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  21 <title>Chapter 6. BIND 9 Configuration Reference</title>
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  31 <tr><th colspan="3" align="center">Chapter 6. <acronym class="acronym">BIND</acronym> 9 Configuration Reference</th></tr>
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  42 <div class="chapter" lang="en">
  43 <div class="titlepage"><div><div><h2 class="title">
  44 <a name="Bv9ARM.ch06"></a>Chapter 6. <acronym class="acronym">BIND</acronym> 9 Configuration Reference</h2></div></div></div>
  45 <div class="toc">
  46 <p><b>Table of Contents</b></p>
  47 <dl>
  48 <dt><span class="sect1"><a href="Bv9ARM.ch06.html#configuration_file_elements">Configuration File Elements</a></span></dt>
  49 <dd><dl>
  50 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#address_match_lists">Address Match Lists</a></span></dt>
  51 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2573716">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#id2574346"><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#id2574536"><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#id2574965"><span><strong class="command">include</strong></span> Statement Grammar</a></span></dt>
  62 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574982"><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#id2575005"><span><strong class="command">key</strong></span> Statement Grammar</a></span></dt>
  65 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575029"><span><strong class="command">key</strong></span> Statement Definition and Usage</a></span></dt>
  66 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575120"><span><strong class="command">logging</strong></span> Statement Grammar</a></span></dt>
  67 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575245"><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#id2577306"><span><strong class="command">lwres</strong></span> Statement Grammar</a></span></dt>
  70 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577448"><span><strong class="command">lwres</strong></span> Statement Definition and Usage</a></span></dt>
  71 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577512"><span><strong class="command">masters</strong></span> Statement Grammar</a></span></dt>
  72 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577556"><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#id2577571"><span><strong class="command">options</strong></span> Statement Grammar</a></span></dt>
  75 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#options"><span><strong class="command">options</strong></span> Statement Definition and
  76           Usage</a></span></dt>
  77 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#server_statement_grammar"><span><strong class="command">server</strong></span> Statement Grammar</a></span></dt>
  78 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#server_statement_definition_and_usage"><span><strong class="command">server</strong></span> Statement Definition and
  79             Usage</a></span></dt>
  80 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#statschannels"><span><strong class="command">statistics-channels</strong></span> Statement Grammar</a></span></dt>
  81 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2586902"><span><strong class="command">statistics-channels</strong></span> Statement Definition and
  82             Usage</a></span></dt>
  83 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2586988"><span><strong class="command">trusted-keys</strong></span> Statement Grammar</a></span></dt>
  84 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2587040"><span><strong class="command">trusted-keys</strong></span> Statement Definition
  85             and Usage</a></span></dt>
  86 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#view_statement_grammar"><span><strong class="command">view</strong></span> Statement Grammar</a></span></dt>
  87 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2587122"><span><strong class="command">view</strong></span> Statement Definition and Usage</a></span></dt>
  88 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#zone_statement_grammar"><span><strong class="command">zone</strong></span>
  89             Statement Grammar</a></span></dt>
  90 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2588659"><span><strong class="command">zone</strong></span> Statement Definition and Usage</a></span></dt>
  91 </dl></dd>
  92 <dt><span class="sect1"><a href="Bv9ARM.ch06.html#id2591138">Zone File</a></span></dt>
  93 <dd><dl>
  94 <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>
  95 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2593300">Discussion of MX Records</a></span></dt>
  96 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#Setting_TTLs">Setting TTLs</a></span></dt>
  97 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2593915">Inverse Mapping in IPv4</a></span></dt>
  98 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2594042">Other Zone File Directives</a></span></dt>
  99 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2594368"><acronym class="acronym">BIND</acronym> Master File Extension: the  <span><strong class="command">$GENERATE</strong></span> Directive</a></span></dt>
 100 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#zonefile_format">Additional File Formats</a></span></dt>
 101 </dl></dd>
 102 <dt><span class="sect1"><a href="Bv9ARM.ch06.html#statistics">BIND9 Statistics</a></span></dt>
 103 <dd><dl><dt><span class="sect2"><a href="Bv9ARM.ch06.html#statistics_counters">Statistics Counters</a></span></dt></dl></dd>
 104 </dl>
 105 </div>
 106 <p>
 107       <acronym class="acronym">BIND</acronym> 9 configuration is broadly similar
 108       to <acronym class="acronym">BIND</acronym> 8; however, there are a few new
 109       areas
 110       of configuration, such as views. <acronym class="acronym">BIND</acronym>
 111       8 configuration files should work with few alterations in <acronym class="acronym">BIND</acronym>
 112       9, although more complex configurations should be reviewed to check
 113       if they can be more efficiently implemented using the new features
 114       found in <acronym class="acronym">BIND</acronym> 9.
 115     </p>
 116 <p>
 117       <acronym class="acronym">BIND</acronym> 4 configuration files can be
 118       converted to the new format
 119       using the shell script
 120       <code class="filename">contrib/named-bootconf/named-bootconf.sh</code>.
 121     </p>
 122 <div class="sect1" lang="en">
 123 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
 124 <a name="configuration_file_elements"></a>Configuration File Elements</h2></div></div></div>
 125 <p>
 126         Following is a list of elements used throughout the <acronym class="acronym">BIND</acronym> configuration
 127         file documentation:
 128       </p>
 129 <div class="informaltable"><table border="1">
 130 <colgroup>
 131 <col>
 132 <col>
 133 </colgroup>
 134 <tbody>
 135 <tr>
 136 <td>
 137                 <p>
 138                   <code class="varname">acl_name</code>
 139                 </p>
 140               </td>
 141 <td>
 142                 <p>
 143                   The name of an <code class="varname">address_match_list</code> as
 144                   defined by the <span><strong class="command">acl</strong></span> statement.
 145                 </p>
 146               </td>
 147 </tr>
 148 <tr>
 149 <td>
 150                 <p>
 151                   <code class="varname">address_match_list</code>
 152                 </p>
 153               </td>
 154 <td>
 155                 <p>
 156                   A list of one or more
 157                   <code class="varname">ip_addr</code>,
 158                   <code class="varname">ip_prefix</code>, <code class="varname">key_id</code>,
 159                   or <code class="varname">acl_name</code> elements, see
 160                   <a href="Bv9ARM.ch06.html#address_match_lists" title="Address Match Lists">the section called &#8220;Address Match Lists&#8221;</a>.
 161                 </p>
 162               </td>
 163 </tr>
 164 <tr>
 165 <td>
 166                 <p>
 167                   <code class="varname">masters_list</code>
 168                 </p>
 169               </td>
 170 <td>
 171                 <p>
 172                   A named list of one or more <code class="varname">ip_addr</code>
 173                   with optional <code class="varname">key_id</code> and/or
 174                   <code class="varname">ip_port</code>.
 175                   A <code class="varname">masters_list</code> may include other
 176                   <code class="varname">masters_lists</code>.
 177                 </p>
 178               </td>
 179 </tr>
 180 <tr>
 181 <td>
 182                 <p>
 183                   <code class="varname">domain_name</code>
 184                 </p>
 185               </td>
 186 <td>
 187                 <p>
 188                   A quoted string which will be used as
 189                   a DNS name, for example "<code class="literal">my.test.domain</code>".
 190                 </p>
 191               </td>
 192 </tr>
 193 <tr>
 194 <td>
 195                 <p>
 196                   <code class="varname">dotted_decimal</code>
 197                 </p>
 198               </td>
 199 <td>
 200                 <p>
 201                   One to four integers valued 0 through
 202                   255 separated by dots (`.'), such as <span><strong class="command">123</strong></span>,
 203                   <span><strong class="command">45.67</strong></span> or <span><strong class="command">89.123.45.67</strong></span>.
 204                 </p>
 205               </td>
 206 </tr>
 207 <tr>
 208 <td>
 209                 <p>
 210                   <code class="varname">ip4_addr</code>
 211                 </p>
 212               </td>
 213 <td>
 214                 <p>
 215                   An IPv4 address with exactly four elements
 216                   in <code class="varname">dotted_decimal</code> notation.
 217                 </p>
 218               </td>
 219 </tr>
 220 <tr>
 221 <td>
 222                 <p>
 223                   <code class="varname">ip6_addr</code>
 224                 </p>
 225               </td>
 226 <td>
 227                 <p>
 228                   An IPv6 address, such as <span><strong class="command">2001:db8::1234</strong></span>.
 229                   IPv6 scoped addresses that have ambiguity on their
 230                   scope zones must be disambiguated by an appropriate
 231                   zone ID with the percent character (`%') as
 232                   delimiter.  It is strongly recommended to use
 233                   string zone names rather than numeric identifiers,
 234                   in order to be robust against system configuration
 235                   changes.  However, since there is no standard
 236                   mapping for such names and identifier values,
 237                   currently only interface names as link identifiers
 238                   are supported, assuming one-to-one mapping between
 239                   interfaces and links.  For example, a link-local
 240                   address <span><strong class="command">fe80::1</strong></span> on the link
 241                   attached to the interface <span><strong class="command">ne0</strong></span>
 242                   can be specified as <span><strong class="command">fe80::1%ne0</strong></span>.
 243                   Note that on most systems link-local addresses
 244                   always have the ambiguity, and need to be
 245                   disambiguated.
 246                 </p>
 247               </td>
 248 </tr>
 249 <tr>
 250 <td>
 251                 <p>
 252                   <code class="varname">ip_addr</code>
 253                 </p>
 254               </td>
 255 <td>
 256                 <p>
 257                   An <code class="varname">ip4_addr</code> or <code class="varname">ip6_addr</code>.
 258                 </p>
 259               </td>
 260 </tr>
 261 <tr>
 262 <td>
 263                 <p>
 264                   <code class="varname">ip_port</code>
 265                 </p>
 266               </td>
 267 <td>
 268                 <p>
 269                   An IP port <code class="varname">number</code>.
 270                   The <code class="varname">number</code> is limited to 0
 271                   through 65535, with values
 272                   below 1024 typically restricted to use by processes running
 273                   as root.
 274                   In some cases, an asterisk (`*') character can be used as a
 275                   placeholder to
 276                   select a random high-numbered port.
 277                 </p>
 278               </td>
 279 </tr>
 280 <tr>
 281 <td>
 282                 <p>
 283                   <code class="varname">ip_prefix</code>
 284                 </p>
 285               </td>
 286 <td>
 287                 <p>
 288                   An IP network specified as an <code class="varname">ip_addr</code>,
 289                   followed by a slash (`/') and then the number of bits in the
 290                   netmask.
 291                   Trailing zeros in a <code class="varname">ip_addr</code>
 292                   may omitted.
 293                   For example, <span><strong class="command">127/8</strong></span> is the
 294                   network <span><strong class="command">127.0.0.0</strong></span> with
 295                   netmask <span><strong class="command">255.0.0.0</strong></span> and <span><strong class="command">1.2.3.0/28</strong></span> is
 296                   network <span><strong class="command">1.2.3.0</strong></span> with netmask <span><strong class="command">255.255.255.240</strong></span>.
 297                 </p>
 298                 <p>
 299                   When specifying a prefix involving a IPv6 scoped address
 300                   the scope may be omitted.  In that case the prefix will
 301                   match packets from any scope.
 302                 </p>
 303               </td>
 304 </tr>
 305 <tr>
 306 <td>
 307                 <p>
 308                   <code class="varname">key_id</code>
 309                 </p>
 310               </td>
 311 <td>
 312                 <p>
 313                   A <code class="varname">domain_name</code> representing
 314                   the name of a shared key, to be used for transaction
 315                   security.
 316                 </p>
 317               </td>
 318 </tr>
 319 <tr>
 320 <td>
 321                 <p>
 322                   <code class="varname">key_list</code>
 323                 </p>
 324               </td>
 325 <td>
 326                 <p>
 327                   A list of one or more
 328                   <code class="varname">key_id</code>s,
 329                   separated by semicolons and ending with a semicolon.
 330                 </p>
 331               </td>
 332 </tr>
 333 <tr>
 334 <td>
 335                 <p>
 336                   <code class="varname">number</code>
 337                 </p>
 338               </td>
 339 <td>
 340                 <p>
 341                   A non-negative 32-bit integer
 342                   (i.e., a number between 0 and 4294967295, inclusive).
 343                   Its acceptable value might further
 344                   be limited by the context in which it is used.
 345                 </p>
 346               </td>
 347 </tr>
 348 <tr>
 349 <td>
 350                 <p>
 351                   <code class="varname">path_name</code>
 352                 </p>
 353               </td>
 354 <td>
 355                 <p>
 356                   A quoted string which will be used as
 357                   a pathname, such as <code class="filename">zones/master/my.test.domain</code>.
 358                 </p>
 359               </td>
 360 </tr>
 361 <tr>
 362 <td>
 363                 <p>
 364                   <code class="varname">port_list</code>
 365                 </p>
 366               </td>
 367 <td>
 368                 <p>
 369                   A list of an <code class="varname">ip_port</code> or a port
 370                   range.
 371                   A port range is specified in the form of
 372                   <strong class="userinput"><code>range</code></strong> followed by
 373                   two <code class="varname">ip_port</code>s,
 374                   <code class="varname">port_low</code> and
 375                   <code class="varname">port_high</code>, which represents
 376                   port numbers from <code class="varname">port_low</code> through
 377                   <code class="varname">port_high</code>, inclusive.
 378                   <code class="varname">port_low</code> must not be larger than
 379                   <code class="varname">port_high</code>.
 380                   For example,
 381                   <strong class="userinput"><code>range 1024 65535</code></strong> represents
 382                   ports from 1024 through 65535.
 383                   In either case an asterisk (`*') character is not
 384                   allowed as a valid <code class="varname">ip_port</code>.
 385                 </p>
 386               </td>
 387 </tr>
 388 <tr>
 389 <td>
 390                 <p>
 391                   <code class="varname">size_spec</code>
 392                 </p>
 393               </td>
 394 <td>
 395                 <p>
 396                   A number, the word <strong class="userinput"><code>unlimited</code></strong>,
 397                   or the word <strong class="userinput"><code>default</code></strong>.
 398                 </p>
 399                 <p>
 400                   An <code class="varname">unlimited</code> <code class="varname">size_spec</code> requests unlimited
 401                   use, or the maximum available amount. A <code class="varname">default size_spec</code> uses
 402                   the limit that was in force when the server was started.
 403                 </p>
 404                 <p>
 405                   A <code class="varname">number</code> can optionally be
 406                   followed by a scaling factor:
 407                   <strong class="userinput"><code>K</code></strong> or <strong class="userinput"><code>k</code></strong>
 408                   for kilobytes,
 409                   <strong class="userinput"><code>M</code></strong> or <strong class="userinput"><code>m</code></strong>
 410                   for megabytes, and
 411                   <strong class="userinput"><code>G</code></strong> or <strong class="userinput"><code>g</code></strong> for gigabytes,
 412                   which scale by 1024, 1024*1024, and 1024*1024*1024
 413                   respectively.
 414                 </p>
 415                 <p>
 416                   The value must be representable as a 64-bit unsigned integer
 417                   (0 to 18446744073709551615, inclusive).
 418                   Using <code class="varname">unlimited</code> is the best
 419                   way
 420                   to safely set a really large number.
 421                 </p>
 422               </td>
 423 </tr>
 424 <tr>
 425 <td>
 426                 <p>
 427                   <code class="varname">yes_or_no</code>
 428                 </p>
 429               </td>
 430 <td>
 431                 <p>
 432                   Either <strong class="userinput"><code>yes</code></strong> or <strong class="userinput"><code>no</code></strong>.
 433                   The words <strong class="userinput"><code>true</code></strong> and <strong class="userinput"><code>false</code></strong> are
 434                   also accepted, as are the numbers <strong class="userinput"><code>1</code></strong>
 435                   and <strong class="userinput"><code>0</code></strong>.
 436                 </p>
 437               </td>
 438 </tr>
 439 <tr>
 440 <td>
 441                 <p>
 442                   <code class="varname">dialup_option</code>
 443                 </p>
 444               </td>
 445 <td>
 446                 <p>
 447                   One of <strong class="userinput"><code>yes</code></strong>,
 448                   <strong class="userinput"><code>no</code></strong>, <strong class="userinput"><code>notify</code></strong>,
 449                   <strong class="userinput"><code>notify-passive</code></strong>, <strong class="userinput"><code>refresh</code></strong> or
 450                   <strong class="userinput"><code>passive</code></strong>.
 451                   When used in a zone, <strong class="userinput"><code>notify-passive</code></strong>,
 452                   <strong class="userinput"><code>refresh</code></strong>, and <strong class="userinput"><code>passive</code></strong>
 453                   are restricted to slave and stub zones.
 454                 </p>
 455               </td>
 456 </tr>
 457 </tbody>
 458 </table></div>
 459 <div class="sect2" lang="en">
 460 <div class="titlepage"><div><div><h3 class="title">
 461 <a name="address_match_lists"></a>Address Match Lists</h3></div></div></div>
 462 <div class="sect3" lang="en">
 463 <div class="titlepage"><div><div><h4 class="title">
 464 <a name="id2573414"></a>Syntax</h4></div></div></div>
 465 <pre class="programlisting"><code class="varname">address_match_list</code> = address_match_list_element ;
 466   [<span class="optional"> address_match_list_element; ... </span>]
 467 <code class="varname">address_match_list_element</code> = [<span class="optional"> ! </span>] (ip_address [<span class="optional">/length</span>] |
 468    key key_id | acl_name | { address_match_list } )
 469 </pre>
 470 </div>
 471 <div class="sect3" lang="en">
 472 <div class="titlepage"><div><div><h4 class="title">
 473 <a name="id2573442"></a>Definition and Usage</h4></div></div></div>
 474 <p>
 475             Address match lists are primarily used to determine access
 476             control for various server operations. They are also used in
 477             the <span><strong class="command">listen-on</strong></span> and <span><strong class="command">sortlist</strong></span>
 478             statements. The elements which constitute an address match
 479             list can be any of the following:
 480           </p>
 481 <div class="itemizedlist"><ul type="disc">
 482 <li>an IP address (IPv4 or IPv6)</li>
 483 <li>an IP prefix (in `/' notation)</li>
 484 <li>
 485                 a key ID, as defined by the <span><strong class="command">key</strong></span>
 486                 statement
 487               </li>
 488 <li>the name of an address match list defined with
 489                 the <span><strong class="command">acl</strong></span> statement
 490               </li>
 491 <li>a nested address match list enclosed in braces</li>
 492 </ul></div>
 493 <p>
 494             Elements can be negated with a leading exclamation mark (`!'),
 495             and the match list names "any", "none", "localhost", and
 496             "localnets" are predefined. More information on those names
 497             can be found in the description of the acl statement.
 498           </p>
 499 <p>
 500             The addition of the key clause made the name of this syntactic
 501             element something of a misnomer, since security keys can be used
 502             to validate access without regard to a host or network address.
 503             Nonetheless, the term "address match list" is still used
 504             throughout the documentation.
 505           </p>
 506 <p>
 507             When a given IP address or prefix is compared to an address
 508             match list, the comparison takes place in approximately O(1)
 509             time.  However, key comparisons require that the list of keys
 510             be traversed until a matching key is found, and therefore may
 511             be somewhat slower.
 512           </p>
 513 <p>
 514             The interpretation of a match depends on whether the list is being
 515             used for access control, defining <span><strong class="command">listen-on</strong></span> ports, or in a
 516             <span><strong class="command">sortlist</strong></span>, and whether the element was negated.
 517           </p>
 518 <p>
 519             When used as an access control list, a non-negated match
 520             allows access and a negated match denies access. If
 521             there is no match, access is denied. The clauses
 522             <span><strong class="command">allow-notify</strong></span>,
 523             <span><strong class="command">allow-recursion</strong></span>,
 524             <span><strong class="command">allow-recursion-on</strong></span>,
 525             <span><strong class="command">allow-query</strong></span>,
 526             <span><strong class="command">allow-query-on</strong></span>,
 527             <span><strong class="command">allow-query-cache</strong></span>,
 528             <span><strong class="command">allow-query-cache-on</strong></span>,
 529             <span><strong class="command">allow-transfer</strong></span>,
 530             <span><strong class="command">allow-update</strong></span>,
 531             <span><strong class="command">allow-update-forwarding</strong></span>, and
 532             <span><strong class="command">blackhole</strong></span> all use address match
 533             lists.  Similarly, the <span><strong class="command">listen-on</strong></span> option will cause the
 534             server to refuse queries on any of the machine's
 535             addresses which do not match the list.
 536           </p>
 537 <p>
 538             Order of insertion is significant.  If more than one element
 539             in an ACL is found to match a given IP address or prefix,
 540             preference will be given to the one that came
 541             <span class="emphasis"><em>first</em></span> in the ACL definition.
 542             Because of this first-match behavior, an element that
 543             defines a subset of another element in the list should
 544             come before the broader element, regardless of whether
 545             either is negated. For example, in
 546             <span><strong class="command">1.2.3/24; ! 1.2.3.13;</strong></span>
 547             the 1.2.3.13 element is completely useless because the
 548             algorithm will match any lookup for 1.2.3.13 to the 1.2.3/24
 549             element.  Using <span><strong class="command">! 1.2.3.13; 1.2.3/24</strong></span> fixes
 550             that problem by having 1.2.3.13 blocked by the negation, but
 551             all other 1.2.3.* hosts fall through.
 552           </p>
 553 </div>
 554 </div>
 555 <div class="sect2" lang="en">
 556 <div class="titlepage"><div><div><h3 class="title">
 557 <a name="id2573716"></a>Comment Syntax</h3></div></div></div>
 558 <p>
 559           The <acronym class="acronym">BIND</acronym> 9 comment syntax allows for
 560           comments to appear
 561           anywhere that whitespace may appear in a <acronym class="acronym">BIND</acronym> configuration
 562           file. To appeal to programmers of all kinds, they can be written
 563           in the C, C++, or shell/perl style.
 564         </p>
 565 <div class="sect3" lang="en">
 566 <div class="titlepage"><div><div><h4 class="title">
 567 <a name="id2573731"></a>Syntax</h4></div></div></div>
 568 <p>
 569             </p>
 570 <pre class="programlisting">/* This is a <acronym class="acronym">BIND</acronym> comment as in C */</pre>
 571 <p>
 572             </p>
 573 <pre class="programlisting">// This is a <acronym class="acronym">BIND</acronym> comment as in C++</pre>
 574 <p>
 575             </p>
 576 <pre class="programlisting"># This is a <acronym class="acronym">BIND</acronym> comment as in common UNIX shells and perl</pre>
 577 <p>
 578           </p>
 579 </div>
 580 <div class="sect3" lang="en">
 581 <div class="titlepage"><div><div><h4 class="title">
 582 <a name="id2573761"></a>Definition and Usage</h4></div></div></div>
 583 <p>
 584             Comments may appear anywhere that whitespace may appear in
 585             a <acronym class="acronym">BIND</acronym> configuration file.
 586           </p>
 587 <p>
 588             C-style comments start with the two characters /* (slash,
 589             star) and end with */ (star, slash). Because they are completely
 590             delimited with these characters, they can be used to comment only
 591             a portion of a line or to span multiple lines.
 592           </p>
 593 <p>
 594             C-style comments cannot be nested. For example, the following
 595             is not valid because the entire comment ends with the first */:
 596           </p>
 597 <p>
 598
 599 </p>
 600 <pre class="programlisting">/* This is the start of a comment.
 601    This is still part of the comment.
 602 /* This is an incorrect attempt at nesting a comment. */
 603    This is no longer in any comment. */
 604 </pre>
 605 <p>
 606
 607           </p>
 608 <p>
 609             C++-style comments start with the two characters // (slash,
 610             slash) and continue to the end of the physical line. They cannot
 611             be continued across multiple physical lines; to have one logical
 612             comment span multiple lines, each line must use the // pair.
 613             For example:
 614           </p>
 615 <p>
 616
 617 </p>
 618 <pre class="programlisting">// This is the start of a comment.  The next line
 619 // is a new comment, even though it is logically
 620 // part of the previous comment.
 621 </pre>
 622 <p>
 623
 624           </p>
 625 <p>
 626             Shell-style (or perl-style, if you prefer) comments start
 627             with the character <code class="literal">#</code> (number sign)
 628             and continue to the end of the
 629             physical line, as in C++ comments.
 630             For example:
 631           </p>
 632 <p>
 633
 634 </p>
 635 <pre class="programlisting"># This is the start of a comment.  The next line
 636 # is a new comment, even though it is logically
 637 # part of the previous comment.
 638 </pre>
 639 <p>
 640
 641           </p>
 642 <div class="warning" style="margin-left: 0.5in; margin-right: 0.5in;">
 643 <h3 class="title">Warning</h3>
 644 <p>
 645               You cannot use the semicolon (`;') character
 646               to start a comment such as you would in a zone file. The
 647               semicolon indicates the end of a configuration
 648               statement.
 649             </p>
 650 </div>
 651 </div>
 652 </div>
 653 </div>
 654 <div class="sect1" lang="en">
 655 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
 656 <a name="Configuration_File_Grammar"></a>Configuration File Grammar</h2></div></div></div>
 657 <p>
 658         A <acronym class="acronym">BIND</acronym> 9 configuration consists of
 659         statements and comments.
 660         Statements end with a semicolon. Statements and comments are the
 661         only elements that can appear without enclosing braces. Many
 662         statements contain a block of sub-statements, which are also
 663         terminated with a semicolon.
 664       </p>
 665 <p>
 666         The following statements are supported:
 667       </p>
 668 <div class="informaltable"><table border="1">
 669 <colgroup>
 670 <col>
 671 <col>
 672 </colgroup>
 673 <tbody>
 674 <tr>
 675 <td>
 676                 <p><span><strong class="command">acl</strong></span></p>
 677               </td>
 678 <td>
 679                 <p>
 680                   defines a named IP address
 681                   matching list, for access control and other uses.
 682                 </p>
 683               </td>
 684 </tr>
 685 <tr>
 686 <td>
 687                 <p><span><strong class="command">controls</strong></span></p>
 688               </td>
 689 <td>
 690                 <p>
 691                   declares control channels to be used
 692                   by the <span><strong class="command">rndc</strong></span> utility.
 693                 </p>
 694               </td>
 695 </tr>
 696 <tr>
 697 <td>
 698                 <p><span><strong class="command">include</strong></span></p>
 699               </td>
 700 <td>
 701                 <p>
 702                   includes a file.
 703                 </p>
 704               </td>
 705 </tr>
 706 <tr>
 707 <td>
 708                 <p><span><strong class="command">key</strong></span></p>
 709               </td>
 710 <td>
 711                 <p>
 712                   specifies key information for use in
 713                   authentication and authorization using TSIG.
 714                 </p>
 715               </td>
 716 </tr>
 717 <tr>
 718 <td>
 719                 <p><span><strong class="command">logging</strong></span></p>
 720               </td>
 721 <td>
 722                 <p>
 723                   specifies what the server logs, and where
 724                   the log messages are sent.
 725                 </p>
 726               </td>
 727 </tr>
 728 <tr>
 729 <td>
 730                 <p><span><strong class="command">lwres</strong></span></p>
 731               </td>
 732 <td>
 733                 <p>
 734                   configures <span><strong class="command">named</strong></span> to
 735                   also act as a light-weight resolver daemon (<span><strong class="command">lwresd</strong></span>).
 736                 </p>
 737               </td>
 738 </tr>
 739 <tr>
 740 <td>
 741                 <p><span><strong class="command">masters</strong></span></p>
 742               </td>
 743 <td>
 744                 <p>
 745                   defines a named masters list for
 746                   inclusion in stub and slave zone masters clauses.
 747                 </p>
 748               </td>
 749 </tr>
 750 <tr>
 751 <td>
 752                 <p><span><strong class="command">options</strong></span></p>
 753               </td>
 754 <td>
 755                 <p>
 756                   controls global server configuration
 757                   options and sets defaults for other statements.
 758                 </p>
 759               </td>
 760 </tr>
 761 <tr>
 762 <td>
 763                 <p><span><strong class="command">server</strong></span></p>
 764               </td>
 765 <td>
 766                 <p>
 767                   sets certain configuration options on
 768                   a per-server basis.
 769                 </p>
 770               </td>
 771 </tr>
 772 <tr>
 773 <td>
 774                 <p><span><strong class="command">statistics-channels</strong></span></p>
 775               </td>
 776 <td>
 777                 <p>
 778                   declares communication channels to get access to
 779                   <span><strong class="command">named</strong></span> statistics.
 780                 </p>
 781               </td>
 782 </tr>
 783 <tr>
 784 <td>
 785                 <p><span><strong class="command">trusted-keys</strong></span></p>
 786               </td>
 787 <td>
 788                 <p>
 789                   defines trusted DNSSEC keys.
 790                 </p>
 791               </td>
 792 </tr>
 793 <tr>
 794 <td>
 795                 <p><span><strong class="command">view</strong></span></p>
 796               </td>
 797 <td>
 798                 <p>
 799                   defines a view.
 800                 </p>
 801               </td>
 802 </tr>
 803 <tr>
 804 <td>
 805                 <p><span><strong class="command">zone</strong></span></p>
 806               </td>
 807 <td>
 808                 <p>
 809                   defines a zone.
 810                 </p>
 811               </td>
 812 </tr>
 813 </tbody>
 814 </table></div>
 815 <p>
 816         The <span><strong class="command">logging</strong></span> and
 817         <span><strong class="command">options</strong></span> statements may only occur once
 818         per
 819         configuration.
 820       </p>
 821 <div class="sect2" lang="en">
 822 <div class="titlepage"><div><div><h3 class="title">
 823 <a name="id2574346"></a><span><strong class="command">acl</strong></span> Statement Grammar</h3></div></div></div>
 824 <pre class="programlisting"><span><strong class="command">acl</strong></span> acl-name {
 825     address_match_list
 826 };
 827 </pre>
 828 </div>
 829 <div class="sect2" lang="en">
 830 <div class="titlepage"><div><div><h3 class="title">
 831 <a name="acl"></a><span><strong class="command">acl</strong></span> Statement Definition and
 832           Usage</h3></div></div></div>
 833 <p>
 834           The <span><strong class="command">acl</strong></span> statement assigns a symbolic
 835           name to an address match list. It gets its name from a primary
 836           use of address match lists: Access Control Lists (ACLs).
 837         </p>
 838 <p>
 839           Note that an address match list's name must be defined
 840           with <span><strong class="command">acl</strong></span> before it can be used
 841           elsewhere; no forward references are allowed.
 842         </p>
 843 <p>
 844           The following ACLs are built-in:
 845         </p>
 846 <div class="informaltable"><table border="1">
 847 <colgroup>
 848 <col>
 849 <col>
 850 </colgroup>
 851 <tbody>
 852 <tr>
 853 <td>
 854                   <p><span><strong class="command">any</strong></span></p>
 855                 </td>
 856 <td>
 857                   <p>
 858                     Matches all hosts.
 859                   </p>
 860                 </td>
 861 </tr>
 862 <tr>
 863 <td>
 864                   <p><span><strong class="command">none</strong></span></p>
 865                 </td>
 866 <td>
 867                   <p>
 868                     Matches no hosts.
 869                   </p>
 870                 </td>
 871 </tr>
 872 <tr>
 873 <td>
 874                   <p><span><strong class="command">localhost</strong></span></p>
 875                 </td>
 876 <td>
 877                   <p>
 878                     Matches the IPv4 and IPv6 addresses of all network
 879                     interfaces on the system.
 880                   </p>
 881                 </td>
 882 </tr>
 883 <tr>
 884 <td>
 885                   <p><span><strong class="command">localnets</strong></span></p>
 886                 </td>
 887 <td>
 888                   <p>
 889                     Matches any host on an IPv4 or IPv6 network
 890                     for which the system has an interface.
 891                     Some systems do not provide a way to determine the prefix
 892                     lengths of
 893                     local IPv6 addresses.
 894                     In such a case, <span><strong class="command">localnets</strong></span>
 895                     only matches the local
 896                     IPv6 addresses, just like <span><strong class="command">localhost</strong></span>.
 897                   </p>
 898                 </td>
 899 </tr>
 900 </tbody>
 901 </table></div>
 902 </div>
 903 <div class="sect2" lang="en">
 904 <div class="titlepage"><div><div><h3 class="title">
 905 <a name="id2574536"></a><span><strong class="command">controls</strong></span> Statement Grammar</h3></div></div></div>
 906 <pre class="programlisting"><span><strong class="command">controls</strong></span> {
 907    [ inet ( ip_addr | * ) [ port ip_port ] allow { <em class="replaceable"><code> address_match_list </code></em> }
 908                 keys { <em class="replaceable"><code>key_list</code></em> }; ]
 909    [ inet ...; ]
 910    [ 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> }; ]
 911    [ unix ...; ]
 912 };
 913 </pre>
 914 </div>
 915 <div class="sect2" lang="en">
 916 <div class="titlepage"><div><div><h3 class="title">
 917 <a name="controls_statement_definition_and_usage"></a><span><strong class="command">controls</strong></span> Statement Definition and
 918           Usage</h3></div></div></div>
 919 <p>
 920           The <span><strong class="command">controls</strong></span> statement declares control
 921           channels to be used by system administrators to control the
 922           operation of the name server. These control channels are
 923           used by the <span><strong class="command">rndc</strong></span> utility to send
 924           commands to and retrieve non-DNS results from a name server.
 925         </p>
 926 <p>
 927           An <span><strong class="command">inet</strong></span> control channel is a TCP socket
 928           listening at the specified <span><strong class="command">ip_port</strong></span> on the
 929           specified <span><strong class="command">ip_addr</strong></span>, which can be an IPv4 or IPv6
 930           address.  An <span><strong class="command">ip_addr</strong></span> of <code class="literal">*</code> (asterisk) is
 931           interpreted as the IPv4 wildcard address; connections will be
 932           accepted on any of the system's IPv4 addresses.
 933           To listen on the IPv6 wildcard address,
 934           use an <span><strong class="command">ip_addr</strong></span> of <code class="literal">::</code>.
 935           If you will only use <span><strong class="command">rndc</strong></span> on the local host,
 936           using the loopback address (<code class="literal">127.0.0.1</code>
 937           or <code class="literal">::1</code>) is recommended for maximum security.
 938         </p>
 939 <p>
 940           If no port is specified, port 953 is used. The asterisk
 941           "<code class="literal">*</code>" cannot be used for <span><strong class="command">ip_port</strong></span>.
 942         </p>
 943 <p>
 944           The ability to issue commands over the control channel is
 945           restricted by the <span><strong class="command">allow</strong></span> and
 946           <span><strong class="command">keys</strong></span> clauses.
 947           Connections to the control channel are permitted based on the
 948           <span><strong class="command">address_match_list</strong></span>.  This is for simple
 949           IP address based filtering only; any <span><strong class="command">key_id</strong></span>
 950           elements of the <span><strong class="command">address_match_list</strong></span>
 951           are ignored.
 952         </p>
 953 <p>
 954           A <span><strong class="command">unix</strong></span> control channel is a UNIX domain
 955           socket listening at the specified path in the file system.
 956           Access to the socket is specified by the <span><strong class="command">perm</strong></span>,
 957           <span><strong class="command">owner</strong></span> and <span><strong class="command">group</strong></span> clauses.
 958           Note on some platforms (SunOS and Solaris) the permissions
 959           (<span><strong class="command">perm</strong></span>) are applied to the parent directory
 960           as the permissions on the socket itself are ignored.
 961         </p>
 962 <p>
 963           The primary authorization mechanism of the command
 964           channel is the <span><strong class="command">key_list</strong></span>, which
 965           contains a list of <span><strong class="command">key_id</strong></span>s.
 966           Each <span><strong class="command">key_id</strong></span> in the <span><strong class="command">key_list</strong></span>
 967           is authorized to execute commands over the control channel.
 968           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>)
 969           for information about configuring keys in <span><strong class="command">rndc</strong></span>.
 970         </p>
 971 <p>
 972           If no <span><strong class="command">controls</strong></span> statement is present,
 973           <span><strong class="command">named</strong></span> will set up a default
 974           control channel listening on the loopback address 127.0.0.1
 975           and its IPv6 counterpart ::1.
 976           In this case, and also when the <span><strong class="command">controls</strong></span> statement
 977           is present but does not have a <span><strong class="command">keys</strong></span> clause,
 978           <span><strong class="command">named</strong></span> will attempt to load the command channel key
 979           from the file <code class="filename">rndc.key</code> in
 980           <code class="filename">/etc</code> (or whatever <code class="varname">sysconfdir</code>
 981           was specified as when <acronym class="acronym">BIND</acronym> was built).
 982           To create a <code class="filename">rndc.key</code> file, run
 983           <strong class="userinput"><code>rndc-confgen -a</code></strong>.
 984         </p>
 985 <p>
 986           The <code class="filename">rndc.key</code> feature was created to
 987           ease the transition of systems from <acronym class="acronym">BIND</acronym> 8,
 988           which did not have digital signatures on its command channel
 989           messages and thus did not have a <span><strong class="command">keys</strong></span> clause.
 990
 991           It makes it possible to use an existing <acronym class="acronym">BIND</acronym> 8
 992           configuration file in <acronym class="acronym">BIND</acronym> 9 unchanged,
 993           and still have <span><strong class="command">rndc</strong></span> work the same way
 994           <span><strong class="command">ndc</strong></span> worked in BIND 8, simply by executing the
 995           command <strong class="userinput"><code>rndc-confgen -a</code></strong> after BIND 9 is
 996           installed.
 997         </p>
 998 <p>
 999           Since the <code class="filename">rndc.key</code> feature
1000           is only intended to allow the backward-compatible usage of
1001           <acronym class="acronym">BIND</acronym> 8 configuration files, this
1002           feature does not
1003           have a high degree of configurability.  You cannot easily change
1004           the key name or the size of the secret, so you should make a
1005           <code class="filename">rndc.conf</code> with your own key if you
1006           wish to change
1007           those things.  The <code class="filename">rndc.key</code> file
1008           also has its
1009           permissions set such that only the owner of the file (the user that
1010           <span><strong class="command">named</strong></span> is running as) can access it.
1011           If you
1012           desire greater flexibility in allowing other users to access
1013           <span><strong class="command">rndc</strong></span> commands, then you need to create
1014           a
1015           <code class="filename">rndc.conf</code> file and make it group
1016           readable by a group
1017           that contains the users who should have access.
1018         </p>
1019 <p>
1020           To disable the command channel, use an empty
1021           <span><strong class="command">controls</strong></span> statement:
1022           <span><strong class="command">controls { };</strong></span>.
1023         </p>
1024 </div>
1025 <div class="sect2" lang="en">
1026 <div class="titlepage"><div><div><h3 class="title">
1027 <a name="id2574965"></a><span><strong class="command">include</strong></span> Statement Grammar</h3></div></div></div>
1028 <pre class="programlisting"><span><strong class="command">include</strong></span> <em class="replaceable"><code>filename</code></em>;</pre>
1029 </div>
1030 <div class="sect2" lang="en">
1031 <div class="titlepage"><div><div><h3 class="title">
1032 <a name="id2574982"></a><span><strong class="command">include</strong></span> Statement Definition and
1033           Usage</h3></div></div></div>
1034 <p>
1035           The <span><strong class="command">include</strong></span> statement inserts the
1036           specified file at the point where the <span><strong class="command">include</strong></span>
1037           statement is encountered. The <span><strong class="command">include</strong></span>
1038                 statement facilitates the administration of configuration
1039           files
1040           by permitting the reading or writing of some things but not
1041           others. For example, the statement could include private keys
1042           that are readable only by the name server.
1043         </p>
1044 </div>
1045 <div class="sect2" lang="en">
1046 <div class="titlepage"><div><div><h3 class="title">
1047 <a name="id2575005"></a><span><strong class="command">key</strong></span> Statement Grammar</h3></div></div></div>
1048 <pre class="programlisting"><span><strong class="command">key</strong></span> <em class="replaceable"><code>key_id</code></em> {
1049     algorithm <em class="replaceable"><code>string</code></em>;
1050     secret <em class="replaceable"><code>string</code></em>;
1051 };
1052 </pre>
1053 </div>
1054 <div class="sect2" lang="en">
1055 <div class="titlepage"><div><div><h3 class="title">
1056 <a name="id2575029"></a><span><strong class="command">key</strong></span> Statement Definition and Usage</h3></div></div></div>
1057 <p>
1058           The <span><strong class="command">key</strong></span> statement defines a shared
1059           secret key for use with TSIG (see <a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
1060           or the command channel
1061           (see <a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and
1062           Usage">the section called &#8220;<span><strong class="command">controls</strong></span> Statement Definition and
1063           Usage&#8221;</a>).
1064         </p>
1065 <p>
1066           The <span><strong class="command">key</strong></span> statement can occur at the
1067           top level
1068           of the configuration file or inside a <span><strong class="command">view</strong></span>
1069           statement.  Keys defined in top-level <span><strong class="command">key</strong></span>
1070           statements can be used in all views.  Keys intended for use in
1071           a <span><strong class="command">controls</strong></span> statement
1072           (see <a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and
1073           Usage">the section called &#8220;<span><strong class="command">controls</strong></span> Statement Definition and
1074           Usage&#8221;</a>)
1075           must be defined at the top level.
1076         </p>
1077 <p>
1078           The <em class="replaceable"><code>key_id</code></em>, also known as the
1079           key name, is a domain name uniquely identifying the key. It can
1080           be used in a <span><strong class="command">server</strong></span>
1081           statement to cause requests sent to that
1082           server to be signed with this key, or in address match lists to
1083           verify that incoming requests have been signed with a key
1084           matching this name, algorithm, and secret.
1085         </p>
1086 <p>
1087           The <em class="replaceable"><code>algorithm_id</code></em> is a string
1088           that specifies a security/authentication algorithm.  Named
1089           supports <code class="literal">hmac-md5</code>,
1090           <code class="literal">hmac-sha1</code>, <code class="literal">hmac-sha224</code>,
1091           <code class="literal">hmac-sha256</code>, <code class="literal">hmac-sha384</code>
1092           and <code class="literal">hmac-sha512</code> TSIG authentication.
1093           Truncated hashes are supported by appending the minimum
1094           number of required bits preceded by a dash, e.g.
1095           <code class="literal">hmac-sha1-80</code>.  The
1096           <em class="replaceable"><code>secret_string</code></em> is the secret
1097           to be used by the algorithm, and is treated as a base-64
1098           encoded string.
1099         </p>
1100 </div>
1101 <div class="sect2" lang="en">
1102 <div class="titlepage"><div><div><h3 class="title">
1103 <a name="id2575120"></a><span><strong class="command">logging</strong></span> Statement Grammar</h3></div></div></div>
1104 <pre class="programlisting"><span><strong class="command">logging</strong></span> {
1105    [ <span><strong class="command">channel</strong></span> <em class="replaceable"><code>channel_name</code></em> {
1106      ( <span><strong class="command">file</strong></span> <em class="replaceable"><code>path_name</code></em>
1107          [ <span><strong class="command">versions</strong></span> ( <em class="replaceable"><code>number</code></em> | <span><strong class="command">unlimited</strong></span> ) ]
1108          [ <span><strong class="command">size</strong></span> <em class="replaceable"><code>size spec</code></em> ]
1109        | <span><strong class="command">syslog</strong></span> <em class="replaceable"><code>syslog_facility</code></em>
1110        | <span><strong class="command">stderr</strong></span>
1111        | <span><strong class="command">null</strong></span> );
1112      [ <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> |
1113                  <code class="option">info</code> | <code class="option">debug</code> [ <em class="replaceable"><code>level</code></em> ] | <code class="option">dynamic</code> ); ]
1114      [ <span><strong class="command">print-category</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1115      [ <span><strong class="command">print-severity</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1116      [ <span><strong class="command">print-time</strong></span> <code class="option">yes</code> or <code class="option">no</code>; ]
1117    }; ]
1118    [ <span><strong class="command">category</strong></span> <em class="replaceable"><code>category_name</code></em> {
1119      <em class="replaceable"><code>channel_name</code></em> ; [ <em class="replaceable"><code>channel_name</code></em> ; ... ]
1120    }; ]
1121    ...
1122 };
1123 </pre>
1124 </div>
1125 <div class="sect2" lang="en">
1126 <div class="titlepage"><div><div><h3 class="title">
1127 <a name="id2575245"></a><span><strong class="command">logging</strong></span> Statement Definition and
1128           Usage</h3></div></div></div>
1129 <p>
1130           The <span><strong class="command">logging</strong></span> statement configures a
1131           wide
1132           variety of logging options for the name server. Its <span><strong class="command">channel</strong></span> phrase
1133           associates output methods, format options and severity levels with
1134           a name that can then be used with the <span><strong class="command">category</strong></span> phrase
1135           to select how various classes of messages are logged.
1136         </p>
1137 <p>
1138           Only one <span><strong class="command">logging</strong></span> statement is used to
1139           define
1140           as many channels and categories as are wanted. If there is no <span><strong class="command">logging</strong></span> statement,
1141           the logging configuration will be:
1142         </p>
1143 <pre class="programlisting">logging {
1144      category default { default_syslog; default_debug; };
1145      category unmatched { null; };
1146 };
1147 </pre>
1148 <p>
1149           In <acronym class="acronym">BIND</acronym> 9, the logging configuration
1150           is only established when
1151           the entire configuration file has been parsed.  In <acronym class="acronym">BIND</acronym> 8, it was
1152           established as soon as the <span><strong class="command">logging</strong></span>
1153           statement
1154           was parsed. When the server is starting up, all logging messages
1155           regarding syntax errors in the configuration file go to the default
1156           channels, or to standard error if the "<code class="option">-g</code>" option
1157           was specified.
1158         </p>
1159 <div class="sect3" lang="en">
1160 <div class="titlepage"><div><div><h4 class="title">
1161 <a name="id2575298"></a>The <span><strong class="command">channel</strong></span> Phrase</h4></div></div></div>
1162 <p>
1163             All log output goes to one or more <span class="emphasis"><em>channels</em></span>;
1164             you can make as many of them as you want.
1165           </p>
1166 <p>
1167             Every channel definition must include a destination clause that
1168             says whether messages selected for the channel go to a file, to a
1169             particular syslog facility, to the standard error stream, or are
1170             discarded. It can optionally also limit the message severity level
1171             that will be accepted by the channel (the default is
1172             <span><strong class="command">info</strong></span>), and whether to include a
1173             <span><strong class="command">named</strong></span>-generated time stamp, the
1174             category name
1175             and/or severity level (the default is not to include any).
1176           </p>
1177 <p>
1178             The <span><strong class="command">null</strong></span> destination clause
1179             causes all messages sent to the channel to be discarded;
1180             in that case, other options for the channel are meaningless.
1181           </p>
1182 <p>
1183             The <span><strong class="command">file</strong></span> destination clause directs
1184             the channel
1185             to a disk file.  It can include limitations
1186             both on how large the file is allowed to become, and how many
1187             versions
1188             of the file will be saved each time the file is opened.
1189           </p>
1190 <p>
1191             If you use the <span><strong class="command">versions</strong></span> log file
1192             option, then
1193             <span><strong class="command">named</strong></span> will retain that many backup
1194             versions of the file by
1195             renaming them when opening.  For example, if you choose to keep
1196             three old versions
1197             of the file <code class="filename">lamers.log</code>, then just
1198             before it is opened
1199             <code class="filename">lamers.log.1</code> is renamed to
1200             <code class="filename">lamers.log.2</code>, <code class="filename">lamers.log.0</code> is renamed
1201             to <code class="filename">lamers.log.1</code>, and <code class="filename">lamers.log</code> is
1202             renamed to <code class="filename">lamers.log.0</code>.
1203             You can say <span><strong class="command">versions unlimited</strong></span> to
1204             not limit
1205             the number of versions.
1206             If a <span><strong class="command">size</strong></span> option is associated with
1207             the log file,
1208             then renaming is only done when the file being opened exceeds the
1209             indicated size.  No backup versions are kept by default; any
1210             existing
1211             log file is simply appended.
1212           </p>
1213 <p>
1214             The <span><strong class="command">size</strong></span> option for files is used
1215             to limit log
1216             growth. If the file ever exceeds the size, then <span><strong class="command">named</strong></span> will
1217             stop writing to the file unless it has a <span><strong class="command">versions</strong></span> option
1218             associated with it.  If backup versions are kept, the files are
1219             rolled as
1220             described above and a new one begun.  If there is no
1221             <span><strong class="command">versions</strong></span> option, no more data will
1222             be written to the log
1223             until some out-of-band mechanism removes or truncates the log to
1224             less than the
1225             maximum size.  The default behavior is not to limit the size of
1226             the
1227             file.
1228           </p>
1229 <p>
1230             Example usage of the <span><strong class="command">size</strong></span> and
1231             <span><strong class="command">versions</strong></span> options:
1232           </p>
1233 <pre class="programlisting">channel an_example_channel {
1234     file "example.log" versions 3 size 20m;
1235     print-time yes;
1236     print-category yes;
1237 };
1238 </pre>
1239 <p>
1240             The <span><strong class="command">syslog</strong></span> destination clause
1241             directs the
1242             channel to the system log.  Its argument is a
1243             syslog facility as described in the <span><strong class="command">syslog</strong></span> man
1244             page. Known facilities are <span><strong class="command">kern</strong></span>, <span><strong class="command">user</strong></span>,
1245             <span><strong class="command">mail</strong></span>, <span><strong class="command">daemon</strong></span>, <span><strong class="command">auth</strong></span>,
1246             <span><strong class="command">syslog</strong></span>, <span><strong class="command">lpr</strong></span>, <span><strong class="command">news</strong></span>,
1247             <span><strong class="command">uucp</strong></span>, <span><strong class="command">cron</strong></span>, <span><strong class="command">authpriv</strong></span>,
1248             <span><strong class="command">ftp</strong></span>, <span><strong class="command">local0</strong></span>, <span><strong class="command">local1</strong></span>,
1249             <span><strong class="command">local2</strong></span>, <span><strong class="command">local3</strong></span>, <span><strong class="command">local4</strong></span>,
1250             <span><strong class="command">local5</strong></span>, <span><strong class="command">local6</strong></span> and
1251             <span><strong class="command">local7</strong></span>, however not all facilities
1252             are supported on
1253             all operating systems.
1254             How <span><strong class="command">syslog</strong></span> will handle messages
1255             sent to
1256             this facility is described in the <span><strong class="command">syslog.conf</strong></span> man
1257             page. If you have a system which uses a very old version of <span><strong class="command">syslog</strong></span> that
1258             only uses two arguments to the <span><strong class="command">openlog()</strong></span> function,
1259             then this clause is silently ignored.
1260           </p>
1261 <p>
1262             The <span><strong class="command">severity</strong></span> clause works like <span><strong class="command">syslog</strong></span>'s
1263             "priorities", except that they can also be used if you are writing
1264             straight to a file rather than using <span><strong class="command">syslog</strong></span>.
1265             Messages which are not at least of the severity level given will
1266             not be selected for the channel; messages of higher severity
1267             levels
1268             will be accepted.
1269           </p>
1270 <p>
1271             If you are using <span><strong class="command">syslog</strong></span>, then the <span><strong class="command">syslog.conf</strong></span> priorities
1272             will also determine what eventually passes through. For example,
1273             defining a channel facility and severity as <span><strong class="command">daemon</strong></span> and <span><strong class="command">debug</strong></span> but
1274             only logging <span><strong class="command">daemon.warning</strong></span> via <span><strong class="command">syslog.conf</strong></span> will
1275             cause messages of severity <span><strong class="command">info</strong></span> and
1276             <span><strong class="command">notice</strong></span> to
1277             be dropped. If the situation were reversed, with <span><strong class="command">named</strong></span> writing
1278             messages of only <span><strong class="command">warning</strong></span> or higher,
1279             then <span><strong class="command">syslogd</strong></span> would
1280             print all messages it received from the channel.
1281           </p>
1282 <p>
1283             The <span><strong class="command">stderr</strong></span> destination clause
1284             directs the
1285             channel to the server's standard error stream.  This is intended
1286             for
1287             use when the server is running as a foreground process, for
1288             example
1289             when debugging a configuration.
1290           </p>
1291 <p>
1292             The server can supply extensive debugging information when
1293             it is in debugging mode. If the server's global debug level is
1294             greater
1295             than zero, then debugging mode will be active. The global debug
1296             level is set either by starting the <span><strong class="command">named</strong></span> server
1297             with the <code class="option">-d</code> flag followed by a positive integer,
1298             or by running <span><strong class="command">rndc trace</strong></span>.
1299             The global debug level
1300             can be set to zero, and debugging mode turned off, by running <span><strong class="command">rndc
1301 notrace</strong></span>. All debugging messages in the server have a debug
1302             level, and higher debug levels give more detailed output. Channels
1303             that specify a specific debug severity, for example:
1304           </p>
1305 <pre class="programlisting">channel specific_debug_level {
1306     file "foo";
1307     severity debug 3;
1308 };
1309 </pre>
1310 <p>
1311             will get debugging output of level 3 or less any time the
1312             server is in debugging mode, regardless of the global debugging
1313             level. Channels with <span><strong class="command">dynamic</strong></span>
1314             severity use the
1315             server's global debug level to determine what messages to print.
1316           </p>
1317 <p>
1318             If <span><strong class="command">print-time</strong></span> has been turned on,
1319             then
1320             the date and time will be logged. <span><strong class="command">print-time</strong></span> may
1321             be specified for a <span><strong class="command">syslog</strong></span> channel,
1322             but is usually
1323             pointless since <span><strong class="command">syslog</strong></span> also logs
1324             the date and
1325             time. If <span><strong class="command">print-category</strong></span> is
1326             requested, then the
1327             category of the message will be logged as well. Finally, if <span><strong class="command">print-severity</strong></span> is
1328             on, then the severity level of the message will be logged. The <span><strong class="command">print-</strong></span> options may
1329             be used in any combination, and will always be printed in the
1330             following
1331             order: time, category, severity. Here is an example where all
1332             three <span><strong class="command">print-</strong></span> options
1333             are on:
1334           </p>
1335 <p>
1336             <code class="computeroutput">28-Feb-2000 15:05:32.863 general: notice: running</code>
1337           </p>
1338 <p>
1339             There are four predefined channels that are used for
1340             <span><strong class="command">named</strong></span>'s default logging as follows.
1341             How they are
1342             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>.
1343           </p>
1344 <pre class="programlisting">channel default_syslog {
1345     syslog daemon;                      // send to syslog's daemon
1346                                         // facility
1347     severity info;                      // only send priority info
1348                                         // and higher
1349 };
1350
1351 channel default_debug {
1352     file "named.run";                   // write to named.run in
1353                                         // the working directory
1354                                         // Note: stderr is used instead
1355                                         // of "named.run"
1356                                         // if the server is started
1357                                         // with the '-f' option.
1358     severity dynamic;                   // log at the server's
1359                                         // current debug level
1360 };
1361
1362 channel default_stderr {
1363     stderr;                             // writes to stderr
1364     severity info;                      // only send priority info
1365                                         // and higher
1366 };
1367
1368 channel null {
1369    null;                                // toss anything sent to
1370                                         // this channel
1371 };
1372 </pre>
1373 <p>
1374             The <span><strong class="command">default_debug</strong></span> channel has the
1375             special
1376             property that it only produces output when the server's debug
1377             level is
1378             nonzero.  It normally writes to a file called <code class="filename">named.run</code>
1379             in the server's working directory.
1380           </p>
1381 <p>
1382             For security reasons, when the "<code class="option">-u</code>"
1383             command line option is used, the <code class="filename">named.run</code> file
1384             is created only after <span><strong class="command">named</strong></span> has
1385             changed to the
1386             new UID, and any debug output generated while <span><strong class="command">named</strong></span> is
1387             starting up and still running as root is discarded.  If you need
1388             to capture this output, you must run the server with the "<code class="option">-g</code>"
1389             option and redirect standard error to a file.
1390           </p>
1391 <p>
1392             Once a channel is defined, it cannot be redefined. Thus you
1393             cannot alter the built-in channels directly, but you can modify
1394             the default logging by pointing categories at channels you have
1395             defined.
1396           </p>
1397 </div>
1398 <div class="sect3" lang="en">
1399 <div class="titlepage"><div><div><h4 class="title">
1400 <a name="the_category_phrase"></a>The <span><strong class="command">category</strong></span> Phrase</h4></div></div></div>
1401 <p>
1402             There are many categories, so you can send the logs you want
1403             to see wherever you want, without seeing logs you don't want. If
1404             you don't specify a list of channels for a category, then log
1405             messages
1406             in that category will be sent to the <span><strong class="command">default</strong></span> category
1407             instead. If you don't specify a default category, the following
1408             "default default" is used:
1409           </p>
1410 <pre class="programlisting">category default { default_syslog; default_debug; };
1411 </pre>
1412 <p>
1413             As an example, let's say you want to log security events to
1414             a file, but you also want keep the default logging behavior. You'd
1415             specify the following:
1416           </p>
1417 <pre class="programlisting">channel my_security_channel {
1418     file "my_security_file";
1419     severity info;
1420 };
1421 category security {
1422     my_security_channel;
1423     default_syslog;
1424     default_debug;
1425 };</pre>
1426 <p>
1427             To discard all messages in a category, specify the <span><strong class="command">null</strong></span> channel:
1428           </p>
1429 <pre class="programlisting">category xfer-out { null; };
1430 category notify { null; };
1431 </pre>
1432 <p>
1433             Following are the available categories and brief descriptions
1434             of the types of log information they contain. More
1435             categories may be added in future <acronym class="acronym">BIND</acronym> releases.
1436           </p>
1437 <div class="informaltable"><table border="1">
1438 <colgroup>
1439 <col>
1440 <col>
1441 </colgroup>
1442 <tbody>
1443 <tr>
1444 <td>
1445                     <p><span><strong class="command">default</strong></span></p>
1446                   </td>
1447 <td>
1448                     <p>
1449                       The default category defines the logging
1450                       options for those categories where no specific
1451                       configuration has been
1452                       defined.
1453                     </p>
1454                   </td>
1455 </tr>
1456 <tr>
1457 <td>
1458                     <p><span><strong class="command">general</strong></span></p>
1459                   </td>
1460 <td>
1461                     <p>
1462                       The catch-all. Many things still aren't
1463                       classified into categories, and they all end up here.
1464                     </p>
1465                   </td>
1466 </tr>
1467 <tr>
1468 <td>
1469                     <p><span><strong class="command">database</strong></span></p>
1470                   </td>
1471 <td>
1472                     <p>
1473                       Messages relating to the databases used
1474                       internally by the name server to store zone and cache
1475                       data.
1476                     </p>
1477                   </td>
1478 </tr>
1479 <tr>
1480 <td>
1481                     <p><span><strong class="command">security</strong></span></p>
1482                   </td>
1483 <td>
1484                     <p>
1485                       Approval and denial of requests.
1486                     </p>
1487                   </td>
1488 </tr>
1489 <tr>
1490 <td>
1491                     <p><span><strong class="command">config</strong></span></p>
1492                   </td>
1493 <td>
1494                     <p>
1495                       Configuration file parsing and processing.
1496                     </p>
1497                   </td>
1498 </tr>
1499 <tr>
1500 <td>
1501                     <p><span><strong class="command">resolver</strong></span></p>
1502                   </td>
1503 <td>
1504                     <p>
1505                       DNS resolution, such as the recursive
1506                       lookups performed on behalf of clients by a caching name
1507                       server.
1508                     </p>
1509                   </td>
1510 </tr>
1511 <tr>
1512 <td>
1513                     <p><span><strong class="command">xfer-in</strong></span></p>
1514                   </td>
1515 <td>
1516                     <p>
1517                       Zone transfers the server is receiving.
1518                     </p>
1519                   </td>
1520 </tr>
1521 <tr>
1522 <td>
1523                     <p><span><strong class="command">xfer-out</strong></span></p>
1524                   </td>
1525 <td>
1526                     <p>
1527                       Zone transfers the server is sending.
1528                     </p>
1529                   </td>
1530 </tr>
1531 <tr>
1532 <td>
1533                     <p><span><strong class="command">notify</strong></span></p>
1534                   </td>
1535 <td>
1536                     <p>
1537                       The NOTIFY protocol.
1538                     </p>
1539                   </td>
1540 </tr>
1541 <tr>
1542 <td>
1543                     <p><span><strong class="command">client</strong></span></p>
1544                   </td>
1545 <td>
1546                     <p>
1547                       Processing of client requests.
1548                     </p>
1549                   </td>
1550 </tr>
1551 <tr>
1552 <td>
1553                     <p><span><strong class="command">unmatched</strong></span></p>
1554                   </td>
1555 <td>
1556                     <p>
1557                       Messages that <span><strong class="command">named</strong></span> was unable to determine the
1558                       class of or for which there was no matching <span><strong class="command">view</strong></span>.
1559                       A one line summary is also logged to the <span><strong class="command">client</strong></span> category.
1560                       This category is best sent to a file or stderr, by
1561                       default it is sent to
1562                       the <span><strong class="command">null</strong></span> channel.
1563                     </p>
1564                   </td>
1565 </tr>
1566 <tr>
1567 <td>
1568                     <p><span><strong class="command">network</strong></span></p>
1569                   </td>
1570 <td>
1571                     <p>
1572                       Network operations.
1573                     </p>
1574                   </td>
1575 </tr>
1576 <tr>
1577 <td>
1578                     <p><span><strong class="command">update</strong></span></p>
1579                   </td>
1580 <td>
1581                     <p>
1582                       Dynamic updates.
1583                     </p>
1584                   </td>
1585 </tr>
1586 <tr>
1587 <td>
1588                     <p><span><strong class="command">update-security</strong></span></p>
1589                   </td>
1590 <td>
1591                     <p>
1592                       Approval and denial of update requests.
1593                     </p>
1594                   </td>
1595 </tr>
1596 <tr>
1597 <td>
1598                     <p><span><strong class="command">queries</strong></span></p>
1599                   </td>
1600 <td>
1601                     <p>
1602                       Specify where queries should be logged to.
1603                     </p>
1604                     <p>
1605                       At startup, specifying the category <span><strong class="command">queries</strong></span> will also
1606                       enable query logging unless <span><strong class="command">querylog</strong></span> option has been
1607                       specified.
1608                     </p>
1609
1610                     <p>
1611                       The query log entry reports the client's IP
1612                       address and port number, and the query name,
1613                       class and type.  It also reports whether the
1614                       Recursion Desired flag was set (+ if set, -
1615                       if not set), if the query was signed (S),
1616                       EDNS was in use (E), if DO (DNSSEC Ok) was
1617                       set (D), or if CD (Checking Disabled) was set
1618                       (C).
1619                     </p>
1620
1621                     <p>
1622                       <code class="computeroutput">client 127.0.0.1#62536: query: www.example.com IN AAAA +SE</code>
1623                     </p>
1624                     <p>
1625                       <code class="computeroutput">client ::1#62537: query: www.example.net IN AAAA -SE</code>
1626                     </p>
1627                   </td>
1628 </tr>
1629 <tr>
1630 <td>
1631                     <p><span><strong class="command">query-errors</strong></span></p>
1632                   </td>
1633 <td>
1634                     <p>
1635                       Information about queries that resulted in some
1636                       failure.
1637                     </p>
1638                   </td>
1639 </tr>
1640 <tr>
1641 <td>
1642                     <p><span><strong class="command">dispatch</strong></span></p>
1643                   </td>
1644 <td>
1645                     <p>
1646                       Dispatching of incoming packets to the
1647                       server modules where they are to be processed.
1648                     </p>
1649                   </td>
1650 </tr>
1651 <tr>
1652 <td>
1653                     <p><span><strong class="command">dnssec</strong></span></p>
1654                   </td>
1655 <td>
1656                     <p>
1657                       DNSSEC and TSIG protocol processing.
1658                     </p>
1659                   </td>
1660 </tr>
1661 <tr>
1662 <td>
1663                     <p><span><strong class="command">lame-servers</strong></span></p>
1664                   </td>
1665 <td>
1666                     <p>
1667                       Lame servers.  These are misconfigurations
1668                       in remote servers, discovered by BIND 9 when trying to
1669                       query
1670                       those servers during resolution.
1671                     </p>
1672                   </td>
1673 </tr>
1674 <tr>
1675 <td>
1676                     <p><span><strong class="command">delegation-only</strong></span></p>
1677                   </td>
1678 <td>
1679                     <p>
1680                       Delegation only.  Logs queries that have been
1681                       forced to NXDOMAIN as the result of a
1682                       delegation-only zone or a
1683                       <span><strong class="command">delegation-only</strong></span> in a hint
1684                       or stub zone declaration.
1685                     </p>
1686                   </td>
1687 </tr>
1688 <tr>
1689 <td>
1690                     <p><span><strong class="command">edns-disabled</strong></span></p>
1691                   </td>
1692 <td>
1693                     <p>
1694                       Log queries that have been forced to use plain
1695                       DNS due to timeouts.  This is often due to
1696                       the remote servers not being RFC 1034 compliant
1697                       (not always returning FORMERR or similar to
1698                       EDNS queries and other extensions to the DNS
1699                       when they are not understood).  In other words, this is
1700                       targeted at servers that fail to respond to
1701                       DNS queries that they don't understand.
1702                     </p>
1703                     <p>
1704                       Note: the log message can also be due to
1705                       packet loss.  Before reporting servers for
1706                       non-RFC 1034 compliance they should be re-tested
1707                       to determine the nature of the non-compliance.
1708                       This testing should prevent or reduce the
1709                       number of false-positive reports.
1710                     </p>
1711                     <p>
1712                       Note: eventually <span><strong class="command">named</strong></span> will have to stop
1713                       treating such timeouts as due to RFC 1034 non
1714                       compliance and start treating it as plain
1715                       packet loss.  Falsely classifying packet
1716                       loss as due to RFC 1034 non compliance impacts
1717                       on DNSSEC validation which requires EDNS for
1718                       the DNSSEC records to be returned.
1719                     </p>
1720                   </td>
1721 </tr>
1722 </tbody>
1723 </table></div>
1724 </div>
1725 <div class="sect3" lang="en">
1726 <div class="titlepage"><div><div><h4 class="title">
1727 <a name="id2576793"></a>The <span><strong class="command">query-errors</strong></span> Category</h4></div></div></div>
1728 <p>
1729             The <span><strong class="command">query-errors</strong></span> category is
1730             specifically intended for debugging purposes: To identify
1731             why and how specific queries result in responses which
1732             indicate an error.
1733             Messages of this category are therefore only logged
1734             with <span><strong class="command">debug</strong></span> levels.
1735           </p>
1736 <p>
1737             At the debug levels of 1 or higher, each response with the
1738             rcode of SERVFAIL is logged as follows:
1739           </p>
1740 <p>
1741             <code class="computeroutput">client 127.0.0.1#61502: query failed (SERVFAIL) for www.example.com/IN/AAAA at query.c:3880</code>
1742           </p>
1743 <p>
1744             This means an error resulting in SERVFAIL was
1745             detected at line 3880 of source file
1746             <code class="filename">query.c</code>.
1747             Log messages of this level will particularly
1748             help identify the cause of SERVFAIL for an
1749             authoritative server.
1750           </p>
1751 <p>
1752             At the debug levels of 2 or higher, detailed context
1753             information of recursive resolutions that resulted in
1754             SERVFAIL is logged.
1755             The log message will look like as follows:
1756           </p>
1757 <p>
1758             <code class="computeroutput">fetch completed at resolver.c:2970 for www.example.com/A in 30.000183: timed out/success [domain:example.com,referral:2,restart:7,qrysent:8,timeout:5,lame:0,neterr:0,badresp:1,adberr:0,findfail:0,valfail:0]</code>
1759           </p>
1760 <p>
1761             The first part before the colon shows that a recursive
1762             resolution for AAAA records of www.example.com completed
1763             in 30.000183 seconds and the final result that led to the
1764             SERVFAIL was determined at line 2970 of source file
1765             <code class="filename">resolver.c</code>.
1766           </p>
1767 <p>
1768             The following part shows the detected final result and the
1769             latest result of DNSSEC validation.
1770             The latter is always success when no validation attempt
1771             is made.
1772             In this example, this query resulted in SERVFAIL probably
1773             because all name servers are down or unreachable, leading
1774             to a timeout in 30 seconds.
1775             DNSSEC validation was probably not attempted.
1776           </p>
1777 <p>
1778             The last part enclosed in square brackets shows statistics
1779             information collected for this particular resolution
1780             attempt.
1781             The <code class="varname">domain</code> field shows the deepest zone
1782             that the resolver reached;
1783             it is the zone where the error was finally detected.
1784             The meaning of the other fields is summarized in the
1785             following table.
1786           </p>
1787 <div class="informaltable"><table border="1">
1788 <colgroup>
1789 <col>
1790 <col>
1791 </colgroup>
1792 <tbody>
1793 <tr>
1794 <td>
1795                     <p><code class="varname">referral</code></p>
1796                   </td>
1797 <td>
1798                     <p>
1799                       The number of referrals the resolver received
1800                       throughout the resolution process.
1801                       In the above example this is 2, which are most
1802                       likely com and example.com.
1803                     </p>
1804                   </td>
1805 </tr>
1806 <tr>
1807 <td>
1808                     <p><code class="varname">restart</code></p>
1809                   </td>
1810 <td>
1811                     <p>
1812                       The number of cycles that the resolver tried
1813                       remote servers at the <code class="varname">domain</code>
1814                       zone.
1815                       In each cycle the resolver sends one query
1816                       (possibly resending it, depending on the response)
1817                       to each known name server of
1818                       the <code class="varname">domain</code> zone.
1819                     </p>
1820                   </td>
1821 </tr>
1822 <tr>
1823 <td>
1824                     <p><code class="varname">qrysent</code></p>
1825                   </td>
1826 <td>
1827                     <p>
1828                       The number of queries the resolver sent at the
1829                       <code class="varname">domain</code> zone.
1830                     </p>
1831                   </td>
1832 </tr>
1833 <tr>
1834 <td>
1835                     <p><code class="varname">timeout</code></p>
1836                   </td>
1837 <td>
1838                     <p>
1839                       The number of timeouts since the resolver
1840                       received the last response.
1841                     </p>
1842                   </td>
1843 </tr>
1844 <tr>
1845 <td>
1846                     <p><code class="varname">lame</code></p>
1847                   </td>
1848 <td>
1849                     <p>
1850                       The number of lame servers the resolver detected
1851                       at the <code class="varname">domain</code> zone.
1852                       A server is detected to be lame either by an
1853                       invalid response or as a result of lookup in
1854                       BIND9's address database (ADB), where lame
1855                       servers are cached.
1856                     </p>
1857                   </td>
1858 </tr>
1859 <tr>
1860 <td>
1861                     <p><code class="varname">neterr</code></p>
1862                   </td>
1863 <td>
1864                     <p>
1865                       The number of erroneous results that the
1866                       resolver encountered in sending queries
1867                       at the <code class="varname">domain</code> zone.
1868                       One common case is the remote server is
1869                       unreachable and the resolver receives an ICMP
1870                       unreachable error message.
1871                     </p>
1872                   </td>
1873 </tr>
1874 <tr>
1875 <td>
1876                     <p><code class="varname">badresp</code></p>
1877                   </td>
1878 <td>
1879                     <p>
1880                       The number of unexpected responses (other than
1881                       <code class="varname">lame</code>) to queries sent by the
1882                       resolver at the <code class="varname">domain</code> zone.
1883                     </p>
1884                   </td>
1885 </tr>
1886 <tr>
1887 <td>
1888                     <p><code class="varname">adberr</code></p>
1889                   </td>
1890 <td>
1891                     <p>
1892                       Failures in finding remote server addresses
1893                       of the <code class="varname">domain</code> zone in the ADB.
1894                       One common case of this is that the remote
1895                       server's name does not have any address records.
1896                     </p>
1897                   </td>
1898 </tr>
1899 <tr>
1900 <td>
1901                     <p><code class="varname">findfail</code></p>
1902                   </td>
1903 <td>
1904                     <p>
1905                       Failures of resolving remote server addresses.
1906                       This is a total number of failures throughout
1907                       the resolution process.
1908                     </p>
1909                   </td>
1910 </tr>
1911 <tr>
1912 <td>
1913                     <p><code class="varname">valfail</code></p>
1914                   </td>
1915 <td>
1916                     <p>
1917                       Failures of DNSSEC validation.
1918                       Validation failures are counted throughout
1919                       the resolution process (not limited to
1920                       the <code class="varname">domain</code> zone), but should
1921                       only happen in <code class="varname">domain</code>.
1922                     </p>
1923                   </td>
1924 </tr>
1925 </tbody>
1926 </table></div>
1927 <p>
1928             At the debug levels of 3 or higher, the same messages
1929             as those at the debug 1 level are logged for other errors
1930             than SERVFAIL.
1931             Note that negative responses such as NXDOMAIN are not
1932             regarded as errors here.
1933           </p>
1934 <p>
1935             At the debug levels of 4 or higher, the same messages
1936             as those at the debug 2 level are logged for other errors
1937             than SERVFAIL.
1938             Unlike the above case of level 3, messages are logged for
1939             negative responses.
1940             This is because any unexpected results can be difficult to
1941             debug in the recursion case.
1942           </p>
1943 </div>
1944 </div>
1945 <div class="sect2" lang="en">
1946 <div class="titlepage"><div><div><h3 class="title">
1947 <a name="id2577306"></a><span><strong class="command">lwres</strong></span> Statement Grammar</h3></div></div></div>
1948 <p>
1949            This is the grammar of the <span><strong class="command">lwres</strong></span>
1950           statement in the <code class="filename">named.conf</code> file:
1951         </p>
1952 <pre class="programlisting"><span><strong class="command">lwres</strong></span> {
1953     [<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>]
1954     [<span class="optional"> view <em class="replaceable"><code>view_name</code></em>; </span>]
1955     [<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>]
1956     [<span class="optional"> ndots <em class="replaceable"><code>number</code></em>; </span>]
1957 };
1958 </pre>
1959 </div>
1960 <div class="sect2" lang="en">
1961 <div class="titlepage"><div><div><h3 class="title">
1962 <a name="id2577448"></a><span><strong class="command">lwres</strong></span> Statement Definition and Usage</h3></div></div></div>
1963 <p>
1964           The <span><strong class="command">lwres</strong></span> statement configures the
1965           name
1966           server to also act as a lightweight resolver server. (See
1967           <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
1968           <span><strong class="command">lwres</strong></span> statements configuring
1969           lightweight resolver servers with different properties.
1970         </p>
1971 <p>
1972           The <span><strong class="command">listen-on</strong></span> statement specifies a
1973           list of
1974           addresses (and ports) that this instance of a lightweight resolver
1975           daemon
1976           should accept requests on.  If no port is specified, port 921 is
1977           used.
1978           If this statement is omitted, requests will be accepted on
1979           127.0.0.1,
1980           port 921.
1981         </p>
1982 <p>
1983           The <span><strong class="command">view</strong></span> statement binds this
1984           instance of a
1985           lightweight resolver daemon to a view in the DNS namespace, so that
1986           the
1987           response will be constructed in the same manner as a normal DNS
1988           query
1989           matching this view.  If this statement is omitted, the default view
1990           is
1991           used, and if there is no default view, an error is triggered.
1992         </p>
1993 <p>
1994           The <span><strong class="command">search</strong></span> statement is equivalent to
1995           the
1996           <span><strong class="command">search</strong></span> statement in
1997           <code class="filename">/etc/resolv.conf</code>.  It provides a
1998           list of domains
1999           which are appended to relative names in queries.
2000         </p>
2001 <p>
2002           The <span><strong class="command">ndots</strong></span> statement is equivalent to
2003           the
2004           <span><strong class="command">ndots</strong></span> statement in
2005           <code class="filename">/etc/resolv.conf</code>.  It indicates the
2006           minimum
2007           number of dots in a relative domain name that should result in an
2008           exact match lookup before search path elements are appended.
2009         </p>
2010 </div>
2011 <div class="sect2" lang="en">
2012 <div class="titlepage"><div><div><h3 class="title">
2013 <a name="id2577512"></a><span><strong class="command">masters</strong></span> Statement Grammar</h3></div></div></div>
2014 <pre class="programlisting">
2015 <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>] };
2016 </pre>
2017 </div>
2018 <div class="sect2" lang="en">
2019 <div class="titlepage"><div><div><h3 class="title">
2020 <a name="id2577556"></a><span><strong class="command">masters</strong></span> Statement Definition and
2021           Usage</h3></div></div></div>
2022 <p><span><strong class="command">masters</strong></span>
2023           lists allow for a common set of masters to be easily used by
2024           multiple stub and slave zones.
2025         </p>
2026 </div>
2027 <div class="sect2" lang="en">
2028 <div class="titlepage"><div><div><h3 class="title">
2029 <a name="id2577571"></a><span><strong class="command">options</strong></span> Statement Grammar</h3></div></div></div>
2030 <p>
2031           This is the grammar of the <span><strong class="command">options</strong></span>
2032           statement in the <code class="filename">named.conf</code> file:
2033         </p>
2034 <pre class="programlisting"><span><strong class="command">options</strong></span> {
2035     [<span class="optional"> version <em class="replaceable"><code>version_string</code></em>; </span>]
2036     [<span class="optional"> hostname <em class="replaceable"><code>hostname_string</code></em>; </span>]
2037     [<span class="optional"> server-id <em class="replaceable"><code>server_id_string</code></em>; </span>]
2038     [<span class="optional"> directory <em class="replaceable"><code>path_name</code></em>; </span>]
2039     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2040     [<span class="optional"> named-xfer <em class="replaceable"><code>path_name</code></em>; </span>]
2041     [<span class="optional"> tkey-gssapi-credential <em class="replaceable"><code>principal</code></em>; </span>]
2042     [<span class="optional"> tkey-domain <em class="replaceable"><code>domainname</code></em>; </span>]
2043     [<span class="optional"> tkey-dhkey <em class="replaceable"><code>key_name</code></em> <em class="replaceable"><code>key_tag</code></em>; </span>]
2044     [<span class="optional"> cache-file <em class="replaceable"><code>path_name</code></em>; </span>]
2045     [<span class="optional"> dump-file <em class="replaceable"><code>path_name</code></em>; </span>]
2046     [<span class="optional"> memstatistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2047     [<span class="optional"> memstatistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2048     [<span class="optional"> pid-file <em class="replaceable"><code>path_name</code></em>; </span>]
2049     [<span class="optional"> recursing-file <em class="replaceable"><code>path_name</code></em>; </span>]
2050     [<span class="optional"> statistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2051     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2052     [<span class="optional"> auth-nxdomain <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2053     [<span class="optional"> deallocate-on-exit <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2054     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em>; </span>]
2055     [<span class="optional"> fake-iquery <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2056     [<span class="optional"> fetch-glue <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2057     [<span class="optional"> flush-zones-on-shutdown <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2058     [<span class="optional"> has-old-clients <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2059     [<span class="optional"> host-statistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2060     [<span class="optional"> host-statistics-max <em class="replaceable"><code>number</code></em>; </span>]
2061     [<span class="optional"> minimal-responses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2062     [<span class="optional"> multiple-cnames <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2063     [<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>]
2064     [<span class="optional"> recursion <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2065     [<span class="optional"> rfc2308-type1 <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2066     [<span class="optional"> use-id-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2067     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2068     [<span class="optional"> ixfr-from-differences (<em class="replaceable"><code>yes_or_no</code></em> | <code class="constant">master</code> | <code class="constant">slave</code>); </span>]
2069     [<span class="optional"> dnssec-enable <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2070     [<span class="optional"> dnssec-validation <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2071     [<span class="optional"> dnssec-lookaside <em class="replaceable"><code>domain</code></em> trust-anchor <em class="replaceable"><code>domain</code></em>; </span>]
2072     [<span class="optional"> dnssec-must-be-secure <em class="replaceable"><code>domain yes_or_no</code></em>; </span>]
2073     [<span class="optional"> dnssec-accept-expired <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2074     [<span class="optional"> forward ( <em class="replaceable"><code>only</code></em> | <em class="replaceable"><code>first</code></em> ); </span>]
2075     [<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>]
2076     [<span class="optional"> dual-stack-servers [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] {
2077         ( <em class="replaceable"><code>domain_name</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] |
2078           <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ) ;
2079         ... }; </span>]
2080     [<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> )
2081         ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2082     [<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>]
2083     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2084     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2085     [<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>]
2086     [<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>]
2087     [<span class="optional"> check-sibling <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2088     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2089     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2090     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2091     [<span class="optional"> allow-query-cache { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2092     [<span class="optional"> allow-query-cache-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2093     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2094     [<span class="optional"> allow-recursion { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2095     [<span class="optional"> allow-recursion-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2096     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2097     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2098     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2099     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2100     [<span class="optional"> allow-v6-synthesis { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2101     [<span class="optional"> blackhole { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2102     [<span class="optional"> use-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2103     [<span class="optional"> avoid-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2104     [<span class="optional"> use-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2105     [<span class="optional"> avoid-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2106     [<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>]
2107     [<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>]
2108     [<span class="optional"> query-source ( ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2109         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
2110         [<span class="optional"> address ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2111         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
2112     [<span class="optional"> query-source-v6 ( ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2113         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
2114         [<span class="optional"> address ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2115         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
2116     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2117     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
2118     [<span class="optional"> queryport-pool-interval <em class="replaceable"><code>number</code></em>; </span>]
2119     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em>; </span>]
2120     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em>; </span>]
2121     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em>; </span>]
2122     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em>; </span>]
2123     [<span class="optional"> tcp-clients <em class="replaceable"><code>number</code></em>; </span>]
2124     [<span class="optional"> reserved-sockets <em class="replaceable"><code>number</code></em>; </span>]
2125     [<span class="optional"> recursive-clients <em class="replaceable"><code>number</code></em>; </span>]
2126     [<span class="optional"> serial-query-rate <em class="replaceable"><code>number</code></em>; </span>]
2127     [<span class="optional"> serial-queries <em class="replaceable"><code>number</code></em>; </span>]
2128     [<span class="optional"> tcp-listen-queue <em class="replaceable"><code>number</code></em>; </span>]
2129     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em>; </span>]
2130     [<span class="optional"> transfers-in  <em class="replaceable"><code>number</code></em>; </span>]
2131     [<span class="optional"> transfers-out <em class="replaceable"><code>number</code></em>; </span>]
2132     [<span class="optional"> transfers-per-ns <em class="replaceable"><code>number</code></em>; </span>]
2133     [<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>]
2134     [<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>]
2135     [<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>]
2136     [<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>]
2137     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2138     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
2139     [<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>]
2140     [<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>]
2141     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2142     [<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>]
2143     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em>; </span>]
2144     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
2145     [<span class="optional"> coresize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2146     [<span class="optional"> datasize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2147     [<span class="optional"> files <em class="replaceable"><code>size_spec</code></em> ; </span>]
2148     [<span class="optional"> stacksize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2149     [<span class="optional"> cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2150     [<span class="optional"> heartbeat-interval <em class="replaceable"><code>number</code></em>; </span>]
2151     [<span class="optional"> interface-interval <em class="replaceable"><code>number</code></em>; </span>]
2152     [<span class="optional"> statistics-interval <em class="replaceable"><code>number</code></em>; </span>]
2153     [<span class="optional"> topology { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2154     [<span class="optional"> sortlist { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2155     [<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>] };
2156     [<span class="optional"> lame-ttl <em class="replaceable"><code>number</code></em>; </span>]
2157     [<span class="optional"> max-ncache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2158     [<span class="optional"> max-cache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2159     [<span class="optional"> sig-validity-interval <em class="replaceable"><code>number</code></em> ; </span>]
2160     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
2161     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
2162     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
2163     [<span class="optional"> min-roots <em class="replaceable"><code>number</code></em>; </span>]
2164     [<span class="optional"> use-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2165     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2166     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2167     [<span class="optional"> treat-cr-as-space <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2168     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2169     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2170     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2171     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2172     [<span class="optional"> port <em class="replaceable"><code>ip_port</code></em>; </span>]
2173     [<span class="optional"> additional-from-auth <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2174     [<span class="optional"> additional-from-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2175     [<span class="optional"> random-device <em class="replaceable"><code>path_name</code></em> ; </span>]
2176     [<span class="optional"> max-cache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2177     [<span class="optional"> match-mapped-addresses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2178     [<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>]
2179     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2180     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2181     [<span class="optional"> root-delegation-only [<span class="optional"> exclude { <em class="replaceable"><code>namelist</code></em> } </span>] ; </span>]
2182     [<span class="optional"> querylog <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2183     [<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>]
2184     [<span class="optional"> acache-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2185     [<span class="optional"> acache-cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2186     [<span class="optional"> max-acache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2187     [<span class="optional"> clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2188     [<span class="optional"> max-clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2189     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
2190     [<span class="optional"> empty-server <em class="replaceable"><code>name</code></em> ; </span>]
2191     [<span class="optional"> empty-contact <em class="replaceable"><code>name</code></em> ; </span>]
2192     [<span class="optional"> empty-zones-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2193     [<span class="optional"> disable-empty-zone <em class="replaceable"><code>zone_name</code></em> ; </span>]
2194     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2195     [<span class="optional"> zero-no-soa-ttl-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2196 };
2197 </pre>
2198 </div>
2199 <div class="sect2" lang="en">
2200 <div class="titlepage"><div><div><h3 class="title">
2201 <a name="options"></a><span><strong class="command">options</strong></span> Statement Definition and
2202           Usage</h3></div></div></div>
2203 <p>
2204           The <span><strong class="command">options</strong></span> statement sets up global
2205           options
2206           to be used by <acronym class="acronym">BIND</acronym>. This statement
2207           may appear only
2208           once in a configuration file. If there is no <span><strong class="command">options</strong></span>
2209           statement, an options block with each option set to its default will
2210           be used.
2211         </p>
2212 <div class="variablelist"><dl>
2213 <dt><span class="term"><span><strong class="command">directory</strong></span></span></dt>
2214 <dd><p>
2215                 The working directory of the server.
2216                 Any non-absolute pathnames in the configuration file will be
2217                 taken
2218                 as relative to this directory. The default location for most
2219                 server
2220                 output files (e.g. <code class="filename">named.run</code>)
2221                 is this directory.
2222                 If a directory is not specified, the working directory
2223                 defaults to `<code class="filename">.</code>', the directory from
2224                 which the server
2225                 was started. The directory specified should be an absolute
2226                 path.
2227               </p></dd>
2228 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
2229 <dd><p>
2230                 When performing dynamic update of secure zones, the
2231                 directory where the public and private key files should be
2232                 found,
2233                 if different than the current working directory.  The
2234                 directory specified
2235                 must be an absolute path.
2236               </p></dd>
2237 <dt><span class="term"><span><strong class="command">named-xfer</strong></span></span></dt>
2238 <dd><p>
2239                 <span class="emphasis"><em>This option is obsolete.</em></span> It
2240                 was used in <acronym class="acronym">BIND</acronym> 8 to specify
2241                 the pathname to the <span><strong class="command">named-xfer</strong></span>
2242                 program.  In <acronym class="acronym">BIND</acronym> 9, no separate
2243                 <span><strong class="command">named-xfer</strong></span> program is needed;
2244                 its functionality is built into the name server.
2245               </p></dd>
2246 <dt><span class="term"><span><strong class="command">tkey-gssapi-credential</strong></span></span></dt>
2247 <dd><p>
2248                 The security credential with which the server should
2249                 authenticate keys requested by the GSS-TSIG protocol.
2250                 Currently only Kerberos 5 authentication is available
2251                 and the credential is a Kerberos principal which
2252                 the server can acquire through the default system
2253                 key file, normally <code class="filename">/etc/krb5.keytab</code>.
2254                 Normally this principal is of the form
2255                 "<strong class="userinput"><code>dns/</code></strong><code class="varname">server.domain</code>".
2256                 To use GSS-TSIG, <span><strong class="command">tkey-domain</strong></span>
2257                 must also be set.
2258               </p></dd>
2259 <dt><span class="term"><span><strong class="command">tkey-domain</strong></span></span></dt>
2260 <dd><p>
2261                 The domain appended to the names of all shared keys
2262                 generated with <span><strong class="command">TKEY</strong></span>.  When a
2263                 client requests a <span><strong class="command">TKEY</strong></span> exchange,
2264                 it may or may not specify the desired name for the
2265                 key. If present, the name of the shared key will
2266                 be <code class="varname">client specified part</code> +
2267                 <code class="varname">tkey-domain</code>.  Otherwise, the
2268                 name of the shared key will be <code class="varname">random hex
2269                 digits</code> + <code class="varname">tkey-domain</code>.
2270                 In most cases, the <span><strong class="command">domainname</strong></span>
2271                 should be the server's domain name, or an otherwise
2272                 non-existent subdomain like
2273                 "_tkey.<code class="varname">domainname</code>".  If you are
2274                 using GSS-TSIG, this variable must be defined.
2275               </p></dd>
2276 <dt><span class="term"><span><strong class="command">tkey-dhkey</strong></span></span></dt>
2277 <dd><p>
2278                 The Diffie-Hellman key used by the server
2279                 to generate shared keys with clients using the Diffie-Hellman
2280                 mode
2281                 of <span><strong class="command">TKEY</strong></span>. The server must be
2282                 able to load the
2283                 public and private keys from files in the working directory.
2284                 In
2285                 most cases, the keyname should be the server's host name.
2286               </p></dd>
2287 <dt><span class="term"><span><strong class="command">cache-file</strong></span></span></dt>
2288 <dd><p>
2289                 This is for testing only.  Do not use.
2290               </p></dd>
2291 <dt><span class="term"><span><strong class="command">dump-file</strong></span></span></dt>
2292 <dd><p>
2293                 The pathname of the file the server dumps
2294                 the database to when instructed to do so with
2295                 <span><strong class="command">rndc dumpdb</strong></span>.
2296                 If not specified, the default is <code class="filename">named_dump.db</code>.
2297               </p></dd>
2298 <dt><span class="term"><span><strong class="command">memstatistics-file</strong></span></span></dt>
2299 <dd><p>
2300                 The pathname of the file the server writes memory
2301                 usage statistics to on exit. If not specified,
2302                 the default is <code class="filename">named.memstats</code>.
2303               </p></dd>
2304 <dt><span class="term"><span><strong class="command">pid-file</strong></span></span></dt>
2305 <dd><p>
2306                 The pathname of the file the server writes its process ID
2307                 in. If not specified, the default is
2308                 <code class="filename">/var/run/named/named.pid</code>.
2309                 The PID file is used by programs that want to send signals to
2310                 the running
2311                 name server. Specifying <span><strong class="command">pid-file none</strong></span> disables the
2312                 use of a PID file &#8212; no file will be written and any
2313                 existing one will be removed.  Note that <span><strong class="command">none</strong></span>
2314                 is a keyword, not a filename, and therefore is not enclosed
2315                 in
2316                 double quotes.
2317               </p></dd>
2318 <dt><span class="term"><span><strong class="command">recursing-file</strong></span></span></dt>
2319 <dd><p>
2320                 The pathname of the file the server dumps
2321                 the queries that are currently recursing when instructed
2322                 to do so with <span><strong class="command">rndc recursing</strong></span>.
2323                 If not specified, the default is <code class="filename">named.recursing</code>.
2324               </p></dd>
2325 <dt><span class="term"><span><strong class="command">statistics-file</strong></span></span></dt>
2326 <dd><p>
2327                 The pathname of the file the server appends statistics
2328                 to when instructed to do so using <span><strong class="command">rndc stats</strong></span>.
2329                 If not specified, the default is <code class="filename">named.stats</code> in the
2330                 server's current directory.  The format of the file is
2331                 described
2332                 in <a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
2333               </p></dd>
2334 <dt><span class="term"><span><strong class="command">port</strong></span></span></dt>
2335 <dd><p>
2336                 The UDP/TCP port number the server uses for
2337                 receiving and sending DNS protocol traffic.
2338                 The default is 53.  This option is mainly intended for server
2339                 testing;
2340                 a server using a port other than 53 will not be able to
2341                 communicate with
2342                 the global DNS.
2343               </p></dd>
2344 <dt><span class="term"><span><strong class="command">random-device</strong></span></span></dt>
2345 <dd><p>
2346                 The source of entropy to be used by the server.  Entropy is
2347                 primarily needed
2348                 for DNSSEC operations, such as TKEY transactions and dynamic
2349                 update of signed
2350                 zones.  This options specifies the device (or file) from which
2351                 to read
2352                 entropy.  If this is a file, operations requiring entropy will
2353                 fail when the
2354                 file has been exhausted.  If not specified, the default value
2355                 is
2356                 <code class="filename">/dev/random</code>
2357                 (or equivalent) when present, and none otherwise.  The
2358                 <span><strong class="command">random-device</strong></span> option takes
2359                 effect during
2360                 the initial configuration load at server startup time and
2361                 is ignored on subsequent reloads.
2362               </p></dd>
2363 <dt><span class="term"><span><strong class="command">preferred-glue</strong></span></span></dt>
2364 <dd><p>
2365                 If specified, the listed type (A or AAAA) will be emitted
2366                 before other glue
2367                 in the additional section of a query response.
2368                 The default is not to prefer any type (NONE).
2369               </p></dd>
2370 <dt>
2371 <a name="root_delegation_only"></a><span class="term"><span><strong class="command">root-delegation-only</strong></span></span>
2372 </dt>
2373 <dd>
2374 <p>
2375                 Turn on enforcement of delegation-only in TLDs
2376                 (top level domains) and root zones with an optional
2377                 exclude list.
2378               </p>
2379 <p>
2380                 DS queries are expected to be made to and be answered by
2381                 delegation only zones.  Such queries and responses are
2382                 treated as a exception to delegation-only processing
2383                 and are not converted to NXDOMAIN responses provided
2384                 a CNAME is not discovered at the query name.
2385               </p>
2386 <p>
2387                 If a delegation only zone server also serves a child
2388                 zone it is not always possible to determine whether
2389                 a answer comes from the delegation only zone or the
2390                 child zone.  SOA NS and DNSKEY records are apex
2391                 only records and a matching response that contains
2392                 these records or DS is treated as coming from a
2393                 child zone.  RRSIG records are also examined to see
2394                 if they are signed by a child zone or not.  The
2395                 authority section is also examined to see if there
2396                 is evidence that the answer is from the child zone.
2397                 Answers that are determined to be from a child zone
2398                 are not converted to NXDOMAIN responses.  Despite
2399                 all these checks there is still a possibility of
2400                 false negatives when a child zone is being served.
2401               </p>
2402 <p>
2403                 Similarly false positives can arise from empty nodes
2404                 (no records at the name) in the delegation only zone
2405                 when the query type is not ANY.
2406               </p>
2407 <p>
2408                 Note some TLDs are not delegation only (e.g. "DE", "LV",
2409                 "US" and "MUSEUM").  This list is not exhaustive.
2410               </p>
2411 <pre class="programlisting">
2412 options {
2413         root-delegation-only exclude { "de"; "lv"; "us"; "museum"; };
2414 };
2415 </pre>
2416 </dd>
2417 <dt><span class="term"><span><strong class="command">disable-algorithms</strong></span></span></dt>
2418 <dd><p>
2419                 Disable the specified DNSSEC algorithms at and below the
2420                 specified name.
2421                 Multiple <span><strong class="command">disable-algorithms</strong></span>
2422                 statements are allowed.
2423                 Only the most specific will be applied.
2424               </p></dd>
2425 <dt><span class="term"><span><strong class="command">dnssec-lookaside</strong></span></span></dt>
2426 <dd><p>
2427                 When set, <span><strong class="command">dnssec-lookaside</strong></span>
2428                 provides the
2429                 validator with an alternate method to validate DNSKEY records
2430                 at the
2431                 top of a zone.  When a DNSKEY is at or below a domain
2432                 specified by the
2433                 deepest <span><strong class="command">dnssec-lookaside</strong></span>, and
2434                 the normal DNSSEC validation
2435                 has left the key untrusted, the trust-anchor will be append to
2436                 the key
2437                 name and a DLV record will be looked up to see if it can
2438                 validate the
2439                 key.  If the DLV record validates a DNSKEY (similarly to the
2440                 way a DS
2441                 record does) the DNSKEY RRset is deemed to be trusted.
2442               </p></dd>
2443 <dt><span class="term"><span><strong class="command">dnssec-must-be-secure</strong></span></span></dt>
2444 <dd><p>
2445                 Specify hierarchies which must be or may not be secure (signed and
2446                 validated).
2447                 If <strong class="userinput"><code>yes</code></strong>, then <span><strong class="command">named</strong></span> will only accept
2448                 answers if they
2449                 are secure.
2450                 If <strong class="userinput"><code>no</code></strong>, then normal DNSSEC validation
2451                 applies
2452                 allowing for insecure answers to be accepted.
2453                 The specified domain must be under a <span><strong class="command">trusted-key</strong></span> or
2454                 <span><strong class="command">dnssec-lookaside</strong></span> must be
2455                 active.
2456               </p></dd>
2457 </dl></div>
2458 <div class="sect3" lang="en">
2459 <div class="titlepage"><div><div><h4 class="title">
2460 <a name="boolean_options"></a>Boolean Options</h4></div></div></div>
2461 <div class="variablelist"><dl>
2462 <dt><span class="term"><span><strong class="command">auth-nxdomain</strong></span></span></dt>
2463 <dd><p>
2464                   If <strong class="userinput"><code>yes</code></strong>, then the <span><strong class="command">AA</strong></span> bit
2465                   is always set on NXDOMAIN responses, even if the server is
2466                   not actually
2467                   authoritative. The default is <strong class="userinput"><code>no</code></strong>;
2468                   this is
2469                   a change from <acronym class="acronym">BIND</acronym> 8. If you
2470                   are using very old DNS software, you
2471                   may need to set it to <strong class="userinput"><code>yes</code></strong>.
2472                 </p></dd>
2473 <dt><span class="term"><span><strong class="command">deallocate-on-exit</strong></span></span></dt>
2474 <dd><p>
2475                   This option was used in <acronym class="acronym">BIND</acronym>
2476                   8 to enable checking
2477                   for memory leaks on exit. <acronym class="acronym">BIND</acronym> 9 ignores the option and always performs
2478                   the checks.
2479                 </p></dd>
2480 <dt><span class="term"><span><strong class="command">memstatistics</strong></span></span></dt>
2481 <dd><p>
2482                   Write memory statistics to the file specified by
2483                   <span><strong class="command">memstatistics-file</strong></span> at exit.
2484                   The default is <strong class="userinput"><code>no</code></strong> unless
2485                   '-m record' is specified on the command line in
2486                   which case it is <strong class="userinput"><code>yes</code></strong>.
2487                 </p></dd>
2488 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
2489 <dd>
2490 <p>
2491                   If <strong class="userinput"><code>yes</code></strong>, then the
2492                   server treats all zones as if they are doing zone transfers
2493                   across
2494                   a dial-on-demand dialup link, which can be brought up by
2495                   traffic
2496                   originating from this server. This has different effects
2497                   according
2498                   to zone type and concentrates the zone maintenance so that
2499                   it all
2500                   happens in a short interval, once every <span><strong class="command">heartbeat-interval</strong></span> and
2501                   hopefully during the one call. It also suppresses some of
2502                   the normal
2503                   zone maintenance traffic. The default is <strong class="userinput"><code>no</code></strong>.
2504                 </p>
2505 <p>
2506                   The <span><strong class="command">dialup</strong></span> option
2507                   may also be specified in the <span><strong class="command">view</strong></span> and
2508                   <span><strong class="command">zone</strong></span> statements,
2509                   in which case it overrides the global <span><strong class="command">dialup</strong></span>
2510                   option.
2511                 </p>
2512 <p>
2513                   If the zone is a master zone, then the server will send out a
2514                   NOTIFY
2515                   request to all the slaves (default). This should trigger the
2516                   zone serial
2517                   number check in the slave (providing it supports NOTIFY)
2518                   allowing the slave
2519                   to verify the zone while the connection is active.
2520                   The set of servers to which NOTIFY is sent can be controlled
2521                   by
2522                   <span><strong class="command">notify</strong></span> and <span><strong class="command">also-notify</strong></span>.
2523                 </p>
2524 <p>
2525                   If the
2526                   zone is a slave or stub zone, then the server will suppress
2527                   the regular
2528                   "zone up to date" (refresh) queries and only perform them
2529                   when the
2530                   <span><strong class="command">heartbeat-interval</strong></span> expires in
2531                   addition to sending
2532                   NOTIFY requests.
2533                 </p>
2534 <p>
2535                   Finer control can be achieved by using
2536                   <strong class="userinput"><code>notify</code></strong> which only sends NOTIFY
2537                   messages,
2538                   <strong class="userinput"><code>notify-passive</code></strong> which sends NOTIFY
2539                   messages and
2540                   suppresses the normal refresh queries, <strong class="userinput"><code>refresh</code></strong>
2541                   which suppresses normal refresh processing and sends refresh
2542                   queries
2543                   when the <span><strong class="command">heartbeat-interval</strong></span>
2544                   expires, and
2545                   <strong class="userinput"><code>passive</code></strong> which just disables normal
2546                   refresh
2547                   processing.
2548                 </p>
2549 <div class="informaltable"><table border="1">
2550 <colgroup>
2551 <col>
2552 <col>
2553 <col>
2554 <col>
2555 </colgroup>
2556 <tbody>
2557 <tr>
2558 <td>
2559                           <p>
2560                             dialup mode
2561                           </p>
2562                         </td>
2563 <td>
2564                           <p>
2565                             normal refresh
2566                           </p>
2567                         </td>
2568 <td>
2569                           <p>
2570                             heart-beat refresh
2571                           </p>
2572                         </td>
2573 <td>
2574                           <p>
2575                             heart-beat notify
2576                           </p>
2577                         </td>
2578 </tr>
2579 <tr>
2580 <td>
2581                           <p><span><strong class="command">no</strong></span> (default)</p>
2582                         </td>
2583 <td>
2584                           <p>
2585                             yes
2586                           </p>
2587                         </td>
2588 <td>
2589                           <p>
2590                             no
2591                           </p>
2592                         </td>
2593 <td>
2594                           <p>
2595                             no
2596                           </p>
2597                         </td>
2598 </tr>
2599 <tr>
2600 <td>
2601                           <p><span><strong class="command">yes</strong></span></p>
2602                         </td>
2603 <td>
2604                           <p>
2605                             no
2606                           </p>
2607                         </td>
2608 <td>
2609                           <p>
2610                             yes
2611                           </p>
2612                         </td>
2613 <td>
2614                           <p>
2615                             yes
2616                           </p>
2617                         </td>
2618 </tr>
2619 <tr>
2620 <td>
2621                           <p><span><strong class="command">notify</strong></span></p>
2622                         </td>
2623 <td>
2624                           <p>
2625                             yes
2626                           </p>
2627                         </td>
2628 <td>
2629                           <p>
2630                             no
2631                           </p>
2632                         </td>
2633 <td>
2634                           <p>
2635                             yes
2636                           </p>
2637                         </td>
2638 </tr>
2639 <tr>
2640 <td>
2641                           <p><span><strong class="command">refresh</strong></span></p>
2642                         </td>
2643 <td>
2644                           <p>
2645                             no
2646                           </p>
2647                         </td>
2648 <td>
2649                           <p>
2650                             yes
2651                           </p>
2652                         </td>
2653 <td>
2654                           <p>
2655                             no
2656                           </p>
2657                         </td>
2658 </tr>
2659 <tr>
2660 <td>
2661                           <p><span><strong class="command">passive</strong></span></p>
2662                         </td>
2663 <td>
2664                           <p>
2665                             no
2666                           </p>
2667                         </td>
2668 <td>
2669                           <p>
2670                             no
2671                           </p>
2672                         </td>
2673 <td>
2674                           <p>
2675                             no
2676                           </p>
2677                         </td>
2678 </tr>
2679 <tr>
2680 <td>
2681                           <p><span><strong class="command">notify-passive</strong></span></p>
2682                         </td>
2683 <td>
2684                           <p>
2685                             no
2686                           </p>
2687                         </td>
2688 <td>
2689                           <p>
2690                             no
2691                           </p>
2692                         </td>
2693 <td>
2694                           <p>
2695                             yes
2696                           </p>
2697                         </td>
2698 </tr>
2699 </tbody>
2700 </table></div>
2701 <p>
2702                   Note that normal NOTIFY processing is not affected by
2703                   <span><strong class="command">dialup</strong></span>.
2704                 </p>
2705 </dd>
2706 <dt><span class="term"><span><strong class="command">fake-iquery</strong></span></span></dt>
2707 <dd><p>
2708                   In <acronym class="acronym">BIND</acronym> 8, this option
2709                   enabled simulating the obsolete DNS query type
2710                   IQUERY. <acronym class="acronym">BIND</acronym> 9 never does
2711                   IQUERY simulation.
2712                 </p></dd>
2713 <dt><span class="term"><span><strong class="command">fetch-glue</strong></span></span></dt>
2714 <dd><p>
2715                   This option is obsolete.
2716                   In BIND 8, <strong class="userinput"><code>fetch-glue yes</code></strong>
2717                   caused the server to attempt to fetch glue resource records
2718                   it
2719                   didn't have when constructing the additional
2720                   data section of a response.  This is now considered a bad
2721                   idea
2722                   and BIND 9 never does it.
2723                 </p></dd>
2724 <dt><span class="term"><span><strong class="command">flush-zones-on-shutdown</strong></span></span></dt>
2725 <dd><p>
2726                   When the nameserver exits due receiving SIGTERM,
2727                   flush or do not flush any pending zone writes.  The default
2728                   is
2729                   <span><strong class="command">flush-zones-on-shutdown</strong></span> <strong class="userinput"><code>no</code></strong>.
2730                 </p></dd>
2731 <dt><span class="term"><span><strong class="command">has-old-clients</strong></span></span></dt>
2732 <dd><p>
2733                   This option was incorrectly implemented
2734                   in <acronym class="acronym">BIND</acronym> 8, and is ignored by <acronym class="acronym">BIND</acronym> 9.
2735                   To achieve the intended effect
2736                   of
2737                   <span><strong class="command">has-old-clients</strong></span> <strong class="userinput"><code>yes</code></strong>, specify
2738                   the two separate options <span><strong class="command">auth-nxdomain</strong></span> <strong class="userinput"><code>yes</code></strong>
2739                   and <span><strong class="command">rfc2308-type1</strong></span> <strong class="userinput"><code>no</code></strong> instead.
2740                 </p></dd>
2741 <dt><span class="term"><span><strong class="command">host-statistics</strong></span></span></dt>
2742 <dd><p>
2743                   In BIND 8, this enables keeping of
2744                   statistics for every host that the name server interacts
2745                   with.
2746                   Not implemented in BIND 9.
2747                 </p></dd>
2748 <dt><span class="term"><span><strong class="command">maintain-ixfr-base</strong></span></span></dt>
2749 <dd><p>
2750                   <span class="emphasis"><em>This option is obsolete</em></span>.
2751                   It was used in <acronym class="acronym">BIND</acronym> 8 to
2752                   determine whether a transaction log was
2753                   kept for Incremental Zone Transfer. <acronym class="acronym">BIND</acronym> 9 maintains a transaction
2754                   log whenever possible.  If you need to disable outgoing
2755                   incremental zone
2756                   transfers, use <span><strong class="command">provide-ixfr</strong></span> <strong class="userinput"><code>no</code></strong>.
2757                 </p></dd>
2758 <dt><span class="term"><span><strong class="command">minimal-responses</strong></span></span></dt>
2759 <dd><p>
2760                   If <strong class="userinput"><code>yes</code></strong>, then when generating
2761                   responses the server will only add records to the authority
2762                   and additional data sections when they are required (e.g.
2763                   delegations, negative responses).  This may improve the
2764                   performance of the server.
2765                   The default is <strong class="userinput"><code>no</code></strong>.
2766                 </p></dd>
2767 <dt><span class="term"><span><strong class="command">multiple-cnames</strong></span></span></dt>
2768 <dd><p>
2769                   This option was used in <acronym class="acronym">BIND</acronym> 8 to allow
2770                   a domain name to have multiple CNAME records in violation of
2771                   the DNS standards.  <acronym class="acronym">BIND</acronym> 9.2 onwards
2772                   always strictly enforces the CNAME rules both in master
2773                   files and dynamic updates.
2774                 </p></dd>
2775 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
2776 <dd>
2777 <p>
2778                   If <strong class="userinput"><code>yes</code></strong> (the default),
2779                   DNS NOTIFY messages are sent when a zone the server is
2780                   authoritative for
2781                   changes, see <a href="Bv9ARM.ch04.html#notify" title="Notify">the section called &#8220;Notify&#8221;</a>.  The messages are
2782                   sent to the
2783                   servers listed in the zone's NS records (except the master
2784                   server identified
2785                   in the SOA MNAME field), and to any servers listed in the
2786                   <span><strong class="command">also-notify</strong></span> option.
2787                 </p>
2788 <p>
2789                   If <strong class="userinput"><code>master-only</code></strong>, notifies are only
2790                   sent
2791                   for master zones.
2792                   If <strong class="userinput"><code>explicit</code></strong>, notifies are sent only
2793                   to
2794                   servers explicitly listed using <span><strong class="command">also-notify</strong></span>.
2795                   If <strong class="userinput"><code>no</code></strong>, no notifies are sent.
2796                 </p>
2797 <p>
2798                   The <span><strong class="command">notify</strong></span> option may also be
2799                   specified in the <span><strong class="command">zone</strong></span>
2800                   statement,
2801                   in which case it overrides the <span><strong class="command">options notify</strong></span> statement.
2802                   It would only be necessary to turn off this option if it
2803                   caused slaves
2804                   to crash.
2805                 </p>
2806 </dd>
2807 <dt><span class="term"><span><strong class="command">notify-to-soa</strong></span></span></dt>
2808 <dd><p>
2809                   If <strong class="userinput"><code>yes</code></strong> do not check the nameservers
2810                   in the NS RRset against the SOA MNAME.  Normally a NOTIFY
2811                   message is not sent to the SOA MNAME (SOA ORIGIN) as it is
2812                   supposed to contain the name of the ultimate master.
2813                   Sometimes, however, a slave is listed as the SOA MNAME in
2814                   hidden master configurations and in that case you would
2815                   want the ultimate master to still send NOTIFY messages to
2816                   all the nameservers listed in the NS RRset.
2817                 </p></dd>
2818 <dt><span class="term"><span><strong class="command">recursion</strong></span></span></dt>
2819 <dd><p>
2820                   If <strong class="userinput"><code>yes</code></strong>, and a
2821                   DNS query requests recursion, then the server will attempt
2822                   to do
2823                   all the work required to answer the query. If recursion is
2824                   off
2825                   and the server does not already know the answer, it will
2826                   return a
2827                   referral response. The default is
2828                   <strong class="userinput"><code>yes</code></strong>.
2829                   Note that setting <span><strong class="command">recursion no</strong></span> does not prevent
2830                   clients from getting data from the server's cache; it only
2831                   prevents new data from being cached as an effect of client
2832                   queries.
2833                   Caching may still occur as an effect the server's internal
2834                   operation, such as NOTIFY address lookups.
2835                   See also <span><strong class="command">fetch-glue</strong></span> above.
2836                 </p></dd>
2837 <dt><span class="term"><span><strong class="command">rfc2308-type1</strong></span></span></dt>
2838 <dd>
2839 <p>
2840                   Setting this to <strong class="userinput"><code>yes</code></strong> will
2841                   cause the server to send NS records along with the SOA
2842                   record for negative
2843                   answers. The default is <strong class="userinput"><code>no</code></strong>.
2844                 </p>
2845 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
2846 <h3 class="title">Note</h3>
2847 <p>
2848                     Not yet implemented in <acronym class="acronym">BIND</acronym>
2849                     9.
2850                   </p>
2851 </div>
2852 </dd>
2853 <dt><span class="term"><span><strong class="command">use-id-pool</strong></span></span></dt>
2854 <dd><p>
2855                   <span class="emphasis"><em>This option is obsolete</em></span>.
2856                   <acronym class="acronym">BIND</acronym> 9 always allocates query
2857                   IDs from a pool.
2858                 </p></dd>
2859 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
2860 <dd><p>
2861                   If <strong class="userinput"><code>yes</code></strong>, the server will collect
2862                   statistical data on all zones (unless specifically turned
2863                   off
2864                   on a per-zone basis by specifying <span><strong class="command">zone-statistics no</strong></span>
2865                   in the <span><strong class="command">zone</strong></span> statement).
2866                   These statistics may be accessed
2867                   using <span><strong class="command">rndc stats</strong></span>, which will
2868                   dump them to the file listed
2869                   in the <span><strong class="command">statistics-file</strong></span>.  See
2870                   also <a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called &#8220;The Statistics File&#8221;</a>.
2871                 </p></dd>
2872 <dt><span class="term"><span><strong class="command">use-ixfr</strong></span></span></dt>
2873 <dd><p>
2874                   <span class="emphasis"><em>This option is obsolete</em></span>.
2875                   If you need to disable IXFR to a particular server or
2876                   servers, see
2877                   the information on the <span><strong class="command">provide-ixfr</strong></span> option
2878                   in <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
2879             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
2880             Usage&#8221;</a>.
2881                   See also
2882                   <a href="Bv9ARM.ch04.html#incremental_zone_transfers" title="Incremental Zone Transfers (IXFR)">the section called &#8220;Incremental Zone Transfers (IXFR)&#8221;</a>.
2883                 </p></dd>
2884 <dt><span class="term"><span><strong class="command">provide-ixfr</strong></span></span></dt>
2885 <dd><p>
2886                   See the description of
2887                   <span><strong class="command">provide-ixfr</strong></span> in
2888                   <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
2889             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
2890             Usage&#8221;</a>.
2891                 </p></dd>
2892 <dt><span class="term"><span><strong class="command">request-ixfr</strong></span></span></dt>
2893 <dd><p>
2894                   See the description of
2895                   <span><strong class="command">request-ixfr</strong></span> in
2896                   <a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and
2897             Usage">the section called &#8220;<span><strong class="command">server</strong></span> Statement Definition and
2898             Usage&#8221;</a>.
2899                 </p></dd>
2900 <dt><span class="term"><span><strong class="command">treat-cr-as-space</strong></span></span></dt>
2901 <dd><p>
2902                   This option was used in <acronym class="acronym">BIND</acronym>
2903                   8 to make
2904                   the server treat carriage return ("<span><strong class="command">\r</strong></span>") characters the same way
2905                   as a space or tab character,
2906                   to facilitate loading of zone files on a UNIX system that
2907                   were generated
2908                   on an NT or DOS machine. In <acronym class="acronym">BIND</acronym> 9, both UNIX "<span><strong class="command">\n</strong></span>"
2909                   and NT/DOS "<span><strong class="command">\r\n</strong></span>" newlines
2910                   are always accepted,
2911                   and the option is ignored.
2912                 </p></dd>
2913 <dt>
2914 <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>
2915 </dt>
2916 <dd>
2917 <p>
2918                   These options control the behavior of an authoritative
2919                   server when
2920                   answering queries which have additional data, or when
2921                   following CNAME
2922                   and DNAME chains.
2923                 </p>
2924 <p>
2925                   When both of these options are set to <strong class="userinput"><code>yes</code></strong>
2926                   (the default) and a
2927                   query is being answered from authoritative data (a zone
2928                   configured into the server), the additional data section of
2929                   the
2930                   reply will be filled in using data from other authoritative
2931                   zones
2932                   and from the cache.  In some situations this is undesirable,
2933                   such
2934                   as when there is concern over the correctness of the cache,
2935                   or
2936                   in servers where slave zones may be added and modified by
2937                   untrusted third parties.  Also, avoiding
2938                   the search for this additional data will speed up server
2939                   operations
2940                   at the possible expense of additional queries to resolve
2941                   what would
2942                   otherwise be provided in the additional section.
2943                 </p>
2944 <p>
2945                   For example, if a query asks for an MX record for host <code class="literal">foo.example.com</code>,
2946                   and the record found is "<code class="literal">MX 10 mail.example.net</code>", normally the address
2947                   records (A and AAAA) for <code class="literal">mail.example.net</code> will be provided as well,
2948                   if known, even though they are not in the example.com zone.
2949                   Setting these options to <span><strong class="command">no</strong></span>
2950                   disables this behavior and makes
2951                   the server only search for additional data in the zone it
2952                   answers from.
2953                 </p>
2954 <p>
2955                   These options are intended for use in authoritative-only
2956                   servers, or in authoritative-only views.  Attempts to set
2957                   them to <span><strong class="command">no</strong></span> without also
2958                   specifying
2959                   <span><strong class="command">recursion no</strong></span> will cause the
2960                   server to
2961                   ignore the options and log a warning message.
2962                 </p>
2963 <p>
2964                   Specifying <span><strong class="command">additional-from-cache no</strong></span> actually
2965                   disables the use of the cache not only for additional data
2966                   lookups
2967                   but also when looking up the answer.  This is usually the
2968                   desired
2969                   behavior in an authoritative-only server where the
2970                   correctness of
2971                   the cached data is an issue.
2972                 </p>
2973 <p>
2974                   When a name server is non-recursively queried for a name
2975                   that is not
2976                   below the apex of any served zone, it normally answers with
2977                   an
2978                   "upwards referral" to the root servers or the servers of
2979                   some other
2980                   known parent of the query name.  Since the data in an
2981                   upwards referral
2982                   comes from the cache, the server will not be able to provide
2983                   upwards
2984                   referrals when <span><strong class="command">additional-from-cache no</strong></span>
2985                   has been specified.  Instead, it will respond to such
2986                   queries
2987                   with REFUSED.  This should not cause any problems since
2988                   upwards referrals are not required for the resolution
2989                   process.
2990                 </p>
2991 </dd>
2992 <dt><span class="term"><span><strong class="command">match-mapped-addresses</strong></span></span></dt>
2993 <dd><p>
2994                   If <strong class="userinput"><code>yes</code></strong>, then an
2995                   IPv4-mapped IPv6 address will match any address match
2996                   list entries that match the corresponding IPv4 address.
2997                   Enabling this option is sometimes useful on IPv6-enabled
2998                   Linux
2999                   systems, to work around a kernel quirk that causes IPv4
3000                   TCP connections such as zone transfers to be accepted
3001                   on an IPv6 socket using mapped addresses, causing
3002                   address match lists designed for IPv4 to fail to match.
3003                   The use of this option for any other purpose is discouraged.
3004                 </p></dd>
3005 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
3006 <dd>
3007 <p>
3008                   When <strong class="userinput"><code>yes</code></strong> and the server loads a new version of a master
3009                   zone from its zone file or receives a new version of a slave
3010                   file by a non-incremental zone transfer, it will compare
3011                   the new version to the previous one and calculate a set
3012                   of differences.  The differences are then logged in the
3013                   zone's journal file such that the changes can be transmitted
3014                   to downstream slaves as an incremental zone transfer.
3015                 </p>
3016 <p>
3017                   By allowing incremental zone transfers to be used for
3018                   non-dynamic zones, this option saves bandwidth at the
3019                   expense of increased CPU and memory consumption at the
3020                   master.
3021                   In particular, if the new version of a zone is completely
3022                   different from the previous one, the set of differences
3023                   will be of a size comparable to the combined size of the
3024                   old and new zone version, and the server will need to
3025                   temporarily allocate memory to hold this complete
3026                   difference set.
3027                 </p>
3028 <p><span><strong class="command">ixfr-from-differences</strong></span>
3029                   also accepts <span><strong class="command">master</strong></span> and
3030                   <span><strong class="command">slave</strong></span> at the view and options
3031                   levels which causes
3032                   <span><strong class="command">ixfr-from-differences</strong></span> to be enabled for
3033                   all <span><strong class="command">master</strong></span> or
3034                   <span><strong class="command">slave</strong></span> zones respectively.
3035                   It is off by default.
3036                 </p>
3037 </dd>
3038 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
3039 <dd><p>
3040                   This should be set when you have multiple masters for a zone
3041                   and the
3042                   addresses refer to different machines.  If <strong class="userinput"><code>yes</code></strong>, <span><strong class="command">named</strong></span> will
3043                   not log
3044                   when the serial number on the master is less than what <span><strong class="command">named</strong></span>
3045                   currently
3046                   has.  The default is <strong class="userinput"><code>no</code></strong>.
3047                 </p></dd>
3048 <dt><span class="term"><span><strong class="command">dnssec-enable</strong></span></span></dt>
3049 <dd><p>
3050                   Enable DNSSEC support in <span><strong class="command">named</strong></span>.  Unless set to <strong class="userinput"><code>yes</code></strong>,
3051                   <span><strong class="command">named</strong></span> behaves as if it does not support DNSSEC.
3052                   The default is <strong class="userinput"><code>yes</code></strong>.
3053                 </p></dd>
3054 <dt><span class="term"><span><strong class="command">dnssec-validation</strong></span></span></dt>
3055 <dd><p>
3056                   Enable DNSSEC validation in <span><strong class="command">named</strong></span>.
3057                   Note <span><strong class="command">dnssec-enable</strong></span> also needs to be
3058                   set to <strong class="userinput"><code>yes</code></strong> to be effective.
3059                   The default is <strong class="userinput"><code>yes</code></strong>.
3060                 </p></dd>
3061 <dt><span class="term"><span><strong class="command">dnssec-accept-expired</strong></span></span></dt>
3062 <dd><p>
3063                   Accept expired signatures when verifying DNSSEC signatures.
3064                   The default is <strong class="userinput"><code>no</code></strong>.
3065                   Setting this option to "yes" leaves <span><strong class="command">named</strong></span> vulnerable to replay attacks.
3066                 </p></dd>
3067 <dt><span class="term"><span><strong class="command">querylog</strong></span></span></dt>
3068 <dd><p>
3069                   Specify whether query logging should be started when <span><strong class="command">named</strong></span>
3070                   starts.
3071                   If <span><strong class="command">querylog</strong></span> is not specified,
3072                   then the query logging
3073                   is determined by the presence of the logging category <span><strong class="command">queries</strong></span>.
3074                 </p></dd>
3075 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
3076 <dd>
3077 <p>
3078                   This option is used to restrict the character set and syntax
3079                   of
3080                   certain domain names in master files and/or DNS responses
3081                   received
3082                   from the network.  The default varies according to usage
3083                   area.  For
3084                   <span><strong class="command">master</strong></span> zones the default is <span><strong class="command">fail</strong></span>.
3085                   For <span><strong class="command">slave</strong></span> zones the default
3086                   is <span><strong class="command">warn</strong></span>.
3087                   For answers received from the network (<span><strong class="command">response</strong></span>)
3088                   the default is <span><strong class="command">ignore</strong></span>.
3089                 </p>
3090 <p>
3091                   The rules for legal hostnames and mail domains are derived
3092                   from RFC 952 and RFC 821 as modified by RFC 1123.
3093                 </p>
3094 <p><span><strong class="command">check-names</strong></span>
3095                   applies to the owner names of A, AAAA and MX records.
3096                   It also applies to the domain names in the RDATA of NS, SOA,
3097                   MX, and SRV records.
3098                   It also applies to the RDATA of PTR records where the owner
3099                   name indicated that it is a reverse lookup of a hostname
3100                   (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, or IP6.INT).
3101                 </p>
3102 </dd>
3103 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
3104 <dd><p>
3105                   Check whether the MX record appears to refer to a IP address.
3106                   The default is to <span><strong class="command">warn</strong></span>.  Other possible
3107                   values are <span><strong class="command">fail</strong></span> and
3108                   <span><strong class="command">ignore</strong></span>.
3109                 </p></dd>
3110 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
3111 <dd><p>
3112                   This option is used to check for non-terminal wildcards.
3113                   The use of non-terminal wildcards is almost always as a
3114                   result of a failure
3115                   to understand the wildcard matching algorithm (RFC 1034).
3116                   This option
3117                   affects master zones.  The default (<span><strong class="command">yes</strong></span>) is to check
3118                   for non-terminal wildcards and issue a warning.
3119                 </p></dd>
3120 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
3121 <dd><p>
3122                   Perform post load zone integrity checks on master
3123                   zones.  This checks that MX and SRV records refer
3124                   to address (A or AAAA) records and that glue
3125                   address records exist for delegated zones.  For
3126                   MX and SRV records only in-zone hostnames are
3127                   checked (for out-of-zone hostnames use
3128                   <span><strong class="command">named-checkzone</strong></span>).
3129                   For NS records only names below top of zone are
3130                   checked (for out-of-zone names and glue consistency
3131                   checks use <span><strong class="command">named-checkzone</strong></span>).
3132                   The default is <span><strong class="command">yes</strong></span>.
3133                 </p></dd>
3134 <dt><span class="term"><span><strong class="command">check-mx-cname</strong></span></span></dt>
3135 <dd><p>
3136                   If <span><strong class="command">check-integrity</strong></span> is set then
3137                   fail, warn or ignore MX records that refer
3138                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
3139                 </p></dd>
3140 <dt><span class="term"><span><strong class="command">check-srv-cname</strong></span></span></dt>
3141 <dd><p>
3142                   If <span><strong class="command">check-integrity</strong></span> is set then
3143                   fail, warn or ignore SRV records that refer
3144                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
3145                 </p></dd>
3146 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
3147 <dd><p>
3148                   When performing integrity checks, also check that
3149                   sibling glue exists.  The default is <span><strong class="command">yes</strong></span>.
3150                 </p></dd>
3151 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
3152 <dd><p>
3153                   When returning authoritative negative responses to
3154                   SOA queries set the TTL of the SOA record returned in
3155                   the authority section to zero.
3156                   The default is <span><strong class="command">yes</strong></span>.
3157                 </p></dd>
3158 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl-cache</strong></span></span></dt>
3159 <dd><p>
3160                   When caching a negative response to a SOA query
3161                   set the TTL to zero.
3162                   The default is <span><strong class="command">no</strong></span>.
3163                 </p></dd>
3164 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
3165 <dd><p>
3166                   When regenerating the RRSIGs following a UPDATE
3167                   request to a secure zone, check the KSK flag on
3168                   the DNSKEY RR to determine if this key should be
3169                   used to generate the RRSIG.  This flag is ignored
3170                   if there are not DNSKEY RRs both with and without
3171                   a KSK.
3172                   The default is <span><strong class="command">yes</strong></span>.
3173                 </p></dd>
3174 <dt><span class="term"><span><strong class="command">try-tcp-refresh</strong></span></span></dt>
3175 <dd><p>
3176                   Try to refresh the zone using TCP if UDP queries fail.
3177                   For BIND 8 compatibility, the default is
3178                   <span><strong class="command">yes</strong></span>.
3179                 </p></dd>
3180 </dl></div>
3181 </div>
3182 <div class="sect3" lang="en">
3183 <div class="titlepage"><div><div><h4 class="title">
3184 <a name="id2581747"></a>Forwarding</h4></div></div></div>
3185 <p>
3186             The forwarding facility can be used to create a large site-wide
3187             cache on a few servers, reducing traffic over links to external
3188             name servers. It can also be used to allow queries by servers that
3189             do not have direct access to the Internet, but wish to look up
3190             exterior
3191             names anyway. Forwarding occurs only on those queries for which
3192             the server is not authoritative and does not have the answer in
3193             its cache.
3194           </p>
3195 <div class="variablelist"><dl>
3196 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
3197 <dd><p>
3198                   This option is only meaningful if the
3199                   forwarders list is not empty. A value of <code class="varname">first</code>,
3200                   the default, causes the server to query the forwarders
3201                   first &#8212; and
3202                   if that doesn't answer the question, the server will then
3203                   look for
3204                   the answer itself. If <code class="varname">only</code> is
3205                   specified, the
3206                   server will only query the forwarders.
3207                 </p></dd>
3208 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
3209 <dd><p>
3210                   Specifies the IP addresses to be used
3211                   for forwarding. The default is the empty list (no
3212                   forwarding).
3213                 </p></dd>
3214 </dl></div>
3215 <p>
3216             Forwarding can also be configured on a per-domain basis, allowing
3217             for the global forwarding options to be overridden in a variety
3218             of ways. You can set particular domains to use different
3219             forwarders,
3220             or have a different <span><strong class="command">forward only/first</strong></span> behavior,
3221             or not forward at all, see <a href="Bv9ARM.ch06.html#zone_statement_grammar" title="zone
3222             Statement Grammar">the section called &#8220;<span><strong class="command">zone</strong></span>
3223             Statement Grammar&#8221;</a>.
3224           </p>
3225 </div>
3226 <div class="sect3" lang="en">
3227 <div class="titlepage"><div><div><h4 class="title">
3228 <a name="id2581874"></a>Dual-stack Servers</h4></div></div></div>
3229 <p>
3230             Dual-stack servers are used as servers of last resort to work
3231             around
3232             problems in reachability due the lack of support for either IPv4
3233             or IPv6
3234             on the host machine.
3235           </p>
3236 <div class="variablelist"><dl>
3237 <dt><span class="term"><span><strong class="command">dual-stack-servers</strong></span></span></dt>
3238 <dd><p>
3239                   Specifies host names or addresses of machines with access to
3240                   both IPv4 and IPv6 transports. If a hostname is used, the
3241                   server must be able
3242                   to resolve the name using only the transport it has.  If the
3243                   machine is dual
3244                   stacked, then the <span><strong class="command">dual-stack-servers</strong></span> have no effect unless
3245                   access to a transport has been disabled on the command line
3246                   (e.g. <span><strong class="command">named -4</strong></span>).
3247                 </p></dd>
3248 </dl></div>
3249 </div>
3250 <div class="sect3" lang="en">
3251 <div class="titlepage"><div><div><h4 class="title">
3252 <a name="access_control"></a>Access Control</h4></div></div></div>
3253 <p>
3254             Access to the server can be restricted based on the IP address
3255             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
3256             details on how to specify IP address lists.
3257           </p>
3258 <div class="variablelist"><dl>
3259 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
3260 <dd><p>
3261                   Specifies which hosts are allowed to
3262                   notify this server, a slave, of zone changes in addition
3263                   to the zone masters.
3264                   <span><strong class="command">allow-notify</strong></span> may also be
3265                   specified in the
3266                   <span><strong class="command">zone</strong></span> statement, in which case
3267                   it overrides the
3268                   <span><strong class="command">options allow-notify</strong></span>
3269                   statement.  It is only meaningful
3270                   for a slave zone.  If not specified, the default is to
3271                   process notify messages
3272                   only from a zone's master.
3273                 </p></dd>
3274 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
3275 <dd>
3276 <p>
3277                   Specifies which hosts are allowed to ask ordinary
3278                   DNS questions. <span><strong class="command">allow-query</strong></span> may
3279                   also be specified in the <span><strong class="command">zone</strong></span>
3280                   statement, in which case it overrides the
3281                   <span><strong class="command">options allow-query</strong></span> statement.
3282                   If not specified, the default is to allow queries
3283                   from all hosts.
3284                 </p>
3285 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3286 <h3 class="title">Note</h3>
3287 <p>
3288                     <span><strong class="command">allow-query-cache</strong></span> is now
3289                     used to specify access to the cache.
3290                   </p>
3291 </div>
3292 </dd>
3293 <dt><span class="term"><span><strong class="command">allow-query-on</strong></span></span></dt>
3294 <dd>
3295 <p>
3296                   Specifies which local addresses can accept ordinary
3297                   DNS questions. This makes it possible, for instance,
3298                   to allow queries on internal-facing interfaces but
3299                   disallow them on external-facing ones, without
3300                   necessarily knowing the internal network's addresses.
3301                 </p>
3302 <p>
3303                   <span><strong class="command">allow-query-on</strong></span> may
3304                   also be specified in the <span><strong class="command">zone</strong></span>
3305                   statement, in which case it overrides the
3306                   <span><strong class="command">options allow-query-on</strong></span> statement.
3307                 </p>
3308 <p>
3309                   If not specified, the default is to allow queries
3310                   on all addresses.
3311                 </p>
3312 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3313 <h3 class="title">Note</h3>
3314 <p>
3315                     <span><strong class="command">allow-query-cache</strong></span> is
3316                     used to specify access to the cache.
3317                   </p>
3318 </div>
3319 </dd>
3320 <dt><span class="term"><span><strong class="command">allow-query-cache</strong></span></span></dt>
3321 <dd><p>
3322                   Specifies which hosts are allowed to get answers
3323                   from the cache.  If <span><strong class="command">allow-query-cache</strong></span>
3324                   is not set then <span><strong class="command">allow-recursion</strong></span>
3325                   is used if set, otherwise <span><strong class="command">allow-query</strong></span>
3326                   is used if set unless <span><strong class="command">recursion no;</strong></span> is
3327                   set in which case <span><strong class="command">none;</strong></span> is used,
3328                   otherwise the default (<span><strong class="command">localnets;</strong></span>
3329                   <span><strong class="command">localhost;</strong></span>) is used.
3330                 </p></dd>
3331 <dt><span class="term"><span><strong class="command">allow-query-cache-on</strong></span></span></dt>
3332 <dd><p>
3333                   Specifies which local addresses can give answers
3334                   from the cache.  If not specified, the default is
3335                   to allow cache queries on any address,
3336                   <span><strong class="command">localnets</strong></span> and
3337                   <span><strong class="command">localhost</strong></span>.
3338                 </p></dd>
3339 <dt><span class="term"><span><strong class="command">allow-recursion</strong></span></span></dt>
3340 <dd><p>
3341                   Specifies which hosts are allowed to make recursive
3342                   queries through this server. If
3343                   <span><strong class="command">allow-recursion</strong></span> is not set
3344                   then <span><strong class="command">allow-query-cache</strong></span> is
3345                   used if set, otherwise <span><strong class="command">allow-query</strong></span>
3346                   is used if set, otherwise the default
3347                   (<span><strong class="command">localnets;</strong></span>
3348                   <span><strong class="command">localhost;</strong></span>) is used.
3349                 </p></dd>
3350 <dt><span class="term"><span><strong class="command">allow-recursion-on</strong></span></span></dt>
3351 <dd><p>
3352                   Specifies which local addresses can accept recursive
3353                   queries.  If not specified, the default is to allow
3354                   recursive queries on all addresses.
3355                 </p></dd>
3356 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
3357 <dd><p>
3358                   Specifies which hosts are allowed to
3359                   submit Dynamic DNS updates for master zones. The default is
3360                   to deny
3361                   updates from all hosts.  Note that allowing updates based
3362                   on the requestor's IP address is insecure; see
3363                   <a href="Bv9ARM.ch07.html#dynamic_update_security" title="Dynamic Update Security">the section called &#8220;Dynamic Update Security&#8221;</a> for details.
3364                 </p></dd>
3365 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
3366 <dd>
3367 <p>
3368                   Specifies which hosts are allowed to
3369                   submit Dynamic DNS updates to slave zones to be forwarded to
3370                   the
3371                   master.  The default is <strong class="userinput"><code>{ none; }</code></strong>,
3372                   which
3373                   means that no update forwarding will be performed.  To
3374                   enable
3375                   update forwarding, specify
3376                   <strong class="userinput"><code>allow-update-forwarding { any; };</code></strong>.
3377                   Specifying values other than <strong class="userinput"><code>{ none; }</code></strong> or
3378                   <strong class="userinput"><code>{ any; }</code></strong> is usually
3379                   counterproductive, since
3380                   the responsibility for update access control should rest
3381                   with the
3382                   master server, not the slaves.
3383                 </p>
3384 <p>
3385                   Note that enabling the update forwarding feature on a slave
3386                   server
3387                   may expose master servers relying on insecure IP address
3388                   based
3389                   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>
3390                   for more details.
3391                 </p>
3392 </dd>
3393 <dt><span class="term"><span><strong class="command">allow-v6-synthesis</strong></span></span></dt>
3394 <dd><p>
3395                   This option was introduced for the smooth transition from
3396                   AAAA
3397                   to A6 and from "nibble labels" to binary labels.
3398                   However, since both A6 and binary labels were then
3399                   deprecated,
3400                   this option was also deprecated.
3401                   It is now ignored with some warning messages.
3402                 </p></dd>
3403 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
3404 <dd><p>
3405                   Specifies which hosts are allowed to
3406                   receive zone transfers from the server. <span><strong class="command">allow-transfer</strong></span> may
3407                   also be specified in the <span><strong class="command">zone</strong></span>
3408                   statement, in which
3409                   case it overrides the <span><strong class="command">options allow-transfer</strong></span> statement.
3410                   If not specified, the default is to allow transfers to all
3411                   hosts.
3412                 </p></dd>
3413 <dt><span class="term"><span><strong class="command">blackhole</strong></span></span></dt>
3414 <dd><p>
3415                   Specifies a list of addresses that the
3416                   server will not accept queries from or use to resolve a
3417                   query. Queries
3418                   from these addresses will not be responded to. The default
3419                   is <strong class="userinput"><code>none</code></strong>.
3420                 </p></dd>
3421 </dl></div>
3422 </div>
3423 <div class="sect3" lang="en">
3424 <div class="titlepage"><div><div><h4 class="title">
3425 <a name="id2582379"></a>Interfaces</h4></div></div></div>
3426 <p>
3427             The interfaces and ports that the server will answer queries
3428             from may be specified using the <span><strong class="command">listen-on</strong></span> option. <span><strong class="command">listen-on</strong></span> takes
3429             an optional port and an <code class="varname">address_match_list</code>.
3430             The server will listen on all interfaces allowed by the address
3431             match list. If a port is not specified, port 53 will be used.
3432           </p>
3433 <p>
3434             Multiple <span><strong class="command">listen-on</strong></span> statements are
3435             allowed.
3436             For example,
3437           </p>
3438 <pre class="programlisting">listen-on { 5.6.7.8; };
3439 listen-on port 1234 { !1.2.3.4; 1.2/16; };
3440 </pre>
3441 <p>
3442             will enable the name server on port 53 for the IP address
3443             5.6.7.8, and on port 1234 of an address on the machine in net
3444             1.2 that is not 1.2.3.4.
3445           </p>
3446 <p>
3447             If no <span><strong class="command">listen-on</strong></span> is specified, the
3448             server will listen on port 53 on all IPv4 interfaces.
3449           </p>
3450 <p>
3451             The <span><strong class="command">listen-on-v6</strong></span> option is used to
3452             specify the interfaces and the ports on which the server will
3453             listen
3454             for incoming queries sent using IPv6.
3455           </p>
3456 <p>
3457             When </p>
3458 <pre class="programlisting">{ any; }</pre>
3459 <p> is
3460             specified
3461             as the <code class="varname">address_match_list</code> for the
3462             <span><strong class="command">listen-on-v6</strong></span> option,
3463             the server does not bind a separate socket to each IPv6 interface
3464             address as it does for IPv4 if the operating system has enough API
3465             support for IPv6 (specifically if it conforms to RFC 3493 and RFC
3466             3542).
3467             Instead, it listens on the IPv6 wildcard address.
3468             If the system only has incomplete API support for IPv6, however,
3469             the behavior is the same as that for IPv4.
3470           </p>
3471 <p>
3472             A list of particular IPv6 addresses can also be specified, in
3473             which case
3474             the server listens on a separate socket for each specified
3475             address,
3476             regardless of whether the desired API is supported by the system.
3477           </p>
3478 <p>
3479             Multiple <span><strong class="command">listen-on-v6</strong></span> options can
3480             be used.
3481             For example,
3482           </p>
3483 <pre class="programlisting">listen-on-v6 { any; };
3484 listen-on-v6 port 1234 { !2001:db8::/32; any; };
3485 </pre>
3486 <p>
3487             will enable the name server on port 53 for any IPv6 addresses
3488             (with a single wildcard socket),
3489             and on port 1234 of IPv6 addresses that is not in the prefix
3490             2001:db8::/32 (with separate sockets for each matched address.)
3491           </p>
3492 <p>
3493             To make the server not listen on any IPv6 address, use
3494           </p>
3495 <pre class="programlisting">listen-on-v6 { none; };
3496 </pre>
3497 <p>
3498             If no <span><strong class="command">listen-on-v6</strong></span> option is
3499             specified, the server will not listen on any IPv6 address
3500             unless <span><strong class="command">-6</strong></span> is specified when <span><strong class="command">named</strong></span> is
3501             invoked.  If <span><strong class="command">-6</strong></span> is specified then
3502             <span><strong class="command">named</strong></span> will listen on port 53 on all IPv6 interfaces by default.
3503           </p>
3504 </div>
3505 <div class="sect3" lang="en">
3506 <div class="titlepage"><div><div><h4 class="title">
3507 <a name="query_address"></a>Query Address</h4></div></div></div>
3508 <p>
3509             If the server doesn't know the answer to a question, it will
3510             query other name servers. <span><strong class="command">query-source</strong></span> specifies
3511             the address and port used for such queries. For queries sent over
3512             IPv6, there is a separate <span><strong class="command">query-source-v6</strong></span> option.
3513             If <span><strong class="command">address</strong></span> is <span><strong class="command">*</strong></span> (asterisk) or is omitted,
3514             a wildcard IP address (<span><strong class="command">INADDR_ANY</strong></span>)
3515             will be used.
3516           </p>
3517 <p>
3518             If <span><strong class="command">port</strong></span> is <span><strong class="command">*</strong></span> or is omitted,
3519             a random port number from a pre-configured
3520             range is picked up and will be used for each query.
3521             The port range(s) is that specified in
3522             the <span><strong class="command">use-v4-udp-ports</strong></span> (for IPv4)
3523             and <span><strong class="command">use-v6-udp-ports</strong></span> (for IPv6)
3524             options, excluding the ranges specified in
3525             the <span><strong class="command">avoid-v4-udp-ports</strong></span>
3526             and <span><strong class="command">avoid-v6-udp-ports</strong></span> options, respectively.
3527           </p>
3528 <p>
3529             The defaults of the <span><strong class="command">query-source</strong></span> and
3530             <span><strong class="command">query-source-v6</strong></span> options
3531             are:
3532           </p>
3533 <pre class="programlisting">query-source address * port *;
3534 query-source-v6 address * port *;
3535 </pre>
3536 <p>
3537             If <span><strong class="command">use-v4-udp-ports</strong></span> or
3538             <span><strong class="command">use-v6-udp-ports</strong></span> is unspecified,
3539             <span><strong class="command">named</strong></span> will check if the operating
3540             system provides a programming interface to retrieve the
3541             system's default range for ephemeral ports.
3542             If such an interface is available,
3543             <span><strong class="command">named</strong></span> will use the corresponding system
3544             default range; otherwise, it will use its own defaults:
3545          </p>
3546 <pre class="programlisting">use-v4-udp-ports { range 1024 65535; };
3547 use-v6-udp-ports { range 1024 65535; };
3548 </pre>
3549 <p>
3550             Note: make sure the ranges be sufficiently large for
3551             security.  A desirable size depends on various parameters,
3552             but we generally recommend it contain at least 16384 ports
3553             (14 bits of entropy).
3554             Note also that the system's default range when used may be
3555             too small for this purpose, and that the range may even be
3556             changed while <span><strong class="command">named</strong></span> is running; the new
3557             range will automatically be applied when <span><strong class="command">named</strong></span>
3558             is reloaded.
3559             It is encouraged to
3560             configure <span><strong class="command">use-v4-udp-ports</strong></span> and
3561             <span><strong class="command">use-v6-udp-ports</strong></span> explicitly so that the
3562             ranges are sufficiently large and are reasonably
3563             independent from the ranges used by other applications.
3564           </p>
3565 <p>
3566             Note: the operational configuration
3567             where <span><strong class="command">named</strong></span> runs may prohibit the use
3568             of some ports.  For example, UNIX systems will not allow
3569             <span><strong class="command">named</strong></span> running without a root privilege
3570             to use ports less than 1024.
3571             If such ports are included in the specified (or detected)
3572             set of query ports, the corresponding query attempts will
3573             fail, resulting in resolution failures or delay.
3574             It is therefore important to configure the set of ports
3575             that can be safely used in the expected operational environment.
3576           </p>
3577 <p>
3578             The defaults of the <span><strong class="command">avoid-v4-udp-ports</strong></span> and
3579             <span><strong class="command">avoid-v6-udp-ports</strong></span> options
3580             are:
3581           </p>
3582 <pre class="programlisting">avoid-v4-udp-ports {};
3583 avoid-v6-udp-ports {};
3584 </pre>
3585 <p>
3586             Note: BIND 9.5.0 introduced
3587             the <span><strong class="command">use-queryport-pool</strong></span>
3588             option to support a pool of such random ports, but this
3589             option is now obsolete because reusing the same ports in
3590             the pool may not be sufficiently secure.
3591             For the same reason, it is generally strongly discouraged to
3592             specify a particular port for the
3593             <span><strong class="command">query-source</strong></span> or
3594             <span><strong class="command">query-source-v6</strong></span> options;
3595             it implicitly disables the use of randomized port numbers.
3596           </p>
3597 <div class="variablelist"><dl>
3598 <dt><span class="term"><span><strong class="command">use-queryport-pool</strong></span></span></dt>
3599 <dd><p>
3600                   This option is obsolete.
3601                 </p></dd>
3602 <dt><span class="term"><span><strong class="command">queryport-pool-ports</strong></span></span></dt>
3603 <dd><p>
3604                   This option is obsolete.
3605                 </p></dd>
3606 <dt><span class="term"><span><strong class="command">queryport-pool-updateinterval</strong></span></span></dt>
3607 <dd><p>
3608                   This option is obsolete.
3609                 </p></dd>
3610 </dl></div>
3611 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3612 <h3 class="title">Note</h3>
3613 <p>
3614               The address specified in the <span><strong class="command">query-source</strong></span> option
3615               is used for both UDP and TCP queries, but the port applies only
3616               to UDP queries.  TCP queries always use a random
3617               unprivileged port.
3618             </p>
3619 </div>
3620 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3621 <h3 class="title">Note</h3>
3622 <p>
3623               Solaris 2.5.1 and earlier does not support setting the source
3624               address for TCP sockets.
3625             </p>
3626 </div>
3627 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3628 <h3 class="title">Note</h3>
3629 <p>
3630               See also <span><strong class="command">transfer-source</strong></span> and
3631               <span><strong class="command">notify-source</strong></span>.
3632             </p>
3633 </div>
3634 </div>
3635 <div class="sect3" lang="en">
3636 <div class="titlepage"><div><div><h4 class="title">
3637 <a name="zone_transfers"></a>Zone Transfers</h4></div></div></div>
3638 <p>
3639             <acronym class="acronym">BIND</acronym> has mechanisms in place to
3640             facilitate zone transfers
3641             and set limits on the amount of load that transfers place on the
3642             system. The following options apply to zone transfers.
3643           </p>
3644 <div class="variablelist"><dl>
3645 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
3646 <dd><p>
3647                   Defines a global list of IP addresses of name servers
3648                   that are also sent NOTIFY messages whenever a fresh copy of
3649                   the
3650                   zone is loaded, in addition to the servers listed in the
3651                   zone's NS records.
3652                   This helps to ensure that copies of the zones will
3653                   quickly converge on stealth servers.
3654                   Optionally, a port may be specified with each
3655                   <span><strong class="command">also-notify</strong></span> address to send
3656                   the notify messages to a port other than the
3657                   default of 53.
3658                   If an <span><strong class="command">also-notify</strong></span> list
3659                   is given in a <span><strong class="command">zone</strong></span> statement,
3660                   it will override
3661                   the <span><strong class="command">options also-notify</strong></span>
3662                   statement. When a <span><strong class="command">zone notify</strong></span>
3663                   statement
3664                   is set to <span><strong class="command">no</strong></span>, the IP
3665                   addresses in the global <span><strong class="command">also-notify</strong></span> list will
3666                   not be sent NOTIFY messages for that zone. The default is
3667                   the empty
3668                   list (no global notification list).
3669                 </p></dd>
3670 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
3671 <dd><p>
3672                   Inbound zone transfers running longer than
3673                   this many minutes will be terminated. The default is 120
3674                   minutes
3675                   (2 hours).  The maximum value is 28 days (40320 minutes).
3676                 </p></dd>
3677 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
3678 <dd><p>
3679                   Inbound zone transfers making no progress
3680                   in this many minutes will be terminated. The default is 60
3681                   minutes
3682                   (1 hour).  The maximum value is 28 days (40320 minutes).
3683                 </p></dd>
3684 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
3685 <dd><p>
3686                   Outbound zone transfers running longer than
3687                   this many minutes will be terminated. The default is 120
3688                   minutes
3689                   (2 hours).  The maximum value is 28 days (40320 minutes).
3690                 </p></dd>
3691 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
3692 <dd><p>
3693                   Outbound zone transfers making no progress
3694                   in this many minutes will be terminated.  The default is 60
3695                   minutes (1
3696                   hour).  The maximum value is 28 days (40320 minutes).
3697                 </p></dd>
3698 <dt><span class="term"><span><strong class="command">serial-query-rate</strong></span></span></dt>
3699 <dd><p>
3700                   Slave servers will periodically query master servers
3701                   to find out if zone serial numbers have changed. Each such
3702                   query uses
3703                   a minute amount of the slave server's network bandwidth.  To
3704                   limit the
3705                   amount of bandwidth used, BIND 9 limits the rate at which
3706                   queries are
3707                   sent.  The value of the <span><strong class="command">serial-query-rate</strong></span> option,
3708                   an integer, is the maximum number of queries sent per
3709                   second.
3710                   The default is 20.
3711                 </p></dd>
3712 <dt><span class="term"><span><strong class="command">serial-queries</strong></span></span></dt>
3713 <dd><p>
3714                   In BIND 8, the <span><strong class="command">serial-queries</strong></span>
3715                   option
3716                   set the maximum number of concurrent serial number queries
3717                   allowed to be outstanding at any given time.
3718                   BIND 9 does not limit the number of outstanding
3719                   serial queries and ignores the <span><strong class="command">serial-queries</strong></span> option.
3720                   Instead, it limits the rate at which the queries are sent
3721                   as defined using the <span><strong class="command">serial-query-rate</strong></span> option.
3722                 </p></dd>
3723 <dt><span class="term"><span><strong class="command">transfer-format</strong></span></span></dt>
3724 <dd><p>
3725                   Zone transfers can be sent using two different formats,
3726                   <span><strong class="command">one-answer</strong></span> and
3727                   <span><strong class="command">many-answers</strong></span>.
3728                   The <span><strong class="command">transfer-format</strong></span> option is used
3729                   on the master server to determine which format it sends.
3730                   <span><strong class="command">one-answer</strong></span> uses one DNS message per
3731                   resource record transferred.
3732                   <span><strong class="command">many-answers</strong></span> packs as many resource
3733                   records as possible into a message.
3734                   <span><strong class="command">many-answers</strong></span> is more efficient, but is
3735                   only supported by relatively new slave servers,
3736                   such as <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
3737                   8.x and <acronym class="acronym">BIND</acronym> 4.9.5 onwards.
3738                   The <span><strong class="command">many-answers</strong></span> format is also supported by
3739                   recent Microsoft Windows nameservers.
3740                   The default is <span><strong class="command">many-answers</strong></span>.
3741                   <span><strong class="command">transfer-format</strong></span> may be overridden on a
3742                   per-server basis by using the <span><strong class="command">server</strong></span>
3743                   statement.
3744                 </p></dd>
3745 <dt><span class="term"><span><strong class="command">transfers-in</strong></span></span></dt>
3746 <dd><p>
3747                   The maximum number of inbound zone transfers
3748                   that can be running concurrently. The default value is <code class="literal">10</code>.
3749                   Increasing <span><strong class="command">transfers-in</strong></span> may
3750                   speed up the convergence
3751                   of slave zones, but it also may increase the load on the
3752                   local system.
3753                 </p></dd>
3754 <dt><span class="term"><span><strong class="command">transfers-out</strong></span></span></dt>
3755 <dd><p>
3756                   The maximum number of outbound zone transfers
3757                   that can be running concurrently. Zone transfer requests in
3758                   excess
3759                   of the limit will be refused. The default value is <code class="literal">10</code>.
3760                 </p></dd>
3761 <dt><span class="term"><span><strong class="command">transfers-per-ns</strong></span></span></dt>
3762 <dd><p>
3763                   The maximum number of inbound zone transfers
3764                   that can be concurrently transferring from a given remote
3765                   name server.
3766                   The default value is <code class="literal">2</code>.
3767                   Increasing <span><strong class="command">transfers-per-ns</strong></span>
3768                   may
3769                   speed up the convergence of slave zones, but it also may
3770                   increase
3771                   the load on the remote name server. <span><strong class="command">transfers-per-ns</strong></span> may
3772                   be overridden on a per-server basis by using the <span><strong class="command">transfers</strong></span> phrase
3773                   of the <span><strong class="command">server</strong></span> statement.
3774                 </p></dd>
3775 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
3776 <dd>
3777 <p><span><strong class="command">transfer-source</strong></span>
3778                   determines which local address will be bound to IPv4
3779                   TCP connections used to fetch zones transferred
3780                   inbound by the server.  It also determines the
3781                   source IPv4 address, and optionally the UDP port,
3782                   used for the refresh queries and forwarded dynamic
3783                   updates.  If not set, it defaults to a system
3784                   controlled value which will usually be the address
3785                   of the interface "closest to" the remote end. This
3786                   address must appear in the remote end's
3787                   <span><strong class="command">allow-transfer</strong></span> option for the
3788                   zone being transferred, if one is specified. This
3789                   statement sets the
3790                   <span><strong class="command">transfer-source</strong></span> for all zones,
3791                   but can be overridden on a per-view or per-zone
3792                   basis by including a
3793                   <span><strong class="command">transfer-source</strong></span> statement within
3794                   the <span><strong class="command">view</strong></span> or
3795                   <span><strong class="command">zone</strong></span> block in the configuration
3796                   file.
3797                 </p>
3798 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3799 <h3 class="title">Note</h3>
3800 <p>
3801                     Solaris 2.5.1 and earlier does not support setting the
3802                     source address for TCP sockets.
3803                   </p>
3804 </div>
3805 </dd>
3806 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
3807 <dd><p>
3808                   The same as <span><strong class="command">transfer-source</strong></span>,
3809                   except zone transfers are performed using IPv6.
3810                 </p></dd>
3811 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
3812 <dd>
3813 <p>
3814                   An alternate transfer source if the one listed in
3815                   <span><strong class="command">transfer-source</strong></span> fails and
3816                   <span><strong class="command">use-alt-transfer-source</strong></span> is
3817                   set.
3818                 </p>
3819 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3820 <h3 class="title">Note</h3>
3821                   If you do not wish the alternate transfer source
3822                   to be used, you should set
3823                   <span><strong class="command">use-alt-transfer-source</strong></span>
3824                   appropriately and you should not depend upon
3825                   getting an answer back to the first refresh
3826                   query.
3827                 </div>
3828 </dd>
3829 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
3830 <dd><p>
3831                   An alternate transfer source if the one listed in
3832                   <span><strong class="command">transfer-source-v6</strong></span> fails and
3833                   <span><strong class="command">use-alt-transfer-source</strong></span> is
3834                   set.
3835                 </p></dd>
3836 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
3837 <dd><p>
3838                   Use the alternate transfer sources or not.  If views are
3839                   specified this defaults to <span><strong class="command">no</strong></span>
3840                   otherwise it defaults to
3841                   <span><strong class="command">yes</strong></span> (for BIND 8
3842                   compatibility).
3843                 </p></dd>
3844 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
3845 <dd>
3846 <p><span><strong class="command">notify-source</strong></span>
3847                   determines which local source address, and
3848                   optionally UDP port, will be used to send NOTIFY
3849                   messages.  This address must appear in the slave
3850                   server's <span><strong class="command">masters</strong></span> zone clause or
3851                   in an <span><strong class="command">allow-notify</strong></span> clause.  This
3852                   statement sets the <span><strong class="command">notify-source</strong></span>
3853                   for all zones, but can be overridden on a per-zone or
3854                   per-view basis by including a
3855                   <span><strong class="command">notify-source</strong></span> statement within
3856                   the <span><strong class="command">zone</strong></span> or
3857                   <span><strong class="command">view</strong></span> block in the configuration
3858                   file.
3859                 </p>
3860 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3861 <h3 class="title">Note</h3>
3862 <p>
3863                     Solaris 2.5.1 and earlier does not support setting the
3864                     source address for TCP sockets.
3865                   </p>
3866 </div>
3867 </dd>
3868 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
3869 <dd><p>
3870                   Like <span><strong class="command">notify-source</strong></span>,
3871                   but applies to notify messages sent to IPv6 addresses.
3872                 </p></dd>
3873 </dl></div>
3874 </div>
3875 <div class="sect3" lang="en">
3876 <div class="titlepage"><div><div><h4 class="title">
3877 <a name="id2583582"></a>UDP Port Lists</h4></div></div></div>
3878 <p>
3879             <span><strong class="command">use-v4-udp-ports</strong></span>,
3880             <span><strong class="command">avoid-v4-udp-ports</strong></span>,
3881             <span><strong class="command">use-v6-udp-ports</strong></span>, and
3882             <span><strong class="command">avoid-v6-udp-ports</strong></span>
3883             specify a list of IPv4 and IPv6 UDP ports that will be
3884             used or not used as source ports for UDP messages.
3885             See <a href="Bv9ARM.ch06.html#query_address" title="Query Address">the section called &#8220;Query Address&#8221;</a> about how the
3886             available ports are determined.
3887             For example, with the following configuration
3888           </p>
3889 <pre class="programlisting">
3890 use-v6-udp-ports { range 32768 65535; };
3891 avoid-v6-udp-ports { 40000; range 50000 60000; };
3892 </pre>
3893 <p>
3894              UDP ports of IPv6 messages sent
3895              from <span><strong class="command">named</strong></span> will be in one
3896              of the following ranges: 32768 to 39999, 40001 to 49999,
3897              and 60001 to 65535.
3898            </p>
3899 <p>
3900              <span><strong class="command">avoid-v4-udp-ports</strong></span> and
3901              <span><strong class="command">avoid-v6-udp-ports</strong></span> can be used
3902              to prevent <span><strong class="command">named</strong></span> from choosing as its random source port a
3903              port that is blocked by your firewall or a port that is
3904              used by other applications;
3905              if a query went out with a source port blocked by a
3906              firewall, the
3907              answer would not get by the firewall and the name server would
3908              have to query again.
3909              Note: the desired range can also be represented only with
3910              <span><strong class="command">use-v4-udp-ports</strong></span> and
3911              <span><strong class="command">use-v6-udp-ports</strong></span>, and the
3912              <span><strong class="command">avoid-</strong></span> options are redundant in that
3913              sense; they are provided for backward compatibility and
3914              to possibly simplify the port specification.
3915            </p>
3916 </div>
3917 <div class="sect3" lang="en">
3918 <div class="titlepage"><div><div><h4 class="title">
3919 <a name="id2583642"></a>Operating System Resource Limits</h4></div></div></div>
3920 <p>
3921             The server's usage of many system resources can be limited.
3922             Scaled values are allowed when specifying resource limits.  For
3923             example, <span><strong class="command">1G</strong></span> can be used instead of
3924             <span><strong class="command">1073741824</strong></span> to specify a limit of
3925             one
3926             gigabyte. <span><strong class="command">unlimited</strong></span> requests
3927             unlimited use, or the
3928             maximum available amount. <span><strong class="command">default</strong></span>
3929             uses the limit
3930             that was in force when the server was started. See the description
3931             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>.
3932           </p>
3933 <p>
3934             The following options set operating system resource limits for
3935             the name server process.  Some operating systems don't support
3936             some or
3937             any of the limits. On such systems, a warning will be issued if
3938             the
3939             unsupported limit is used.
3940           </p>
3941 <div class="variablelist"><dl>
3942 <dt><span class="term"><span><strong class="command">coresize</strong></span></span></dt>
3943 <dd><p>
3944                   The maximum size of a core dump. The default
3945                   is <code class="literal">default</code>.
3946                 </p></dd>
3947 <dt><span class="term"><span><strong class="command">datasize</strong></span></span></dt>
3948 <dd><p>
3949                   The maximum amount of data memory the server
3950                   may use. The default is <code class="literal">default</code>.
3951                   This is a hard limit on server memory usage.
3952                   If the server attempts to allocate memory in excess of this
3953                   limit, the allocation will fail, which may in turn leave
3954                   the server unable to perform DNS service.  Therefore,
3955                   this option is rarely useful as a way of limiting the
3956                   amount of memory used by the server, but it can be used
3957                   to raise an operating system data size limit that is
3958                   too small by default.  If you wish to limit the amount
3959                   of memory used by the server, use the
3960                   <span><strong class="command">max-cache-size</strong></span> and
3961                   <span><strong class="command">recursive-clients</strong></span>
3962                   options instead.
3963                 </p></dd>
3964 <dt><span class="term"><span><strong class="command">files</strong></span></span></dt>
3965 <dd><p>
3966                   The maximum number of files the server
3967                   may have open concurrently. The default is <code class="literal">unlimited</code>.
3968                 </p></dd>
3969 <dt><span class="term"><span><strong class="command">stacksize</strong></span></span></dt>
3970 <dd><p>
3971                   The maximum amount of stack memory the server
3972                   may use. The default is <code class="literal">default</code>.
3973                 </p></dd>
3974 </dl></div>
3975 </div>
3976 <div class="sect3" lang="en">
3977 <div class="titlepage"><div><div><h4 class="title">
3978 <a name="server_resource_limits"></a>Server  Resource Limits</h4></div></div></div>
3979 <p>
3980             The following options set limits on the server's
3981             resource consumption that are enforced internally by the
3982             server rather than the operating system.
3983           </p>
3984 <div class="variablelist"><dl>
3985 <dt><span class="term"><span><strong class="command">max-ixfr-log-size</strong></span></span></dt>
3986 <dd><p>
3987                   This option is obsolete; it is accepted
3988                   and ignored for BIND 8 compatibility.  The option
3989                   <span><strong class="command">max-journal-size</strong></span> performs a
3990                   similar function in BIND 9.
3991                 </p></dd>
3992 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
3993 <dd><p>
3994                   Sets a maximum size for each journal file
3995                   (see <a href="Bv9ARM.ch04.html#journal" title="The journal file">the section called &#8220;The journal file&#8221;</a>).  When the journal file
3996                   approaches
3997                   the specified size, some of the oldest transactions in the
3998                   journal
3999                   will be automatically removed.  The default is
4000                   <code class="literal">unlimited</code>.
4001                   This may also be set on a per-zone basis.
4002                 </p></dd>
4003 <dt><span class="term"><span><strong class="command">host-statistics-max</strong></span></span></dt>
4004 <dd><p>
4005                   In BIND 8, specifies the maximum number of host statistics
4006                   entries to be kept.
4007                   Not implemented in BIND 9.
4008                 </p></dd>
4009 <dt><span class="term"><span><strong class="command">recursive-clients</strong></span></span></dt>
4010 <dd><p>
4011                   The maximum number of simultaneous recursive lookups
4012                   the server will perform on behalf of clients.  The default
4013                   is
4014                   <code class="literal">1000</code>.  Because each recursing
4015                   client uses a fair
4016                   bit of memory, on the order of 20 kilobytes, the value of
4017                   the
4018                   <span><strong class="command">recursive-clients</strong></span> option may
4019                   have to be decreased
4020                   on hosts with limited memory.
4021                 </p></dd>
4022 <dt><span class="term"><span><strong class="command">tcp-clients</strong></span></span></dt>
4023 <dd><p>
4024                   The maximum number of simultaneous client TCP
4025                   connections that the server will accept.
4026                   The default is <code class="literal">100</code>.
4027                 </p></dd>
4028 <dt><span class="term"><span><strong class="command">reserved-sockets</strong></span></span></dt>
4029 <dd>
4030 <p>
4031                   The number of file descriptors reserved for TCP, stdio,
4032                   etc.  This needs to be big enough to cover the number of
4033                   interfaces <span><strong class="command">named</strong></span> listens on, <span><strong class="command">tcp-clients</strong></span> as well as
4034                   to provide room for outgoing TCP queries and incoming zone
4035                   transfers.  The default is <code class="literal">512</code>.
4036                   The minimum value is <code class="literal">128</code> and the
4037                   maximum value is <code class="literal">128</code> less than
4038                   maxsockets (-S).  This option may be removed in the future.
4039                 </p>
4040 <p>
4041                   This option has little effect on Windows.
4042                 </p>
4043 </dd>
4044 <dt><span class="term"><span><strong class="command">max-cache-size</strong></span></span></dt>
4045 <dd><p>
4046                   The maximum amount of memory to use for the
4047                   server's cache, in bytes.
4048                   When the amount of data in the cache
4049                   reaches this limit, the server will cause records to expire
4050                   prematurely based on an LRU based strategy so that
4051                   the limit is not exceeded.
4052                   A value of 0 is special, meaning that
4053                   records are purged from the cache only when their
4054                   TTLs expire.
4055                   Another special keyword <strong class="userinput"><code>unlimited</code></strong>
4056                   means the maximum value of 32-bit unsigned integers
4057                   (0xffffffff), which may not have the same effect as
4058                   0 on machines that support more than 32 bits of
4059                   memory space.
4060                   Any positive values less than 2MB will be ignored reset
4061                   to 2MB.
4062                   In a server with multiple views, the limit applies
4063                   separately to the cache of each view.
4064                   The default is 0.
4065                 </p></dd>
4066 <dt><span class="term"><span><strong class="command">tcp-listen-queue</strong></span></span></dt>
4067 <dd><p>
4068                   The listen queue depth.  The default and minimum is 3.
4069                   If the kernel supports the accept filter "dataready" this
4070                   also controls how
4071                   many TCP connections that will be queued in kernel space
4072                   waiting for
4073                   some data before being passed to accept.  Values less than 3
4074                   will be
4075                   silently raised.
4076                 </p></dd>
4077 </dl></div>
4078 </div>
4079 <div class="sect3" lang="en">
4080 <div class="titlepage"><div><div><h4 class="title">
4081 <a name="id2584065"></a>Periodic Task Intervals</h4></div></div></div>
4082 <div class="variablelist"><dl>
4083 <dt><span class="term"><span><strong class="command">cleaning-interval</strong></span></span></dt>
4084 <dd><p>
4085                   This interval is effectively obsolete.  Previously,
4086                   the server would remove expired resource records
4087                   from the cache every <span><strong class="command">cleaning-interval</strong></span> minutes.
4088                   <acronym class="acronym">BIND</acronym> 9 now manages cache
4089                   memory in a more sophisticated manner and does not
4090                   rely on the periodic cleaning any more.
4091                   Specifying this option therefore has no effect on
4092                   the server's behavior.
4093                 </p></dd>
4094 <dt><span class="term"><span><strong class="command">heartbeat-interval</strong></span></span></dt>
4095 <dd><p>
4096                   The server will perform zone maintenance tasks
4097                   for all zones marked as <span><strong class="command">dialup</strong></span> whenever this
4098                   interval expires. The default is 60 minutes. Reasonable
4099                   values are up
4100                   to 1 day (1440 minutes).  The maximum value is 28 days
4101                   (40320 minutes).
4102                   If set to 0, no zone maintenance for these zones will occur.
4103                 </p></dd>
4104 <dt><span class="term"><span><strong class="command">interface-interval</strong></span></span></dt>
4105 <dd><p>
4106                   The server will scan the network interface list
4107                   every <span><strong class="command">interface-interval</strong></span>
4108                   minutes. The default
4109                   is 60 minutes. The maximum value is 28 days (40320 minutes).
4110                   If set to 0, interface scanning will only occur when
4111                   the configuration file is  loaded. After the scan, the
4112                   server will
4113                   begin listening for queries on any newly discovered
4114                   interfaces (provided they are allowed by the
4115                   <span><strong class="command">listen-on</strong></span> configuration), and
4116                   will
4117                   stop listening on interfaces that have gone away.
4118                 </p></dd>
4119 <dt><span class="term"><span><strong class="command">statistics-interval</strong></span></span></dt>
4120 <dd>
4121 <p>
4122                   Name server statistics will be logged
4123                   every <span><strong class="command">statistics-interval</strong></span>
4124                   minutes. The default is
4125                   60. The maximum value is 28 days (40320 minutes).
4126                   If set to 0, no statistics will be logged.
4127                   </p>
4128 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4129 <h3 class="title">Note</h3>
4130 <p>
4131                     Not yet implemented in
4132                     <acronym class="acronym">BIND</acronym> 9.
4133                   </p>
4134 </div>
4135 </dd>
4136 </dl></div>
4137 </div>
4138 <div class="sect3" lang="en">
4139 <div class="titlepage"><div><div><h4 class="title">
4140 <a name="topology"></a>Topology</h4></div></div></div>
4141 <p>
4142             All other things being equal, when the server chooses a name
4143             server
4144             to query from a list of name servers, it prefers the one that is
4145             topologically closest to itself. The <span><strong class="command">topology</strong></span> statement
4146             takes an <span><strong class="command">address_match_list</strong></span> and
4147             interprets it
4148             in a special way. Each top-level list element is assigned a
4149             distance.
4150             Non-negated elements get a distance based on their position in the
4151             list, where the closer the match is to the start of the list, the
4152             shorter the distance is between it and the server. A negated match
4153             will be assigned the maximum distance from the server. If there
4154             is no match, the address will get a distance which is further than
4155             any non-negated list element, and closer than any negated element.
4156             For example,
4157           </p>
4158 <pre class="programlisting">topology {
4159     10/8;
4160     !1.2.3/24;
4161     { 1.2/16; 3/8; };
4162 };</pre>
4163 <p>
4164             will prefer servers on network 10 the most, followed by hosts
4165             on network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the
4166             exception of hosts on network 1.2.3 (netmask 255.255.255.0), which
4167             is preferred least of all.
4168           </p>
4169 <p>
4170             The default topology is
4171           </p>
4172 <pre class="programlisting">    topology { localhost; localnets; };
4173 </pre>
4174 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4175 <h3 class="title">Note</h3>
4176 <p>
4177               The <span><strong class="command">topology</strong></span> option
4178               is not implemented in <acronym class="acronym">BIND</acronym> 9.
4179             </p>
4180 </div>
4181 </div>
4182 <div class="sect3" lang="en">
4183 <div class="titlepage"><div><div><h4 class="title">
4184 <a name="the_sortlist_statement"></a>The <span><strong class="command">sortlist</strong></span> Statement</h4></div></div></div>
4185 <p>
4186             The response to a DNS query may consist of multiple resource
4187             records (RRs) forming a resource records set (RRset).
4188             The name server will normally return the
4189             RRs within the RRset in an indeterminate order
4190             (but see the <span><strong class="command">rrset-order</strong></span>
4191             statement in <a href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">the section called &#8220;RRset Ordering&#8221;</a>).
4192             The client resolver code should rearrange the RRs as appropriate,
4193             that is, using any addresses on the local net in preference to
4194             other addresses.
4195             However, not all resolvers can do this or are correctly
4196             configured.
4197             When a client is using a local server, the sorting can be performed
4198             in the server, based on the client's address. This only requires
4199             configuring the name servers, not all the clients.
4200           </p>
4201 <p>
4202             The <span><strong class="command">sortlist</strong></span> statement (see below)
4203             takes
4204             an <span><strong class="command">address_match_list</strong></span> and
4205             interprets it even
4206             more specifically than the <span><strong class="command">topology</strong></span>
4207             statement
4208             does (<a href="Bv9ARM.ch06.html#topology" title="Topology">the section called &#8220;Topology&#8221;</a>).
4209             Each top level statement in the <span><strong class="command">sortlist</strong></span> must
4210             itself be an explicit <span><strong class="command">address_match_list</strong></span> with
4211             one or two elements. The first element (which may be an IP
4212             address,
4213             an IP prefix, an ACL name or a nested <span><strong class="command">address_match_list</strong></span>)
4214             of each top level list is checked against the source address of
4215             the query until a match is found.
4216           </p>
4217 <p>
4218             Once the source address of the query has been matched, if
4219             the top level statement contains only one element, the actual
4220             primitive
4221             element that matched the source address is used to select the
4222             address
4223             in the response to move to the beginning of the response. If the
4224             statement is a list of two elements, then the second element is
4225             treated the same as the <span><strong class="command">address_match_list</strong></span> in
4226             a <span><strong class="command">topology</strong></span> statement. Each top
4227             level element
4228             is assigned a distance and the address in the response with the
4229             minimum
4230             distance is moved to the beginning of the response.
4231           </p>
4232 <p>
4233             In the following example, any queries received from any of
4234             the addresses of the host itself will get responses preferring
4235             addresses
4236             on any of the locally connected networks. Next most preferred are
4237             addresses
4238             on the 192.168.1/24 network, and after that either the
4239             192.168.2/24
4240             or
4241             192.168.3/24 network with no preference shown between these two
4242             networks. Queries received from a host on the 192.168.1/24 network
4243             will prefer other addresses on that network to the 192.168.2/24
4244             and
4245             192.168.3/24 networks. Queries received from a host on the
4246             192.168.4/24
4247             or the 192.168.5/24 network will only prefer other addresses on
4248             their directly connected networks.
4249           </p>
4250 <pre class="programlisting">sortlist {
4251     { localhost;                                   // IF   the local host
4252         { localnets;                               // THEN first fit on the
4253             192.168.1/24;                          //   following nets
4254             { 192.168.2/24; 192.168.3/24; }; }; };
4255     { 192.168.1/24;                                // IF   on class C 192.168.1
4256         { 192.168.1/24;                            // THEN use .1, or .2 or .3
4257             { 192.168.2/24; 192.168.3/24; }; }; };
4258     { 192.168.2/24;                                // IF   on class C 192.168.2
4259         { 192.168.2/24;                            // THEN use .2, or .1 or .3
4260             { 192.168.1/24; 192.168.3/24; }; }; };
4261     { 192.168.3/24;                                // IF   on class C 192.168.3
4262         { 192.168.3/24;                            // THEN use .3, or .1 or .2
4263             { 192.168.1/24; 192.168.2/24; }; }; };
4264     { { 192.168.4/24; 192.168.5/24; };             // if .4 or .5, prefer that net
4265     };
4266 };</pre>
4267 <p>
4268             The following example will give reasonable behavior for the
4269             local host and hosts on directly connected networks. It is similar
4270             to the behavior of the address sort in <acronym class="acronym">BIND</acronym> 4.9.x. Responses sent
4271             to queries from the local host will favor any of the directly
4272             connected
4273             networks. Responses sent to queries from any other hosts on a
4274             directly
4275             connected network will prefer addresses on that same network.
4276             Responses
4277             to other queries will not be sorted.
4278           </p>
4279 <pre class="programlisting">sortlist {
4280            { localhost; localnets; };
4281            { localnets; };
4282 };
4283 </pre>
4284 </div>
4285 <div class="sect3" lang="en">
4286 <div class="titlepage"><div><div><h4 class="title">
4287 <a name="rrset_ordering"></a>RRset Ordering</h4></div></div></div>
4288 <p>
4289             When multiple records are returned in an answer it may be
4290             useful to configure the order of the records placed into the
4291             response.
4292             The <span><strong class="command">rrset-order</strong></span> statement permits
4293             configuration
4294             of the ordering of the records in a multiple record response.
4295             See also the <span><strong class="command">sortlist</strong></span> statement,
4296             <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>.
4297           </p>
4298 <p>
4299             An <span><strong class="command">order_spec</strong></span> is defined as
4300             follows:
4301           </p>
4302 <p>
4303             [<span class="optional">class <em class="replaceable"><code>class_name</code></em></span>]
4304             [<span class="optional">type <em class="replaceable"><code>type_name</code></em></span>]
4305             [<span class="optional">name <em class="replaceable"><code>"domain_name"</code></em></span>]
4306             order <em class="replaceable"><code>ordering</code></em>
4307           </p>
4308 <p>
4309             If no class is specified, the default is <span><strong class="command">ANY</strong></span>.
4310             If no type is specified, the default is <span><strong class="command">ANY</strong></span>.
4311             If no name is specified, the default is "<span><strong class="command">*</strong></span>" (asterisk).
4312           </p>
4313 <p>
4314             The legal values for <span><strong class="command">ordering</strong></span> are:
4315           </p>
4316 <div class="informaltable"><table border="1">
4317 <colgroup>
4318 <col>
4319 <col>
4320 </colgroup>
4321 <tbody>
4322 <tr>
4323 <td>
4324                     <p><span><strong class="command">fixed</strong></span></p>
4325                   </td>
4326 <td>
4327                     <p>
4328                       Records are returned in the order they
4329                       are defined in the zone file.
4330                     </p>
4331                   </td>
4332 </tr>
4333 <tr>
4334 <td>
4335                     <p><span><strong class="command">random</strong></span></p>
4336                   </td>
4337 <td>
4338                     <p>
4339                       Records are returned in some random order.
4340                     </p>
4341                   </td>
4342 </tr>
4343 <tr>
4344 <td>
4345                     <p><span><strong class="command">cyclic</strong></span></p>
4346                   </td>
4347 <td>
4348                     <p>
4349                       Records are returned in a cyclic round-robin order.
4350                     </p>
4351                     <p>
4352                       If <acronym class="acronym">BIND</acronym> is configured with the
4353                       "--enable-fixed-rrset" option at compile time, then
4354                       the initial ordering of the RRset will match the
4355                       one specified in the zone file.
4356                     </p>
4357                   </td>
4358 </tr>
4359 </tbody>
4360 </table></div>
4361 <p>
4362             For example:
4363           </p>
4364 <pre class="programlisting">rrset-order {
4365    class IN type A name "host.example.com" order random;
4366    order cyclic;
4367 };
4368 </pre>
4369 <p>
4370             will cause any responses for type A records in class IN that
4371             have "<code class="literal">host.example.com</code>" as a
4372             suffix, to always be returned
4373             in random order. All other records are returned in cyclic order.
4374           </p>
4375 <p>
4376             If multiple <span><strong class="command">rrset-order</strong></span> statements
4377             appear,
4378             they are not combined &#8212; the last one applies.
4379           </p>
4380 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4381 <h3 class="title">Note</h3>
4382 <p>
4383               In this release of <acronym class="acronym">BIND</acronym> 9, the
4384               <span><strong class="command">rrset-order</strong></span> statement does not support
4385               "fixed" ordering by default.  Fixed ordering can be enabled
4386               at compile time by specifying "--enable-fixed-rrset" on
4387               the "configure" command line.
4388             </p>
4389 </div>
4390 </div>
4391 <div class="sect3" lang="en">
4392 <div class="titlepage"><div><div><h4 class="title">
4393 <a name="tuning"></a>Tuning</h4></div></div></div>
4394 <div class="variablelist"><dl>
4395 <dt><span class="term"><span><strong class="command">lame-ttl</strong></span></span></dt>
4396 <dd><p>
4397                   Sets the number of seconds to cache a
4398                   lame server indication. 0 disables caching. (This is
4399                   <span class="bold"><strong>NOT</strong></span> recommended.)
4400                   The default is <code class="literal">600</code> (10 minutes) and the
4401                   maximum value is
4402                   <code class="literal">1800</code> (30 minutes).
4403                 </p></dd>
4404 <dt><span class="term"><span><strong class="command">max-ncache-ttl</strong></span></span></dt>
4405 <dd><p>
4406                   To reduce network traffic and increase performance,
4407                   the server stores negative answers. <span><strong class="command">max-ncache-ttl</strong></span> is
4408                   used to set a maximum retention time for these answers in
4409                   the server
4410                   in seconds. The default
4411                   <span><strong class="command">max-ncache-ttl</strong></span> is <code class="literal">10800</code> seconds (3 hours).
4412                   <span><strong class="command">max-ncache-ttl</strong></span> cannot exceed
4413                   7 days and will
4414                   be silently truncated to 7 days if set to a greater value.
4415                 </p></dd>
4416 <dt><span class="term"><span><strong class="command">max-cache-ttl</strong></span></span></dt>
4417 <dd><p>
4418                   Sets the maximum time for which the server will
4419                   cache ordinary (positive) answers. The default is
4420                   one week (7 days).
4421                   A value of zero may cause all queries to return
4422                   SERVFAIL, because of lost caches of intermediate
4423                   RRsets (such as NS and glue AAAA/A records) in the
4424                   resolution process.
4425                 </p></dd>
4426 <dt><span class="term"><span><strong class="command">min-roots</strong></span></span></dt>
4427 <dd>
4428 <p>
4429                   The minimum number of root servers that
4430                   is required for a request for the root servers to be
4431                   accepted. The default
4432                   is <strong class="userinput"><code>2</code></strong>.
4433                 </p>
4434 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4435 <h3 class="title">Note</h3>
4436 <p>
4437                     Not implemented in <acronym class="acronym">BIND</acronym> 9.
4438                   </p>
4439 </div>
4440 </dd>
4441 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
4442 <dd>
4443 <p>
4444                   Specifies the number of days into the future when
4445                   DNSSEC signatures automatically generated as a
4446                   result of dynamic updates (<a href="Bv9ARM.ch04.html#dynamic_update" title="Dynamic Update">the section called &#8220;Dynamic Update&#8221;</a>) will expire.  There
4447                   is a optional second field which specifies how
4448                   long before expiry that the signatures will be
4449                   regenerated.  If not specified, the signatures will
4450                   be regenerated at 1/4 of base interval.  The second
4451                   field is specified in days if the base interval is
4452                   greater than 7 days otherwise it is specified in hours.
4453                   The default base interval is <code class="literal">30</code> days
4454                   giving a re-signing interval of 7 1/2 days.  The maximum
4455                   values are 10 years (3660 days).
4456                 </p>
4457 <p>
4458                   The signature inception time is unconditionally
4459                   set to one hour before the current time to allow
4460                   for a limited amount of clock skew.
4461                 </p>
4462 <p>
4463                   The <span><strong class="command">sig-validity-interval</strong></span>
4464                   should be, at least, several multiples of the SOA
4465                   expire interval to allow for reasonable interaction
4466                   between the various timer and expiry dates.
4467                 </p>
4468 </dd>
4469 <dt><span class="term"><span><strong class="command">sig-signing-nodes</strong></span></span></dt>
4470 <dd><p>
4471                   Specify the maximum number of nodes to be
4472                   examined in each quantum when signing a zone with
4473                   a new DNSKEY. The default is
4474                   <code class="literal">100</code>.
4475                 </p></dd>
4476 <dt><span class="term"><span><strong class="command">sig-signing-signatures</strong></span></span></dt>
4477 <dd><p>
4478                   Specify a threshold number of signatures that
4479                   will terminate processing a quantum when signing
4480                   a zone with a new DNSKEY.  The default is
4481                   <code class="literal">10</code>.
4482                 </p></dd>
4483 <dt><span class="term"><span><strong class="command">sig-signing-type</strong></span></span></dt>
4484 <dd>
4485 <p>
4486                   Specify a private RDATA type to be used when generating
4487                   key signing records.  The default is
4488                   <code class="literal">65535</code>.
4489                 </p>
4490 <p>
4491                   It is expected that this parameter may be removed
4492                   in a future version once there is a standard type.
4493                 </p>
4494 </dd>
4495 <dt>
4496 <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>
4497 </dt>
4498 <dd>
4499 <p>
4500                   These options control the server's behavior on refreshing a
4501                   zone
4502                   (querying for SOA changes) or retrying failed transfers.
4503                   Usually the SOA values for the zone are used, but these
4504                   values
4505                   are set by the master, giving slave server administrators
4506                   little
4507                   control over their contents.
4508                 </p>
4509 <p>
4510                   These options allow the administrator to set a minimum and
4511                   maximum
4512                   refresh and retry time either per-zone, per-view, or
4513                   globally.
4514                   These options are valid for slave and stub zones,
4515                   and clamp the SOA refresh and retry times to the specified
4516                   values.
4517                 </p>
4518 </dd>
4519 <dt><span class="term"><span><strong class="command">edns-udp-size</strong></span></span></dt>
4520 <dd><p>
4521                   Sets the advertised EDNS UDP buffer size in bytes
4522                   to control the size of packets received.
4523                   Valid values are 512 to 4096 (values outside this range
4524                   will be silently adjusted).  The default value
4525                   is 4096.  The usual reason for setting
4526                   <span><strong class="command">edns-udp-size</strong></span> to a non-default
4527                   value is to get UDP answers to pass through broken
4528                   firewalls that block fragmented packets and/or
4529                   block UDP packets that are greater than 512 bytes.
4530                 </p></dd>
4531 <dt><span class="term"><span><strong class="command">max-udp-size</strong></span></span></dt>
4532 <dd><p>
4533                   Sets the maximum EDNS UDP message size <span><strong class="command">named</strong></span> will
4534                   send in bytes.  Valid values are 512 to 4096 (values outside
4535                   this range will be silently adjusted).  The default
4536                   value is 4096.  The usual reason for setting
4537                   <span><strong class="command">max-udp-size</strong></span> to a non-default value is to get UDP
4538                   answers to pass through broken firewalls that
4539                   block fragmented packets and/or block UDP packets
4540                   that are greater than 512 bytes.
4541                   This is independent of the advertised receive
4542                   buffer (<span><strong class="command">edns-udp-size</strong></span>).
4543                 </p></dd>
4544 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
4545 <dd><p>Specifies
4546                   the file format of zone files (see
4547                   <a href="Bv9ARM.ch06.html#zonefile_format" title="Additional File Formats">the section called &#8220;Additional File Formats&#8221;</a>).
4548                   The default value is <code class="constant">text</code>, which is the
4549                   standard textual representation.  Files in other formats
4550                   than <code class="constant">text</code> are typically expected
4551                   to be generated by the <span><strong class="command">named-compilezone</strong></span> tool.
4552                   Note that when a zone file in a different format than
4553                   <code class="constant">text</code> is loaded, <span><strong class="command">named</strong></span>
4554                   may omit some of the checks which would be performed for a
4555                   file in the <code class="constant">text</code> format.  In particular,
4556                   <span><strong class="command">check-names</strong></span> checks do not apply
4557                   for the <code class="constant">raw</code> format.  This means
4558                   a zone file in the <code class="constant">raw</code> format
4559                   must be generated with the same check level as that
4560                   specified in the <span><strong class="command">named</strong></span> configuration
4561                   file.  This statement sets the
4562                   <span><strong class="command">masterfile-format</strong></span> for all zones,
4563                   but can be overridden on a per-zone or per-view basis
4564                   by including a <span><strong class="command">masterfile-format</strong></span>
4565                   statement within the <span><strong class="command">zone</strong></span> or
4566                   <span><strong class="command">view</strong></span> block in the configuration
4567                   file.
4568                 </p></dd>
4569 <dt>
4570 <a name="clients-per-query"></a><span class="term"><span><strong class="command">clients-per-query</strong></span>, </span><span class="term"><span><strong class="command">max-clients-per-query</strong></span></span>
4571 </dt>
4572 <dd>
4573 <p>These set the
4574                   initial value (minimum) and maximum number of recursive
4575                   simultaneous clients for any given query
4576                   (&lt;qname,qtype,qclass&gt;) that the server will accept
4577                   before dropping additional clients.  <span><strong class="command">named</strong></span> will attempt to
4578                   self tune this value and changes will be logged.  The
4579                   default values are 10 and 100.
4580                 </p>
4581 <p>
4582                   This value should reflect how many queries come in for
4583                   a given name in the time it takes to resolve that name.
4584                   If the number of queries exceed this value, <span><strong class="command">named</strong></span> will
4585                   assume that it is dealing with a non-responsive zone
4586                   and will drop additional queries.  If it gets a response
4587                   after dropping queries, it will raise the estimate.  The
4588                   estimate will then be lowered in 20 minutes if it has
4589                   remained unchanged.
4590                 </p>
4591 <p>
4592                   If <span><strong class="command">clients-per-query</strong></span> is set to zero,
4593                   then there is no limit on the number of clients per query
4594                   and no queries will be dropped.
4595                 </p>
4596 <p>
4597                   If <span><strong class="command">max-clients-per-query</strong></span> is set to zero,
4598                   then there is no upper bound other than imposed by
4599                   <span><strong class="command">recursive-clients</strong></span>.
4600                 </p>
4601 </dd>
4602 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
4603 <dd><p>
4604                   The delay, in seconds, between sending sets of notify
4605                   messages for a zone.  The default is zero.
4606                 </p></dd>
4607 </dl></div>
4608 </div>
4609 <div class="sect3" lang="en">
4610 <div class="titlepage"><div><div><h4 class="title">
4611 <a name="builtin"></a>Built-in server information zones</h4></div></div></div>
4612 <p>
4613             The server provides some helpful diagnostic information
4614             through a number of built-in zones under the
4615             pseudo-top-level-domain <code class="literal">bind</code> in the
4616             <span><strong class="command">CHAOS</strong></span> class.  These zones are part
4617             of a
4618             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
4619             class
4620             <span><strong class="command">CHAOS</strong></span> which is separate from the
4621             default view of
4622             class <span><strong class="command">IN</strong></span>; therefore, any global
4623             server options
4624             such as <span><strong class="command">allow-query</strong></span> do not apply
4625             the these zones.
4626             If you feel the need to disable these zones, use the options
4627             below, or hide the built-in <span><strong class="command">CHAOS</strong></span>
4628             view by
4629             defining an explicit view of class <span><strong class="command">CHAOS</strong></span>
4630             that matches all clients.
4631           </p>
4632 <div class="variablelist"><dl>
4633 <dt><span class="term"><span><strong class="command">version</strong></span></span></dt>
4634 <dd><p>
4635                   The version the server should report
4636                   via a query of the name <code class="literal">version.bind</code>
4637                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
4638                   The default is the real version number of this server.
4639                   Specifying <span><strong class="command">version none</strong></span>
4640                   disables processing of the queries.
4641                 </p></dd>
4642 <dt><span class="term"><span><strong class="command">hostname</strong></span></span></dt>
4643 <dd><p>
4644                   The hostname the server should report via a query of
4645                   the name <code class="filename">hostname.bind</code>
4646                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
4647                   This defaults to the hostname of the machine hosting the
4648                   name server as
4649                   found by the gethostname() function.  The primary purpose of such queries
4650                   is to
4651                   identify which of a group of anycast servers is actually
4652                   answering your queries.  Specifying <span><strong class="command">hostname none;</strong></span>
4653                   disables processing of the queries.
4654                 </p></dd>
4655 <dt><span class="term"><span><strong class="command">server-id</strong></span></span></dt>
4656 <dd><p>
4657                   The ID the server should report when receiving a Name
4658                   Server Identifier (NSID) query, or a query of the name
4659                   <code class="filename">ID.SERVER</code> with type
4660                   <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
4661                   The primary purpose of such queries is to
4662                   identify which of a group of anycast servers is actually
4663                   answering your queries.  Specifying <span><strong class="command">server-id none;</strong></span>
4664                   disables processing of the queries.
4665                   Specifying <span><strong class="command">server-id hostname;</strong></span> will cause <span><strong class="command">named</strong></span> to
4666                   use the hostname as found by the gethostname() function.
4667                   The default <span><strong class="command">server-id</strong></span> is <span><strong class="command">none</strong></span>.
4668                 </p></dd>
4669 </dl></div>
4670 </div>
4671 <div class="sect3" lang="en">
4672 <div class="titlepage"><div><div><h4 class="title">
4673 <a name="empty"></a>Built-in Empty Zones</h4></div></div></div>
4674 <p>
4675             Named has some built-in empty zones (SOA and NS records only).
4676             These are for zones that should normally be answered locally
4677             and which queries should not be sent to the Internet's root
4678             servers.  The official servers which cover these namespaces
4679             return NXDOMAIN responses to these queries.  In particular,
4680             these cover the reverse namespace for addresses from RFC 1918 and
4681             RFC 3330.  They also include the reverse namespace for IPv6 local
4682             address (locally assigned), IPv6 link local addresses, the IPv6
4683             loopback address and the IPv6 unknown address.
4684           </p>
4685 <p>
4686             Named will attempt to determine if a built-in zone already exists
4687             or is active (covered by a forward-only forwarding declaration)
4688             and will not create a empty zone in that case.
4689           </p>
4690 <p>
4691             The current list of empty zones is:
4692             </p>
4693 <div class="itemizedlist"><ul type="disc">
4694 <li>0.IN-ADDR.ARPA</li>
4695 <li>127.IN-ADDR.ARPA</li>
4696 <li>254.169.IN-ADDR.ARPA</li>
4697 <li>2.0.192.IN-ADDR.ARPA</li>
4698 <li>255.255.255.255.IN-ADDR.ARPA</li>
4699 <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>
4700 <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>
4701 <li>D.F.IP6.ARPA</li>
4702 <li>8.E.F.IP6.ARPA</li>
4703 <li>9.E.F.IP6.ARPA</li>
4704 <li>A.E.F.IP6.ARPA</li>
4705 <li>B.E.F.IP6.ARPA</li>
4706 </ul></div>
4707 <p>
4708           </p>
4709 <p>
4710             Empty zones are settable at the view level and only apply to
4711             views of class IN.  Disabled empty zones are only inherited
4712             from options if there are no disabled empty zones specified
4713             at the view level.  To override the options list of disabled
4714             zones, you can disable the root zone at the view level, for example:
4715 </p>
4716 <pre class="programlisting">
4717             disable-empty-zone ".";
4718 </pre>
4719 <p>
4720           </p>
4721 <p>
4722             If you are using the address ranges covered here, you should
4723             already have reverse zones covering the addresses you use.
4724             In practice this appears to not be the case with many queries
4725             being made to the infrastructure servers for names in these
4726             spaces.  So many in fact that sacrificial servers were needed
4727             to be deployed to channel the query load away from the
4728             infrastructure servers.
4729           </p>
4730 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4731 <h3 class="title">Note</h3>
4732             The real parent servers for these zones should disable all
4733             empty zone under the parent zone they serve.  For the real
4734             root servers, this is all built-in empty zones.  This will
4735             enable them to return referrals to deeper in the tree.
4736           </div>
4737 <div class="variablelist"><dl>
4738 <dt><span class="term"><span><strong class="command">empty-server</strong></span></span></dt>
4739 <dd><p>
4740                   Specify what server name will appear in the returned
4741                   SOA record for empty zones.  If none is specified, then
4742                   the zone's name will be used.
4743                 </p></dd>
4744 <dt><span class="term"><span><strong class="command">empty-contact</strong></span></span></dt>
4745 <dd><p>
4746                   Specify what contact name will appear in the returned
4747                   SOA record for empty zones.  If none is specified, then
4748                   "." will be used.
4749                 </p></dd>
4750 <dt><span class="term"><span><strong class="command">empty-zones-enable</strong></span></span></dt>
4751 <dd><p>
4752                   Enable or disable all empty zones.  By default, they
4753                   are enabled.
4754                 </p></dd>
4755 <dt><span class="term"><span><strong class="command">disable-empty-zone</strong></span></span></dt>
4756 <dd><p>
4757                   Disable individual empty zones.  By default, none are
4758                   disabled.  This option can be specified multiple times.
4759                 </p></dd>
4760 </dl></div>
4761 </div>
4762 <div class="sect3" lang="en">
4763 <div class="titlepage"><div><div><h4 class="title">
4764 <a name="acache"></a>Additional Section Caching</h4></div></div></div>
4765 <p>
4766             The additional section cache, also called <span><strong class="command">acache</strong></span>,
4767             is an internal cache to improve the response performance of BIND 9.
4768             When additional section caching is enabled, BIND 9 will
4769             cache an internal short-cut to the additional section content for
4770             each answer RR.
4771             Note that <span><strong class="command">acache</strong></span> is an internal caching
4772             mechanism of BIND 9, and is not related to the DNS caching
4773             server function.
4774           </p>
4775 <p>
4776             Additional section caching does not change the
4777             response content (except the RRsets ordering of the additional
4778             section, see below), but can improve the response performance
4779             significantly.
4780             It is particularly effective when BIND 9 acts as an authoritative
4781             server for a zone that has many delegations with many glue RRs.
4782           </p>
4783 <p>
4784             In order to obtain the maximum performance improvement
4785             from additional section caching, setting
4786             <span><strong class="command">additional-from-cache</strong></span>
4787             to <span><strong class="command">no</strong></span> is recommended, since the current
4788             implementation of <span><strong class="command">acache</strong></span>
4789             does not short-cut of additional section information from the
4790             DNS cache data.
4791           </p>
4792 <p>
4793             One obvious disadvantage of <span><strong class="command">acache</strong></span> is
4794             that it requires much more
4795             memory for the internal cached data.
4796             Thus, if the response performance does not matter and memory
4797             consumption is much more critical, the
4798             <span><strong class="command">acache</strong></span> mechanism can be
4799             disabled by setting <span><strong class="command">acache-enable</strong></span> to
4800             <span><strong class="command">no</strong></span>.
4801             It is also possible to specify the upper limit of memory
4802             consumption
4803             for acache by using <span><strong class="command">max-acache-size</strong></span>.
4804           </p>
4805 <p>
4806             Additional section caching also has a minor effect on the
4807             RRset ordering in the additional section.
4808             Without <span><strong class="command">acache</strong></span>,
4809             <span><strong class="command">cyclic</strong></span> order is effective for the additional
4810             section as well as the answer and authority sections.
4811             However, additional section caching fixes the ordering when it
4812             first caches an RRset for the additional section, and the same
4813             ordering will be kept in succeeding responses, regardless of the
4814             setting of <span><strong class="command">rrset-order</strong></span>.
4815             The effect of this should be minor, however, since an
4816             RRset in the additional section
4817             typically only contains a small number of RRs (and in many cases
4818             it only contains a single RR), in which case the
4819             ordering does not matter much.
4820           </p>
4821 <p>
4822             The following is a summary of options related to
4823             <span><strong class="command">acache</strong></span>.
4824           </p>
4825 <div class="variablelist"><dl>
4826 <dt><span class="term"><span><strong class="command">acache-enable</strong></span></span></dt>
4827 <dd><p>
4828                   If <span><strong class="command">yes</strong></span>, additional section caching is
4829                   enabled.  The default value is <span><strong class="command">no</strong></span>.
4830                 </p></dd>
4831 <dt><span class="term"><span><strong class="command">acache-cleaning-interval</strong></span></span></dt>
4832 <dd><p>
4833                   The server will remove stale cache entries, based on an LRU
4834                   based
4835                   algorithm, every <span><strong class="command">acache-cleaning-interval</strong></span> minutes.
4836                   The default is 60 minutes.
4837                   If set to 0, no periodic cleaning will occur.
4838                 </p></dd>
4839 <dt><span class="term"><span><strong class="command">max-acache-size</strong></span></span></dt>
4840 <dd><p>
4841                   The maximum amount of memory in bytes to use for the server's acache.
4842                   When the amount of data in the acache reaches this limit,
4843                   the server
4844                   will clean more aggressively so that the limit is not
4845                   exceeded.
4846                   In a server with multiple views, the limit applies
4847                   separately to the
4848                   acache of each view.
4849                   The default is <code class="literal">16M</code>.
4850                 </p></dd>
4851 </dl></div>
4852 </div>
4853 </div>
4854 <div class="sect2" lang="en">
4855 <div class="titlepage"><div><div><h3 class="title">
4856 <a name="server_statement_grammar"></a><span><strong class="command">server</strong></span> Statement Grammar</h3></div></div></div>
4857 <pre class="programlisting"><span><strong class="command">server</strong></span> <em class="replaceable"><code>ip_addr[/prefixlen]</code></em> {
4858     [<span class="optional"> bogus <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4859     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4860     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4861     [<span class="optional"> edns <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4862     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
4863     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
4864     [<span class="optional"> transfers <em class="replaceable"><code>number</code></em> ; </span>]
4865     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em> ; ]</span>]
4866     [<span class="optional"> keys <em class="replaceable"><code>{ string ; [<span class="optional"> string ; [<span class="optional">...</span>]</span>] }</code></em> ; </span>]
4867     [<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>]
4868     [<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>]
4869     [<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>]
4870     [<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>]
4871     [<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>]
4872     [<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>]
4873     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
4874     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
4875     [<span class="optional"> queryport-pool-interval <em class="replaceable"><code>number</code></em>; </span>]
4876 };
4877 </pre>
4878 </div>
4879 <div class="sect2" lang="en">
4880 <div class="titlepage"><div><div><h3 class="title">
4881 <a name="server_statement_definition_and_usage"></a><span><strong class="command">server</strong></span> Statement Definition and
4882             Usage</h3></div></div></div>
4883 <p>
4884             The <span><strong class="command">server</strong></span> statement defines
4885             characteristics
4886             to be associated with a remote name server.  If a prefix length is
4887             specified, then a range of servers is covered.  Only the most
4888             specific
4889             server clause applies regardless of the order in
4890             <code class="filename">named.conf</code>.
4891           </p>
4892 <p>
4893             The <span><strong class="command">server</strong></span> statement can occur at
4894             the top level of the
4895             configuration file or inside a <span><strong class="command">view</strong></span>
4896             statement.
4897             If a <span><strong class="command">view</strong></span> statement contains
4898             one or more <span><strong class="command">server</strong></span> statements, only
4899             those
4900             apply to the view and any top-level ones are ignored.
4901             If a view contains no <span><strong class="command">server</strong></span>
4902             statements,
4903             any top-level <span><strong class="command">server</strong></span> statements are
4904             used as
4905             defaults.
4906           </p>
4907 <p>
4908             If you discover that a remote server is giving out bad data,
4909             marking it as bogus will prevent further queries to it. The
4910             default
4911             value of <span><strong class="command">bogus</strong></span> is <span><strong class="command">no</strong></span>.
4912           </p>
4913 <p>
4914             The <span><strong class="command">provide-ixfr</strong></span> clause determines
4915             whether
4916             the local server, acting as master, will respond with an
4917             incremental
4918             zone transfer when the given remote server, a slave, requests it.
4919             If set to <span><strong class="command">yes</strong></span>, incremental transfer
4920             will be provided
4921             whenever possible. If set to <span><strong class="command">no</strong></span>,
4922             all transfers
4923             to the remote server will be non-incremental. If not set, the
4924             value
4925             of the <span><strong class="command">provide-ixfr</strong></span> option in the
4926             view or
4927             global options block is used as a default.
4928           </p>
4929 <p>
4930             The <span><strong class="command">request-ixfr</strong></span> clause determines
4931             whether
4932             the local server, acting as a slave, will request incremental zone
4933             transfers from the given remote server, a master. If not set, the
4934             value of the <span><strong class="command">request-ixfr</strong></span> option in
4935             the view or
4936             global options block is used as a default.
4937           </p>
4938 <p>
4939             IXFR requests to servers that do not support IXFR will
4940             automatically
4941             fall back to AXFR.  Therefore, there is no need to manually list
4942             which servers support IXFR and which ones do not; the global
4943             default
4944             of <span><strong class="command">yes</strong></span> should always work.
4945             The purpose of the <span><strong class="command">provide-ixfr</strong></span> and
4946             <span><strong class="command">request-ixfr</strong></span> clauses is
4947             to make it possible to disable the use of IXFR even when both
4948             master
4949             and slave claim to support it, for example if one of the servers
4950             is buggy and crashes or corrupts data when IXFR is used.
4951           </p>
4952 <p>
4953             The <span><strong class="command">edns</strong></span> clause determines whether
4954             the local server will attempt to use EDNS when communicating
4955             with the remote server.  The default is <span><strong class="command">yes</strong></span>.
4956           </p>
4957 <p>
4958             The <span><strong class="command">edns-udp-size</strong></span> option sets the EDNS UDP size
4959             that is advertised by <span><strong class="command">named</strong></span> when querying the remote server.
4960             Valid values are 512 to 4096 bytes (values outside this range will be
4961             silently adjusted).  This option is useful when you wish to
4962             advertises a different value to this server than the value you
4963             advertise globally, for example, when there is a firewall at the
4964             remote site that is blocking large replies.
4965           </p>
4966 <p>
4967             The <span><strong class="command">max-udp-size</strong></span> option sets the
4968             maximum EDNS UDP message size <span><strong class="command">named</strong></span> will send.  Valid
4969             values are 512 to 4096 bytes (values outside this range will
4970             be silently adjusted).  This option is useful when you
4971             know that there is a firewall that is blocking large
4972             replies from <span><strong class="command">named</strong></span>.
4973           </p>
4974 <p>
4975             The server supports two zone transfer methods. The first, <span><strong class="command">one-answer</strong></span>,
4976             uses one DNS message per resource record transferred. <span><strong class="command">many-answers</strong></span> packs
4977             as many resource records as possible into a message. <span><strong class="command">many-answers</strong></span> is
4978             more efficient, but is only known to be understood by <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
4979             8.x, and patched versions of <acronym class="acronym">BIND</acronym>
4980             4.9.5. You can specify which method
4981             to use for a server with the <span><strong class="command">transfer-format</strong></span> option.
4982             If <span><strong class="command">transfer-format</strong></span> is not
4983             specified, the <span><strong class="command">transfer-format</strong></span>
4984             specified
4985             by the <span><strong class="command">options</strong></span> statement will be
4986             used.
4987           </p>
4988 <p><span><strong class="command">transfers</strong></span>
4989             is used to limit the number of concurrent inbound zone
4990             transfers from the specified server. If no
4991             <span><strong class="command">transfers</strong></span> clause is specified, the
4992             limit is set according to the
4993             <span><strong class="command">transfers-per-ns</strong></span> option.
4994           </p>
4995 <p>
4996             The <span><strong class="command">keys</strong></span> clause identifies a
4997             <span><strong class="command">key_id</strong></span> defined by the <span><strong class="command">key</strong></span> statement,
4998             to be used for transaction security (TSIG, <a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
4999             when talking to the remote server.
5000             When a request is sent to the remote server, a request signature
5001             will be generated using the key specified here and appended to the
5002             message. A request originating from the remote server is not
5003             required
5004             to be signed by this key.
5005           </p>
5006 <p>
5007             Although the grammar of the <span><strong class="command">keys</strong></span>
5008             clause
5009             allows for multiple keys, only a single key per server is
5010             currently
5011             supported.
5012           </p>
5013 <p>
5014             The <span><strong class="command">transfer-source</strong></span> and
5015             <span><strong class="command">transfer-source-v6</strong></span> clauses specify
5016             the IPv4 and IPv6 source
5017             address to be used for zone transfer with the remote server,
5018             respectively.
5019             For an IPv4 remote server, only <span><strong class="command">transfer-source</strong></span> can
5020             be specified.
5021             Similarly, for an IPv6 remote server, only
5022             <span><strong class="command">transfer-source-v6</strong></span> can be
5023             specified.
5024             For more details, see the description of
5025             <span><strong class="command">transfer-source</strong></span> and
5026             <span><strong class="command">transfer-source-v6</strong></span> in
5027             <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
5028           </p>
5029 <p>
5030             The <span><strong class="command">notify-source</strong></span> and
5031             <span><strong class="command">notify-source-v6</strong></span> clauses specify the
5032             IPv4 and IPv6 source address to be used for notify
5033             messages sent to remote servers, respectively.  For an
5034             IPv4 remote server, only <span><strong class="command">notify-source</strong></span>
5035             can be specified.  Similarly, for an IPv6 remote server,
5036             only <span><strong class="command">notify-source-v6</strong></span> can be specified.
5037           </p>
5038 <p>
5039             The <span><strong class="command">query-source</strong></span> and
5040             <span><strong class="command">query-source-v6</strong></span> clauses specify the
5041             IPv4 and IPv6 source address to be used for queries
5042             sent to remote servers, respectively.  For an IPv4
5043             remote server, only <span><strong class="command">query-source</strong></span> can
5044             be specified.  Similarly, for an IPv6 remote server,
5045             only <span><strong class="command">query-source-v6</strong></span> can be specified.
5046           </p>
5047 </div>
5048 <div class="sect2" lang="en">
5049 <div class="titlepage"><div><div><h3 class="title">
5050 <a name="statschannels"></a><span><strong class="command">statistics-channels</strong></span> Statement Grammar</h3></div></div></div>
5051 <pre class="programlisting"><span><strong class="command">statistics-channels</strong></span> {
5052    [ inet ( ip_addr | * ) [ port ip_port ] [allow { <em class="replaceable"><code> address_match_list </code></em> } ]; ]
5053    [ inet ...; ]
5054 };
5055 </pre>
5056 </div>
5057 <div class="sect2" lang="en">
5058 <div class="titlepage"><div><div><h3 class="title">
5059 <a name="id2586902"></a><span><strong class="command">statistics-channels</strong></span> Statement Definition and
5060             Usage</h3></div></div></div>
5061 <p>
5062           The <span><strong class="command">statistics-channels</strong></span> statement
5063           declares communication channels to be used by system
5064           administrators to get access to statistics information of
5065           the name server.
5066         </p>
5067 <p>
5068           This statement intends to be flexible to support multiple
5069           communication protocols in the future, but currently only
5070           HTTP access is supported.
5071           It requires that BIND 9 be compiled with libxml2;
5072           the <span><strong class="command">statistics-channels</strong></span> statement is
5073           still accepted even if it is built without the library,
5074           but any HTTP access will fail with an error.
5075         </p>
5076 <p>
5077           An <span><strong class="command">inet</strong></span> control channel is a TCP socket
5078           listening at the specified <span><strong class="command">ip_port</strong></span> on the
5079           specified <span><strong class="command">ip_addr</strong></span>, which can be an IPv4 or IPv6
5080           address.  An <span><strong class="command">ip_addr</strong></span> of <code class="literal">*</code> (asterisk) is
5081           interpreted as the IPv4 wildcard address; connections will be
5082           accepted on any of the system's IPv4 addresses.
5083           To listen on the IPv6 wildcard address,
5084           use an <span><strong class="command">ip_addr</strong></span> of <code class="literal">::</code>.
5085         </p>
5086 <p>
5087           If no port is specified, port 80 is used for HTTP channels.
5088           The asterisk "<code class="literal">*</code>" cannot be used for
5089           <span><strong class="command">ip_port</strong></span>.
5090         </p>
5091 <p>
5092           The attempt of opening a statistics channel is
5093           restricted by the optional <span><strong class="command">allow</strong></span> clause.
5094           Connections to the statistics channel are permitted based on the
5095           <span><strong class="command">address_match_list</strong></span>.
5096           If no <span><strong class="command">allow</strong></span> clause is present,
5097           <span><strong class="command">named</strong></span> accepts connection
5098           attempts from any address; since the statistics may
5099           contain sensitive internal information, it is highly
5100           recommended to restrict the source of connection requests
5101           appropriately.
5102         </p>
5103 <p>
5104           If no <span><strong class="command">statistics-channels</strong></span> statement is present,
5105           <span><strong class="command">named</strong></span> will not open any communication channels.
5106         </p>
5107 </div>
5108 <div class="sect2" lang="en">
5109 <div class="titlepage"><div><div><h3 class="title">
5110 <a name="id2586988"></a><span><strong class="command">trusted-keys</strong></span> Statement Grammar</h3></div></div></div>
5111 <pre class="programlisting"><span><strong class="command">trusted-keys</strong></span> {
5112     <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> ;
5113     [<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>]
5114 };
5115 </pre>
5116 </div>
5117 <div class="sect2" lang="en">
5118 <div class="titlepage"><div><div><h3 class="title">
5119 <a name="id2587040"></a><span><strong class="command">trusted-keys</strong></span> Statement Definition
5120             and Usage</h3></div></div></div>
5121 <p>
5122             The <span><strong class="command">trusted-keys</strong></span> statement defines
5123             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
5124             public key for a non-authoritative zone is known, but
5125             cannot be securely obtained through DNS, either because
5126             it is the DNS root zone or because its parent zone is
5127             unsigned.  Once a key has been configured as a trusted
5128             key, it is treated as if it had been validated and
5129             proven secure. The resolver attempts DNSSEC validation
5130             on all DNS data in subdomains of a security root.
5131           </p>
5132 <p>
5133             All keys (and corresponding zones) listed in
5134             <span><strong class="command">trusted-keys</strong></span> are deemed to exist regardless
5135             of what parent zones say.  Similarly for all keys listed in
5136             <span><strong class="command">trusted-keys</strong></span> only those keys are
5137             used to validate the DNSKEY RRset.  The parent's DS RRset
5138             will not be used.
5139           </p>
5140 <p>
5141             The <span><strong class="command">trusted-keys</strong></span> statement can contain
5142             multiple key entries, each consisting of the key's
5143             domain name, flags, protocol, algorithm, and the Base-64
5144             representation of the key data.
5145             Spaces, tabs, newlines and carriage returns are ignored
5146             in the key data, so the configuration may be split up into
5147             multiple lines.
5148           </p>
5149 </div>
5150 <div class="sect2" lang="en">
5151 <div class="titlepage"><div><div><h3 class="title">
5152 <a name="view_statement_grammar"></a><span><strong class="command">view</strong></span> Statement Grammar</h3></div></div></div>
5153 <pre class="programlisting"><span><strong class="command">view</strong></span> <em class="replaceable"><code>view_name</code></em>
5154       [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
5155       match-clients { <em class="replaceable"><code>address_match_list</code></em> };
5156       match-destinations { <em class="replaceable"><code>address_match_list</code></em> };
5157       match-recursive-only <em class="replaceable"><code>yes_or_no</code></em> ;
5158       [<span class="optional"> <em class="replaceable"><code>view_option</code></em>; ...</span>]
5159       [<span class="optional"> <em class="replaceable"><code>zone_statement</code></em>; ...</span>]
5160 };
5161 </pre>
5162 </div>
5163 <div class="sect2" lang="en">
5164 <div class="titlepage"><div><div><h3 class="title">
5165 <a name="id2587122"></a><span><strong class="command">view</strong></span> Statement Definition and Usage</h3></div></div></div>
5166 <p>
5167             The <span><strong class="command">view</strong></span> statement is a powerful
5168             feature
5169             of <acronym class="acronym">BIND</acronym> 9 that lets a name server
5170             answer a DNS query differently
5171             depending on who is asking. It is particularly useful for
5172             implementing
5173             split DNS setups without having to run multiple servers.
5174           </p>
5175 <p>
5176             Each <span><strong class="command">view</strong></span> statement defines a view
5177             of the
5178             DNS namespace that will be seen by a subset of clients.  A client
5179             matches
5180             a view if its source IP address matches the
5181             <code class="varname">address_match_list</code> of the view's
5182             <span><strong class="command">match-clients</strong></span> clause and its
5183             destination IP address matches
5184             the <code class="varname">address_match_list</code> of the
5185             view's
5186             <span><strong class="command">match-destinations</strong></span> clause.  If not
5187             specified, both
5188             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
5189             default to matching all addresses.  In addition to checking IP
5190             addresses
5191             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
5192             can also take <span><strong class="command">keys</strong></span> which provide an
5193             mechanism for the
5194             client to select the view.  A view can also be specified
5195             as <span><strong class="command">match-recursive-only</strong></span>, which
5196             means that only recursive
5197             requests from matching clients will match that view.
5198             The order of the <span><strong class="command">view</strong></span> statements is
5199             significant &#8212;
5200             a client request will be resolved in the context of the first
5201             <span><strong class="command">view</strong></span> that it matches.
5202           </p>
5203 <p>
5204             Zones defined within a <span><strong class="command">view</strong></span>
5205             statement will
5206             only be accessible to clients that match the <span><strong class="command">view</strong></span>.
5207             By defining a zone of the same name in multiple views, different
5208             zone data can be given to different clients, for example,
5209             "internal"
5210             and "external" clients in a split DNS setup.
5211           </p>
5212 <p>
5213             Many of the options given in the <span><strong class="command">options</strong></span> statement
5214             can also be used within a <span><strong class="command">view</strong></span>
5215             statement, and then
5216             apply only when resolving queries with that view.  When no
5217             view-specific
5218             value is given, the value in the <span><strong class="command">options</strong></span> statement
5219             is used as a default.  Also, zone options can have default values
5220             specified
5221             in the <span><strong class="command">view</strong></span> statement; these
5222             view-specific defaults
5223             take precedence over those in the <span><strong class="command">options</strong></span> statement.
5224           </p>
5225 <p>
5226             Views are class specific.  If no class is given, class IN
5227             is assumed.  Note that all non-IN views must contain a hint zone,
5228             since only the IN class has compiled-in default hints.
5229           </p>
5230 <p>
5231             If there are no <span><strong class="command">view</strong></span> statements in
5232             the config
5233             file, a default view that matches any client is automatically
5234             created
5235             in class IN. Any <span><strong class="command">zone</strong></span> statements
5236             specified on
5237             the top level of the configuration file are considered to be part
5238             of
5239             this default view, and the <span><strong class="command">options</strong></span>
5240             statement will
5241             apply to the default view. If any explicit <span><strong class="command">view</strong></span>
5242             statements are present, all <span><strong class="command">zone</strong></span>
5243             statements must
5244             occur inside <span><strong class="command">view</strong></span> statements.
5245           </p>
5246 <p>
5247             Here is an example of a typical split DNS setup implemented
5248             using <span><strong class="command">view</strong></span> statements:
5249           </p>
5250 <pre class="programlisting">view "internal" {
5251       // This should match our internal networks.
5252       match-clients { 10.0.0.0/8; };
5253
5254       // Provide recursive service to internal clients only.
5255       recursion yes;
5256
5257       // Provide a complete view of the example.com zone
5258       // including addresses of internal hosts.
5259       zone "example.com" {
5260             type master;
5261             file "example-internal.db";
5262       };
5263 };
5264
5265 view "external" {
5266       // Match all clients not matched by the previous view.
5267       match-clients { any; };
5268
5269       // Refuse recursive service to external clients.
5270       recursion no;
5271
5272       // Provide a restricted view of the example.com zone
5273       // containing only publicly accessible hosts.
5274       zone "example.com" {
5275            type master;
5276            file "example-external.db";
5277       };
5278 };
5279 </pre>
5280 </div>
5281 <div class="sect2" lang="en">
5282 <div class="titlepage"><div><div><h3 class="title">
5283 <a name="zone_statement_grammar"></a><span><strong class="command">zone</strong></span>
5284             Statement Grammar</h3></div></div></div>
5285 <pre class="programlisting"><span><strong class="command">zone</strong></span> <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
5286     type master;
5287     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5288     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5289     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5290     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5291     [<span class="optional"> update-policy { <em class="replaceable"><code>update_policy_rule</code></em> [<span class="optional">...</span>] }; </span>]
5292     [<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>]
5293     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
5294     [<span class="optional"> check-mx (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
5295     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5296     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5297     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
5298     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
5299     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
5300     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
5301     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
5302     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
5303     [<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>]
5304     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
5305     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5306     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
5307     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5308     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
5309     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
5310     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
5311     [<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>]
5312     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
5313     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5314     [<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>]
5315     [<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>]
5316     [<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>]
5317     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5318     [<span class="optional"> sig-validity-interval <em class="replaceable"><code>number</code></em> ; </span>]
5319     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
5320     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
5321     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
5322     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
5323     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
5324     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
5325     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
5326     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
5327     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
5328     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5329 };
5330
5331 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
5332     type slave;
5333     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5334     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5335     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5336     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5337     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5338     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5339     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5340     [<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>]
5341     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
5342     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
5343     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
5344     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
5345     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
5346     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
5347     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
5348     [<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>]
5349     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
5350     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5351     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
5352     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5353     [<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>]
5354     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
5355     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
5356     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
5357     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
5358     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
5359     [<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>]
5360     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
5361     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5362     [<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>]
5363     [<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>]
5364     [<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>]
5365     [<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>]
5366     [<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>]
5367     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5368     [<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>]
5369     [<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>]
5370     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5371     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
5372     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
5373     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
5374     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
5375     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
5376     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5377     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5378 };
5379
5380 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
5381     type hint;
5382     file <em class="replaceable"><code>string</code></em> ;
5383     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5384     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; // Not Implemented. </span>]
5385 };
5386
5387 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
5388     type stub;
5389     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5390     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5391     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
5392     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
5393     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5394     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
5395     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
5396     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
5397     [<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>]
5398     [<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>]
5399     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
5400     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
5401     [<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>]
5402     [<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>]
5403     [<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>]
5404     [<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>]
5405     [<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>]
5406     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5407     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5408     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
5409     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
5410     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
5411     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
5412     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
5413     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5414 };
5415
5416 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
5417     type forward;
5418     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
5419     [<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>]
5420     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5421 };
5422
5423 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
5424     type delegation-only;
5425 };
5426
5427 </pre>
5428 </div>
5429 <div class="sect2" lang="en">
5430 <div class="titlepage"><div><div><h3 class="title">
5431 <a name="id2588659"></a><span><strong class="command">zone</strong></span> Statement Definition and Usage</h3></div></div></div>
5432 <div class="sect3" lang="en">
5433 <div class="titlepage"><div><div><h4 class="title">
5434 <a name="id2588666"></a>Zone Types</h4></div></div></div>
5435 <div class="informaltable"><table border="1">
5436 <colgroup>
5437 <col>
5438 <col>
5439 </colgroup>
5440 <tbody>
5441 <tr>
5442 <td>
5443                       <p>
5444                         <code class="varname">master</code>
5445                       </p>
5446                     </td>
5447 <td>
5448                       <p>
5449                         The server has a master copy of the data
5450                         for the zone and will be able to provide authoritative
5451                         answers for
5452                         it.
5453                       </p>
5454                     </td>
5455 </tr>
5456 <tr>
5457 <td>
5458                       <p>
5459                         <code class="varname">slave</code>
5460                       </p>
5461                     </td>
5462 <td>
5463                       <p>
5464                         A slave zone is a replica of a master
5465                         zone. The <span><strong class="command">masters</strong></span> list
5466                         specifies one or more IP addresses
5467                         of master servers that the slave contacts to update
5468                         its copy of the zone.
5469                         Masters list elements can also be names of other
5470                         masters lists.
5471                         By default, transfers are made from port 53 on the
5472                         servers; this can
5473                         be changed for all servers by specifying a port number
5474                         before the
5475                         list of IP addresses, or on a per-server basis after
5476                         the IP address.
5477                         Authentication to the master can also be done with
5478                         per-server TSIG keys.
5479                         If a file is specified, then the
5480                         replica will be written to this file whenever the zone
5481                         is changed,
5482                         and reloaded from this file on a server restart. Use
5483                         of a file is
5484                         recommended, since it often speeds server startup and
5485                         eliminates
5486                         a needless waste of bandwidth. Note that for large
5487                         numbers (in the
5488                         tens or hundreds of thousands) of zones per server, it
5489                         is best to
5490                         use a two-level naming scheme for zone filenames. For
5491                         example,
5492                         a slave server for the zone <code class="literal">example.com</code> might place
5493                         the zone contents into a file called
5494                         <code class="filename">ex/example.com</code> where <code class="filename">ex/</code> is
5495                         just the first two letters of the zone name. (Most
5496                         operating systems
5497                         behave very slowly if you put 100000 files into
5498                         a single directory.)
5499                       </p>
5500                     </td>
5501 </tr>
5502 <tr>
5503 <td>
5504                       <p>
5505                         <code class="varname">stub</code>
5506                       </p>
5507                     </td>
5508 <td>
5509                       <p>
5510                         A stub zone is similar to a slave zone,
5511                         except that it replicates only the NS records of a
5512                         master zone instead
5513                         of the entire zone. Stub zones are not a standard part
5514                         of the DNS;
5515                         they are a feature specific to the <acronym class="acronym">BIND</acronym> implementation.
5516                       </p>
5517
5518                       <p>
5519                         Stub zones can be used to eliminate the need for glue
5520                         NS record
5521                         in a parent zone at the expense of maintaining a stub
5522                         zone entry and
5523                         a set of name server addresses in <code class="filename">named.conf</code>.
5524                         This usage is not recommended for new configurations,
5525                         and BIND 9
5526                         supports it only in a limited way.
5527                         In <acronym class="acronym">BIND</acronym> 4/8, zone
5528                         transfers of a parent zone
5529                         included the NS records from stub children of that
5530                         zone. This meant
5531                         that, in some cases, users could get away with
5532                         configuring child stubs
5533                         only in the master server for the parent zone. <acronym class="acronym">BIND</acronym>
5534                         9 never mixes together zone data from different zones
5535                         in this
5536                         way. Therefore, if a <acronym class="acronym">BIND</acronym> 9 master serving a parent
5537                         zone has child stub zones configured, all the slave
5538                         servers for the
5539                         parent zone also need to have the same child stub
5540                         zones
5541                         configured.
5542                       </p>
5543
5544                       <p>
5545                         Stub zones can also be used as a way of forcing the
5546                         resolution
5547                         of a given domain to use a particular set of
5548                         authoritative servers.
5549                         For example, the caching name servers on a private
5550                         network using
5551                         RFC1918 addressing may be configured with stub zones
5552                         for
5553                         <code class="literal">10.in-addr.arpa</code>
5554                         to use a set of internal name servers as the
5555                         authoritative
5556                         servers for that domain.
5557                       </p>
5558                     </td>
5559 </tr>
5560 <tr>
5561 <td>
5562                       <p>
5563                         <code class="varname">forward</code>
5564                       </p>
5565                     </td>
5566 <td>
5567                       <p>
5568                         A "forward zone" is a way to configure
5569                         forwarding on a per-domain basis.  A <span><strong class="command">zone</strong></span> statement
5570                         of type <span><strong class="command">forward</strong></span> can
5571                         contain a <span><strong class="command">forward</strong></span>
5572                         and/or <span><strong class="command">forwarders</strong></span>
5573                         statement,
5574                         which will apply to queries within the domain given by
5575                         the zone
5576                         name. If no <span><strong class="command">forwarders</strong></span>
5577                         statement is present or
5578                         an empty list for <span><strong class="command">forwarders</strong></span> is given, then no
5579                         forwarding will be done for the domain, canceling the
5580                         effects of
5581                         any forwarders in the <span><strong class="command">options</strong></span> statement. Thus
5582                         if you want to use this type of zone to change the
5583                         behavior of the
5584                         global <span><strong class="command">forward</strong></span> option
5585                         (that is, "forward first"
5586                         to, then "forward only", or vice versa, but want to
5587                         use the same
5588                         servers as set globally) you need to re-specify the
5589                         global forwarders.
5590                       </p>
5591                     </td>
5592 </tr>
5593 <tr>
5594 <td>
5595                       <p>
5596                         <code class="varname">hint</code>
5597                       </p>
5598                     </td>
5599 <td>
5600                       <p>
5601                         The initial set of root name servers is
5602                         specified using a "hint zone". When the server starts
5603                         up, it uses
5604                         the root hints to find a root name server and get the
5605                         most recent
5606                         list of root name servers. If no hint zone is
5607                         specified for class
5608                         IN, the server uses a compiled-in default set of root
5609                         servers hints.
5610                         Classes other than IN have no built-in defaults hints.
5611                       </p>
5612                     </td>
5613 </tr>
5614 <tr>
5615 <td>
5616                       <p>
5617                         <code class="varname">delegation-only</code>
5618                       </p>
5619                     </td>
5620 <td>
5621                       <p>
5622                         This is used to enforce the delegation-only
5623                         status of infrastructure zones (e.g. COM,
5624                         NET, ORG).  Any answer that is received
5625                         without an explicit or implicit delegation
5626                         in the authority section will be treated
5627                         as NXDOMAIN.  This does not apply to the
5628                         zone apex.  This should not be applied to
5629                         leaf zones.
5630                       </p>
5631                       <p>
5632                         <code class="varname">delegation-only</code> has no
5633                         effect on answers received from forwarders.
5634                       </p>
5635                       <p>
5636                         See caveats in <a href="Bv9ARM.ch06.html#root_delegation_only"><span><strong class="command">root-delegation-only</strong></span></a>.
5637                       </p>
5638                     </td>
5639 </tr>
5640 </tbody>
5641 </table></div>
5642 </div>
5643 <div class="sect3" lang="en">
5644 <div class="titlepage"><div><div><h4 class="title">
5645 <a name="id2589094"></a>Class</h4></div></div></div>
5646 <p>
5647               The zone's name may optionally be followed by a class. If
5648               a class is not specified, class <code class="literal">IN</code> (for <code class="varname">Internet</code>),
5649               is assumed. This is correct for the vast majority of cases.
5650             </p>
5651 <p>
5652               The <code class="literal">hesiod</code> class is
5653               named for an information service from MIT's Project Athena. It
5654               is
5655               used to share information about various systems databases, such
5656               as users, groups, printers and so on. The keyword
5657               <code class="literal">HS</code> is
5658               a synonym for hesiod.
5659             </p>
5660 <p>
5661               Another MIT development is Chaosnet, a LAN protocol created
5662               in the mid-1970s. Zone data for it can be specified with the <code class="literal">CHAOS</code> class.
5663             </p>
5664 </div>
5665 <div class="sect3" lang="en">
5666 <div class="titlepage"><div><div><h4 class="title">
5667 <a name="id2589127"></a>Zone Options</h4></div></div></div>
5668 <div class="variablelist"><dl>
5669 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
5670 <dd><p>
5671                     See the description of
5672                     <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>.
5673                   </p></dd>
5674 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
5675 <dd><p>
5676                     See the description of
5677                     <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>.
5678                   </p></dd>
5679 <dt><span class="term"><span><strong class="command">allow-query-on</strong></span></span></dt>
5680 <dd><p>
5681                     See the description of
5682                     <span><strong class="command">allow-query-on</strong></span> in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
5683                   </p></dd>
5684 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
5685 <dd><p>
5686                     See the description of <span><strong class="command">allow-transfer</strong></span>
5687                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
5688                   </p></dd>
5689 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
5690 <dd><p>
5691                     See the description of <span><strong class="command">allow-update</strong></span>
5692                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
5693                   </p></dd>
5694 <dt><span class="term"><span><strong class="command">update-policy</strong></span></span></dt>
5695 <dd><p>
5696                     Specifies a "Simple Secure Update" policy. See
5697                     <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>.
5698                   </p></dd>
5699 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
5700 <dd><p>
5701                     See the description of <span><strong class="command">allow-update-forwarding</strong></span>
5702                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
5703                   </p></dd>
5704 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
5705 <dd><p>
5706                     Only meaningful if <span><strong class="command">notify</strong></span>
5707                     is
5708                     active for this zone. The set of machines that will
5709                     receive a
5710                     <code class="literal">DNS NOTIFY</code> message
5711                     for this zone is made up of all the listed name servers
5712                     (other than
5713                     the primary master) for the zone plus any IP addresses
5714                     specified
5715                     with <span><strong class="command">also-notify</strong></span>. A port
5716                     may be specified
5717                     with each <span><strong class="command">also-notify</strong></span>
5718                     address to send the notify
5719                     messages to a port other than the default of 53.
5720                     <span><strong class="command">also-notify</strong></span> is not
5721                     meaningful for stub zones.
5722                     The default is the empty list.
5723                   </p></dd>
5724 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
5725 <dd><p>
5726                     This option is used to restrict the character set and
5727                     syntax of
5728                     certain domain names in master files and/or DNS responses
5729                     received from the
5730                     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>
5731                     zones the default is <span><strong class="command">warn</strong></span>.
5732                   </p></dd>
5733 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
5734 <dd><p>
5735                     See the description of
5736                     <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>.
5737                   </p></dd>
5738 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
5739 <dd><p>
5740                     See the description of
5741                     <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>.
5742                   </p></dd>
5743 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
5744 <dd><p>
5745                     See the description of
5746                     <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>.
5747                   </p></dd>
5748 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
5749 <dd><p>
5750                     See the description of
5751                     <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>.
5752                   </p></dd>
5753 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
5754 <dd><p>
5755                     See the description of
5756                     <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>.
5757                   </p></dd>
5758 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
5759 <dd><p>
5760                     See the description of
5761                     <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>.
5762                   </p></dd>
5763 <dt><span class="term"><span><strong class="command">try-tcp-refresh</strong></span></span></dt>
5764 <dd><p>
5765                     See the description of
5766                     <span><strong class="command">try-tcp-refresh</strong></span> in <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
5767                   </p></dd>
5768 <dt><span class="term"><span><strong class="command">database</strong></span></span></dt>
5769 <dd>
5770 <p>
5771                     Specify the type of database to be used for storing the
5772                     zone data.  The string following the <span><strong class="command">database</strong></span> keyword
5773                     is interpreted as a list of whitespace-delimited words.
5774                     The first word
5775                     identifies the database type, and any subsequent words are
5776                     passed
5777                     as arguments to the database to be interpreted in a way
5778                     specific
5779                     to the database type.
5780                   </p>
5781 <p>
5782                     The default is <strong class="userinput"><code>"rbt"</code></strong>, BIND 9's
5783                     native in-memory
5784                     red-black-tree database.  This database does not take
5785                     arguments.
5786                   </p>
5787 <p>
5788                     Other values are possible if additional database drivers
5789                     have been linked into the server.  Some sample drivers are
5790                     included
5791                     with the distribution but none are linked in by default.
5792                   </p>
5793 </dd>
5794 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
5795 <dd><p>
5796                     See the description of
5797                     <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>.
5798                   </p></dd>
5799 <dt><span class="term"><span><strong class="command">delegation-only</strong></span></span></dt>
5800 <dd>
5801 <p>
5802                     The flag only applies to hint and stub zones.  If set
5803                     to <strong class="userinput"><code>yes</code></strong>, then the zone will also be
5804                     treated as if it is also a delegation-only type zone.
5805                   </p>
5806 <p>
5807                     See caveats in <a href="Bv9ARM.ch06.html#root_delegation_only"><span><strong class="command">root-delegation-only</strong></span></a>.
5808                   </p>
5809 </dd>
5810 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
5811 <dd><p>
5812                     Only meaningful if the zone has a forwarders
5813                     list. The <span><strong class="command">only</strong></span> value causes
5814                     the lookup to fail
5815                     after trying the forwarders and getting no answer, while <span><strong class="command">first</strong></span> would
5816                     allow a normal lookup to be tried.
5817                   </p></dd>
5818 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
5819 <dd><p>
5820                     Used to override the list of global forwarders.
5821                     If it is not specified in a zone of type <span><strong class="command">forward</strong></span>,
5822                     no forwarding is done for the zone and the global options are
5823                     not used.
5824                   </p></dd>
5825 <dt><span class="term"><span><strong class="command">ixfr-base</strong></span></span></dt>
5826 <dd><p>
5827                     Was used in <acronym class="acronym">BIND</acronym> 8 to
5828                     specify the name
5829                     of the transaction log (journal) file for dynamic update
5830                     and IXFR.
5831                     <acronym class="acronym">BIND</acronym> 9 ignores the option
5832                     and constructs the name of the journal
5833                     file by appending "<code class="filename">.jnl</code>"
5834                     to the name of the
5835                     zone file.
5836                   </p></dd>
5837 <dt><span class="term"><span><strong class="command">ixfr-tmp-file</strong></span></span></dt>
5838 <dd><p>
5839                     Was an undocumented option in <acronym class="acronym">BIND</acronym> 8.
5840                     Ignored in <acronym class="acronym">BIND</acronym> 9.
5841                   </p></dd>
5842 <dt><span class="term"><span><strong class="command">journal</strong></span></span></dt>
5843 <dd><p>
5844                     Allow the default journal's filename to be overridden.
5845                     The default is the zone's filename with "<code class="filename">.jnl</code>" appended.
5846                     This is applicable to <span><strong class="command">master</strong></span> and <span><strong class="command">slave</strong></span> zones.
5847                   </p></dd>
5848 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
5849 <dd><p>
5850                     See the description of
5851                     <span><strong class="command">max-journal-size</strong></span> in <a href="Bv9ARM.ch06.html#server_resource_limits" title="Server  Resource Limits">the section called &#8220;Server  Resource Limits&#8221;</a>.
5852                   </p></dd>
5853 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
5854 <dd><p>
5855                     See the description of
5856                     <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>.
5857                   </p></dd>
5858 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
5859 <dd><p>
5860                     See the description of
5861                     <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>.
5862                   </p></dd>
5863 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
5864 <dd><p>
5865                     See the description of
5866                     <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>.
5867                   </p></dd>
5868 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
5869 <dd><p>
5870                     See the description of
5871                     <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>.
5872                   </p></dd>
5873 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
5874 <dd><p>
5875                     See the description of
5876                     <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>.
5877                   </p></dd>
5878 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
5879 <dd><p>
5880                     See the description of
5881                     <span><strong class="command">notify-delay</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
5882                   </p></dd>
5883 <dt><span class="term"><span><strong class="command">notify-to-soa</strong></span></span></dt>
5884 <dd><p>
5885                     See the description of
5886                     <span><strong class="command">notify-to-soa</strong></span> in
5887                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
5888                   </p></dd>
5889 <dt><span class="term"><span><strong class="command">pubkey</strong></span></span></dt>
5890 <dd><p>
5891                     In <acronym class="acronym">BIND</acronym> 8, this option was
5892                     intended for specifying
5893                     a public zone key for verification of signatures in DNSSEC
5894                     signed
5895                     zones when they are loaded from disk. <acronym class="acronym">BIND</acronym> 9 does not verify signatures
5896                     on load and ignores the option.
5897                   </p></dd>
5898 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
5899 <dd><p>
5900                     If <strong class="userinput"><code>yes</code></strong>, the server will keep
5901                     statistical
5902                     information for this zone, which can be dumped to the
5903                     <span><strong class="command">statistics-file</strong></span> defined in
5904                     the server options.
5905                   </p></dd>
5906 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
5907 <dd><p>
5908                     See the description of
5909                     <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>.
5910                   </p></dd>
5911 <dt><span class="term"><span><strong class="command">sig-signing-nodes</strong></span></span></dt>
5912 <dd><p>
5913                     See the description of
5914                     <span><strong class="command">sig-signing-nodes</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
5915                   </p></dd>
5916 <dt><span class="term"><span><strong class="command">sig-signing-signatures</strong></span></span></dt>
5917 <dd><p>
5918                     See the description of
5919                     <span><strong class="command">sig-signing-signatures</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
5920                   </p></dd>
5921 <dt><span class="term"><span><strong class="command">sig-signing-type</strong></span></span></dt>
5922 <dd><p>
5923                     See the description of
5924                     <span><strong class="command">sig-signing-type</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
5925                   </p></dd>
5926 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
5927 <dd><p>
5928                     See the description of
5929                     <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>.
5930                   </p></dd>
5931 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
5932 <dd><p>
5933                     See the description of
5934                     <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>.
5935                   </p></dd>
5936 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
5937 <dd><p>
5938                     See the description of
5939                     <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>.
5940                   </p></dd>
5941 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
5942 <dd><p>
5943                     See the description of
5944                     <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>.
5945                   </p></dd>
5946 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
5947 <dd><p>
5948                     See the description of
5949                     <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>.
5950                   </p></dd>
5951 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
5952 <dd><p>
5953                     See the description of
5954                     <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>.
5955                   </p></dd>
5956 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
5957 <dd><p>
5958                     See the description of
5959                     <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>.
5960                   </p></dd>
5961 <dt>
5962 <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>
5963 </dt>
5964 <dd><p>
5965                     See the description in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
5966                   </p></dd>
5967 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
5968 <dd><p>
5969                     See the description of
5970                     <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>.
5971                     (Note that the <span><strong class="command">ixfr-from-differences</strong></span>
5972                     <strong class="userinput"><code>master</code></strong> and
5973                     <strong class="userinput"><code>slave</code></strong> choices are not
5974                     available at the zone level.)
5975                   </p></dd>
5976 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
5977 <dd><p>
5978                     See the description of
5979                     <span><strong class="command">key-directory</strong></span> in <a href="Bv9ARM.ch06.html#options" title="options Statement Definition and
5980           Usage">the section called &#8220;<span><strong class="command">options</strong></span> Statement Definition and
5981           Usage&#8221;</a>.
5982                   </p></dd>
5983 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
5984 <dd><p>
5985                     See the description of <span><strong class="command">multi-master</strong></span> in
5986                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
5987                   </p></dd>
5988 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
5989 <dd><p>
5990                     See the description of <span><strong class="command">masterfile-format</strong></span>
5991                     in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
5992                   </p></dd>
5993 </dl></div>
5994 </div>
5995 <div class="sect3" lang="en">
5996 <div class="titlepage"><div><div><h4 class="title">
5997 <a name="dynamic_update_policies"></a>Dynamic Update Policies</h4></div></div></div>
5998 <p><acronym class="acronym">BIND</acronym> 9 supports two alternative
5999               methods of granting clients the right to perform
6000               dynamic updates to a zone, configured by the
6001               <span><strong class="command">allow-update</strong></span> and
6002               <span><strong class="command">update-policy</strong></span> option, respectively.
6003             </p>
6004 <p>
6005               The <span><strong class="command">allow-update</strong></span> clause works the
6006               same way as in previous versions of <acronym class="acronym">BIND</acronym>.
6007               It grants given clients the permission to update any
6008               record of any name in the zone.
6009             </p>
6010 <p>
6011               The <span><strong class="command">update-policy</strong></span> clause is new
6012               in <acronym class="acronym">BIND</acronym> 9 and allows more fine-grained
6013               control over what updates are allowed.  A set of rules
6014               is specified, where each rule either grants or denies
6015               permissions for one or more names to be updated by
6016               one or more identities.  If the dynamic update request
6017               message is signed (that is, it includes either a TSIG
6018               or SIG(0) record), the identity of the signer can be
6019               determined.
6020             </p>
6021 <p>
6022               Rules are specified in the <span><strong class="command">update-policy</strong></span>
6023               zone option, and are only meaningful for master zones.
6024               When the <span><strong class="command">update-policy</strong></span> statement
6025               is present, it is a configuration error for the
6026               <span><strong class="command">allow-update</strong></span> statement to be
6027               present.  The <span><strong class="command">update-policy</strong></span> statement
6028               only examines the signer of a message; the source
6029               address is not relevant.
6030             </p>
6031 <p>
6032               This is how a rule definition looks:
6033             </p>
6034 <pre class="programlisting">
6035 ( <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>]
6036 </pre>
6037 <p>
6038               Each rule grants or denies privileges.  Once a message has
6039               successfully matched a rule, the operation is immediately
6040               granted
6041               or denied and no further rules are examined.  A rule is matched
6042               when the signer matches the identity field, the name matches the
6043               name field in accordance with the nametype field, and the type
6044               matches
6045               the types specified in the type field.
6046             </p>
6047 <p>
6048               No signer is required for <em class="replaceable"><code>tcp-self</code></em>
6049               or <em class="replaceable"><code>6to4-self</code></em> however the standard
6050               reverse mapping / prefix conversion must match the identity
6051               field.
6052             </p>
6053 <p>
6054               The identity field specifies a name or a wildcard
6055               name.  Normally, this is the name of the TSIG or
6056               SIG(0) key used to sign the update request.  When a
6057               TKEY exchange has been used to create a shared secret,
6058               the identity of the shared secret is the same as the
6059               identity of the key used to authenticate the TKEY
6060               exchange.  TKEY is also the negotiation method used
6061               by GSS-TSIG, which establishes an identity that is
6062               the Kerberos principal of the client, such as
6063               <strong class="userinput"><code>"user@host.domain"</code></strong>.  When the
6064               <em class="replaceable"><code>identity</code></em> field specifies
6065               a wildcard name, it is subject to DNS wildcard
6066               expansion, so the rule will apply to multiple identities.
6067               The <em class="replaceable"><code>identity</code></em> field must
6068               contain a fully-qualified domain name.
6069             </p>
6070 <p>
6071               The <em class="replaceable"><code>nametype</code></em> field has 12
6072               values:
6073               <code class="varname">name</code>, <code class="varname">subdomain</code>,
6074               <code class="varname">wildcard</code>, <code class="varname">self</code>,
6075               <code class="varname">selfsub</code>, <code class="varname">selfwild</code>,
6076               <code class="varname">krb5-self</code>, <code class="varname">ms-self</code>,
6077               <code class="varname">krb5-subdomain</code>,
6078               <code class="varname">ms-subdomain</code>,
6079               <code class="varname">tcp-self</code> and <code class="varname">6to4-self</code>.
6080             </p>
6081 <div class="informaltable"><table border="1">
6082 <colgroup>
6083 <col>
6084 <col>
6085 </colgroup>
6086 <tbody>
6087 <tr>
6088 <td>
6089                       <p>
6090                         <code class="varname">name</code>
6091                       </p>
6092                     </td>
6093 <td>
6094                       <p>
6095                         Exact-match semantics.  This rule matches
6096                         when the name being updated is identical
6097                         to the contents of the
6098                         <em class="replaceable"><code>name</code></em> field.
6099                       </p>
6100                     </td>
6101 </tr>
6102 <tr>
6103 <td>
6104                       <p>
6105                         <code class="varname">subdomain</code>
6106                       </p>
6107                     </td>
6108 <td>
6109                       <p>
6110                         This rule matches when the name being updated
6111                         is a subdomain of, or identical to, the
6112                         contents of the <em class="replaceable"><code>name</code></em>
6113                         field.
6114                       </p>
6115                     </td>
6116 </tr>
6117 <tr>
6118 <td>
6119                       <p>
6120                         <code class="varname">wildcard</code>
6121                       </p>
6122                     </td>
6123 <td>
6124                       <p>
6125                         The <em class="replaceable"><code>name</code></em> field
6126                         is subject to DNS wildcard expansion, and
6127                         this rule matches when the name being updated
6128                         name is a valid expansion of the wildcard.
6129                       </p>
6130                     </td>
6131 </tr>
6132 <tr>
6133 <td>
6134                       <p>
6135                         <code class="varname">self</code>
6136                       </p>
6137                     </td>
6138 <td>
6139                       <p>
6140                         This rule matches when the name being updated
6141                         matches the contents of the
6142                         <em class="replaceable"><code>identity</code></em> field.
6143                         The <em class="replaceable"><code>name</code></em> field
6144                         is ignored, but should be the same as the
6145                         <em class="replaceable"><code>identity</code></em> field.
6146                         The <code class="varname">self</code> nametype is
6147                         most useful when allowing using one key per
6148                         name to update, where the key has the same
6149                         name as the name to be updated.  The
6150                         <em class="replaceable"><code>identity</code></em> would
6151                         be specified as <code class="constant">*</code> (an asterisk) in
6152                         this case.
6153                       </p>
6154                     </td>
6155 </tr>
6156 <tr>
6157 <td>
6158                       <p>
6159                         <code class="varname">selfsub</code>
6160                       </p>
6161                     </td>
6162 <td>
6163                       <p>
6164                         This rule is similar to <code class="varname">self</code>
6165                         except that subdomains of <code class="varname">self</code>
6166                         can also be updated.
6167                       </p>
6168                     </td>
6169 </tr>
6170 <tr>
6171 <td>
6172                       <p>
6173                         <code class="varname">selfwild</code>
6174                       </p>
6175                     </td>
6176 <td>
6177                       <p>
6178                         This rule is similar to <code class="varname">self</code>
6179                         except that only subdomains of
6180                         <code class="varname">self</code> can be updated.
6181                       </p>
6182                     </td>
6183 </tr>
6184 <tr>
6185 <td>
6186                       <p>
6187                         <code class="varname">tcp-self</code>
6188                       </p>
6189                     </td>
6190 <td>
6191                       <p>
6192                         Allow updates that have been sent via TCP and
6193                         for which the standard mapping from the initiating
6194                         IP address into the IN-ADDR.ARPA and IP6.ARPA
6195                         namespaces match the name to be updated.
6196                       </p>
6197                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
6198 <h3 class="title">Note</h3>
6199                         It is theoretically possible to spoof these TCP
6200                         sessions.
6201                       </div>
6202                     </td>
6203 </tr>
6204 <tr>
6205 <td>
6206                       <p>
6207                         <code class="varname">6to4-self</code>
6208                       </p>
6209                     </td>
6210 <td>
6211                       <p>
6212                         Allow the 6to4 prefix to be update by any TCP
6213                         conection from the 6to4 network or from the
6214                         corresponding IPv4 address.  This is intended
6215                         to allow NS or DNAME RRsets to be added to the
6216                         reverse tree.
6217                       </p>
6218                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
6219 <h3 class="title">Note</h3>
6220                         It is theoretically possible to spoof these TCP
6221                         sessions.
6222                       </div>
6223                     </td>
6224 </tr>
6225 </tbody>
6226 </table></div>
6227 <p>
6228               In all cases, the <em class="replaceable"><code>name</code></em>
6229               field must
6230               specify a fully-qualified domain name.
6231             </p>
6232 <p>
6233               If no types are explicitly specified, this rule matches
6234               all types except RRSIG, NS, SOA, NSEC and NSEC3. Types
6235               may be specified by name, including "ANY" (ANY matches
6236               all types except NSEC and NSEC3, which can never be
6237               updated).  Note that when an attempt is made to delete
6238               all records associated with a name, the rules are
6239               checked for each existing record type.
6240             </p>
6241 </div>
6242 </div>
6243 </div>
6244 <div class="sect1" lang="en">
6245 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
6246 <a name="id2591138"></a>Zone File</h2></div></div></div>
6247 <div class="sect2" lang="en">
6248 <div class="titlepage"><div><div><h3 class="title">
6249 <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>
6250 <p>
6251             This section, largely borrowed from RFC 1034, describes the
6252             concept of a Resource Record (RR) and explains when each is used.
6253             Since the publication of RFC 1034, several new RRs have been
6254             identified
6255             and implemented in the DNS. These are also included.
6256           </p>
6257 <div class="sect3" lang="en">
6258 <div class="titlepage"><div><div><h4 class="title">
6259 <a name="id2591156"></a>Resource Records</h4></div></div></div>
6260 <p>
6261               A domain name identifies a node.  Each node has a set of
6262               resource information, which may be empty.  The set of resource
6263               information associated with a particular name is composed of
6264               separate RRs. The order of RRs in a set is not significant and
6265               need not be preserved by name servers, resolvers, or other
6266               parts of the DNS. However, sorting of multiple RRs is
6267               permitted for optimization purposes, for example, to specify
6268               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>.
6269             </p>
6270 <p>
6271               The components of a Resource Record are:
6272             </p>
6273 <div class="informaltable"><table border="1">
6274 <colgroup>
6275 <col>
6276 <col>
6277 </colgroup>
6278 <tbody>
6279 <tr>
6280 <td>
6281                       <p>
6282                         owner name
6283                       </p>
6284                     </td>
6285 <td>
6286                       <p>
6287                         The domain name where the RR is found.
6288                       </p>
6289                     </td>
6290 </tr>
6291 <tr>
6292 <td>
6293                       <p>
6294                         type
6295                       </p>
6296                     </td>
6297 <td>
6298                       <p>
6299                         An encoded 16-bit value that specifies
6300                         the type of the resource record.
6301                       </p>
6302                     </td>
6303 </tr>
6304 <tr>
6305 <td>
6306                       <p>
6307                         TTL
6308                       </p>
6309                     </td>
6310 <td>
6311                       <p>
6312                         The time-to-live of the RR. This field
6313                         is a 32-bit integer in units of seconds, and is
6314                         primarily used by
6315                         resolvers when they cache RRs. The TTL describes how
6316                         long a RR can
6317                         be cached before it should be discarded.
6318                       </p>
6319                     </td>
6320 </tr>
6321 <tr>
6322 <td>
6323                       <p>
6324                         class
6325                       </p>
6326                     </td>
6327 <td>
6328                       <p>
6329                         An encoded 16-bit value that identifies
6330                         a protocol family or instance of a protocol.
6331                       </p>
6332                     </td>
6333 </tr>
6334 <tr>
6335 <td>
6336                       <p>
6337                         RDATA
6338                       </p>
6339                     </td>
6340 <td>
6341                       <p>
6342                         The resource data.  The format of the
6343                         data is type (and sometimes class) specific.
6344                       </p>
6345                     </td>
6346 </tr>
6347 </tbody>
6348 </table></div>
6349 <p>
6350               The following are <span class="emphasis"><em>types</em></span> of valid RRs:
6351             </p>
6352 <div class="informaltable"><table border="1">
6353 <colgroup>
6354 <col>
6355 <col>
6356 </colgroup>
6357 <tbody>
6358 <tr>
6359 <td>
6360                       <p>
6361                         A
6362                       </p>
6363                     </td>
6364 <td>
6365                       <p>
6366                         A host address.  In the IN class, this is a
6367                         32-bit IP address.  Described in RFC 1035.
6368                       </p>
6369                     </td>
6370 </tr>
6371 <tr>
6372 <td>
6373                       <p>
6374                         AAAA
6375                       </p>
6376                     </td>
6377 <td>
6378                       <p>
6379                         IPv6 address.  Described in RFC 1886.
6380                       </p>
6381                     </td>
6382 </tr>
6383 <tr>
6384 <td>
6385                       <p>
6386                         A6
6387                       </p>
6388                     </td>
6389 <td>
6390                       <p>
6391                         IPv6 address.  This can be a partial
6392                         address (a suffix) and an indirection to the name
6393                         where the rest of the
6394                         address (the prefix) can be found.  Experimental.
6395                         Described in RFC 2874.
6396                       </p>
6397                     </td>
6398 </tr>
6399 <tr>
6400 <td>
6401                       <p>
6402                         AFSDB
6403                       </p>
6404                     </td>
6405 <td>
6406                       <p>
6407                         Location of AFS database servers.
6408                         Experimental.  Described in RFC 1183.
6409                       </p>
6410                     </td>
6411 </tr>
6412 <tr>
6413 <td>
6414                       <p>
6415                         APL
6416                       </p>
6417                     </td>
6418 <td>
6419                       <p>
6420                         Address prefix list.  Experimental.
6421                         Described in RFC 3123.
6422                       </p>
6423                     </td>
6424 </tr>
6425 <tr>
6426 <td>
6427                       <p>
6428                         CERT
6429                       </p>
6430                     </td>
6431 <td>
6432                       <p>
6433                         Holds a digital certificate.
6434                         Described in RFC 2538.
6435                       </p>
6436                     </td>
6437 </tr>
6438 <tr>
6439 <td>
6440                       <p>
6441                         CNAME
6442                       </p>
6443                     </td>
6444 <td>
6445                       <p>
6446                         Identifies the canonical name of an alias.
6447                         Described in RFC 1035.
6448                       </p>
6449                     </td>
6450 </tr>
6451 <tr>
6452 <td>
6453                       <p>
6454                         DHCID
6455                       </p>
6456                     </td>
6457 <td>
6458                       <p>
6459                         Is used for identifying which DHCP client is
6460                         associated with this name.  Described in RFC 4701.
6461                       </p>
6462                     </td>
6463 </tr>
6464 <tr>
6465 <td>
6466                       <p>
6467                         DNAME
6468                       </p>
6469                     </td>
6470 <td>
6471                       <p>
6472                         Replaces the domain name specified with
6473                         another name to be looked up, effectively aliasing an
6474                         entire
6475                         subtree of the domain name space rather than a single
6476                         record
6477                         as in the case of the CNAME RR.
6478                         Described in RFC 2672.
6479                       </p>
6480                     </td>
6481 </tr>
6482 <tr>
6483 <td>
6484                       <p>
6485                         DNSKEY
6486                       </p>
6487                     </td>
6488 <td>
6489                       <p>
6490                         Stores a public key associated with a signed
6491                         DNS zone.  Described in RFC 4034.
6492                       </p>
6493                     </td>
6494 </tr>
6495 <tr>
6496 <td>
6497                       <p>
6498                         DS
6499                       </p>
6500                     </td>
6501 <td>
6502                       <p>
6503                         Stores the hash of a public key associated with a
6504                         signed DNS zone.  Described in RFC 4034.
6505                       </p>
6506                     </td>
6507 </tr>
6508 <tr>
6509 <td>
6510                       <p>
6511                         GPOS
6512                       </p>
6513                     </td>
6514 <td>
6515                       <p>
6516                         Specifies the global position.  Superseded by LOC.
6517                       </p>
6518                     </td>
6519 </tr>
6520 <tr>
6521 <td>
6522                       <p>
6523                         HINFO
6524                       </p>
6525                     </td>
6526 <td>
6527                       <p>
6528                         Identifies the CPU and OS used by a host.
6529                         Described in RFC 1035.
6530                       </p>
6531                     </td>
6532 </tr>
6533 <tr>
6534 <td>
6535                       <p>
6536                         IPSECKEY
6537                       </p>
6538                     </td>
6539 <td>
6540                       <p>
6541                         Provides a method for storing IPsec keying material in
6542                         DNS.  Described in RFC 4025.
6543                       </p>
6544                     </td>
6545 </tr>
6546 <tr>
6547 <td>
6548                       <p>
6549                         ISDN
6550                       </p>
6551                     </td>
6552 <td>
6553                       <p>
6554                         Representation of ISDN addresses.
6555                         Experimental.  Described in RFC 1183.
6556                       </p>
6557                     </td>
6558 </tr>
6559 <tr>
6560 <td>
6561                       <p>
6562                         KEY
6563                       </p>
6564                     </td>
6565 <td>
6566                       <p>
6567                         Stores a public key associated with a
6568                         DNS name.  Used in original DNSSEC; replaced
6569                         by DNSKEY in DNSSECbis, but still used with
6570                         SIG(0).  Described in RFCs 2535 and 2931.
6571                       </p>
6572                     </td>
6573 </tr>
6574 <tr>
6575 <td>
6576                       <p>
6577                         KX
6578                       </p>
6579                     </td>
6580 <td>
6581                       <p>
6582                         Identifies a key exchanger for this
6583                         DNS name.  Described in RFC 2230.
6584                       </p>
6585                     </td>
6586 </tr>
6587 <tr>
6588 <td>
6589                       <p>
6590                         LOC
6591                       </p>
6592                     </td>
6593 <td>
6594                       <p>
6595                         For storing GPS info.  Described in RFC 1876.
6596                         Experimental.
6597                       </p>
6598                     </td>
6599 </tr>
6600 <tr>
6601 <td>
6602                       <p>
6603                         MX
6604                       </p>
6605                     </td>
6606 <td>
6607                       <p>
6608                         Identifies a mail exchange for the domain with
6609                         a 16-bit preference value (lower is better)
6610                         followed by the host name of the mail exchange.
6611                         Described in RFC 974, RFC 1035.
6612                       </p>
6613                     </td>
6614 </tr>
6615 <tr>
6616 <td>
6617                       <p>
6618                         NAPTR
6619                       </p>
6620                     </td>
6621 <td>
6622                       <p>
6623                         Name authority pointer.  Described in RFC 2915.
6624                       </p>
6625                     </td>
6626 </tr>
6627 <tr>
6628 <td>
6629                       <p>
6630                         NSAP
6631                       </p>
6632                     </td>
6633 <td>
6634                       <p>
6635                         A network service access point.
6636                         Described in RFC 1706.
6637                       </p>
6638                     </td>
6639 </tr>
6640 <tr>
6641 <td>
6642                       <p>
6643                         NS
6644                       </p>
6645                     </td>
6646 <td>
6647                       <p>
6648                         The authoritative name server for the
6649                         domain.  Described in RFC 1035.
6650                       </p>
6651                     </td>
6652 </tr>
6653 <tr>
6654 <td>
6655                       <p>
6656                         NSEC
6657                       </p>
6658                     </td>
6659 <td>
6660                       <p>
6661                         Used in DNSSECbis to securely indicate that
6662                         RRs with an owner name in a certain name interval do
6663                         not exist in
6664                         a zone and indicate what RR types are present for an
6665                         existing name.
6666                         Described in RFC 4034.
6667                       </p>
6668                     </td>
6669 </tr>
6670 <tr>
6671 <td>
6672                       <p>
6673                         NSEC3
6674                       </p>
6675                     </td>
6676 <td>
6677                       <p>
6678                         Used in DNSSECbis to securely indicate that
6679                         RRs with an owner name in a certain name
6680                         interval do not exist in a zone and indicate
6681                         what RR types are present for an existing
6682                         name.  NSEC3 differs from NSEC in that it
6683                         prevents zone enumeration but is more
6684                         computationally expensive on both the server
6685                         and the client than NSEC.  Described in RFC
6686                         5155.
6687                       </p>
6688                     </td>
6689 </tr>
6690 <tr>
6691 <td>
6692                       <p>
6693                         NSEC3PARAM
6694                       </p>
6695                     </td>
6696 <td>
6697                       <p>
6698                         Used in DNSSECbis to tell the authoritative
6699                         server which NSEC3 chains are available to use.
6700                         Described in RFC 5155.
6701                       </p>
6702                     </td>
6703 </tr>
6704 <tr>
6705 <td>
6706                       <p>
6707                         NXT
6708                       </p>
6709                     </td>
6710 <td>
6711                       <p>
6712                         Used in DNSSEC to securely indicate that
6713                         RRs with an owner name in a certain name interval do
6714                         not exist in
6715                         a zone and indicate what RR types are present for an
6716                         existing name.
6717                         Used in original DNSSEC; replaced by NSEC in
6718                         DNSSECbis.
6719                         Described in RFC 2535.
6720                       </p>
6721                     </td>
6722 </tr>
6723 <tr>
6724 <td>
6725                       <p>
6726                         PTR
6727                       </p>
6728                     </td>
6729 <td>
6730                       <p>
6731                         A pointer to another part of the domain
6732                         name space.  Described in RFC 1035.
6733                       </p>
6734                     </td>
6735 </tr>
6736 <tr>
6737 <td>
6738                       <p>
6739                         PX
6740                       </p>
6741                     </td>
6742 <td>
6743                       <p>
6744                         Provides mappings between RFC 822 and X.400
6745                         addresses.  Described in RFC 2163.
6746                       </p>
6747                     </td>
6748 </tr>
6749 <tr>
6750 <td>
6751                       <p>
6752                         RP
6753                       </p>
6754                     </td>
6755 <td>
6756                       <p>
6757                         Information on persons responsible
6758                         for the domain.  Experimental.  Described in RFC 1183.
6759                       </p>
6760                     </td>
6761 </tr>
6762 <tr>
6763 <td>
6764                       <p>
6765                         RRSIG
6766                       </p>
6767                     </td>
6768 <td>
6769                       <p>
6770                         Contains DNSSECbis signature data.  Described
6771                         in RFC 4034.
6772                       </p>
6773                     </td>
6774 </tr>
6775 <tr>
6776 <td>
6777                       <p>
6778                         RT
6779                       </p>
6780                     </td>
6781 <td>
6782                       <p>
6783                         Route-through binding for hosts that
6784                         do not have their own direct wide area network
6785                         addresses.
6786                         Experimental.  Described in RFC 1183.
6787                       </p>
6788                     </td>
6789 </tr>
6790 <tr>
6791 <td>
6792                       <p>
6793                         SIG
6794                       </p>
6795                     </td>
6796 <td>
6797                       <p>
6798                         Contains DNSSEC signature data.  Used in
6799                         original DNSSEC; replaced by RRSIG in
6800                         DNSSECbis, but still used for SIG(0).
6801                         Described in RFCs 2535 and 2931.
6802                       </p>
6803                     </td>
6804 </tr>
6805 <tr>
6806 <td>
6807                       <p>
6808                         SOA
6809                       </p>
6810                     </td>
6811 <td>
6812                       <p>
6813                         Identifies the start of a zone of authority.
6814                         Described in RFC 1035.
6815                       </p>
6816                     </td>
6817 </tr>
6818 <tr>
6819 <td>
6820                       <p>
6821                         SPF
6822                       </p>
6823                     </td>
6824 <td>
6825                       <p>
6826                         Contains the Sender Policy Framework information
6827                         for a given email domain.  Described in RFC 4408.
6828                       </p>
6829                     </td>
6830 </tr>
6831 <tr>
6832 <td>
6833                       <p>
6834                         SRV
6835                       </p>
6836                     </td>
6837 <td>
6838                       <p>
6839                         Information about well known network
6840                         services (replaces WKS).  Described in RFC 2782.
6841                       </p>
6842                     </td>
6843 </tr>
6844 <tr>
6845 <td>
6846                       <p>
6847                         SSHFP
6848                       </p>
6849                     </td>
6850 <td>
6851                       <p>
6852                         Provides a way to securely publish a secure shell key's
6853                         fingerprint.  Described in RFC 4255.
6854                       </p>
6855                     </td>
6856 </tr>
6857 <tr>
6858 <td>
6859                       <p>
6860                         TXT
6861                       </p>
6862                     </td>
6863 <td>
6864                       <p>
6865                         Text records.  Described in RFC 1035.
6866                       </p>
6867                     </td>
6868 </tr>
6869 <tr>
6870 <td>
6871                       <p>
6872                         WKS
6873                       </p>
6874                     </td>
6875 <td>
6876                       <p>
6877                         Information about which well known
6878                         network services, such as SMTP, that a domain
6879                         supports. Historical.
6880                       </p>
6881                     </td>
6882 </tr>
6883 <tr>
6884 <td>
6885                       <p>
6886                         X25
6887                       </p>
6888                     </td>
6889 <td>
6890                       <p>
6891                         Representation of X.25 network addresses.
6892                         Experimental.  Described in RFC 1183.
6893                       </p>
6894                     </td>
6895 </tr>
6896 </tbody>
6897 </table></div>
6898 <p>
6899               The following <span class="emphasis"><em>classes</em></span> of resource records
6900               are currently valid in the DNS:
6901             </p>
6902 <div class="informaltable"><table border="1">
6903 <colgroup>
6904 <col>
6905 <col>
6906 </colgroup>
6907 <tbody>
6908 <tr>
6909 <td>
6910                       <p>
6911                         IN
6912                       </p>
6913                     </td>
6914 <td>
6915                       <p>
6916                         The Internet.
6917                       </p>
6918                     </td>
6919 </tr>
6920 <tr>
6921 <td>
6922                       <p>
6923                         CH
6924                       </p>
6925                     </td>
6926 <td>
6927                       <p>
6928                         Chaosnet, a LAN protocol created at MIT in the
6929                         mid-1970s.
6930                         Rarely used for its historical purpose, but reused for
6931                         BIND's
6932                         built-in server information zones, e.g.,
6933                         <code class="literal">version.bind</code>.
6934                       </p>
6935                     </td>
6936 </tr>
6937 <tr>
6938 <td>
6939                       <p>
6940                         HS
6941                       </p>
6942                     </td>
6943 <td>
6944                       <p>
6945                         Hesiod, an information service
6946                         developed by MIT's Project Athena. It is used to share
6947                         information
6948                         about various systems databases, such as users,
6949                         groups, printers
6950                         and so on.
6951                       </p>
6952                     </td>
6953 </tr>
6954 </tbody>
6955 </table></div>
6956 <p>
6957               The owner name is often implicit, rather than forming an
6958               integral
6959               part of the RR.  For example, many name servers internally form
6960               tree
6961               or hash structures for the name space, and chain RRs off nodes.
6962               The remaining RR parts are the fixed header (type, class, TTL)
6963               which is consistent for all RRs, and a variable part (RDATA)
6964               that
6965               fits the needs of the resource being described.
6966             </p>
6967 <p>
6968               The meaning of the TTL field is a time limit on how long an
6969               RR can be kept in a cache.  This limit does not apply to
6970               authoritative
6971               data in zones; it is also timed out, but by the refreshing
6972               policies
6973               for the zone.  The TTL is assigned by the administrator for the
6974               zone where the data originates.  While short TTLs can be used to
6975               minimize caching, and a zero TTL prohibits caching, the
6976               realities
6977               of Internet performance suggest that these times should be on
6978               the
6979               order of days for the typical host.  If a change can be
6980               anticipated,
6981               the TTL can be reduced prior to the change to minimize
6982               inconsistency
6983               during the change, and then increased back to its former value
6984               following
6985               the change.
6986             </p>
6987 <p>
6988               The data in the RDATA section of RRs is carried as a combination
6989               of binary strings and domain names.  The domain names are
6990               frequently
6991               used as "pointers" to other data in the DNS.
6992             </p>
6993 </div>
6994 <div class="sect3" lang="en">
6995 <div class="titlepage"><div><div><h4 class="title">
6996 <a name="id2592779"></a>Textual expression of RRs</h4></div></div></div>
6997 <p>
6998               RRs are represented in binary form in the packets of the DNS
6999               protocol, and are usually represented in highly encoded form
7000               when
7001               stored in a name server or resolver.  In the examples provided
7002               in
7003               RFC 1034, a style similar to that used in master files was
7004               employed
7005               in order to show the contents of RRs.  In this format, most RRs
7006               are shown on a single line, although continuation lines are
7007               possible
7008               using parentheses.
7009             </p>
7010 <p>
7011               The start of the line gives the owner of the RR.  If a line
7012               begins with a blank, then the owner is assumed to be the same as
7013               that of the previous RR.  Blank lines are often included for
7014               readability.
7015             </p>
7016 <p>
7017               Following the owner, we list the TTL, type, and class of the
7018               RR.  Class and type use the mnemonics defined above, and TTL is
7019               an integer before the type field.  In order to avoid ambiguity
7020               in
7021               parsing, type and class mnemonics are disjoint, TTLs are
7022               integers,
7023               and the type mnemonic is always last. The IN class and TTL
7024               values
7025               are often omitted from examples in the interests of clarity.
7026             </p>
7027 <p>
7028               The resource data or RDATA section of the RR are given using
7029               knowledge of the typical representation for the data.
7030             </p>
7031 <p>
7032               For example, we might show the RRs carried in a message as:
7033             </p>
7034 <div class="informaltable"><table border="1">
7035 <colgroup>
7036 <col>
7037 <col>
7038 <col>
7039 </colgroup>
7040 <tbody>
7041 <tr>
7042 <td>
7043                       <p>
7044                         <code class="literal">ISI.EDU.</code>
7045                       </p>
7046                     </td>
7047 <td>
7048                       <p>
7049                         <code class="literal">MX</code>
7050                       </p>
7051                     </td>
7052 <td>
7053                       <p>
7054                         <code class="literal">10 VENERA.ISI.EDU.</code>
7055                       </p>
7056                     </td>
7057 </tr>
7058 <tr>
7059 <td>
7060                       <p></p>
7061                     </td>
7062 <td>
7063                       <p>
7064                         <code class="literal">MX</code>
7065                       </p>
7066                     </td>
7067 <td>
7068                       <p>
7069                         <code class="literal">10 VAXA.ISI.EDU</code>
7070                       </p>
7071                     </td>
7072 </tr>
7073 <tr>
7074 <td>
7075                       <p>
7076                         <code class="literal">VENERA.ISI.EDU</code>
7077                       </p>
7078                     </td>
7079 <td>
7080                       <p>
7081                         <code class="literal">A</code>
7082                       </p>
7083                     </td>
7084 <td>
7085                       <p>
7086                         <code class="literal">128.9.0.32</code>
7087                       </p>
7088                     </td>
7089 </tr>
7090 <tr>
7091 <td>
7092                       <p></p>
7093                     </td>
7094 <td>
7095                       <p>
7096                         <code class="literal">A</code>
7097                       </p>
7098                     </td>
7099 <td>
7100                       <p>
7101                         <code class="literal">10.1.0.52</code>
7102                       </p>
7103                     </td>
7104 </tr>
7105 <tr>
7106 <td>
7107                       <p>
7108                         <code class="literal">VAXA.ISI.EDU</code>
7109                       </p>
7110                     </td>
7111 <td>
7112                       <p>
7113                         <code class="literal">A</code>
7114                       </p>
7115                     </td>
7116 <td>
7117                       <p>
7118                         <code class="literal">10.2.0.27</code>
7119                       </p>
7120                     </td>
7121 </tr>
7122 <tr>
7123 <td>
7124                       <p></p>
7125                     </td>
7126 <td>
7127                       <p>
7128                         <code class="literal">A</code>
7129                       </p>
7130                     </td>
7131 <td>
7132                       <p>
7133                         <code class="literal">128.9.0.33</code>
7134                       </p>
7135                     </td>
7136 </tr>
7137 </tbody>
7138 </table></div>
7139 <p>
7140               The MX RRs have an RDATA section which consists of a 16-bit
7141               number followed by a domain name.  The address RRs use a
7142               standard
7143               IP address format to contain a 32-bit internet address.
7144             </p>
7145 <p>
7146               The above example shows six RRs, with two RRs at each of three
7147               domain names.
7148             </p>
7149 <p>
7150               Similarly we might see:
7151             </p>
7152 <div class="informaltable"><table border="1">
7153 <colgroup>
7154 <col>
7155 <col>
7156 <col>
7157 </colgroup>
7158 <tbody>
7159 <tr>
7160 <td>
7161                       <p>
7162                         <code class="literal">XX.LCS.MIT.EDU.</code>
7163                       </p>
7164                     </td>
7165 <td>
7166                       <p>
7167                         <code class="literal">IN A</code>
7168                       </p>
7169                     </td>
7170 <td>
7171                       <p>
7172                         <code class="literal">10.0.0.44</code>
7173                       </p>
7174                     </td>
7175 </tr>
7176 <tr>
7177 <td> </td>
7178 <td>
7179                       <p>
7180                         <code class="literal">CH A</code>
7181                       </p>
7182                     </td>
7183 <td>
7184                       <p>
7185                         <code class="literal">MIT.EDU. 2420</code>
7186                       </p>
7187                     </td>
7188 </tr>
7189 </tbody>
7190 </table></div>
7191 <p>
7192               This example shows two addresses for
7193               <code class="literal">XX.LCS.MIT.EDU</code>, each of a different class.
7194             </p>
7195 </div>
7196 </div>
7197 <div class="sect2" lang="en">
7198 <div class="titlepage"><div><div><h3 class="title">
7199 <a name="id2593300"></a>Discussion of MX Records</h3></div></div></div>
7200 <p>
7201             As described above, domain servers store information as a
7202             series of resource records, each of which contains a particular
7203             piece of information about a given domain name (which is usually,
7204             but not always, a host). The simplest way to think of a RR is as
7205             a typed pair of data, a domain name matched with a relevant datum,
7206             and stored with some additional type information to help systems
7207             determine when the RR is relevant.
7208           </p>
7209 <p>
7210             MX records are used to control delivery of email. The data
7211             specified in the record is a priority and a domain name. The
7212             priority
7213             controls the order in which email delivery is attempted, with the
7214             lowest number first. If two priorities are the same, a server is
7215             chosen randomly. If no servers at a given priority are responding,
7216             the mail transport agent will fall back to the next largest
7217             priority.
7218             Priority numbers do not have any absolute meaning &#8212; they are
7219             relevant
7220             only respective to other MX records for that domain name. The
7221             domain
7222             name given is the machine to which the mail will be delivered.
7223             It <span class="emphasis"><em>must</em></span> have an associated address record
7224             (A or AAAA) &#8212; CNAME is not sufficient.
7225           </p>
7226 <p>
7227             For a given domain, if there is both a CNAME record and an
7228             MX record, the MX record is in error, and will be ignored.
7229             Instead,
7230             the mail will be delivered to the server specified in the MX
7231             record
7232             pointed to by the CNAME.
7233             For example:
7234           </p>
7235 <div class="informaltable"><table border="1">
7236 <colgroup>
7237 <col>
7238 <col>
7239 <col>
7240 <col>
7241 <col>
7242 </colgroup>
7243 <tbody>
7244 <tr>
7245 <td>
7246                     <p>
7247                       <code class="literal">example.com.</code>
7248                     </p>
7249                   </td>
7250 <td>
7251                     <p>
7252                       <code class="literal">IN</code>
7253                     </p>
7254                   </td>
7255 <td>
7256                     <p>
7257                       <code class="literal">MX</code>
7258                     </p>
7259                   </td>
7260 <td>
7261                     <p>
7262                       <code class="literal">10</code>
7263                     </p>
7264                   </td>
7265 <td>
7266                     <p>
7267                       <code class="literal">mail.example.com.</code>
7268                     </p>
7269                   </td>
7270 </tr>
7271 <tr>
7272 <td>
7273                     <p></p>
7274                   </td>
7275 <td>
7276                     <p>
7277                       <code class="literal">IN</code>
7278                     </p>
7279                   </td>
7280 <td>
7281                     <p>
7282                       <code class="literal">MX</code>
7283                     </p>
7284                   </td>
7285 <td>
7286                     <p>
7287                       <code class="literal">10</code>
7288                     </p>
7289                   </td>
7290 <td>
7291                     <p>
7292                       <code class="literal">mail2.example.com.</code>
7293                     </p>
7294                   </td>
7295 </tr>
7296 <tr>
7297 <td>
7298                     <p></p>
7299                   </td>
7300 <td>
7301                     <p>
7302                       <code class="literal">IN</code>
7303                     </p>
7304                   </td>
7305 <td>
7306                     <p>
7307                       <code class="literal">MX</code>
7308                     </p>
7309                   </td>
7310 <td>
7311                     <p>
7312                       <code class="literal">20</code>
7313                     </p>
7314                   </td>
7315 <td>
7316                     <p>
7317                       <code class="literal">mail.backup.org.</code>
7318                     </p>
7319                   </td>
7320 </tr>
7321 <tr>
7322 <td>
7323                     <p>
7324                       <code class="literal">mail.example.com.</code>
7325                     </p>
7326                   </td>
7327 <td>
7328                     <p>
7329                       <code class="literal">IN</code>
7330                     </p>
7331                   </td>
7332 <td>
7333                     <p>
7334                       <code class="literal">A</code>
7335                     </p>
7336                   </td>
7337 <td>
7338                     <p>
7339                       <code class="literal">10.0.0.1</code>
7340                     </p>
7341                   </td>
7342 <td>
7343                     <p></p>
7344                   </td>
7345 </tr>
7346 <tr>
7347 <td>
7348                     <p>
7349                       <code class="literal">mail2.example.com.</code>
7350                     </p>
7351                   </td>
7352 <td>
7353                     <p>
7354                       <code class="literal">IN</code>
7355                     </p>
7356                   </td>
7357 <td>
7358                     <p>
7359                       <code class="literal">A</code>
7360                     </p>
7361                   </td>
7362 <td>
7363                     <p>
7364                       <code class="literal">10.0.0.2</code>
7365                     </p>
7366                   </td>
7367 <td>
7368                     <p></p>
7369                   </td>
7370 </tr>
7371 </tbody>
7372 </table></div>
7373 <p>
7374             Mail delivery will be attempted to <code class="literal">mail.example.com</code> and
7375             <code class="literal">mail2.example.com</code> (in
7376             any order), and if neither of those succeed, delivery to <code class="literal">mail.backup.org</code> will
7377             be attempted.
7378           </p>
7379 </div>
7380 <div class="sect2" lang="en">
7381 <div class="titlepage"><div><div><h3 class="title">
7382 <a name="Setting_TTLs"></a>Setting TTLs</h3></div></div></div>
7383 <p>
7384             The time-to-live of the RR field is a 32-bit integer represented
7385             in units of seconds, and is primarily used by resolvers when they
7386             cache RRs. The TTL describes how long a RR can be cached before it
7387             should be discarded. The following three types of TTL are
7388             currently
7389             used in a zone file.
7390           </p>
7391 <div class="informaltable"><table border="1">
7392 <colgroup>
7393 <col>
7394 <col>
7395 </colgroup>
7396 <tbody>
7397 <tr>
7398 <td>
7399                     <p>
7400                       SOA
7401                     </p>
7402                   </td>
7403 <td>
7404                     <p>
7405                       The last field in the SOA is the negative
7406                       caching TTL. This controls how long other servers will
7407                       cache no-such-domain
7408                       (NXDOMAIN) responses from you.
7409                     </p>
7410                     <p>
7411                       The maximum time for
7412                       negative caching is 3 hours (3h).
7413                     </p>
7414                   </td>
7415 </tr>
7416 <tr>
7417 <td>
7418                     <p>
7419                       $TTL
7420                     </p>
7421                   </td>
7422 <td>
7423                     <p>
7424                       The $TTL directive at the top of the
7425                       zone file (before the SOA) gives a default TTL for every
7426                       RR without
7427                       a specific TTL set.
7428                     </p>
7429                   </td>
7430 </tr>
7431 <tr>
7432 <td>
7433                     <p>
7434                       RR TTLs
7435                     </p>
7436                   </td>
7437 <td>
7438                     <p>
7439                       Each RR can have a TTL as the second
7440                       field in the RR, which will control how long other
7441                       servers can cache
7442                       the it.
7443                     </p>
7444                   </td>
7445 </tr>
7446 </tbody>
7447 </table></div>
7448 <p>
7449             All of these TTLs default to units of seconds, though units
7450             can be explicitly specified, for example, <code class="literal">1h30m</code>.
7451           </p>
7452 </div>
7453 <div class="sect2" lang="en">
7454 <div class="titlepage"><div><div><h3 class="title">
7455 <a name="id2593915"></a>Inverse Mapping in IPv4</h3></div></div></div>
7456 <p>
7457             Reverse name resolution (that is, translation from IP address
7458             to name) is achieved by means of the <span class="emphasis"><em>in-addr.arpa</em></span> domain
7459             and PTR records. Entries in the in-addr.arpa domain are made in
7460             least-to-most significant order, read left to right. This is the
7461             opposite order to the way IP addresses are usually written. Thus,
7462             a machine with an IP address of 10.1.2.3 would have a
7463             corresponding
7464             in-addr.arpa name of
7465             3.2.1.10.in-addr.arpa. This name should have a PTR resource record
7466             whose data field is the name of the machine or, optionally,
7467             multiple
7468             PTR records if the machine has more than one name. For example,
7469             in the [<span class="optional">example.com</span>] domain:
7470           </p>
7471 <div class="informaltable"><table border="1">
7472 <colgroup>
7473 <col>
7474 <col>
7475 </colgroup>
7476 <tbody>
7477 <tr>
7478 <td>
7479                     <p>
7480                       <code class="literal">$ORIGIN</code>
7481                     </p>
7482                   </td>
7483 <td>
7484                     <p>
7485                       <code class="literal">2.1.10.in-addr.arpa</code>
7486                     </p>
7487                   </td>
7488 </tr>
7489 <tr>
7490 <td>
7491                     <p>
7492                       <code class="literal">3</code>
7493                     </p>
7494                   </td>
7495 <td>
7496                     <p>
7497                       <code class="literal">IN PTR foo.example.com.</code>
7498                     </p>
7499                   </td>
7500 </tr>
7501 </tbody>
7502 </table></div>
7503 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
7504 <h3 class="title">Note</h3>
7505 <p>
7506               The <span><strong class="command">$ORIGIN</strong></span> lines in the examples
7507               are for providing context to the examples only &#8212; they do not
7508               necessarily
7509               appear in the actual usage. They are only used here to indicate
7510               that the example is relative to the listed origin.
7511             </p>
7512 </div>
7513 </div>
7514 <div class="sect2" lang="en">
7515 <div class="titlepage"><div><div><h3 class="title">
7516 <a name="id2594042"></a>Other Zone File Directives</h3></div></div></div>
7517 <p>
7518             The Master File Format was initially defined in RFC 1035 and
7519             has subsequently been extended. While the Master File Format
7520             itself
7521             is class independent all records in a Master File must be of the
7522             same
7523             class.
7524           </p>
7525 <p>
7526             Master File Directives include <span><strong class="command">$ORIGIN</strong></span>, <span><strong class="command">$INCLUDE</strong></span>,
7527             and <span><strong class="command">$TTL.</strong></span>
7528           </p>
7529 <div class="sect3" lang="en">
7530 <div class="titlepage"><div><div><h4 class="title">
7531 <a name="id2594201"></a>The <span><strong class="command">$ORIGIN</strong></span> Directive</h4></div></div></div>
7532 <p>
7533               Syntax: <span><strong class="command">$ORIGIN</strong></span>
7534               <em class="replaceable"><code>domain-name</code></em>
7535               [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
7536             </p>
7537 <p><span><strong class="command">$ORIGIN</strong></span>
7538               sets the domain name that will be appended to any
7539               unqualified records. When a zone is first read in there
7540               is an implicit <span><strong class="command">$ORIGIN</strong></span>
7541               &lt;<code class="varname">zone-name</code>&gt;<span><strong class="command">.</strong></span>
7542               The current <span><strong class="command">$ORIGIN</strong></span> is appended to
7543               the domain specified in the <span><strong class="command">$ORIGIN</strong></span>
7544               argument if it is not absolute.
7545             </p>
7546 <pre class="programlisting">
7547 $ORIGIN example.com.
7548 WWW     CNAME   MAIN-SERVER
7549 </pre>
7550 <p>
7551               is equivalent to
7552             </p>
7553 <pre class="programlisting">
7554 WWW.EXAMPLE.COM. CNAME MAIN-SERVER.EXAMPLE.COM.
7555 </pre>
7556 </div>
7557 <div class="sect3" lang="en">
7558 <div class="titlepage"><div><div><h4 class="title">
7559 <a name="id2594262"></a>The <span><strong class="command">$INCLUDE</strong></span> Directive</h4></div></div></div>
7560 <p>
7561               Syntax: <span><strong class="command">$INCLUDE</strong></span>
7562               <em class="replaceable"><code>filename</code></em>
7563               [<span class="optional">
7564 <em class="replaceable"><code>origin</code></em> </span>]
7565               [<span class="optional"> <em class="replaceable"><code>comment</code></em> </span>]
7566             </p>
7567 <p>
7568               Read and process the file <code class="filename">filename</code> as
7569               if it were included into the file at this point.  If <span><strong class="command">origin</strong></span> is
7570               specified the file is processed with <span><strong class="command">$ORIGIN</strong></span> set
7571               to that value, otherwise the current <span><strong class="command">$ORIGIN</strong></span> is
7572               used.
7573             </p>
7574 <p>
7575               The origin and the current domain name
7576               revert to the values they had prior to the <span><strong class="command">$INCLUDE</strong></span> once
7577               the file has been read.
7578             </p>
7579 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
7580 <h3 class="title">Note</h3>
7581 <p>
7582                 RFC 1035 specifies that the current origin should be restored
7583                 after
7584                 an <span><strong class="command">$INCLUDE</strong></span>, but it is silent
7585                 on whether the current
7586                 domain name should also be restored.  BIND 9 restores both of
7587                 them.
7588                 This could be construed as a deviation from RFC 1035, a
7589                 feature, or both.
7590               </p>
7591 </div>
7592 </div>
7593 <div class="sect3" lang="en">
7594 <div class="titlepage"><div><div><h4 class="title">
7595 <a name="id2594331"></a>The <span><strong class="command">$TTL</strong></span> Directive</h4></div></div></div>
7596 <p>
7597               Syntax: <span><strong class="command">$TTL</strong></span>
7598               <em class="replaceable"><code>default-ttl</code></em>
7599               [<span class="optional">
7600 <em class="replaceable"><code>comment</code></em> </span>]
7601             </p>
7602 <p>
7603               Set the default Time To Live (TTL) for subsequent records
7604               with undefined TTLs. Valid TTLs are of the range 0-2147483647
7605               seconds.
7606             </p>
7607 <p><span><strong class="command">$TTL</strong></span>
7608                is defined in RFC 2308.
7609             </p>
7610 </div>
7611 </div>
7612 <div class="sect2" lang="en">
7613 <div class="titlepage"><div><div><h3 class="title">
7614 <a name="id2594368"></a><acronym class="acronym">BIND</acronym> Master File Extension: the  <span><strong class="command">$GENERATE</strong></span> Directive</h3></div></div></div>
7615 <p>
7616             Syntax: <span><strong class="command">$GENERATE</strong></span>
7617             <em class="replaceable"><code>range</code></em>
7618             <em class="replaceable"><code>lhs</code></em>
7619             [<span class="optional"><em class="replaceable"><code>ttl</code></em></span>]
7620             [<span class="optional"><em class="replaceable"><code>class</code></em></span>]
7621             <em class="replaceable"><code>type</code></em>
7622             <em class="replaceable"><code>rhs</code></em>
7623             [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
7624           </p>
7625 <p><span><strong class="command">$GENERATE</strong></span>
7626             is used to create a series of resource records that only
7627             differ from each other by an
7628             iterator. <span><strong class="command">$GENERATE</strong></span> can be used to
7629             easily generate the sets of records required to support
7630             sub /24 reverse delegations described in RFC 2317:
7631             Classless IN-ADDR.ARPA delegation.
7632           </p>
7633 <pre class="programlisting">$ORIGIN 0.0.192.IN-ADDR.ARPA.
7634 $GENERATE 1-2 0 NS SERVER$.EXAMPLE.
7635 $GENERATE 1-127 $ CNAME $.0</pre>
7636 <p>
7637             is equivalent to
7638           </p>
7639 <pre class="programlisting">0.0.0.192.IN-ADDR.ARPA. NS SERVER1.EXAMPLE.
7640 0.0.0.192.IN-ADDR.ARPA. NS SERVER2.EXAMPLE.
7641 1.0.0.192.IN-ADDR.ARPA. CNAME 1.0.0.0.192.IN-ADDR.ARPA.
7642 2.0.0.192.IN-ADDR.ARPA. CNAME 2.0.0.0.192.IN-ADDR.ARPA.
7643 ...
7644 127.0.0.192.IN-ADDR.ARPA. CNAME 127.0.0.0.192.IN-ADDR.ARPA.
7645 </pre>
7646 <div class="informaltable"><table border="1">
7647 <colgroup>
7648 <col>
7649 <col>
7650 </colgroup>
7651 <tbody>
7652 <tr>
7653 <td>
7654                     <p><span><strong class="command">range</strong></span></p>
7655                   </td>
7656 <td>
7657                     <p>
7658                       This can be one of two forms: start-stop
7659                       or start-stop/step. If the first form is used, then step
7660                       is set to
7661                       1. All of start, stop and step must be positive.
7662                     </p>
7663                   </td>
7664 </tr>
7665 <tr>
7666 <td>
7667                     <p><span><strong class="command">lhs</strong></span></p>
7668                   </td>
7669 <td>
7670                     <p>This
7671                       describes the owner name of the resource records
7672                       to be created.  Any single <span><strong class="command">$</strong></span>
7673                       (dollar sign)
7674                       symbols within the <span><strong class="command">lhs</strong></span> string
7675                       are replaced by the iterator value.
7676
7677                       To get a $ in the output, you need to escape the
7678                       <span><strong class="command">$</strong></span> using a backslash
7679                       <span><strong class="command">\</strong></span>,
7680                       e.g. <span><strong class="command">\$</strong></span>. The
7681                       <span><strong class="command">$</strong></span> may optionally be followed
7682                       by modifiers which change the offset from the
7683                       iterator, field width and base.
7684
7685                       Modifiers are introduced by a
7686                       <span><strong class="command">{</strong></span> (left brace) immediately following the
7687                       <span><strong class="command">$</strong></span> as
7688                       <span><strong class="command">${offset[,width[,base]]}</strong></span>.
7689                       For example, <span><strong class="command">${-20,3,d}</strong></span>
7690                       subtracts 20 from the current value, prints the
7691                       result as a decimal in a zero-padded field of
7692                       width 3.
7693
7694                       Available output forms are decimal
7695                       (<span><strong class="command">d</strong></span>), octal
7696                       (<span><strong class="command">o</strong></span>) and hexadecimal
7697                       (<span><strong class="command">x</strong></span> or <span><strong class="command">X</strong></span>
7698                       for uppercase).  The default modifier is
7699                       <span><strong class="command">${0,0,d}</strong></span>.  If the
7700                       <span><strong class="command">lhs</strong></span> is not absolute, the
7701                       current <span><strong class="command">$ORIGIN</strong></span> is appended
7702                       to the name.
7703                     </p>
7704                     <p>
7705                       For compatibility with earlier versions, <span><strong class="command">$$</strong></span> is still
7706                       recognized as indicating a literal $ in the output.
7707                     </p>
7708                   </td>
7709 </tr>
7710 <tr>
7711 <td>
7712                     <p><span><strong class="command">ttl</strong></span></p>
7713                   </td>
7714 <td>
7715                     <p>
7716                       Specifies the time-to-live of the generated records. If
7717                       not specified this will be inherited using the
7718                       normal TTL inheritance rules.
7719                     </p>
7720                     <p><span><strong class="command">class</strong></span>
7721                       and <span><strong class="command">ttl</strong></span> can be
7722                       entered in either order.
7723                     </p>
7724                   </td>
7725 </tr>
7726 <tr>
7727 <td>
7728                     <p><span><strong class="command">class</strong></span></p>
7729                   </td>
7730 <td>
7731                     <p>
7732                       Specifies the class of the generated records.
7733                       This must match the zone class if it is
7734                       specified.
7735                     </p>
7736                     <p><span><strong class="command">class</strong></span>
7737                       and <span><strong class="command">ttl</strong></span> can be
7738                       entered in either order.
7739                     </p>
7740                   </td>
7741 </tr>
7742 <tr>
7743 <td>
7744                     <p><span><strong class="command">type</strong></span></p>
7745                   </td>
7746 <td>
7747                     <p>
7748                       At present the only supported types are
7749                       PTR, CNAME, DNAME, A, AAAA and NS.
7750                     </p>
7751                   </td>
7752 </tr>
7753 <tr>
7754 <td>
7755                     <p><span><strong class="command">rhs</strong></span></p>
7756                   </td>
7757 <td>
7758                     <p>
7759                       <span><strong class="command">rhs</strong></span> is a domain name. It is processed
7760                       similarly to lhs.
7761                     </p>
7762                   </td>
7763 </tr>
7764 </tbody>
7765 </table></div>
7766 <p>
7767             The <span><strong class="command">$GENERATE</strong></span> directive is a <acronym class="acronym">BIND</acronym> extension
7768             and not part of the standard zone file format.
7769           </p>
7770 <p>
7771             BIND 8 does not support the optional TTL and CLASS fields.
7772           </p>
7773 </div>
7774 <div class="sect2" lang="en">
7775 <div class="titlepage"><div><div><h3 class="title">
7776 <a name="zonefile_format"></a>Additional File Formats</h3></div></div></div>
7777 <p>
7778             In addition to the standard textual format, BIND 9
7779             supports the ability to read or dump to zone files in
7780             other formats.  The <code class="constant">raw</code> format is
7781             currently available as an additional format.  It is a
7782             binary format representing BIND 9's internal data
7783             structure directly, thereby remarkably improving the
7784             loading time.
7785           </p>
7786 <p>
7787             For a primary server, a zone file in the
7788             <code class="constant">raw</code> format is expected to be
7789             generated from a textual zone file by the
7790             <span><strong class="command">named-compilezone</strong></span> command.  For a
7791             secondary server or for a dynamic zone, it is automatically
7792             generated (if this format is specified by the
7793             <span><strong class="command">masterfile-format</strong></span> option) when
7794             <span><strong class="command">named</strong></span> dumps the zone contents after
7795             zone transfer or when applying prior updates.
7796           </p>
7797 <p>
7798             If a zone file in a binary format needs manual modification,
7799             it first must be converted to a textual form by the
7800             <span><strong class="command">named-compilezone</strong></span> command.  All
7801             necessary modification should go to the text file, which
7802             should then be converted to the binary form by the
7803             <span><strong class="command">named-compilezone</strong></span> command again.
7804           </p>
7805 <p>
7806              Although the <code class="constant">raw</code> format uses the
7807              network byte order and avoids architecture-dependent
7808              data alignment so that it is as much portable as
7809              possible, it is primarily expected to be used inside
7810              the same single system.  In order to export a zone
7811              file in the <code class="constant">raw</code> format or make a
7812              portable backup of the file, it is recommended to
7813              convert the file to the standard textual representation.
7814           </p>
7815 </div>
7816 </div>
7817 <div class="sect1" lang="en">
7818 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
7819 <a name="statistics"></a>BIND9 Statistics</h2></div></div></div>
7820 <p>
7821           <acronym class="acronym">BIND</acronym> 9 maintains lots of statistics
7822           information and provides several interfaces for users to
7823           get access to the statistics.
7824           The available statistics include all statistics counters
7825           that were available in <acronym class="acronym">BIND</acronym> 8 and
7826           are meaningful in <acronym class="acronym">BIND</acronym> 9,
7827           and other information that is considered useful.
7828         </p>
7829 <p>
7830           The statistics information is categorized into the following
7831           sections.
7832         </p>
7833 <div class="informaltable"><table border="1">
7834 <colgroup>
7835 <col>
7836 <col>
7837 </colgroup>
7838 <tbody>
7839 <tr>
7840 <td>
7841                   <p>Incoming Requests</p>
7842                 </td>
7843 <td>
7844                   <p>
7845                     The number of incoming DNS requests for each OPCODE.
7846                   </p>
7847                 </td>
7848 </tr>
7849 <tr>
7850 <td>
7851                   <p>Incoming Queries</p>
7852                 </td>
7853 <td>
7854                   <p>
7855                     The number of incoming queries for each RR type.
7856                   </p>
7857                 </td>
7858 </tr>
7859 <tr>
7860 <td>
7861                   <p>Outgoing Queries</p>
7862                 </td>
7863 <td>
7864                   <p>
7865                     The number of outgoing queries for each RR
7866                     type sent from the internal resolver.
7867                     Maintained per view.
7868                   </p>
7869                 </td>
7870 </tr>
7871 <tr>
7872 <td>
7873                   <p>Name Server Statistics</p>
7874                 </td>
7875 <td>
7876                   <p>
7877                     Statistics counters about incoming request processing.
7878                   </p>
7879                 </td>
7880 </tr>
7881 <tr>
7882 <td>
7883                   <p>Zone Maintenance Statistics</p>
7884                 </td>
7885 <td>
7886                   <p>
7887                     Statistics counters regarding zone maintenance
7888                     operations such as zone transfers.
7889                   </p>
7890                 </td>
7891 </tr>
7892 <tr>
7893 <td>
7894                   <p>Resolver Statistics</p>
7895                 </td>
7896 <td>
7897                   <p>
7898                     Statistics counters about name resolution
7899                     performed in the internal resolver.
7900                     Maintained per view.
7901                   </p>
7902                 </td>
7903 </tr>
7904 <tr>
7905 <td>
7906                   <p>Cache DB RRsets</p>
7907                 </td>
7908 <td>
7909                   <p>
7910                     The number of RRsets per RR type (positive
7911                     or negative) and nonexistent names stored in the
7912                     cache database.
7913                     Maintained per view.
7914                   </p>
7915                 </td>
7916 </tr>
7917 <tr>
7918 <td>
7919                   <p>Socket I/O Statistics</p>
7920                 </td>
7921 <td>
7922                   <p>
7923                     Statistics counters about network related events.
7924                   </p>
7925                 </td>
7926 </tr>
7927 </tbody>
7928 </table></div>
7929 <p>
7930           A subset of Name Server Statistics is collected and shown
7931           per zone for which the server has the authority when
7932           <span><strong class="command">zone-statistics</strong></span> is set to
7933           <strong class="userinput"><code>yes</code></strong>.
7934           These statistics counters are shown with their zone and view
7935           names.
7936           In some cases the view names are omitted for the default view.
7937         </p>
7938 <p>
7939           There are currently two user interfaces to get access to the
7940           statistics.
7941           One is in the plain text format dumped to the file specified
7942           by the <span><strong class="command">statistics-file</strong></span> configuration option.
7943           The other is remotely accessible via a statistics channel
7944           when the <span><strong class="command">statistics-channels</strong></span> statement
7945           is specified in the configuration file
7946           (see <a href="Bv9ARM.ch06.html#statschannels" title="statistics-channels Statement Grammar">the section called &#8220;<span><strong class="command">statistics-channels</strong></span> Statement Grammar&#8221;</a>.)
7947         </p>
7948 <div class="sect3" lang="en">
7949 <div class="titlepage"><div><div><h4 class="title">
7950 <a name="statsfile"></a>The Statistics File</h4></div></div></div>
7951 <p>
7952             The text format statistics dump begins with a line, like:
7953           </p>
7954 <p>
7955             <span><strong class="command">+++ Statistics Dump +++ (973798949)</strong></span>
7956           </p>
7957 <p>
7958             The number in parentheses is a standard
7959             Unix-style timestamp, measured as seconds since January 1, 1970.
7960
7961             Following
7962             that line is a set of statistics information, which is categorized
7963             as described above.
7964             Each section begins with a line, like:
7965           </p>
7966 <p>
7967             <span><strong class="command">++ Name Server Statistics ++</strong></span>
7968           </p>
7969 <p>
7970             Each section consists of lines, each containing the statistics
7971             counter value followed by its textual description.
7972             See below for available counters.
7973             For brevity, counters that have a value of 0 are not shown
7974             in the statistics file.
7975           </p>
7976 <p>
7977             The statistics dump ends with the line where the
7978             number is identical to the number in the beginning line; for example:
7979           </p>
7980 <p>
7981             <span><strong class="command">--- Statistics Dump --- (973798949)</strong></span>
7982           </p>
7983 </div>
7984 <div class="sect2" lang="en">
7985 <div class="titlepage"><div><div><h3 class="title">
7986 <a name="statistics_counters"></a>Statistics Counters</h3></div></div></div>
7987 <p>
7988             The following tables summarize statistics counters that
7989             <acronym class="acronym">BIND</acronym> 9 provides.
7990             For each row of the tables, the leftmost column is the
7991             abbreviated symbol name of that counter.
7992             These symbols are shown in the statistics information
7993             accessed via an HTTP statistics channel.
7994             The rightmost column gives the description of the counter,
7995             which is also shown in the statistics file
7996             (but, in this document, possibly with slight modification
7997             for better readability).
7998             Additional notes may also be provided in this column.
7999             When a middle column exists between these two columns,
8000             it gives the corresponding counter name of the
8001             <acronym class="acronym">BIND</acronym> 8 statistics, if applicable.
8002           </p>
8003 <div class="sect3" lang="en">
8004 <div class="titlepage"><div><div><h4 class="title">
8005 <a name="id2595364"></a>Name Server Statistics Counters</h4></div></div></div>
8006 <div class="informaltable"><table border="1">
8007 <colgroup>
8008 <col>
8009 <col>
8010 <col>
8011 </colgroup>
8012 <tbody>
8013 <tr>
8014 <td>
8015                       <p>
8016                         <span class="emphasis"><em>Symbol</em></span>
8017                       </p>
8018                     </td>
8019 <td>
8020                       <p>
8021                         <span class="emphasis"><em>BIND8 Symbol</em></span>
8022                       </p>
8023                     </td>
8024 <td>
8025                       <p>
8026                         <span class="emphasis"><em>Description</em></span>
8027                       </p>
8028                     </td>
8029 </tr>
8030 <tr>
8031 <td>
8032                       <p><span><strong class="command">Requestv4</strong></span></p>
8033                     </td>
8034 <td>
8035                       <p><span><strong class="command">RQ</strong></span></p>
8036                     </td>
8037 <td>
8038                       <p>
8039                         IPv4 requests received.
8040                         Note: this also counts non query requests.
8041                       </p>
8042                     </td>
8043 </tr>
8044 <tr>
8045 <td>
8046                       <p><span><strong class="command">Requestv6</strong></span></p>
8047                     </td>
8048 <td>
8049                       <p><span><strong class="command">RQ</strong></span></p>
8050                     </td>
8051 <td>
8052                       <p>
8053                         IPv6 requests received.
8054                         Note: this also counts non query requests.
8055                       </p>
8056                     </td>
8057 </tr>
8058 <tr>
8059 <td>
8060                       <p><span><strong class="command">ReqEdns0</strong></span></p>
8061                     </td>
8062 <td>
8063                       <p><span><strong class="command"></strong></span></p>
8064                     </td>
8065 <td>
8066                       <p>
8067                         Requests with EDNS(0) received.
8068                       </p>
8069                     </td>
8070 </tr>
8071 <tr>
8072 <td>
8073                       <p><span><strong class="command">ReqBadEDNSVer</strong></span></p>
8074                     </td>
8075 <td>
8076                       <p><span><strong class="command"></strong></span></p>
8077                     </td>
8078 <td>
8079                       <p>
8080                         Requests with unsupported EDNS version received.
8081                       </p>
8082                     </td>
8083 </tr>
8084 <tr>
8085 <td>
8086                       <p><span><strong class="command">ReqTSIG</strong></span></p>
8087                     </td>
8088 <td>
8089                       <p><span><strong class="command"></strong></span></p>
8090                     </td>
8091 <td>
8092                       <p>
8093                         Requests with TSIG received.
8094                       </p>
8095                     </td>
8096 </tr>
8097 <tr>
8098 <td>
8099                       <p><span><strong class="command">ReqSIG0</strong></span></p>
8100                     </td>
8101 <td>
8102                       <p><span><strong class="command"></strong></span></p>
8103                     </td>
8104 <td>
8105                       <p>
8106                         Requests with SIG(0) received.
8107                       </p>
8108                     </td>
8109 </tr>
8110 <tr>
8111 <td>
8112                       <p><span><strong class="command">ReqBadSIG</strong></span></p>
8113                     </td>
8114 <td>
8115                       <p><span><strong class="command"></strong></span></p>
8116                     </td>
8117 <td>
8118                       <p>
8119                         Requests with invalid (TSIG or SIG(0)) signature.
8120                       </p>
8121                     </td>
8122 </tr>
8123 <tr>
8124 <td>
8125                       <p><span><strong class="command">ReqTCP</strong></span></p>
8126                     </td>
8127 <td>
8128                       <p><span><strong class="command">RTCP</strong></span></p>
8129                     </td>
8130 <td>
8131                       <p>
8132                         TCP requests received.
8133                       </p>
8134                     </td>
8135 </tr>
8136 <tr>
8137 <td>
8138                       <p><span><strong class="command">AuthQryRej</strong></span></p>
8139                     </td>
8140 <td>
8141                       <p><span><strong class="command">RUQ</strong></span></p>
8142                     </td>
8143 <td>
8144                       <p>
8145                         Authoritative (non recursive) queries rejected.
8146                       </p>
8147                     </td>
8148 </tr>
8149 <tr>
8150 <td>
8151                       <p><span><strong class="command">RecQryRej</strong></span></p>
8152                     </td>
8153 <td>
8154                       <p><span><strong class="command">RURQ</strong></span></p>
8155                     </td>
8156 <td>
8157                       <p>
8158                         Recursive queries rejected.
8159                       </p>
8160                     </td>
8161 </tr>
8162 <tr>
8163 <td>
8164                       <p><span><strong class="command">XfrRej</strong></span></p>
8165                     </td>
8166 <td>
8167                       <p><span><strong class="command">RUXFR</strong></span></p>
8168                     </td>
8169 <td>
8170                       <p>
8171                         Zone transfer requests rejected.
8172                       </p>
8173                     </td>
8174 </tr>
8175 <tr>
8176 <td>
8177                       <p><span><strong class="command">UpdateRej</strong></span></p>
8178                     </td>
8179 <td>
8180                       <p><span><strong class="command">RUUpd</strong></span></p>
8181                     </td>
8182 <td>
8183                       <p>
8184                         Dynamic update requests rejected.
8185                       </p>
8186                     </td>
8187 </tr>
8188 <tr>
8189 <td>
8190                       <p><span><strong class="command">Response</strong></span></p>
8191                     </td>
8192 <td>
8193                       <p><span><strong class="command">SAns</strong></span></p>
8194                     </td>
8195 <td>
8196                       <p>
8197                         Responses sent.
8198                       </p>
8199                     </td>
8200 </tr>
8201 <tr>
8202 <td>
8203                       <p><span><strong class="command">RespTruncated</strong></span></p>
8204                     </td>
8205 <td>
8206                       <p><span><strong class="command"></strong></span></p>
8207                     </td>
8208 <td>
8209                       <p>
8210                         Truncated responses sent.
8211                       </p>
8212                     </td>
8213 </tr>
8214 <tr>
8215 <td>
8216                       <p><span><strong class="command">RespEDNS0</strong></span></p>
8217                     </td>
8218 <td>
8219                       <p><span><strong class="command"></strong></span></p>
8220                     </td>
8221 <td>
8222                       <p>
8223                         Responses with EDNS(0) sent.
8224                       </p>
8225                     </td>
8226 </tr>
8227 <tr>
8228 <td>
8229                       <p><span><strong class="command">RespTSIG</strong></span></p>
8230                     </td>
8231 <td>
8232                       <p><span><strong class="command"></strong></span></p>
8233                     </td>
8234 <td>
8235                       <p>
8236                         Responses with TSIG sent.
8237                       </p>
8238                     </td>
8239 </tr>
8240 <tr>
8241 <td>
8242                       <p><span><strong class="command">RespSIG0</strong></span></p>
8243                     </td>
8244 <td>
8245                       <p><span><strong class="command"></strong></span></p>
8246                     </td>
8247 <td>
8248                       <p>
8249                         Responses with SIG(0) sent.
8250                       </p>
8251                     </td>
8252 </tr>
8253 <tr>
8254 <td>
8255                       <p><span><strong class="command">QrySuccess</strong></span></p>
8256                     </td>
8257 <td>
8258                       <p><span><strong class="command"></strong></span></p>
8259                     </td>
8260 <td>
8261                       <p>
8262                         Queries resulted in a successful answer.
8263                         This means the query which returns a NOERROR response
8264                         with at least one answer RR.
8265                         This corresponds to the
8266                         <span><strong class="command">success</strong></span> counter
8267                         of previous versions of
8268                         <acronym class="acronym">BIND</acronym> 9.
8269                       </p>
8270                     </td>
8271 </tr>
8272 <tr>
8273 <td>
8274                       <p><span><strong class="command">QryAuthAns</strong></span></p>
8275                     </td>
8276 <td>
8277                       <p><span><strong class="command"></strong></span></p>
8278                     </td>
8279 <td>
8280                       <p>
8281                         Queries resulted in authoritative answer.
8282                       </p>
8283                     </td>
8284 </tr>
8285 <tr>
8286 <td>
8287                       <p><span><strong class="command">QryNoauthAns</strong></span></p>
8288                     </td>
8289 <td>
8290                       <p><span><strong class="command">SNaAns</strong></span></p>
8291                     </td>
8292 <td>
8293                       <p>
8294                         Queries resulted in non authoritative answer.
8295                       </p>
8296                     </td>
8297 </tr>
8298 <tr>
8299 <td>
8300                       <p><span><strong class="command">QryReferral</strong></span></p>
8301                     </td>
8302 <td>
8303                       <p><span><strong class="command"></strong></span></p>
8304                     </td>
8305 <td>
8306                       <p>
8307                         Queries resulted in referral answer.
8308                         This corresponds to the
8309                         <span><strong class="command">referral</strong></span> counter
8310                         of previous versions of
8311                         <acronym class="acronym">BIND</acronym> 9.
8312                       </p>
8313                     </td>
8314 </tr>
8315 <tr>
8316 <td>
8317                       <p><span><strong class="command">QryNxrrset</strong></span></p>
8318                     </td>
8319 <td>
8320                       <p><span><strong class="command"></strong></span></p>
8321                     </td>
8322 <td>
8323                       <p>
8324                         Queries resulted in NOERROR responses with no data.
8325                         This corresponds to the
8326                         <span><strong class="command">nxrrset</strong></span> counter
8327                         of previous versions of
8328                         <acronym class="acronym">BIND</acronym> 9.
8329                       </p>
8330                     </td>
8331 </tr>
8332 <tr>
8333 <td>
8334                       <p><span><strong class="command">QrySERVFAIL</strong></span></p>
8335                     </td>
8336 <td>
8337                       <p><span><strong class="command">SFail</strong></span></p>
8338                     </td>
8339 <td>
8340                       <p>
8341                         Queries resulted in SERVFAIL.
8342                       </p>
8343                     </td>
8344 </tr>
8345 <tr>
8346 <td>
8347                       <p><span><strong class="command">QryFORMERR</strong></span></p>
8348                     </td>
8349 <td>
8350                       <p><span><strong class="command">SFErr</strong></span></p>
8351                     </td>
8352 <td>
8353                       <p>
8354                         Queries resulted in FORMERR.
8355                       </p>
8356                     </td>
8357 </tr>
8358 <tr>
8359 <td>
8360                       <p><span><strong class="command">QryNXDOMAIN</strong></span></p>
8361                     </td>
8362 <td>
8363                       <p><span><strong class="command">SNXD</strong></span></p>
8364                     </td>
8365 <td>
8366                       <p>
8367                         Queries resulted in NXDOMAIN.
8368                         This corresponds to the
8369                         <span><strong class="command">nxdomain</strong></span> counter
8370                         of previous versions of
8371                         <acronym class="acronym">BIND</acronym> 9.
8372                       </p>
8373                     </td>
8374 </tr>
8375 <tr>
8376 <td>
8377                       <p><span><strong class="command">QryRecursion</strong></span></p>
8378                     </td>
8379 <td>
8380                       <p><span><strong class="command">RFwdQ</strong></span></p>
8381                     </td>
8382 <td>
8383                       <p>
8384                         Queries which caused the server
8385                         to perform recursion in order to find the final answer.
8386                         This corresponds to the
8387                         <span><strong class="command">recursion</strong></span> counter
8388                         of previous versions of
8389                         <acronym class="acronym">BIND</acronym> 9.
8390                       </p>
8391                     </td>
8392 </tr>
8393 <tr>
8394 <td>
8395                       <p><span><strong class="command">QryDuplicate</strong></span></p>
8396                     </td>
8397 <td>
8398                       <p><span><strong class="command">RDupQ</strong></span></p>
8399                     </td>
8400 <td>
8401                       <p>
8402                         Queries which the server attempted to
8403                         recurse but discovered an existing query with the same
8404                         IP address, port, query ID, name, type and class
8405                         already being processed.
8406                         This corresponds to the
8407                         <span><strong class="command">duplicate</strong></span> counter
8408                         of previous versions of
8409                         <acronym class="acronym">BIND</acronym> 9.
8410                       </p>
8411                     </td>
8412 </tr>
8413 <tr>
8414 <td>
8415                       <p><span><strong class="command">QryDropped</strong></span></p>
8416                     </td>
8417 <td>
8418                       <p><span><strong class="command"></strong></span></p>
8419                     </td>
8420 <td>
8421                       <p>
8422                         Recursive queries for which the server
8423                         discovered an excessive number of existing
8424                         recursive queries for the same name, type and
8425                         class and were subsequently dropped.
8426                         This is the number of dropped queries due to
8427                         the reason explained with the
8428                         <span><strong class="command">clients-per-query</strong></span>
8429                         and
8430                         <span><strong class="command">max-clients-per-query</strong></span>
8431                         options
8432                         (see the description about
8433                         <a href="Bv9ARM.ch06.html#clients-per-query"><span><strong class="command">clients-per-query</strong></span></a>.)
8434                         This corresponds to the
8435                         <span><strong class="command">dropped</strong></span> counter
8436                         of previous versions of
8437                         <acronym class="acronym">BIND</acronym> 9.
8438                       </p>
8439                     </td>
8440 </tr>
8441 <tr>
8442 <td>
8443                       <p><span><strong class="command">QryFailure</strong></span></p>
8444                     </td>
8445 <td>
8446                       <p><span><strong class="command"></strong></span></p>
8447                     </td>
8448 <td>
8449                       <p>
8450                         Other query failures.
8451                         This corresponds to the
8452                         <span><strong class="command">failure</strong></span> counter
8453                         of previous versions of
8454                         <acronym class="acronym">BIND</acronym> 9.
8455                         Note: this counter is provided mainly for
8456                         backward compatibility with the previous versions.
8457                         Normally a more fine-grained counters such as
8458                         <span><strong class="command">AuthQryRej</strong></span> and
8459                         <span><strong class="command">RecQryRej</strong></span>
8460                         that would also fall into this counter are provided,
8461                         and so this counter would not be of much
8462                         interest in practice.
8463                       </p>
8464                     </td>
8465 </tr>
8466 <tr>
8467 <td>
8468                       <p><span><strong class="command">XfrReqDone</strong></span></p>
8469                     </td>
8470 <td>
8471                       <p><span><strong class="command"></strong></span></p>
8472                     </td>
8473 <td>
8474                       <p>
8475                         Requested zone transfers completed.
8476                       </p>
8477                     </td>
8478 </tr>
8479 <tr>
8480 <td>
8481                       <p><span><strong class="command">UpdateReqFwd</strong></span></p>
8482                     </td>
8483 <td>
8484                       <p><span><strong class="command"></strong></span></p>
8485                     </td>
8486 <td>
8487                       <p>
8488                         Update requests forwarded.
8489                       </p>
8490                     </td>
8491 </tr>
8492 <tr>
8493 <td>
8494                       <p><span><strong class="command">UpdateRespFwd</strong></span></p>
8495                     </td>
8496 <td>
8497                       <p><span><strong class="command"></strong></span></p>
8498                     </td>
8499 <td>
8500                       <p>
8501                         Update responses forwarded.
8502                       </p>
8503                     </td>
8504 </tr>
8505 <tr>
8506 <td>
8507                       <p><span><strong class="command">UpdateFwdFail</strong></span></p>
8508                     </td>
8509 <td>
8510                       <p><span><strong class="command"></strong></span></p>
8511                     </td>
8512 <td>
8513                       <p>
8514                         Dynamic update forward failed.
8515                       </p>
8516                     </td>
8517 </tr>
8518 <tr>
8519 <td>
8520                       <p><span><strong class="command">UpdateDone</strong></span></p>
8521                     </td>
8522 <td>
8523                       <p><span><strong class="command"></strong></span></p>
8524                     </td>
8525 <td>
8526                       <p>
8527                         Dynamic updates completed.
8528                       </p>
8529                     </td>
8530 </tr>
8531 <tr>
8532 <td>
8533                       <p><span><strong class="command">UpdateFail</strong></span></p>
8534                     </td>
8535 <td>
8536                       <p><span><strong class="command"></strong></span></p>
8537                     </td>
8538 <td>
8539                       <p>
8540                         Dynamic updates failed.
8541                       </p>
8542                     </td>
8543 </tr>
8544 <tr>
8545 <td>
8546                       <p><span><strong class="command">UpdateBadPrereq</strong></span></p>
8547                     </td>
8548 <td>
8549                       <p><span><strong class="command"></strong></span></p>
8550                     </td>
8551 <td>
8552                       <p>
8553                         Dynamic updates rejected due to prerequisite failure.
8554                       </p>
8555                     </td>
8556 </tr>
8557 </tbody>
8558 </table></div>
8559 </div>
8560 <div class="sect3" lang="en">
8561 <div class="titlepage"><div><div><h4 class="title">
8562 <a name="id2596905"></a>Zone Maintenance Statistics Counters</h4></div></div></div>
8563 <div class="informaltable"><table border="1">
8564 <colgroup>
8565 <col>
8566 <col>
8567 </colgroup>
8568 <tbody>
8569 <tr>
8570 <td>
8571                       <p>
8572                         <span class="emphasis"><em>Symbol</em></span>
8573                       </p>
8574                     </td>
8575 <td>
8576                       <p>
8577                         <span class="emphasis"><em>Description</em></span>
8578                       </p>
8579                     </td>
8580 </tr>
8581 <tr>
8582 <td>
8583                       <p><span><strong class="command">NotifyOutv4</strong></span></p>
8584                     </td>
8585 <td>
8586                       <p>
8587                         IPv4 notifies sent.
8588                       </p>
8589                     </td>
8590 </tr>
8591 <tr>
8592 <td>
8593                       <p><span><strong class="command">NotifyOutv6</strong></span></p>
8594                     </td>
8595 <td>
8596                       <p>
8597                         IPv6 notifies sent.
8598                       </p>
8599                     </td>
8600 </tr>
8601 <tr>
8602 <td>
8603                       <p><span><strong class="command">NotifyInv4</strong></span></p>
8604                     </td>
8605 <td>
8606                       <p>
8607                         IPv4 notifies received.
8608                       </p>
8609                     </td>
8610 </tr>
8611 <tr>
8612 <td>
8613                       <p><span><strong class="command">NotifyInv6</strong></span></p>
8614                     </td>
8615 <td>
8616                       <p>
8617                         IPv6 notifies received.
8618                       </p>
8619                     </td>
8620 </tr>
8621 <tr>
8622 <td>
8623                       <p><span><strong class="command">NotifyRej</strong></span></p>
8624                     </td>
8625 <td>
8626                       <p>
8627                         Incoming notifies rejected.
8628                       </p>
8629                     </td>
8630 </tr>
8631 <tr>
8632 <td>
8633                       <p><span><strong class="command">SOAOutv4</strong></span></p>
8634                     </td>
8635 <td>
8636                       <p>
8637                         IPv4 SOA queries sent.
8638                       </p>
8639                     </td>
8640 </tr>
8641 <tr>
8642 <td>
8643                       <p><span><strong class="command">SOAOutv6</strong></span></p>
8644                     </td>
8645 <td>
8646                       <p>
8647                         IPv6 SOA queries sent.
8648                       </p>
8649                     </td>
8650 </tr>
8651 <tr>
8652 <td>
8653                       <p><span><strong class="command">AXFRReqv4</strong></span></p>
8654                     </td>
8655 <td>
8656                       <p>
8657                         IPv4 AXFR requested.
8658                       </p>
8659                     </td>
8660 </tr>
8661 <tr>
8662 <td>
8663                       <p><span><strong class="command">AXFRReqv6</strong></span></p>
8664                     </td>
8665 <td>
8666                       <p>
8667                         IPv6 AXFR requested.
8668                       </p>
8669                     </td>
8670 </tr>
8671 <tr>
8672 <td>
8673                       <p><span><strong class="command">IXFRReqv4</strong></span></p>
8674                     </td>
8675 <td>
8676                       <p>
8677                         IPv4 IXFR requested.
8678                       </p>
8679                     </td>
8680 </tr>
8681 <tr>
8682 <td>
8683                       <p><span><strong class="command">IXFRReqv6</strong></span></p>
8684                     </td>
8685 <td>
8686                       <p>
8687                         IPv6 IXFR requested.
8688                       </p>
8689                     </td>
8690 </tr>
8691 <tr>
8692 <td>
8693                       <p><span><strong class="command">XfrSuccess</strong></span></p>
8694                     </td>
8695 <td>
8696                       <p>
8697                         Zone transfer requests succeeded.
8698                       </p>
8699                     </td>
8700 </tr>
8701 <tr>
8702 <td>
8703                       <p><span><strong class="command">XfrFail</strong></span></p>
8704                     </td>
8705 <td>
8706                       <p>
8707                         Zone transfer requests failed.
8708                       </p>
8709                     </td>
8710 </tr>
8711 </tbody>
8712 </table></div>
8713 </div>
8714 <div class="sect3" lang="en">
8715 <div class="titlepage"><div><div><h4 class="title">
8716 <a name="id2597288"></a>Resolver Statistics Counters</h4></div></div></div>
8717 <div class="informaltable"><table border="1">
8718 <colgroup>
8719 <col>
8720 <col>
8721 <col>
8722 </colgroup>
8723 <tbody>
8724 <tr>
8725 <td>
8726                       <p>
8727                         <span class="emphasis"><em>Symbol</em></span>
8728                       </p>
8729                     </td>
8730 <td>
8731                       <p>
8732                         <span class="emphasis"><em>BIND8 Symbol</em></span>
8733                       </p>
8734                     </td>
8735 <td>
8736                       <p>
8737                         <span class="emphasis"><em>Description</em></span>
8738                       </p>
8739                     </td>
8740 </tr>
8741 <tr>
8742 <td>
8743                       <p><span><strong class="command">Queryv4</strong></span></p>
8744                     </td>
8745 <td>
8746                       <p><span><strong class="command">SFwdQ</strong></span></p>
8747                     </td>
8748 <td>
8749                       <p>
8750                         IPv4 queries sent.
8751                       </p>
8752                     </td>
8753 </tr>
8754 <tr>
8755 <td>
8756                       <p><span><strong class="command">Queryv6</strong></span></p>
8757                     </td>
8758 <td>
8759                       <p><span><strong class="command">SFwdQ</strong></span></p>
8760                     </td>
8761 <td>
8762                       <p>
8763                         IPv6 queries sent.
8764                       </p>
8765                     </td>
8766 </tr>
8767 <tr>
8768 <td>
8769                       <p><span><strong class="command">Responsev4</strong></span></p>
8770                     </td>
8771 <td>
8772                       <p><span><strong class="command">RR</strong></span></p>
8773                     </td>
8774 <td>
8775                       <p>
8776                         IPv4 responses received.
8777                       </p>
8778                     </td>
8779 </tr>
8780 <tr>
8781 <td>
8782                       <p><span><strong class="command">Responsev6</strong></span></p>
8783                     </td>
8784 <td>
8785                       <p><span><strong class="command">RR</strong></span></p>
8786                     </td>
8787 <td>
8788                       <p>
8789                         IPv6 responses received.
8790                       </p>
8791                     </td>
8792 </tr>
8793 <tr>
8794 <td>
8795                       <p><span><strong class="command">NXDOMAIN</strong></span></p>
8796                     </td>
8797 <td>
8798                       <p><span><strong class="command">RNXD</strong></span></p>
8799                     </td>
8800 <td>
8801                       <p>
8802                         NXDOMAIN received.
8803                       </p>
8804                     </td>
8805 </tr>
8806 <tr>
8807 <td>
8808                       <p><span><strong class="command">SERVFAIL</strong></span></p>
8809                     </td>
8810 <td>
8811                       <p><span><strong class="command">RFail</strong></span></p>
8812                     </td>
8813 <td>
8814                       <p>
8815                         SERVFAIL received.
8816                       </p>
8817                     </td>
8818 </tr>
8819 <tr>
8820 <td>
8821                       <p><span><strong class="command">FORMERR</strong></span></p>
8822                     </td>
8823 <td>
8824                       <p><span><strong class="command">RFErr</strong></span></p>
8825                     </td>
8826 <td>
8827                       <p>
8828                         FORMERR received.
8829                       </p>
8830                     </td>
8831 </tr>
8832 <tr>
8833 <td>
8834                       <p><span><strong class="command">OtherError</strong></span></p>
8835                     </td>
8836 <td>
8837                       <p><span><strong class="command">RErr</strong></span></p>
8838                     </td>
8839 <td>
8840                       <p>
8841                         Other errors received.
8842                       </p>
8843                     </td>
8844 </tr>
8845 <tr>
8846 <td>
8847                       <p><span><strong class="command">EDNS0Fail</strong></span></p>
8848                                                  </td>
8849 <td>
8850                       <p><span><strong class="command"></strong></span></p>
8851                     </td>
8852 <td>
8853                       <p>
8854                         EDNS(0) query failures.
8855                       </p>
8856                     </td>
8857 </tr>
8858 <tr>
8859 <td>
8860                       <p><span><strong class="command">Mismatch</strong></span></p>
8861                     </td>
8862 <td>
8863                       <p><span><strong class="command">RDupR</strong></span></p>
8864                     </td>
8865 <td>
8866                       <p>
8867                         Mismatch responses received.
8868                       </p>
8869                     </td>
8870 </tr>
8871 <tr>
8872 <td>
8873                       <p><span><strong class="command">Truncated</strong></span></p>
8874                     </td>
8875 <td>
8876                       <p><span><strong class="command"></strong></span></p>
8877                     </td>
8878 <td>
8879                       <p>
8880                         Truncated responses received.
8881                       </p>
8882                     </td>
8883 </tr>
8884 <tr>
8885 <td>
8886                       <p><span><strong class="command">Lame</strong></span></p>
8887                     </td>
8888 <td>
8889                       <p><span><strong class="command">RLame</strong></span></p>
8890                     </td>
8891 <td>
8892                       <p>
8893                         Lame delegations received.
8894                       </p>
8895                     </td>
8896 </tr>
8897 <tr>
8898 <td>
8899                       <p><span><strong class="command">Retry</strong></span></p>
8900                     </td>
8901 <td>
8902                       <p><span><strong class="command">SDupQ</strong></span></p>
8903                     </td>
8904 <td>
8905                       <p>
8906                         Query retries performed.
8907                       </p>
8908                     </td>
8909 </tr>
8910 <tr>
8911 <td>
8912                       <p><span><strong class="command">QueryAbort</strong></span></p>
8913                     </td>
8914 <td>
8915                       <p><span><strong class="command"></strong></span></p>
8916                     </td>
8917 <td>
8918                       <p>
8919                         Queries aborted due to quota control.
8920                       </p>
8921                     </td>
8922 </tr>
8923 <tr>
8924 <td>
8925                       <p><span><strong class="command">QuerySockFail</strong></span></p>
8926                     </td>
8927 <td>
8928                       <p><span><strong class="command"></strong></span></p>
8929                     </td>
8930 <td>
8931                       <p>
8932                         Failures in opening query sockets.
8933                         One common reason for such failures is a
8934                         failure of opening a new socket due to a
8935                         limitation on file descriptors.
8936                       </p>
8937                     </td>
8938 </tr>
8939 <tr>
8940 <td>
8941                       <p><span><strong class="command">QueryTimeout</strong></span></p>
8942                     </td>
8943 <td>
8944                       <p><span><strong class="command"></strong></span></p>
8945                     </td>
8946 <td>
8947                       <p>
8948                         Query timeouts.
8949                       </p>
8950                     </td>
8951 </tr>
8952 <tr>
8953 <td>
8954                       <p><span><strong class="command">GlueFetchv4</strong></span></p>
8955                     </td>
8956 <td>
8957                       <p><span><strong class="command">SSysQ</strong></span></p>
8958                     </td>
8959 <td>
8960                       <p>
8961                         IPv4 NS address fetches invoked.
8962                       </p>
8963                     </td>
8964 </tr>
8965 <tr>
8966 <td>
8967                       <p><span><strong class="command">GlueFetchv6</strong></span></p>
8968                     </td>
8969 <td>
8970                       <p><span><strong class="command">SSysQ</strong></span></p>
8971                     </td>
8972 <td>
8973                       <p>
8974                         IPv6 NS address fetches invoked.
8975                       </p>
8976                     </td>
8977 </tr>
8978 <tr>
8979 <td>
8980                       <p><span><strong class="command">GlueFetchv4Fail</strong></span></p>
8981                     </td>
8982 <td>
8983                       <p><span><strong class="command"></strong></span></p>
8984                     </td>
8985 <td>
8986                       <p>
8987                         IPv4 NS address fetch failed.
8988                       </p>
8989                     </td>
8990 </tr>
8991 <tr>
8992 <td>
8993                       <p><span><strong class="command">GlueFetchv6Fail</strong></span></p>
8994                     </td>
8995 <td>
8996                       <p><span><strong class="command"></strong></span></p>
8997                     </td>
8998 <td>
8999                       <p>
9000                         IPv6 NS address fetch failed.
9001                       </p>
9002                     </td>
9003 </tr>
9004 <tr>
9005 <td>
9006                       <p><span><strong class="command">ValAttempt</strong></span></p>
9007                     </td>
9008 <td>
9009                       <p><span><strong class="command"></strong></span></p>
9010                     </td>
9011 <td>
9012                       <p>
9013                         DNSSEC validation attempted.
9014                       </p>
9015                     </td>
9016 </tr>
9017 <tr>
9018 <td>
9019                       <p><span><strong class="command">ValOk</strong></span></p>
9020                     </td>
9021 <td>
9022                       <p><span><strong class="command"></strong></span></p>
9023                     </td>
9024 <td>
9025                       <p>
9026                         DNSSEC validation succeeded.
9027                       </p>
9028                     </td>
9029 </tr>
9030 <tr>
9031 <td>
9032                       <p><span><strong class="command">ValNegOk</strong></span></p>
9033                     </td>
9034 <td>
9035                       <p><span><strong class="command"></strong></span></p>
9036                     </td>
9037 <td>
9038                       <p>
9039                         DNSSEC validation on negative information succeeded.
9040                       </p>
9041                     </td>
9042 </tr>
9043 <tr>
9044 <td>
9045                       <p><span><strong class="command">ValFail</strong></span></p>
9046                     </td>
9047 <td>
9048                       <p><span><strong class="command"></strong></span></p>
9049                     </td>
9050 <td>
9051                       <p>
9052                         DNSSEC validation failed.
9053                       </p>
9054                     </td>
9055 </tr>
9056 <tr>
9057 <td>
9058                       <p><span><strong class="command">QryRTTnn</strong></span></p>
9059                     </td>
9060 <td>
9061                       <p><span><strong class="command"></strong></span></p>
9062                     </td>
9063 <td>
9064                       <p>
9065                         Frequency table on round trip times (RTTs) of
9066                         queries.
9067                         Each <span><strong class="command">nn</strong></span> specifies the corresponding
9068                         frequency.
9069                         In the sequence of
9070                         <span><strong class="command">nn_1</strong></span>,
9071                         <span><strong class="command">nn_2</strong></span>,
9072                         ...,
9073                         <span><strong class="command">nn_m</strong></span>,
9074                         the value of <span><strong class="command">nn_i</strong></span> is the
9075                         number of queries whose RTTs are between
9076                         <span><strong class="command">nn_(i-1)</strong></span> (inclusive) and
9077                         <span><strong class="command">nn_i</strong></span> (exclusive) milliseconds.
9078                         For the sake of convenience we define
9079                         <span><strong class="command">nn_0</strong></span> to be 0.
9080                         The last entry should be represented as
9081                         <span><strong class="command">nn_m+</strong></span>, which means the
9082                         number of queries whose RTTs are equal to or over
9083                         <span><strong class="command">nn_m</strong></span> milliseconds.
9084                       </p>
9085                     </td>
9086 </tr>
9087 </tbody>
9088 </table></div>
9089 </div>
9090 <div class="sect3" lang="en">
9091 <div class="titlepage"><div><div><h4 class="title">
9092 <a name="id2598307"></a>Socket I/O Statistics Counters</h4></div></div></div>
9093 <p>
9094               Socket I/O statistics counters are defined per socket
9095               types, which are
9096               <span><strong class="command">UDP4</strong></span> (UDP/IPv4),
9097               <span><strong class="command">UDP6</strong></span> (UDP/IPv6),
9098               <span><strong class="command">TCP4</strong></span> (TCP/IPv4),
9099               <span><strong class="command">TCP6</strong></span> (TCP/IPv6),
9100               <span><strong class="command">Unix</strong></span> (Unix Domain), and
9101               <span><strong class="command">FDwatch</strong></span> (sockets opened outside the
9102               socket module).
9103               In the following table <span><strong class="command">&lt;TYPE&gt;</strong></span>
9104               represents a socket type.
9105               Not all counters are available for all socket types;
9106               exceptions are noted in the description field.
9107             </p>
9108 <div class="informaltable"><table border="1">
9109 <colgroup>
9110 <col>
9111 <col>
9112 </colgroup>
9113 <tbody>
9114 <tr>
9115 <td>
9116                       <p>
9117                         <span class="emphasis"><em>Symbol</em></span>
9118                       </p>
9119                     </td>
9120 <td>
9121                       <p>
9122                         <span class="emphasis"><em>Description</em></span>
9123                       </p>
9124                     </td>
9125 </tr>
9126 <tr>
9127 <td>
9128                       <p><span><strong class="command">&lt;TYPE&gt;Open</strong></span></p>
9129                     </td>
9130 <td>
9131                       <p>
9132                         Sockets opened successfully.
9133                         This counter is not applicable to the
9134                         <span><strong class="command">FDwatch</strong></span> type.
9135                       </p>
9136                     </td>
9137 </tr>
9138 <tr>
9139 <td>
9140                       <p><span><strong class="command">&lt;TYPE&gt;OpenFail</strong></span></p>
9141                     </td>
9142 <td>
9143                       <p>
9144                         Failures of opening sockets.
9145                         This counter is not applicable to the
9146                         <span><strong class="command">FDwatch</strong></span> type.
9147                       </p>
9148                     </td>
9149 </tr>
9150 <tr>
9151 <td>
9152                       <p><span><strong class="command">&lt;TYPE&gt;Close</strong></span></p>
9153                     </td>
9154 <td>
9155                       <p>
9156                         Sockets closed.
9157                       </p>
9158                     </td>
9159 </tr>
9160 <tr>
9161 <td>
9162                       <p><span><strong class="command">&lt;TYPE&gt;BindFail</strong></span></p>
9163                     </td>
9164 <td>
9165                       <p>
9166                         Failures of binding sockets.
9167                       </p>
9168                     </td>
9169 </tr>
9170 <tr>
9171 <td>
9172                       <p><span><strong class="command">&lt;TYPE&gt;ConnFail</strong></span></p>
9173                     </td>
9174 <td>
9175                       <p>
9176                         Failures of connecting sockets.
9177                       </p>
9178                     </td>
9179 </tr>
9180 <tr>
9181 <td>
9182                       <p><span><strong class="command">&lt;TYPE&gt;Conn</strong></span></p>
9183                     </td>
9184 <td>
9185                       <p>
9186                         Connections established successfully.
9187                       </p>
9188                     </td>
9189 </tr>
9190 <tr>
9191 <td>
9192                       <p><span><strong class="command">&lt;TYPE&gt;AcceptFail</strong></span></p>
9193                     </td>
9194 <td>
9195                       <p>
9196                         Failures of accepting incoming connection requests.
9197                         This counter is not applicable to the
9198                         <span><strong class="command">UDP</strong></span> and
9199                         <span><strong class="command">FDwatch</strong></span> types.
9200                       </p>
9201                     </td>
9202 </tr>
9203 <tr>
9204 <td>
9205                       <p><span><strong class="command">&lt;TYPE&gt;Accept</strong></span></p>
9206                     </td>
9207 <td>
9208                       <p>
9209                         Incoming connections successfully accepted.
9210                         This counter is not applicable to the
9211                         <span><strong class="command">UDP</strong></span> and
9212                         <span><strong class="command">FDwatch</strong></span> types.
9213                       </p>
9214                     </td>
9215 </tr>
9216 <tr>
9217 <td>
9218                       <p><span><strong class="command">&lt;TYPE&gt;SendErr</strong></span></p>
9219                     </td>
9220 <td>
9221                       <p>
9222                         Errors in socket send operations.
9223                         This counter corresponds
9224                         to <span><strong class="command">SErr</strong></span> counter of
9225                         <span><strong class="command">BIND</strong></span> 8.
9226                       </p>
9227                     </td>
9228 </tr>
9229 <tr>
9230 <td>
9231                       <p><span><strong class="command">&lt;TYPE&gt;RecvErr</strong></span></p>
9232                     </td>
9233 <td>
9234                       <p>
9235                         Errors in socket receive operations.
9236                         This includes errors of send operations on a
9237                         connected UDP socket notified by an ICMP error
9238                         message.
9239                       </p>
9240                     </td>
9241 </tr>
9242 </tbody>
9243 </table></div>
9244 </div>
9245 <div class="sect3" lang="en">
9246 <div class="titlepage"><div><div><h4 class="title">
9247 <a name="id2598817"></a>Compatibility with <span class="emphasis"><em>BIND</em></span> 8 Counters</h4></div></div></div>
9248 <p>
9249               Most statistics counters that were available
9250               in <span><strong class="command">BIND</strong></span> 8 are also supported in
9251               <span><strong class="command">BIND</strong></span> 9 as shown in the above tables.
9252               Here are notes about other counters that do not appear
9253               in these tables.
9254             </p>
9255 <div class="variablelist"><dl>
9256 <dt><span class="term"><span><strong class="command">RFwdR,SFwdR</strong></span></span></dt>
9257 <dd><p>
9258                     These counters are not supported
9259                     because <span><strong class="command">BIND</strong></span> 9 does not adopt
9260                     the notion of <span class="emphasis"><em>forwarding</em></span>
9261                     as <span><strong class="command">BIND</strong></span> 8 did.
9262                   </p></dd>
9263 <dt><span class="term"><span><strong class="command">RAXFR</strong></span></span></dt>
9264 <dd><p>
9265                     This counter is accessible in the Incoming Queries section.
9266                   </p></dd>
9267 <dt><span class="term"><span><strong class="command">RIQ</strong></span></span></dt>
9268 <dd><p>
9269                     This counter is accessible in the Incoming Requests section.
9270                   </p></dd>
9271 <dt><span class="term"><span><strong class="command">ROpts</strong></span></span></dt>
9272 <dd><p>
9273                     This counter is not supported
9274                     because <span><strong class="command">BIND</strong></span> 9 does not care
9275                     about IP options in the first place.
9276                   </p></dd>
9277 </dl></div>
9278 </div>
9279 </div>
9280 </div>
9281 </div>
9282 <div class="navfooter">
9283 <hr>
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9285 <tr>
9286 <td width="40%" align="left">
9287 <a accesskey="p" href="Bv9ARM.ch05.html">Prev</a> </td>
9288 <td width="20%" align="center"> </td>
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9290 </td>
9291 </tr>
9292 <tr>
9293 <td width="40%" align="left" valign="top">Chapter 5. The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver </td>
9294 <td width="20%" align="center"><a accesskey="h" href="Bv9ARM.html">Home</a></td>
9295 <td width="40%" align="right" valign="top"> Chapter 7. <acronym class="acronym">BIND</acronym> 9 Security Considerations</td>
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