and new zone version, and the server will need to
2641                   temporarily allocate memory to hold this complete
2642                   difference set.
2643                 </p>
2644 <p><span><strong class="command">ixfr-from-differences</strong></span>
2645                   also accepts <span><strong class="command">master</strong></span> and
2646                   <span><strong class="command">slave</strong></span> at the view and options
2647                   levels which causes
2648                   <span><strong class="command">ixfr-from-differences</strong></span> to apply to
2649                   all <span><strong class="command">master</strong></span> or
2650                   <span><strong class="command">slave</strong></span> zones respectively.
2651                 </p>
2652 </dd>
2653 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
2654 <dd><p>
2655                   This should be set when you have multiple masters for a zone
2656                   and the
2657                   addresses refer to different machines.  If <strong class="userinput"><code>yes</code></strong>, named will
2658                   not log
2659                   when the serial number on the master is less than what named
2660                   currently
2661                   has.  The default is <strong class="userinput"><code>no</code></strong>.
2662                 </p></dd>
2663 <dt><span class="term"><span><strong class="command">dnssec-enable</strong></span></span></dt>
2664 <dd><p>
2665                   Enable DNSSEC support in named.  Unless set to <strong class="userinput"><code>yes</code></strong>,
2666                   named behaves as if it does not support DNSSEC.
2667                   The default is <strong class="userinput"><code>yes</code></strong>.
2668                 </p></dd>
2669 <dt><span class="term"><span><strong class="command">dnssec-validation</strong></span></span></dt>
2670 <dd><p>
2671                   Enable DNSSEC validation in named.
2672                   Note <span><strong class="command">dnssec-enable</strong></span> also needs to be
2673                   set to <strong class="userinput"><code>yes</code></strong> to be effective.
2674                   The default is <strong class="userinput"><code>no</code></strong>.
2675                 </p></dd>
2676 <dt><span class="term"><span><strong class="command">dnssec-accept-expired</strong></span></span></dt>
2677 <dd><p>
2678                   Accept expired signatures when verifying DNSSEC signatures.
2679                   The default is <strong class="userinput"><code>no</code></strong>.
2680                   Setting this option to "yes" leaves named vulnerable to replay attacks.
2681                 </p></dd>
2682 <dt><span class="term"><span><strong class="command">querylog</strong></span></span></dt>
2683 <dd><p>
2684                   Specify whether query logging should be started when named
2685                   starts.
2686                   If <span><strong class="command">querylog</strong></span> is not specified,
2687                   then the query logging
2688                   is determined by the presence of the logging category <span><strong class="command">queries</strong></span>.
2689                 </p></dd>
2690 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
2691 <dd>
2692 <p>
2693                   This option is used to restrict the character set and syntax
2694                   of
2695                   certain domain names in master files and/or DNS responses
2696                   received
2697                   from the network.  The default varies according to usage
2698                   area.  For
2699                   <span><strong class="command">master</strong></span> zones the default is <span><strong class="command">fail</strong></span>.
2700                   For <span><strong class="command">slave</strong></span> zones the default
2701                   is <span><strong class="command">warn</strong></span>.
2702                   For answers received from the network (<span><strong class="command">response</strong></span>)
2703                   the default is <span><strong class="command">ignore</strong></span>.
2704                 </p>
2705 <p>
2706                   The rules for legal hostnames and mail domains are derived
2707                   from RFC 952 and RFC 821 as modified by RFC 1123.
2708                 </p>
2709 <p><span><strong class="command">check-names</strong></span>
2710                   applies to the owner names of A, AAA and MX records.
2711                   It also applies to the domain names in the RDATA of NS, SOA
2712                   and MX records.
2713                   It also applies to the RDATA of PTR records where the owner
2714                   name indicated that it is a reverse lookup of a hostname
2715                   (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, or IP6.INT).
2716                 </p>
2717 </dd>
2718 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
2719 <dd><p>
2720                   Check whether the MX record appears to refer to a IP address.
2721                   The default is to <span><strong class="command">warn</strong></span>.  Other possible
2722                   values are <span><strong class="command">fail</strong></span> and
2723                   <span><strong class="command">ignore</strong></span>.
2724                 </p></dd>
2725 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
2726 <dd><p>
2727                   This option is used to check for non-terminal wildcards.
2728                   The use of non-terminal wildcards is almost always as a
2729                   result of a failure
2730                   to understand the wildcard matching algorithm (RFC 1034).
2731                   This option
2732                   affects master zones.  The default (<span><strong class="command">yes</strong></span>) is to check
2733                   for non-terminal wildcards and issue a warning.
2734                 </p></dd>
2735 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
2736 <dd><p>
2737                   Perform post load zone integrity checks on master
2738                   zones.  This checks that MX and SRV records refer
2739                   to address (A or AAAA) records and that glue
2740                   address records exist for delegated zones.  For
2741                   MX and SRV records only in-zone hostnames are
2742                   checked (for out-of-zone hostnames use named-checkzone).
2743                   For NS records only names below top of zone are
2744                   checked (for out-of-zone names and glue consistency
2745                   checks use named-checkzone).  The default is
2746                   <span><strong class="command">yes</strong></span>.
2747                 </p></dd>
2748 <dt><span class="term"><span><strong class="command">check-mx-cname</strong></span></span></dt>
2749 <dd><p>
2750                   If <span><strong class="command">check-integrity</strong></span> is set then
2751                   fail, warn or ignore MX records that refer
2752                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
2753                 </p></dd>
2754 <dt><span class="term"><span><strong class="command">check-srv-cname</strong></span></span></dt>
2755 <dd><p>
2756                   If <span><strong class="command">check-integrity</strong></span> is set then
2757                   fail, warn or ignore SRV records that refer
2758                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
2759                 </p></dd>
2760 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
2761 <dd><p>
2762                   When performing integrity checks, also check that
2763                   sibling glue exists.  The default is <span><strong class="command">yes</strong></span>.
2764                 </p></dd>
2765 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
2766 <dd><p>
2767                   When returning authoritative negative responses to
2768                   SOA queries set the TTL of the SOA recored returned in
2769                   the authority section to zero.
2770                   The default is <span><strong class="command">yes</strong></span>.
2771                 </p></dd>
2772 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl-cache</strong></span></span></dt>
2773 <dd><p>
2774                   When caching a negative response to a SOA query
2775                   set the TTL to zero.
2776                   The default is <span><strong class="command">no</strong></span>.
2777                 </p></dd>
2778 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
2779 <dd><p>
2780                   When regenerating the RRSIGs following a UPDATE
2781                   request to a secure zone, check the KSK flag on
2782                   the DNSKEY RR to determine if this key should be
2783                   used to generate the RRSIG.  This flag is ignored
2784                   if there are not DNSKEY RRs both with and without
2785                   a KSK.
2786                   The default is <span><strong class="command">yes</strong></span>.
2787                 </p></dd>
2788 </dl></div>
2789 </div>
2790 <div class="sect3" lang="en">
2791 <div class="titlepage"><div><div><h4 class="title">
2792 <a name="id2580536"></a>Forwarding</h4></div></div></div>
2793 <p>
2794             The forwarding facility can be used to create a large site-wide
2795             cache on a few servers, reducing traffic over links to external
2796             name servers. It can also be used to allow queries by servers that
2797             do not have direct access to the Internet, but wish to look up
2798             exterior
2799             names anyway. Forwarding occurs only on those queries for which
2800             the server is not authoritative and does not have the answer in
2801             its cache.
2802           </p>
2803 <div class="variablelist"><dl>
2804 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
2805 <dd><p>
2806                   This option is only meaningful if the
2807                   forwarders list is not empty. A value of <code class="varname">first</code>,
2808                   the default, causes the server to query the forwarders
2809                   first &#8212; and
2810                   if that doesn't answer the question, the server will then
2811                   look for
2812                   the answer itself. If <code class="varname">only</code> is
2813                   specified, the
2814                   server will only query the forwarders.
2815                 </p></dd>
2816 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
2817 <dd><p>
2818                   Specifies the IP addresses to be used
2819                   for forwarding. The default is the empty list (no
2820                   forwarding).
2821                 </p></dd>
2822 </dl></div>
2823 <p>
2824             Forwarding can also be configured on a per-domain basis, allowing
2825             for the global forwarding options to be overridden in a variety
2826             of ways. You can set particular domains to use different
2827             forwarders,
2828             or have a different <span><strong class="command">forward only/first</strong></span> behavior,
2829             or not forward at all, see <a href="Bv9ARM.ch06.html#zone_statement_grammar" title="zone
2830             Statement Grammar">the section called &#8220;<span><strong class="command">zone</strong></span>
2831             Statement Grammar&#8221;</a>.
2832           </p>
2833 </div>
2834 <div class="sect3" lang="en">
2835 <div class="titlepage"><div><div><h4 class="title">
2836 <a name="id2580595"></a>Dual-stack Servers</h4></div></div></div>
2837 <p>
2838             Dual-stack servers are used as servers of last resort to work
2839             around
2840             problems in reachability due the lack of support for either IPv4
2841             or IPv6
2842             on the host machine.
2843           </p>
2844 <div class="variablelist"><dl>
2845 <dt><span class="term"><span><strong class="command">dual-stack-servers</strong></span></span></dt>
2846 <dd><p>
2847                   Specifies host names or addresses of machines with access to
2848                   both IPv4 and IPv6 transports. If a hostname is used, the
2849                   server must be able
2850                   to resolve the name using only the transport it has.  If the
2851                   machine is dual
2852                   stacked, then the <span><strong class="command">dual-stack-servers</strong></span> have no effect unless
2853                   access to a transport has been disabled on the command line
2854                   (e.g. <span><strong class="command">named -4</strong></span>).
2855                 </p></dd>
2856 </dl></div>
2857 </div>
2858 <div class="sect3" lang="en">
2859 <div class="titlepage"><div><div><h4 class="title">
2860 <a name="access_control"></a>Access Control</h4></div></div></div>
2861 <p>
2862             Access to the server can be restricted based on the IP address
2863             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
2864             details on how to specify IP address lists.
2865           </p>
2866 <div class="variablelist"><dl>
2867 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
2868 <dd><p>
2869                   Specifies which hosts are allowed to
2870                   notify this server, a slave, of zone changes in addition
2871                   to the zone masters.
2872                   <span><strong class="command">allow-notify</strong></span> may also be
2873                   specified in the
2874                   <span><strong class="command">zone</strong></span> statement, in which case
2875                   it overrides the
2876                   <span><strong class="command">options allow-notify</strong></span>
2877                   statement.  It is only meaningful
2878                   for a slave zone.  If not specified, the default is to
2879                   process notify messages
2880                   only from a zone's master.
2881                 </p></dd>
2882 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
2883 <dd>
2884 <p>
2885                   Specifies which hosts are allowed to ask ordinary
2886                   DNS questions. <span><strong class="command">allow-query</strong></span> may
2887                   also be specified in the <span><strong class="command">zone</strong></span>
2888                   statement, in which case it overrides the
2889                   <span><strong class="command">options allow-query</strong></span> statement.
2890                   If not specified, the default is to allow queries
2891                   from all hosts.
2892                 </p>
2893 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
2894 <h3 class="title">Note</h3>
2895 <p>
2896                     <span><strong class="command">allow-query-cache</strong></span> is now
2897                     used to specify access to the cache.
2898                   </p>
2899 </div>
2900 </dd>
2901 <dt><span class="term"><span><strong class="command">allow-query-cache</strong></span></span></dt>
2902 <dd><p>
2903                   Specifies which hosts are allowed to get answers
2904                   from the cache.  If <span><strong class="command">allow-query-cache</strong></span>
2905                   is not set then <span><strong class="command">allow-recursion</strong></span>
2906                   is used if set, otherwise <span><strong class="command">allow-query</strong></span>
2907                   is used if set, otherwise the default
2908                   (<span><strong class="command">localnets;</strong></span>
2909                   <span><strong class="command">localhost;</strong></span>) is used.
2910                 </p></dd>
2911 <dt><span class="term"><span><strong class="command">allow-recursion</strong></span></span></dt>
2912 <dd><p>
2913                   Specifies which hosts are allowed to make recursive
2914                   queries through this server. If
2915                   <span><strong class="command">allow-recursion</strong></span> is not set
2916                   then <span><strong class="command">allow-query-cache</strong></span> is
2917                   used if set, otherwise <span><strong class="command">allow-query</strong></span>
2918                   is used if set, otherwise the default
2919                   (<span><strong class="command">localnets;</strong></span>
2920                   <span><strong class="command">localhost;</strong></span>) is used.
2921                 </p></dd>
2922 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
2923 <dd><p>
2924                   Specifies which hosts are allowed to
2925                   submit Dynamic DNS updates for master zones. The default is
2926                   to deny
2927                   updates from all hosts.  Note that allowing updates based
2928                   on the requestor's IP address is insecure; see
2929                   <a href="Bv9ARM.ch07.html#dynamic_update_security" title="Dynamic Update Security">the section called &#8220;Dynamic Update Security&#8221;</a> for details.
2930                 </p></dd>
2931 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
2932 <dd>
2933 <p>
2934                   Specifies which hosts are allowed to
2935                   submit Dynamic DNS updates to slave zones to be forwarded to
2936                   the
2937                   master.  The default is <strong class="userinput"><code>{ none; }</code></strong>,
2938                   which
2939                   means that no update forwarding will be performed.  To
2940                   enable
2941                   update forwarding, specify
2942                   <strong class="userinput"><code>allow-update-forwarding { any; };</code></strong>.
2943                   Specifying values other than <strong class="userinput"><code>{ none; }</code></strong> or
2944                   <strong class="userinput"><code>{ any; }</code></strong> is usually
2945                   counterproductive, since
2946                   the responsibility for update access control should rest
2947                   with the
2948                   master server, not the slaves.
2949                 </p>
2950 <p>
2951                   Note that enabling the update forwarding feature on a slave
2952                   server
2953                   may expose master servers relying on insecure IP address
2954                   based
2955                   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>
2956                   for more details.
2957                 </p>
2958 </dd>
2959 <dt><span class="term"><span><strong class="command">allow-v6-synthesis</strong></span></span></dt>
2960 <dd><p>
2961                   This option was introduced for the smooth transition from
2962                   AAAA
2963                   to A6 and from "nibble labels" to binary labels.
2964                   However, since both A6 and binary labels were then
2965                   deprecated,
2966                   this option was also deprecated.
2967                   It is now ignored with some warning messages.
2968                 </p></dd>
2969 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
2970 <dd><p>
2971                   Specifies which hosts are allowed to
2972                   receive zone transfers from the server. <span><strong class="command">allow-transfer</strong></span> may
2973                   also be specified in the <span><strong class="command">zone</strong></span>
2974                   statement, in which
2975                   case it overrides the <span><strong class="command">options allow-transfer</strong></span> statement.
2976                   If not specified, the default is to allow transfers to all
2977                   hosts.
2978                 </p></dd>
2979 <dt><span class="term"><span><strong class="command">blackhole</strong></span></span></dt>
2980 <dd><p>
2981                   Specifies a list of addresses that the
2982                   server will not accept queries from or use to resolve a
2983                   query. Queries
2984                   from these addresses will not be responded to. The default
2985                   is <strong class="userinput"><code>none</code></strong>.
2986                 </p></dd>
2987 </dl></div>
2988 </div>
2989 <div class="sect3" lang="en">
2990 <div class="titlepage"><div><div><h4 class="title">
2991 <a name="id2581153"></a>Interfaces</h4></div></div></div>
2992 <p>
2993             The interfaces and ports that the server will answer queries
2994             from may be specified using the <span><strong class="command">listen-on</strong></span> option. <span><strong class="command">listen-on</strong></span> takes
2995             an optional port, and an <code class="varname">address_match_list</code>.
2996             The server will listen on all interfaces allowed by the address
2997             match list. If a port is not specified, port 53 will be used.
2998           </p>
2999 <p>
3000             Multiple <span><strong class="command">listen-on</strong></span> statements are
3001             allowed.
3002             For example,
3003           </p>
3004 <pre class="programlisting">listen-on { 5.6.7.8; };
3005 listen-on port 1234 { !1.2.3.4; 1.2/16; };
3006 </pre>
3007 <p>
3008             will enable the name server on port 53 for the IP address
3009             5.6.7.8, and on port 1234 of an address on the machine in net
3010             1.2 that is not 1.2.3.4.
3011           </p>
3012 <p>
3013             If no <span><strong class="command">listen-on</strong></span> is specified, the
3014             server will listen on port 53 on all interfaces.
3015           </p>
3016 <p>
3017             The <span><strong class="command">listen-on-v6</strong></span> option is used to
3018             specify the interfaces and the ports on which the server will
3019             listen
3020             for incoming queries sent using IPv6.
3021           </p>
3022 <p>
3023             When </p>
3024 <pre class="programlisting">{ any; }</pre>
3025 <p> is
3026             specified
3027             as the <code class="varname">address_match_list</code> for the
3028             <span><strong class="command">listen-on-v6</strong></span> option,
3029             the server does not bind a separate socket to each IPv6 interface
3030             address as it does for IPv4 if the operating system has enough API
3031             support for IPv6 (specifically if it conforms to RFC 3493 and RFC
3032             3542).
3033             Instead, it listens on the IPv6 wildcard address.
3034             If the system only has incomplete API support for IPv6, however,
3035             the behavior is the same as that for IPv4.
3036           </p>
3037 <p>
3038             A list of particular IPv6 addresses can also be specified, in
3039             which case
3040             the server listens on a separate socket for each specified
3041             address,
3042             regardless of whether the desired API is supported by the system.
3043           </p>
3044 <p>
3045             Multiple <span><strong class="command">listen-on-v6</strong></span> options can
3046             be used.
3047             For example,
3048           </p>
3049 <pre class="programlisting">listen-on-v6 { any; };
3050 listen-on-v6 port 1234 { !2001:db8::/32; any; };
3051 </pre>
3052 <p>
3053             will enable the name server on port 53 for any IPv6 addresses
3054             (with a single wildcard socket),
3055             and on port 1234 of IPv6 addresses that is not in the prefix
3056             2001:db8::/32 (with separate sockets for each matched address.)
3057           </p>
3058 <p>
3059             To make the server not listen on any IPv6 address, use
3060           </p>
3061 <pre class="programlisting">listen-on-v6 { none; };
3062 </pre>
3063 <p>
3064             If no <span><strong class="command">listen-on-v6</strong></span> option is
3065             specified,
3066             the server will not listen on any IPv6 address.
3067           </p>
3068 </div>
3069 <div class="sect3" lang="en">
3070 <div class="titlepage"><div><div><h4 class="title">
3071 <a name="id2581241"></a>Query Address</h4></div></div></div>
3072 <p>
3073             If the server doesn't know the answer to a question, it will
3074             query other name servers. <span><strong class="command">query-source</strong></span> specifies
3075             the address and port used for such queries. For queries sent over
3076             IPv6, there is a separate <span><strong class="command">query-source-v6</strong></span> option.
3077             If <span><strong class="command">address</strong></span> is <span><strong class="command">*</strong></span> (asterisk) or is omitted,
3078             a wildcard IP address (<span><strong class="command">INADDR_ANY</strong></span>)
3079             will be used.
3080             If <span><strong class="command">port</strong></span> is <span><strong class="command">*</strong></span> or is omitted,
3081             a random unprivileged port number is picked up and will be
3082             used for each query.
3083             It is generally strongly discouraged to
3084             specify a particular port for the
3085             <span><strong class="command">query-source</strong></span> or
3086             <span><strong class="command">query-source-v6</strong></span>
3087             options; it implicitly disables the use of randomized port numbers
3088             and leads to insecure operation.
3089             The <span><strong class="command">avoid-v4-udp-ports</strong></span>
3090             and <span><strong class="command">avoid-v6-udp-ports</strong></span> options can be used
3091             to prevent named
3092             from selecting certain ports. The defaults are:
3093           </p>
3094 <pre class="programlisting">query-source address * port *;
3095 query-source-v6 address * port *;
3096 </pre>
3097 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3098 <h3 class="title">Note</h3>
3099 <p>
3100               The address specified in the <span><strong class="command">query-source</strong></span> option
3101               is used for both UDP and TCP queries, but the port applies only
3102               to
3103               UDP queries.  TCP queries always use a random
3104               unprivileged port.
3105             </p>
3106 </div>
3107 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3108 <h3 class="title">Note</h3>
3109 <p>
3110               Solaris 2.5.1 and earlier does not support setting the source
3111               address for TCP sockets.
3112             </p>
3113 </div>
3114 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3115 <h3 class="title">Note</h3>
3116 <p>
3117               See also <span><strong class="command">transfer-source</strong></span> and
3118               <span><strong class="command">notify-source</strong></span>.
3119             </p>
3120 </div>
3121 </div>
3122 <div class="sect3" lang="en">
3123 <div class="titlepage"><div><div><h4 class="title">
3124 <a name="zone_transfers"></a>Zone Transfers</h4></div></div></div>
3125 <p>
3126             <acronym class="acronym">BIND</acronym> has mechanisms in place to
3127             facilitate zone transfers
3128             and set limits on the amount of load that transfers place on the
3129             system. The following options apply to zone transfers.
3130           </p>
3131 <div class="variablelist"><dl>
3132 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
3133 <dd><p>
3134                   Defines a global list of IP addresses of name servers
3135                   that are also sent NOTIFY messages whenever a fresh copy of
3136                   the
3137                   zone is loaded, in addition to the servers listed in the
3138                   zone's NS records.
3139                   This helps to ensure that copies of the zones will
3140                   quickly converge on stealth servers. If an <span><strong class="command">also-notify</strong></span> list
3141                   is given in a <span><strong class="command">zone</strong></span> statement,
3142                   it will override
3143                   the <span><strong class="command">options also-notify</strong></span>
3144                   statement. When a <span><strong class="command">zone notify</strong></span>
3145                   statement
3146                   is set to <span><strong class="command">no</strong></span>, the IP
3147                   addresses in the global <span><strong class="command">also-notify</strong></span> list will
3148                   not be sent NOTIFY messages for that zone. The default is
3149                   the empty
3150                   list (no global notification list).
3151                 </p></dd>
3152 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
3153 <dd><p>
3154                   Inbound zone transfers running longer than
3155                   this many minutes will be terminated. The default is 120
3156                   minutes
3157                   (2 hours).  The maximum value is 28 days (40320 minutes).
3158                 </p></dd>
3159 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
3160 <dd><p>
3161                   Inbound zone transfers making no progress
3162                   in this many minutes will be terminated. The default is 60
3163                   minutes
3164                   (1 hour).  The maximum value is 28 days (40320 minutes).
3165                 </p></dd>
3166 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
3167 <dd><p>
3168                   Outbound zone transfers running longer than
3169                   this many minutes will be terminated. The default is 120
3170                   minutes
3171                   (2 hours).  The maximum value is 28 days (40320 minutes).
3172                 </p></dd>
3173 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
3174 <dd><p>
3175                   Outbound zone transfers making no progress
3176                   in this many minutes will be terminated.  The default is 60
3177                   minutes (1
3178                   hour).  The maximum value is 28 days (40320 minutes).
3179                 </p></dd>
3180 <dt><span class="term"><span><strong class="command">serial-query-rate</strong></span></span></dt>
3181 <dd><p>
3182                   Slave servers will periodically query master servers
3183                   to find out if zone serial numbers have changed. Each such
3184                   query uses
3185                   a minute amount of the slave server's network bandwidth.  To
3186                   limit the
3187                   amount of bandwidth used, BIND 9 limits the rate at which
3188                   queries are
3189                   sent.  The value of the <span><strong class="command">serial-query-rate</strong></span> option,
3190                   an integer, is the maximum number of queries sent per
3191                   second.
3192                   The default is 20.
3193                 </p></dd>
3194 <dt><span class="term"><span><strong class="command">serial-queries</strong></span></span></dt>
3195 <dd><p>
3196                   In BIND 8, the <span><strong class="command">serial-queries</strong></span>
3197                   option
3198                   set the maximum number of concurrent serial number queries
3199                   allowed to be outstanding at any given time.
3200                   BIND 9 does not limit the number of outstanding
3201                   serial queries and ignores the <span><strong class="command">serial-queries</strong></span> option.
3202                   Instead, it limits the rate at which the queries are sent
3203                   as defined using the <span><strong class="command">serial-query-rate</strong></span> option.
3204                 </p></dd>
3205 <dt><span class="term"><span><strong class="command">transfer-format</strong></span></span></dt>
3206 <dd><p>
3207                   Zone transfers can be sent using two different formats,
3208                   <span><strong class="command">one-answer</strong></span> and
3209                   <span><strong class="command">many-answers</strong></span>.
3210                   The <span><strong class="command">transfer-format</strong></span> option is used
3211                   on the master server to determine which format it sends.
3212                   <span><strong class="command">one-answer</strong></span> uses one DNS message per
3213                   resource record transferred.
3214                   <span><strong class="command">many-answers</strong></span> packs as many resource
3215                   records as possible into a message.
3216                   <span><strong class="command">many-answers</strong></span> is more efficient, but is
3217                   only supported by relatively new slave servers,
3218                   such as <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
3219                   8.x and <acronym class="acronym">BIND</acronym> 4.9.5 onwards.
3220                   The <span><strong class="command">many-answers</strong></span> format is also supported by
3221                   recent Microsoft Windows nameservers.
3222                   The default is <span><strong class="command">many-answers</strong></span>.
3223                   <span><strong class="command">transfer-format</strong></span> may be overridden on a
3224                   per-server basis by using the <span><strong class="command">server</strong></span>
3225                   statement.
3226                 </p></dd>
3227 <dt><span class="term"><span><strong class="command">transfers-in</strong></span></span></dt>
3228 <dd><p>
3229                   The maximum number of inbound zone transfers
3230                   that can be running concurrently. The default value is <code class="literal">10</code>.
3231                   Increasing <span><strong class="command">transfers-in</strong></span> may
3232                   speed up the convergence
3233                   of slave zones, but it also may increase the load on the
3234                   local system.
3235                 </p></dd>
3236 <dt><span class="term"><span><strong class="command">transfers-out</strong></span></span></dt>
3237 <dd><p>
3238                   The maximum number of outbound zone transfers
3239                   that can be running concurrently. Zone transfer requests in
3240                   excess
3241                   of the limit will be refused. The default value is <code class="literal">10</code>.
3242                 </p></dd>
3243 <dt><span class="term"><span><strong class="command">transfers-per-ns</strong></span></span></dt>
3244 <dd><p>
3245                   The maximum number of inbound zone transfers
3246                   that can be concurrently transferring from a given remote
3247                   name server.
3248                   The default value is <code class="literal">2</code>.
3249                   Increasing <span><strong class="command">transfers-per-ns</strong></span>
3250                   may
3251                   speed up the convergence of slave zones, but it also may
3252                   increase
3253                   the load on the remote name server. <span><strong class="command">transfers-per-ns</strong></span> may
3254                   be overridden on a per-server basis by using the <span><strong class="command">transfers</strong></span> phrase
3255                   of the <span><strong class="command">server</strong></span> statement.
3256                 </p></dd>
3257 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
3258 <dd>
3259 <p><span><strong class="command">transfer-source</strong></span>
3260                   determines which local address will be bound to IPv4
3261                   TCP connections used to fetch zones transferred
3262                   inbound by the server.  It also determines the
3263                   source IPv4 address, and optionally the UDP port,
3264                   used for the refresh queries and forwarded dynamic
3265                   updates.  If not set, it defaults to a system
3266                   controlled value which will usually be the address
3267                   of the interface "closest to" the remote end. This
3268                   address must appear in the remote end's
3269                   <span><strong class="command">allow-transfer</strong></span> option for the
3270                   zone being transferred, if one is specified. This
3271                   statement sets the
3272                   <span><strong class="command">transfer-source</strong></span> for all zones,
3273                   but can be overridden on a per-view or per-zone
3274                   basis by including a
3275                   <span><strong class="command">transfer-source</strong></span> statement within
3276                   the <span><strong class="command">view</strong></span> or
3277                   <span><strong class="command">zone</strong></span> block in the configuration
3278                   file.
3279                 </p>
3280 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3281 <h3 class="title">Note</h3>
3282 <p>
3283                     Solaris 2.5.1 and earlier does not support setting the
3284                     source address for TCP sockets.
3285                   </p>
3286 </div>
3287 </dd>
3288 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
3289 <dd><p>
3290                   The same as <span><strong class="command">transfer-source</strong></span>,
3291                   except zone transfers are performed using IPv6.
3292                 </p></dd>
3293 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
3294 <dd>
3295 <p>
3296                   An alternate transfer source if the one listed in
3297                   <span><strong class="command">transfer-source</strong></span> fails and
3298                   <span><strong class="command">use-alt-transfer-source</strong></span> is
3299                   set.
3300                 </p>
3301 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3302 <h3 class="title">Note</h3>
3303                   If you do not wish the alternate transfer source
3304                   to be used, you should set
3305                   <span><strong class="command">use-alt-transfer-source</strong></span>
3306                   appropriately and you should not depend upon
3307                   getting a answer back to the first refresh
3308                   query.
3309                 </div>
3310 </dd>
3311 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
3312 <dd><p>
3313                   An alternate transfer source if the one listed in
3314                   <span><strong class="command">transfer-source-v6</strong></span> fails and
3315                   <span><strong class="command">use-alt-transfer-source</strong></span> is
3316                   set.
3317                 </p></dd>
3318 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
3319 <dd><p>
3320                   Use the alternate transfer sources or not.  If views are
3321                   specified this defaults to <span><strong class="command">no</strong></span>
3322                   otherwise it defaults to
3323                   <span><strong class="command">yes</strong></span> (for BIND 8
3324                   compatibility).
3325                 </p></dd>
3326 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
3327 <dd>
3328 <p><span><strong class="command">notify-source</strong></span>
3329                   determines which local source address, and
3330                   optionally UDP port, will be used to send NOTIFY
3331                   messages.  This address must appear in the slave
3332                   server's <span><strong class="command">masters</strong></span> zone clause or
3333                   in an <span><strong class="command">allow-notify</strong></span> clause.  This
3334                   statement sets the <span><strong class="command">notify-source</strong></span>
3335                   for all zones, but can be overridden on a per-zone or
3336                   per-view basis by including a
3337                   <span><strong class="command">notify-source</strong></span> statement within
3338                   the <span><strong class="command">zone</strong></span> or
3339                   <span><strong class="command">view</strong></span> block in the configuration
3340                   file.
3341                 </p>
3342 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3343 <h3 class="title">Note</h3>
3344 <p>
3345                     Solaris 2.5.1 and earlier does not support setting the
3346                     source address for TCP sockets.
3347                   </p>
3348 </div>
3349 </dd>
3350 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
3351 <dd><p>
3352                   Like <span><strong class="command">notify-source</strong></span>,
3353                   but applies to notify messages sent to IPv6 addresses.
3354                 </p></dd>
3355 </dl></div>
3356 </div>
3357 <div class="sect3" lang="en">
3358 <div class="titlepage"><div><div><h4 class="title">
3359 <a name="id2581988"></a>Bad UDP Port Lists</h4></div></div></div>
3360 <p><span><strong class="command">avoid-v4-udp-ports</strong></span>
3361             and <span><strong class="command">avoid-v6-udp-ports</strong></span> specify a list
3362             of IPv4 and IPv6 UDP ports that will not be used as system
3363             assigned source ports for UDP sockets.  These lists
3364             prevent named from choosing as its random source port a
3365             port that is blocked by your firewall.  If a query went
3366             out with such a source port, the answer would not get by
3367             the firewall and the name server would have to query
3368             again.
3369           </p>
3370 </div>
3371 <div class="sect3" lang="en">
3372 <div class="titlepage"><div><div><h4 class="title">
3373 <a name="id2582003"></a>Operating System Resource Limits</h4></div></div></div>
3374 <p>
3375             The server's usage of many system resources can be limited.
3376             Scaled values are allowed when specifying resource limits.  For
3377             example, <span><strong class="command">1G</strong></span> can be used instead of
3378             <span><strong class="command">1073741824</strong></span> to specify a limit of
3379             one
3380             gigabyte. <span><strong class="command">unlimited</strong></span> requests
3381             unlimited use, or the
3382             maximum available amount. <span><strong class="command">default</strong></span>
3383             uses the limit
3384             that was in force when the server was started. See the description
3385             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>.
3386           </p>
3387 <p>
3388             The following options set operating system resource limits for
3389             the name server process.  Some operating systems don't support
3390             some or
3391             any of the limits. On such systems, a warning will be issued if
3392             the
3393             unsupported limit is used.
3394           </p>
3395 <div class="variablelist"><dl>
3396 <dt><span class="term"><span><strong class="command">coresize</strong></span></span></dt>
3397 <dd><p>
3398                   The maximum size of a core dump. The default
3399                   is <code class="literal">default</code>.
3400                 </p></dd>
3401 <dt><span class="term"><span><strong class="command">datasize</strong></span></span></dt>
3402 <dd><p>
3403                   The maximum amount of data memory the server
3404                   may use. The default is <code class="literal">default</code>.
3405                   This is a hard limit on server memory usage.
3406                   If the server attempts to allocate memory in excess of this
3407                   limit, the allocation will fail, which may in turn leave
3408                   the server unable to perform DNS service.  Therefore,
3409                   this option is rarely useful as a way of limiting the
3410                   amount of memory used by the server, but it can be used
3411                   to raise an operating system data size limit that is
3412                   too small by default.  If you wish to limit the amount
3413                   of memory used by the server, use the
3414                   <span><strong class="command">max-cache-size</strong></span> and
3415                   <span><strong class="command">recursive-clients</strong></span>
3416                   options instead.
3417                 </p></dd>
3418 <dt><span class="term"><span><strong class="command">files</strong></span></span></dt>
3419 <dd><p>
3420                   The maximum number of files the server
3421                   may have open concurrently. The default is <code class="literal">unlimited</code>.
3422                 </p></dd>
3423 <dt><span class="term"><span><strong class="command">stacksize</strong></span></span></dt>
3424 <dd><p>
3425                   The maximum amount of stack memory the server
3426                   may use. The default is <code class="literal">default</code>.
3427                 </p></dd>
3428 </dl></div>
3429 </div>
3430 <div class="sect3" lang="en">
3431 <div class="titlepage"><div><div><h4 class="title">
3432 <a name="id2582186"></a>Server  Resource Limits</h4></div></div></div>
3433 <p>
3434             The following options set limits on the server's
3435             resource consumption that are enforced internally by the
3436             server rather than the operating system.
3437           </p>
3438 <div class="variablelist"><dl>
3439 <dt><span class="term"><span><strong class="command">max-ixfr-log-size</strong></span></span></dt>
3440 <dd><p>
3441                   This option is obsolete; it is accepted
3442                   and ignored for BIND 8 compatibility.  The option
3443                   <span><strong class="command">max-journal-size</strong></span> performs a
3444                   similar function in BIND 9.
3445                 </p></dd>
3446 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
3447 <dd><p>
3448                   Sets a maximum size for each journal file
3449                   (see <a href="Bv9ARM.ch04.html#journal" title="The journal file">the section called &#8220;The journal file&#8221;</a>).  When the journal file
3450                   approaches
3451                   the specified size, some of the oldest transactions in the
3452                   journal
3453                   will be automatically removed.  The default is
3454                   <code class="literal">unlimited</code>.
3455                 </p></dd>
3456 <dt><span class="term"><span><strong class="command">host-statistics-max</strong></span></span></dt>
3457 <dd><p>
3458                   In BIND 8, specifies the maximum number of host statistics
3459                   entries to be kept.
3460                   Not implemented in BIND 9.
3461                 </p></dd>
3462 <dt><span class="term"><span><strong class="command">recursive-clients</strong></span></span></dt>
3463 <dd><p>
3464                   The maximum number of simultaneous recursive lookups
3465                   the server will perform on behalf of clients.  The default
3466                   is
3467                   <code class="literal">1000</code>.  Because each recursing
3468                   client uses a fair
3469                   bit of memory, on the order of 20 kilobytes, the value of
3470                   the
3471                   <span><strong class="command">recursive-clients</strong></span> option may
3472                   have to be decreased
3473                   on hosts with limited memory.
3474                 </p></dd>
3475 <dt><span class="term"><span><strong class="command">tcp-clients</strong></span></span></dt>
3476 <dd><p>
3477                   The maximum number of simultaneous client TCP
3478                   connections that the server will accept.
3479                   The default is <code class="literal">100</code>.
3480                 </p></dd>
3481 <dt><span class="term"><span><strong class="command">max-cache-size</strong></span></span></dt>
3482 <dd><p>
3483                   The maximum amount of memory to use for the
3484                   server's cache, in bytes.  When the amount of data in the
3485                   cache
3486                   reaches this limit, the server will cause records to expire
3487                   prematurely so that the limit is not exceeded.  In a server
3488                   with
3489                   multiple views, the limit applies separately to the cache of
3490                   each
3491                   view.  The default is <code class="literal">unlimited</code>, meaning that
3492                   records are purged from the cache only when their TTLs
3493                   expire.
3494                 </p></dd>
3495 <dt><span class="term"><span><strong class="command">tcp-listen-queue</strong></span></span></dt>
3496 <dd><p>
3497                   The listen queue depth.  The default and minimum is 3.
3498                   If the kernel supports the accept filter "dataready" this
3499                   also controls how
3500                   many TCP connections that will be queued in kernel space
3501                   waiting for
3502                   some data before being passed to accept.  Values less than 3
3503                   will be
3504                   silently raised.
3505                 </p></dd>
3506 </dl></div>
3507 </div>
3508 <div class="sect3" lang="en">
3509 <div class="titlepage"><div><div><h4 class="title">
3510 <a name="id2582320"></a>Periodic Task Intervals</h4></div></div></div>
3511 <div class="variablelist"><dl>
3512 <dt><span class="term"><span><strong class="command">cleaning-interval</strong></span></span></dt>
3513 <dd><p>
3514                   The server will remove expired resource records
3515                   from the cache every <span><strong class="command">cleaning-interval</strong></span> minutes.
3516                   The default is 60 minutes.  The maximum value is 28 days
3517                   (40320 minutes).
3518                   If set to 0, no periodic cleaning will occur.
3519                 </p></dd>
3520 <dt><span class="term"><span><strong class="command">heartbeat-interval</strong></span></span></dt>
3521 <dd><p>
3522                   The server will perform zone maintenance tasks
3523                   for all zones marked as <span><strong class="command">dialup</strong></span> whenever this
3524                   interval expires. The default is 60 minutes. Reasonable
3525                   values are up
3526                   to 1 day (1440 minutes).  The maximum value is 28 days
3527                   (40320 minutes).
3528                   If set to 0, no zone maintenance for these zones will occur.
3529                 </p></dd>
3530 <dt><span class="term"><span><strong class="command">interface-interval</strong></span></span></dt>
3531 <dd><p>
3532                   The server will scan the network interface list
3533                   every <span><strong class="command">interface-interval</strong></span>
3534                   minutes. The default
3535                   is 60 minutes. The maximum value is 28 days (40320 minutes).
3536                   If set to 0, interface scanning will only occur when
3537                   the configuration file is  loaded. After the scan, the
3538                   server will
3539                   begin listening for queries on any newly discovered
3540                   interfaces (provided they are allowed by the
3541                   <span><strong class="command">listen-on</strong></span> configuration), and
3542                   will
3543                   stop listening on interfaces that have gone away.
3544                 </p></dd>
3545 <dt><span class="term"><span><strong class="command">statistics-interval</strong></span></span></dt>
3546 <dd>
3547 <p>
3548                   Name server statistics will be logged
3549                   every <span><strong class="command">statistics-interval</strong></span>
3550                   minutes. The default is
3551                   60. The maximum value is 28 days (40320 minutes).
3552                   If set to 0, no statistics will be logged.
3553                   </p>
3554 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3555 <h3 class="title">Note</h3>
3556 <p>
3557                     Not yet implemented in
3558                     <acronym class="acronym">BIND</acronym> 9.
3559                   </p>
3560 </div>
3561 </dd>
3562 </dl></div>
3563 </div>
3564 <div class="sect3" lang="en">
3565 <div class="titlepage"><div><div><h4 class="title">
3566 <a name="topology"></a>Topology</h4></div></div></div>
3567 <p>
3568             All other things being equal, when the server chooses a name
3569             server
3570             to query from a list of name servers, it prefers the one that is
3571             topologically closest to itself. The <span><strong class="command">topology</strong></span> statement
3572             takes an <span><strong class="command">address_match_list</strong></span> and
3573             interprets it
3574             in a special way. Each top-level list element is assigned a
3575             distance.
3576             Non-negated elements get a distance based on their position in the
3577             list, where the closer the match is to the start of the list, the
3578             shorter the distance is between it and the server. A negated match
3579             will be assigned the maximum distance from the server. If there
3580             is no match, the address will get a distance which is further than
3581             any non-negated list element, and closer than any negated element.
3582             For example,
3583           </p>
3584 <pre class="programlisting">topology {
3585     10/8;
3586     !1.2.3/24;
3587     { 1.2/16; 3/8; };
3588 };</pre>
3589 <p>
3590             will prefer servers on network 10 the most, followed by hosts
3591             on network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the
3592             exception of hosts on network 1.2.3 (netmask 255.255.255.0), which
3593             is preferred least of all.
3594           </p>
3595 <p>
3596             The default topology is
3597           </p>
3598 <pre class="programlisting">    topology { localhost; localnets; };
3599 </pre>
3600 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3601 <h3 class="title">Note</h3>
3602 <p>
3603               The <span><strong class="command">topology</strong></span> option
3604               is not implemented in <acronym class="acronym">BIND</acronym> 9.
3605             </p>
3606 </div>
3607 </div>
3608 <div class="sect3" lang="en">
3609 <div class="titlepage"><div><div><h4 class="title">
3610 <a name="the_sortlist_statement"></a>The <span><strong class="command">sortlist</strong></span> Statement</h4></div></div></div>
3611 <p>
3612             The response to a DNS query may consist of multiple resource
3613             records (RRs) forming a resource records set (RRset).
3614             The name server will normally return the
3615             RRs within the RRset in an indeterminate order
3616             (but see the <span><strong class="command">rrset-order</strong></span>
3617             statement in <a href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">the section called &#8220;RRset Ordering&#8221;</a>).
3618             The client resolver code should rearrange the RRs as appropriate,
3619             that is, using any addresses on the local net in preference to
3620             other addresses.
3621             However, not all resolvers can do this or are correctly
3622             configured.
3623             When a client is using a local server, the sorting can be performed
3624             in the server, based on the client's address. This only requires
3625             configuring the name servers, not all the clients.
3626           </p>
3627 <p>
3628             The <span><strong class="command">sortlist</strong></span> statement (see below)
3629             takes
3630             an <span><strong class="command">address_match_list</strong></span> and
3631             interprets it even
3632             more specifically than the <span><strong class="command">topology</strong></span>
3633             statement
3634             does (<a href="Bv9ARM.ch06.html#topology" title="Topology">the section called &#8220;Topology&#8221;</a>).
3635             Each top level statement in the <span><strong class="command">sortlist</strong></span> must
3636             itself be an explicit <span><strong class="command">address_match_list</strong></span> with
3637             one or two elements. The first element (which may be an IP
3638             address,
3639             an IP prefix, an ACL name or a nested <span><strong class="command">address_match_list</strong></span>)
3640             of each top level list is checked against the source address of
3641             the query until a match is found.
3642           </p>
3643 <p>
3644             Once the source address of the query has been matched, if
3645             the top level statement contains only one element, the actual
3646             primitive
3647             element that matched the source address is used to select the
3648             address
3649             in the response to move to the beginning of the response. If the
3650             statement is a list of two elements, then the second element is
3651             treated the same as the <span><strong class="command">address_match_list</strong></span> in
3652             a <span><strong class="command">topology</strong></span> statement. Each top
3653             level element
3654             is assigned a distance and the address in the response with the
3655             minimum
3656             distance is moved to the beginning of the response.
3657           </p>
3658 <p>
3659             In the following example, any queries received from any of
3660             the addresses of the host itself will get responses preferring
3661             addresses
3662             on any of the locally connected networks. Next most preferred are
3663             addresses
3664             on the 192.168.1/24 network, and after that either the
3665             192.168.2/24
3666             or
3667             192.168.3/24 network with no preference shown between these two
3668             networks. Queries received from a host on the 192.168.1/24 network
3669             will prefer other addresses on that network to the 192.168.2/24
3670             and
3671             192.168.3/24 networks. Queries received from a host on the
3672             192.168.4/24
3673             or the 192.168.5/24 network will only prefer other addresses on
3674             their directly connected networks.
3675           </p>
3676 <pre class="programlisting">sortlist {
3677     { localhost;                                   // IF   the local host
3678         { localnets;                               // THEN first fit on the
3679             192.168.1/24;                          //   following nets
3680             { 192.168.2/24; 192.168.3/24; }; }; };
3681     { 192.168.1/24;                                // IF   on class C 192.168.1
3682         { 192.168.1/24;                            // THEN use .1, or .2 or .3
3683             { 192.168.2/24; 192.168.3/24; }; }; };
3684     { 192.168.2/24;                                // IF   on class C 192.168.2
3685         { 192.168.2/24;                            // THEN use .2, or .1 or .3
3686             { 192.168.1/24; 192.168.3/24; }; }; };
3687     { 192.168.3/24;                                // IF   on class C 192.168.3
3688         { 192.168.3/24;                            // THEN use .3, or .1 or .2
3689             { 192.168.1/24; 192.168.2/24; }; }; };
3690     { { 192.168.4/24; 192.168.5/24; };             // if .4 or .5, prefer that net
3691     };
3692 };</pre>
3693 <p>
3694             The following example will give reasonable behavior for the
3695             local host and hosts on directly connected networks. It is similar
3696             to the behavior of the address sort in <acronym class="acronym">BIND</acronym> 4.9.x. Responses sent
3697             to queries from the local host will favor any of the directly
3698             connected
3699             networks. Responses sent to queries from any other hosts on a
3700             directly
3701             connected network will prefer addresses on that same network.
3702             Responses
3703             to other queries will not be sorted.
3704           </p>
3705 <pre class="programlisting">sortlist {
3706            { localhost; localnets; };
3707            { localnets; };
3708 };
3709 </pre>
3710 </div>
3711 <div class="sect3" lang="en">
3712 <div class="titlepage"><div><div><h4 class="title">
3713 <a name="rrset_ordering"></a>RRset Ordering</h4></div></div></div>
3714 <p>
3715             When multiple records are returned in an answer it may be
3716             useful to configure the order of the records placed into the
3717             response.
3718             The <span><strong class="command">rrset-order</strong></span> statement permits
3719             configuration
3720             of the ordering of the records in a multiple record response.
3721             See also the <span><strong class="command">sortlist</strong></span> statement,
3722             <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>.
3723           </p>
3724 <p>
3725             An <span><strong class="command">order_spec</strong></span> is defined as
3726             follows:
3727           </p>
3728 <p>
3729             [<span class="optional">class <em class="replaceable"><code>class_name</code></em></span>]
3730             [<span class="optional">type <em class="replaceable"><code>type_name</code></em></span>]
3731             [<span class="optional">name <em class="replaceable"><code>"domain_name"</code></em></span>]
3732             order <em class="replaceable"><code>ordering</code></em>
3733           </p>
3734 <p>
3735             If no class is specified, the default is <span><strong class="command">ANY</strong></span>.
3736             If no type is specified, the default is <span><strong class="command">ANY</strong></span>.
3737             If no name is specified, the default is "<span><strong class="command">*</strong></span>" (asterisk).
3738           </p>
3739 <p>
3740             The legal values for <span><strong class="command">ordering</strong></span> are:
3741           </p>
3742 <div class="informaltable"><table border="1">
3743 <colgroup>
3744 <col>
3745 <col>
3746 </colgroup>
3747 <tbody>
3748 <tr>
3749 <td>
3750                     <p><span><strong class="command">fixed</strong></span></p>
3751                   </td>
3752 <td>
3753                     <p>
3754                       Records are returned in the order they
3755                       are defined in the zone file.
3756                     </p>
3757                   </td>
3758 </tr>
3759 <tr>
3760 <td>
3761                     <p><span><strong class="command">random</strong></span></p>
3762                   </td>
3763 <td>
3764                     <p>
3765                       Records are returned in some random order.
3766                     </p>
3767                   </td>
3768 </tr>
3769 <tr>
3770 <td>
3771                     <p><span><strong class="command">cyclic</strong></span></p>
3772                   </td>
3773 <td>
3774                     <p>
3775                       Records are returned in a round-robin
3776                       order.
3777                     </p>
3778                   </td>
3779 </tr>
3780 </tbody>
3781 </table></div>
3782 <p>
3783             For example:
3784           </p>
3785 <pre class="programlisting">rrset-order {
3786    class IN type A name "host.example.com" order random;
3787    order cyclic;
3788 };
3789 </pre>
3790 <p>
3791             will cause any responses for type A records in class IN that
3792             have "<code class="literal">host.example.com</code>" as a
3793             suffix, to always be returned
3794             in random order. All other records are returned in cyclic order.
3795           </p>
3796 <p>
3797             If multiple <span><strong class="command">rrset-order</strong></span> statements
3798             appear,
3799             they are not combined &#8212; the last one applies.
3800           </p>
3801 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3802 <h3 class="title">Note</h3>
3803 <p>
3804               The <span><strong class="command">rrset-order</strong></span> statement
3805               is not yet fully implemented in <acronym class="acronym">BIND</acronym> 9.
3806               BIND 9 currently does not fully support "fixed" ordering.
3807             </p>
3808 </div>
3809 </div>
3810 <div class="sect3" lang="en">
3811 <div class="titlepage"><div><div><h4 class="title">
3812 <a name="tuning"></a>Tuning</h4></div></div></div>
3813 <div class="variablelist"><dl>
3814 <dt><span class="term"><span><strong class="command">lame-ttl</strong></span></span></dt>
3815 <dd><p>
3816                   Sets the number of seconds to cache a
3817                   lame server indication. 0 disables caching. (This is
3818                   <span class="bold"><strong>NOT</strong></span> recommended.)
3819                   The default is <code class="literal">600</code> (10 minutes) and the
3820                   maximum value is
3821                   <code class="literal">1800</code> (30 minutes).
3822                 </p></dd>
3823 <dt><span class="term"><span><strong class="command">max-ncache-ttl</strong></span></span></dt>
3824 <dd><p>
3825                   To reduce network traffic and increase performance,
3826                   the server stores negative answers. <span><strong class="command">max-ncache-ttl</strong></span> is
3827                   used to set a maximum retention time for these answers in
3828                   the server
3829                   in seconds. The default
3830                   <span><strong class="command">max-ncache-ttl</strong></span> is <code class="literal">10800</code> seconds (3 hours).
3831                   <span><strong class="command">max-ncache-ttl</strong></span> cannot exceed
3832                   7 days and will
3833                   be silently truncated to 7 days if set to a greater value.
3834                 </p></dd>
3835 <dt><span class="term"><span><strong class="command">max-cache-ttl</strong></span></span></dt>
3836 <dd><p>
3837                   Sets the maximum time for which the server will
3838                   cache ordinary (positive) answers. The default is
3839                   one week (7 days).
3840                 </p></dd>
3841 <dt><span class="term"><span><strong class="command">min-roots</strong></span></span></dt>
3842 <dd>
3843 <p>
3844                   The minimum number of root servers that
3845                   is required for a request for the root servers to be
3846                   accepted. The default
3847                   is <strong class="userinput"><code>2</code></strong>.
3848                 </p>
3849 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3850 <h3 class="title">Note</h3>
3851 <p>
3852                     Not implemented in <acronym class="acronym">BIND</acronym> 9.
3853                   </p>
3854 </div>
3855 </dd>
3856 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
3857 <dd><p>
3858                   Specifies the number of days into the
3859                   future when DNSSEC signatures automatically generated as a
3860                   result
3861                   of dynamic updates (<a href="Bv9ARM.ch04.html#dynamic_update" title="Dynamic Update">the section called &#8220;Dynamic Update&#8221;</a>)
3862                   will expire. The default is <code class="literal">30</code> days.
3863                   The maximum value is 10 years (3660 days). The signature
3864                   inception time is unconditionally set to one hour before the
3865                   current time
3866                   to allow for a limited amount of clock skew.
3867                 </p></dd>
3868 <dt>
3869 <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>
3870 </dt>
3871 <dd>
3872 <p>
3873                   These options control the server's behavior on refreshing a
3874                   zone
3875                   (querying for SOA changes) or retrying failed transfers.
3876                   Usually the SOA values for the zone are used, but these
3877                   values
3878                   are set by the master, giving slave server administrators
3879                   little
3880                   control over their contents.
3881                 </p>
3882 <p>
3883                   These options allow the administrator to set a minimum and
3884                   maximum
3885                   refresh and retry time either per-zone, per-view, or
3886                   globally.
3887                   These options are valid for slave and stub zones,
3888                   and clamp the SOA refresh and retry times to the specified
3889                   values.
3890                 </p>
3891 </dd>
3892 <dt><span class="term"><span><strong class="command">edns-udp-size</strong></span></span></dt>
3893 <dd><p>
3894                   Sets the advertised EDNS UDP buffer size in bytes.  Valid
3895                   values are 512 to 4096 (values outside this range
3896                   will be silently adjusted).  The default value is
3897                   4096.  The usual reason for setting edns-udp-size to
3898                   a non-default value is to get UDP answers to pass
3899                   through broken firewalls that block fragmented
3900                   packets and/or block UDP packets that are greater
3901                   than 512 bytes.
3902                 </p></dd>
3903 <dt><span class="term"><span><strong class="command">max-udp-size</strong></span></span></dt>
3904 <dd><p>
3905                   Sets the maximum EDNS UDP message size named will
3906                   send in bytes.  Valid values are 512 to 4096 (values outside
3907                   this range will be silently adjusted).  The default
3908                   value is 4096.  The usual reason for setting
3909                   max-udp-size to a non-default value is to get UDP
3910                   answers to pass through broken firewalls that
3911                   block fragmented packets and/or block UDP packets
3912                   that are greater than 512 bytes.
3913                   This is independent of the advertised receive
3914                   buffer (<span><strong class="command">edns-udp-size</strong></span>).
3915                 </p></dd>
3916 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
3917 <dd><p>Specifies
3918                   the file format of zone files (see
3919                   <a href="Bv9ARM.ch06.html#zonefile_format" title="Additional File Formats">the section called &#8220;Additional File Formats&#8221;</a>).
3920                   The default value is <code class="constant">text</code>, which is the
3921                   standard textual representation.  Files in other formats
3922                   than <code class="constant">text</code> are typically expected
3923                   to be generated by the <span><strong class="command">named-compilezone</strong></span> tool.
3924                   Note that when a zone file in a different format than
3925                   <code class="constant">text</code> is loaded, <span><strong class="command">named</strong></span>
3926                   may omit some of the checks which would be performed for a
3927                   file in the <code class="constant">text</code> format.  In particular,
3928                   <span><strong class="command">check-names</strong></span> checks do not apply
3929                   for the <code class="constant">raw</code> format.  This means
3930                   a zone file in the <code class="constant">raw</code> format
3931                   must be generated with the same check level as that
3932                   specified in the <span><strong class="command">named</strong></span> configuration
3933                   file.  This statement sets the
3934                   <span><strong class="command">masterfile-format</strong></span> for all zones,
3935                   but can be overridden on a per-zone or per-view basis
3936                   by including a <span><strong class="command">masterfile-format</strong></span>
3937                   statement within the <span><strong class="command">zone</strong></span> or
3938                   <span><strong class="command">view</strong></span> block in the configuration
3939                   file.
3940                 </p></dd>
3941 <dt>
3942 <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>
3943 </dt>
3944 <dd>
3945 <p>These set the
3946                   initial value (minimum) and maximum number of recursive
3947                   simultanious clients for any given query
3948                   (&lt;qname,qtype,qclass&gt;) that the server will accept
3949                   before dropping additional clients.  named will attempt to
3950                   self tune this value and changes will be logged.  The
3951                   default values are 10 and 100.
3952                 </p>
3953 <p>
3954                   This value should reflect how many queries come in for
3955                   a given name in the time it takes to resolve that name.
3956                   If the number of queries exceed this value, named will
3957                   assume that it is dealing with a non-responsive zone
3958                   and will drop additional queries.  If it gets a response
3959                   after dropping queries, it will raise the estimate.  The
3960                   estimate will then be lowered in 20 minutes if it has
3961                   remained unchanged.
3962                 </p>
3963 <p>
3964                   If <span><strong class="command">clients-per-query</strong></span> is set to zero,
3965                   then there is no limit on the number of clients per query
3966                   and no queries will be dropped.
3967                 </p>
3968 <p>
3969                   If <span><strong class="command">max-clients-per-query</strong></span> is set to zero,
3970                   then there is no upper bound other than imposed by
3971                   <span><strong class="command">recursive-clients</strong></span>.
3972                 </p>
3973 </dd>
3974 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
3975 <dd><p>
3976                   The delay, in seconds, between sending sets of notify
3977                   messages for a zone.  The default is zero.
3978                 </p></dd>
3979 </dl></div>
3980 </div>
3981 <div class="sect3" lang="en">
3982 <div class="titlepage"><div><div><h4 class="title">
3983 <a name="builtin"></a>Built-in server information zones</h4></div></div></div>
3984 <p>
3985             The server provides some helpful diagnostic information
3986             through a number of built-in zones under the
3987             pseudo-top-level-domain <code class="literal">bind</code> in the
3988             <span><strong class="command">CHAOS</strong></span> class.  These zones are part
3989             of a
3990             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
3991             class
3992             <span><strong class="command">CHAOS</strong></span> which is separate from the
3993             default view of
3994             class <span><strong class="command">IN</strong></span>; therefore, any global
3995             server options
3996             such as <span><strong class="command">allow-query</strong></span> do not apply
3997             the these zones.
3998             If you feel the need to disable these zones, use the options
3999             below, or hide the built-in <span><strong class="command">CHAOS</strong></span>
4000             view by
4001             defining an explicit view of class <span><strong class="command">CHAOS</strong></span>
4002             that matches all clients.
4003           </p>
4004 <div class="variablelist"><dl>
4005 <dt><span class="term"><span><strong class="command">version</strong></span></span></dt>
4006 <dd><p>
4007                   The version the server should report
4008                   via a query of the name <code class="literal">version.bind</code>
4009                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
4010                   The default is the real version number of this server.
4011                   Specifying <span><strong class="command">version none</strong></span>
4012                   disables processing of the queries.
4013                 </p></dd>
4014 <dt><span class="term"><span><strong class="command">hostname</strong></span></span></dt>
4015 <dd><p>
4016                   The hostname the server should report via a query of
4017                   the name <code class="filename">hostname.bind</code>
4018                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
4019                   This defaults to the hostname of the machine hosting the
4020                   name server as
4021                   found by the gethostname() function.  The primary purpose of such queries
4022                   is to
4023                   identify which of a group of anycast servers is actually
4024                   answering your queries.  Specifying <span><strong class="command">hostname none;</strong></span>
4025                   disables processing of the queries.
4026                 </p></dd>
4027 <dt><span class="term"><span><strong class="command">server-id</strong></span></span></dt>
4028 <dd><p>
4029                   The ID of the server should report via a query of
4030                   the name <code class="filename">ID.SERVER</code>
4031                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
4032                   The primary purpose of such queries is to
4033                   identify which of a group of anycast servers is actually
4034                   answering your queries.  Specifying <span><strong class="command">server-id none;</strong></span>
4035                   disables processing of the queries.
4036                   Specifying <span><strong class="command">server-id hostname;</strong></span> will cause named to
4037                   use the hostname as found by the gethostname() function.
4038                   The default <span><strong class="command">server-id</strong></span> is <span><strong class="command">none</strong></span>.
4039                 </p></dd>
4040 </dl></div>
4041 </div>
4042 <div class="sect3" lang="en">
4043 <div class="titlepage"><div><div><h4 class="title">
4044 <a name="empty"></a>Built-in Empty Zones</h4></div></div></div>
4045 <p>
4046             Named has some built-in empty zones (SOA and NS records only).
4047             These are for zones that should normally be answered locally
4048             and which queries should not be sent to the Internet's root
4049             servers.  The official servers which cover these namespaces
4050             return NXDOMAIN responses to these queries.  In particular,
4051             these cover the reverse namespace for addresses from RFC 1918 and
4052             RFC 3330.  They also include the reverse namespace for IPv6 local
4053             address (locally assigned), IPv6 link local addresses, the IPv6
4054             loopback address and the IPv6 unknown addresss.
4055           </p>
4056 <p>
4057             Named will attempt to determine if a built in zone already exists
4058             or is active (covered by a forward-only forwarding declaration)
4059             and will not not create a empty zone in that case.
4060           </p>
4061 <p>
4062             The current list of empty zones is:
4063             </p>
4064 <div class="itemizedlist"><ul type="disc">
4065 <li>10.IN-ADDR.ARPA</li>
4066 <li>127.IN-ADDR.ARPA</li>
4067 <li>254.169.IN-ADDR.ARPA</li>
4068 <li>16.172.IN-ADDR.ARPA</li>
4069 <li>17.172.IN-ADDR.ARPA</li>
4070 <li>18.172.IN-ADDR.ARPA</li>
4071 <li>19.172.IN-ADDR.ARPA</li>
4072 <li>20.172.IN-ADDR.ARPA</li>
4073 <li>21.172.IN-ADDR.ARPA</li>
4074 <li>22.172.IN-ADDR.ARPA</li>
4075 <li>23.172.IN-ADDR.ARPA</li>
4076 <li>24.172.IN-ADDR.ARPA</li>
4077 <li>25.172.IN-ADDR.ARPA</li>
4078 <li>26.172.IN-ADDR.ARPA</li>
4079 <li>27.172.IN-ADDR.ARPA</li>
4080 <li>28.172.IN-ADDR.ARPA</li>
4081 <li>29.172.IN-ADDR.ARPA</li>
4082 <li>30.172.IN-ADDR.ARPA</li>
4083 <li>31.172.IN-ADDR.ARPA</li>
4084 <li>168.192.IN-ADDR.ARPA</li>
4085 <li>2.0.192.IN-ADDR.ARPA</li>
4086 <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>
4087 <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>
4088 <li>D.F.IP6.ARPA</li>
4089 <li>8.E.F.IP6.ARPA</li>
4090 <li>9.E.F.IP6.ARPA</li>
4091 <li>A.E.F.IP6.ARPA</li>
4092 <li>B.E.F.IP6.ARPA</li>
4093 </ul></div>
4094 <p>
4095           </p>
4096 <p>
4097             Empty zones are settable at the view level and only apply to
4098             views of class IN.  Disabled empty zones are only inherited
4099             from options if there are no disabled empty zones specified
4100             at the view level.  To override the options list of disabled
4101             zones, you can disable the root zone at the view level, for example:
4102 </p>
4103 <pre class="programlisting">
4104             disable-empty-zone ".";
4105 </pre>
4106 <p>
4107           </p>
4108 <p>
4109             If you are using the address ranges covered here, you should
4110             already have reverse zones covering the addresses you use.
4111             In practice this appears to not be the case with many queries
4112             being made to the infrastructure servers for names in these
4113             spaces.  So many in fact that sacrificial servers were needed
4114             to be deployed to channel the query load away from the
4115             infrastructure servers.
4116           </p>
4117 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4118 <h3 class="title">Note</h3>
4119             The real parent servers for these zones should disable all
4120             empty zone under the parent zone they serve.  For the real
4121             root servers, this is all built in empty zones.  This will
4122             enable them to return referrals to deeper in the tree.
4123           </div>
4124 <div class="variablelist"><dl>
4125 <dt><span class="term"><span><strong class="command">empty-server</strong></span></span></dt>
4126 <dd><p>
4127                   Specify what server name will appear in the returned
4128                   SOA record for empty zones.  If none is specified, then
4129                   the zone's name will be used.
4130                 </p></dd>
4131 <dt><span class="term"><span><strong class="command">empty-contact</strong></span></span></dt>
4132 <dd><p>
4133                   Specify what contact name will appear in the returned
4134                   SOA record for empty zones.  If none is specified, then
4135                   "." will be used.
4136                 </p></dd>
4137 <dt><span class="term"><span><strong class="command">empty-zones-enable</strong></span></span></dt>
4138 <dd><p>
4139                   Enable or disable all empty zones.  By default they
4140                   are enabled.
4141                 </p></dd>
4142 <dt><span class="term"><span><strong class="command">disable-empty-zone</strong></span></span></dt>
4143 <dd><p>
4144                   Disable individual empty zones.  By default none are
4145                   disabled.  This option can be specified multiple times.
4146                 </p></dd>
4147 </dl></div>
4148 </div>
4149 <div class="sect3" lang="en">
4150 <div class="titlepage"><div><div><h4 class="title">
4151 <a name="statsfile"></a>The Statistics File</h4></div></div></div>
4152 <p>
4153             The statistics file generated by <acronym class="acronym">BIND</acronym> 9
4154             is similar, but not identical, to that
4155             generated by <acronym class="acronym">BIND</acronym> 8.
4156           </p>
4157 <p>
4158             The statistics dump begins with a line, like:
4159           </p>
4160 <p>
4161             <span><strong class="command">+++ Statistics Dump +++ (973798949)</strong></span>
4162           </p>
4163 <p>
4164             The number in parentheses is a standard
4165             Unix-style timestamp, measured as seconds since January 1, 1970.
4166             Following
4167             that line are a series of lines containing a counter type, the
4168             value of the
4169             counter, optionally a zone name, and optionally a view name.
4170             The lines without view and zone listed are global statistics for
4171             the entire server.
4172             Lines with a zone and view name for the given view and zone (the
4173             view name is
4174             omitted for the default view).
4175           </p>
4176 <p>
4177             The statistics dump ends with the line where the
4178             number is identical to the number in the beginning line; for example:
4179           </p>
4180 <p>
4181             <span><strong class="command">--- Statistics Dump --- (973798949)</strong></span>
4182           </p>
4183 <p>
4184             The following statistics counters are maintained:
4185           </p>
4186 <div class="informaltable"><table border="1">
4187 <colgroup>
4188 <col>
4189 <col>
4190 </colgroup>
4191 <tbody>
4192 <tr>
4193 <td>
4194                     <p><span><strong class="command">success</strong></span></p>
4195                   </td>
4196 <td>
4197                     <p>
4198                       The number of
4199                       successful queries made to the server or zone.  A
4200                       successful query
4201                       is defined as query which returns a NOERROR response
4202                       with at least
4203                       one answer RR.
4204                     </p>
4205                   </td>
4206 </tr>
4207 <tr>
4208 <td>
4209                     <p><span><strong class="command">referral</strong></span></p>
4210                   </td>
4211 <td>
4212                     <p>
4213                       The number of queries which resulted
4214                       in referral responses.
4215                     </p>
4216                   </td>
4217 </tr>
4218 <tr>
4219 <td>
4220                     <p><span><strong class="command">nxrrset</strong></span></p>
4221                   </td>
4222 <td>
4223                     <p>
4224                       The number of queries which resulted in
4225                       NOERROR responses with no data.
4226                     </p>
4227                   </td>
4228 </tr>
4229 <tr>
4230 <td>
4231                     <p><span><strong class="command">nxdomain</strong></span></p>
4232                   </td>
4233 <td>
4234                     <p>
4235                       The number
4236                       of queries which resulted in NXDOMAIN responses.
4237                     </p>
4238                   </td>
4239 </tr>
4240 <tr>
4241 <td>
4242                     <p><span><strong class="command">failure</strong></span></p>
4243                   </td>
4244 <td>
4245                     <p>
4246                       The number of queries which resulted in a
4247                       failure response other than those above.
4248                     </p>
4249                   </td>
4250 </tr>
4251 <tr>
4252 <td>
4253                     <p><span><strong class="command">recursion</strong></span></p>
4254                   </td>
4255 <td>
4256                     <p>
4257                       The number of queries which caused the server
4258                       to perform recursion in order to find the final answer.
4259                     </p>
4260                   </td>
4261 </tr>
4262 <tr>
4263 <td>
4264                     <p><span><strong class="command">duplicate</strong></span></p>
4265                   </td>
4266 <td>
4267                     <p>
4268                       The number of queries which the server attempted to
4269                       recurse but discover a existing query with the same
4270                       IP address, port, query id, name, type and class
4271                       already being processed.
4272                     </p>
4273                   </td>
4274 </tr>
4275 <tr>
4276 <td>
4277                     <p><span><strong class="command">dropped</strong></span></p>
4278                   </td>
4279 <td>
4280                     <p>
4281                       The number of queries for which the server
4282                       discovered a excessive number of existing
4283                       recursive queries for the same name, type and
4284                       class and were subsequently dropped.
4285                     </p>
4286                   </td>
4287 </tr>
4288 </tbody>
4289 </table></div>
4290 <p>
4291             Each query received by the server will cause exactly one of
4292             <span><strong class="command">success</strong></span>,
4293             <span><strong class="command">referral</strong></span>,
4294             <span><strong class="command">nxrrset</strong></span>,
4295             <span><strong class="command">nxdomain</strong></span>, or
4296             <span><strong class="command">failure</strong></span>
4297             to be incremented, and may additionally cause the
4298             <span><strong class="command">recursion</strong></span> counter to be
4299             incremented.
4300           </p>
4301 </div>
4302 <div class="sect3" lang="en">
4303 <div class="titlepage"><div><div><h4 class="title">
4304 <a name="acache"></a>Additional Section Caching</h4></div></div></div>
4305 <p>
4306             The additional section cache, also called <span><strong class="command">acache</strong></span>,
4307             is an internal cache to improve the response performance of BIND 9.
4308             When additional section caching is enabled, BIND 9 will
4309             cache an internal short-cut to the additional section content for
4310             each answer RR.
4311             Note that <span><strong class="command">acache</strong></span> is an internal caching
4312             mechanism of BIND 9, and is not related to the DNS caching
4313             server function.
4314           </p>
4315 <p>
4316             Additional section caching does not change the
4317             response content (except the RRsets ordering of the additional
4318             section, see below), but can improve the response performance
4319             significantly.
4320             It is particularly effective when BIND 9 acts as an authoritative
4321             server for a zone that has many delegations with many glue RRs.
4322           </p>
4323 <p>
4324             In order to obtain the maximum performance improvement
4325             from additional section caching, setting
4326             <span><strong class="command">additional-from-cache</strong></span>
4327             to <span><strong class="command">no</strong></span> is recommended, since the current
4328             implementation of <span><strong class="command">acache</strong></span>
4329             does not short-cut of additional section information from the
4330             DNS cache data.
4331           </p>
4332 <p>
4333             One obvious disadvantage of <span><strong class="command">acache</strong></span> is
4334             that it requires much more
4335             memory for the internal cached data.
4336             Thus, if the response performance does not matter and memory
4337             consumption is much more critical, the
4338             <span><strong class="command">acache</strong></span> mechanism can be
4339             disabled by setting <span><strong class="command">acache-enable</strong></span> to
4340             <span><strong class="command">no</strong></span>.
4341             It is also possible to specify the upper limit of memory
4342             consumption
4343             for acache by using <span><strong class="command">max-acache-size</strong></span>.
4344           </p>
4345 <p>
4346             Additional section caching also has a minor effect on the
4347             RRset ordering in the additional section.
4348             Without <span><strong class="command">acache</strong></span>,
4349             <span><strong class="command">cyclic</strong></span> order is effective for the additional
4350             section as well as the answer and authority sections.
4351             However, additional section caching fixes the ordering when it
4352             first caches an RRset for the additional section, and the same
4353             ordering will be kept in succeeding responses, regardless of the
4354             setting of <span><strong class="command">rrset-order</strong></span>.
4355             The effect of this should be minor, however, since an
4356             RRset in the additional section
4357             typically only contains a small number of RRs (and in many cases
4358             it only contains a single RR), in which case the
4359             ordering does not matter much.
4360           </p>
4361 <p>
4362             The following is a summary of options related to
4363             <span><strong class="command">acache</strong></span>.
4364           </p>
4365 <div class="variablelist"><dl>
4366 <dt><span class="term"><span><strong class="command">acache-enable</strong></span></span></dt>
4367 <dd><p>
4368                   If <span><strong class="command">yes</strong></span>, additional section caching is
4369                   enabled.  The default value is <span><strong class="command">no</strong></span>.
4370                 </p></dd>
4371 <dt><span class="term"><span><strong class="command">acache-cleaning-interval</strong></span></span></dt>
4372 <dd><p>
4373                   The server will remove stale cache entries, based on an LRU
4374                   based
4375                   algorithm, every <span><strong class="command">acache-cleaning-interval</strong></span> minutes.
4376                   The default is 60 minutes.
4377                   If set to 0, no periodic cleaning will occur.
4378                 </p></dd>
4379 <dt><span class="term"><span><strong class="command">max-acache-size</strong></span></span></dt>
4380 <dd><p>
4381                   The maximum amount of memory in bytes to use for the server's acache.
4382                   When the amount of data in the acache reaches this limit,
4383                   the server
4384                   will clean more aggressively so that the limit is not
4385                   exceeded.
4386                   In a server with multiple views, the limit applies
4387                   separately to the
4388                   acache of each view.
4389                   The default is <code class="literal">unlimited</code>,
4390                   meaning that
4391                   entries are purged from the acache only at the
4392                   periodic cleaning time.
4393                 </p></dd>
4394 </dl></div>
4395 </div>
4396 </div>
4397 <div class="sect2" lang="en">
4398 <div class="titlepage"><div><div><h3 class="title">
4399 <a name="server_statement_grammar"></a><span><strong class="command">server</strong></span> Statement Grammar</h3></div></div></div>
4400 <pre class="programlisting">server <em class="replaceable"><code>ip_addr[/prefixlen]</code></em> {
4401     [<span class="optional"> bogus <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4402     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4403     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4404     [<span class="optional"> edns <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4405     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
4406     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
4407     [<span class="optional"> transfers <em class="replaceable"><code>number</code></em> ; </span>]
4408     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em> ; ]</span>]
4409     [<span class="optional"> keys <em class="replaceable"><code>{ string ; [<span class="optional"> string ; [<span class="optional">...</span>]</span>] }</code></em> ; </span>]
4410     [<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>]
4411     [<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>]
4412     [<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>]
4413     [<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>]
4414     [<span class="optional"> query-source [<span class="optional"> address ( <em class="replaceable"><code>ip_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]; </span>]
4415     [<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>] [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]; </span>]
4416 };
4417 </pre>
4418 </div>
4419 <div class="sect2" lang="en">
4420 <div class="titlepage"><div><div><h3 class="title">
4421 <a name="server_statement_definition_and_usage"></a><span><strong class="command">server</strong></span> Statement Definition and
4422             Usage</h3></div></div></div>
4423 <p>
4424             The <span><strong class="command">server</strong></span> statement defines
4425             characteristics
4426             to be associated with a remote name server.  If a prefix length is
4427             specified, then a range of servers is covered.  Only the most
4428             specific
4429             server clause applies regardless of the order in
4430             <code class="filename">named.conf</code>.
4431           </p>
4432 <p>
4433             The <span><strong class="command">server</strong></span> statement can occur at
4434             the top level of the
4435             configuration file or inside a <span><strong class="command">view</strong></span>
4436             statement.
4437             If a <span><strong class="command">view</strong></span> statement contains
4438             one or more <span><strong class="command">server</strong></span> statements, only
4439             those
4440             apply to the view and any top-level ones are ignored.
4441             If a view contains no <span><strong class="command">server</strong></span>
4442             statements,
4443             any top-level <span><strong class="command">server</strong></span> statements are
4444             used as
4445             defaults.
4446           </p>
4447 <p>
4448             If you discover that a remote server is giving out bad data,
4449             marking it as bogus will prevent further queries to it. The
4450             default
4451             value of <span><strong class="command">bogus</strong></span> is <span><strong class="command">no</strong></span>.
4452           </p>
4453 <p>
4454             The <span><strong class="command">provide-ixfr</strong></span> clause determines
4455             whether
4456             the local server, acting as master, will respond with an
4457             incremental
4458             zone transfer when the given remote server, a slave, requests it.
4459             If set to <span><strong class="command">yes</strong></span>, incremental transfer
4460             will be provided
4461             whenever possible. If set to <span><strong class="command">no</strong></span>,
4462             all transfers
4463             to the remote server will be non-incremental. If not set, the
4464             value
4465             of the <span><strong class="command">provide-ixfr</strong></span> option in the
4466             view or
4467             global options block is used as a default.
4468           </p>
4469 <p>
4470             The <span><strong class="command">request-ixfr</strong></span> clause determines
4471             whether
4472             the local server, acting as a slave, will request incremental zone
4473             transfers from the given remote server, a master. If not set, the
4474             value of the <span><strong class="command">request-ixfr</strong></span> option in
4475             the view or
4476             global options block is used as a default.
4477           </p>
4478 <p>
4479             IXFR requests to servers that do not support IXFR will
4480             automatically
4481             fall back to AXFR.  Therefore, there is no need to manually list
4482             which servers support IXFR and which ones do not; the global
4483             default
4484             of <span><strong class="command">yes</strong></span> should always work.
4485             The purpose of the <span><strong class="command">provide-ixfr</strong></span> and
4486             <span><strong class="command">request-ixfr</strong></span> clauses is
4487             to make it possible to disable the use of IXFR even when both
4488             master
4489             and slave claim to support it, for example if one of the servers
4490             is buggy and crashes or corrupts data when IXFR is used.
4491           </p>
4492 <p>
4493             The <span><strong class="command">edns</strong></span> clause determines whether
4494             the local server will attempt to use EDNS when communicating
4495             with the remote server.  The default is <span><strong class="command">yes</strong></span>.
4496           </p>
4497 <p>
4498             The <span><strong class="command">edns-udp-size</strong></span> option sets the EDNS UDP size
4499             that is advertised by named when querying the remote server.
4500             Valid values are 512 to 4096 bytes (values outside this range will be
4501             silently adjusted).  This option is useful when you wish to
4502             advertises a different value to this server than the value you
4503             advertise globally, for example, when there is a firewall at the
4504             remote site that is blocking large replies.
4505           </p>
4506 <p>
4507             The <span><strong class="command">max-udp-size</strong></span> option sets the
4508             maximum EDNS UDP message size named will send.  Valid
4509             values are 512 to 4096 bytes (values outside this range will
4510             be silently adjusted).  This option is useful when you
4511             know that there is a firewall that is blocking large
4512             replies from named.
4513           </p>
4514 <p>
4515             The server supports two zone transfer methods. The first, <span><strong class="command">one-answer</strong></span>,
4516             uses one DNS message per resource record transferred. <span><strong class="command">many-answers</strong></span> packs
4517             as many resource records as possible into a message. <span><strong class="command">many-answers</strong></span> is
4518             more efficient, but is only known to be understood by <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
4519             8.x, and patched versions of <acronym class="acronym">BIND</acronym>
4520             4.9.5. You can specify which method
4521             to use for a server with the <span><strong class="command">transfer-format</strong></span> option.
4522             If <span><strong class="command">transfer-format</strong></span> is not
4523             specified, the <span><strong class="command">transfer-format</strong></span>
4524             specified
4525             by the <span><strong class="command">options</strong></span> statement will be
4526             used.
4527           </p>
4528 <p><span><strong class="command">transfers</strong></span>
4529             is used to limit the number of concurrent inbound zone
4530             transfers from the specified server. If no
4531             <span><strong class="command">transfers</strong></span> clause is specified, the
4532             limit is set according to the
4533             <span><strong class="command">transfers-per-ns</strong></span> option.
4534           </p>
4535 <p>
4536             The <span><strong class="command">keys</strong></span> clause identifies a
4537             <span><strong class="command">key_id</strong></span> defined by the <span><strong class="command">key</strong></span> statement,
4538             to be used for transaction security (TSIG, <a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
4539             when talking to the remote server.
4540             When a request is sent to the remote server, a request signature
4541             will be generated using the key specified here and appended to the
4542             message. A request originating from the remote server is not
4543             required
4544             to be signed by this key.
4545           </p>
4546 <p>
4547             Although the grammar of the <span><strong class="command">keys</strong></span>
4548             clause
4549             allows for multiple keys, only a single key per server is
4550             currently
4551             supported.
4552           </p>
4553 <p>
4554             The <span><strong class="command">transfer-source</strong></span> and
4555             <span><strong class="command">transfer-source-v6</strong></span> clauses specify
4556             the IPv4 and IPv6 source
4557             address to be used for zone transfer with the remote server,
4558             respectively.
4559             For an IPv4 remote server, only <span><strong class="command">transfer-source</strong></span> can
4560             be specified.
4561             Similarly, for an IPv6 remote server, only
4562             <span><strong class="command">transfer-source-v6</strong></span> can be
4563             specified.
4564             For more details, see the description of
4565             <span><strong class="command">transfer-source</strong></span> and
4566             <span><strong class="command">transfer-source-v6</strong></span> in
4567             <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
4568           </p>
4569 <p>
4570             The <span><strong class="command">notify-source</strong></span> and
4571             <span><strong class="command">notify-source-v6</strong></span> clauses specify the
4572             IPv4 and IPv6 source address to be used for notify
4573             messages sent to remote servers, respectively.  For an
4574             IPv4 remote server, only <span><strong class="command">notify-source</strong></span>
4575             can be specified.  Similarly, for an IPv6 remote server,
4576             only <span><strong class="command">notify-source-v6</strong></span> can be specified.
4577           </p>
4578 <p>
4579             The <span><strong class="command">query-source</strong></span> and
4580             <span><strong class="command">query-source-v6</strong></span> clauses specify the
4581             IPv4 and IPv6 source address to be used for queries
4582             sent to remote servers, respectively.  For an IPv4
4583             remote server, only <span><strong class="command">query-source</strong></span> can
4584             be specified.  Similarly, for an IPv6 remote server,
4585             only <span><strong class="command">query-source-v6</strong></span> can be specified.
4586           </p>
4587 </div>
4588 <div class="sect2" lang="en">
4589 <div class="titlepage"><div><div><h3 class="title">
4590 <a name="id2585361"></a><span><strong class="command">trusted-keys</strong></span> Statement Grammar</h3></div></div></div>
4591 <pre class="programlisting">trusted-keys {
4592     <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> ;
4593     [<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>]
4594 };
4595 </pre>
4596 </div>
4597 <div class="sect2" lang="en">
4598 <div class="titlepage"><div><div><h3 class="title">
4599 <a name="id2585410"></a><span><strong class="command">trusted-keys</strong></span> Statement Definition
4600             and Usage</h3></div></div></div>
4601 <p>
4602             The <span><strong class="command">trusted-keys</strong></span> statement defines
4603             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
4604             public key for a non-authoritative zone is known, but
4605             cannot be securely obtained through DNS, either because
4606             it is the DNS root zone or because its parent zone is
4607             unsigned.  Once a key has been configured as a trusted
4608             key, it is treated as if it had been validated and
4609             proven secure. The resolver attempts DNSSEC validation
4610             on all DNS data in subdomains of a security root.
4611           </p>
4612 <p>
4613             All keys (and corresponding zones) listed in
4614             <span><strong class="command">trusted-keys</strong></span> are deemed to exist regardless
4615             of what parent zones say.  Similarly for all keys listed in
4616             <span><strong class="command">trusted-keys</strong></span> only those keys are
4617             used to validate the DNSKEY RRset.  The parent's DS RRset
4618             will not be used.
4619           </p>
4620 <p>
4621             The <span><strong class="command">trusted-keys</strong></span> statement can contain
4622             multiple key entries, each consisting of the key's
4623             domain name, flags, protocol, algorithm, and the Base-64
4624             representation of the key data.
4625           </p>
4626 </div>
4627 <div class="sect2" lang="en">
4628 <div class="titlepage"><div><div><h3 class="title">
4629 <a name="view_statement_grammar"></a><span><strong class="command">view</strong></span> Statement Grammar</h3></div></div></div>
4630 <pre class="programlisting">view <em class="replaceable"><code>view_name</code></em>
4631       [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
4632       match-clients { <em class="replaceable"><code>address_match_list</code></em> };
4633       match-destinations { <em class="replaceable"><code>address_match_list</code></em> };
4634       match-recursive-only <em class="replaceable"><code>yes_or_no</code></em> ;
4635       [<span class="optional"> <em class="replaceable"><code>view_option</code></em>; ...</span>]
4636       [<span class="optional"> <em class="replaceable"><code>zone_statement</code></em>; ...</span>]
4637 };
4638 </pre>
4639 </div>
4640 <div class="sect2" lang="en">
4641 <div class="titlepage"><div><div><h3 class="title">
4642 <a name="id2585490"></a><span><strong class="command">view</strong></span> Statement Definition and Usage</h3></div></div></div>
4643 <p>
4644             The <span><strong class="command">view</strong></span> statement is a powerful
4645             feature
4646             of <acronym class="acronym">BIND</acronym> 9 that lets a name server
4647             answer a DNS query differently
4648             depending on who is asking. It is particularly useful for
4649             implementing
4650             split DNS setups without having to run multiple servers.
4651           </p>
4652 <p>
4653             Each <span><strong class="command">view</strong></span> statement defines a view
4654             of the
4655             DNS namespace that will be seen by a subset of clients.  A client
4656             matches
4657             a view if its source IP address matches the
4658             <code class="varname">address_match_list</code> of the view's
4659             <span><strong class="command">match-clients</strong></span> clause and its
4660             destination IP address matches
4661             the <code class="varname">address_match_list</code> of the
4662             view's
4663             <span><strong class="command">match-destinations</strong></span> clause.  If not
4664             specified, both
4665             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
4666             default to matching all addresses.  In addition to checking IP
4667             addresses
4668             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
4669             can also take <span><strong class="command">keys</strong></span> which provide an
4670             mechanism for the
4671             client to select the view.  A view can also be specified
4672             as <span><strong class="command">match-recursive-only</strong></span>, which
4673             means that only recursive
4674             requests from matching clients will match that view.
4675             The order of the <span><strong class="command">view</strong></span> statements is
4676             significant &#8212;
4677             a client request will be resolved in the context of the first
4678             <span><strong class="command">view</strong></span> that it matches.
4679           </p>
4680 <p>
4681             Zones defined within a <span><strong class="command">view</strong></span>
4682             statement will
4683             be only be accessible to clients that match the <span><strong class="command">view</strong></span>.
4684             By defining a zone of the same name in multiple views, different
4685             zone data can be given to different clients, for example,
4686             "internal"
4687             and "external" clients in a split DNS setup.
4688           </p>
4689 <p>
4690             Many of the options given in the <span><strong class="command">options</strong></span> statement
4691             can also be used within a <span><strong class="command">view</strong></span>
4692             statement, and then
4693             apply only when resolving queries with that view.  When no
4694             view-specific
4695             value is given, the value in the <span><strong class="command">options</strong></span> statement
4696             is used as a default.  Also, zone options can have default values
4697             specified
4698             in the <span><strong class="command">view</strong></span> statement; these
4699             view-specific defaults
4700             take precedence over those in the <span><strong class="command">options</strong></span> statement.
4701           </p>
4702 <p>
4703             Views are class specific.  If no class is given, class IN
4704             is assumed.  Note that all non-IN views must contain a hint zone,
4705             since only the IN class has compiled-in default hints.
4706           </p>
4707 <p>
4708             If there are no <span><strong class="command">view</strong></span> statements in
4709             the config
4710             file, a default view that matches any client is automatically
4711             created
4712             in class IN. Any <span><strong class="command">zone</strong></span> statements
4713             specified on
4714             the top level of the configuration file are considered to be part
4715             of
4716             this default view, and the <span><strong class="command">options</strong></span>
4717             statement will
4718             apply to the default view. If any explicit <span><strong class="command">view</strong></span>
4719             statements are present, all <span><strong class="command">zone</strong></span>
4720             statements must
4721             occur inside <span><strong class="command">view</strong></span> statements.
4722           </p>
4723 <p>
4724             Here is an example of a typical split DNS setup implemented
4725             using <span><strong class="command">view</strong></span> statements:
4726           </p>
4727 <pre class="programlisting">view "internal" {
4728       // This should match our internal networks.
4729       match-clients { 10.0.0.0/8; };
4730
4731       // Provide recursive service to internal clients only.
4732       recursion yes;
4733
4734       // Provide a complete view of the example.com zone
4735       // including addresses of internal hosts.
4736       zone "example.com" {
4737             type master;
4738             file "example-internal.db";
4739       };
4740 };
4741
4742 view "external" {
4743       // Match all clients not matched by the previous view.
4744       match-clients { any; };
4745
4746       // Refuse recursive service to external clients.
4747       recursion no;
4748
4749       // Provide a restricted view of the example.com zone
4750       // containing only publicly accessible hosts.
4751       zone "example.com" {
4752            type master;
4753            file "example-external.db";
4754       };
4755 };
4756 </pre>
4757 </div>
4758 <div class="sect2" lang="en">
4759 <div class="titlepage"><div><div><h3 class="title">
4760 <a name="zone_statement_grammar"></a><span><strong class="command">zone</strong></span>
4761             Statement Grammar</h3></div></div></div>
4762 <pre class="programlisting">zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
4763     type master;
4764     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
4765     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
4766     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
4767     [<span class="optional"> update-policy { <em class="replaceable"><code>update_policy_rule</code></em> [<span class="optional">...</span>] }; </span>]
4768     [<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>] ; [<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>]
4769     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
4770     [<span class="optional"> check-mx (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
4771     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
4772     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4773     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
4774     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
4775     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
4776     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
4777     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
4778     [<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>]
4779     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
4780     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
4781     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4782     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
4783     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
4784     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
4785     [<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>]
4786     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
4787     [<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>]
4788     [<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>]
4789     [<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>]
4790     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4791     [<span class="optional"> sig-validity-interval <em class="replaceable"><code>number</code></em> ; </span>]
4792     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
4793     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
4794     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
4795     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
4796     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
4797     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
4798     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4799 };
4800
4801 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
4802     type slave;
4803     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
4804     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
4805     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
4806     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
4807     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
4808     [<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>] ; [<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>]
4809     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
4810     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
4811     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
4812     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
4813     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
4814     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
4815     [<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>]
4816     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
4817     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
4818     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4819     [<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> [<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>] }; </span>]
4820     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
4821     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
4822     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
4823     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
4824     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
4825     [<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>]
4826     [<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>]
4827     [<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>]
4828     [<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>]
4829     [<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>]
4830     [<span class="optional"> alt-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>]
4831     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
4832     [<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>]
4833     [<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>]
4834     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4835     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
4836     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
4837     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
4838     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
4839     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
4840     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4841     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4842 };
4843
4844 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
4845     type hint;
4846     file <em class="replaceable"><code>string</code></em> ;
4847     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4848     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; // Not Implemented. </span>]
4849 };
4850
4851 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
4852     type stub;
4853     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
4854     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
4855     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
4856     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4857     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
4858     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
4859     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
4860     [<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>]
4861     [<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> [<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>] }; </span>]
4862     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
4863     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
4864     [<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>]
4865     [<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>]
4866     [<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>]
4867     [<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>]
4868     [<span class="optional"> alt-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>]
4869     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
4870     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4871     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
4872     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
4873     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
4874     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
4875     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
4876     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4877 };
4878
4879 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
4880     type forward;
4881     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
4882     [<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>]
4883     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4884 };
4885
4886 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
4887     type delegation-only;
4888 };
4889
4890 </pre>
4891 </div>
4892 <div class="sect2" lang="en">
4893 <div class="titlepage"><div><div><h3 class="title">
4894 <a name="id2586798"></a><span><strong class="command">zone</strong></span> Statement Definition and Usage</h3></div></div></div>
4895 <div class="sect3" lang="en">
4896 <div class="titlepage"><div><div><h4 class="title">
4897 <a name="id2586806"></a>Zone Types</h4></div></div></div>
4898 <div class="informaltable"><table border="1">
4899 <colgroup>
4900 <col>
4901 <col>
4902 </colgroup>
4903 <tbody>
4904 <tr>
4905 <td>
4906                       <p>
4907                         <code class="varname">master</code>
4908                       </p>
4909                     </td>
4910 <td>
4911                       <p>
4912                         The server has a master copy of the data
4913                         for the zone and will be able to provide authoritative
4914                         answers for
4915                         it.
4916                       </p>
4917                     </td>
4918 </tr>
4919 <tr>
4920 <td>
4921                       <p>
4922                         <code class="varname">slave</code>
4923                       </p>
4924                     </td>
4925 <td>
4926                       <p>
4927                         A slave zone is a replica of a master
4928                         zone. The <span><strong class="command">masters</strong></span> list
4929                         specifies one or more IP addresses
4930                         of master servers that the slave contacts to update
4931                         its copy of the zone.
4932                         Masters list elements can also be names of other
4933                         masters lists.
4934                         By default, transfers are made from port 53 on the
4935                         servers; this can
4936                         be changed for all servers by specifying a port number
4937                         before the
4938                         list of IP addresses, or on a per-server basis after
4939                         the IP address.
4940                         Authentication to the master can also be done with
4941                         per-server TSIG keys.
4942                         If a file is specified, then the
4943                         replica will be written to this file whenever the zone
4944                         is changed,
4945                         and reloaded from this file on a server restart. Use
4946                         of a file is
4947                         recommended, since it often speeds server startup and
4948                         eliminates
4949                         a needless waste of bandwidth. Note that for large
4950                         numbers (in the
4951                         tens or hundreds of thousands) of zones per server, it
4952                         is best to
4953                         use a two-level naming scheme for zone filenames. For
4954                         example,
4955                         a slave server for the zone <code class="literal">example.com</code> might place
4956                         the zone contents into a file called
4957                         <code class="filename">ex/example.com</code> where <code class="filename">ex/</code> is
4958                         just the first two letters of the zone name. (Most
4959                         operating systems
4960                         behave very slowly if you put 100 000 files into
4961                         a single directory.)
4962                       </p>
4963                     </td>
4964 </tr>
4965 <tr>
4966 <td>
4967                       <p>
4968                         <code class="varname">stub</code>
4969                       </p>
4970                     </td>
4971 <td>
4972                       <p>
4973                         A stub zone is similar to a slave zone,
4974                         except that it replicates only the NS records of a
4975                         master zone instead
4976                         of the entire zone. Stub zones are not a standard part
4977                         of the DNS;
4978                         they are a feature specific to the <acronym class="acronym">BIND</acronym> implementation.
4979                       </p>
4980
4981                       <p>
4982                         Stub zones can be used to eliminate the need for glue
4983                         NS record
4984                         in a parent zone at the expense of maintaining a stub
4985                         zone entry and
4986                         a set of name server addresses in <code class="filename">named.conf</code>.
4987                         This usage is not recommended for new configurations,
4988                         and BIND 9
4989                         supports it only in a limited way.
4990                         In <acronym class="acronym">BIND</acronym> 4/8, zone
4991                         transfers of a parent zone
4992                         included the NS records from stub children of that
4993                         zone. This meant
4994                         that, in some cases, users could get away with
4995                         configuring child stubs
4996                         only in the master server for the parent zone. <acronym class="acronym">BIND</acronym>
4997                         9 never mixes together zone data from different zones
4998                         in this
4999                         way. Therefore, if a <acronym class="acronym">BIND</acronym> 9 master serving a parent
5000                         zone has child stub zones configured, all the slave
5001                         servers for the
5002                         parent zone also need to have the same child stub
5003                         zones
5004                         configured.
5005                       </p>
5006
5007                       <p>
5008                         Stub zones can also be used as a way of forcing the
5009                         resolution
5010                         of a given domain to use a particular set of
5011                         authoritative servers.
5012                         For example, the caching name servers on a private
5013                         network using
5014                         RFC1918 addressing may be configured with stub zones
5015                         for
5016                         <code class="literal">10.in-addr.arpa</code>
5017                         to use a set of internal name servers as the
5018                         authoritative
5019                         servers for that domain.
5020                       </p>
5021                     </td>
5022 </tr>
5023 <tr>
5024 <td>
5025                       <p>
5026                         <code class="varname">forward</code>
5027                       </p>
5028                     </td>
5029 <td>
5030                       <p>
5031                         A "forward zone" is a way to configure
5032                         forwarding on a per-domain basis.  A <span><strong class="command">zone</strong></span> statement
5033                         of type <span><strong class="command">forward</strong></span> can
5034                         contain a <span><strong class="command">forward</strong></span>
5035                         and/or <span><strong class="command">forwarders</strong></span>
5036                         statement,
5037                         which will apply to queries within the domain given by
5038                         the zone
5039                         name. If no <span><strong class="command">forwarders</strong></span>
5040                         statement is present or
5041                         an empty list for <span><strong class="command">forwarders</strong></span> is given, then no
5042                         forwarding will be done for the domain, canceling the
5043                         effects of
5044                         any forwarders in the <span><strong class="command">options</strong></span> statement. Thus
5045                         if you want to use this type of zone to change the
5046                         behavior of the
5047                         global <span><strong class="command">forward</strong></span> option
5048                         (that is, "forward first"
5049                         to, then "forward only", or vice versa, but want to
5050                         use the same
5051                         servers as set globally) you need to re-specify the
5052                         global forwarders.
5053                       </p>
5054                     </td>
5055 </tr>
5056 <tr>
5057 <td>
5058                       <p>
5059                         <code class="varname">hint</code>
5060                       </p>
5061                     </td>
5062 <td>
5063                       <p>
5064                         The initial set of root name servers is
5065                         specified using a "hint zone". When the server starts
5066                         up, it uses
5067                         the root hints to find a root name server and get the
5068                         most recent
5069                         list of root name servers. If no hint zone is
5070                         specified for class
5071                         IN, the server uses a compiled-in default set of root
5072                         servers hints.
5073                         Classes other than IN have no built-in defaults hints.
5074                       </p>
5075                     </td>
5076 </tr>
5077 <tr>
5078 <td>
5079                       <p>
5080                         <code class="varname">delegation-only</code>
5081                       </p>
5082                     </td>
5083 <td>
5084                       <p>
5085                         This is used to enforce the delegation-only
5086                         status of infrastructure zones (e.g. COM, NET, ORG).
5087                         Any answer that
5088                         is received without an explicit or implicit delegation
5089                         in the authority
5090                         section will be treated as NXDOMAIN.  This does not
5091                         apply to the zone
5092                         apex.  This should not be applied to leaf zones.
5093                       </p>
5094                       <p>
5095                         <code class="varname">delegation-only</code> has no
5096                         effect on answers received
5097                         from forwarders.
5098                       </p>
5099                     </td>
5100 </tr>
5101 </tbody>
5102 </table></div>
5103 </div>
5104 <div class="sect3" lang="en">
5105 <div class="titlepage"><div><div><h4 class="title">
5106 <a name="id2587362"></a>Class</h4></div></div></div>
5107 <p>
5108               The zone's name may optionally be followed by a class. If
5109               a class is not specified, class <code class="literal">IN</code> (for <code class="varname">Internet</code>),
5110               is assumed. This is correct for the vast majority of cases.
5111             </p>
5112 <p>
5113               The <code class="literal">hesiod</code> class is
5114               named for an information service from MIT's Project Athena. It
5115               is
5116               used to share information about various systems databases, such
5117               as users, groups, printers and so on. The keyword
5118               <code class="literal">HS</code> is
5119               a synonym for hesiod.
5120             </p>
5121 <p>
5122               Another MIT development is Chaosnet, a LAN protocol created
5123               in the mid-1970s. Zone data for it can be specified with the <code class="literal">CHAOS</code> class.
5124             </p>
5125 </div>
5126 <div class="sect3" lang="en">
5127 <div class="titlepage"><div><div><h4 class="title">
5128 <a name="id2587395"></a>Zone Options</h4></div></div></div>
5129 <div class="variablelist"><dl>
5130 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
5131 <dd><p>
5132                     See the description of
5133                     <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>.
5134                   </p></dd>
5135 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
5136 <dd><p>
5137                     See the description of
5138                     <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>.
5139                   </p></dd>
5140 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
5141 <dd><p>
5142                     See the description of <span><strong class="command">allow-transfer</strong></span>
5143                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
5144                   </p></dd>
5145 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
5146 <dd><p>
5147                     See the description of <span><strong class="command">allow-update</strong></span>
5148                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
5149                   </p></dd>
5150 <dt><span class="term"><span><strong class="command">update-policy</strong></span></span></dt>
5151 <dd><p>
5152                     Specifies a "Simple Secure Update" policy. See
5153                     <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>.
5154                   </p></dd>
5155 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
5156 <dd><p>
5157                     See the description of <span><strong class="command">allow-update-forwarding</strong></span>
5158                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
5159                   </p></dd>
5160 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
5161 <dd><p>
5162                     Only meaningful if <span><strong class="command">notify</strong></span>
5163                     is
5164                     active for this zone. The set of machines that will
5165                     receive a
5166                     <code class="literal">DNS NOTIFY</code> message
5167                     for this zone is made up of all the listed name servers
5168                     (other than
5169                     the primary master) for the zone plus any IP addresses
5170                     specified
5171                     with <span><strong class="command">also-notify</strong></span>. A port
5172                     may be specified
5173                     with each <span><strong class="command">also-notify</strong></span>
5174                     address to send the notify
5175                     messages to a port other than the default of 53.
5176                     <span><strong class="command">also-notify</strong></span> is not
5177                     meaningful for stub zones.
5178                     The default is the empty list.
5179                   </p></dd>
5180 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
5181 <dd><p>
5182                     This option is used to restrict the character set and
5183                     syntax of
5184                     certain domain names in master files and/or DNS responses
5185                     received from the
5186                     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>
5187                     zones the default is <span><strong class="command">warn</strong></span>.
5188                   </p></dd>
5189 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
5190 <dd><p>
5191                     See the description of
5192                     <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>.
5193                   </p></dd>
5194 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
5195 <dd><p>
5196                     See the description of
5197                     <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>.
5198                   </p></dd>
5199 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
5200 <dd><p>
5201                     See the description of
5202                     <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>.
5203                   </p></dd>
5204 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
5205 <dd><p>
5206                     See the description of
5207                     <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>.
5208                   </p></dd>
5209 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
5210 <dd><p>
5211                     See the description of
5212                     <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>.
5213                   </p></dd>
5214 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
5215 <dd><p>
5216                     See the description of
5217                     <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>.
5218                   </p></dd>
5219 <dt><span class="term"><span><strong class="command">database</strong></span></span></dt>
5220 <dd>
5221 <p>
5222                     Specify the type of database to be used for storing the
5223                     zone data.  The string following the <span><strong class="command">database</strong></span> keyword
5224                     is interpreted as a list of whitespace-delimited words.
5225                     The first word
5226                     identifies the database type, and any subsequent words are
5227                     passed
5228                     as arguments to the database to be interpreted in a way
5229                     specific
5230                     to the database type.
5231                   </p>
5232 <p>
5233                     The default is <strong class="userinput"><code>"rbt"</code></strong>, BIND 9's
5234                     native in-memory
5235                     red-black-tree database.  This database does not take
5236                     arguments.
5237                   </p>
5238 <p>
5239                     Other values are possible if additional database drivers
5240                     have been linked into the server.  Some sample drivers are
5241                     included
5242                     with the distribution but none are linked in by default.
5243                   </p>
5244 </dd>
5245 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
5246 <dd><p>
5247                     See the description of
5248                     <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>.
5249                   </p></dd>
5250 <dt><span class="term"><span><strong class="command">delegation-only</strong></span></span></dt>
5251 <dd><p>
5252                     The flag only applies to hint and stub zones.  If set
5253                     to <strong class="userinput"><code>yes</code></strong>, then the zone will also be
5254                     treated as if it
5255                     is also a delegation-only type zone.
5256                   </p></dd>
5257 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
5258 <dd><p>
5259                     Only meaningful if the zone has a forwarders
5260                     list. The <span><strong class="command">only</strong></span> value causes
5261                     the lookup to fail
5262                     after trying the forwarders and getting no answer, while <span><strong class="command">first</strong></span> would
5263                     allow a normal lookup to be tried.
5264                   </p></dd>
5265 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
5266 <dd><p>
5267                     Used to override the list of global forwarders.
5268                     If it is not specified in a zone of type <span><strong class="command">forward</strong></span>,
5269                     no forwarding is done for the zone and the global options are
5270                     not used.
5271                   </p></dd>
5272 <dt><span class="term"><span><strong class="command">ixfr-base</strong></span></span></dt>
5273 <dd><p>
5274                     Was used in <acronym class="acronym">BIND</acronym> 8 to
5275                     specify the name
5276                     of the transaction log (journal) file for dynamic update
5277                     and IXFR.
5278                     <acronym class="acronym">BIND</acronym> 9 ignores the option
5279                     and constructs the name of the journal
5280                     file by appending "<code class="filename">.jnl</code>"
5281                     to the name of the
5282                     zone file.
5283                   </p></dd>
5284 <dt><span class="term"><span><strong class="command">ixfr-tmp-file</strong></span></span></dt>
5285 <dd><p>
5286                     Was an undocumented option in <acronym class="acronym">BIND</acronym> 8.
5287                     Ignored in <acronym class="acronym">BIND</acronym> 9.
5288                   </p></dd>
5289 <dt><span class="term"><span><strong class="command">journal</strong></span></span></dt>
5290 <dd><p>
5291                     Allow the default journal's filename to be overridden.
5292                     The default is the zone's filename with "<code class="filename">.jnl</code>" appended.
5293                     This is applicable to <span><strong class="command">master</strong></span> and <span><strong class="command">slave</strong></span> zones.
5294                   </p></dd>
5295 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
5296 <dd><p>
5297                     See the description of
5298                     <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>.
5299                   </p></dd>
5300 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
5301 <dd><p>
5302                     See the description of
5303                     <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>.
5304                   </p></dd>
5305 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
5306 <dd><p>
5307                     See the description of
5308                     <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>.
5309                   </p></dd>
5310 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
5311 <dd><p>
5312                     See the description of
5313                     <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>.
5314                   </p></dd>
5315 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
5316 <dd><p>
5317                     See the description of
5318                     <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>.
5319                   </p></dd>
5320 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
5321 <dd><p>
5322                     See the description of
5323                     <span><strong class="command">notify-delay</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
5324                   </p></dd>
5325 <dt><span class="term"><span><strong class="command">pubkey</strong></span></span></dt>
5326 <dd><p>
5327                     In <acronym class="acronym">BIND</acronym> 8, this option was
5328                     intended for specifying
5329                     a public zone key for verification of signatures in DNSSEC
5330                     signed
5331                     zones when they are loaded from disk. <acronym class="acronym">BIND</acronym> 9 does not verify signatures
5332                     on load and ignores the option.
5333                   </p></dd>
5334 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
5335 <dd><p>
5336                     If <strong class="userinput"><code>yes</code></strong>, the server will keep
5337                     statistical
5338                     information for this zone, which can be dumped to the
5339                     <span><strong class="command">statistics-file</strong></span> defined in
5340                     the server options.
5341                   </p></dd>
5342 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
5343 <dd><p>
5344                     See the description of
5345                     <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>.
5346                   </p></dd>
5347 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
5348 <dd><p>
5349                     See the description of
5350                     <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>.
5351                   </p></dd>
5352 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
5353 <dd><p>
5354                     See the description of
5355                     <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>.
5356                   </p></dd>
5357 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
5358 <dd><p>
5359                     See the description of
5360                     <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>.
5361                   </p></dd>
5362 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
5363 <dd><p>
5364                     See the description of
5365                     <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>.
5366                   </p></dd>
5367 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
5368 <dd><p>
5369                     See the description of
5370                     <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>.
5371                   </p></dd>
5372 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
5373 <dd><p>
5374                     See the description of
5375                     <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>.
5376                   </p></dd>
5377 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
5378 <dd><p>
5379                     See the description of
5380                     <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>.
5381                   </p></dd>
5382 <dt>
5383 <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>
5384 </dt>
5385 <dd><p>
5386                     See the description in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
5387                   </p></dd>
5388 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
5389 <dd><p>
5390                     See the description of
5391                     <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>.
5392                   </p></dd>
5393 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
5394 <dd><p>
5395                     See the description of
5396                     <span><strong class="command">key-directory</strong></span> in <a href="Bv9ARM.ch06.html#options" title="options Statement Definition and
5397           Usage">the section called &#8220;<span><strong class="command">options</strong></span> Statement Definition and
5398           Usage&#8221;</a>.
5399                   </p></dd>
5400 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
5401 <dd><p>
5402                     See the description of <span><strong class="command">multi-master</strong></span> in
5403                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
5404                   </p></dd>
5405 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
5406 <dd><p>
5407                     See the description of <span><strong class="command">masterfile-format</strong></span>
5408                     in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
5409                   </p></dd>
5410 </dl></div>
5411 </div>
5412 <div class="sect3" lang="en">
5413 <div class="titlepage"><div><div><h4 class="title">
5414 <a name="dynamic_update_policies"></a>Dynamic Update Policies</h4></div></div></div>
5415 <p>
5416               <acronym class="acronym">BIND</acronym> 9 supports two alternative
5417               methods of granting clients
5418               the right to perform dynamic updates to a zone,
5419               configured by the <span><strong class="command">allow-update</strong></span>
5420               and
5421               <span><strong class="command">update-policy</strong></span> option,
5422               respectively.
5423             </p>
5424 <p>
5425               The <span><strong class="command">allow-update</strong></span> clause works the
5426               same
5427               way as in previous versions of <acronym class="acronym">BIND</acronym>. It grants given clients the
5428               permission to update any record of any name in the zone.
5429             </p>
5430 <p>
5431               The <span><strong class="command">update-policy</strong></span> clause is new
5432               in <acronym class="acronym">BIND</acronym>
5433               9 and allows more fine-grained control over what updates are
5434               allowed.
5435               A set of rules is specified, where each rule either grants or
5436               denies
5437               permissions for one or more names to be updated by one or more
5438               identities.
5439               If the dynamic update request message is signed (that is, it
5440               includes
5441               either a TSIG or SIG(0) record), the identity of the signer can
5442               be determined.
5443             </p>
5444 <p>
5445               Rules are specified in the <span><strong class="command">update-policy</strong></span> zone
5446               option, and are only meaningful for master zones.  When the <span><strong class="command">update-policy</strong></span> statement
5447               is present, it is a configuration error for the <span><strong class="command">allow-update</strong></span> statement
5448               to be present.  The <span><strong class="command">update-policy</strong></span>
5449               statement only
5450               examines the signer of a message; the source address is not
5451               relevant.
5452             </p>
5453 <p>
5454               This is how a rule definition looks:
5455             </p>
5456 <pre class="programlisting">
5457 ( <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> <em class="replaceable"><code>name</code></em> [<span class="optional"> <em class="replaceable"><code>types</code></em> </span>]
5458 </pre>
5459 <p>
5460               Each rule grants or denies privileges.  Once a message has
5461               successfully matched a rule, the operation is immediately
5462               granted
5463               or denied and no further rules are examined.  A rule is matched
5464               when the signer matches the identity field, the name matches the
5465               name field in accordance with the nametype field, and the type
5466               matches
5467               the types specified in the type field.
5468             </p>
5469 <p>
5470               The identity field specifies a name or a wildcard name.
5471               Normally, this
5472               is the name of the TSIG or SIG(0) key used to sign the update
5473               request.  When a
5474               TKEY exchange has been used to create a shared secret, the
5475               identity of the
5476               shared secret is the same as the identity of the key used to
5477               authenticate the
5478               TKEY exchange.  When the <em class="replaceable"><code>identity</code></em> field specifies a
5479               wildcard name, it is subject to DNS wildcard expansion, so the
5480               rule will apply
5481               to multiple identities.  The <em class="replaceable"><code>identity</code></em> field must
5482               contain a fully-qualified domain name.
5483             </p>
5484 <p>
5485               The <em class="replaceable"><code>nametype</code></em> field has 6
5486               values:
5487               <code class="varname">name</code>, <code class="varname">subdomain</code>,
5488               <code class="varname">wildcard</code>, <code class="varname">self</code>,
5489                <code class="varname">selfsub</code>, and <code class="varname">selfwild</code>.
5490             </p>
5491 <div class="informaltable"><table border="1">
5492 <colgroup>
5493 <col>
5494 <col>
5495 </colgroup>
5496 <tbody>
5497 <tr>
5498 <td>
5499                       <p>
5500                         <code class="varname">name</code>
5501                       </p>
5502                     </td>
5503 <td>
5504                       <p>
5505                         Exact-match semantics.  This rule matches
5506                         when the name being updated is identical
5507                         to the contents of the
5508                         <em class="replaceable"><code>name</code></em> field.
5509                       </p>
5510                     </td>
5511 </tr>
5512 <tr>
5513 <td>
5514                       <p>
5515                         <code class="varname">subdomain</code>
5516                       </p>
5517                     </td>
5518 <td>
5519                       <p>
5520                         This rule matches when the name being updated
5521                         is a subdomain of, or identical to, the
5522                         contents of the <em class="replaceable"><code>name</code></em>
5523                         field.
5524                       </p>
5525                     </td>
5526 </tr>
5527 <tr>
5528 <td>
5529                       <p>
5530                         <code class="varname">wildcard</code>
5531                       </p>
5532                     </td>
5533 <td>
5534                       <p>
5535                         The <em class="replaceable"><code>name</code></em> field
5536                         is subject to DNS wildcard expansion, and
5537                         this rule matches when the name being updated
5538                         name is a valid expansion of the wildcard.
5539                       </p>
5540                     </td>
5541 </tr>
5542 <tr>
5543 <td>
5544                       <p>
5545                         <code class="varname">self</code>
5546                       </p>
5547                     </td>
5548 <td>
5549                       <p>
5550                         This rule matches when the name being updated
5551                         matches the contents of the
5552                         <em class="replaceable"><code>identity</code></em> field.
5553                         The <em class="replaceable"><code>name</code></em> field
5554                         is ignored, but should be the same as the
5555                         <em class="replaceable"><code>identity</code></em> field.
5556                         The <code class="varname">self</code> nametype is
5557                         most useful when allowing using one key per
5558                         name to update, where the key has the same
5559                         name as the name to be updated.  The
5560                         <em class="replaceable"><code>identity</code></em> would
5561                         be specified as <code class="constant">*</code> (an asterisk) in
5562                         this case.
5563                       </p>
5564                     </td>
5565 </tr>
5566 <tr>
5567 <td>
5568                       <p>
5569                         <code class="varname">selfsub</code>
5570                       </p>
5571                     </td>
5572 <td>
5573                       <p>
5574                         This rule is similar to <code class="varname">self</code>
5575                         except that subdomains of <code class="varname">self</code>
5576                         can also be updated.
5577                       </p>
5578                     </td>
5579 </tr>
5580 <tr>
5581 <td>
5582                       <p>
5583                         <code class="varname">selfwild</code>
5584                       </p>
5585                     </td>
5586 <td>
5587                       <p>
5588                         This rule is similar to <code class="varname">self</code>
5589                         except that only subdomains of
5590                         <code class="varname">self</code> can be updated.
5591                       </p>
5592                     </td>
5593 </tr>
5594 </tbody>
5595 </table></div>
5596 <p>
5597               In all cases, the <em class="replaceable"><code>name</code></em>
5598               field must
5599               specify a fully-qualified domain name.
5600             </p>
5601 <p>
5602               If no types are explicitly specified, this rule matches all
5603               types except
5604               RRSIG, NS, SOA, and NSEC. Types may be specified by name, including
5605               "ANY" (ANY matches all types except NSEC, which can never be
5606               updated).
5607               Note that when an attempt is made to delete all records
5608               associated with a
5609               name, the rules are checked for each existing record type.
5610             </p>
5611 </div>
5612 </div>
5613 </div>
5614 <div class="sect1" lang="en">
5615 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
5616 <a name="id2589080"></a>Zone File</h2></div></div></div>
5617 <div class="sect2" lang="en">
5618 <div class="titlepage"><div><div><h3 class="title">
5619 <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>
5620 <p>
5621             This section, largely borrowed from RFC 1034, describes the
5622             concept of a Resource Record (RR) and explains when each is used.
5623             Since the publication of RFC 1034, several new RRs have been
5624             identified
5625             and implemented in the DNS. These are also included.
5626           </p>
5627 <div class="sect3" lang="en">
5628 <div class="titlepage"><div><div><h4 class="title">
5629 <a name="id2589098"></a>Resource Records</h4></div></div></div>
5630 <p>
5631               A domain name identifies a node.  Each node has a set of
5632               resource information, which may be empty.  The set of resource
5633               information associated with a particular name is composed of
5634               separate RRs. The order of RRs in a set is not significant and
5635               need not be preserved by name servers, resolvers, or other
5636               parts of the DNS. However, sorting of multiple RRs is
5637               permitted for optimization purposes, for example, to specify
5638               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>.
5639             </p>
5640 <p>
5641               The components of a Resource Record are:
5642             </p>
5643 <div class="informaltable"><table border="1">
5644 <colgroup>
5645 <col>
5646 <col>
5647 </colgroup>
5648 <tbody>
5649 <tr>
5650 <td>
5651                       <p>
5652                         owner name
5653                       </p>
5654                     </td>
5655 <td>
5656                       <p>
5657                         The domain name where the RR is found.
5658                       </p>
5659                     </td>
5660 </tr>
5661 <tr>
5662 <td>
5663                       <p>
5664                         type
5665                       </p>
5666                     </td>
5667 <td>
5668                       <p>
5669                         An encoded 16-bit value that specifies
5670                         the type of the resource record.
5671                       </p>
5672                     </td>
5673 </tr>
5674 <tr>
5675 <td>
5676                       <p>
5677                         TTL
5678                       </p>
5679                     </td>
5680 <td>
5681                       <p>
5682                         The time-to-live of the RR. This field
5683                         is a 32-bit integer in units of seconds, and is
5684                         primarily used by
5685                         resolvers when they cache RRs. The TTL describes how
5686                         long a RR can
5687                         be cached before it should be discarded.
5688                       </p>
5689                     </td>
5690 </tr>
5691 <tr>
5692 <td>
5693                       <p>
5694                         class
5695                       </p>
5696                     </td>
5697 <td>
5698                       <p>
5699                         An encoded 16-bit value that identifies
5700                         a protocol family or instance of a protocol.
5701                       </p>
5702                     </td>
5703 </tr>
5704 <tr>
5705 <td>
5706                       <p>
5707                         RDATA
5708                       </p>
5709                     </td>
5710 <td>
5711                       <p>
5712                         The resource data.  The format of the
5713                         data is type (and sometimes class) specific.
5714                       </p>
5715                     </td>
5716 </tr>
5717 </tbody>
5718 </table></div>
5719 <p>
5720               The following are <span class="emphasis"><em>types</em></span> of valid RRs:
5721             </p>
5722 <div class="informaltable"><table border="1">
5723 <colgroup>
5724 <col>
5725 <col>
5726 </colgroup>
5727 <tbody>
5728 <tr>
5729 <td>
5730                       <p>
5731                         A
5732                       </p>
5733                     </td>
5734 <td>
5735                       <p>
5736                         A host address.  In the IN class, this is a
5737                         32-bit IP address.  Described in RFC 1035.
5738                       </p>
5739                     </td>
5740 </tr>
5741 <tr>
5742 <td>
5743                       <p>
5744                         AAAA
5745                       </p>
5746                     </td>
5747 <td>
5748                       <p>
5749                         IPv6 address.  Described in RFC 1886.
5750                       </p>
5751                     </td>
5752 </tr>
5753 <tr>
5754 <td>
5755                       <p>
5756                         A6
5757                       </p>
5758                     </td>
5759 <td>
5760                       <p>
5761                         IPv6 address.  This can be a partial
5762                         address (a suffix) and an indirection to the name
5763                         where the rest of the
5764                         address (the prefix) can be found.  Experimental.
5765                         Described in RFC 2874.
5766                       </p>
5767                     </td>
5768 </tr>
5769 <tr>
5770 <td>
5771                       <p>
5772                         AFSDB
5773                       </p>
5774                     </td>
5775 <td>
5776                       <p>
5777                         Location of AFS database servers.
5778                         Experimental.  Described in RFC 1183.
5779                       </p>
5780                     </td>
5781 </tr>
5782 <tr>
5783 <td>
5784                       <p>
5785                         APL
5786                       </p>
5787                     </td>
5788 <td>
5789                       <p>
5790                         Address prefix list.  Experimental.
5791                         Described in RFC 3123.
5792                       </p>
5793                     </td>
5794 </tr>
5795 <tr>
5796 <td>
5797                       <p>
5798                         CERT
5799                       </p>
5800                     </td>
5801 <td>
5802                       <p>
5803                         Holds a digital certificate.
5804                         Described in RFC 2538.
5805                       </p>
5806                     </td>
5807 </tr>
5808 <tr>
5809 <td>
5810                       <p>
5811                         CNAME
5812                       </p>
5813                     </td>
5814 <td>
5815                       <p>
5816                         Identifies the canonical name of an alias.
5817                         Described in RFC 1035.
5818                       </p>
5819                     </td>
5820 </tr>
5821 <tr>
5822 <td>
5823                       <p>
5824                         DNAME
5825                       </p>
5826                     </td>
5827 <td>
5828                       <p>
5829                         Replaces the domain name specified with
5830                         another name to be looked up, effectively aliasing an
5831                         entire
5832                         subtree of the domain name space rather than a single
5833                         record
5834                         as in the case of the CNAME RR.
5835                         Described in RFC 2672.
5836                       </p>
5837                     </td>
5838 </tr>
5839 <tr>
5840 <td>
5841                       <p>
5842                         DNSKEY
5843                       </p>
5844                     </td>
5845 <td>
5846                       <p>
5847                         Stores a public key associated with a signed
5848                         DNS zone.  Described in RFC 4034.
5849                       </p>
5850                     </td>
5851 </tr>
5852 <tr>
5853 <td>
5854                       <p>
5855                         DS
5856                       </p>
5857                     </td>
5858 <td>
5859                       <p>
5860                         Stores the hash of a public key associated with a
5861                         signed DNS zone.  Described in RFC 4034.
5862                       </p>
5863                     </td>
5864 </tr>
5865 <tr>
5866 <td>
5867                       <p>
5868                         GPOS
5869                       </p>
5870                     </td>
5871 <td>
5872                       <p>
5873                         Specifies the global position.  Superseded by LOC.
5874                       </p>
5875                     </td>
5876 </tr>
5877 <tr>
5878 <td>
5879                       <p>
5880                         HINFO
5881                       </p>
5882                     </td>
5883 <td>
5884                       <p>
5885                         Identifies the CPU and OS used by a host.
5886                         Described in RFC 1035.
5887                       </p>
5888                     </td>
5889 </tr>
5890 <tr>
5891 <td>
5892                       <p>
5893                         ISDN
5894                       </p>
5895                     </td>
5896 <td>
5897                       <p>
5898                         Representation of ISDN addresses.
5899                         Experimental.  Described in RFC 1183.
5900                       </p>
5901                     </td>
5902 </tr>
5903 <tr>
5904 <td>
5905                       <p>
5906                         KEY
5907                       </p>
5908                     </td>
5909 <td>
5910                       <p>
5911                         Stores a public key associated with a
5912                         DNS name.  Used in original DNSSEC; replaced
5913                         by DNSKEY in DNSSECbis, but still used with
5914                         SIG(0).  Described in RFCs 2535 and 2931.
5915                       </p>
5916                     </td>
5917 </tr>
5918 <tr>
5919 <td>
5920                       <p>
5921                         KX
5922                       </p>
5923                     </td>
5924 <td>
5925                       <p>
5926                         Identifies a key exchanger for this
5927                         DNS name.  Described in RFC 2230.
5928                       </p>
5929                     </td>
5930 </tr>
5931 <tr>
5932 <td>
5933                       <p>
5934                         LOC
5935                       </p>
5936                     </td>
5937 <td>
5938                       <p>
5939                         For storing GPS info.  Described in RFC 1876.
5940                         Experimental.
5941                       </p>
5942                     </td>
5943 </tr>
5944 <tr>
5945 <td>
5946                       <p>
5947                         MX
5948                       </p>
5949                     </td>
5950 <td>
5951                       <p>
5952                         Identifies a mail exchange for the domain with
5953                         a 16-bit preference value (lower is better)
5954                         followed by the host name of the mail exchange.
5955                         Described in RFC 974, RFC 1035.
5956                       </p>
5957                     </td>
5958 </tr>
5959 <tr>
5960 <td>
5961                       <p>
5962                         NAPTR
5963                       </p>
5964                     </td>
5965 <td>
5966                       <p>
5967                         Name authority pointer.  Described in RFC 2915.
5968                       </p>
5969                     </td>
5970 </tr>
5971 <tr>
5972 <td>
5973                       <p>
5974                         NSAP
5975                       </p>
5976                     </td>
5977 <td>
5978                       <p>
5979                         A network service access point.
5980                         Described in RFC 1706.
5981                       </p>
5982                     </td>
5983 </tr>
5984 <tr>
5985 <td>
5986                       <p>
5987                         NS
5988                       </p>
5989                     </td>
5990 <td>
5991                       <p>
5992                         The authoritative name server for the
5993                         domain.  Described in RFC 1035.
5994                       </p>
5995                     </td>
5996 </tr>
5997 <tr>
5998 <td>
5999                       <p>
6000                         NSEC
6001                       </p>
6002                     </td>
6003 <td>
6004                       <p>
6005                         Used in DNSSECbis to securely indicate that
6006                         RRs with an owner name in a certain name interval do
6007                         not exist in
6008                         a zone and indicate what RR types are present for an
6009                         existing name.
6010                         Described in RFC 4034.
6011                       </p>
6012                     </td>
6013 </tr>
6014 <tr>
6015 <td>
6016                       <p>
6017                         NXT
6018                       </p>
6019                     </td>
6020 <td>
6021                       <p>
6022                         Used in DNSSEC to securely indicate that
6023                         RRs with an owner name in a certain name interval do
6024                         not exist in
6025                         a zone and indicate what RR types are present for an
6026                         existing name.
6027                         Used in original DNSSEC; replaced by NSEC in
6028                         DNSSECbis.
6029                         Described in RFC 2535.
6030                       </p>
6031                     </td>
6032 </tr>
6033 <tr>
6034 <td>
6035                       <p>
6036                         PTR
6037                       </p>
6038                     </td>
6039 <td>
6040                       <p>
6041                         A pointer to another part of the domain
6042                         name space.  Described in RFC 1035.
6043                       </p>
6044                     </td>
6045 </tr>
6046 <tr>
6047 <td>
6048                       <p>
6049                         PX
6050                       </p>
6051                     </td>
6052 <td>
6053                       <p>
6054                         Provides mappings between RFC 822 and X.400
6055                         addresses.  Described in RFC 2163.
6056                       </p>
6057                     </td>
6058 </tr>
6059 <tr>
6060 <td>
6061                       <p>
6062                         RP
6063                       </p>
6064                     </td>
6065 <td>
6066                       <p>
6067                         Information on persons responsible
6068                         for the domain.  Experimental.  Described in RFC 1183.
6069                       </p>
6070                     </td>
6071 </tr>
6072 <tr>
6073 <td>
6074                       <p>
6075                         RRSIG
6076                       </p>
6077                     </td>
6078 <td>
6079                       <p>
6080                         Contains DNSSECbis signature data.  Described
6081                         in RFC 4034.
6082                       </p>
6083                     </td>
6084 </tr>
6085 <tr>
6086 <td>
6087                       <p>
6088                         RT
6089                       </p>
6090                     </td>
6091 <td>
6092                       <p>
6093                         Route-through binding for hosts that
6094                         do not have their own direct wide area network
6095                         addresses.
6096                         Experimental.  Described in RFC 1183.
6097                       </p>
6098                     </td>
6099 </tr>
6100 <tr>
6101 <td>
6102                       <p>
6103                         SIG
6104                       </p>
6105                     </td>
6106 <td>
6107                       <p>
6108                         Contains DNSSEC signature data.  Used in
6109                         original DNSSEC; replaced by RRSIG in
6110                         DNSSECbis, but still used for SIG(0).
6111                         Described in RFCs 2535 and 2931.
6112                       </p>
6113                     </td>
6114 </tr>
6115 <tr>
6116 <td>
6117                       <p>
6118                         SOA
6119                       </p>
6120                     </td>
6121 <td>
6122                       <p>
6123                         Identifies the start of a zone of authority.
6124                         Described in RFC 1035.
6125                       </p>
6126                     </td>
6127 </tr>
6128 <tr>
6129 <td>
6130                       <p>
6131                         SRV
6132                       </p>
6133                     </td>
6134 <td>
6135                       <p>
6136                         Information about well known network
6137                         services (replaces WKS).  Described in RFC 2782.
6138                       </p>
6139                     </td>
6140 </tr>
6141 <tr>
6142 <td>
6143                       <p>
6144                         TXT
6145                       </p>
6146                     </td>
6147 <td>
6148                       <p>
6149                         Text records.  Described in RFC 1035.
6150                       </p>
6151                     </td>
6152 </tr>
6153 <tr>
6154 <td>
6155                       <p>
6156                         WKS
6157                       </p>
6158                     </td>
6159 <td>
6160                       <p>
6161                         Information about which well known
6162                         network services, such as SMTP, that a domain
6163                         supports. Historical.
6164                       </p>
6165                     </td>
6166 </tr>
6167 <tr>
6168 <td>
6169                       <p>
6170                         X25
6171                       </p>
6172                     </td>
6173 <td>
6174                       <p>
6175                         Representation of X.25 network addresses.
6176                         Experimental.  Described in RFC 1183.
6177                       </p>
6178                     </td>
6179 </tr>
6180 </tbody>
6181 </table></div>
6182 <p>
6183               The following <span class="emphasis"><em>classes</em></span> of resource records
6184               are currently valid in the DNS:
6185             </p>
6186 <div class="informaltable"><table border="1">
6187 <colgroup>
6188 <col>
6189 <col>
6190 </colgroup>
6191 <tbody>
6192 <tr>
6193 <td>
6194                       <p>
6195                         IN
6196                       </p>
6197                     </td>
6198 <td>
6199                       <p>
6200                         The Internet.
6201                       </p>
6202                     </td>
6203 </tr>
6204 <tr>
6205 <td>
6206                       <p>
6207                         CH
6208                       </p>
6209                     </td>
6210 <td>
6211                       <p>
6212                         Chaosnet, a LAN protocol created at MIT in the
6213                         mid-1970s.
6214                         Rarely used for its historical purpose, but reused for
6215                         BIND's
6216                         built-in server information zones, e.g.,
6217                         <code class="literal">version.bind</code>.
6218                       </p>
6219                     </td>
6220 </tr>
6221 <tr>
6222 <td>
6223                       <p>
6224                         HS
6225                       </p>
6226                     </td>
6227 <td>
6228                       <p>
6229                         Hesiod, an information service
6230                         developed by MIT's Project Athena. It is used to share
6231                         information
6232                         about various systems databases, such as users,
6233                         groups, printers
6234                         and so on.
6235                       </p>
6236                     </td>
6237 </tr>
6238 </tbody>
6239 </table></div>
6240 <p>
6241               The owner name is often implicit, rather than forming an
6242               integral
6243               part of the RR.  For example, many name servers internally form
6244               tree
6245               or hash structures for the name space, and chain RRs off nodes.
6246               The remaining RR parts are the fixed header (type, class, TTL)
6247               which is consistent for all RRs, and a variable part (RDATA)
6248               that
6249               fits the needs of the resource being described.
6250             </p>
6251 <p>
6252               The meaning of the TTL field is a time limit on how long an
6253               RR can be kept in a cache.  This limit does not apply to
6254               authoritative
6255               data in zones; it is also timed out, but by the refreshing
6256               policies
6257               for the zone.  The TTL is assigned by the administrator for the
6258               zone where the data originates.  While short TTLs can be used to
6259               minimize caching, and a zero TTL prohibits caching, the
6260               realities
6261               of Internet performance suggest that these times should be on
6262               the
6263               order of days for the typical host.  If a change can be
6264               anticipated,
6265               the TTL can be reduced prior to the change to minimize
6266               inconsistency
6267               during the change, and then increased back to its former value
6268               following
6269               the change.
6270             </p>
6271 <p>
6272               The data in the RDATA section of RRs is carried as a combination
6273               of binary strings and domain names.  The domain names are
6274               frequently
6275               used as "pointers" to other data in the DNS.
6276             </p>
6277 </div>
6278 <div class="sect3" lang="en">
6279 <div class="titlepage"><div><div><h4 class="title">
6280 <a name="id2590513"></a>Textual expression of RRs</h4></div></div></div>
6281 <p>
6282               RRs are represented in binary form in the packets of the DNS
6283               protocol, and are usually represented in highly encoded form
6284               when
6285               stored in a name server or resolver.  In the examples provided
6286               in
6287               RFC 1034, a style similar to that used in master files was
6288               employed
6289               in order to show the contents of RRs.  In this format, most RRs
6290               are shown on a single line, although continuation lines are
6291               possible
6292               using parentheses.
6293             </p>
6294 <p>
6295               The start of the line gives the owner of the RR.  If a line
6296               begins with a blank, then the owner is assumed to be the same as
6297               that of the previous RR.  Blank lines are often included for
6298               readability.
6299             </p>
6300 <p>
6301               Following the owner, we list the TTL, type, and class of the
6302               RR.  Class and type use the mnemonics defined above, and TTL is
6303               an integer before the type field.  In order to avoid ambiguity
6304               in
6305               parsing, type and class mnemonics are disjoint, TTLs are
6306               integers,
6307               and the type mnemonic is always last. The IN class and TTL
6308               values
6309               are often omitted from examples in the interests of clarity.
6310             </p>
6311 <p>
6312               The resource data or RDATA section of the RR are given using
6313               knowledge of the typical representation for the data.
6314             </p>
6315 <p>
6316               For example, we might show the RRs carried in a message as:
6317             </p>
6318 <div class="informaltable"><table border="1">
6319 <colgroup>
6320 <col>
6321 <col>
6322 <col>
6323 </colgroup>
6324 <tbody>
6325 <tr>
6326 <td>
6327                       <p>
6328                         <code class="literal">ISI.EDU.</code>
6329                       </p>
6330                     </td>
6331 <td>
6332                       <p>
6333                         <code class="literal">MX</code>
6334                       </p>
6335                     </td>
6336 <td>
6337                       <p>
6338                         <code class="literal">10 VENERA.ISI.EDU.</code>
6339                       </p>
6340                     </td>
6341 </tr>
6342 <tr>
6343 <td>
6344                       <p></p>
6345                     </td>
6346 <td>
6347                       <p>
6348                         <code class="literal">MX</code>
6349                       </p>
6350                     </td>
6351 <td>
6352                       <p>
6353                         <code class="literal">10 VAXA.ISI.EDU</code>
6354                       </p>
6355                     </td>
6356 </tr>
6357 <tr>
6358 <td>
6359                       <p>
6360                         <code class="literal">VENERA.ISI.EDU</code>
6361                       </p>
6362                     </td>
6363 <td>
6364                       <p>
6365                         <code class="literal">A</code>
6366                       </p>
6367                     </td>
6368 <td>
6369                       <p>
6370                         <code class="literal">128.9.0.32</code>
6371                       </p>
6372                     </td>
6373 </tr>
6374 <tr>
6375 <td>
6376                       <p></p>
6377                     </td>
6378 <td>
6379                       <p>
6380                         <code class="literal">A</code>
6381                       </p>
6382                     </td>
6383 <td>
6384                       <p>
6385                         <code class="literal">10.1.0.52</code>
6386                       </p>
6387                     </td>
6388 </tr>
6389 <tr>
6390 <td>
6391                       <p>
6392                         <code class="literal">VAXA.ISI.EDU</code>
6393                       </p>
6394                     </td>
6395 <td>
6396                       <p>
6397                         <code class="literal">A</code>
6398                       </p>
6399                     </td>
6400 <td>
6401                       <p>
6402                         <code class="literal">10.2.0.27</code>
6403                       </p>
6404                     </td>
6405 </tr>
6406 <tr>
6407 <td>
6408                       <p></p>
6409                     </td>
6410 <td>
6411                       <p>
6412                         <code class="literal">A</code>
6413                       </p>
6414                     </td>
6415 <td>
6416                       <p>
6417                         <code class="literal">128.9.0.33</code>
6418                       </p>
6419                     </td>
6420 </tr>
6421 </tbody>
6422 </table></div>
6423 <p>
6424               The MX RRs have an RDATA section which consists of a 16-bit
6425               number followed by a domain name.  The address RRs use a
6426               standard
6427               IP address format to contain a 32-bit internet address.
6428             </p>
6429 <p>
6430               The above example shows six RRs, with two RRs at each of three
6431               domain names.
6432             </p>
6433 <p>
6434               Similarly we might see:
6435             </p>
6436 <div class="informaltable"><table border="1">
6437 <colgroup>
6438 <col>
6439 <col>
6440 <col>
6441 </colgroup>
6442 <tbody>
6443 <tr>
6444 <td>
6445                       <p>
6446                         <code class="literal">XX.LCS.MIT.EDU.</code>
6447                       </p>
6448                     </td>
6449 <td>
6450                       <p>
6451                         <code class="literal">IN A</code>
6452                       </p>
6453                     </td>
6454 <td>
6455                       <p>
6456                         <code class="literal">10.0.0.44</code>
6457                       </p>
6458                     </td>
6459 </tr>
6460 <tr>
6461 <td> </td>
6462 <td>
6463                       <p>
6464                         <code class="literal">CH A</code>
6465                       </p>
6466                     </td>
6467 <td>
6468                       <p>
6469                         <code class="literal">MIT.EDU. 2420</code>
6470                       </p>
6471                     </td>
6472 </tr>
6473 </tbody>
6474 </table></div>
6475 <p>
6476               This example shows two addresses for
6477               <code class="literal">XX.LCS.MIT.EDU</code>, each of a different class.
6478             </p>
6479 </div>
6480 </div>
6481 <div class="sect2" lang="en">
6482 <div class="titlepage"><div><div><h3 class="title">
6483 <a name="id2591101"></a>Discussion of MX Records</h3></div></div></div>
6484 <p>
6485             As described above, domain servers store information as a
6486             series of resource records, each of which contains a particular
6487             piece of information about a given domain name (which is usually,
6488             but not always, a host). The simplest way to think of a RR is as
6489             a typed pair of data, a domain name matched with a relevant datum,
6490             and stored with some additional type information to help systems
6491             determine when the RR is relevant.
6492           </p>
6493 <p>
6494             MX records are used to control delivery of email. The data
6495             specified in the record is a priority and a domain name. The
6496             priority
6497             controls the order in which email delivery is attempted, with the
6498             lowest number first. If two priorities are the same, a server is
6499             chosen randomly. If no servers at a given priority are responding,
6500             the mail transport agent will fall back to the next largest
6501             priority.
6502             Priority numbers do not have any absolute meaning &#8212; they are
6503             relevant
6504             only respective to other MX records for that domain name. The
6505             domain
6506             name given is the machine to which the mail will be delivered.
6507             It <span class="emphasis"><em>must</em></span> have an associated address record
6508             (A or AAAA) &#8212; CNAME is not sufficient.
6509           </p>
6510 <p>
6511             For a given domain, if there is both a CNAME record and an
6512             MX record, the MX record is in error, and will be ignored.
6513             Instead,
6514             the mail will be delivered to the server specified in the MX
6515             record
6516             pointed to by the CNAME.
6517           </p>
6518 <p>
6519             For example:
6520           </p>
6521 <div class="informaltable"><table border="1">
6522 <colgroup>
6523 <col>
6524 <col>
6525 <col>
6526 <col>
6527 <col>
6528 </colgroup>
6529 <tbody>
6530 <tr>
6531 <td>
6532                     <p>
6533                       <code class="literal">example.com.</code>
6534                     </p>
6535                   </td>
6536 <td>
6537                     <p>
6538                       <code class="literal">IN</code>
6539                     </p>
6540                   </td>
6541 <td>
6542                     <p>
6543                       <code class="literal">MX</code>
6544                     </p>
6545                   </td>
6546 <td>
6547                     <p>
6548                       <code class="literal">10</code>
6549                     </p>
6550                   </td>
6551 <td>
6552                     <p>
6553                       <code class="literal">mail.example.com.</code>
6554                     </p>
6555                   </td>
6556 </tr>
6557 <tr>
6558 <td>
6559                     <p></p>
6560                   </td>
6561 <td>
6562                     <p>
6563                       <code class="literal">IN</code>
6564                     </p>
6565                   </td>
6566 <td>
6567                     <p>
6568                       <code class="literal">MX</code>
6569                     </p>
6570                   </td>
6571 <td>
6572                     <p>
6573                       <code class="literal">10</code>
6574                     </p>
6575                   </td>
6576 <td>
6577                     <p>
6578                       <code class="literal">mail2.example.com.</code>
6579                     </p>
6580                   </td>
6581 </tr>
6582 <tr>
6583 <td>
6584                     <p></p>
6585                   </td>
6586 <td>
6587                     <p>
6588                       <code class="literal">IN</code>
6589                     </p>
6590                   </td>
6591 <td>
6592                     <p>
6593                       <code class="literal">MX</code>
6594                     </p>
6595                   </td>
6596 <td>
6597                     <p>
6598                       <code class="literal">20</code>
6599                     </p>
6600                   </td>
6601 <td>
6602                     <p>
6603                       <code class="literal">mail.backup.org.</code>
6604                     </p>
6605                   </td>
6606 </tr>
6607 <tr>
6608 <td>
6609                     <p>
6610                       <code class="literal">mail.example.com.</code>
6611                     </p>
6612                   </td>
6613 <td>
6614                     <p>
6615                       <code class="literal">IN</code>
6616                     </p>
6617                   </td>
6618 <td>
6619                     <p>
6620                       <code class="literal">A</code>
6621                     </p>
6622                   </td>
6623 <td>
6624                     <p>
6625                       <code class="literal">10.0.0.1</code>
6626                     </p>
6627                   </td>
6628 <td>
6629                     <p></p>
6630                   </td>
6631 </tr>
6632 <tr>
6633 <td>
6634                     <p>
6635                       <code class="literal">mail2.example.com.</code>
6636                     </p>
6637                   </td>
6638 <td>
6639                     <p>
6640                       <code class="literal">IN</code>
6641                     </p>
6642                   </td>
6643 <td>
6644                     <p>
6645                       <code class="literal">A</code>
6646                     </p>
6647                   </td>
6648 <td>
6649                     <p>
6650                       <code class="literal">10.0.0.2</code>
6651                     </p>
6652                   </td>
6653 <td>
6654                     <p></p>
6655                   </td>
6656 </tr>
6657 </tbody>
6658 </table></div>
6659 <p>
6660             Mail delivery will be attempted to <code class="literal">mail.example.com</code> and
6661             <code class="literal">mail2.example.com</code> (in
6662             any order), and if neither of those succeed, delivery to <code class="literal">mail.backup.org</code> will
6663             be attempted.
6664           </p>
6665 </div>
6666 <div class="sect2" lang="en">
6667 <div class="titlepage"><div><div><h3 class="title">
6668 <a name="Setting_TTLs"></a>Setting TTLs</h3></div></div></div>
6669 <p>
6670             The time-to-live of the RR field is a 32-bit integer represented
6671             in units of seconds, and is primarily used by resolvers when they
6672             cache RRs. The TTL describes how long a RR can be cached before it
6673             should be discarded. The following three types of TTL are
6674             currently
6675             used in a zone file.
6676           </p>
6677 <div class="informaltable"><table border="1">
6678 <colgroup>
6679 <col>
6680 <col>
6681 </colgroup>
6682 <tbody>
6683 <tr>
6684 <td>
6685                     <p>
6686                       SOA
6687                     </p>
6688                   </td>
6689 <td>
6690                     <p>
6691                       The last field in the SOA is the negative
6692                       caching TTL. This controls how long other servers will
6693                       cache no-such-domain
6694                       (NXDOMAIN) responses from you.
6695                     </p>
6696                     <p>
6697                       The maximum time for
6698                       negative caching is 3 hours (3h).
6699                     </p>
6700                   </td>
6701 </tr>
6702 <tr>
6703 <td>
6704                     <p>
6705                       $TTL
6706                     </p>
6707                   </td>
6708 <td>
6709                     <p>
6710                       The $TTL directive at the top of the
6711                       zone file (before the SOA) gives a default TTL for every
6712                       RR without
6713                       a specific TTL set.
6714                     </p>
6715                   </td>
6716 </tr>
6717 <tr>
6718 <td>
6719                     <p>
6720                       RR TTLs
6721                     </p>
6722                   </td>
6723 <td>
6724                     <p>
6725                       Each RR can have a TTL as the second
6726                       field in the RR, which will control how long other
6727                       servers can cache
6728                       the it.
6729                     </p>
6730                   </td>
6731 </tr>
6732 </tbody>
6733 </table></div>
6734 <p>
6735             All of these TTLs default to units of seconds, though units
6736             can be explicitly specified, for example, <code class="literal">1h30m</code>.
6737           </p>
6738 </div>
6739 <div class="sect2" lang="en">
6740 <div class="titlepage"><div><div><h3 class="title">
6741 <a name="id2591653"></a>Inverse Mapping in IPv4</h3></div></div></div>
6742 <p>
6743             Reverse name resolution (that is, translation from IP address
6744             to name) is achieved by means of the <span class="emphasis"><em>in-addr.arpa</em></span> domain
6745             and PTR records. Entries in the in-addr.arpa domain are made in
6746             least-to-most significant order, read left to right. This is the
6747             opposite order to the way IP addresses are usually written. Thus,
6748             a machine with an IP address of 10.1.2.3 would have a
6749             corresponding
6750             in-addr.arpa name of
6751             3.2.1.10.in-addr.arpa. This name should have a PTR resource record
6752             whose data field is the name of the machine or, optionally,
6753             multiple
6754             PTR records if the machine has more than one name. For example,
6755             in the [<span class="optional">example.com</span>] domain:
6756           </p>
6757 <div class="informaltable"><table border="1">
6758 <colgroup>
6759 <col>
6760 <col>
6761 </colgroup>
6762 <tbody>
6763 <tr>
6764 <td>
6765                     <p>
6766                       <code class="literal">$ORIGIN</code>
6767                     </p>
6768                   </td>
6769 <td>
6770                     <p>
6771                       <code class="literal">2.1.10.in-addr.arpa</code>
6772                     </p>
6773                   </td>
6774 </tr>
6775 <tr>
6776 <td>
6777                     <p>
6778                       <code class="literal">3</code>
6779                     </p>
6780                   </td>
6781 <td>
6782                     <p>
6783                       <code class="literal">IN PTR foo.example.com.</code>
6784                     </p>
6785                   </td>
6786 </tr>
6787 </tbody>
6788 </table></div>
6789 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
6790 <h3 class="title">Note</h3>
6791 <p>
6792               The <span><strong class="command">$ORIGIN</strong></span> lines in the examples
6793               are for providing context to the examples only &#8212; they do not
6794               necessarily
6795               appear in the actual usage. They are only used here to indicate
6796               that the example is relative to the listed origin.
6797             </p>
6798 </div>
6799 </div>
6800 <div class="sect2" lang="en">
6801 <div class="titlepage"><div><div><h3 class="title">
6802 <a name="id2591848"></a>Other Zone File Directives</h3></div></div></div>
6803 <p>
6804             The Master File Format was initially defined in RFC 1035 and
6805             has subsequently been extended. While the Master File Format
6806             itself
6807             is class independent all records in a Master File must be of the
6808             same
6809             class.
6810           </p>
6811 <p>
6812             Master File Directives include <span><strong class="command">$ORIGIN</strong></span>, <span><strong class="command">$INCLUDE</strong></span>,
6813             and <span><strong class="command">$TTL.</strong></span>
6814           </p>
6815 <div class="sect3" lang="en">
6816 <div class="titlepage"><div><div><h4 class="title">
6817 <a name="id2591870"></a>The <span><strong class="command">$ORIGIN</strong></span> Directive</h4></div></div></div>
6818 <p>
6819               Syntax: <span><strong class="command">$ORIGIN</strong></span>
6820               <em class="replaceable"><code>domain-name</code></em>
6821               [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
6822             </p>
6823 <p><span><strong class="command">$ORIGIN</strong></span>
6824               sets the domain name that will be appended to any
6825               unqualified records. When a zone is first read in there
6826               is an implicit <span><strong class="command">$ORIGIN</strong></span>
6827               &lt;<code class="varname">zone-name</code>&gt;<span><strong class="command">.</strong></span>
6828               The current <span><strong class="command">$ORIGIN</strong></span> is appended to
6829               the domain specified in the <span><strong class="command">$ORIGIN</strong></span>
6830               argument if it is not absolute.
6831             </p>
6832 <pre class="programlisting">
6833 $ORIGIN example.com.
6834 WWW     CNAME   MAIN-SERVER
6835 </pre>
6836 <p>
6837               is equivalent to
6838             </p>
6839 <pre class="programlisting">
6840 WWW.EXAMPLE.COM. CNAME MAIN-SERVER.EXAMPLE.COM.
6841 </pre>
6842 </div>
6843 <div class="sect3" lang="en">
6844 <div class="titlepage"><div><div><h4 class="title">
6845 <a name="id2592000"></a>The <span><strong class="command">$INCLUDE</strong></span> Directive</h4></div></div></div>
6846 <p>
6847               Syntax: <span><strong class="command">$INCLUDE</strong></span>
6848               <em class="replaceable"><code>filename</code></em>
6849               [<span class="optional">
6850 <em class="replaceable"><code>origin</code></em> </span>]
6851               [<span class="optional"> <em class="replaceable"><code>comment</code></em> </span>]
6852             </p>
6853 <p>
6854               Read and process the file <code class="filename">filename</code> as
6855               if it were included into the file at this point.  If <span><strong class="command">origin</strong></span> is
6856               specified the file is processed with <span><strong class="command">$ORIGIN</strong></span> set
6857               to that value, otherwise the current <span><strong class="command">$ORIGIN</strong></span> is
6858               used.
6859             </p>
6860 <p>
6861               The origin and the current domain name
6862               revert to the values they had prior to the <span><strong class="command">$INCLUDE</strong></span> once
6863               the file has been read.
6864             </p>
6865 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
6866 <h3 class="title">Note</h3>
6867 <p>
6868                 RFC 1035 specifies that the current origin should be restored
6869                 after
6870                 an <span><strong class="command">$INCLUDE</strong></span>, but it is silent
6871                 on whether the current
6872                 domain name should also be restored.  BIND 9 restores both of
6873                 them.
6874                 This could be construed as a deviation from RFC 1035, a
6875                 feature, or both.
6876               </p>
6877 </div>
6878 </div>
6879 <div class="sect3" lang="en">
6880 <div class="titlepage"><div><div><h4 class="title">
6881 <a name="id2592069"></a>The <span><strong class="command">$TTL</strong></span> Directive</h4></div></div></div>
6882 <p>
6883               Syntax: <span><strong class="command">$TTL</strong></span>
6884               <em class="replaceable"><code>default-ttl</code></em>
6885               [<span class="optional">
6886 <em class="replaceable"><code>comment</code></em> </span>]
6887             </p>
6888 <p>
6889               Set the default Time To Live (TTL) for subsequent records
6890               with undefined TTLs. Valid TTLs are of the range 0-2147483647
6891               seconds.
6892             </p>
6893 <p><span><strong class="command">$TTL</strong></span>
6894                is defined in RFC 2308.
6895             </p>
6896 </div>
6897 </div>
6898 <div class="sect2" lang="en">
6899 <div class="titlepage"><div><div><h3 class="title">
6900 <a name="id2592173"></a><acronym class="acronym">BIND</acronym> Master File Extension: the  <span><strong class="command">$GENERATE</strong></span> Directive</h3></div></div></div>
6901 <p>
6902             Syntax: <span><strong class="command">$GENERATE</strong></span>
6903             <em class="replaceable"><code>range</code></em>
6904             <em class="replaceable"><code>lhs</code></em>
6905             [<span class="optional"><em class="replaceable"><code>ttl</code></em></span>]
6906             [<span class="optional"><em class="replaceable"><code>class</code></em></span>]
6907             <em class="replaceable"><code>type</code></em>
6908             <em class="replaceable"><code>rhs</code></em>
6909             [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
6910           </p>
6911 <p><span><strong class="command">$GENERATE</strong></span>
6912             is used to create a series of resource records that only
6913             differ from each other by an
6914             iterator. <span><strong class="command">$GENERATE</strong></span> can be used to
6915             easily generate the sets of records required to support
6916             sub /24 reverse delegations described in RFC 2317:
6917             Classless IN-ADDR.ARPA delegation.
6918           </p>
6919 <pre class="programlisting">$ORIGIN 0.0.192.IN-ADDR.ARPA.
6920 $GENERATE 1-2 0 NS SERVER$.EXAMPLE.
6921 $GENERATE 1-127 $ CNAME $.0</pre>
6922 <p>
6923             is equivalent to
6924           </p>
6925 <pre class="programlisting">0.0.0.192.IN-ADDR.ARPA NS SERVER1.EXAMPLE.
6926 0.0.0.192.IN-ADDR.ARPA. NS SERVER2.EXAMPLE.
6927 1.0.0.192.IN-ADDR.ARPA. CNAME 1.0.0.0.192.IN-ADDR.ARPA.
6928 2.0.0.192.IN-ADDR.ARPA. CNAME 2.0.0.0.192.IN-ADDR.ARPA.
6929 ...
6930 127.0.0.192.IN-ADDR.ARPA. CNAME 127.0.0.0.192.IN-ADDR.ARPA.
6931 </pre>
6932 <div class="informaltable"><table border="1">
6933 <colgroup>
6934 <col>
6935 <col>
6936 </colgroup>
6937 <tbody>
6938 <tr>
6939 <td>
6940                     <p><span><strong class="command">range</strong></span></p>
6941                   </td>
6942 <td>
6943                     <p>
6944                       This can be one of two forms: start-stop
6945                       or start-stop/step. If the first form is used, then step
6946                       is set to
6947                       1. All of start, stop and step must be positive.
6948                     </p>
6949                   </td>
6950 </tr>
6951 <tr>
6952 <td>
6953                     <p><span><strong class="command">lhs</strong></span></p>
6954                   </td>
6955 <td>
6956                     <p>This
6957                       describes the owner name of the resource records
6958                       to be created.  Any single <span><strong class="command">$</strong></span>
6959                       (dollar sign)
6960                       symbols within the <span><strong class="command">lhs</strong></span> side
6961                       are replaced by the iterator value.
6962
6963                       To get a $ in the output, you need to escape the
6964                       <span><strong class="command">$</strong></span> using a backslash
6965                       <span><strong class="command">\</strong></span>,
6966                       e.g. <span><strong class="command">\$</strong></span>. The
6967                       <span><strong class="command">$</strong></span> may optionally be followed
6968                       by modifiers which change the offset from the
6969                       iterator, field width and base.
6970
6971                       Modifiers are introduced by a
6972                       <span><strong class="command">{</strong></span> (left brace) immediately following the
6973                       <span><strong class="command">$</strong></span> as
6974                       <span><strong class="command">${offset[,width[,base]]}</strong></span>.
6975                       For example, <span><strong class="command">${-20,3,d}</strong></span>
6976                       subtracts 20 from the current value, prints the
6977                       result as a decimal in a zero-padded field of
6978                       width 3.
6979
6980                       Available output forms are decimal
6981                       (<span><strong class="command">d</strong></span>), octal
6982                       (<span><strong class="command">o</strong></span>) and hexadecimal
6983                       (<span><strong class="command">x</strong></span> or <span><strong class="command">X</strong></span>
6984                       for uppercase).  The default modifier is
6985                       <span><strong class="command">${0,0,d}</strong></span>.  If the
6986                       <span><strong class="command">lhs</strong></span> is not absolute, the
6987                       current <span><strong class="command">$ORIGIN</strong></span> is appended
6988                       to the name.
6989                     </p>
6990                     <p>
6991                       For compatibility with earlier versions, <span><strong class="command">$$</strong></span> is still
6992                       recognized as indicating a literal $ in the output.
6993                     </p>
6994                   </td>
6995 </tr>
6996 <tr>
6997 <td>
6998                     <p><span><strong class="command">ttl</strong></span></p>
6999                   </td>
7000 <td>
7001                     <p>
7002                       Specifies the time-to-live of the generated records. If
7003                       not specified this will be inherited using the
7004                       normal ttl inheritance rules.
7005                     </p>
7006                     <p><span><strong class="command">class</strong></span>
7007                       and <span><strong class="command">ttl</strong></span> can be
7008                       entered in either order.
7009                     </p>
7010                   </td>
7011 </tr>
7012 <tr>
7013 <td>
7014                     <p><span><strong class="command">class</strong></span></p>
7015                   </td>
7016 <td>
7017                     <p>
7018                       Specifies the class of the generated records.
7019                       This must match the zone class if it is
7020                       specified.
7021                     </p>
7022                     <p><span><strong class="command">class</strong></span>
7023                       and <span><strong class="command">ttl</strong></span> can be
7024                       entered in either order.
7025                     </p>
7026                   </td>
7027 </tr>
7028 <tr>
7029 <td>
7030                     <p><span><strong class="command">type</strong></span></p>
7031                   </td>
7032 <td>
7033                     <p>
7034                       At present the only supported types are
7035                       PTR, CNAME, DNAME, A, AAAA and NS.
7036                     </p>
7037                   </td>
7038 </tr>
7039 <tr>
7040 <td>
7041                     <p><span><strong class="command">rhs</strong></span></p>
7042                   </td>
7043 <td>
7044                     <p>
7045                       <span><strong class="command">rhs</strong></span> is a domain name. It is processed
7046                       similarly to lhs.
7047                     </p>
7048                   </td>
7049 </tr>
7050 </tbody>
7051 </table></div>
7052 <p>
7053             The <span><strong class="command">$GENERATE</strong></span> directive is a <acronym class="acronym">BIND</acronym> extension
7054             and not part of the standard zone file format.
7055           </p>
7056 <p>
7057             BIND 8 does not support the optional TTL and CLASS fields.
7058           </p>
7059 </div>
7060 <div class="sect2" lang="en">
7061 <div class="titlepage"><div><div><h3 class="title">
7062 <a name="zonefile_format"></a>Additional File Formats</h3></div></div></div>
7063 <p>
7064             In addition to the standard textual format, BIND 9
7065             supports the ability to read or dump to zone files in
7066             other formats.  The <code class="constant">raw</code> format is
7067             currently available as an additional format.  It is a
7068             binary format representing BIND 9's internal data
7069             structure directly, thereby remarkably improving the
7070             loading time.
7071           </p>
7072 <p>
7073             For a primary server, a zone file in the
7074             <code class="constant">raw</code> format is expected to be
7075             generated from a textual zone file by the
7076             <span><strong class="command">named-compilezone</strong></span> command.  For a
7077             secondary server or for a dynamic zone, it is automatically
7078             generated (if this format is specified by the
7079             <span><strong class="command">masterfile-format</strong></span> option) when
7080             <span><strong class="command">named</strong></span> dumps the zone contents after
7081             zone transfer or when applying prior updates.
7082           </p>
7083 <p>
7084             If a zone file in a binary format needs manual modification,
7085             it first must be converted to a textual form by the
7086             <span><strong class="command">named-compilezone</strong></span> command.  All
7087             necessary modification should go to the text file, which
7088             should then be converted to the binary form by the
7089             <span><strong class="command">named-compilezone</strong></span> command again.
7090           </p>
7091 <p>
7092              Although the <code class="constant">raw</code> format uses the
7093              network byte order and avoids architecture-dependent
7094              data alignment so that it is as much portable as
7095              possible, it is primarily expected to be used inside
7096              the same single system.  In order to export a zone
7097              file in the <code class="constant">raw</code> format or make a
7098              portable backup of the file, it is recommended to
7099              convert the file to the standard textual representation.
7100           </p>
7101 </div>
7102 </div>
7103 </div>
7104 <div class="navfooter">
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7115 <td width="40%" align="left" valign="top">Chapter 5. The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver </td>
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