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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#id2573606">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#id2574305"><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#id2574494"><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#id2574923"><span><strong class="command">include</strong></span> Statement Grammar</a></span></dt>
  62 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574940"><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#id2574964"><span><strong class="command">key</strong></span> Statement Grammar</a></span></dt>
  65 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2574987"><span><strong class="command">key</strong></span> Statement Definition and Usage</a></span></dt>
  66 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575078"><span><strong class="command">logging</strong></span> Statement Grammar</a></span></dt>
  67 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2575204"><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#id2577401"><span><strong class="command">lwres</strong></span> Statement Grammar</a></span></dt>
  70 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577475"><span><strong class="command">lwres</strong></span> Statement Definition and Usage</a></span></dt>
  71 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577539"><span><strong class="command">masters</strong></span> Statement Grammar</a></span></dt>
  72 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2577582"><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#id2577597"><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#id2586907"><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#id2587062"><span><strong class="command">trusted-keys</strong></span> Statement Grammar</a></span></dt>
  84 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2587113"><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#id2587195"><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#id2588600"><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#id2591216">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#id2593378">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#id2593993">Inverse Mapping in IPv4</a></span></dt>
  98 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2594188">Other Zone File Directives</a></span></dt>
  99 <dt><span class="sect2"><a href="Bv9ARM.ch06.html#id2594461"><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="id2573372"></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="id2573468"></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="id2573606"></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="id2573621"></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="id2573651"></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="id2574305"></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="id2574494"></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="id2574923"></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="id2574940"></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="id2574964"></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="id2574987"></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="id2575078"></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="id2575204"></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="id2575256"></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 those servers during resolution.
1670                     </p>
1671                   </td>
1672 </tr>
1673 <tr>
1674 <td>
1675                     <p><span><strong class="command">delegation-only</strong></span></p>
1676                   </td>
1677 <td>
1678                     <p>
1679                       Delegation only.  Logs queries that have been
1680                       forced to NXDOMAIN as the result of a
1681                       delegation-only zone or a
1682                       <span><strong class="command">delegation-only</strong></span> in a hint
1683                       or stub zone declaration.
1684                     </p>
1685                   </td>
1686 </tr>
1687 <tr>
1688 <td>
1689                     <p><span><strong class="command">edns-disabled</strong></span></p>
1690                   </td>
1691 <td>
1692                     <p>
1693                       Log queries that have been forced to use plain
1694                       DNS due to timeouts.  This is often due to
1695                       the remote servers not being RFC 1034 compliant
1696                       (not always returning FORMERR or similar to
1697                       EDNS queries and other extensions to the DNS
1698                       when they are not understood).  In other words, this is
1699                       targeted at servers that fail to respond to
1700                       DNS queries that they don't understand.
1701                     </p>
1702                     <p>
1703                       Note: the log message can also be due to
1704                       packet loss.  Before reporting servers for
1705                       non-RFC 1034 compliance they should be re-tested
1706                       to determine the nature of the non-compliance.
1707                       This testing should prevent or reduce the
1708                       number of false-positive reports.
1709                     </p>
1710                     <p>
1711                       Note: eventually <span><strong class="command">named</strong></span> will have to stop
1712                       treating such timeouts as due to RFC 1034 non
1713                       compliance and start treating it as plain
1714                       packet loss.  Falsely classifying packet
1715                       loss as due to RFC 1034 non compliance impacts
1716                       on DNSSEC validation which requires EDNS for
1717                       the DNSSEC records to be returned.
1718                     </p>
1719                   </td>
1720 </tr>
1721 </tbody>
1722 </table></div>
1723 </div>
1724 <div class="sect3" lang="en">
1725 <div class="titlepage"><div><div><h4 class="title">
1726 <a name="id2576820"></a>The <span><strong class="command">query-errors</strong></span> Category</h4></div></div></div>
1727 <p>
1728             The <span><strong class="command">query-errors</strong></span> category is
1729             specifically intended for debugging purposes: To identify
1730             why and how specific queries result in responses which
1731             indicate an error.
1732             Messages of this category are therefore only logged
1733             with <span><strong class="command">debug</strong></span> levels.
1734           </p>
1735 <p>
1736             At the debug levels of 1 or higher, each response with the
1737             rcode of SERVFAIL is logged as follows:
1738           </p>
1739 <p>
1740             <code class="computeroutput">client 127.0.0.1#61502: query failed (SERVFAIL) for www.example.com/IN/AAAA at query.c:3880</code>
1741           </p>
1742 <p>
1743             This means an error resulting in SERVFAIL was
1744             detected at line 3880 of source file
1745             <code class="filename">query.c</code>.
1746             Log messages of this level will particularly
1747             help identify the cause of SERVFAIL for an
1748             authoritative server.
1749           </p>
1750 <p>
1751             At the debug levels of 2 or higher, detailed context
1752             information of recursive resolutions that resulted in
1753             SERVFAIL is logged.
1754             The log message will look like as follows:
1755           </p>
1756 <p>
1757             <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>
1758           </p>
1759 <p>
1760             The first part before the colon shows that a recursive
1761             resolution for AAAA records of www.example.com completed
1762             in 30.000183 seconds and the final result that led to the
1763             SERVFAIL was determined at line 2970 of source file
1764             <code class="filename">resolver.c</code>.
1765           </p>
1766 <p>
1767             The following part shows the detected final result and the
1768             latest result of DNSSEC validation.
1769             The latter is always success when no validation attempt
1770             is made.
1771             In this example, this query resulted in SERVFAIL probably
1772             because all name servers are down or unreachable, leading
1773             to a timeout in 30 seconds.
1774             DNSSEC validation was probably not attempted.
1775           </p>
1776 <p>
1777             The last part enclosed in square brackets shows statistics
1778             information collected for this particular resolution
1779             attempt.
1780             The <code class="varname">domain</code> field shows the deepest zone
1781             that the resolver reached;
1782             it is the zone where the error was finally detected.
1783             The meaning of the other fields is summarized in the
1784             following table.
1785           </p>
1786 <div class="informaltable"><table border="1">
1787 <colgroup>
1788 <col>
1789 <col>
1790 </colgroup>
1791 <tbody>
1792 <tr>
1793 <td>
1794                     <p><code class="varname">referral</code></p>
1795                   </td>
1796 <td>
1797                     <p>
1798                       The number of referrals the resolver received
1799                       throughout the resolution process.
1800                       In the above example this is 2, which are most
1801                       likely com and example.com.
1802                     </p>
1803                   </td>
1804 </tr>
1805 <tr>
1806 <td>
1807                     <p><code class="varname">restart</code></p>
1808                   </td>
1809 <td>
1810                     <p>
1811                       The number of cycles that the resolver tried
1812                       remote servers at the <code class="varname">domain</code>
1813                       zone.
1814                       In each cycle the resolver sends one query
1815                       (possibly resending it, depending on the response)
1816                       to each known name server of
1817                       the <code class="varname">domain</code> zone.
1818                     </p>
1819                   </td>
1820 </tr>
1821 <tr>
1822 <td>
1823                     <p><code class="varname">qrysent</code></p>
1824                   </td>
1825 <td>
1826                     <p>
1827                       The number of queries the resolver sent at the
1828                       <code class="varname">domain</code> zone.
1829                     </p>
1830                   </td>
1831 </tr>
1832 <tr>
1833 <td>
1834                     <p><code class="varname">timeout</code></p>
1835                   </td>
1836 <td>
1837                     <p>
1838                       The number of timeouts since the resolver
1839                       received the last response.
1840                     </p>
1841                   </td>
1842 </tr>
1843 <tr>
1844 <td>
1845                     <p><code class="varname">lame</code></p>
1846                   </td>
1847 <td>
1848                     <p>
1849                       The number of lame servers the resolver detected
1850                       at the <code class="varname">domain</code> zone.
1851                       A server is detected to be lame either by an
1852                       invalid response or as a result of lookup in
1853                       BIND9's address database (ADB), where lame
1854                       servers are cached.
1855                     </p>
1856                   </td>
1857 </tr>
1858 <tr>
1859 <td>
1860                     <p><code class="varname">neterr</code></p>
1861                   </td>
1862 <td>
1863                     <p>
1864                       The number of erroneous results that the
1865                       resolver encountered in sending queries
1866                       at the <code class="varname">domain</code> zone.
1867                       One common case is the remote server is
1868                       unreachable and the resolver receives an ICMP
1869                       unreachable error message.
1870                     </p>
1871                   </td>
1872 </tr>
1873 <tr>
1874 <td>
1875                     <p><code class="varname">badresp</code></p>
1876                   </td>
1877 <td>
1878                     <p>
1879                       The number of unexpected responses (other than
1880                       <code class="varname">lame</code>) to queries sent by the
1881                       resolver at the <code class="varname">domain</code> zone.
1882                     </p>
1883                   </td>
1884 </tr>
1885 <tr>
1886 <td>
1887                     <p><code class="varname">adberr</code></p>
1888                   </td>
1889 <td>
1890                     <p>
1891                       Failures in finding remote server addresses
1892                       of the <code class="varname">domain</code> zone in the ADB.
1893                       One common case of this is that the remote
1894                       server's name does not have any address records.
1895                     </p>
1896                   </td>
1897 </tr>
1898 <tr>
1899 <td>
1900                     <p><code class="varname">findfail</code></p>
1901                   </td>
1902 <td>
1903                     <p>
1904                       Failures of resolving remote server addresses.
1905                       This is a total number of failures throughout
1906                       the resolution process.
1907                     </p>
1908                   </td>
1909 </tr>
1910 <tr>
1911 <td>
1912                     <p><code class="varname">valfail</code></p>
1913                   </td>
1914 <td>
1915                     <p>
1916                       Failures of DNSSEC validation.
1917                       Validation failures are counted throughout
1918                       the resolution process (not limited to
1919                       the <code class="varname">domain</code> zone), but should
1920                       only happen in <code class="varname">domain</code>.
1921                     </p>
1922                   </td>
1923 </tr>
1924 </tbody>
1925 </table></div>
1926 <p>
1927             At the debug levels of 3 or higher, the same messages
1928             as those at the debug 1 level are logged for other errors
1929             than SERVFAIL.
1930             Note that negative responses such as NXDOMAIN are not
1931             regarded as errors here.
1932           </p>
1933 <p>
1934             At the debug levels of 4 or higher, the same messages
1935             as those at the debug 2 level are logged for other errors
1936             than SERVFAIL.
1937             Unlike the above case of level 3, messages are logged for
1938             negative responses.
1939             This is because any unexpected results can be difficult to
1940             debug in the recursion case.
1941           </p>
1942 </div>
1943 </div>
1944 <div class="sect2" lang="en">
1945 <div class="titlepage"><div><div><h3 class="title">
1946 <a name="id2577401"></a><span><strong class="command">lwres</strong></span> Statement Grammar</h3></div></div></div>
1947 <p>
1948            This is the grammar of the <span><strong class="command">lwres</strong></span>
1949           statement in the <code class="filename">named.conf</code> file:
1950         </p>
1951 <pre class="programlisting"><span><strong class="command">lwres</strong></span> {
1952     [<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>]
1953     [<span class="optional"> view <em class="replaceable"><code>view_name</code></em>; </span>]
1954     [<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>]
1955     [<span class="optional"> ndots <em class="replaceable"><code>number</code></em>; </span>]
1956 };
1957 </pre>
1958 </div>
1959 <div class="sect2" lang="en">
1960 <div class="titlepage"><div><div><h3 class="title">
1961 <a name="id2577475"></a><span><strong class="command">lwres</strong></span> Statement Definition and Usage</h3></div></div></div>
1962 <p>
1963           The <span><strong class="command">lwres</strong></span> statement configures the
1964           name
1965           server to also act as a lightweight resolver server. (See
1966           <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
1967           <span><strong class="command">lwres</strong></span> statements configuring
1968           lightweight resolver servers with different properties.
1969         </p>
1970 <p>
1971           The <span><strong class="command">listen-on</strong></span> statement specifies a
1972           list of
1973           addresses (and ports) that this instance of a lightweight resolver
1974           daemon
1975           should accept requests on.  If no port is specified, port 921 is
1976           used.
1977           If this statement is omitted, requests will be accepted on
1978           127.0.0.1,
1979           port 921.
1980         </p>
1981 <p>
1982           The <span><strong class="command">view</strong></span> statement binds this
1983           instance of a
1984           lightweight resolver daemon to a view in the DNS namespace, so that
1985           the
1986           response will be constructed in the same manner as a normal DNS
1987           query
1988           matching this view.  If this statement is omitted, the default view
1989           is
1990           used, and if there is no default view, an error is triggered.
1991         </p>
1992 <p>
1993           The <span><strong class="command">search</strong></span> statement is equivalent to
1994           the
1995           <span><strong class="command">search</strong></span> statement in
1996           <code class="filename">/etc/resolv.conf</code>.  It provides a
1997           list of domains
1998           which are appended to relative names in queries.
1999         </p>
2000 <p>
2001           The <span><strong class="command">ndots</strong></span> statement is equivalent to
2002           the
2003           <span><strong class="command">ndots</strong></span> statement in
2004           <code class="filename">/etc/resolv.conf</code>.  It indicates the
2005           minimum
2006           number of dots in a relative domain name that should result in an
2007           exact match lookup before search path elements are appended.
2008         </p>
2009 </div>
2010 <div class="sect2" lang="en">
2011 <div class="titlepage"><div><div><h3 class="title">
2012 <a name="id2577539"></a><span><strong class="command">masters</strong></span> Statement Grammar</h3></div></div></div>
2013 <pre class="programlisting">
2014 <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>] };
2015 </pre>
2016 </div>
2017 <div class="sect2" lang="en">
2018 <div class="titlepage"><div><div><h3 class="title">
2019 <a name="id2577582"></a><span><strong class="command">masters</strong></span> Statement Definition and
2020           Usage</h3></div></div></div>
2021 <p><span><strong class="command">masters</strong></span>
2022           lists allow for a common set of masters to be easily used by
2023           multiple stub and slave zones.
2024         </p>
2025 </div>
2026 <div class="sect2" lang="en">
2027 <div class="titlepage"><div><div><h3 class="title">
2028 <a name="id2577597"></a><span><strong class="command">options</strong></span> Statement Grammar</h3></div></div></div>
2029 <p>
2030           This is the grammar of the <span><strong class="command">options</strong></span>
2031           statement in the <code class="filename">named.conf</code> file:
2032         </p>
2033 <pre class="programlisting"><span><strong class="command">options</strong></span> {
2034     [<span class="optional"> version <em class="replaceable"><code>version_string</code></em>; </span>]
2035     [<span class="optional"> hostname <em class="replaceable"><code>hostname_string</code></em>; </span>]
2036     [<span class="optional"> server-id <em class="replaceable"><code>server_id_string</code></em>; </span>]
2037     [<span class="optional"> directory <em class="replaceable"><code>path_name</code></em>; </span>]
2038     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
2039     [<span class="optional"> named-xfer <em class="replaceable"><code>path_name</code></em>; </span>]
2040     [<span class="optional"> tkey-gssapi-credential <em class="replaceable"><code>principal</code></em>; </span>]
2041     [<span class="optional"> tkey-domain <em class="replaceable"><code>domainname</code></em>; </span>]
2042     [<span class="optional"> tkey-dhkey <em class="replaceable"><code>key_name</code></em> <em class="replaceable"><code>key_tag</code></em>; </span>]
2043     [<span class="optional"> cache-file <em class="replaceable"><code>path_name</code></em>; </span>]
2044     [<span class="optional"> dump-file <em class="replaceable"><code>path_name</code></em>; </span>]
2045     [<span class="optional"> memstatistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2046     [<span class="optional"> memstatistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2047     [<span class="optional"> pid-file <em class="replaceable"><code>path_name</code></em>; </span>]
2048     [<span class="optional"> recursing-file <em class="replaceable"><code>path_name</code></em>; </span>]
2049     [<span class="optional"> statistics-file <em class="replaceable"><code>path_name</code></em>; </span>]
2050     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2051     [<span class="optional"> auth-nxdomain <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2052     [<span class="optional"> deallocate-on-exit <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2053     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em>; </span>]
2054     [<span class="optional"> fake-iquery <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2055     [<span class="optional"> fetch-glue <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2056     [<span class="optional"> flush-zones-on-shutdown <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2057     [<span class="optional"> has-old-clients <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2058     [<span class="optional"> host-statistics <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2059     [<span class="optional"> host-statistics-max <em class="replaceable"><code>number</code></em>; </span>]
2060     [<span class="optional"> minimal-responses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2061     [<span class="optional"> multiple-cnames <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2062     [<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>]
2063     [<span class="optional"> recursion <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2064     [<span class="optional"> rfc2308-type1 <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2065     [<span class="optional"> use-id-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2066     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2067     [<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>]
2068     [<span class="optional"> dnssec-enable <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2069     [<span class="optional"> dnssec-validation <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2070     [<span class="optional"> dnssec-lookaside <em class="replaceable"><code>domain</code></em> trust-anchor <em class="replaceable"><code>domain</code></em>; </span>]
2071     [<span class="optional"> dnssec-must-be-secure <em class="replaceable"><code>domain yes_or_no</code></em>; </span>]
2072     [<span class="optional"> dnssec-accept-expired <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2073     [<span class="optional"> forward ( <em class="replaceable"><code>only</code></em> | <em class="replaceable"><code>first</code></em> ); </span>]
2074     [<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>]
2075     [<span class="optional"> dual-stack-servers [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] {
2076         ( <em class="replaceable"><code>domain_name</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] |
2077           <em class="replaceable"><code>ip_addr</code></em> [<span class="optional">port <em class="replaceable"><code>ip_port</code></em></span>] ) ;
2078         ... }; </span>]
2079     [<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> )
2080         ( <em class="replaceable"><code>warn</code></em> | <em class="replaceable"><code>fail</code></em> | <em class="replaceable"><code>ignore</code></em> ); </span>]
2081     [<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>]
2082     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2083     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2084     [<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>]
2085     [<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>]
2086     [<span class="optional"> check-sibling <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2087     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2088     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2089     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2090     [<span class="optional"> allow-query-cache { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2091     [<span class="optional"> allow-query-cache-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2092     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2093     [<span class="optional"> allow-recursion { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2094     [<span class="optional"> allow-recursion-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2095     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2096     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2097     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2098     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2099     [<span class="optional"> allow-v6-synthesis { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2100     [<span class="optional"> blackhole { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
2101     [<span class="optional"> use-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2102     [<span class="optional"> avoid-v4-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2103     [<span class="optional"> use-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2104     [<span class="optional"> avoid-v6-udp-ports { <em class="replaceable"><code>port_list</code></em> }; </span>]
2105     [<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>]
2106     [<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>]
2107     [<span class="optional"> query-source ( ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2108         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
2109         [<span class="optional"> address ( <em class="replaceable"><code>ip4_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2110         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
2111     [<span class="optional"> query-source-v6 ( ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> )
2112         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] |
2113         [<span class="optional"> address ( <em class="replaceable"><code>ip6_addr</code></em> | <em class="replaceable"><code>*</code></em> ) </span>]
2114         [<span class="optional"> port ( <em class="replaceable"><code>ip_port</code></em> | <em class="replaceable"><code>*</code></em> ) </span>] ) ; </span>]
2115     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2116     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
2117     [<span class="optional"> queryport-pool-updateinterval <em class="replaceable"><code>number</code></em>; </span>]
2118     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em>; </span>]
2119     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em>; </span>]
2120     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em>; </span>]
2121     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em>; </span>]
2122     [<span class="optional"> tcp-clients <em class="replaceable"><code>number</code></em>; </span>]
2123     [<span class="optional"> reserved-sockets <em class="replaceable"><code>number</code></em>; </span>]
2124     [<span class="optional"> recursive-clients <em class="replaceable"><code>number</code></em>; </span>]
2125     [<span class="optional"> serial-query-rate <em class="replaceable"><code>number</code></em>; </span>]
2126     [<span class="optional"> serial-queries <em class="replaceable"><code>number</code></em>; </span>]
2127     [<span class="optional"> tcp-listen-queue <em class="replaceable"><code>number</code></em>; </span>]
2128     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em>; </span>]
2129     [<span class="optional"> transfers-in  <em class="replaceable"><code>number</code></em>; </span>]
2130     [<span class="optional"> transfers-out <em class="replaceable"><code>number</code></em>; </span>]
2131     [<span class="optional"> transfers-per-ns <em class="replaceable"><code>number</code></em>; </span>]
2132     [<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>]
2133     [<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>]
2134     [<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>]
2135     [<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>]
2136     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2137     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
2138     [<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>]
2139     [<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>]
2140     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2141     [<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>]
2142     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em>; </span>]
2143     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
2144     [<span class="optional"> coresize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2145     [<span class="optional"> datasize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2146     [<span class="optional"> files <em class="replaceable"><code>size_spec</code></em> ; </span>]
2147     [<span class="optional"> stacksize <em class="replaceable"><code>size_spec</code></em> ; </span>]
2148     [<span class="optional"> cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2149     [<span class="optional"> heartbeat-interval <em class="replaceable"><code>number</code></em>; </span>]
2150     [<span class="optional"> interface-interval <em class="replaceable"><code>number</code></em>; </span>]
2151     [<span class="optional"> statistics-interval <em class="replaceable"><code>number</code></em>; </span>]
2152     [<span class="optional"> topology { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2153     [<span class="optional"> sortlist { <em class="replaceable"><code>address_match_list</code></em> }</span>];
2154     [<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>] };
2155     [<span class="optional"> lame-ttl <em class="replaceable"><code>number</code></em>; </span>]
2156     [<span class="optional"> max-ncache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2157     [<span class="optional"> max-cache-ttl <em class="replaceable"><code>number</code></em>; </span>]
2158     [<span class="optional"> sig-validity-interval <em class="replaceable"><code>number</code></em> [<span class="optional"><em class="replaceable"><code>number</code></em></span>] ; </span>]
2159     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
2160     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
2161     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
2162     [<span class="optional"> min-roots <em class="replaceable"><code>number</code></em>; </span>]
2163     [<span class="optional"> use-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2164     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2165     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2166     [<span class="optional"> treat-cr-as-space <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2167     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2168     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
2169     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2170     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
2171     [<span class="optional"> port <em class="replaceable"><code>ip_port</code></em>; </span>]
2172     [<span class="optional"> additional-from-auth <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2173     [<span class="optional"> additional-from-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2174     [<span class="optional"> random-device <em class="replaceable"><code>path_name</code></em> ; </span>]
2175     [<span class="optional"> max-cache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2176     [<span class="optional"> match-mapped-addresses <em class="replaceable"><code>yes_or_no</code></em>; </span>]
2177     [<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>]
2178     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2179     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em>; </span>]
2180     [<span class="optional"> root-delegation-only [<span class="optional"> exclude { <em class="replaceable"><code>namelist</code></em> } </span>] ; </span>]
2181     [<span class="optional"> querylog <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2182     [<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>]
2183     [<span class="optional"> acache-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2184     [<span class="optional"> acache-cleaning-interval <em class="replaceable"><code>number</code></em>; </span>]
2185     [<span class="optional"> max-acache-size <em class="replaceable"><code>size_spec</code></em> ; </span>]
2186     [<span class="optional"> clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2187     [<span class="optional"> max-clients-per-query <em class="replaceable"><code>number</code></em> ; </span>]
2188     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
2189     [<span class="optional"> empty-server <em class="replaceable"><code>name</code></em> ; </span>]
2190     [<span class="optional"> empty-contact <em class="replaceable"><code>name</code></em> ; </span>]
2191     [<span class="optional"> empty-zones-enable <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2192     [<span class="optional"> disable-empty-zone <em class="replaceable"><code>zone_name</code></em> ; </span>]
2193     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2194     [<span class="optional"> zero-no-soa-ttl-cache <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
2195 };
2196 </pre>
2197 </div>
2198 <div class="sect2" lang="en">
2199 <div class="titlepage"><div><div><h3 class="title">
2200 <a name="options"></a><span><strong class="command">options</strong></span> Statement Definition and
2201           Usage</h3></div></div></div>
2202 <p>
2203           The <span><strong class="command">options</strong></span> statement sets up global
2204           options
2205           to be used by <acronym class="acronym">BIND</acronym>. This statement
2206           may appear only
2207           once in a configuration file. If there is no <span><strong class="command">options</strong></span>
2208           statement, an options block with each option set to its default will
2209           be used.
2210         </p>
2211 <div class="variablelist"><dl>
2212 <dt><span class="term"><span><strong class="command">directory</strong></span></span></dt>
2213 <dd><p>
2214                 The working directory of the server.
2215                 Any non-absolute pathnames in the configuration file will be
2216                 taken
2217                 as relative to this directory. The default location for most
2218                 server
2219                 output files (e.g. <code class="filename">named.run</code>)
2220                 is this directory.
2221                 If a directory is not specified, the working directory
2222                 defaults to `<code class="filename">.</code>', the directory from
2223                 which the server
2224                 was started. The directory specified should be an absolute
2225                 path.
2226               </p></dd>
2227 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
2228 <dd><p>
2229                 When performing dynamic update of secure zones, the
2230                 directory where the public and private DNSSEC key files
2231                 should be found, if different than the current working
2232                 directory.  The directory specified must be an absolute
2233                 path.  (Note that this option has no effect on the paths
2234                 for files containing non-DNSSEC keys such as the
2235                 <code class="filename">rndc.key</code>.
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>
2994 <p>
2995                   If <strong class="userinput"><code>yes</code></strong>, then an
2996                   IPv4-mapped IPv6 address will match any address match
2997                   list entries that match the corresponding IPv4 address.
2998                 </p>
2999 <p>
3000                   This option was introduced to work around a kernel quirk
3001                   in some operating systems that causes IPv4 TCP
3002                   connections, such as zone transfers, to be accepted on an
3003                   IPv6 socket using mapped addresses.  This caused address
3004                   match lists designed for IPv4 to fail to match.  However,
3005                   <span><strong class="command">named</strong></span> now solves this problem
3006                   internally.  The use of this option is discouraged.
3007                 </p>
3008 </dd>
3009 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
3010 <dd>
3011 <p>
3012                   When <strong class="userinput"><code>yes</code></strong> and the server loads a new version of a master
3013                   zone from its zone file or receives a new version of a slave
3014                   file by a non-incremental zone transfer, it will compare
3015                   the new version to the previous one and calculate a set
3016                   of differences.  The differences are then logged in the
3017                   zone's journal file such that the changes can be transmitted
3018                   to downstream slaves as an incremental zone transfer.
3019                 </p>
3020 <p>
3021                   By allowing incremental zone transfers to be used for
3022                   non-dynamic zones, this option saves bandwidth at the
3023                   expense of increased CPU and memory consumption at the
3024                   master.
3025                   In particular, if the new version of a zone is completely
3026                   different from the previous one, the set of differences
3027                   will be of a size comparable to the combined size of the
3028                   old and new zone version, and the server will need to
3029                   temporarily allocate memory to hold this complete
3030                   difference set.
3031                 </p>
3032 <p><span><strong class="command">ixfr-from-differences</strong></span>
3033                   also accepts <span><strong class="command">master</strong></span> and
3034                   <span><strong class="command">slave</strong></span> at the view and options
3035                   levels which causes
3036                   <span><strong class="command">ixfr-from-differences</strong></span> to be enabled for
3037                   all <span><strong class="command">master</strong></span> or
3038                   <span><strong class="command">slave</strong></span> zones respectively.
3039                   It is off by default.
3040                 </p>
3041 </dd>
3042 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
3043 <dd><p>
3044                   This should be set when you have multiple masters for a zone
3045                   and the
3046                   addresses refer to different machines.  If <strong class="userinput"><code>yes</code></strong>, <span><strong class="command">named</strong></span> will
3047                   not log
3048                   when the serial number on the master is less than what <span><strong class="command">named</strong></span>
3049                   currently
3050                   has.  The default is <strong class="userinput"><code>no</code></strong>.
3051                 </p></dd>
3052 <dt><span class="term"><span><strong class="command">dnssec-enable</strong></span></span></dt>
3053 <dd><p>
3054                   Enable DNSSEC support in <span><strong class="command">named</strong></span>.  Unless set to <strong class="userinput"><code>yes</code></strong>,
3055                   <span><strong class="command">named</strong></span> behaves as if it does not support DNSSEC.
3056                   The default is <strong class="userinput"><code>yes</code></strong>.
3057                 </p></dd>
3058 <dt><span class="term"><span><strong class="command">dnssec-validation</strong></span></span></dt>
3059 <dd><p>
3060                   Enable DNSSEC validation in <span><strong class="command">named</strong></span>.
3061                   Note <span><strong class="command">dnssec-enable</strong></span> also needs to be
3062                   set to <strong class="userinput"><code>yes</code></strong> to be effective.
3063                   The default is <strong class="userinput"><code>yes</code></strong>.
3064                 </p></dd>
3065 <dt><span class="term"><span><strong class="command">dnssec-accept-expired</strong></span></span></dt>
3066 <dd><p>
3067                   Accept expired signatures when verifying DNSSEC signatures.
3068                   The default is <strong class="userinput"><code>no</code></strong>.
3069                   Setting this option to "yes" leaves <span><strong class="command">named</strong></span> vulnerable to replay attacks.
3070                 </p></dd>
3071 <dt><span class="term"><span><strong class="command">querylog</strong></span></span></dt>
3072 <dd><p>
3073                   Specify whether query logging should be started when <span><strong class="command">named</strong></span>
3074                   starts.
3075                   If <span><strong class="command">querylog</strong></span> is not specified,
3076                   then the query logging
3077                   is determined by the presence of the logging category <span><strong class="command">queries</strong></span>.
3078                 </p></dd>
3079 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
3080 <dd>
3081 <p>
3082                   This option is used to restrict the character set and syntax
3083                   of
3084                   certain domain names in master files and/or DNS responses
3085                   received
3086                   from the network.  The default varies according to usage
3087                   area.  For
3088                   <span><strong class="command">master</strong></span> zones the default is <span><strong class="command">fail</strong></span>.
3089                   For <span><strong class="command">slave</strong></span> zones the default
3090                   is <span><strong class="command">warn</strong></span>.
3091                   For answers received from the network (<span><strong class="command">response</strong></span>)
3092                   the default is <span><strong class="command">ignore</strong></span>.
3093                 </p>
3094 <p>
3095                   The rules for legal hostnames and mail domains are derived
3096                   from RFC 952 and RFC 821 as modified by RFC 1123.
3097                 </p>
3098 <p><span><strong class="command">check-names</strong></span>
3099                   applies to the owner names of A, AAAA and MX records.
3100                   It also applies to the domain names in the RDATA of NS, SOA,
3101                   MX, and SRV records.
3102                   It also applies to the RDATA of PTR records where the owner
3103                   name indicated that it is a reverse lookup of a hostname
3104                   (the owner name ends in IN-ADDR.ARPA, IP6.ARPA, or IP6.INT).
3105                 </p>
3106 </dd>
3107 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
3108 <dd><p>
3109                   Check whether the MX record appears to refer to a IP address.
3110                   The default is to <span><strong class="command">warn</strong></span>.  Other possible
3111                   values are <span><strong class="command">fail</strong></span> and
3112                   <span><strong class="command">ignore</strong></span>.
3113                 </p></dd>
3114 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
3115 <dd><p>
3116                   This option is used to check for non-terminal wildcards.
3117                   The use of non-terminal wildcards is almost always as a
3118                   result of a failure
3119                   to understand the wildcard matching algorithm (RFC 1034).
3120                   This option
3121                   affects master zones.  The default (<span><strong class="command">yes</strong></span>) is to check
3122                   for non-terminal wildcards and issue a warning.
3123                 </p></dd>
3124 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
3125 <dd><p>
3126                   Perform post load zone integrity checks on master
3127                   zones.  This checks that MX and SRV records refer
3128                   to address (A or AAAA) records and that glue
3129                   address records exist for delegated zones.  For
3130                   MX and SRV records only in-zone hostnames are
3131                   checked (for out-of-zone hostnames use
3132                   <span><strong class="command">named-checkzone</strong></span>).
3133                   For NS records only names below top of zone are
3134                   checked (for out-of-zone names and glue consistency
3135                   checks use <span><strong class="command">named-checkzone</strong></span>).
3136                   The default is <span><strong class="command">yes</strong></span>.
3137                 </p></dd>
3138 <dt><span class="term"><span><strong class="command">check-mx-cname</strong></span></span></dt>
3139 <dd><p>
3140                   If <span><strong class="command">check-integrity</strong></span> is set then
3141                   fail, warn or ignore MX records that refer
3142                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
3143                 </p></dd>
3144 <dt><span class="term"><span><strong class="command">check-srv-cname</strong></span></span></dt>
3145 <dd><p>
3146                   If <span><strong class="command">check-integrity</strong></span> is set then
3147                   fail, warn or ignore SRV records that refer
3148                   to CNAMES.  The default is to <span><strong class="command">warn</strong></span>.
3149                 </p></dd>
3150 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
3151 <dd><p>
3152                   When performing integrity checks, also check that
3153                   sibling glue exists.  The default is <span><strong class="command">yes</strong></span>.
3154                 </p></dd>
3155 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
3156 <dd><p>
3157                   When returning authoritative negative responses to
3158                   SOA queries set the TTL of the SOA record returned in
3159                   the authority section to zero.
3160                   The default is <span><strong class="command">yes</strong></span>.
3161                 </p></dd>
3162 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl-cache</strong></span></span></dt>
3163 <dd><p>
3164                   When caching a negative response to a SOA query
3165                   set the TTL to zero.
3166                   The default is <span><strong class="command">no</strong></span>.
3167                 </p></dd>
3168 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
3169 <dd><p>
3170                   When regenerating the RRSIGs following a UPDATE
3171                   request to a secure zone, check the KSK flag on
3172                   the DNSKEY RR to determine if this key should be
3173                   used to generate the RRSIG.  This flag is ignored
3174                   if there are not DNSKEY RRs both with and without
3175                   a KSK.
3176                   The default is <span><strong class="command">yes</strong></span>.
3177                 </p></dd>
3178 <dt><span class="term"><span><strong class="command">try-tcp-refresh</strong></span></span></dt>
3179 <dd><p>
3180                   Try to refresh the zone using TCP if UDP queries fail.
3181                   For BIND 8 compatibility, the default is
3182                   <span><strong class="command">yes</strong></span>.
3183                 </p></dd>
3184 </dl></div>
3185 </div>
3186 <div class="sect3" lang="en">
3187 <div class="titlepage"><div><div><h4 class="title">
3188 <a name="id2581856"></a>Forwarding</h4></div></div></div>
3189 <p>
3190             The forwarding facility can be used to create a large site-wide
3191             cache on a few servers, reducing traffic over links to external
3192             name servers. It can also be used to allow queries by servers that
3193             do not have direct access to the Internet, but wish to look up
3194             exterior
3195             names anyway. Forwarding occurs only on those queries for which
3196             the server is not authoritative and does not have the answer in
3197             its cache.
3198           </p>
3199 <div class="variablelist"><dl>
3200 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
3201 <dd><p>
3202                   This option is only meaningful if the
3203                   forwarders list is not empty. A value of <code class="varname">first</code>,
3204                   the default, causes the server to query the forwarders
3205                   first &#8212; and
3206                   if that doesn't answer the question, the server will then
3207                   look for
3208                   the answer itself. If <code class="varname">only</code> is
3209                   specified, the
3210                   server will only query the forwarders.
3211                 </p></dd>
3212 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
3213 <dd><p>
3214                   Specifies the IP addresses to be used
3215                   for forwarding. The default is the empty list (no
3216                   forwarding).
3217                 </p></dd>
3218 </dl></div>
3219 <p>
3220             Forwarding can also be configured on a per-domain basis, allowing
3221             for the global forwarding options to be overridden in a variety
3222             of ways. You can set particular domains to use different
3223             forwarders,
3224             or have a different <span><strong class="command">forward only/first</strong></span> behavior,
3225             or not forward at all, see <a href="Bv9ARM.ch06.html#zone_statement_grammar" title="zone
3226             Statement Grammar">the section called &#8220;<span><strong class="command">zone</strong></span>
3227             Statement Grammar&#8221;</a>.
3228           </p>
3229 </div>
3230 <div class="sect3" lang="en">
3231 <div class="titlepage"><div><div><h4 class="title">
3232 <a name="id2581914"></a>Dual-stack Servers</h4></div></div></div>
3233 <p>
3234             Dual-stack servers are used as servers of last resort to work
3235             around
3236             problems in reachability due the lack of support for either IPv4
3237             or IPv6
3238             on the host machine.
3239           </p>
3240 <div class="variablelist"><dl>
3241 <dt><span class="term"><span><strong class="command">dual-stack-servers</strong></span></span></dt>
3242 <dd><p>
3243                   Specifies host names or addresses of machines with access to
3244                   both IPv4 and IPv6 transports. If a hostname is used, the
3245                   server must be able
3246                   to resolve the name using only the transport it has.  If the
3247                   machine is dual
3248                   stacked, then the <span><strong class="command">dual-stack-servers</strong></span> have no effect unless
3249                   access to a transport has been disabled on the command line
3250                   (e.g. <span><strong class="command">named -4</strong></span>).
3251                 </p></dd>
3252 </dl></div>
3253 </div>
3254 <div class="sect3" lang="en">
3255 <div class="titlepage"><div><div><h4 class="title">
3256 <a name="access_control"></a>Access Control</h4></div></div></div>
3257 <p>
3258             Access to the server can be restricted based on the IP address
3259             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
3260             details on how to specify IP address lists.
3261           </p>
3262 <div class="variablelist"><dl>
3263 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
3264 <dd><p>
3265                   Specifies which hosts are allowed to
3266                   notify this server, a slave, of zone changes in addition
3267                   to the zone masters.
3268                   <span><strong class="command">allow-notify</strong></span> may also be
3269                   specified in the
3270                   <span><strong class="command">zone</strong></span> statement, in which case
3271                   it overrides the
3272                   <span><strong class="command">options allow-notify</strong></span>
3273                   statement.  It is only meaningful
3274                   for a slave zone.  If not specified, the default is to
3275                   process notify messages
3276                   only from a zone's master.
3277                 </p></dd>
3278 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
3279 <dd>
3280 <p>
3281                   Specifies which hosts are allowed to ask ordinary
3282                   DNS questions. <span><strong class="command">allow-query</strong></span> may
3283                   also be specified in the <span><strong class="command">zone</strong></span>
3284                   statement, in which case it overrides the
3285                   <span><strong class="command">options allow-query</strong></span> statement.
3286                   If not specified, the default is to allow queries
3287                   from all hosts.
3288                 </p>
3289 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3290 <h3 class="title">Note</h3>
3291 <p>
3292                     <span><strong class="command">allow-query-cache</strong></span> is now
3293                     used to specify access to the cache.
3294                   </p>
3295 </div>
3296 </dd>
3297 <dt><span class="term"><span><strong class="command">allow-query-on</strong></span></span></dt>
3298 <dd>
3299 <p>
3300                   Specifies which local addresses can accept ordinary
3301                   DNS questions. This makes it possible, for instance,
3302                   to allow queries on internal-facing interfaces but
3303                   disallow them on external-facing ones, without
3304                   necessarily knowing the internal network's addresses.
3305                 </p>
3306 <p>
3307                   <span><strong class="command">allow-query-on</strong></span> may
3308                   also be specified in the <span><strong class="command">zone</strong></span>
3309                   statement, in which case it overrides the
3310                   <span><strong class="command">options allow-query-on</strong></span> statement.
3311                 </p>
3312 <p>
3313                   If not specified, the default is to allow queries
3314                   on all addresses.
3315                 </p>
3316 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3317 <h3 class="title">Note</h3>
3318 <p>
3319                     <span><strong class="command">allow-query-cache</strong></span> is
3320                     used to specify access to the cache.
3321                   </p>
3322 </div>
3323 </dd>
3324 <dt><span class="term"><span><strong class="command">allow-query-cache</strong></span></span></dt>
3325 <dd><p>
3326                   Specifies which hosts are allowed to get answers
3327                   from the cache.  If <span><strong class="command">allow-query-cache</strong></span>
3328                   is not set then <span><strong class="command">allow-recursion</strong></span>
3329                   is used if set, otherwise <span><strong class="command">allow-query</strong></span>
3330                   is used if set unless <span><strong class="command">recursion no;</strong></span> is
3331                   set in which case <span><strong class="command">none;</strong></span> is used,
3332                   otherwise the default (<span><strong class="command">localnets;</strong></span>
3333                   <span><strong class="command">localhost;</strong></span>) is used.
3334                 </p></dd>
3335 <dt><span class="term"><span><strong class="command">allow-query-cache-on</strong></span></span></dt>
3336 <dd><p>
3337                   Specifies which local addresses can give answers
3338                   from the cache.  If not specified, the default is
3339                   to allow cache queries on any address,
3340                   <span><strong class="command">localnets</strong></span> and
3341                   <span><strong class="command">localhost</strong></span>.
3342                 </p></dd>
3343 <dt><span class="term"><span><strong class="command">allow-recursion</strong></span></span></dt>
3344 <dd><p>
3345                   Specifies which hosts are allowed to make recursive
3346                   queries through this server. If
3347                   <span><strong class="command">allow-recursion</strong></span> is not set
3348                   then <span><strong class="command">allow-query-cache</strong></span> is
3349                   used if set, otherwise <span><strong class="command">allow-query</strong></span>
3350                   is used if set, otherwise the default
3351                   (<span><strong class="command">localnets;</strong></span>
3352                   <span><strong class="command">localhost;</strong></span>) is used.
3353                 </p></dd>
3354 <dt><span class="term"><span><strong class="command">allow-recursion-on</strong></span></span></dt>
3355 <dd><p>
3356                   Specifies which local addresses can accept recursive
3357                   queries.  If not specified, the default is to allow
3358                   recursive queries on all addresses.
3359                 </p></dd>
3360 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
3361 <dd><p>
3362                   Specifies which hosts are allowed to
3363                   submit Dynamic DNS updates for master zones. The default is
3364                   to deny
3365                   updates from all hosts.  Note that allowing updates based
3366                   on the requestor's IP address is insecure; see
3367                   <a href="Bv9ARM.ch07.html#dynamic_update_security" title="Dynamic Update Security">the section called &#8220;Dynamic Update Security&#8221;</a> for details.
3368                 </p></dd>
3369 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
3370 <dd>
3371 <p>
3372                   Specifies which hosts are allowed to
3373                   submit Dynamic DNS updates to slave zones to be forwarded to
3374                   the
3375                   master.  The default is <strong class="userinput"><code>{ none; }</code></strong>,
3376                   which
3377                   means that no update forwarding will be performed.  To
3378                   enable
3379                   update forwarding, specify
3380                   <strong class="userinput"><code>allow-update-forwarding { any; };</code></strong>.
3381                   Specifying values other than <strong class="userinput"><code>{ none; }</code></strong> or
3382                   <strong class="userinput"><code>{ any; }</code></strong> is usually
3383                   counterproductive, since
3384                   the responsibility for update access control should rest
3385                   with the
3386                   master server, not the slaves.
3387                 </p>
3388 <p>
3389                   Note that enabling the update forwarding feature on a slave
3390                   server
3391                   may expose master servers relying on insecure IP address
3392                   based
3393                   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>
3394                   for more details.
3395                 </p>
3396 </dd>
3397 <dt><span class="term"><span><strong class="command">allow-v6-synthesis</strong></span></span></dt>
3398 <dd><p>
3399                   This option was introduced for the smooth transition from
3400                   AAAA
3401                   to A6 and from "nibble labels" to binary labels.
3402                   However, since both A6 and binary labels were then
3403                   deprecated,
3404                   this option was also deprecated.
3405                   It is now ignored with some warning messages.
3406                 </p></dd>
3407 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
3408 <dd><p>
3409                   Specifies which hosts are allowed to
3410                   receive zone transfers from the server. <span><strong class="command">allow-transfer</strong></span> may
3411                   also be specified in the <span><strong class="command">zone</strong></span>
3412                   statement, in which
3413                   case it overrides the <span><strong class="command">options allow-transfer</strong></span> statement.
3414                   If not specified, the default is to allow transfers to all
3415                   hosts.
3416                 </p></dd>
3417 <dt><span class="term"><span><strong class="command">blackhole</strong></span></span></dt>
3418 <dd><p>
3419                   Specifies a list of addresses that the
3420                   server will not accept queries from or use to resolve a
3421                   query. Queries
3422                   from these addresses will not be responded to. The default
3423                   is <strong class="userinput"><code>none</code></strong>.
3424                 </p></dd>
3425 </dl></div>
3426 </div>
3427 <div class="sect3" lang="en">
3428 <div class="titlepage"><div><div><h4 class="title">
3429 <a name="id2582420"></a>Interfaces</h4></div></div></div>
3430 <p>
3431             The interfaces and ports that the server will answer queries
3432             from may be specified using the <span><strong class="command">listen-on</strong></span> option. <span><strong class="command">listen-on</strong></span> takes
3433             an optional port and an <code class="varname">address_match_list</code>.
3434             The server will listen on all interfaces allowed by the address
3435             match list. If a port is not specified, port 53 will be used.
3436           </p>
3437 <p>
3438             Multiple <span><strong class="command">listen-on</strong></span> statements are
3439             allowed.
3440             For example,
3441           </p>
3442 <pre class="programlisting">listen-on { 5.6.7.8; };
3443 listen-on port 1234 { !1.2.3.4; 1.2/16; };
3444 </pre>
3445 <p>
3446             will enable the name server on port 53 for the IP address
3447             5.6.7.8, and on port 1234 of an address on the machine in net
3448             1.2 that is not 1.2.3.4.
3449           </p>
3450 <p>
3451             If no <span><strong class="command">listen-on</strong></span> is specified, the
3452             server will listen on port 53 on all IPv4 interfaces.
3453           </p>
3454 <p>
3455             The <span><strong class="command">listen-on-v6</strong></span> option is used to
3456             specify the interfaces and the ports on which the server will
3457             listen
3458             for incoming queries sent using IPv6.
3459           </p>
3460 <p>
3461             When </p>
3462 <pre class="programlisting">{ any; }</pre>
3463 <p> is
3464             specified
3465             as the <code class="varname">address_match_list</code> for the
3466             <span><strong class="command">listen-on-v6</strong></span> option,
3467             the server does not bind a separate socket to each IPv6 interface
3468             address as it does for IPv4 if the operating system has enough API
3469             support for IPv6 (specifically if it conforms to RFC 3493 and RFC
3470             3542).
3471             Instead, it listens on the IPv6 wildcard address.
3472             If the system only has incomplete API support for IPv6, however,
3473             the behavior is the same as that for IPv4.
3474           </p>
3475 <p>
3476             A list of particular IPv6 addresses can also be specified, in
3477             which case
3478             the server listens on a separate socket for each specified
3479             address,
3480             regardless of whether the desired API is supported by the system.
3481           </p>
3482 <p>
3483             Multiple <span><strong class="command">listen-on-v6</strong></span> options can
3484             be used.
3485             For example,
3486           </p>
3487 <pre class="programlisting">listen-on-v6 { any; };
3488 listen-on-v6 port 1234 { !2001:db8::/32; any; };
3489 </pre>
3490 <p>
3491             will enable the name server on port 53 for any IPv6 addresses
3492             (with a single wildcard socket),
3493             and on port 1234 of IPv6 addresses that is not in the prefix
3494             2001:db8::/32 (with separate sockets for each matched address.)
3495           </p>
3496 <p>
3497             To make the server not listen on any IPv6 address, use
3498           </p>
3499 <pre class="programlisting">listen-on-v6 { none; };
3500 </pre>
3501 <p>
3502             If no <span><strong class="command">listen-on-v6</strong></span> option is
3503             specified, the server will not listen on any IPv6 address
3504             unless <span><strong class="command">-6</strong></span> is specified when <span><strong class="command">named</strong></span> is
3505             invoked.  If <span><strong class="command">-6</strong></span> is specified then
3506             <span><strong class="command">named</strong></span> will listen on port 53 on all IPv6 interfaces by default.
3507           </p>
3508 </div>
3509 <div class="sect3" lang="en">
3510 <div class="titlepage"><div><div><h4 class="title">
3511 <a name="query_address"></a>Query Address</h4></div></div></div>
3512 <p>
3513             If the server doesn't know the answer to a question, it will
3514             query other name servers. <span><strong class="command">query-source</strong></span> specifies
3515             the address and port used for such queries. For queries sent over
3516             IPv6, there is a separate <span><strong class="command">query-source-v6</strong></span> option.
3517             If <span><strong class="command">address</strong></span> is <span><strong class="command">*</strong></span> (asterisk) or is omitted,
3518             a wildcard IP address (<span><strong class="command">INADDR_ANY</strong></span>)
3519             will be used.
3520           </p>
3521 <p>
3522             If <span><strong class="command">port</strong></span> is <span><strong class="command">*</strong></span> or is omitted,
3523             a random port number from a pre-configured
3524             range is picked up and will be used for each query.
3525             The port range(s) is that specified in
3526             the <span><strong class="command">use-v4-udp-ports</strong></span> (for IPv4)
3527             and <span><strong class="command">use-v6-udp-ports</strong></span> (for IPv6)
3528             options, excluding the ranges specified in
3529             the <span><strong class="command">avoid-v4-udp-ports</strong></span>
3530             and <span><strong class="command">avoid-v6-udp-ports</strong></span> options, respectively.
3531           </p>
3532 <p>
3533             The defaults of the <span><strong class="command">query-source</strong></span> and
3534             <span><strong class="command">query-source-v6</strong></span> options
3535             are:
3536           </p>
3537 <pre class="programlisting">query-source address * port *;
3538 query-source-v6 address * port *;
3539 </pre>
3540 <p>
3541             If <span><strong class="command">use-v4-udp-ports</strong></span> or
3542             <span><strong class="command">use-v6-udp-ports</strong></span> is unspecified,
3543             <span><strong class="command">named</strong></span> will check if the operating
3544             system provides a programming interface to retrieve the
3545             system's default range for ephemeral ports.
3546             If such an interface is available,
3547             <span><strong class="command">named</strong></span> will use the corresponding system
3548             default range; otherwise, it will use its own defaults:
3549          </p>
3550 <pre class="programlisting">use-v4-udp-ports { range 1024 65535; };
3551 use-v6-udp-ports { range 1024 65535; };
3552 </pre>
3553 <p>
3554             Note: make sure the ranges be sufficiently large for
3555             security.  A desirable size depends on various parameters,
3556             but we generally recommend it contain at least 16384 ports
3557             (14 bits of entropy).
3558             Note also that the system's default range when used may be
3559             too small for this purpose, and that the range may even be
3560             changed while <span><strong class="command">named</strong></span> is running; the new
3561             range will automatically be applied when <span><strong class="command">named</strong></span>
3562             is reloaded.
3563             It is encouraged to
3564             configure <span><strong class="command">use-v4-udp-ports</strong></span> and
3565             <span><strong class="command">use-v6-udp-ports</strong></span> explicitly so that the
3566             ranges are sufficiently large and are reasonably
3567             independent from the ranges used by other applications.
3568           </p>
3569 <p>
3570             Note: the operational configuration
3571             where <span><strong class="command">named</strong></span> runs may prohibit the use
3572             of some ports.  For example, UNIX systems will not allow
3573             <span><strong class="command">named</strong></span> running without a root privilege
3574             to use ports less than 1024.
3575             If such ports are included in the specified (or detected)
3576             set of query ports, the corresponding query attempts will
3577             fail, resulting in resolution failures or delay.
3578             It is therefore important to configure the set of ports
3579             that can be safely used in the expected operational environment.
3580           </p>
3581 <p>
3582             The defaults of the <span><strong class="command">avoid-v4-udp-ports</strong></span> and
3583             <span><strong class="command">avoid-v6-udp-ports</strong></span> options
3584             are:
3585           </p>
3586 <pre class="programlisting">avoid-v4-udp-ports {};
3587 avoid-v6-udp-ports {};
3588 </pre>
3589 <p>
3590             Note: BIND 9.5.0 introduced
3591             the <span><strong class="command">use-queryport-pool</strong></span>
3592             option to support a pool of such random ports, but this
3593             option is now obsolete because reusing the same ports in
3594             the pool may not be sufficiently secure.
3595             For the same reason, it is generally strongly discouraged to
3596             specify a particular port for the
3597             <span><strong class="command">query-source</strong></span> or
3598             <span><strong class="command">query-source-v6</strong></span> options;
3599             it implicitly disables the use of randomized port numbers.
3600           </p>
3601 <div class="variablelist"><dl>
3602 <dt><span class="term"><span><strong class="command">use-queryport-pool</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-ports</strong></span></span></dt>
3607 <dd><p>
3608                   This option is obsolete.
3609                 </p></dd>
3610 <dt><span class="term"><span><strong class="command">queryport-pool-updateinterval</strong></span></span></dt>
3611 <dd><p>
3612                   This option is obsolete.
3613                 </p></dd>
3614 </dl></div>
3615 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3616 <h3 class="title">Note</h3>
3617 <p>
3618               The address specified in the <span><strong class="command">query-source</strong></span> option
3619               is used for both UDP and TCP queries, but the port applies only
3620               to UDP queries.  TCP queries always use a random
3621               unprivileged port.
3622             </p>
3623 </div>
3624 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3625 <h3 class="title">Note</h3>
3626 <p>
3627               Solaris 2.5.1 and earlier does not support setting the source
3628               address for TCP sockets.
3629             </p>
3630 </div>
3631 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3632 <h3 class="title">Note</h3>
3633 <p>
3634               See also <span><strong class="command">transfer-source</strong></span> and
3635               <span><strong class="command">notify-source</strong></span>.
3636             </p>
3637 </div>
3638 </div>
3639 <div class="sect3" lang="en">
3640 <div class="titlepage"><div><div><h4 class="title">
3641 <a name="zone_transfers"></a>Zone Transfers</h4></div></div></div>
3642 <p>
3643             <acronym class="acronym">BIND</acronym> has mechanisms in place to
3644             facilitate zone transfers
3645             and set limits on the amount of load that transfers place on the
3646             system. The following options apply to zone transfers.
3647           </p>
3648 <div class="variablelist"><dl>
3649 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
3650 <dd><p>
3651                   Defines a global list of IP addresses of name servers
3652                   that are also sent NOTIFY messages whenever a fresh copy of
3653                   the
3654                   zone is loaded, in addition to the servers listed in the
3655                   zone's NS records.
3656                   This helps to ensure that copies of the zones will
3657                   quickly converge on stealth servers.
3658                   Optionally, a port may be specified with each
3659                   <span><strong class="command">also-notify</strong></span> address to send
3660                   the notify messages to a port other than the
3661                   default of 53.
3662                   If an <span><strong class="command">also-notify</strong></span> list
3663                   is given in a <span><strong class="command">zone</strong></span> statement,
3664                   it will override
3665                   the <span><strong class="command">options also-notify</strong></span>
3666                   statement. When a <span><strong class="command">zone notify</strong></span>
3667                   statement
3668                   is set to <span><strong class="command">no</strong></span>, the IP
3669                   addresses in the global <span><strong class="command">also-notify</strong></span> list will
3670                   not be sent NOTIFY messages for that zone. The default is
3671                   the empty
3672                   list (no global notification list).
3673                 </p></dd>
3674 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
3675 <dd><p>
3676                   Inbound zone transfers running longer than
3677                   this many minutes will be terminated. The default is 120
3678                   minutes
3679                   (2 hours).  The maximum value is 28 days (40320 minutes).
3680                 </p></dd>
3681 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
3682 <dd><p>
3683                   Inbound zone transfers making no progress
3684                   in this many minutes will be terminated. The default is 60
3685                   minutes
3686                   (1 hour).  The maximum value is 28 days (40320 minutes).
3687                 </p></dd>
3688 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
3689 <dd><p>
3690                   Outbound zone transfers running longer than
3691                   this many minutes will be terminated. The default is 120
3692                   minutes
3693                   (2 hours).  The maximum value is 28 days (40320 minutes).
3694                 </p></dd>
3695 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
3696 <dd><p>
3697                   Outbound zone transfers making no progress
3698                   in this many minutes will be terminated.  The default is 60
3699                   minutes (1
3700                   hour).  The maximum value is 28 days (40320 minutes).
3701                 </p></dd>
3702 <dt><span class="term"><span><strong class="command">serial-query-rate</strong></span></span></dt>
3703 <dd><p>
3704                   Slave servers will periodically query master servers
3705                   to find out if zone serial numbers have changed. Each such
3706                   query uses
3707                   a minute amount of the slave server's network bandwidth.  To
3708                   limit the
3709                   amount of bandwidth used, BIND 9 limits the rate at which
3710                   queries are
3711                   sent.  The value of the <span><strong class="command">serial-query-rate</strong></span> option,
3712                   an integer, is the maximum number of queries sent per
3713                   second.
3714                   The default is 20.
3715                 </p></dd>
3716 <dt><span class="term"><span><strong class="command">serial-queries</strong></span></span></dt>
3717 <dd><p>
3718                   In BIND 8, the <span><strong class="command">serial-queries</strong></span>
3719                   option
3720                   set the maximum number of concurrent serial number queries
3721                   allowed to be outstanding at any given time.
3722                   BIND 9 does not limit the number of outstanding
3723                   serial queries and ignores the <span><strong class="command">serial-queries</strong></span> option.
3724                   Instead, it limits the rate at which the queries are sent
3725                   as defined using the <span><strong class="command">serial-query-rate</strong></span> option.
3726                 </p></dd>
3727 <dt><span class="term"><span><strong class="command">transfer-format</strong></span></span></dt>
3728 <dd><p>
3729                   Zone transfers can be sent using two different formats,
3730                   <span><strong class="command">one-answer</strong></span> and
3731                   <span><strong class="command">many-answers</strong></span>.
3732                   The <span><strong class="command">transfer-format</strong></span> option is used
3733                   on the master server to determine which format it sends.
3734                   <span><strong class="command">one-answer</strong></span> uses one DNS message per
3735                   resource record transferred.
3736                   <span><strong class="command">many-answers</strong></span> packs as many resource
3737                   records as possible into a message.
3738                   <span><strong class="command">many-answers</strong></span> is more efficient, but is
3739                   only supported by relatively new slave servers,
3740                   such as <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
3741                   8.x and <acronym class="acronym">BIND</acronym> 4.9.5 onwards.
3742                   The <span><strong class="command">many-answers</strong></span> format is also supported by
3743                   recent Microsoft Windows nameservers.
3744                   The default is <span><strong class="command">many-answers</strong></span>.
3745                   <span><strong class="command">transfer-format</strong></span> may be overridden on a
3746                   per-server basis by using the <span><strong class="command">server</strong></span>
3747                   statement.
3748                 </p></dd>
3749 <dt><span class="term"><span><strong class="command">transfers-in</strong></span></span></dt>
3750 <dd><p>
3751                   The maximum number of inbound zone transfers
3752                   that can be running concurrently. The default value is <code class="literal">10</code>.
3753                   Increasing <span><strong class="command">transfers-in</strong></span> may
3754                   speed up the convergence
3755                   of slave zones, but it also may increase the load on the
3756                   local system.
3757                 </p></dd>
3758 <dt><span class="term"><span><strong class="command">transfers-out</strong></span></span></dt>
3759 <dd><p>
3760                   The maximum number of outbound zone transfers
3761                   that can be running concurrently. Zone transfer requests in
3762                   excess
3763                   of the limit will be refused. The default value is <code class="literal">10</code>.
3764                 </p></dd>
3765 <dt><span class="term"><span><strong class="command">transfers-per-ns</strong></span></span></dt>
3766 <dd><p>
3767                   The maximum number of inbound zone transfers
3768                   that can be concurrently transferring from a given remote
3769                   name server.
3770                   The default value is <code class="literal">2</code>.
3771                   Increasing <span><strong class="command">transfers-per-ns</strong></span>
3772                   may
3773                   speed up the convergence of slave zones, but it also may
3774                   increase
3775                   the load on the remote name server. <span><strong class="command">transfers-per-ns</strong></span> may
3776                   be overridden on a per-server basis by using the <span><strong class="command">transfers</strong></span> phrase
3777                   of the <span><strong class="command">server</strong></span> statement.
3778                 </p></dd>
3779 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
3780 <dd>
3781 <p><span><strong class="command">transfer-source</strong></span>
3782                   determines which local address will be bound to IPv4
3783                   TCP connections used to fetch zones transferred
3784                   inbound by the server.  It also determines the
3785                   source IPv4 address, and optionally the UDP port,
3786                   used for the refresh queries and forwarded dynamic
3787                   updates.  If not set, it defaults to a system
3788                   controlled value which will usually be the address
3789                   of the interface "closest to" the remote end. This
3790                   address must appear in the remote end's
3791                   <span><strong class="command">allow-transfer</strong></span> option for the
3792                   zone being transferred, if one is specified. This
3793                   statement sets the
3794                   <span><strong class="command">transfer-source</strong></span> for all zones,
3795                   but can be overridden on a per-view or per-zone
3796                   basis by including a
3797                   <span><strong class="command">transfer-source</strong></span> statement within
3798                   the <span><strong class="command">view</strong></span> or
3799                   <span><strong class="command">zone</strong></span> block in the configuration
3800                   file.
3801                 </p>
3802 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3803 <h3 class="title">Note</h3>
3804 <p>
3805                     Solaris 2.5.1 and earlier does not support setting the
3806                     source address for TCP sockets.
3807                   </p>
3808 </div>
3809 </dd>
3810 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
3811 <dd><p>
3812                   The same as <span><strong class="command">transfer-source</strong></span>,
3813                   except zone transfers are performed using IPv6.
3814                 </p></dd>
3815 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
3816 <dd>
3817 <p>
3818                   An alternate transfer source if the one listed in
3819                   <span><strong class="command">transfer-source</strong></span> fails and
3820                   <span><strong class="command">use-alt-transfer-source</strong></span> is
3821                   set.
3822                 </p>
3823 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3824 <h3 class="title">Note</h3>
3825                   If you do not wish the alternate transfer source
3826                   to be used, you should set
3827                   <span><strong class="command">use-alt-transfer-source</strong></span>
3828                   appropriately and you should not depend upon
3829                   getting an answer back to the first refresh
3830                   query.
3831                 </div>
3832 </dd>
3833 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
3834 <dd><p>
3835                   An alternate transfer source if the one listed in
3836                   <span><strong class="command">transfer-source-v6</strong></span> fails and
3837                   <span><strong class="command">use-alt-transfer-source</strong></span> is
3838                   set.
3839                 </p></dd>
3840 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
3841 <dd><p>
3842                   Use the alternate transfer sources or not.  If views are
3843                   specified this defaults to <span><strong class="command">no</strong></span>
3844                   otherwise it defaults to
3845                   <span><strong class="command">yes</strong></span> (for BIND 8
3846                   compatibility).
3847                 </p></dd>
3848 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
3849 <dd>
3850 <p><span><strong class="command">notify-source</strong></span>
3851                   determines which local source address, and
3852                   optionally UDP port, will be used to send NOTIFY
3853                   messages.  This address must appear in the slave
3854                   server's <span><strong class="command">masters</strong></span> zone clause or
3855                   in an <span><strong class="command">allow-notify</strong></span> clause.  This
3856                   statement sets the <span><strong class="command">notify-source</strong></span>
3857                   for all zones, but can be overridden on a per-zone or
3858                   per-view basis by including a
3859                   <span><strong class="command">notify-source</strong></span> statement within
3860                   the <span><strong class="command">zone</strong></span> or
3861                   <span><strong class="command">view</strong></span> block in the configuration
3862                   file.
3863                 </p>
3864 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
3865 <h3 class="title">Note</h3>
3866 <p>
3867                     Solaris 2.5.1 and earlier does not support setting the
3868                     source address for TCP sockets.
3869                   </p>
3870 </div>
3871 </dd>
3872 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
3873 <dd><p>
3874                   Like <span><strong class="command">notify-source</strong></span>,
3875                   but applies to notify messages sent to IPv6 addresses.
3876                 </p></dd>
3877 </dl></div>
3878 </div>
3879 <div class="sect3" lang="en">
3880 <div class="titlepage"><div><div><h4 class="title">
3881 <a name="id2583691"></a>UDP Port Lists</h4></div></div></div>
3882 <p>
3883             <span><strong class="command">use-v4-udp-ports</strong></span>,
3884             <span><strong class="command">avoid-v4-udp-ports</strong></span>,
3885             <span><strong class="command">use-v6-udp-ports</strong></span>, and
3886             <span><strong class="command">avoid-v6-udp-ports</strong></span>
3887             specify a list of IPv4 and IPv6 UDP ports that will be
3888             used or not used as source ports for UDP messages.
3889             See <a href="Bv9ARM.ch06.html#query_address" title="Query Address">the section called &#8220;Query Address&#8221;</a> about how the
3890             available ports are determined.
3891             For example, with the following configuration
3892           </p>
3893 <pre class="programlisting">
3894 use-v6-udp-ports { range 32768 65535; };
3895 avoid-v6-udp-ports { 40000; range 50000 60000; };
3896 </pre>
3897 <p>
3898              UDP ports of IPv6 messages sent
3899              from <span><strong class="command">named</strong></span> will be in one
3900              of the following ranges: 32768 to 39999, 40001 to 49999,
3901              and 60001 to 65535.
3902            </p>
3903 <p>
3904              <span><strong class="command">avoid-v4-udp-ports</strong></span> and
3905              <span><strong class="command">avoid-v6-udp-ports</strong></span> can be used
3906              to prevent <span><strong class="command">named</strong></span> from choosing as its random source port a
3907              port that is blocked by your firewall or a port that is
3908              used by other applications;
3909              if a query went out with a source port blocked by a
3910              firewall, the
3911              answer would not get by the firewall and the name server would
3912              have to query again.
3913              Note: the desired range can also be represented only with
3914              <span><strong class="command">use-v4-udp-ports</strong></span> and
3915              <span><strong class="command">use-v6-udp-ports</strong></span>, and the
3916              <span><strong class="command">avoid-</strong></span> options are redundant in that
3917              sense; they are provided for backward compatibility and
3918              to possibly simplify the port specification.
3919            </p>
3920 </div>
3921 <div class="sect3" lang="en">
3922 <div class="titlepage"><div><div><h4 class="title">
3923 <a name="id2583751"></a>Operating System Resource Limits</h4></div></div></div>
3924 <p>
3925             The server's usage of many system resources can be limited.
3926             Scaled values are allowed when specifying resource limits.  For
3927             example, <span><strong class="command">1G</strong></span> can be used instead of
3928             <span><strong class="command">1073741824</strong></span> to specify a limit of
3929             one
3930             gigabyte. <span><strong class="command">unlimited</strong></span> requests
3931             unlimited use, or the
3932             maximum available amount. <span><strong class="command">default</strong></span>
3933             uses the limit
3934             that was in force when the server was started. See the description
3935             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>.
3936           </p>
3937 <p>
3938             The following options set operating system resource limits for
3939             the name server process.  Some operating systems don't support
3940             some or
3941             any of the limits. On such systems, a warning will be issued if
3942             the
3943             unsupported limit is used.
3944           </p>
3945 <div class="variablelist"><dl>
3946 <dt><span class="term"><span><strong class="command">coresize</strong></span></span></dt>
3947 <dd><p>
3948                   The maximum size of a core dump. The default
3949                   is <code class="literal">default</code>.
3950                 </p></dd>
3951 <dt><span class="term"><span><strong class="command">datasize</strong></span></span></dt>
3952 <dd><p>
3953                   The maximum amount of data memory the server
3954                   may use. The default is <code class="literal">default</code>.
3955                   This is a hard limit on server memory usage.
3956                   If the server attempts to allocate memory in excess of this
3957                   limit, the allocation will fail, which may in turn leave
3958                   the server unable to perform DNS service.  Therefore,
3959                   this option is rarely useful as a way of limiting the
3960                   amount of memory used by the server, but it can be used
3961                   to raise an operating system data size limit that is
3962                   too small by default.  If you wish to limit the amount
3963                   of memory used by the server, use the
3964                   <span><strong class="command">max-cache-size</strong></span> and
3965                   <span><strong class="command">recursive-clients</strong></span>
3966                   options instead.
3967                 </p></dd>
3968 <dt><span class="term"><span><strong class="command">files</strong></span></span></dt>
3969 <dd><p>
3970                   The maximum number of files the server
3971                   may have open concurrently. The default is <code class="literal">unlimited</code>.
3972                 </p></dd>
3973 <dt><span class="term"><span><strong class="command">stacksize</strong></span></span></dt>
3974 <dd><p>
3975                   The maximum amount of stack memory the server
3976                   may use. The default is <code class="literal">default</code>.
3977                 </p></dd>
3978 </dl></div>
3979 </div>
3980 <div class="sect3" lang="en">
3981 <div class="titlepage"><div><div><h4 class="title">
3982 <a name="server_resource_limits"></a>Server  Resource Limits</h4></div></div></div>
3983 <p>
3984             The following options set limits on the server's
3985             resource consumption that are enforced internally by the
3986             server rather than the operating system.
3987           </p>
3988 <div class="variablelist"><dl>
3989 <dt><span class="term"><span><strong class="command">max-ixfr-log-size</strong></span></span></dt>
3990 <dd><p>
3991                   This option is obsolete; it is accepted
3992                   and ignored for BIND 8 compatibility.  The option
3993                   <span><strong class="command">max-journal-size</strong></span> performs a
3994                   similar function in BIND 9.
3995                 </p></dd>
3996 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
3997 <dd><p>
3998                   Sets a maximum size for each journal file
3999                   (see <a href="Bv9ARM.ch04.html#journal" title="The journal file">the section called &#8220;The journal file&#8221;</a>).  When the journal file
4000                   approaches
4001                   the specified size, some of the oldest transactions in the
4002                   journal
4003                   will be automatically removed.  The default is
4004                   <code class="literal">unlimited</code>.
4005                   This may also be set on a per-zone basis.
4006                 </p></dd>
4007 <dt><span class="term"><span><strong class="command">host-statistics-max</strong></span></span></dt>
4008 <dd><p>
4009                   In BIND 8, specifies the maximum number of host statistics
4010                   entries to be kept.
4011                   Not implemented in BIND 9.
4012                 </p></dd>
4013 <dt><span class="term"><span><strong class="command">recursive-clients</strong></span></span></dt>
4014 <dd><p>
4015                   The maximum number of simultaneous recursive lookups
4016                   the server will perform on behalf of clients.  The default
4017                   is
4018                   <code class="literal">1000</code>.  Because each recursing
4019                   client uses a fair
4020                   bit of memory, on the order of 20 kilobytes, the value of
4021                   the
4022                   <span><strong class="command">recursive-clients</strong></span> option may
4023                   have to be decreased
4024                   on hosts with limited memory.
4025                 </p></dd>
4026 <dt><span class="term"><span><strong class="command">tcp-clients</strong></span></span></dt>
4027 <dd><p>
4028                   The maximum number of simultaneous client TCP
4029                   connections that the server will accept.
4030                   The default is <code class="literal">100</code>.
4031                 </p></dd>
4032 <dt><span class="term"><span><strong class="command">reserved-sockets</strong></span></span></dt>
4033 <dd>
4034 <p>
4035                   The number of file descriptors reserved for TCP, stdio,
4036                   etc.  This needs to be big enough to cover the number of
4037                   interfaces <span><strong class="command">named</strong></span> listens on, <span><strong class="command">tcp-clients</strong></span> as well as
4038                   to provide room for outgoing TCP queries and incoming zone
4039                   transfers.  The default is <code class="literal">512</code>.
4040                   The minimum value is <code class="literal">128</code> and the
4041                   maximum value is <code class="literal">128</code> less than
4042                   maxsockets (-S).  This option may be removed in the future.
4043                 </p>
4044 <p>
4045                   This option has little effect on Windows.
4046                 </p>
4047 </dd>
4048 <dt><span class="term"><span><strong class="command">max-cache-size</strong></span></span></dt>
4049 <dd><p>
4050                   The maximum amount of memory to use for the
4051                   server's cache, in bytes.
4052                   When the amount of data in the cache
4053                   reaches this limit, the server will cause records to expire
4054                   prematurely based on an LRU based strategy so that
4055                   the limit is not exceeded.
4056                   A value of 0 is special, meaning that
4057                   records are purged from the cache only when their
4058                   TTLs expire.
4059                   Another special keyword <strong class="userinput"><code>unlimited</code></strong>
4060                   means the maximum value of 32-bit unsigned integers
4061                   (0xffffffff), which may not have the same effect as
4062                   0 on machines that support more than 32 bits of
4063                   memory space.
4064                   Any positive values less than 2MB will be ignored reset
4065                   to 2MB.
4066                   In a server with multiple views, the limit applies
4067                   separately to the cache of each view.
4068                   The default is 0.
4069                 </p></dd>
4070 <dt><span class="term"><span><strong class="command">tcp-listen-queue</strong></span></span></dt>
4071 <dd><p>
4072                   The listen queue depth.  The default and minimum is 3.
4073                   If the kernel supports the accept filter "dataready" this
4074                   also controls how
4075                   many TCP connections that will be queued in kernel space
4076                   waiting for
4077                   some data before being passed to accept.  Values less than 3
4078                   will be
4079                   silently raised.
4080                 </p></dd>
4081 </dl></div>
4082 </div>
4083 <div class="sect3" lang="en">
4084 <div class="titlepage"><div><div><h4 class="title">
4085 <a name="id2584173"></a>Periodic Task Intervals</h4></div></div></div>
4086 <div class="variablelist"><dl>
4087 <dt><span class="term"><span><strong class="command">cleaning-interval</strong></span></span></dt>
4088 <dd><p>
4089                   This interval is effectively obsolete.  Previously,
4090                   the server would remove expired resource records
4091                   from the cache every <span><strong class="command">cleaning-interval</strong></span> minutes.
4092                   <acronym class="acronym">BIND</acronym> 9 now manages cache
4093                   memory in a more sophisticated manner and does not
4094                   rely on the periodic cleaning any more.
4095                   Specifying this option therefore has no effect on
4096                   the server's behavior.
4097                 </p></dd>
4098 <dt><span class="term"><span><strong class="command">heartbeat-interval</strong></span></span></dt>
4099 <dd><p>
4100                   The server will perform zone maintenance tasks
4101                   for all zones marked as <span><strong class="command">dialup</strong></span> whenever this
4102                   interval expires. The default is 60 minutes. Reasonable
4103                   values are up
4104                   to 1 day (1440 minutes).  The maximum value is 28 days
4105                   (40320 minutes).
4106                   If set to 0, no zone maintenance for these zones will occur.
4107                 </p></dd>
4108 <dt><span class="term"><span><strong class="command">interface-interval</strong></span></span></dt>
4109 <dd><p>
4110                   The server will scan the network interface list
4111                   every <span><strong class="command">interface-interval</strong></span>
4112                   minutes. The default
4113                   is 60 minutes. The maximum value is 28 days (40320 minutes).
4114                   If set to 0, interface scanning will only occur when
4115                   the configuration file is  loaded. After the scan, the
4116                   server will
4117                   begin listening for queries on any newly discovered
4118                   interfaces (provided they are allowed by the
4119                   <span><strong class="command">listen-on</strong></span> configuration), and
4120                   will
4121                   stop listening on interfaces that have gone away.
4122                 </p></dd>
4123 <dt><span class="term"><span><strong class="command">statistics-interval</strong></span></span></dt>
4124 <dd>
4125 <p>
4126                   Name server statistics will be logged
4127                   every <span><strong class="command">statistics-interval</strong></span>
4128                   minutes. The default is
4129                   60. The maximum value is 28 days (40320 minutes).
4130                   If set to 0, no statistics will be logged.
4131                   </p>
4132 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4133 <h3 class="title">Note</h3>
4134 <p>
4135                     Not yet implemented in
4136                     <acronym class="acronym">BIND</acronym> 9.
4137                   </p>
4138 </div>
4139 </dd>
4140 </dl></div>
4141 </div>
4142 <div class="sect3" lang="en">
4143 <div class="titlepage"><div><div><h4 class="title">
4144 <a name="topology"></a>Topology</h4></div></div></div>
4145 <p>
4146             All other things being equal, when the server chooses a name
4147             server
4148             to query from a list of name servers, it prefers the one that is
4149             topologically closest to itself. The <span><strong class="command">topology</strong></span> statement
4150             takes an <span><strong class="command">address_match_list</strong></span> and
4151             interprets it
4152             in a special way. Each top-level list element is assigned a
4153             distance.
4154             Non-negated elements get a distance based on their position in the
4155             list, where the closer the match is to the start of the list, the
4156             shorter the distance is between it and the server. A negated match
4157             will be assigned the maximum distance from the server. If there
4158             is no match, the address will get a distance which is further than
4159             any non-negated list element, and closer than any negated element.
4160             For example,
4161           </p>
4162 <pre class="programlisting">topology {
4163     10/8;
4164     !1.2.3/24;
4165     { 1.2/16; 3/8; };
4166 };</pre>
4167 <p>
4168             will prefer servers on network 10 the most, followed by hosts
4169             on network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the
4170             exception of hosts on network 1.2.3 (netmask 255.255.255.0), which
4171             is preferred least of all.
4172           </p>
4173 <p>
4174             The default topology is
4175           </p>
4176 <pre class="programlisting">    topology { localhost; localnets; };
4177 </pre>
4178 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4179 <h3 class="title">Note</h3>
4180 <p>
4181               The <span><strong class="command">topology</strong></span> option
4182               is not implemented in <acronym class="acronym">BIND</acronym> 9.
4183             </p>
4184 </div>
4185 </div>
4186 <div class="sect3" lang="en">
4187 <div class="titlepage"><div><div><h4 class="title">
4188 <a name="the_sortlist_statement"></a>The <span><strong class="command">sortlist</strong></span> Statement</h4></div></div></div>
4189 <p>
4190             The response to a DNS query may consist of multiple resource
4191             records (RRs) forming a resource records set (RRset).
4192             The name server will normally return the
4193             RRs within the RRset in an indeterminate order
4194             (but see the <span><strong class="command">rrset-order</strong></span>
4195             statement in <a href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">the section called &#8220;RRset Ordering&#8221;</a>).
4196             The client resolver code should rearrange the RRs as appropriate,
4197             that is, using any addresses on the local net in preference to
4198             other addresses.
4199             However, not all resolvers can do this or are correctly
4200             configured.
4201             When a client is using a local server, the sorting can be performed
4202             in the server, based on the client's address. This only requires
4203             configuring the name servers, not all the clients.
4204           </p>
4205 <p>
4206             The <span><strong class="command">sortlist</strong></span> statement (see below)
4207             takes
4208             an <span><strong class="command">address_match_list</strong></span> and
4209             interprets it even
4210             more specifically than the <span><strong class="command">topology</strong></span>
4211             statement
4212             does (<a href="Bv9ARM.ch06.html#topology" title="Topology">the section called &#8220;Topology&#8221;</a>).
4213             Each top level statement in the <span><strong class="command">sortlist</strong></span> must
4214             itself be an explicit <span><strong class="command">address_match_list</strong></span> with
4215             one or two elements. The first element (which may be an IP
4216             address,
4217             an IP prefix, an ACL name or a nested <span><strong class="command">address_match_list</strong></span>)
4218             of each top level list is checked against the source address of
4219             the query until a match is found.
4220           </p>
4221 <p>
4222             Once the source address of the query has been matched, if
4223             the top level statement contains only one element, the actual
4224             primitive
4225             element that matched the source address is used to select the
4226             address
4227             in the response to move to the beginning of the response. If the
4228             statement is a list of two elements, then the second element is
4229             treated the same as the <span><strong class="command">address_match_list</strong></span> in
4230             a <span><strong class="command">topology</strong></span> statement. Each top
4231             level element
4232             is assigned a distance and the address in the response with the
4233             minimum
4234             distance is moved to the beginning of the response.
4235           </p>
4236 <p>
4237             In the following example, any queries received from any of
4238             the addresses of the host itself will get responses preferring
4239             addresses
4240             on any of the locally connected networks. Next most preferred are
4241             addresses
4242             on the 192.168.1/24 network, and after that either the
4243             192.168.2/24
4244             or
4245             192.168.3/24 network with no preference shown between these two
4246             networks. Queries received from a host on the 192.168.1/24 network
4247             will prefer other addresses on that network to the 192.168.2/24
4248             and
4249             192.168.3/24 networks. Queries received from a host on the
4250             192.168.4/24
4251             or the 192.168.5/24 network will only prefer other addresses on
4252             their directly connected networks.
4253           </p>
4254 <pre class="programlisting">sortlist {
4255     { localhost;                                   // IF   the local host
4256         { localnets;                               // THEN first fit on the
4257             192.168.1/24;                          //   following nets
4258             { 192.168.2/24; 192.168.3/24; }; }; };
4259     { 192.168.1/24;                                // IF   on class C 192.168.1
4260         { 192.168.1/24;                            // THEN use .1, or .2 or .3
4261             { 192.168.2/24; 192.168.3/24; }; }; };
4262     { 192.168.2/24;                                // IF   on class C 192.168.2
4263         { 192.168.2/24;                            // THEN use .2, or .1 or .3
4264             { 192.168.1/24; 192.168.3/24; }; }; };
4265     { 192.168.3/24;                                // IF   on class C 192.168.3
4266         { 192.168.3/24;                            // THEN use .3, or .1 or .2
4267             { 192.168.1/24; 192.168.2/24; }; }; };
4268     { { 192.168.4/24; 192.168.5/24; };             // if .4 or .5, prefer that net
4269     };
4270 };</pre>
4271 <p>
4272             The following example will give reasonable behavior for the
4273             local host and hosts on directly connected networks. It is similar
4274             to the behavior of the address sort in <acronym class="acronym">BIND</acronym> 4.9.x. Responses sent
4275             to queries from the local host will favor any of the directly
4276             connected
4277             networks. Responses sent to queries from any other hosts on a
4278             directly
4279             connected network will prefer addresses on that same network.
4280             Responses
4281             to other queries will not be sorted.
4282           </p>
4283 <pre class="programlisting">sortlist {
4284            { localhost; localnets; };
4285            { localnets; };
4286 };
4287 </pre>
4288 </div>
4289 <div class="sect3" lang="en">
4290 <div class="titlepage"><div><div><h4 class="title">
4291 <a name="rrset_ordering"></a>RRset Ordering</h4></div></div></div>
4292 <p>
4293             When multiple records are returned in an answer it may be
4294             useful to configure the order of the records placed into the
4295             response.
4296             The <span><strong class="command">rrset-order</strong></span> statement permits
4297             configuration
4298             of the ordering of the records in a multiple record response.
4299             See also the <span><strong class="command">sortlist</strong></span> statement,
4300             <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>.
4301           </p>
4302 <p>
4303             An <span><strong class="command">order_spec</strong></span> is defined as
4304             follows:
4305           </p>
4306 <p>
4307             [<span class="optional">class <em class="replaceable"><code>class_name</code></em></span>]
4308             [<span class="optional">type <em class="replaceable"><code>type_name</code></em></span>]
4309             [<span class="optional">name <em class="replaceable"><code>"domain_name"</code></em></span>]
4310             order <em class="replaceable"><code>ordering</code></em>
4311           </p>
4312 <p>
4313             If no class is specified, the default is <span><strong class="command">ANY</strong></span>.
4314             If no type is specified, the default is <span><strong class="command">ANY</strong></span>.
4315             If no name is specified, the default is "<span><strong class="command">*</strong></span>" (asterisk).
4316           </p>
4317 <p>
4318             The legal values for <span><strong class="command">ordering</strong></span> are:
4319           </p>
4320 <div class="informaltable"><table border="1">
4321 <colgroup>
4322 <col>
4323 <col>
4324 </colgroup>
4325 <tbody>
4326 <tr>
4327 <td>
4328                     <p><span><strong class="command">fixed</strong></span></p>
4329                   </td>
4330 <td>
4331                     <p>
4332                       Records are returned in the order they
4333                       are defined in the zone file.
4334                     </p>
4335                   </td>
4336 </tr>
4337 <tr>
4338 <td>
4339                     <p><span><strong class="command">random</strong></span></p>
4340                   </td>
4341 <td>
4342                     <p>
4343                       Records are returned in some random order.
4344                     </p>
4345                   </td>
4346 </tr>
4347 <tr>
4348 <td>
4349                     <p><span><strong class="command">cyclic</strong></span></p>
4350                   </td>
4351 <td>
4352                     <p>
4353                       Records are returned in a cyclic round-robin order.
4354                     </p>
4355                     <p>
4356                       If <acronym class="acronym">BIND</acronym> is configured with the
4357                       "--enable-fixed-rrset" option at compile time, then
4358                       the initial ordering of the RRset will match the
4359                       one specified in the zone file.
4360                     </p>
4361                   </td>
4362 </tr>
4363 </tbody>
4364 </table></div>
4365 <p>
4366             For example:
4367           </p>
4368 <pre class="programlisting">rrset-order {
4369    class IN type A name "host.example.com" order random;
4370    order cyclic;
4371 };
4372 </pre>
4373 <p>
4374             will cause any responses for type A records in class IN that
4375             have "<code class="literal">host.example.com</code>" as a
4376             suffix, to always be returned
4377             in random order. All other records are returned in cyclic order.
4378           </p>
4379 <p>
4380             If multiple <span><strong class="command">rrset-order</strong></span> statements
4381             appear,
4382             they are not combined &#8212; the last one applies.
4383           </p>
4384 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4385 <h3 class="title">Note</h3>
4386 <p>
4387               In this release of <acronym class="acronym">BIND</acronym> 9, the
4388               <span><strong class="command">rrset-order</strong></span> statement does not support
4389               "fixed" ordering by default.  Fixed ordering can be enabled
4390               at compile time by specifying "--enable-fixed-rrset" on
4391               the "configure" command line.
4392             </p>
4393 </div>
4394 </div>
4395 <div class="sect3" lang="en">
4396 <div class="titlepage"><div><div><h4 class="title">
4397 <a name="tuning"></a>Tuning</h4></div></div></div>
4398 <div class="variablelist"><dl>
4399 <dt><span class="term"><span><strong class="command">lame-ttl</strong></span></span></dt>
4400 <dd>
4401 <p>
4402                   Sets the number of seconds to cache a
4403                   lame server indication. 0 disables caching. (This is
4404                   <span class="bold"><strong>NOT</strong></span> recommended.)
4405                   The default is <code class="literal">600</code> (10 minutes) and the
4406                   maximum value is
4407                   <code class="literal">1800</code> (30 minutes).
4408                 </p>
4409 <p>
4410                   Lame-ttl also controls the amount of time DNSSEC
4411                   validation failures are cached.  There is a minimum
4412                   of 30 seconds applied to bad cache entries if the
4413                   lame-ttl is set to less than 30 seconds.
4414                 </p>
4415 </dd>
4416 <dt><span class="term"><span><strong class="command">max-ncache-ttl</strong></span></span></dt>
4417 <dd><p>
4418                   To reduce network traffic and increase performance,
4419                   the server stores negative answers. <span><strong class="command">max-ncache-ttl</strong></span> is
4420                   used to set a maximum retention time for these answers in
4421                   the server
4422                   in seconds. The default
4423                   <span><strong class="command">max-ncache-ttl</strong></span> is <code class="literal">10800</code> seconds (3 hours).
4424                   <span><strong class="command">max-ncache-ttl</strong></span> cannot exceed
4425                   7 days and will
4426                   be silently truncated to 7 days if set to a greater value.
4427                 </p></dd>
4428 <dt><span class="term"><span><strong class="command">max-cache-ttl</strong></span></span></dt>
4429 <dd><p>
4430                   Sets the maximum time for which the server will
4431                   cache ordinary (positive) answers. The default is
4432                   one week (7 days).
4433                   A value of zero may cause all queries to return
4434                   SERVFAIL, because of lost caches of intermediate
4435                   RRsets (such as NS and glue AAAA/A records) in the
4436                   resolution process.
4437                 </p></dd>
4438 <dt><span class="term"><span><strong class="command">min-roots</strong></span></span></dt>
4439 <dd>
4440 <p>
4441                   The minimum number of root servers that
4442                   is required for a request for the root servers to be
4443                   accepted. The default
4444                   is <strong class="userinput"><code>2</code></strong>.
4445                 </p>
4446 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4447 <h3 class="title">Note</h3>
4448 <p>
4449                     Not implemented in <acronym class="acronym">BIND</acronym> 9.
4450                   </p>
4451 </div>
4452 </dd>
4453 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
4454 <dd>
4455 <p>
4456                   Specifies the number of days into the future when
4457                   DNSSEC signatures automatically generated as a
4458                   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
4459                   is a optional second field which specifies how
4460                   long before expiry that the signatures will be
4461                   regenerated.  If not specified, the signatures will
4462                   be regenerated at 1/4 of base interval.  The second
4463                   field is specified in days if the base interval is
4464                   greater than 7 days otherwise it is specified in hours.
4465                   The default base interval is <code class="literal">30</code> days
4466                   giving a re-signing interval of 7 1/2 days.  The maximum
4467                   values are 10 years (3660 days).
4468                 </p>
4469 <p>
4470                   The signature inception time is unconditionally
4471                   set to one hour before the current time to allow
4472                   for a limited amount of clock skew.
4473                 </p>
4474 <p>
4475                   The <span><strong class="command">sig-validity-interval</strong></span>
4476                   should be, at least, several multiples of the SOA
4477                   expire interval to allow for reasonable interaction
4478                   between the various timer and expiry dates.
4479                 </p>
4480 </dd>
4481 <dt><span class="term"><span><strong class="command">sig-signing-nodes</strong></span></span></dt>
4482 <dd><p>
4483                   Specify the maximum number of nodes to be
4484                   examined in each quantum when signing a zone with
4485                   a new DNSKEY. The default is
4486                   <code class="literal">100</code>.
4487                 </p></dd>
4488 <dt><span class="term"><span><strong class="command">sig-signing-signatures</strong></span></span></dt>
4489 <dd><p>
4490                   Specify a threshold number of signatures that
4491                   will terminate processing a quantum when signing
4492                   a zone with a new DNSKEY.  The default is
4493                   <code class="literal">10</code>.
4494                 </p></dd>
4495 <dt><span class="term"><span><strong class="command">sig-signing-type</strong></span></span></dt>
4496 <dd>
4497 <p>
4498                   Specify a private RDATA type to be used when generating
4499                   key signing records.  The default is
4500                   <code class="literal">65535</code>.
4501                 </p>
4502 <p>
4503                   It is expected that this parameter may be removed
4504                   in a future version once there is a standard type.
4505                 </p>
4506 </dd>
4507 <dt>
4508 <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>
4509 </dt>
4510 <dd>
4511 <p>
4512                   These options control the server's behavior on refreshing a
4513                   zone
4514                   (querying for SOA changes) or retrying failed transfers.
4515                   Usually the SOA values for the zone are used, but these
4516                   values
4517                   are set by the master, giving slave server administrators
4518                   little
4519                   control over their contents.
4520                 </p>
4521 <p>
4522                   These options allow the administrator to set a minimum and
4523                   maximum
4524                   refresh and retry time either per-zone, per-view, or
4525                   globally.
4526                   These options are valid for slave and stub zones,
4527                   and clamp the SOA refresh and retry times to the specified
4528                   values.
4529                 </p>
4530 <p>
4531                   The following defaults apply.
4532                   <span><strong class="command">min-refresh-time</strong></span> 300 seconds,
4533                   <span><strong class="command">max-refresh-time</strong></span> 2419200 seconds
4534                   (4 weeks), <span><strong class="command">min-retry-time</strong></span> 500 seconds,
4535                   and <span><strong class="command">max-retry-time</strong></span> 1209600 seconds
4536                   (2 weeks).
4537                 </p>
4538 </dd>
4539 <dt><span class="term"><span><strong class="command">edns-udp-size</strong></span></span></dt>
4540 <dd><p>
4541                   Sets the advertised EDNS UDP buffer size in bytes
4542                   to control the size of packets received.
4543                   Valid values are 512 to 4096 (values outside this range
4544                   will be silently adjusted).  The default value
4545                   is 4096.  The usual reason for setting
4546                   <span><strong class="command">edns-udp-size</strong></span> to a non-default
4547                   value is to get UDP answers to pass through broken
4548                   firewalls that block fragmented packets and/or
4549                   block UDP packets that are greater than 512 bytes.
4550                 </p></dd>
4551 <dt><span class="term"><span><strong class="command">max-udp-size</strong></span></span></dt>
4552 <dd><p>
4553                   Sets the maximum EDNS UDP message size <span><strong class="command">named</strong></span> will
4554                   send in bytes.  Valid values are 512 to 4096 (values outside
4555                   this range will be silently adjusted).  The default
4556                   value is 4096.  The usual reason for setting
4557                   <span><strong class="command">max-udp-size</strong></span> to a non-default value is to get UDP
4558                   answers to pass through broken firewalls that
4559                   block fragmented packets and/or block UDP packets
4560                   that are greater than 512 bytes.
4561                   This is independent of the advertised receive
4562                   buffer (<span><strong class="command">edns-udp-size</strong></span>).
4563                 </p></dd>
4564 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
4565 <dd><p>Specifies
4566                   the file format of zone files (see
4567                   <a href="Bv9ARM.ch06.html#zonefile_format" title="Additional File Formats">the section called &#8220;Additional File Formats&#8221;</a>).
4568                   The default value is <code class="constant">text</code>, which is the
4569                   standard textual representation.  Files in other formats
4570                   than <code class="constant">text</code> are typically expected
4571                   to be generated by the <span><strong class="command">named-compilezone</strong></span> tool.
4572                   Note that when a zone file in a different format than
4573                   <code class="constant">text</code> is loaded, <span><strong class="command">named</strong></span>
4574                   may omit some of the checks which would be performed for a
4575                   file in the <code class="constant">text</code> format.  In particular,
4576                   <span><strong class="command">check-names</strong></span> checks do not apply
4577                   for the <code class="constant">raw</code> format.  This means
4578                   a zone file in the <code class="constant">raw</code> format
4579                   must be generated with the same check level as that
4580                   specified in the <span><strong class="command">named</strong></span> configuration
4581                   file.  This statement sets the
4582                   <span><strong class="command">masterfile-format</strong></span> for all zones,
4583                   but can be overridden on a per-zone or per-view basis
4584                   by including a <span><strong class="command">masterfile-format</strong></span>
4585                   statement within the <span><strong class="command">zone</strong></span> or
4586                   <span><strong class="command">view</strong></span> block in the configuration
4587                   file.
4588                 </p></dd>
4589 <dt>
4590 <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>
4591 </dt>
4592 <dd>
4593 <p>These set the
4594                   initial value (minimum) and maximum number of recursive
4595                   simultaneous clients for any given query
4596                   (&lt;qname,qtype,qclass&gt;) that the server will accept
4597                   before dropping additional clients.  <span><strong class="command">named</strong></span> will attempt to
4598                   self tune this value and changes will be logged.  The
4599                   default values are 10 and 100.
4600                 </p>
4601 <p>
4602                   This value should reflect how many queries come in for
4603                   a given name in the time it takes to resolve that name.
4604                   If the number of queries exceed this value, <span><strong class="command">named</strong></span> will
4605                   assume that it is dealing with a non-responsive zone
4606                   and will drop additional queries.  If it gets a response
4607                   after dropping queries, it will raise the estimate.  The
4608                   estimate will then be lowered in 20 minutes if it has
4609                   remained unchanged.
4610                 </p>
4611 <p>
4612                   If <span><strong class="command">clients-per-query</strong></span> is set to zero,
4613                   then there is no limit on the number of clients per query
4614                   and no queries will be dropped.
4615                 </p>
4616 <p>
4617                   If <span><strong class="command">max-clients-per-query</strong></span> is set to zero,
4618                   then there is no upper bound other than imposed by
4619                   <span><strong class="command">recursive-clients</strong></span>.
4620                 </p>
4621 </dd>
4622 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
4623 <dd><p>
4624                   The delay, in seconds, between sending sets of notify
4625                   messages for a zone.  The default is five (5) seconds.
4626                 </p></dd>
4627 </dl></div>
4628 </div>
4629 <div class="sect3" lang="en">
4630 <div class="titlepage"><div><div><h4 class="title">
4631 <a name="builtin"></a>Built-in server information zones</h4></div></div></div>
4632 <p>
4633             The server provides some helpful diagnostic information
4634             through a number of built-in zones under the
4635             pseudo-top-level-domain <code class="literal">bind</code> in the
4636             <span><strong class="command">CHAOS</strong></span> class.  These zones are part
4637             of a
4638             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
4639             class
4640             <span><strong class="command">CHAOS</strong></span> which is separate from the
4641             default view of
4642             class <span><strong class="command">IN</strong></span>; therefore, any global
4643             server options
4644             such as <span><strong class="command">allow-query</strong></span> do not apply
4645             the these zones.
4646             If you feel the need to disable these zones, use the options
4647             below, or hide the built-in <span><strong class="command">CHAOS</strong></span>
4648             view by
4649             defining an explicit view of class <span><strong class="command">CHAOS</strong></span>
4650             that matches all clients.
4651           </p>
4652 <div class="variablelist"><dl>
4653 <dt><span class="term"><span><strong class="command">version</strong></span></span></dt>
4654 <dd><p>
4655                   The version the server should report
4656                   via a query of the name <code class="literal">version.bind</code>
4657                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
4658                   The default is the real version number of this server.
4659                   Specifying <span><strong class="command">version none</strong></span>
4660                   disables processing of the queries.
4661                 </p></dd>
4662 <dt><span class="term"><span><strong class="command">hostname</strong></span></span></dt>
4663 <dd><p>
4664                   The hostname the server should report via a query of
4665                   the name <code class="filename">hostname.bind</code>
4666                   with type <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
4667                   This defaults to the hostname of the machine hosting the
4668                   name server as
4669                   found by the gethostname() function.  The primary purpose of such queries
4670                   is to
4671                   identify which of a group of anycast servers is actually
4672                   answering your queries.  Specifying <span><strong class="command">hostname none;</strong></span>
4673                   disables processing of the queries.
4674                 </p></dd>
4675 <dt><span class="term"><span><strong class="command">server-id</strong></span></span></dt>
4676 <dd><p>
4677                   The ID the server should report when receiving a Name
4678                   Server Identifier (NSID) query, or a query of the name
4679                   <code class="filename">ID.SERVER</code> with type
4680                   <span><strong class="command">TXT</strong></span>, class <span><strong class="command">CHAOS</strong></span>.
4681                   The primary purpose of such queries is to
4682                   identify which of a group of anycast servers is actually
4683                   answering your queries.  Specifying <span><strong class="command">server-id none;</strong></span>
4684                   disables processing of the queries.
4685                   Specifying <span><strong class="command">server-id hostname;</strong></span> will cause <span><strong class="command">named</strong></span> to
4686                   use the hostname as found by the gethostname() function.
4687                   The default <span><strong class="command">server-id</strong></span> is <span><strong class="command">none</strong></span>.
4688                 </p></dd>
4689 </dl></div>
4690 </div>
4691 <div class="sect3" lang="en">
4692 <div class="titlepage"><div><div><h4 class="title">
4693 <a name="empty"></a>Built-in Empty Zones</h4></div></div></div>
4694 <p>
4695             Named has some built-in empty zones (SOA and NS records only).
4696             These are for zones that should normally be answered locally
4697             and which queries should not be sent to the Internet's root
4698             servers.  The official servers which cover these namespaces
4699             return NXDOMAIN responses to these queries.  In particular,
4700             these cover the reverse namespace for addresses from RFC 1918 and
4701             RFC 3330.  They also include the reverse namespace for IPv6 local
4702             address (locally assigned), IPv6 link local addresses, the IPv6
4703             loopback address and the IPv6 unknown address.
4704           </p>
4705 <p>
4706             Named will attempt to determine if a built-in zone already exists
4707             or is active (covered by a forward-only forwarding declaration)
4708             and will not create a empty zone in that case.
4709           </p>
4710 <p>
4711             The current list of empty zones is:
4712             </p>
4713 <div class="itemizedlist"><ul type="disc">
4714 <li>0.IN-ADDR.ARPA</li>
4715 <li>127.IN-ADDR.ARPA</li>
4716 <li>254.169.IN-ADDR.ARPA</li>
4717 <li>2.0.192.IN-ADDR.ARPA</li>
4718 <li>100.51.198.IN-ADDR.ARPA</li>
4719 <li>113.0.203.IN-ADDR.ARPA</li>
4720 <li>255.255.255.255.IN-ADDR.ARPA</li>
4721 <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>
4722 <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>
4723 <li>8.B.D.0.1.0.0.2.IP6.ARPA</li>
4724 <li>D.F.IP6.ARPA</li>
4725 <li>8.E.F.IP6.ARPA</li>
4726 <li>9.E.F.IP6.ARPA</li>
4727 <li>A.E.F.IP6.ARPA</li>
4728 <li>B.E.F.IP6.ARPA</li>
4729 </ul></div>
4730 <p>
4731           </p>
4732 <p>
4733             Empty zones are settable at the view level and only apply to
4734             views of class IN.  Disabled empty zones are only inherited
4735             from options if there are no disabled empty zones specified
4736             at the view level.  To override the options list of disabled
4737             zones, you can disable the root zone at the view level, for example:
4738 </p>
4739 <pre class="programlisting">
4740             disable-empty-zone ".";
4741 </pre>
4742 <p>
4743           </p>
4744 <p>
4745             If you are using the address ranges covered here, you should
4746             already have reverse zones covering the addresses you use.
4747             In practice this appears to not be the case with many queries
4748             being made to the infrastructure servers for names in these
4749             spaces.  So many in fact that sacrificial servers were needed
4750             to be deployed to channel the query load away from the
4751             infrastructure servers.
4752           </p>
4753 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
4754 <h3 class="title">Note</h3>
4755             The real parent servers for these zones should disable all
4756             empty zone under the parent zone they serve.  For the real
4757             root servers, this is all built-in empty zones.  This will
4758             enable them to return referrals to deeper in the tree.
4759           </div>
4760 <div class="variablelist"><dl>
4761 <dt><span class="term"><span><strong class="command">empty-server</strong></span></span></dt>
4762 <dd><p>
4763                   Specify what server name will appear in the returned
4764                   SOA record for empty zones.  If none is specified, then
4765                   the zone's name will be used.
4766                 </p></dd>
4767 <dt><span class="term"><span><strong class="command">empty-contact</strong></span></span></dt>
4768 <dd><p>
4769                   Specify what contact name will appear in the returned
4770                   SOA record for empty zones.  If none is specified, then
4771                   "." will be used.
4772                 </p></dd>
4773 <dt><span class="term"><span><strong class="command">empty-zones-enable</strong></span></span></dt>
4774 <dd><p>
4775                   Enable or disable all empty zones.  By default, they
4776                   are enabled.
4777                 </p></dd>
4778 <dt><span class="term"><span><strong class="command">disable-empty-zone</strong></span></span></dt>
4779 <dd><p>
4780                   Disable individual empty zones.  By default, none are
4781                   disabled.  This option can be specified multiple times.
4782                 </p></dd>
4783 </dl></div>
4784 </div>
4785 <div class="sect3" lang="en">
4786 <div class="titlepage"><div><div><h4 class="title">
4787 <a name="acache"></a>Additional Section Caching</h4></div></div></div>
4788 <p>
4789             The additional section cache, also called <span><strong class="command">acache</strong></span>,
4790             is an internal cache to improve the response performance of BIND 9.
4791             When additional section caching is enabled, BIND 9 will
4792             cache an internal short-cut to the additional section content for
4793             each answer RR.
4794             Note that <span><strong class="command">acache</strong></span> is an internal caching
4795             mechanism of BIND 9, and is not related to the DNS caching
4796             server function.
4797           </p>
4798 <p>
4799             Additional section caching does not change the
4800             response content (except the RRsets ordering of the additional
4801             section, see below), but can improve the response performance
4802             significantly.
4803             It is particularly effective when BIND 9 acts as an authoritative
4804             server for a zone that has many delegations with many glue RRs.
4805           </p>
4806 <p>
4807             In order to obtain the maximum performance improvement
4808             from additional section caching, setting
4809             <span><strong class="command">additional-from-cache</strong></span>
4810             to <span><strong class="command">no</strong></span> is recommended, since the current
4811             implementation of <span><strong class="command">acache</strong></span>
4812             does not short-cut of additional section information from the
4813             DNS cache data.
4814           </p>
4815 <p>
4816             One obvious disadvantage of <span><strong class="command">acache</strong></span> is
4817             that it requires much more
4818             memory for the internal cached data.
4819             Thus, if the response performance does not matter and memory
4820             consumption is much more critical, the
4821             <span><strong class="command">acache</strong></span> mechanism can be
4822             disabled by setting <span><strong class="command">acache-enable</strong></span> to
4823             <span><strong class="command">no</strong></span>.
4824             It is also possible to specify the upper limit of memory
4825             consumption
4826             for acache by using <span><strong class="command">max-acache-size</strong></span>.
4827           </p>
4828 <p>
4829             Additional section caching also has a minor effect on the
4830             RRset ordering in the additional section.
4831             Without <span><strong class="command">acache</strong></span>,
4832             <span><strong class="command">cyclic</strong></span> order is effective for the additional
4833             section as well as the answer and authority sections.
4834             However, additional section caching fixes the ordering when it
4835             first caches an RRset for the additional section, and the same
4836             ordering will be kept in succeeding responses, regardless of the
4837             setting of <span><strong class="command">rrset-order</strong></span>.
4838             The effect of this should be minor, however, since an
4839             RRset in the additional section
4840             typically only contains a small number of RRs (and in many cases
4841             it only contains a single RR), in which case the
4842             ordering does not matter much.
4843           </p>
4844 <p>
4845             The following is a summary of options related to
4846             <span><strong class="command">acache</strong></span>.
4847           </p>
4848 <div class="variablelist"><dl>
4849 <dt><span class="term"><span><strong class="command">acache-enable</strong></span></span></dt>
4850 <dd><p>
4851                   If <span><strong class="command">yes</strong></span>, additional section caching is
4852                   enabled.  The default value is <span><strong class="command">no</strong></span>.
4853                 </p></dd>
4854 <dt><span class="term"><span><strong class="command">acache-cleaning-interval</strong></span></span></dt>
4855 <dd><p>
4856                   The server will remove stale cache entries, based on an LRU
4857                   based
4858                   algorithm, every <span><strong class="command">acache-cleaning-interval</strong></span> minutes.
4859                   The default is 60 minutes.
4860                   If set to 0, no periodic cleaning will occur.
4861                 </p></dd>
4862 <dt><span class="term"><span><strong class="command">max-acache-size</strong></span></span></dt>
4863 <dd><p>
4864                   The maximum amount of memory in bytes to use for the server's acache.
4865                   When the amount of data in the acache reaches this limit,
4866                   the server
4867                   will clean more aggressively so that the limit is not
4868                   exceeded.
4869                   In a server with multiple views, the limit applies
4870                   separately to the
4871                   acache of each view.
4872                   The default is <code class="literal">16M</code>.
4873                 </p></dd>
4874 </dl></div>
4875 </div>
4876 </div>
4877 <div class="sect2" lang="en">
4878 <div class="titlepage"><div><div><h3 class="title">
4879 <a name="server_statement_grammar"></a><span><strong class="command">server</strong></span> Statement Grammar</h3></div></div></div>
4880 <pre class="programlisting"><span><strong class="command">server</strong></span> <em class="replaceable"><code>ip_addr[/prefixlen]</code></em> {
4881     [<span class="optional"> bogus <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4882     [<span class="optional"> provide-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4883     [<span class="optional"> request-ixfr <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4884     [<span class="optional"> edns <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
4885     [<span class="optional"> edns-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
4886     [<span class="optional"> max-udp-size <em class="replaceable"><code>number</code></em> ; </span>]
4887     [<span class="optional"> transfers <em class="replaceable"><code>number</code></em> ; </span>]
4888     [<span class="optional"> transfer-format <em class="replaceable"><code>( one-answer | many-answers )</code></em> ; ]</span>]
4889     [<span class="optional"> keys <em class="replaceable"><code>{ string ; [<span class="optional"> string ; [<span class="optional">...</span>]</span>] }</code></em> ; </span>]
4890     [<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>]
4891     [<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>]
4892     [<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>]
4893     [<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>]
4894     [<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>]
4895     [<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>]
4896     [<span class="optional"> use-queryport-pool <em class="replaceable"><code>yes_or_no</code></em>; </span>]
4897     [<span class="optional"> queryport-pool-ports <em class="replaceable"><code>number</code></em>; </span>]
4898     [<span class="optional"> queryport-pool-updateinterval <em class="replaceable"><code>number</code></em>; </span>]
4899 };
4900 </pre>
4901 </div>
4902 <div class="sect2" lang="en">
4903 <div class="titlepage"><div><div><h3 class="title">
4904 <a name="server_statement_definition_and_usage"></a><span><strong class="command">server</strong></span> Statement Definition and
4905             Usage</h3></div></div></div>
4906 <p>
4907             The <span><strong class="command">server</strong></span> statement defines
4908             characteristics
4909             to be associated with a remote name server.  If a prefix length is
4910             specified, then a range of servers is covered.  Only the most
4911             specific
4912             server clause applies regardless of the order in
4913             <code class="filename">named.conf</code>.
4914           </p>
4915 <p>
4916             The <span><strong class="command">server</strong></span> statement can occur at
4917             the top level of the
4918             configuration file or inside a <span><strong class="command">view</strong></span>
4919             statement.
4920             If a <span><strong class="command">view</strong></span> statement contains
4921             one or more <span><strong class="command">server</strong></span> statements, only
4922             those
4923             apply to the view and any top-level ones are ignored.
4924             If a view contains no <span><strong class="command">server</strong></span>
4925             statements,
4926             any top-level <span><strong class="command">server</strong></span> statements are
4927             used as
4928             defaults.
4929           </p>
4930 <p>
4931             If you discover that a remote server is giving out bad data,
4932             marking it as bogus will prevent further queries to it. The
4933             default
4934             value of <span><strong class="command">bogus</strong></span> is <span><strong class="command">no</strong></span>.
4935           </p>
4936 <p>
4937             The <span><strong class="command">provide-ixfr</strong></span> clause determines
4938             whether
4939             the local server, acting as master, will respond with an
4940             incremental
4941             zone transfer when the given remote server, a slave, requests it.
4942             If set to <span><strong class="command">yes</strong></span>, incremental transfer
4943             will be provided
4944             whenever possible. If set to <span><strong class="command">no</strong></span>,
4945             all transfers
4946             to the remote server will be non-incremental. If not set, the
4947             value
4948             of the <span><strong class="command">provide-ixfr</strong></span> option in the
4949             view or
4950             global options block is used as a default.
4951           </p>
4952 <p>
4953             The <span><strong class="command">request-ixfr</strong></span> clause determines
4954             whether
4955             the local server, acting as a slave, will request incremental zone
4956             transfers from the given remote server, a master. If not set, the
4957             value of the <span><strong class="command">request-ixfr</strong></span> option in
4958             the view or
4959             global options block is used as a default.
4960           </p>
4961 <p>
4962             IXFR requests to servers that do not support IXFR will
4963             automatically
4964             fall back to AXFR.  Therefore, there is no need to manually list
4965             which servers support IXFR and which ones do not; the global
4966             default
4967             of <span><strong class="command">yes</strong></span> should always work.
4968             The purpose of the <span><strong class="command">provide-ixfr</strong></span> and
4969             <span><strong class="command">request-ixfr</strong></span> clauses is
4970             to make it possible to disable the use of IXFR even when both
4971             master
4972             and slave claim to support it, for example if one of the servers
4973             is buggy and crashes or corrupts data when IXFR is used.
4974           </p>
4975 <p>
4976             The <span><strong class="command">edns</strong></span> clause determines whether
4977             the local server will attempt to use EDNS when communicating
4978             with the remote server.  The default is <span><strong class="command">yes</strong></span>.
4979           </p>
4980 <p>
4981             The <span><strong class="command">edns-udp-size</strong></span> option sets the EDNS UDP size
4982             that is advertised by <span><strong class="command">named</strong></span> when querying the remote server.
4983             Valid values are 512 to 4096 bytes (values outside this range will be
4984             silently adjusted).  This option is useful when you wish to
4985             advertises a different value to this server than the value you
4986             advertise globally, for example, when there is a firewall at the
4987             remote site that is blocking large replies.
4988           </p>
4989 <p>
4990             The <span><strong class="command">max-udp-size</strong></span> option sets the
4991             maximum EDNS UDP message size <span><strong class="command">named</strong></span> will send.  Valid
4992             values are 512 to 4096 bytes (values outside this range will
4993             be silently adjusted).  This option is useful when you
4994             know that there is a firewall that is blocking large
4995             replies from <span><strong class="command">named</strong></span>.
4996           </p>
4997 <p>
4998             The server supports two zone transfer methods. The first, <span><strong class="command">one-answer</strong></span>,
4999             uses one DNS message per resource record transferred. <span><strong class="command">many-answers</strong></span> packs
5000             as many resource records as possible into a message. <span><strong class="command">many-answers</strong></span> is
5001             more efficient, but is only known to be understood by <acronym class="acronym">BIND</acronym> 9, <acronym class="acronym">BIND</acronym>
5002             8.x, and patched versions of <acronym class="acronym">BIND</acronym>
5003             4.9.5. You can specify which method
5004             to use for a server with the <span><strong class="command">transfer-format</strong></span> option.
5005             If <span><strong class="command">transfer-format</strong></span> is not
5006             specified, the <span><strong class="command">transfer-format</strong></span>
5007             specified
5008             by the <span><strong class="command">options</strong></span> statement will be
5009             used.
5010           </p>
5011 <p><span><strong class="command">transfers</strong></span>
5012             is used to limit the number of concurrent inbound zone
5013             transfers from the specified server. If no
5014             <span><strong class="command">transfers</strong></span> clause is specified, the
5015             limit is set according to the
5016             <span><strong class="command">transfers-per-ns</strong></span> option.
5017           </p>
5018 <p>
5019             The <span><strong class="command">keys</strong></span> clause identifies a
5020             <span><strong class="command">key_id</strong></span> defined by the <span><strong class="command">key</strong></span> statement,
5021             to be used for transaction security (TSIG, <a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called &#8220;TSIG&#8221;</a>)
5022             when talking to the remote server.
5023             When a request is sent to the remote server, a request signature
5024             will be generated using the key specified here and appended to the
5025             message. A request originating from the remote server is not
5026             required
5027             to be signed by this key.
5028           </p>
5029 <p>
5030             Although the grammar of the <span><strong class="command">keys</strong></span>
5031             clause
5032             allows for multiple keys, only a single key per server is
5033             currently
5034             supported.
5035           </p>
5036 <p>
5037             The <span><strong class="command">transfer-source</strong></span> and
5038             <span><strong class="command">transfer-source-v6</strong></span> clauses specify
5039             the IPv4 and IPv6 source
5040             address to be used for zone transfer with the remote server,
5041             respectively.
5042             For an IPv4 remote server, only <span><strong class="command">transfer-source</strong></span> can
5043             be specified.
5044             Similarly, for an IPv6 remote server, only
5045             <span><strong class="command">transfer-source-v6</strong></span> can be
5046             specified.
5047             For more details, see the description of
5048             <span><strong class="command">transfer-source</strong></span> and
5049             <span><strong class="command">transfer-source-v6</strong></span> in
5050             <a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called &#8220;Zone Transfers&#8221;</a>.
5051           </p>
5052 <p>
5053             The <span><strong class="command">notify-source</strong></span> and
5054             <span><strong class="command">notify-source-v6</strong></span> clauses specify the
5055             IPv4 and IPv6 source address to be used for notify
5056             messages sent to remote servers, respectively.  For an
5057             IPv4 remote server, only <span><strong class="command">notify-source</strong></span>
5058             can be specified.  Similarly, for an IPv6 remote server,
5059             only <span><strong class="command">notify-source-v6</strong></span> can be specified.
5060           </p>
5061 <p>
5062             The <span><strong class="command">query-source</strong></span> and
5063             <span><strong class="command">query-source-v6</strong></span> clauses specify the
5064             IPv4 and IPv6 source address to be used for queries
5065             sent to remote servers, respectively.  For an IPv4
5066             remote server, only <span><strong class="command">query-source</strong></span> can
5067             be specified.  Similarly, for an IPv6 remote server,
5068             only <span><strong class="command">query-source-v6</strong></span> can be specified.
5069           </p>
5070 </div>
5071 <div class="sect2" lang="en">
5072 <div class="titlepage"><div><div><h3 class="title">
5073 <a name="statschannels"></a><span><strong class="command">statistics-channels</strong></span> Statement Grammar</h3></div></div></div>
5074 <pre class="programlisting"><span><strong class="command">statistics-channels</strong></span> {
5075    [ inet ( ip_addr | * ) [ port ip_port ] [allow { <em class="replaceable"><code> address_match_list </code></em> } ]; ]
5076    [ inet ...; ]
5077 };
5078 </pre>
5079 </div>
5080 <div class="sect2" lang="en">
5081 <div class="titlepage"><div><div><h3 class="title">
5082 <a name="id2586907"></a><span><strong class="command">statistics-channels</strong></span> Statement Definition and
5083             Usage</h3></div></div></div>
5084 <p>
5085           The <span><strong class="command">statistics-channels</strong></span> statement
5086           declares communication channels to be used by system
5087           administrators to get access to statistics information of
5088           the name server.
5089         </p>
5090 <p>
5091           This statement intends to be flexible to support multiple
5092           communication protocols in the future, but currently only
5093           HTTP access is supported.
5094           It requires that BIND 9 be compiled with libxml2;
5095           the <span><strong class="command">statistics-channels</strong></span> statement is
5096           still accepted even if it is built without the library,
5097           but any HTTP access will fail with an error.
5098         </p>
5099 <p>
5100           An <span><strong class="command">inet</strong></span> control channel is a TCP socket
5101           listening at the specified <span><strong class="command">ip_port</strong></span> on the
5102           specified <span><strong class="command">ip_addr</strong></span>, which can be an IPv4 or IPv6
5103           address.  An <span><strong class="command">ip_addr</strong></span> of <code class="literal">*</code> (asterisk) is
5104           interpreted as the IPv4 wildcard address; connections will be
5105           accepted on any of the system's IPv4 addresses.
5106           To listen on the IPv6 wildcard address,
5107           use an <span><strong class="command">ip_addr</strong></span> of <code class="literal">::</code>.
5108         </p>
5109 <p>
5110           If no port is specified, port 80 is used for HTTP channels.
5111           The asterisk "<code class="literal">*</code>" cannot be used for
5112           <span><strong class="command">ip_port</strong></span>.
5113         </p>
5114 <p>
5115           The attempt of opening a statistics channel is
5116           restricted by the optional <span><strong class="command">allow</strong></span> clause.
5117           Connections to the statistics channel are permitted based on the
5118           <span><strong class="command">address_match_list</strong></span>.
5119           If no <span><strong class="command">allow</strong></span> clause is present,
5120           <span><strong class="command">named</strong></span> accepts connection
5121           attempts from any address; since the statistics may
5122           contain sensitive internal information, it is highly
5123           recommended to restrict the source of connection requests
5124           appropriately.
5125         </p>
5126 <p>
5127           If no <span><strong class="command">statistics-channels</strong></span> statement is present,
5128           <span><strong class="command">named</strong></span> will not open any communication channels.
5129         </p>
5130 </div>
5131 <div class="sect2" lang="en">
5132 <div class="titlepage"><div><div><h3 class="title">
5133 <a name="id2587062"></a><span><strong class="command">trusted-keys</strong></span> Statement Grammar</h3></div></div></div>
5134 <pre class="programlisting"><span><strong class="command">trusted-keys</strong></span> {
5135     <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> ;
5136     [<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>]
5137 };
5138 </pre>
5139 </div>
5140 <div class="sect2" lang="en">
5141 <div class="titlepage"><div><div><h3 class="title">
5142 <a name="id2587113"></a><span><strong class="command">trusted-keys</strong></span> Statement Definition
5143             and Usage</h3></div></div></div>
5144 <p>
5145             The <span><strong class="command">trusted-keys</strong></span> statement defines
5146             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
5147             public key for a non-authoritative zone is known, but
5148             cannot be securely obtained through DNS, either because
5149             it is the DNS root zone or because its parent zone is
5150             unsigned.  Once a key has been configured as a trusted
5151             key, it is treated as if it had been validated and
5152             proven secure. The resolver attempts DNSSEC validation
5153             on all DNS data in subdomains of a security root.
5154           </p>
5155 <p>
5156             All keys (and corresponding zones) listed in
5157             <span><strong class="command">trusted-keys</strong></span> are deemed to exist regardless
5158             of what parent zones say.  Similarly for all keys listed in
5159             <span><strong class="command">trusted-keys</strong></span> only those keys are
5160             used to validate the DNSKEY RRset.  The parent's DS RRset
5161             will not be used.
5162           </p>
5163 <p>
5164             The <span><strong class="command">trusted-keys</strong></span> statement can contain
5165             multiple key entries, each consisting of the key's
5166             domain name, flags, protocol, algorithm, and the Base-64
5167             representation of the key data.
5168             Spaces, tabs, newlines and carriage returns are ignored
5169             in the key data, so the configuration may be split up into
5170             multiple lines.
5171           </p>
5172 </div>
5173 <div class="sect2" lang="en">
5174 <div class="titlepage"><div><div><h3 class="title">
5175 <a name="view_statement_grammar"></a><span><strong class="command">view</strong></span> Statement Grammar</h3></div></div></div>
5176 <pre class="programlisting"><span><strong class="command">view</strong></span> <em class="replaceable"><code>view_name</code></em>
5177       [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
5178       match-clients { <em class="replaceable"><code>address_match_list</code></em> };
5179       match-destinations { <em class="replaceable"><code>address_match_list</code></em> };
5180       match-recursive-only <em class="replaceable"><code>yes_or_no</code></em> ;
5181       [<span class="optional"> <em class="replaceable"><code>view_option</code></em>; ...</span>]
5182       [<span class="optional"> <em class="replaceable"><code>zone_statement</code></em>; ...</span>]
5183 };
5184 </pre>
5185 </div>
5186 <div class="sect2" lang="en">
5187 <div class="titlepage"><div><div><h3 class="title">
5188 <a name="id2587195"></a><span><strong class="command">view</strong></span> Statement Definition and Usage</h3></div></div></div>
5189 <p>
5190             The <span><strong class="command">view</strong></span> statement is a powerful
5191             feature
5192             of <acronym class="acronym">BIND</acronym> 9 that lets a name server
5193             answer a DNS query differently
5194             depending on who is asking. It is particularly useful for
5195             implementing
5196             split DNS setups without having to run multiple servers.
5197           </p>
5198 <p>
5199             Each <span><strong class="command">view</strong></span> statement defines a view
5200             of the
5201             DNS namespace that will be seen by a subset of clients.  A client
5202             matches
5203             a view if its source IP address matches the
5204             <code class="varname">address_match_list</code> of the view's
5205             <span><strong class="command">match-clients</strong></span> clause and its
5206             destination IP address matches
5207             the <code class="varname">address_match_list</code> of the
5208             view's
5209             <span><strong class="command">match-destinations</strong></span> clause.  If not
5210             specified, both
5211             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
5212             default to matching all addresses.  In addition to checking IP
5213             addresses
5214             <span><strong class="command">match-clients</strong></span> and <span><strong class="command">match-destinations</strong></span>
5215             can also take <span><strong class="command">keys</strong></span> which provide an
5216             mechanism for the
5217             client to select the view.  A view can also be specified
5218             as <span><strong class="command">match-recursive-only</strong></span>, which
5219             means that only recursive
5220             requests from matching clients will match that view.
5221             The order of the <span><strong class="command">view</strong></span> statements is
5222             significant &#8212;
5223             a client request will be resolved in the context of the first
5224             <span><strong class="command">view</strong></span> that it matches.
5225           </p>
5226 <p>
5227             Zones defined within a <span><strong class="command">view</strong></span>
5228             statement will
5229             only be accessible to clients that match the <span><strong class="command">view</strong></span>.
5230             By defining a zone of the same name in multiple views, different
5231             zone data can be given to different clients, for example,
5232             "internal"
5233             and "external" clients in a split DNS setup.
5234           </p>
5235 <p>
5236             Many of the options given in the <span><strong class="command">options</strong></span> statement
5237             can also be used within a <span><strong class="command">view</strong></span>
5238             statement, and then
5239             apply only when resolving queries with that view.  When no
5240             view-specific
5241             value is given, the value in the <span><strong class="command">options</strong></span> statement
5242             is used as a default.  Also, zone options can have default values
5243             specified
5244             in the <span><strong class="command">view</strong></span> statement; these
5245             view-specific defaults
5246             take precedence over those in the <span><strong class="command">options</strong></span> statement.
5247           </p>
5248 <p>
5249             Views are class specific.  If no class is given, class IN
5250             is assumed.  Note that all non-IN views must contain a hint zone,
5251             since only the IN class has compiled-in default hints.
5252           </p>
5253 <p>
5254             If there are no <span><strong class="command">view</strong></span> statements in
5255             the config
5256             file, a default view that matches any client is automatically
5257             created
5258             in class IN. Any <span><strong class="command">zone</strong></span> statements
5259             specified on
5260             the top level of the configuration file are considered to be part
5261             of
5262             this default view, and the <span><strong class="command">options</strong></span>
5263             statement will
5264             apply to the default view. If any explicit <span><strong class="command">view</strong></span>
5265             statements are present, all <span><strong class="command">zone</strong></span>
5266             statements must
5267             occur inside <span><strong class="command">view</strong></span> statements.
5268           </p>
5269 <p>
5270             Here is an example of a typical split DNS setup implemented
5271             using <span><strong class="command">view</strong></span> statements:
5272           </p>
5273 <pre class="programlisting">view "internal" {
5274       // This should match our internal networks.
5275       match-clients { 10.0.0.0/8; };
5276
5277       // Provide recursive service to internal clients only.
5278       recursion yes;
5279
5280       // Provide a complete view of the example.com zone
5281       // including addresses of internal hosts.
5282       zone "example.com" {
5283             type master;
5284             file "example-internal.db";
5285       };
5286 };
5287
5288 view "external" {
5289       // Match all clients not matched by the previous view.
5290       match-clients { any; };
5291
5292       // Refuse recursive service to external clients.
5293       recursion no;
5294
5295       // Provide a restricted view of the example.com zone
5296       // containing only publicly accessible hosts.
5297       zone "example.com" {
5298            type master;
5299            file "example-external.db";
5300       };
5301 };
5302 </pre>
5303 </div>
5304 <div class="sect2" lang="en">
5305 <div class="titlepage"><div><div><h3 class="title">
5306 <a name="zone_statement_grammar"></a><span><strong class="command">zone</strong></span>
5307             Statement Grammar</h3></div></div></div>
5308 <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>] {
5309     type master;
5310     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5311     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5312     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5313     [<span class="optional"> allow-update { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5314     [<span class="optional"> update-policy { <em class="replaceable"><code>update_policy_rule</code></em> [<span class="optional">...</span>] }; </span>]
5315     [<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>]
5316     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
5317     [<span class="optional"> check-mx (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
5318     [<span class="optional"> check-wildcard <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5319     [<span class="optional"> check-integrity <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5320     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
5321     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
5322     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
5323     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
5324     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
5325     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
5326     [<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>]
5327     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
5328     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5329     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
5330     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5331     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
5332     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
5333     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
5334     [<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>]
5335     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
5336     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5337     [<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>]
5338     [<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>]
5339     [<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>]
5340     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5341     [<span class="optional"> sig-validity-interval <em class="replaceable"><code>number</code></em> [<span class="optional"><em class="replaceable"><code>number</code></em></span>] ; </span>]
5342     [<span class="optional"> sig-signing-nodes <em class="replaceable"><code>number</code></em> ; </span>]
5343     [<span class="optional"> sig-signing-signatures <em class="replaceable"><code>number</code></em> ; </span>]
5344     [<span class="optional"> sig-signing-type <em class="replaceable"><code>number</code></em> ; </span>]
5345     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
5346     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
5347     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
5348     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
5349     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
5350     [<span class="optional"> key-directory <em class="replaceable"><code>path_name</code></em>; </span>]
5351     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5352 };
5353
5354 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
5355     type slave;
5356     [<span class="optional"> allow-notify { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5357     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5358     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5359     [<span class="optional"> allow-transfer { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5360     [<span class="optional"> allow-update-forwarding { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5361     [<span class="optional"> update-check-ksk <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5362     [<span class="optional"> try-tcp-refresh <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5363     [<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>]
5364     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
5365     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
5366     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
5367     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
5368     [<span class="optional"> journal <em class="replaceable"><code>string</code></em> ; </span>]
5369     [<span class="optional"> max-journal-size <em class="replaceable"><code>size_spec</code></em>; </span>]
5370     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
5371     [<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>]
5372     [<span class="optional"> ixfr-base <em class="replaceable"><code>string</code></em> ; </span>]
5373     [<span class="optional"> ixfr-from-differences <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5374     [<span class="optional"> ixfr-tmp-file <em class="replaceable"><code>string</code></em> ; </span>]
5375     [<span class="optional"> maintain-ixfr-base <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5376     [<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>]
5377     [<span class="optional"> max-ixfr-log-size <em class="replaceable"><code>number</code></em> ; </span>]
5378     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
5379     [<span class="optional"> max-transfer-idle-out <em class="replaceable"><code>number</code></em> ; </span>]
5380     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
5381     [<span class="optional"> max-transfer-time-out <em class="replaceable"><code>number</code></em> ; </span>]
5382     [<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>]
5383     [<span class="optional"> notify-delay <em class="replaceable"><code>seconds</code></em> ; </span>]
5384     [<span class="optional"> notify-to-soa <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5385     [<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>]
5386     [<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>]
5387     [<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>]
5388     [<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>]
5389     [<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>]
5390     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5391     [<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>]
5392     [<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>]
5393     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5394     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
5395     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
5396     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
5397     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
5398     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
5399     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5400     [<span class="optional"> zero-no-soa-ttl <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5401 };
5402
5403 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
5404     type hint;
5405     file <em class="replaceable"><code>string</code></em> ;
5406     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5407     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; // Not Implemented. </span>]
5408 };
5409
5410 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
5411     type stub;
5412     [<span class="optional"> allow-query { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5413     [<span class="optional"> allow-query-on { <em class="replaceable"><code>address_match_list</code></em> }; </span>]
5414     [<span class="optional"> check-names (<code class="constant">warn</code>|<code class="constant">fail</code>|<code class="constant">ignore</code>) ; </span>]
5415     [<span class="optional"> dialup <em class="replaceable"><code>dialup_option</code></em> ; </span>]
5416     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5417     [<span class="optional"> file <em class="replaceable"><code>string</code></em> ; </span>]
5418     [<span class="optional"> masterfile-format (<code class="constant">text</code>|<code class="constant">raw</code>) ; </span>]
5419     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
5420     [<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>]
5421     [<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>]
5422     [<span class="optional"> max-transfer-idle-in <em class="replaceable"><code>number</code></em> ; </span>]
5423     [<span class="optional"> max-transfer-time-in <em class="replaceable"><code>number</code></em> ; </span>]
5424     [<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>]
5425     [<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>]
5426     [<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>]
5427     [<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>]
5428     [<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>]
5429     [<span class="optional"> use-alt-transfer-source <em class="replaceable"><code>yes_or_no</code></em>; </span>]
5430     [<span class="optional"> zone-statistics <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5431     [<span class="optional"> database <em class="replaceable"><code>string</code></em> ; </span>]
5432     [<span class="optional"> min-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
5433     [<span class="optional"> max-refresh-time <em class="replaceable"><code>number</code></em> ; </span>]
5434     [<span class="optional"> min-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
5435     [<span class="optional"> max-retry-time <em class="replaceable"><code>number</code></em> ; </span>]
5436     [<span class="optional"> multi-master <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5437 };
5438
5439 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
5440     type forward;
5441     [<span class="optional"> forward (<code class="constant">only</code>|<code class="constant">first</code>) ; </span>]
5442     [<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>]
5443     [<span class="optional"> delegation-only <em class="replaceable"><code>yes_or_no</code></em> ; </span>]
5444 };
5445
5446 zone <em class="replaceable"><code>zone_name</code></em> [<span class="optional"><em class="replaceable"><code>class</code></em></span>] {
5447     type delegation-only;
5448 };
5449
5450 </pre>
5451 </div>
5452 <div class="sect2" lang="en">
5453 <div class="titlepage"><div><div><h3 class="title">
5454 <a name="id2588600"></a><span><strong class="command">zone</strong></span> Statement Definition and Usage</h3></div></div></div>
5455 <div class="sect3" lang="en">
5456 <div class="titlepage"><div><div><h4 class="title">
5457 <a name="id2588608"></a>Zone Types</h4></div></div></div>
5458 <div class="informaltable"><table border="1">
5459 <colgroup>
5460 <col>
5461 <col>
5462 </colgroup>
5463 <tbody>
5464 <tr>
5465 <td>
5466                       <p>
5467                         <code class="varname">master</code>
5468                       </p>
5469                     </td>
5470 <td>
5471                       <p>
5472                         The server has a master copy of the data
5473                         for the zone and will be able to provide authoritative
5474                         answers for
5475                         it.
5476                       </p>
5477                     </td>
5478 </tr>
5479 <tr>
5480 <td>
5481                       <p>
5482                         <code class="varname">slave</code>
5483                       </p>
5484                     </td>
5485 <td>
5486                       <p>
5487                         A slave zone is a replica of a master
5488                         zone. The <span><strong class="command">masters</strong></span> list
5489                         specifies one or more IP addresses
5490                         of master servers that the slave contacts to update
5491                         its copy of the zone.
5492                         Masters list elements can also be names of other
5493                         masters lists.
5494                         By default, transfers are made from port 53 on the
5495                         servers; this can
5496                         be changed for all servers by specifying a port number
5497                         before the
5498                         list of IP addresses, or on a per-server basis after
5499                         the IP address.
5500                         Authentication to the master can also be done with
5501                         per-server TSIG keys.
5502                         If a file is specified, then the
5503                         replica will be written to this file whenever the zone
5504                         is changed,
5505                         and reloaded from this file on a server restart. Use
5506                         of a file is
5507                         recommended, since it often speeds server startup and
5508                         eliminates
5509                         a needless waste of bandwidth. Note that for large
5510                         numbers (in the
5511                         tens or hundreds of thousands) of zones per server, it
5512                         is best to
5513                         use a two-level naming scheme for zone filenames. For
5514                         example,
5515                         a slave server for the zone <code class="literal">example.com</code> might place
5516                         the zone contents into a file called
5517                         <code class="filename">ex/example.com</code> where <code class="filename">ex/</code> is
5518                         just the first two letters of the zone name. (Most
5519                         operating systems
5520                         behave very slowly if you put 100000 files into
5521                         a single directory.)
5522                       </p>
5523                     </td>
5524 </tr>
5525 <tr>
5526 <td>
5527                       <p>
5528                         <code class="varname">stub</code>
5529                       </p>
5530                     </td>
5531 <td>
5532                       <p>
5533                         A stub zone is similar to a slave zone,
5534                         except that it replicates only the NS records of a
5535                         master zone instead
5536                         of the entire zone. Stub zones are not a standard part
5537                         of the DNS;
5538                         they are a feature specific to the <acronym class="acronym">BIND</acronym> implementation.
5539                       </p>
5540
5541                       <p>
5542                         Stub zones can be used to eliminate the need for glue
5543                         NS record
5544                         in a parent zone at the expense of maintaining a stub
5545                         zone entry and
5546                         a set of name server addresses in <code class="filename">named.conf</code>.
5547                         This usage is not recommended for new configurations,
5548                         and BIND 9
5549                         supports it only in a limited way.
5550                         In <acronym class="acronym">BIND</acronym> 4/8, zone
5551                         transfers of a parent zone
5552                         included the NS records from stub children of that
5553                         zone. This meant
5554                         that, in some cases, users could get away with
5555                         configuring child stubs
5556                         only in the master server for the parent zone. <acronym class="acronym">BIND</acronym>
5557                         9 never mixes together zone data from different zones
5558                         in this
5559                         way. Therefore, if a <acronym class="acronym">BIND</acronym> 9 master serving a parent
5560                         zone has child stub zones configured, all the slave
5561                         servers for the
5562                         parent zone also need to have the same child stub
5563                         zones
5564                         configured.
5565                       </p>
5566
5567                       <p>
5568                         Stub zones can also be used as a way of forcing the
5569                         resolution
5570                         of a given domain to use a particular set of
5571                         authoritative servers.
5572                         For example, the caching name servers on a private
5573                         network using
5574                         RFC1918 addressing may be configured with stub zones
5575                         for
5576                         <code class="literal">10.in-addr.arpa</code>
5577                         to use a set of internal name servers as the
5578                         authoritative
5579                         servers for that domain.
5580                       </p>
5581                     </td>
5582 </tr>
5583 <tr>
5584 <td>
5585                       <p>
5586                         <code class="varname">forward</code>
5587                       </p>
5588                     </td>
5589 <td>
5590                       <p>
5591                         A "forward zone" is a way to configure
5592                         forwarding on a per-domain basis.  A <span><strong class="command">zone</strong></span> statement
5593                         of type <span><strong class="command">forward</strong></span> can
5594                         contain a <span><strong class="command">forward</strong></span>
5595                         and/or <span><strong class="command">forwarders</strong></span>
5596                         statement,
5597                         which will apply to queries within the domain given by
5598                         the zone
5599                         name. If no <span><strong class="command">forwarders</strong></span>
5600                         statement is present or
5601                         an empty list for <span><strong class="command">forwarders</strong></span> is given, then no
5602                         forwarding will be done for the domain, canceling the
5603                         effects of
5604                         any forwarders in the <span><strong class="command">options</strong></span> statement. Thus
5605                         if you want to use this type of zone to change the
5606                         behavior of the
5607                         global <span><strong class="command">forward</strong></span> option
5608                         (that is, "forward first"
5609                         to, then "forward only", or vice versa, but want to
5610                         use the same
5611                         servers as set globally) you need to re-specify the
5612                         global forwarders.
5613                       </p>
5614                     </td>
5615 </tr>
5616 <tr>
5617 <td>
5618                       <p>
5619                         <code class="varname">hint</code>
5620                       </p>
5621                     </td>
5622 <td>
5623                       <p>
5624                         The initial set of root name servers is
5625                         specified using a "hint zone". When the server starts
5626                         up, it uses
5627                         the root hints to find a root name server and get the
5628                         most recent
5629                         list of root name servers. If no hint zone is
5630                         specified for class
5631                         IN, the server uses a compiled-in default set of root
5632                         servers hints.
5633                         Classes other than IN have no built-in defaults hints.
5634                       </p>
5635                     </td>
5636 </tr>
5637 <tr>
5638 <td>
5639                       <p>
5640                         <code class="varname">delegation-only</code>
5641                       </p>
5642                     </td>
5643 <td>
5644                       <p>
5645                         This is used to enforce the delegation-only
5646                         status of infrastructure zones (e.g. COM,
5647                         NET, ORG).  Any answer that is received
5648                         without an explicit or implicit delegation
5649                         in the authority section will be treated
5650                         as NXDOMAIN.  This does not apply to the
5651                         zone apex.  This should not be applied to
5652                         leaf zones.
5653                       </p>
5654                       <p>
5655                         <code class="varname">delegation-only</code> has no
5656                         effect on answers received from forwarders.
5657                       </p>
5658                       <p>
5659                         See caveats in <a href="Bv9ARM.ch06.html#root_delegation_only"><span><strong class="command">root-delegation-only</strong></span></a>.
5660                       </p>
5661                     </td>
5662 </tr>
5663 </tbody>
5664 </table></div>
5665 </div>
5666 <div class="sect3" lang="en">
5667 <div class="titlepage"><div><div><h4 class="title">
5668 <a name="id2589104"></a>Class</h4></div></div></div>
5669 <p>
5670               The zone's name may optionally be followed by a class. If
5671               a class is not specified, class <code class="literal">IN</code> (for <code class="varname">Internet</code>),
5672               is assumed. This is correct for the vast majority of cases.
5673             </p>
5674 <p>
5675               The <code class="literal">hesiod</code> class is
5676               named for an information service from MIT's Project Athena. It
5677               is
5678               used to share information about various systems databases, such
5679               as users, groups, printers and so on. The keyword
5680               <code class="literal">HS</code> is
5681               a synonym for hesiod.
5682             </p>
5683 <p>
5684               Another MIT development is Chaosnet, a LAN protocol created
5685               in the mid-1970s. Zone data for it can be specified with the <code class="literal">CHAOS</code> class.
5686             </p>
5687 </div>
5688 <div class="sect3" lang="en">
5689 <div class="titlepage"><div><div><h4 class="title">
5690 <a name="id2589137"></a>Zone Options</h4></div></div></div>
5691 <div class="variablelist"><dl>
5692 <dt><span class="term"><span><strong class="command">allow-notify</strong></span></span></dt>
5693 <dd><p>
5694                     See the description of
5695                     <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>.
5696                   </p></dd>
5697 <dt><span class="term"><span><strong class="command">allow-query</strong></span></span></dt>
5698 <dd><p>
5699                     See the description of
5700                     <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>.
5701                   </p></dd>
5702 <dt><span class="term"><span><strong class="command">allow-query-on</strong></span></span></dt>
5703 <dd><p>
5704                     See the description of
5705                     <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>.
5706                   </p></dd>
5707 <dt><span class="term"><span><strong class="command">allow-transfer</strong></span></span></dt>
5708 <dd><p>
5709                     See the description of <span><strong class="command">allow-transfer</strong></span>
5710                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
5711                   </p></dd>
5712 <dt><span class="term"><span><strong class="command">allow-update</strong></span></span></dt>
5713 <dd><p>
5714                     See the description of <span><strong class="command">allow-update</strong></span>
5715                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
5716                   </p></dd>
5717 <dt><span class="term"><span><strong class="command">update-policy</strong></span></span></dt>
5718 <dd><p>
5719                     Specifies a "Simple Secure Update" policy. See
5720                     <a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called &#8220;Dynamic Update Policies&#8221;</a>.
5721                   </p></dd>
5722 <dt><span class="term"><span><strong class="command">allow-update-forwarding</strong></span></span></dt>
5723 <dd><p>
5724                     See the description of <span><strong class="command">allow-update-forwarding</strong></span>
5725                     in <a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called &#8220;Access Control&#8221;</a>.
5726                   </p></dd>
5727 <dt><span class="term"><span><strong class="command">also-notify</strong></span></span></dt>
5728 <dd><p>
5729                     Only meaningful if <span><strong class="command">notify</strong></span>
5730                     is
5731                     active for this zone. The set of machines that will
5732                     receive a
5733                     <code class="literal">DNS NOTIFY</code> message
5734                     for this zone is made up of all the listed name servers
5735                     (other than
5736                     the primary master) for the zone plus any IP addresses
5737                     specified
5738                     with <span><strong class="command">also-notify</strong></span>. A port
5739                     may be specified
5740                     with each <span><strong class="command">also-notify</strong></span>
5741                     address to send the notify
5742                     messages to a port other than the default of 53.
5743                     <span><strong class="command">also-notify</strong></span> is not
5744                     meaningful for stub zones.
5745                     The default is the empty list.
5746                   </p></dd>
5747 <dt><span class="term"><span><strong class="command">check-names</strong></span></span></dt>
5748 <dd><p>
5749                     This option is used to restrict the character set and
5750                     syntax of
5751                     certain domain names in master files and/or DNS responses
5752                     received from the
5753                     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>
5754                     zones the default is <span><strong class="command">warn</strong></span>.
5755                   </p></dd>
5756 <dt><span class="term"><span><strong class="command">check-mx</strong></span></span></dt>
5757 <dd><p>
5758                     See the description of
5759                     <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>.
5760                   </p></dd>
5761 <dt><span class="term"><span><strong class="command">check-wildcard</strong></span></span></dt>
5762 <dd><p>
5763                     See the description of
5764                     <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>.
5765                   </p></dd>
5766 <dt><span class="term"><span><strong class="command">check-integrity</strong></span></span></dt>
5767 <dd><p>
5768                     See the description of
5769                     <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>.
5770                   </p></dd>
5771 <dt><span class="term"><span><strong class="command">check-sibling</strong></span></span></dt>
5772 <dd><p>
5773                     See the description of
5774                     <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>.
5775                   </p></dd>
5776 <dt><span class="term"><span><strong class="command">zero-no-soa-ttl</strong></span></span></dt>
5777 <dd><p>
5778                     See the description of
5779                     <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>.
5780                   </p></dd>
5781 <dt><span class="term"><span><strong class="command">update-check-ksk</strong></span></span></dt>
5782 <dd><p>
5783                     See the description of
5784                     <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>.
5785                   </p></dd>
5786 <dt><span class="term"><span><strong class="command">try-tcp-refresh</strong></span></span></dt>
5787 <dd><p>
5788                     See the description of
5789                     <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>.
5790                   </p></dd>
5791 <dt><span class="term"><span><strong class="command">database</strong></span></span></dt>
5792 <dd>
5793 <p>
5794                     Specify the type of database to be used for storing the
5795                     zone data.  The string following the <span><strong class="command">database</strong></span> keyword
5796                     is interpreted as a list of whitespace-delimited words.
5797                     The first word
5798                     identifies the database type, and any subsequent words are
5799                     passed
5800                     as arguments to the database to be interpreted in a way
5801                     specific
5802                     to the database type.
5803                   </p>
5804 <p>
5805                     The default is <strong class="userinput"><code>"rbt"</code></strong>, BIND 9's
5806                     native in-memory
5807                     red-black-tree database.  This database does not take
5808                     arguments.
5809                   </p>
5810 <p>
5811                     Other values are possible if additional database drivers
5812                     have been linked into the server.  Some sample drivers are
5813                     included
5814                     with the distribution but none are linked in by default.
5815                   </p>
5816 </dd>
5817 <dt><span class="term"><span><strong class="command">dialup</strong></span></span></dt>
5818 <dd><p>
5819                     See the description of
5820                     <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>.
5821                   </p></dd>
5822 <dt><span class="term"><span><strong class="command">delegation-only</strong></span></span></dt>
5823 <dd>
5824 <p>
5825                     The flag only applies to hint and stub zones.  If set
5826                     to <strong class="userinput"><code>yes</code></strong>, then the zone will also be
5827                     treated as if it is also a delegation-only type zone.
5828                   </p>
5829 <p>
5830                     See caveats in <a href="Bv9ARM.ch06.html#root_delegation_only"><span><strong class="command">root-delegation-only</strong></span></a>.
5831                   </p>
5832 </dd>
5833 <dt><span class="term"><span><strong class="command">forward</strong></span></span></dt>
5834 <dd><p>
5835                     Only meaningful if the zone has a forwarders
5836                     list. The <span><strong class="command">only</strong></span> value causes
5837                     the lookup to fail
5838                     after trying the forwarders and getting no answer, while <span><strong class="command">first</strong></span> would
5839                     allow a normal lookup to be tried.
5840                   </p></dd>
5841 <dt><span class="term"><span><strong class="command">forwarders</strong></span></span></dt>
5842 <dd><p>
5843                     Used to override the list of global forwarders.
5844                     If it is not specified in a zone of type <span><strong class="command">forward</strong></span>,
5845                     no forwarding is done for the zone and the global options are
5846                     not used.
5847                   </p></dd>
5848 <dt><span class="term"><span><strong class="command">ixfr-base</strong></span></span></dt>
5849 <dd><p>
5850                     Was used in <acronym class="acronym">BIND</acronym> 8 to
5851                     specify the name
5852                     of the transaction log (journal) file for dynamic update
5853                     and IXFR.
5854                     <acronym class="acronym">BIND</acronym> 9 ignores the option
5855                     and constructs the name of the journal
5856                     file by appending "<code class="filename">.jnl</code>"
5857                     to the name of the
5858                     zone file.
5859                   </p></dd>
5860 <dt><span class="term"><span><strong class="command">ixfr-tmp-file</strong></span></span></dt>
5861 <dd><p>
5862                     Was an undocumented option in <acronym class="acronym">BIND</acronym> 8.
5863                     Ignored in <acronym class="acronym">BIND</acronym> 9.
5864                   </p></dd>
5865 <dt><span class="term"><span><strong class="command">journal</strong></span></span></dt>
5866 <dd><p>
5867                     Allow the default journal's filename to be overridden.
5868                     The default is the zone's filename with "<code class="filename">.jnl</code>" appended.
5869                     This is applicable to <span><strong class="command">master</strong></span> and <span><strong class="command">slave</strong></span> zones.
5870                   </p></dd>
5871 <dt><span class="term"><span><strong class="command">max-journal-size</strong></span></span></dt>
5872 <dd><p>
5873                     See the description of
5874                     <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>.
5875                   </p></dd>
5876 <dt><span class="term"><span><strong class="command">max-transfer-time-in</strong></span></span></dt>
5877 <dd><p>
5878                     See the description of
5879                     <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>.
5880                   </p></dd>
5881 <dt><span class="term"><span><strong class="command">max-transfer-idle-in</strong></span></span></dt>
5882 <dd><p>
5883                     See the description of
5884                     <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>.
5885                   </p></dd>
5886 <dt><span class="term"><span><strong class="command">max-transfer-time-out</strong></span></span></dt>
5887 <dd><p>
5888                     See the description of
5889                     <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>.
5890                   </p></dd>
5891 <dt><span class="term"><span><strong class="command">max-transfer-idle-out</strong></span></span></dt>
5892 <dd><p>
5893                     See the description of
5894                     <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>.
5895                   </p></dd>
5896 <dt><span class="term"><span><strong class="command">notify</strong></span></span></dt>
5897 <dd><p>
5898                     See the description of
5899                     <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>.
5900                   </p></dd>
5901 <dt><span class="term"><span><strong class="command">notify-delay</strong></span></span></dt>
5902 <dd><p>
5903                     See the description of
5904                     <span><strong class="command">notify-delay</strong></span> in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
5905                   </p></dd>
5906 <dt><span class="term"><span><strong class="command">notify-to-soa</strong></span></span></dt>
5907 <dd><p>
5908                     See the description of
5909                     <span><strong class="command">notify-to-soa</strong></span> in
5910                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
5911                   </p></dd>
5912 <dt><span class="term"><span><strong class="command">pubkey</strong></span></span></dt>
5913 <dd><p>
5914                     In <acronym class="acronym">BIND</acronym> 8, this option was
5915                     intended for specifying
5916                     a public zone key for verification of signatures in DNSSEC
5917                     signed
5918                     zones when they are loaded from disk. <acronym class="acronym">BIND</acronym> 9 does not verify signatures
5919                     on load and ignores the option.
5920                   </p></dd>
5921 <dt><span class="term"><span><strong class="command">zone-statistics</strong></span></span></dt>
5922 <dd><p>
5923                     If <strong class="userinput"><code>yes</code></strong>, the server will keep
5924                     statistical
5925                     information for this zone, which can be dumped to the
5926                     <span><strong class="command">statistics-file</strong></span> defined in
5927                     the server options.
5928                   </p></dd>
5929 <dt><span class="term"><span><strong class="command">sig-validity-interval</strong></span></span></dt>
5930 <dd><p>
5931                     See the description of
5932                     <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>.
5933                   </p></dd>
5934 <dt><span class="term"><span><strong class="command">sig-signing-nodes</strong></span></span></dt>
5935 <dd><p>
5936                     See the description of
5937                     <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>.
5938                   </p></dd>
5939 <dt><span class="term"><span><strong class="command">sig-signing-signatures</strong></span></span></dt>
5940 <dd><p>
5941                     See the description of
5942                     <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>.
5943                   </p></dd>
5944 <dt><span class="term"><span><strong class="command">sig-signing-type</strong></span></span></dt>
5945 <dd><p>
5946                     See the description of
5947                     <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>.
5948                   </p></dd>
5949 <dt><span class="term"><span><strong class="command">transfer-source</strong></span></span></dt>
5950 <dd><p>
5951                     See the description of
5952                     <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>.
5953                   </p></dd>
5954 <dt><span class="term"><span><strong class="command">transfer-source-v6</strong></span></span></dt>
5955 <dd><p>
5956                     See the description of
5957                     <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>.
5958                   </p></dd>
5959 <dt><span class="term"><span><strong class="command">alt-transfer-source</strong></span></span></dt>
5960 <dd><p>
5961                     See the description of
5962                     <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>.
5963                   </p></dd>
5964 <dt><span class="term"><span><strong class="command">alt-transfer-source-v6</strong></span></span></dt>
5965 <dd><p>
5966                     See the description of
5967                     <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>.
5968                   </p></dd>
5969 <dt><span class="term"><span><strong class="command">use-alt-transfer-source</strong></span></span></dt>
5970 <dd><p>
5971                     See the description of
5972                     <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>.
5973                   </p></dd>
5974 <dt><span class="term"><span><strong class="command">notify-source</strong></span></span></dt>
5975 <dd><p>
5976                     See the description of
5977                     <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>.
5978                   </p></dd>
5979 <dt><span class="term"><span><strong class="command">notify-source-v6</strong></span></span></dt>
5980 <dd><p>
5981                     See the description of
5982                     <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>.
5983                   </p></dd>
5984 <dt>
5985 <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>
5986 </dt>
5987 <dd><p>
5988                     See the description in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
5989                   </p></dd>
5990 <dt><span class="term"><span><strong class="command">ixfr-from-differences</strong></span></span></dt>
5991 <dd><p>
5992                     See the description of
5993                     <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>.
5994                     (Note that the <span><strong class="command">ixfr-from-differences</strong></span>
5995                     <strong class="userinput"><code>master</code></strong> and
5996                     <strong class="userinput"><code>slave</code></strong> choices are not
5997                     available at the zone level.)
5998                   </p></dd>
5999 <dt><span class="term"><span><strong class="command">key-directory</strong></span></span></dt>
6000 <dd><p>
6001                     See the description of
6002                     <span><strong class="command">key-directory</strong></span> in <a href="Bv9ARM.ch06.html#options" title="options Statement Definition and
6003           Usage">the section called &#8220;<span><strong class="command">options</strong></span> Statement Definition and
6004           Usage&#8221;</a>.
6005                   </p></dd>
6006 <dt><span class="term"><span><strong class="command">multi-master</strong></span></span></dt>
6007 <dd><p>
6008                     See the description of <span><strong class="command">multi-master</strong></span> in
6009                     <a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called &#8220;Boolean Options&#8221;</a>.
6010                   </p></dd>
6011 <dt><span class="term"><span><strong class="command">masterfile-format</strong></span></span></dt>
6012 <dd><p>
6013                     See the description of <span><strong class="command">masterfile-format</strong></span>
6014                     in <a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called &#8220;Tuning&#8221;</a>.
6015                   </p></dd>
6016 </dl></div>
6017 </div>
6018 <div class="sect3" lang="en">
6019 <div class="titlepage"><div><div><h4 class="title">
6020 <a name="dynamic_update_policies"></a>Dynamic Update Policies</h4></div></div></div>
6021 <p><acronym class="acronym">BIND</acronym> 9 supports two alternative
6022               methods of granting clients the right to perform
6023               dynamic updates to a zone, configured by the
6024               <span><strong class="command">allow-update</strong></span> and
6025               <span><strong class="command">update-policy</strong></span> option, respectively.
6026             </p>
6027 <p>
6028               The <span><strong class="command">allow-update</strong></span> clause works the
6029               same way as in previous versions of <acronym class="acronym">BIND</acronym>.
6030               It grants given clients the permission to update any
6031               record of any name in the zone.
6032             </p>
6033 <p>
6034               The <span><strong class="command">update-policy</strong></span> clause is new
6035               in <acronym class="acronym">BIND</acronym> 9 and allows more fine-grained
6036               control over what updates are allowed.  A set of rules
6037               is specified, where each rule either grants or denies
6038               permissions for one or more names to be updated by
6039               one or more identities.  If the dynamic update request
6040               message is signed (that is, it includes either a TSIG
6041               or SIG(0) record), the identity of the signer can be
6042               determined.
6043             </p>
6044 <p>
6045               Rules are specified in the <span><strong class="command">update-policy</strong></span>
6046               zone option, and are only meaningful for master zones.
6047               When the <span><strong class="command">update-policy</strong></span> statement
6048               is present, it is a configuration error for the
6049               <span><strong class="command">allow-update</strong></span> statement to be
6050               present.  The <span><strong class="command">update-policy</strong></span> statement
6051               only examines the signer of a message; the source
6052               address is not relevant.
6053             </p>
6054 <p>
6055               This is how a rule definition looks:
6056             </p>
6057 <pre class="programlisting">
6058 ( <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>]
6059 </pre>
6060 <p>
6061               Each rule grants or denies privileges.  Once a message has
6062               successfully matched a rule, the operation is immediately
6063               granted
6064               or denied and no further rules are examined.  A rule is matched
6065               when the signer matches the identity field, the name matches the
6066               name field in accordance with the nametype field, and the type
6067               matches
6068               the types specified in the type field.
6069             </p>
6070 <p>
6071               No signer is required for <em class="replaceable"><code>tcp-self</code></em>
6072               or <em class="replaceable"><code>6to4-self</code></em> however the standard
6073               reverse mapping / prefix conversion must match the identity
6074               field.
6075             </p>
6076 <p>
6077               The identity field specifies a name or a wildcard
6078               name.  Normally, this is the name of the TSIG or
6079               SIG(0) key used to sign the update request.  When a
6080               TKEY exchange has been used to create a shared secret,
6081               the identity of the shared secret is the same as the
6082               identity of the key used to authenticate the TKEY
6083               exchange.  TKEY is also the negotiation method used
6084               by GSS-TSIG, which establishes an identity that is
6085               the Kerberos principal of the client, such as
6086               <strong class="userinput"><code>"user@host.domain"</code></strong>.  When the
6087               <em class="replaceable"><code>identity</code></em> field specifies
6088               a wildcard name, it is subject to DNS wildcard
6089               expansion, so the rule will apply to multiple identities.
6090               The <em class="replaceable"><code>identity</code></em> field must
6091               contain a fully-qualified domain name.
6092             </p>
6093 <p>
6094               The <em class="replaceable"><code>nametype</code></em> field has 12
6095               values:
6096               <code class="varname">name</code>, <code class="varname">subdomain</code>,
6097               <code class="varname">wildcard</code>, <code class="varname">self</code>,
6098               <code class="varname">selfsub</code>, <code class="varname">selfwild</code>,
6099               <code class="varname">krb5-self</code>, <code class="varname">ms-self</code>,
6100               <code class="varname">krb5-subdomain</code>,
6101               <code class="varname">ms-subdomain</code>,
6102               <code class="varname">tcp-self</code> and <code class="varname">6to4-self</code>.
6103             </p>
6104 <div class="informaltable"><table border="1">
6105 <colgroup>
6106 <col>
6107 <col>
6108 </colgroup>
6109 <tbody>
6110 <tr>
6111 <td>
6112                       <p>
6113                         <code class="varname">name</code>
6114                       </p>
6115                     </td>
6116 <td>
6117                       <p>
6118                         Exact-match semantics.  This rule matches
6119                         when the name being updated is identical
6120                         to the contents of the
6121                         <em class="replaceable"><code>name</code></em> field.
6122                       </p>
6123                     </td>
6124 </tr>
6125 <tr>
6126 <td>
6127                       <p>
6128                         <code class="varname">subdomain</code>
6129                       </p>
6130                     </td>
6131 <td>
6132                       <p>
6133                         This rule matches when the name being updated
6134                         is a subdomain of, or identical to, the
6135                         contents of the <em class="replaceable"><code>name</code></em>
6136                         field.
6137                       </p>
6138                     </td>
6139 </tr>
6140 <tr>
6141 <td>
6142                       <p>
6143                         <code class="varname">wildcard</code>
6144                       </p>
6145                     </td>
6146 <td>
6147                       <p>
6148                         The <em class="replaceable"><code>name</code></em> field
6149                         is subject to DNS wildcard expansion, and
6150                         this rule matches when the name being updated
6151                         name is a valid expansion of the wildcard.
6152                       </p>
6153                     </td>
6154 </tr>
6155 <tr>
6156 <td>
6157                       <p>
6158                         <code class="varname">self</code>
6159                       </p>
6160                     </td>
6161 <td>
6162                       <p>
6163                         This rule matches when the name being updated
6164                         matches the contents of the
6165                         <em class="replaceable"><code>identity</code></em> field.
6166                         The <em class="replaceable"><code>name</code></em> field
6167                         is ignored, but should be the same as the
6168                         <em class="replaceable"><code>identity</code></em> field.
6169                         The <code class="varname">self</code> nametype is
6170                         most useful when allowing using one key per
6171                         name to update, where the key has the same
6172                         name as the name to be updated.  The
6173                         <em class="replaceable"><code>identity</code></em> would
6174                         be specified as <code class="constant">*</code> (an asterisk) in
6175                         this case.
6176                       </p>
6177                     </td>
6178 </tr>
6179 <tr>
6180 <td>
6181                       <p>
6182                         <code class="varname">selfsub</code>
6183                       </p>
6184                     </td>
6185 <td>
6186                       <p>
6187                         This rule is similar to <code class="varname">self</code>
6188                         except that subdomains of <code class="varname">self</code>
6189                         can also be updated.
6190                       </p>
6191                     </td>
6192 </tr>
6193 <tr>
6194 <td>
6195                       <p>
6196                         <code class="varname">selfwild</code>
6197                       </p>
6198                     </td>
6199 <td>
6200                       <p>
6201                         This rule is similar to <code class="varname">self</code>
6202                         except that only subdomains of
6203                         <code class="varname">self</code> can be updated.
6204                       </p>
6205                     </td>
6206 </tr>
6207 <tr>
6208 <td>
6209                       <p>
6210                         <code class="varname">tcp-self</code>
6211                       </p>
6212                     </td>
6213 <td>
6214                       <p>
6215                         Allow updates that have been sent via TCP and
6216                         for which the standard mapping from the initiating
6217                         IP address into the IN-ADDR.ARPA and IP6.ARPA
6218                         namespaces match the name to be updated.
6219                       </p>
6220                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
6221 <h3 class="title">Note</h3>
6222                         It is theoretically possible to spoof these TCP
6223                         sessions.
6224                       </div>
6225                     </td>
6226 </tr>
6227 <tr>
6228 <td>
6229                       <p>
6230                         <code class="varname">6to4-self</code>
6231                       </p>
6232                     </td>
6233 <td>
6234                       <p>
6235                         Allow the 6to4 prefix to be update by any TCP
6236                         conection from the 6to4 network or from the
6237                         corresponding IPv4 address.  This is intended
6238                         to allow NS or DNAME RRsets to be added to the
6239                         reverse tree.
6240                       </p>
6241                       <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
6242 <h3 class="title">Note</h3>
6243                         It is theoretically possible to spoof these TCP
6244                         sessions.
6245                       </div>
6246                     </td>
6247 </tr>
6248 </tbody>
6249 </table></div>
6250 <p>
6251               In all cases, the <em class="replaceable"><code>name</code></em>
6252               field must
6253               specify a fully-qualified domain name.
6254             </p>
6255 <p>
6256               If no types are explicitly specified, this rule matches
6257               all types except RRSIG, NS, SOA, NSEC and NSEC3. Types
6258               may be specified by name, including "ANY" (ANY matches
6259               all types except NSEC and NSEC3, which can never be
6260               updated).  Note that when an attempt is made to delete
6261               all records associated with a name, the rules are
6262               checked for each existing record type.
6263             </p>
6264 </div>
6265 </div>
6266 </div>
6267 <div class="sect1" lang="en">
6268 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
6269 <a name="id2591216"></a>Zone File</h2></div></div></div>
6270 <div class="sect2" lang="en">
6271 <div class="titlepage"><div><div><h3 class="title">
6272 <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>
6273 <p>
6274             This section, largely borrowed from RFC 1034, describes the
6275             concept of a Resource Record (RR) and explains when each is used.
6276             Since the publication of RFC 1034, several new RRs have been
6277             identified
6278             and implemented in the DNS. These are also included.
6279           </p>
6280 <div class="sect3" lang="en">
6281 <div class="titlepage"><div><div><h4 class="title">
6282 <a name="id2591234"></a>Resource Records</h4></div></div></div>
6283 <p>
6284               A domain name identifies a node.  Each node has a set of
6285               resource information, which may be empty.  The set of resource
6286               information associated with a particular name is composed of
6287               separate RRs. The order of RRs in a set is not significant and
6288               need not be preserved by name servers, resolvers, or other
6289               parts of the DNS. However, sorting of multiple RRs is
6290               permitted for optimization purposes, for example, to specify
6291               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>.
6292             </p>
6293 <p>
6294               The components of a Resource Record are:
6295             </p>
6296 <div class="informaltable"><table border="1">
6297 <colgroup>
6298 <col>
6299 <col>
6300 </colgroup>
6301 <tbody>
6302 <tr>
6303 <td>
6304                       <p>
6305                         owner name
6306                       </p>
6307                     </td>
6308 <td>
6309                       <p>
6310                         The domain name where the RR is found.
6311                       </p>
6312                     </td>
6313 </tr>
6314 <tr>
6315 <td>
6316                       <p>
6317                         type
6318                       </p>
6319                     </td>
6320 <td>
6321                       <p>
6322                         An encoded 16-bit value that specifies
6323                         the type of the resource record.
6324                       </p>
6325                     </td>
6326 </tr>
6327 <tr>
6328 <td>
6329                       <p>
6330                         TTL
6331                       </p>
6332                     </td>
6333 <td>
6334                       <p>
6335                         The time-to-live of the RR. This field
6336                         is a 32-bit integer in units of seconds, and is
6337                         primarily used by
6338                         resolvers when they cache RRs. The TTL describes how
6339                         long a RR can
6340                         be cached before it should be discarded.
6341                       </p>
6342                     </td>
6343 </tr>
6344 <tr>
6345 <td>
6346                       <p>
6347                         class
6348                       </p>
6349                     </td>
6350 <td>
6351                       <p>
6352                         An encoded 16-bit value that identifies
6353                         a protocol family or instance of a protocol.
6354                       </p>
6355                     </td>
6356 </tr>
6357 <tr>
6358 <td>
6359                       <p>
6360                         RDATA
6361                       </p>
6362                     </td>
6363 <td>
6364                       <p>
6365                         The resource data.  The format of the
6366                         data is type (and sometimes class) specific.
6367                       </p>
6368                     </td>
6369 </tr>
6370 </tbody>
6371 </table></div>
6372 <p>
6373               The following are <span class="emphasis"><em>types</em></span> of valid RRs:
6374             </p>
6375 <div class="informaltable"><table border="1">
6376 <colgroup>
6377 <col>
6378 <col>
6379 </colgroup>
6380 <tbody>
6381 <tr>
6382 <td>
6383                       <p>
6384                         A
6385                       </p>
6386                     </td>
6387 <td>
6388                       <p>
6389                         A host address.  In the IN class, this is a
6390                         32-bit IP address.  Described in RFC 1035.
6391                       </p>
6392                     </td>
6393 </tr>
6394 <tr>
6395 <td>
6396                       <p>
6397                         AAAA
6398                       </p>
6399                     </td>
6400 <td>
6401                       <p>
6402                         IPv6 address.  Described in RFC 1886.
6403                       </p>
6404                     </td>
6405 </tr>
6406 <tr>
6407 <td>
6408                       <p>
6409                         A6
6410                       </p>
6411                     </td>
6412 <td>
6413                       <p>
6414                         IPv6 address.  This can be a partial
6415                         address (a suffix) and an indirection to the name
6416                         where the rest of the
6417                         address (the prefix) can be found.  Experimental.
6418                         Described in RFC 2874.
6419                       </p>
6420                     </td>
6421 </tr>
6422 <tr>
6423 <td>
6424                       <p>
6425                         AFSDB
6426                       </p>
6427                     </td>
6428 <td>
6429                       <p>
6430                         Location of AFS database servers.
6431                         Experimental.  Described in RFC 1183.
6432                       </p>
6433                     </td>
6434 </tr>
6435 <tr>
6436 <td>
6437                       <p>
6438                         APL
6439                       </p>
6440                     </td>
6441 <td>
6442                       <p>
6443                         Address prefix list.  Experimental.
6444                         Described in RFC 3123.
6445                       </p>
6446                     </td>
6447 </tr>
6448 <tr>
6449 <td>
6450                       <p>
6451                         CERT
6452                       </p>
6453                     </td>
6454 <td>
6455                       <p>
6456                         Holds a digital certificate.
6457                         Described in RFC 2538.
6458                       </p>
6459                     </td>
6460 </tr>
6461 <tr>
6462 <td>
6463                       <p>
6464                         CNAME
6465                       </p>
6466                     </td>
6467 <td>
6468                       <p>
6469                         Identifies the canonical name of an alias.
6470                         Described in RFC 1035.
6471                       </p>
6472                     </td>
6473 </tr>
6474 <tr>
6475 <td>
6476                       <p>
6477                         DHCID
6478                       </p>
6479                     </td>
6480 <td>
6481                       <p>
6482                         Is used for identifying which DHCP client is
6483                         associated with this name.  Described in RFC 4701.
6484                       </p>
6485                     </td>
6486 </tr>
6487 <tr>
6488 <td>
6489                       <p>
6490                         DNAME
6491                       </p>
6492                     </td>
6493 <td>
6494                       <p>
6495                         Replaces the domain name specified with
6496                         another name to be looked up, effectively aliasing an
6497                         entire
6498                         subtree of the domain name space rather than a single
6499                         record
6500                         as in the case of the CNAME RR.
6501                         Described in RFC 2672.
6502                       </p>
6503                     </td>
6504 </tr>
6505 <tr>
6506 <td>
6507                       <p>
6508                         DNSKEY
6509                       </p>
6510                     </td>
6511 <td>
6512                       <p>
6513                         Stores a public key associated with a signed
6514                         DNS zone.  Described in RFC 4034.
6515                       </p>
6516                     </td>
6517 </tr>
6518 <tr>
6519 <td>
6520                       <p>
6521                         DS
6522                       </p>
6523                     </td>
6524 <td>
6525                       <p>
6526                         Stores the hash of a public key associated with a
6527                         signed DNS zone.  Described in RFC 4034.
6528                       </p>
6529                     </td>
6530 </tr>
6531 <tr>
6532 <td>
6533                       <p>
6534                         GPOS
6535                       </p>
6536                     </td>
6537 <td>
6538                       <p>
6539                         Specifies the global position.  Superseded by LOC.
6540                       </p>
6541                     </td>
6542 </tr>
6543 <tr>
6544 <td>
6545                       <p>
6546                         HINFO
6547                       </p>
6548                     </td>
6549 <td>
6550                       <p>
6551                         Identifies the CPU and OS used by a host.
6552                         Described in RFC 1035.
6553                       </p>
6554                     </td>
6555 </tr>
6556 <tr>
6557 <td>
6558                       <p>
6559                         IPSECKEY
6560                       </p>
6561                     </td>
6562 <td>
6563                       <p>
6564                         Provides a method for storing IPsec keying material in
6565                         DNS.  Described in RFC 4025.
6566                       </p>
6567                     </td>
6568 </tr>
6569 <tr>
6570 <td>
6571                       <p>
6572                         ISDN
6573                       </p>
6574                     </td>
6575 <td>
6576                       <p>
6577                         Representation of ISDN addresses.
6578                         Experimental.  Described in RFC 1183.
6579                       </p>
6580                     </td>
6581 </tr>
6582 <tr>
6583 <td>
6584                       <p>
6585                         KEY
6586                       </p>
6587                     </td>
6588 <td>
6589                       <p>
6590                         Stores a public key associated with a
6591                         DNS name.  Used in original DNSSEC; replaced
6592                         by DNSKEY in DNSSECbis, but still used with
6593                         SIG(0).  Described in RFCs 2535 and 2931.
6594                       </p>
6595                     </td>
6596 </tr>
6597 <tr>
6598 <td>
6599                       <p>
6600                         KX
6601                       </p>
6602                     </td>
6603 <td>
6604                       <p>
6605                         Identifies a key exchanger for this
6606                         DNS name.  Described in RFC 2230.
6607                       </p>
6608                     </td>
6609 </tr>
6610 <tr>
6611 <td>
6612                       <p>
6613                         LOC
6614                       </p>
6615                     </td>
6616 <td>
6617                       <p>
6618                         For storing GPS info.  Described in RFC 1876.
6619                         Experimental.
6620                       </p>
6621                     </td>
6622 </tr>
6623 <tr>
6624 <td>
6625                       <p>
6626                         MX
6627                       </p>
6628                     </td>
6629 <td>
6630                       <p>
6631                         Identifies a mail exchange for the domain with
6632                         a 16-bit preference value (lower is better)
6633                         followed by the host name of the mail exchange.
6634                         Described in RFC 974, RFC 1035.
6635                       </p>
6636                     </td>
6637 </tr>
6638 <tr>
6639 <td>
6640                       <p>
6641                         NAPTR
6642                       </p>
6643                     </td>
6644 <td>
6645                       <p>
6646                         Name authority pointer.  Described in RFC 2915.
6647                       </p>
6648                     </td>
6649 </tr>
6650 <tr>
6651 <td>
6652                       <p>
6653                         NSAP
6654                       </p>
6655                     </td>
6656 <td>
6657                       <p>
6658                         A network service access point.
6659                         Described in RFC 1706.
6660                       </p>
6661                     </td>
6662 </tr>
6663 <tr>
6664 <td>
6665                       <p>
6666                         NS
6667                       </p>
6668                     </td>
6669 <td>
6670                       <p>
6671                         The authoritative name server for the
6672                         domain.  Described in RFC 1035.
6673                       </p>
6674                     </td>
6675 </tr>
6676 <tr>
6677 <td>
6678                       <p>
6679                         NSEC
6680                       </p>
6681                     </td>
6682 <td>
6683                       <p>
6684                         Used in DNSSECbis to securely indicate that
6685                         RRs with an owner name in a certain name interval do
6686                         not exist in
6687                         a zone and indicate what RR types are present for an
6688                         existing name.
6689                         Described in RFC 4034.
6690                       </p>
6691                     </td>
6692 </tr>
6693 <tr>
6694 <td>
6695                       <p>
6696                         NSEC3
6697                       </p>
6698                     </td>
6699 <td>
6700                       <p>
6701                         Used in DNSSECbis to securely indicate that
6702                         RRs with an owner name in a certain name
6703                         interval do not exist in a zone and indicate
6704                         what RR types are present for an existing
6705                         name.  NSEC3 differs from NSEC in that it
6706                         prevents zone enumeration but is more
6707                         computationally expensive on both the server
6708                         and the client than NSEC.  Described in RFC
6709                         5155.
6710                       </p>
6711                     </td>
6712 </tr>
6713 <tr>
6714 <td>
6715                       <p>
6716                         NSEC3PARAM
6717                       </p>
6718                     </td>
6719 <td>
6720                       <p>
6721                         Used in DNSSECbis to tell the authoritative
6722                         server which NSEC3 chains are available to use.
6723                         Described in RFC 5155.
6724                       </p>
6725                     </td>
6726 </tr>
6727 <tr>
6728 <td>
6729                       <p>
6730                         NXT
6731                       </p>
6732                     </td>
6733 <td>
6734                       <p>
6735                         Used in DNSSEC to securely indicate that
6736                         RRs with an owner name in a certain name interval do
6737                         not exist in
6738                         a zone and indicate what RR types are present for an
6739                         existing name.
6740                         Used in original DNSSEC; replaced by NSEC in
6741                         DNSSECbis.
6742                         Described in RFC 2535.
6743                       </p>
6744                     </td>
6745 </tr>
6746 <tr>
6747 <td>
6748                       <p>
6749                         PTR
6750                       </p>
6751                     </td>
6752 <td>
6753                       <p>
6754                         A pointer to another part of the domain
6755                         name space.  Described in RFC 1035.
6756                       </p>
6757                     </td>
6758 </tr>
6759 <tr>
6760 <td>
6761                       <p>
6762                         PX
6763                       </p>
6764                     </td>
6765 <td>
6766                       <p>
6767                         Provides mappings between RFC 822 and X.400
6768                         addresses.  Described in RFC 2163.
6769                       </p>
6770                     </td>
6771 </tr>
6772 <tr>
6773 <td>
6774                       <p>
6775                         RP
6776                       </p>
6777                     </td>
6778 <td>
6779                       <p>
6780                         Information on persons responsible
6781                         for the domain.  Experimental.  Described in RFC 1183.
6782                       </p>
6783                     </td>
6784 </tr>
6785 <tr>
6786 <td>
6787                       <p>
6788                         RRSIG
6789                       </p>
6790                     </td>
6791 <td>
6792                       <p>
6793                         Contains DNSSECbis signature data.  Described
6794                         in RFC 4034.
6795                       </p>
6796                     </td>
6797 </tr>
6798 <tr>
6799 <td>
6800                       <p>
6801                         RT
6802                       </p>
6803                     </td>
6804 <td>
6805                       <p>
6806                         Route-through binding for hosts that
6807                         do not have their own direct wide area network
6808                         addresses.
6809                         Experimental.  Described in RFC 1183.
6810                       </p>
6811                     </td>
6812 </tr>
6813 <tr>
6814 <td>
6815                       <p>
6816                         SIG
6817                       </p>
6818                     </td>
6819 <td>
6820                       <p>
6821                         Contains DNSSEC signature data.  Used in
6822                         original DNSSEC; replaced by RRSIG in
6823                         DNSSECbis, but still used for SIG(0).
6824                         Described in RFCs 2535 and 2931.
6825                       </p>
6826                     </td>
6827 </tr>
6828 <tr>
6829 <td>
6830                       <p>
6831                         SOA
6832                       </p>
6833                     </td>
6834 <td>
6835                       <p>
6836                         Identifies the start of a zone of authority.
6837                         Described in RFC 1035.
6838                       </p>
6839                     </td>
6840 </tr>
6841 <tr>
6842 <td>
6843                       <p>
6844                         SPF
6845                       </p>
6846                     </td>
6847 <td>
6848                       <p>
6849                         Contains the Sender Policy Framework information
6850                         for a given email domain.  Described in RFC 4408.
6851                       </p>
6852                     </td>
6853 </tr>
6854 <tr>
6855 <td>
6856                       <p>
6857                         SRV
6858                       </p>
6859                     </td>
6860 <td>
6861                       <p>
6862                         Information about well known network
6863                         services (replaces WKS).  Described in RFC 2782.
6864                       </p>
6865                     </td>
6866 </tr>
6867 <tr>
6868 <td>
6869                       <p>
6870                         SSHFP
6871                       </p>
6872                     </td>
6873 <td>
6874                       <p>
6875                         Provides a way to securely publish a secure shell key's
6876                         fingerprint.  Described in RFC 4255.
6877                       </p>
6878                     </td>
6879 </tr>
6880 <tr>
6881 <td>
6882                       <p>
6883                         TXT
6884                       </p>
6885                     </td>
6886 <td>
6887                       <p>
6888                         Text records.  Described in RFC 1035.
6889                       </p>
6890                     </td>
6891 </tr>
6892 <tr>
6893 <td>
6894                       <p>
6895                         WKS
6896                       </p>
6897                     </td>
6898 <td>
6899                       <p>
6900                         Information about which well known
6901                         network services, such as SMTP, that a domain
6902                         supports. Historical.
6903                       </p>
6904                     </td>
6905 </tr>
6906 <tr>
6907 <td>
6908                       <p>
6909                         X25
6910                       </p>
6911                     </td>
6912 <td>
6913                       <p>
6914                         Representation of X.25 network addresses.
6915                         Experimental.  Described in RFC 1183.
6916                       </p>
6917                     </td>
6918 </tr>
6919 </tbody>
6920 </table></div>
6921 <p>
6922               The following <span class="emphasis"><em>classes</em></span> of resource records
6923               are currently valid in the DNS:
6924             </p>
6925 <div class="informaltable"><table border="1">
6926 <colgroup>
6927 <col>
6928 <col>
6929 </colgroup>
6930 <tbody>
6931 <tr>
6932 <td>
6933                       <p>
6934                         IN
6935                       </p>
6936                     </td>
6937 <td>
6938                       <p>
6939                         The Internet.
6940                       </p>
6941                     </td>
6942 </tr>
6943 <tr>
6944 <td>
6945                       <p>
6946                         CH
6947                       </p>
6948                     </td>
6949 <td>
6950                       <p>
6951                         Chaosnet, a LAN protocol created at MIT in the
6952                         mid-1970s.
6953                         Rarely used for its historical purpose, but reused for
6954                         BIND's
6955                         built-in server information zones, e.g.,
6956                         <code class="literal">version.bind</code>.
6957                       </p>
6958                     </td>
6959 </tr>
6960 <tr>
6961 <td>
6962                       <p>
6963                         HS
6964                       </p>
6965                     </td>
6966 <td>
6967                       <p>
6968                         Hesiod, an information service
6969                         developed by MIT's Project Athena. It is used to share
6970                         information
6971                         about various systems databases, such as users,
6972                         groups, printers
6973                         and so on.
6974                       </p>
6975                     </td>
6976 </tr>
6977 </tbody>
6978 </table></div>
6979 <p>
6980               The owner name is often implicit, rather than forming an
6981               integral
6982               part of the RR.  For example, many name servers internally form
6983               tree
6984               or hash structures for the name space, and chain RRs off nodes.
6985               The remaining RR parts are the fixed header (type, class, TTL)
6986               which is consistent for all RRs, and a variable part (RDATA)
6987               that
6988               fits the needs of the resource being described.
6989             </p>
6990 <p>
6991               The meaning of the TTL field is a time limit on how long an
6992               RR can be kept in a cache.  This limit does not apply to
6993               authoritative
6994               data in zones; it is also timed out, but by the refreshing
6995               policies
6996               for the zone.  The TTL is assigned by the administrator for the
6997               zone where the data originates.  While short TTLs can be used to
6998               minimize caching, and a zero TTL prohibits caching, the
6999               realities
7000               of Internet performance suggest that these times should be on
7001               the
7002               order of days for the typical host.  If a change can be
7003               anticipated,
7004               the TTL can be reduced prior to the change to minimize
7005               inconsistency
7006               during the change, and then increased back to its former value
7007               following
7008               the change.
7009             </p>
7010 <p>
7011               The data in the RDATA section of RRs is carried as a combination
7012               of binary strings and domain names.  The domain names are
7013               frequently
7014               used as "pointers" to other data in the DNS.
7015             </p>
7016 </div>
7017 <div class="sect3" lang="en">
7018 <div class="titlepage"><div><div><h4 class="title">
7019 <a name="id2592857"></a>Textual expression of RRs</h4></div></div></div>
7020 <p>
7021               RRs are represented in binary form in the packets of the DNS
7022               protocol, and are usually represented in highly encoded form
7023               when
7024               stored in a name server or resolver.  In the examples provided
7025               in
7026               RFC 1034, a style similar to that used in master files was
7027               employed
7028               in order to show the contents of RRs.  In this format, most RRs
7029               are shown on a single line, although continuation lines are
7030               possible
7031               using parentheses.
7032             </p>
7033 <p>
7034               The start of the line gives the owner of the RR.  If a line
7035               begins with a blank, then the owner is assumed to be the same as
7036               that of the previous RR.  Blank lines are often included for
7037               readability.
7038             </p>
7039 <p>
7040               Following the owner, we list the TTL, type, and class of the
7041               RR.  Class and type use the mnemonics defined above, and TTL is
7042               an integer before the type field.  In order to avoid ambiguity
7043               in
7044               parsing, type and class mnemonics are disjoint, TTLs are
7045               integers,
7046               and the type mnemonic is always last. The IN class and TTL
7047               values
7048               are often omitted from examples in the interests of clarity.
7049             </p>
7050 <p>
7051               The resource data or RDATA section of the RR are given using
7052               knowledge of the typical representation for the data.
7053             </p>
7054 <p>
7055               For example, we might show the RRs carried in a message as:
7056             </p>
7057 <div class="informaltable"><table border="1">
7058 <colgroup>
7059 <col>
7060 <col>
7061 <col>
7062 </colgroup>
7063 <tbody>
7064 <tr>
7065 <td>
7066                       <p>
7067                         <code class="literal">ISI.EDU.</code>
7068                       </p>
7069                     </td>
7070 <td>
7071                       <p>
7072                         <code class="literal">MX</code>
7073                       </p>
7074                     </td>
7075 <td>
7076                       <p>
7077                         <code class="literal">10 VENERA.ISI.EDU.</code>
7078                       </p>
7079                     </td>
7080 </tr>
7081 <tr>
7082 <td>
7083                       <p></p>
7084                     </td>
7085 <td>
7086                       <p>
7087                         <code class="literal">MX</code>
7088                       </p>
7089                     </td>
7090 <td>
7091                       <p>
7092                         <code class="literal">10 VAXA.ISI.EDU</code>
7093                       </p>
7094                     </td>
7095 </tr>
7096 <tr>
7097 <td>
7098                       <p>
7099                         <code class="literal">VENERA.ISI.EDU</code>
7100                       </p>
7101                     </td>
7102 <td>
7103                       <p>
7104                         <code class="literal">A</code>
7105                       </p>
7106                     </td>
7107 <td>
7108                       <p>
7109                         <code class="literal">128.9.0.32</code>
7110                       </p>
7111                     </td>
7112 </tr>
7113 <tr>
7114 <td>
7115                       <p></p>
7116                     </td>
7117 <td>
7118                       <p>
7119                         <code class="literal">A</code>
7120                       </p>
7121                     </td>
7122 <td>
7123                       <p>
7124                         <code class="literal">10.1.0.52</code>
7125                       </p>
7126                     </td>
7127 </tr>
7128 <tr>
7129 <td>
7130                       <p>
7131                         <code class="literal">VAXA.ISI.EDU</code>
7132                       </p>
7133                     </td>
7134 <td>
7135                       <p>
7136                         <code class="literal">A</code>
7137                       </p>
7138                     </td>
7139 <td>
7140                       <p>
7141                         <code class="literal">10.2.0.27</code>
7142                       </p>
7143                     </td>
7144 </tr>
7145 <tr>
7146 <td>
7147                       <p></p>
7148                     </td>
7149 <td>
7150                       <p>
7151                         <code class="literal">A</code>
7152                       </p>
7153                     </td>
7154 <td>
7155                       <p>
7156                         <code class="literal">128.9.0.33</code>
7157                       </p>
7158                     </td>
7159 </tr>
7160 </tbody>
7161 </table></div>
7162 <p>
7163               The MX RRs have an RDATA section which consists of a 16-bit
7164               number followed by a domain name.  The address RRs use a
7165               standard
7166               IP address format to contain a 32-bit internet address.
7167             </p>
7168 <p>
7169               The above example shows six RRs, with two RRs at each of three
7170               domain names.
7171             </p>
7172 <p>
7173               Similarly we might see:
7174             </p>
7175 <div class="informaltable"><table border="1">
7176 <colgroup>
7177 <col>
7178 <col>
7179 <col>
7180 </colgroup>
7181 <tbody>
7182 <tr>
7183 <td>
7184                       <p>
7185                         <code class="literal">XX.LCS.MIT.EDU.</code>
7186                       </p>
7187                     </td>
7188 <td>
7189                       <p>
7190                         <code class="literal">IN A</code>
7191                       </p>
7192                     </td>
7193 <td>
7194                       <p>
7195                         <code class="literal">10.0.0.44</code>
7196                       </p>
7197                     </td>
7198 </tr>
7199 <tr>
7200 <td> </td>
7201 <td>
7202                       <p>
7203                         <code class="literal">CH A</code>
7204                       </p>
7205                     </td>
7206 <td>
7207                       <p>
7208                         <code class="literal">MIT.EDU. 2420</code>
7209                       </p>
7210                     </td>
7211 </tr>
7212 </tbody>
7213 </table></div>
7214 <p>
7215               This example shows two addresses for
7216               <code class="literal">XX.LCS.MIT.EDU</code>, each of a different class.
7217             </p>
7218 </div>
7219 </div>
7220 <div class="sect2" lang="en">
7221 <div class="titlepage"><div><div><h3 class="title">
7222 <a name="id2593378"></a>Discussion of MX Records</h3></div></div></div>
7223 <p>
7224             As described above, domain servers store information as a
7225             series of resource records, each of which contains a particular
7226             piece of information about a given domain name (which is usually,
7227             but not always, a host). The simplest way to think of a RR is as
7228             a typed pair of data, a domain name matched with a relevant datum,
7229             and stored with some additional type information to help systems
7230             determine when the RR is relevant.
7231           </p>
7232 <p>
7233             MX records are used to control delivery of email. The data
7234             specified in the record is a priority and a domain name. The
7235             priority
7236             controls the order in which email delivery is attempted, with the
7237             lowest number first. If two priorities are the same, a server is
7238             chosen randomly. If no servers at a given priority are responding,
7239             the mail transport agent will fall back to the next largest
7240             priority.
7241             Priority numbers do not have any absolute meaning &#8212; they are
7242             relevant
7243             only respective to other MX records for that domain name. The
7244             domain
7245             name given is the machine to which the mail will be delivered.
7246             It <span class="emphasis"><em>must</em></span> have an associated address record
7247             (A or AAAA) &#8212; CNAME is not sufficient.
7248           </p>
7249 <p>
7250             For a given domain, if there is both a CNAME record and an
7251             MX record, the MX record is in error, and will be ignored.
7252             Instead,
7253             the mail will be delivered to the server specified in the MX
7254             record
7255             pointed to by the CNAME.
7256             For example:
7257           </p>
7258 <div class="informaltable"><table border="1">
7259 <colgroup>
7260 <col>
7261 <col>
7262 <col>
7263 <col>
7264 <col>
7265 </colgroup>
7266 <tbody>
7267 <tr>
7268 <td>
7269                     <p>
7270                       <code class="literal">example.com.</code>
7271                     </p>
7272                   </td>
7273 <td>
7274                     <p>
7275                       <code class="literal">IN</code>
7276                     </p>
7277                   </td>
7278 <td>
7279                     <p>
7280                       <code class="literal">MX</code>
7281                     </p>
7282                   </td>
7283 <td>
7284                     <p>
7285                       <code class="literal">10</code>
7286                     </p>
7287                   </td>
7288 <td>
7289                     <p>
7290                       <code class="literal">mail.example.com.</code>
7291                     </p>
7292                   </td>
7293 </tr>
7294 <tr>
7295 <td>
7296                     <p></p>
7297                   </td>
7298 <td>
7299                     <p>
7300                       <code class="literal">IN</code>
7301                     </p>
7302                   </td>
7303 <td>
7304                     <p>
7305                       <code class="literal">MX</code>
7306                     </p>
7307                   </td>
7308 <td>
7309                     <p>
7310                       <code class="literal">10</code>
7311                     </p>
7312                   </td>
7313 <td>
7314                     <p>
7315                       <code class="literal">mail2.example.com.</code>
7316                     </p>
7317                   </td>
7318 </tr>
7319 <tr>
7320 <td>
7321                     <p></p>
7322                   </td>
7323 <td>
7324                     <p>
7325                       <code class="literal">IN</code>
7326                     </p>
7327                   </td>
7328 <td>
7329                     <p>
7330                       <code class="literal">MX</code>
7331                     </p>
7332                   </td>
7333 <td>
7334                     <p>
7335                       <code class="literal">20</code>
7336                     </p>
7337                   </td>
7338 <td>
7339                     <p>
7340                       <code class="literal">mail.backup.org.</code>
7341                     </p>
7342                   </td>
7343 </tr>
7344 <tr>
7345 <td>
7346                     <p>
7347                       <code class="literal">mail.example.com.</code>
7348                     </p>
7349                   </td>
7350 <td>
7351                     <p>
7352                       <code class="literal">IN</code>
7353                     </p>
7354                   </td>
7355 <td>
7356                     <p>
7357                       <code class="literal">A</code>
7358                     </p>
7359                   </td>
7360 <td>
7361                     <p>
7362                       <code class="literal">10.0.0.1</code>
7363                     </p>
7364                   </td>
7365 <td>
7366                     <p></p>
7367                   </td>
7368 </tr>
7369 <tr>
7370 <td>
7371                     <p>
7372                       <code class="literal">mail2.example.com.</code>
7373                     </p>
7374                   </td>
7375 <td>
7376                     <p>
7377                       <code class="literal">IN</code>
7378                     </p>
7379                   </td>
7380 <td>
7381                     <p>
7382                       <code class="literal">A</code>
7383                     </p>
7384                   </td>
7385 <td>
7386                     <p>
7387                       <code class="literal">10.0.0.2</code>
7388                     </p>
7389                   </td>
7390 <td>
7391                     <p></p>
7392                   </td>
7393 </tr>
7394 </tbody>
7395 </table></div>
7396 <p>
7397             Mail delivery will be attempted to <code class="literal">mail.example.com</code> and
7398             <code class="literal">mail2.example.com</code> (in
7399             any order), and if neither of those succeed, delivery to <code class="literal">mail.backup.org</code> will
7400             be attempted.
7401           </p>
7402 </div>
7403 <div class="sect2" lang="en">
7404 <div class="titlepage"><div><div><h3 class="title">
7405 <a name="Setting_TTLs"></a>Setting TTLs</h3></div></div></div>
7406 <p>
7407             The time-to-live of the RR field is a 32-bit integer represented
7408             in units of seconds, and is primarily used by resolvers when they
7409             cache RRs. The TTL describes how long a RR can be cached before it
7410             should be discarded. The following three types of TTL are
7411             currently
7412             used in a zone file.
7413           </p>
7414 <div class="informaltable"><table border="1">
7415 <colgroup>
7416 <col>
7417 <col>
7418 </colgroup>
7419 <tbody>
7420 <tr>
7421 <td>
7422                     <p>
7423                       SOA
7424                     </p>
7425                   </td>
7426 <td>
7427                     <p>
7428                       The last field in the SOA is the negative
7429                       caching TTL. This controls how long other servers will
7430                       cache no-such-domain
7431                       (NXDOMAIN) responses from you.
7432                     </p>
7433                     <p>
7434                       The maximum time for
7435                       negative caching is 3 hours (3h).
7436                     </p>
7437                   </td>
7438 </tr>
7439 <tr>
7440 <td>
7441                     <p>
7442                       $TTL
7443                     </p>
7444                   </td>
7445 <td>
7446                     <p>
7447                       The $TTL directive at the top of the
7448                       zone file (before the SOA) gives a default TTL for every
7449                       RR without
7450                       a specific TTL set.
7451                     </p>
7452                   </td>
7453 </tr>
7454 <tr>
7455 <td>
7456                     <p>
7457                       RR TTLs
7458                     </p>
7459                   </td>
7460 <td>
7461                     <p>
7462                       Each RR can have a TTL as the second
7463                       field in the RR, which will control how long other
7464                       servers can cache
7465                       the it.
7466                     </p>
7467                   </td>
7468 </tr>
7469 </tbody>
7470 </table></div>
7471 <p>
7472             All of these TTLs default to units of seconds, though units
7473             can be explicitly specified, for example, <code class="literal">1h30m</code>.
7474           </p>
7475 </div>
7476 <div class="sect2" lang="en">
7477 <div class="titlepage"><div><div><h3 class="title">
7478 <a name="id2593993"></a>Inverse Mapping in IPv4</h3></div></div></div>
7479 <p>
7480             Reverse name resolution (that is, translation from IP address
7481             to name) is achieved by means of the <span class="emphasis"><em>in-addr.arpa</em></span> domain
7482             and PTR records. Entries in the in-addr.arpa domain are made in
7483             least-to-most significant order, read left to right. This is the
7484             opposite order to the way IP addresses are usually written. Thus,
7485             a machine with an IP address of 10.1.2.3 would have a
7486             corresponding
7487             in-addr.arpa name of
7488             3.2.1.10.in-addr.arpa. This name should have a PTR resource record
7489             whose data field is the name of the machine or, optionally,
7490             multiple
7491             PTR records if the machine has more than one name. For example,
7492             in the [<span class="optional">example.com</span>] domain:
7493           </p>
7494 <div class="informaltable"><table border="1">
7495 <colgroup>
7496 <col>
7497 <col>
7498 </colgroup>
7499 <tbody>
7500 <tr>
7501 <td>
7502                     <p>
7503                       <code class="literal">$ORIGIN</code>
7504                     </p>
7505                   </td>
7506 <td>
7507                     <p>
7508                       <code class="literal">2.1.10.in-addr.arpa</code>
7509                     </p>
7510                   </td>
7511 </tr>
7512 <tr>
7513 <td>
7514                     <p>
7515                       <code class="literal">3</code>
7516                     </p>
7517                   </td>
7518 <td>
7519                     <p>
7520                       <code class="literal">IN PTR foo.example.com.</code>
7521                     </p>
7522                   </td>
7523 </tr>
7524 </tbody>
7525 </table></div>
7526 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
7527 <h3 class="title">Note</h3>
7528 <p>
7529               The <span><strong class="command">$ORIGIN</strong></span> lines in the examples
7530               are for providing context to the examples only &#8212; they do not
7531               necessarily
7532               appear in the actual usage. They are only used here to indicate
7533               that the example is relative to the listed origin.
7534             </p>
7535 </div>
7536 </div>
7537 <div class="sect2" lang="en">
7538 <div class="titlepage"><div><div><h3 class="title">
7539 <a name="id2594188"></a>Other Zone File Directives</h3></div></div></div>
7540 <p>
7541             The Master File Format was initially defined in RFC 1035 and
7542             has subsequently been extended. While the Master File Format
7543             itself
7544             is class independent all records in a Master File must be of the
7545             same
7546             class.
7547           </p>
7548 <p>
7549             Master File Directives include <span><strong class="command">$ORIGIN</strong></span>, <span><strong class="command">$INCLUDE</strong></span>,
7550             and <span><strong class="command">$TTL.</strong></span>
7551           </p>
7552 <div class="sect3" lang="en">
7553 <div class="titlepage"><div><div><h4 class="title">
7554 <a name="id2594211"></a>The <span><strong class="command">@</strong></span> (at-sign)</h4></div></div></div>
7555 <p>
7556               When used in the label (or name) field, the asperand or
7557               at-sign (@) symbol represents the current origin.
7558               At the start of the zone file, it is the
7559               &lt;<code class="varname">zone_name</code>&gt; (followed by
7560               trailing dot).
7561             </p>
7562 </div>
7563 <div class="sect3" lang="en">
7564 <div class="titlepage"><div><div><h4 class="title">
7565 <a name="id2594227"></a>The <span><strong class="command">$ORIGIN</strong></span> Directive</h4></div></div></div>
7566 <p>
7567               Syntax: <span><strong class="command">$ORIGIN</strong></span>
7568               <em class="replaceable"><code>domain-name</code></em>
7569               [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
7570             </p>
7571 <p><span><strong class="command">$ORIGIN</strong></span>
7572               sets the domain name that will be appended to any
7573               unqualified records. When a zone is first read in there
7574               is an implicit <span><strong class="command">$ORIGIN</strong></span>
7575               &lt;<code class="varname">zone_name</code>&gt;<span><strong class="command">.</strong></span>
7576               (followed by trailing dot).
7577               The current <span><strong class="command">$ORIGIN</strong></span> is appended to
7578               the domain specified in the <span><strong class="command">$ORIGIN</strong></span>
7579               argument if it is not absolute.
7580             </p>
7581 <pre class="programlisting">
7582 $ORIGIN example.com.
7583 WWW     CNAME   MAIN-SERVER
7584 </pre>
7585 <p>
7586               is equivalent to
7587             </p>
7588 <pre class="programlisting">
7589 WWW.EXAMPLE.COM. CNAME MAIN-SERVER.EXAMPLE.COM.
7590 </pre>
7591 </div>
7592 <div class="sect3" lang="en">
7593 <div class="titlepage"><div><div><h4 class="title">
7594 <a name="id2594356"></a>The <span><strong class="command">$INCLUDE</strong></span> Directive</h4></div></div></div>
7595 <p>
7596               Syntax: <span><strong class="command">$INCLUDE</strong></span>
7597               <em class="replaceable"><code>filename</code></em>
7598               [<span class="optional">
7599 <em class="replaceable"><code>origin</code></em> </span>]
7600               [<span class="optional"> <em class="replaceable"><code>comment</code></em> </span>]
7601             </p>
7602 <p>
7603               Read and process the file <code class="filename">filename</code> as
7604               if it were included into the file at this point.  If <span><strong class="command">origin</strong></span> is
7605               specified the file is processed with <span><strong class="command">$ORIGIN</strong></span> set
7606               to that value, otherwise the current <span><strong class="command">$ORIGIN</strong></span> is
7607               used.
7608             </p>
7609 <p>
7610               The origin and the current domain name
7611               revert to the values they had prior to the <span><strong class="command">$INCLUDE</strong></span> once
7612               the file has been read.
7613             </p>
7614 <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
7615 <h3 class="title">Note</h3>
7616 <p>
7617                 RFC 1035 specifies that the current origin should be restored
7618                 after
7619                 an <span><strong class="command">$INCLUDE</strong></span>, but it is silent
7620                 on whether the current
7621                 domain name should also be restored.  BIND 9 restores both of
7622                 them.
7623                 This could be construed as a deviation from RFC 1035, a
7624                 feature, or both.
7625               </p>
7626 </div>
7627 </div>
7628 <div class="sect3" lang="en">
7629 <div class="titlepage"><div><div><h4 class="title">
7630 <a name="id2594425"></a>The <span><strong class="command">$TTL</strong></span> Directive</h4></div></div></div>
7631 <p>
7632               Syntax: <span><strong class="command">$TTL</strong></span>
7633               <em class="replaceable"><code>default-ttl</code></em>
7634               [<span class="optional">
7635 <em class="replaceable"><code>comment</code></em> </span>]
7636             </p>
7637 <p>
7638               Set the default Time To Live (TTL) for subsequent records
7639               with undefined TTLs. Valid TTLs are of the range 0-2147483647
7640               seconds.
7641             </p>
7642 <p><span><strong class="command">$TTL</strong></span>
7643                is defined in RFC 2308.
7644             </p>
7645 </div>
7646 </div>
7647 <div class="sect2" lang="en">
7648 <div class="titlepage"><div><div><h3 class="title">
7649 <a name="id2594461"></a><acronym class="acronym">BIND</acronym> Master File Extension: the  <span><strong class="command">$GENERATE</strong></span> Directive</h3></div></div></div>
7650 <p>
7651             Syntax: <span><strong class="command">$GENERATE</strong></span>
7652             <em class="replaceable"><code>range</code></em>
7653             <em class="replaceable"><code>lhs</code></em>
7654             [<span class="optional"><em class="replaceable"><code>ttl</code></em></span>]
7655             [<span class="optional"><em class="replaceable"><code>class</code></em></span>]
7656             <em class="replaceable"><code>type</code></em>
7657             <em class="replaceable"><code>rhs</code></em>
7658             [<span class="optional"><em class="replaceable"><code>comment</code></em></span>]
7659           </p>
7660 <p><span><strong class="command">$GENERATE</strong></span>
7661             is used to create a series of resource records that only
7662             differ from each other by an
7663             iterator. <span><strong class="command">$GENERATE</strong></span> can be used to
7664             easily generate the sets of records required to support
7665             sub /24 reverse delegations described in RFC 2317:
7666             Classless IN-ADDR.ARPA delegation.
7667           </p>
7668 <pre class="programlisting">$ORIGIN 0.0.192.IN-ADDR.ARPA.
7669 $GENERATE 1-2 0 NS SERVER$.EXAMPLE.
7670 $GENERATE 1-127 $ CNAME $.0</pre>
7671 <p>
7672             is equivalent to
7673           </p>
7674 <pre class="programlisting">0.0.0.192.IN-ADDR.ARPA. NS SERVER1.EXAMPLE.
7675 0.0.0.192.IN-ADDR.ARPA. NS SERVER2.EXAMPLE.
7676 1.0.0.192.IN-ADDR.ARPA. CNAME 1.0.0.0.192.IN-ADDR.ARPA.
7677 2.0.0.192.IN-ADDR.ARPA. CNAME 2.0.0.0.192.IN-ADDR.ARPA.
7678 ...
7679 127.0.0.192.IN-ADDR.ARPA. CNAME 127.0.0.0.192.IN-ADDR.ARPA.
7680 </pre>
7681 <div class="informaltable"><table border="1">
7682 <colgroup>
7683 <col>
7684 <col>
7685 </colgroup>
7686 <tbody>
7687 <tr>
7688 <td>
7689                     <p><span><strong class="command">range</strong></span></p>
7690                   </td>
7691 <td>
7692                     <p>
7693                       This can be one of two forms: start-stop
7694                       or start-stop/step. If the first form is used, then step
7695                       is set to
7696                       1. All of start, stop and step must be positive.
7697                     </p>
7698                   </td>
7699 </tr>
7700 <tr>
7701 <td>
7702                     <p><span><strong class="command">lhs</strong></span></p>
7703                   </td>
7704 <td>
7705                     <p>This
7706                       describes the owner name of the resource records
7707                       to be created.  Any single <span><strong class="command">$</strong></span>
7708                       (dollar sign)
7709                       symbols within the <span><strong class="command">lhs</strong></span> string
7710                       are replaced by the iterator value.
7711
7712                       To get a $ in the output, you need to escape the
7713                       <span><strong class="command">$</strong></span> using a backslash
7714                       <span><strong class="command">\</strong></span>,
7715                       e.g. <span><strong class="command">\$</strong></span>. The
7716                       <span><strong class="command">$</strong></span> may optionally be followed
7717                       by modifiers which change the offset from the
7718                       iterator, field width and base.
7719
7720                       Modifiers are introduced by a
7721                       <span><strong class="command">{</strong></span> (left brace) immediately following the
7722                       <span><strong class="command">$</strong></span> as
7723                       <span><strong class="command">${offset[,width[,base]]}</strong></span>.
7724                       For example, <span><strong class="command">${-20,3,d}</strong></span>
7725                       subtracts 20 from the current value, prints the
7726                       result as a decimal in a zero-padded field of
7727                       width 3.
7728
7729                       Available output forms are decimal
7730                       (<span><strong class="command">d</strong></span>), octal
7731                       (<span><strong class="command">o</strong></span>) and hexadecimal
7732                       (<span><strong class="command">x</strong></span> or <span><strong class="command">X</strong></span>
7733                       for uppercase).  The default modifier is
7734                       <span><strong class="command">${0,0,d}</strong></span>.  If the
7735                       <span><strong class="command">lhs</strong></span> is not absolute, the
7736                       current <span><strong class="command">$ORIGIN</strong></span> is appended
7737                       to the name.
7738                     </p>
7739                     <p>
7740                       For compatibility with earlier versions, <span><strong class="command">$$</strong></span> is still
7741                       recognized as indicating a literal $ in the output.
7742                     </p>
7743                   </td>
7744 </tr>
7745 <tr>
7746 <td>
7747                     <p><span><strong class="command">ttl</strong></span></p>
7748                   </td>
7749 <td>
7750                     <p>
7751                       Specifies the time-to-live of the generated records. If
7752                       not specified this will be inherited using the
7753                       normal TTL inheritance rules.
7754                     </p>
7755                     <p><span><strong class="command">class</strong></span>
7756                       and <span><strong class="command">ttl</strong></span> can be
7757                       entered in either order.
7758                     </p>
7759                   </td>
7760 </tr>
7761 <tr>
7762 <td>
7763                     <p><span><strong class="command">class</strong></span></p>
7764                   </td>
7765 <td>
7766                     <p>
7767                       Specifies the class of the generated records.
7768                       This must match the zone class if it is
7769                       specified.
7770                     </p>
7771                     <p><span><strong class="command">class</strong></span>
7772                       and <span><strong class="command">ttl</strong></span> can be
7773                       entered in either order.
7774                     </p>
7775                   </td>
7776 </tr>
7777 <tr>
7778 <td>
7779                     <p><span><strong class="command">type</strong></span></p>
7780                   </td>
7781 <td>
7782                     <p>
7783                       At present the only supported types are
7784                       PTR, CNAME, DNAME, A, AAAA and NS.
7785                     </p>
7786                   </td>
7787 </tr>
7788 <tr>
7789 <td>
7790                     <p><span><strong class="command">rhs</strong></span></p>
7791                   </td>
7792 <td>
7793                     <p>
7794                       <span><strong class="command">rhs</strong></span> is a domain name. It is processed
7795                       similarly to lhs.
7796                     </p>
7797                   </td>
7798 </tr>
7799 </tbody>
7800 </table></div>
7801 <p>
7802             The <span><strong class="command">$GENERATE</strong></span> directive is a <acronym class="acronym">BIND</acronym> extension
7803             and not part of the standard zone file format.
7804           </p>
7805 <p>
7806             BIND 8 does not support the optional TTL and CLASS fields.
7807           </p>
7808 </div>
7809 <div class="sect2" lang="en">
7810 <div class="titlepage"><div><div><h3 class="title">
7811 <a name="zonefile_format"></a>Additional File Formats</h3></div></div></div>
7812 <p>
7813             In addition to the standard textual format, BIND 9
7814             supports the ability to read or dump to zone files in
7815             other formats.  The <code class="constant">raw</code> format is
7816             currently available as an additional format.  It is a
7817             binary format representing BIND 9's internal data
7818             structure directly, thereby remarkably improving the
7819             loading time.
7820           </p>
7821 <p>
7822             For a primary server, a zone file in the
7823             <code class="constant">raw</code> format is expected to be
7824             generated from a textual zone file by the
7825             <span><strong class="command">named-compilezone</strong></span> command.  For a
7826             secondary server or for a dynamic zone, it is automatically
7827             generated (if this format is specified by the
7828             <span><strong class="command">masterfile-format</strong></span> option) when
7829             <span><strong class="command">named</strong></span> dumps the zone contents after
7830             zone transfer or when applying prior updates.
7831           </p>
7832 <p>
7833             If a zone file in a binary format needs manual modification,
7834             it first must be converted to a textual form by the
7835             <span><strong class="command">named-compilezone</strong></span> command.  All
7836             necessary modification should go to the text file, which
7837             should then be converted to the binary form by the
7838             <span><strong class="command">named-compilezone</strong></span> command again.
7839           </p>
7840 <p>
7841              Although the <code class="constant">raw</code> format uses the
7842              network byte order and avoids architecture-dependent
7843              data alignment so that it is as much portable as
7844              possible, it is primarily expected to be used inside
7845              the same single system.  In order to export a zone
7846              file in the <code class="constant">raw</code> format or make a
7847              portable backup of the file, it is recommended to
7848              convert the file to the standard textual representation.
7849           </p>
7850 </div>
7851 </div>
7852 <div class="sect1" lang="en">
7853 <div class="titlepage"><div><div><h2 class="title" style="clear: both">
7854 <a name="statistics"></a>BIND9 Statistics</h2></div></div></div>
7855 <p>
7856           <acronym class="acronym">BIND</acronym> 9 maintains lots of statistics
7857           information and provides several interfaces for users to
7858           get access to the statistics.
7859           The available statistics include all statistics counters
7860           that were available in <acronym class="acronym">BIND</acronym> 8 and
7861           are meaningful in <acronym class="acronym">BIND</acronym> 9,
7862           and other information that is considered useful.
7863         </p>
7864 <p>
7865           The statistics information is categorized into the following
7866           sections.
7867         </p>
7868 <div class="informaltable"><table border="1">
7869 <colgroup>
7870 <col>
7871 <col>
7872 </colgroup>
7873 <tbody>
7874 <tr>
7875 <td>
7876                   <p>Incoming Requests</p>
7877                 </td>
7878 <td>
7879                   <p>
7880                     The number of incoming DNS requests for each OPCODE.
7881                   </p>
7882                 </td>
7883 </tr>
7884 <tr>
7885 <td>
7886                   <p>Incoming Queries</p>
7887                 </td>
7888 <td>
7889                   <p>
7890                     The number of incoming queries for each RR type.
7891                   </p>
7892                 </td>
7893 </tr>
7894 <tr>
7895 <td>
7896                   <p>Outgoing Queries</p>
7897                 </td>
7898 <td>
7899                   <p>
7900                     The number of outgoing queries for each RR
7901                     type sent from the internal resolver.
7902                     Maintained per view.
7903                   </p>
7904                 </td>
7905 </tr>
7906 <tr>
7907 <td>
7908                   <p>Name Server Statistics</p>
7909                 </td>
7910 <td>
7911                   <p>
7912                     Statistics counters about incoming request processing.
7913                   </p>
7914                 </td>
7915 </tr>
7916 <tr>
7917 <td>
7918                   <p>Zone Maintenance Statistics</p>
7919                 </td>
7920 <td>
7921                   <p>
7922                     Statistics counters regarding zone maintenance
7923                     operations such as zone transfers.
7924                   </p>
7925                 </td>
7926 </tr>
7927 <tr>
7928 <td>
7929                   <p>Resolver Statistics</p>
7930                 </td>
7931 <td>
7932                   <p>
7933                     Statistics counters about name resolution
7934                     performed in the internal resolver.
7935                     Maintained per view.
7936                   </p>
7937                 </td>
7938 </tr>
7939 <tr>
7940 <td>
7941                   <p>Cache DB RRsets</p>
7942                 </td>
7943 <td>
7944                   <p>
7945                     The number of RRsets per RR type (positive
7946                     or negative) and nonexistent names stored in the
7947                     cache database.
7948                     Maintained per view.
7949                   </p>
7950                 </td>
7951 </tr>
7952 <tr>
7953 <td>
7954                   <p>Socket I/O Statistics</p>
7955                 </td>
7956 <td>
7957                   <p>
7958                     Statistics counters about network related events.
7959                   </p>
7960                 </td>
7961 </tr>
7962 </tbody>
7963 </table></div>
7964 <p>
7965           A subset of Name Server Statistics is collected and shown
7966           per zone for which the server has the authority when
7967           <span><strong class="command">zone-statistics</strong></span> is set to
7968           <strong class="userinput"><code>yes</code></strong>.
7969           These statistics counters are shown with their zone and view
7970           names.
7971           In some cases the view names are omitted for the default view.
7972         </p>
7973 <p>
7974           There are currently two user interfaces to get access to the
7975           statistics.
7976           One is in the plain text format dumped to the file specified
7977           by the <span><strong class="command">statistics-file</strong></span> configuration option.
7978           The other is remotely accessible via a statistics channel
7979           when the <span><strong class="command">statistics-channels</strong></span> statement
7980           is specified in the configuration file
7981           (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>.)
7982         </p>
7983 <div class="sect3" lang="en">
7984 <div class="titlepage"><div><div><h4 class="title">
7985 <a name="statsfile"></a>The Statistics File</h4></div></div></div>
7986 <p>
7987             The text format statistics dump begins with a line, like:
7988           </p>
7989 <p>
7990             <span><strong class="command">+++ Statistics Dump +++ (973798949)</strong></span>
7991           </p>
7992 <p>
7993             The number in parentheses is a standard
7994             Unix-style timestamp, measured as seconds since January 1, 1970.
7995
7996             Following
7997             that line is a set of statistics information, which is categorized
7998             as described above.
7999             Each section begins with a line, like:
8000           </p>
8001 <p>
8002             <span><strong class="command">++ Name Server Statistics ++</strong></span>
8003           </p>
8004 <p>
8005             Each section consists of lines, each containing the statistics
8006             counter value followed by its textual description.
8007             See below for available counters.
8008             For brevity, counters that have a value of 0 are not shown
8009             in the statistics file.
8010           </p>
8011 <p>
8012             The statistics dump ends with the line where the
8013             number is identical to the number in the beginning line; for example:
8014           </p>
8015 <p>
8016             <span><strong class="command">--- Statistics Dump --- (973798949)</strong></span>
8017           </p>
8018 </div>
8019 <div class="sect2" lang="en">
8020 <div class="titlepage"><div><div><h3 class="title">
8021 <a name="statistics_counters"></a>Statistics Counters</h3></div></div></div>
8022 <p>
8023             The following tables summarize statistics counters that
8024             <acronym class="acronym">BIND</acronym> 9 provides.
8025             For each row of the tables, the leftmost column is the
8026             abbreviated symbol name of that counter.
8027             These symbols are shown in the statistics information
8028             accessed via an HTTP statistics channel.
8029             The rightmost column gives the description of the counter,
8030             which is also shown in the statistics file
8031             (but, in this document, possibly with slight modification
8032             for better readability).
8033             Additional notes may also be provided in this column.
8034             When a middle column exists between these two columns,
8035             it gives the corresponding counter name of the
8036             <acronym class="acronym">BIND</acronym> 8 statistics, if applicable.
8037           </p>
8038 <div class="sect3" lang="en">
8039 <div class="titlepage"><div><div><h4 class="title">
8040 <a name="id2595458"></a>Name Server Statistics Counters</h4></div></div></div>
8041 <div class="informaltable"><table border="1">
8042 <colgroup>
8043 <col>
8044 <col>
8045 <col>
8046 </colgroup>
8047 <tbody>
8048 <tr>
8049 <td>
8050                       <p>
8051                         <span class="emphasis"><em>Symbol</em></span>
8052                       </p>
8053                     </td>
8054 <td>
8055                       <p>
8056                         <span class="emphasis"><em>BIND8 Symbol</em></span>
8057                       </p>
8058                     </td>
8059 <td>
8060                       <p>
8061                         <span class="emphasis"><em>Description</em></span>
8062                       </p>
8063                     </td>
8064 </tr>
8065 <tr>
8066 <td>
8067                       <p><span><strong class="command">Requestv4</strong></span></p>
8068                     </td>
8069 <td>
8070                       <p><span><strong class="command">RQ</strong></span></p>
8071                     </td>
8072 <td>
8073                       <p>
8074                         IPv4 requests received.
8075                         Note: this also counts non query requests.
8076                       </p>
8077                     </td>
8078 </tr>
8079 <tr>
8080 <td>
8081                       <p><span><strong class="command">Requestv6</strong></span></p>
8082                     </td>
8083 <td>
8084                       <p><span><strong class="command">RQ</strong></span></p>
8085                     </td>
8086 <td>
8087                       <p>
8088                         IPv6 requests received.
8089                         Note: this also counts non query requests.
8090                       </p>
8091                     </td>
8092 </tr>
8093 <tr>
8094 <td>
8095                       <p><span><strong class="command">ReqEdns0</strong></span></p>
8096                     </td>
8097 <td>
8098                       <p><span><strong class="command"></strong></span></p>
8099                     </td>
8100 <td>
8101                       <p>
8102                         Requests with EDNS(0) received.
8103                       </p>
8104                     </td>
8105 </tr>
8106 <tr>
8107 <td>
8108                       <p><span><strong class="command">ReqBadEDNSVer</strong></span></p>
8109                     </td>
8110 <td>
8111                       <p><span><strong class="command"></strong></span></p>
8112                     </td>
8113 <td>
8114                       <p>
8115                         Requests with unsupported EDNS version received.
8116                       </p>
8117                     </td>
8118 </tr>
8119 <tr>
8120 <td>
8121                       <p><span><strong class="command">ReqTSIG</strong></span></p>
8122                     </td>
8123 <td>
8124                       <p><span><strong class="command"></strong></span></p>
8125                     </td>
8126 <td>
8127                       <p>
8128                         Requests with TSIG received.
8129                       </p>
8130                     </td>
8131 </tr>
8132 <tr>
8133 <td>
8134                       <p><span><strong class="command">ReqSIG0</strong></span></p>
8135                     </td>
8136 <td>
8137                       <p><span><strong class="command"></strong></span></p>
8138                     </td>
8139 <td>
8140                       <p>
8141                         Requests with SIG(0) received.
8142                       </p>
8143                     </td>
8144 </tr>
8145 <tr>
8146 <td>
8147                       <p><span><strong class="command">ReqBadSIG</strong></span></p>
8148                     </td>
8149 <td>
8150                       <p><span><strong class="command"></strong></span></p>
8151                     </td>
8152 <td>
8153                       <p>
8154                         Requests with invalid (TSIG or SIG(0)) signature.
8155                       </p>
8156                     </td>
8157 </tr>
8158 <tr>
8159 <td>
8160                       <p><span><strong class="command">ReqTCP</strong></span></p>
8161                     </td>
8162 <td>
8163                       <p><span><strong class="command">RTCP</strong></span></p>
8164                     </td>
8165 <td>
8166                       <p>
8167                         TCP requests received.
8168                       </p>
8169                     </td>
8170 </tr>
8171 <tr>
8172 <td>
8173                       <p><span><strong class="command">AuthQryRej</strong></span></p>
8174                     </td>
8175 <td>
8176                       <p><span><strong class="command">RUQ</strong></span></p>
8177                     </td>
8178 <td>
8179                       <p>
8180                         Authoritative (non recursive) queries rejected.
8181                       </p>
8182                     </td>
8183 </tr>
8184 <tr>
8185 <td>
8186                       <p><span><strong class="command">RecQryRej</strong></span></p>
8187                     </td>
8188 <td>
8189                       <p><span><strong class="command">RURQ</strong></span></p>
8190                     </td>
8191 <td>
8192                       <p>
8193                         Recursive queries rejected.
8194                       </p>
8195                     </td>
8196 </tr>
8197 <tr>
8198 <td>
8199                       <p><span><strong class="command">XfrRej</strong></span></p>
8200                     </td>
8201 <td>
8202                       <p><span><strong class="command">RUXFR</strong></span></p>
8203                     </td>
8204 <td>
8205                       <p>
8206                         Zone transfer requests rejected.
8207                       </p>
8208                     </td>
8209 </tr>
8210 <tr>
8211 <td>
8212                       <p><span><strong class="command">UpdateRej</strong></span></p>
8213                     </td>
8214 <td>
8215                       <p><span><strong class="command">RUUpd</strong></span></p>
8216                     </td>
8217 <td>
8218                       <p>
8219                         Dynamic update requests rejected.
8220                       </p>
8221                     </td>
8222 </tr>
8223 <tr>
8224 <td>
8225                       <p><span><strong class="command">Response</strong></span></p>
8226                     </td>
8227 <td>
8228                       <p><span><strong class="command">SAns</strong></span></p>
8229                     </td>
8230 <td>
8231                       <p>
8232                         Responses sent.
8233                       </p>
8234                     </td>
8235 </tr>
8236 <tr>
8237 <td>
8238                       <p><span><strong class="command">RespTruncated</strong></span></p>
8239                     </td>
8240 <td>
8241                       <p><span><strong class="command"></strong></span></p>
8242                     </td>
8243 <td>
8244                       <p>
8245                         Truncated responses sent.
8246                       </p>
8247                     </td>
8248 </tr>
8249 <tr>
8250 <td>
8251                       <p><span><strong class="command">RespEDNS0</strong></span></p>
8252                     </td>
8253 <td>
8254                       <p><span><strong class="command"></strong></span></p>
8255                     </td>
8256 <td>
8257                       <p>
8258                         Responses with EDNS(0) sent.
8259                       </p>
8260                     </td>
8261 </tr>
8262 <tr>
8263 <td>
8264                       <p><span><strong class="command">RespTSIG</strong></span></p>
8265                     </td>
8266 <td>
8267                       <p><span><strong class="command"></strong></span></p>
8268                     </td>
8269 <td>
8270                       <p>
8271                         Responses with TSIG sent.
8272                       </p>
8273                     </td>
8274 </tr>
8275 <tr>
8276 <td>
8277                       <p><span><strong class="command">RespSIG0</strong></span></p>
8278                     </td>
8279 <td>
8280                       <p><span><strong class="command"></strong></span></p>
8281                     </td>
8282 <td>
8283                       <p>
8284                         Responses with SIG(0) sent.
8285                       </p>
8286                     </td>
8287 </tr>
8288 <tr>
8289 <td>
8290                       <p><span><strong class="command">QrySuccess</strong></span></p>
8291                     </td>
8292 <td>
8293                       <p><span><strong class="command"></strong></span></p>
8294                     </td>
8295 <td>
8296                       <p>
8297                         Queries resulted in a successful answer.
8298                         This means the query which returns a NOERROR response
8299                         with at least one answer RR.
8300                         This corresponds to the
8301                         <span><strong class="command">success</strong></span> counter
8302                         of previous versions of
8303                         <acronym class="acronym">BIND</acronym> 9.
8304                       </p>
8305                     </td>
8306 </tr>
8307 <tr>
8308 <td>
8309                       <p><span><strong class="command">QryAuthAns</strong></span></p>
8310                     </td>
8311 <td>
8312                       <p><span><strong class="command"></strong></span></p>
8313                     </td>
8314 <td>
8315                       <p>
8316                         Queries resulted in authoritative answer.
8317                       </p>
8318                     </td>
8319 </tr>
8320 <tr>
8321 <td>
8322                       <p><span><strong class="command">QryNoauthAns</strong></span></p>
8323                     </td>
8324 <td>
8325                       <p><span><strong class="command">SNaAns</strong></span></p>
8326                     </td>
8327 <td>
8328                       <p>
8329                         Queries resulted in non authoritative answer.
8330                       </p>
8331                     </td>
8332 </tr>
8333 <tr>
8334 <td>
8335                       <p><span><strong class="command">QryReferral</strong></span></p>
8336                     </td>
8337 <td>
8338                       <p><span><strong class="command"></strong></span></p>
8339                     </td>
8340 <td>
8341                       <p>
8342                         Queries resulted in referral answer.
8343                         This corresponds to the
8344                         <span><strong class="command">referral</strong></span> counter
8345                         of previous versions of
8346                         <acronym class="acronym">BIND</acronym> 9.
8347                       </p>
8348                     </td>
8349 </tr>
8350 <tr>
8351 <td>
8352                       <p><span><strong class="command">QryNxrrset</strong></span></p>
8353                     </td>
8354 <td>
8355                       <p><span><strong class="command"></strong></span></p>
8356                     </td>
8357 <td>
8358                       <p>
8359                         Queries resulted in NOERROR responses with no data.
8360                         This corresponds to the
8361                         <span><strong class="command">nxrrset</strong></span> counter
8362                         of previous versions of
8363                         <acronym class="acronym">BIND</acronym> 9.
8364                       </p>
8365                     </td>
8366 </tr>
8367 <tr>
8368 <td>
8369                       <p><span><strong class="command">QrySERVFAIL</strong></span></p>
8370                     </td>
8371 <td>
8372                       <p><span><strong class="command">SFail</strong></span></p>
8373                     </td>
8374 <td>
8375                       <p>
8376                         Queries resulted in SERVFAIL.
8377                       </p>
8378                     </td>
8379 </tr>
8380 <tr>
8381 <td>
8382                       <p><span><strong class="command">QryFORMERR</strong></span></p>
8383                     </td>
8384 <td>
8385                       <p><span><strong class="command">SFErr</strong></span></p>
8386                     </td>
8387 <td>
8388                       <p>
8389                         Queries resulted in FORMERR.
8390                       </p>
8391                     </td>
8392 </tr>
8393 <tr>
8394 <td>
8395                       <p><span><strong class="command">QryNXDOMAIN</strong></span></p>
8396                     </td>
8397 <td>
8398                       <p><span><strong class="command">SNXD</strong></span></p>
8399                     </td>
8400 <td>
8401                       <p>
8402                         Queries resulted in NXDOMAIN.
8403                         This corresponds to the
8404                         <span><strong class="command">nxdomain</strong></span> counter
8405                         of previous versions of
8406                         <acronym class="acronym">BIND</acronym> 9.
8407                       </p>
8408                     </td>
8409 </tr>
8410 <tr>
8411 <td>
8412                       <p><span><strong class="command">QryRecursion</strong></span></p>
8413                     </td>
8414 <td>
8415                       <p><span><strong class="command">RFwdQ</strong></span></p>
8416                     </td>
8417 <td>
8418                       <p>
8419                         Queries which caused the server
8420                         to perform recursion in order to find the final answer.
8421                         This corresponds to the
8422                         <span><strong class="command">recursion</strong></span> counter
8423                         of previous versions of
8424                         <acronym class="acronym">BIND</acronym> 9.
8425                       </p>
8426                     </td>
8427 </tr>
8428 <tr>
8429 <td>
8430                       <p><span><strong class="command">QryDuplicate</strong></span></p>
8431                     </td>
8432 <td>
8433                       <p><span><strong class="command">RDupQ</strong></span></p>
8434                     </td>
8435 <td>
8436                       <p>
8437                         Queries which the server attempted to
8438                         recurse but discovered an existing query with the same
8439                         IP address, port, query ID, name, type and class
8440                         already being processed.
8441                         This corresponds to the
8442                         <span><strong class="command">duplicate</strong></span> counter
8443                         of previous versions of
8444                         <acronym class="acronym">BIND</acronym> 9.
8445                       </p>
8446                     </td>
8447 </tr>
8448 <tr>
8449 <td>
8450                       <p><span><strong class="command">QryDropped</strong></span></p>
8451                     </td>
8452 <td>
8453                       <p><span><strong class="command"></strong></span></p>
8454                     </td>
8455 <td>
8456                       <p>
8457                         Recursive queries for which the server
8458                         discovered an excessive number of existing
8459                         recursive queries for the same name, type and
8460                         class and were subsequently dropped.
8461                         This is the number of dropped queries due to
8462                         the reason explained with the
8463                         <span><strong class="command">clients-per-query</strong></span>
8464                         and
8465                         <span><strong class="command">max-clients-per-query</strong></span>
8466                         options
8467                         (see the description about
8468                         <a href="Bv9ARM.ch06.html#clients-per-query"><span><strong class="command">clients-per-query</strong></span></a>.)
8469                         This corresponds to the
8470                         <span><strong class="command">dropped</strong></span> counter
8471                         of previous versions of
8472                         <acronym class="acronym">BIND</acronym> 9.
8473                       </p>
8474                     </td>
8475 </tr>
8476 <tr>
8477 <td>
8478                       <p><span><strong class="command">QryFailure</strong></span></p>
8479                     </td>
8480 <td>
8481                       <p><span><strong class="command"></strong></span></p>
8482                     </td>
8483 <td>
8484                       <p>
8485                         Other query failures.
8486                         This corresponds to the
8487                         <span><strong class="command">failure</strong></span> counter
8488                         of previous versions of
8489                         <acronym class="acronym">BIND</acronym> 9.
8490                         Note: this counter is provided mainly for
8491                         backward compatibility with the previous versions.
8492                         Normally a more fine-grained counters such as
8493                         <span><strong class="command">AuthQryRej</strong></span> and
8494                         <span><strong class="command">RecQryRej</strong></span>
8495                         that would also fall into this counter are provided,
8496                         and so this counter would not be of much
8497                         interest in practice.
8498                       </p>
8499                     </td>
8500 </tr>
8501 <tr>
8502 <td>
8503                       <p><span><strong class="command">XfrReqDone</strong></span></p>
8504                     </td>
8505 <td>
8506                       <p><span><strong class="command"></strong></span></p>
8507                     </td>
8508 <td>
8509                       <p>
8510                         Requested zone transfers completed.
8511                       </p>
8512                     </td>
8513 </tr>
8514 <tr>
8515 <td>
8516                       <p><span><strong class="command">UpdateReqFwd</strong></span></p>
8517                     </td>
8518 <td>
8519                       <p><span><strong class="command"></strong></span></p>
8520                     </td>
8521 <td>
8522                       <p>
8523                         Update requests forwarded.
8524                       </p>
8525                     </td>
8526 </tr>
8527 <tr>
8528 <td>
8529                       <p><span><strong class="command">UpdateRespFwd</strong></span></p>
8530                     </td>
8531 <td>
8532                       <p><span><strong class="command"></strong></span></p>
8533                     </td>
8534 <td>
8535                       <p>
8536                         Update responses forwarded.
8537                       </p>
8538                     </td>
8539 </tr>
8540 <tr>
8541 <td>
8542                       <p><span><strong class="command">UpdateFwdFail</strong></span></p>
8543                     </td>
8544 <td>
8545                       <p><span><strong class="command"></strong></span></p>
8546                     </td>
8547 <td>
8548                       <p>
8549                         Dynamic update forward failed.
8550                       </p>
8551                     </td>
8552 </tr>
8553 <tr>
8554 <td>
8555                       <p><span><strong class="command">UpdateDone</strong></span></p>
8556                     </td>
8557 <td>
8558                       <p><span><strong class="command"></strong></span></p>
8559                     </td>
8560 <td>
8561                       <p>
8562                         Dynamic updates completed.
8563                       </p>
8564                     </td>
8565 </tr>
8566 <tr>
8567 <td>
8568                       <p><span><strong class="command">UpdateFail</strong></span></p>
8569                     </td>
8570 <td>
8571                       <p><span><strong class="command"></strong></span></p>
8572                     </td>
8573 <td>
8574                       <p>
8575                         Dynamic updates failed.
8576                       </p>
8577                     </td>
8578 </tr>
8579 <tr>
8580 <td>
8581                       <p><span><strong class="command">UpdateBadPrereq</strong></span></p>
8582                     </td>
8583 <td>
8584                       <p><span><strong class="command"></strong></span></p>
8585                     </td>
8586 <td>
8587                       <p>
8588                         Dynamic updates rejected due to prerequisite failure.
8589                       </p>
8590                     </td>
8591 </tr>
8592 </tbody>
8593 </table></div>
8594 </div>
8595 <div class="sect3" lang="en">
8596 <div class="titlepage"><div><div><h4 class="title">
8597 <a name="id2596931"></a>Zone Maintenance Statistics Counters</h4></div></div></div>
8598 <div class="informaltable"><table border="1">
8599 <colgroup>
8600 <col>
8601 <col>
8602 </colgroup>
8603 <tbody>
8604 <tr>
8605 <td>
8606                       <p>
8607                         <span class="emphasis"><em>Symbol</em></span>
8608                       </p>
8609                     </td>
8610 <td>
8611                       <p>
8612                         <span class="emphasis"><em>Description</em></span>
8613                       </p>
8614                     </td>
8615 </tr>
8616 <tr>
8617 <td>
8618                       <p><span><strong class="command">NotifyOutv4</strong></span></p>
8619                     </td>
8620 <td>
8621                       <p>
8622                         IPv4 notifies sent.
8623                       </p>
8624                     </td>
8625 </tr>
8626 <tr>
8627 <td>
8628                       <p><span><strong class="command">NotifyOutv6</strong></span></p>
8629                     </td>
8630 <td>
8631                       <p>
8632                         IPv6 notifies sent.
8633                       </p>
8634                     </td>
8635 </tr>
8636 <tr>
8637 <td>
8638                       <p><span><strong class="command">NotifyInv4</strong></span></p>
8639                     </td>
8640 <td>
8641                       <p>
8642                         IPv4 notifies received.
8643                       </p>
8644                     </td>
8645 </tr>
8646 <tr>
8647 <td>
8648                       <p><span><strong class="command">NotifyInv6</strong></span></p>
8649                     </td>
8650 <td>
8651                       <p>
8652                         IPv6 notifies received.
8653                       </p>
8654                     </td>
8655 </tr>
8656 <tr>
8657 <td>
8658                       <p><span><strong class="command">NotifyRej</strong></span></p>
8659                     </td>
8660 <td>
8661                       <p>
8662                         Incoming notifies rejected.
8663                       </p>
8664                     </td>
8665 </tr>
8666 <tr>
8667 <td>
8668                       <p><span><strong class="command">SOAOutv4</strong></span></p>
8669                     </td>
8670 <td>
8671                       <p>
8672                         IPv4 SOA queries sent.
8673                       </p>
8674                     </td>
8675 </tr>
8676 <tr>
8677 <td>
8678                       <p><span><strong class="command">SOAOutv6</strong></span></p>
8679                     </td>
8680 <td>
8681                       <p>
8682                         IPv6 SOA queries sent.
8683                       </p>
8684                     </td>
8685 </tr>
8686 <tr>
8687 <td>
8688                       <p><span><strong class="command">AXFRReqv4</strong></span></p>
8689                     </td>
8690 <td>
8691                       <p>
8692                         IPv4 AXFR requested.
8693                       </p>
8694                     </td>
8695 </tr>
8696 <tr>
8697 <td>
8698                       <p><span><strong class="command">AXFRReqv6</strong></span></p>
8699                     </td>
8700 <td>
8701                       <p>
8702                         IPv6 AXFR requested.
8703                       </p>
8704                     </td>
8705 </tr>
8706 <tr>
8707 <td>
8708                       <p><span><strong class="command">IXFRReqv4</strong></span></p>
8709                     </td>
8710 <td>
8711                       <p>
8712                         IPv4 IXFR requested.
8713                       </p>
8714                     </td>
8715 </tr>
8716 <tr>
8717 <td>
8718                       <p><span><strong class="command">IXFRReqv6</strong></span></p>
8719                     </td>
8720 <td>
8721                       <p>
8722                         IPv6 IXFR requested.
8723                       </p>
8724                     </td>
8725 </tr>
8726 <tr>
8727 <td>
8728                       <p><span><strong class="command">XfrSuccess</strong></span></p>
8729                     </td>
8730 <td>
8731                       <p>
8732                         Zone transfer requests succeeded.
8733                       </p>
8734                     </td>
8735 </tr>
8736 <tr>
8737 <td>
8738                       <p><span><strong class="command">XfrFail</strong></span></p>
8739                     </td>
8740 <td>
8741                       <p>
8742                         Zone transfer requests failed.
8743                       </p>
8744                     </td>
8745 </tr>
8746 </tbody>
8747 </table></div>
8748 </div>
8749 <div class="sect3" lang="en">
8750 <div class="titlepage"><div><div><h4 class="title">
8751 <a name="id2597314"></a>Resolver Statistics Counters</h4></div></div></div>
8752 <div class="informaltable"><table border="1">
8753 <colgroup>
8754 <col>
8755 <col>
8756 <col>
8757 </colgroup>
8758 <tbody>
8759 <tr>
8760 <td>
8761                       <p>
8762                         <span class="emphasis"><em>Symbol</em></span>
8763                       </p>
8764                     </td>
8765 <td>
8766                       <p>
8767                         <span class="emphasis"><em>BIND8 Symbol</em></span>
8768                       </p>
8769                     </td>
8770 <td>
8771                       <p>
8772                         <span class="emphasis"><em>Description</em></span>
8773                       </p>
8774                     </td>
8775 </tr>
8776 <tr>
8777 <td>
8778                       <p><span><strong class="command">Queryv4</strong></span></p>
8779                     </td>
8780 <td>
8781                       <p><span><strong class="command">SFwdQ</strong></span></p>
8782                     </td>
8783 <td>
8784                       <p>
8785                         IPv4 queries sent.
8786                       </p>
8787                     </td>
8788 </tr>
8789 <tr>
8790 <td>
8791                       <p><span><strong class="command">Queryv6</strong></span></p>
8792                     </td>
8793 <td>
8794                       <p><span><strong class="command">SFwdQ</strong></span></p>
8795                     </td>
8796 <td>
8797                       <p>
8798                         IPv6 queries sent.
8799                       </p>
8800                     </td>
8801 </tr>
8802 <tr>
8803 <td>
8804                       <p><span><strong class="command">Responsev4</strong></span></p>
8805                     </td>
8806 <td>
8807                       <p><span><strong class="command">RR</strong></span></p>
8808                     </td>
8809 <td>
8810                       <p>
8811                         IPv4 responses received.
8812                       </p>
8813                     </td>
8814 </tr>
8815 <tr>
8816 <td>
8817                       <p><span><strong class="command">Responsev6</strong></span></p>
8818                     </td>
8819 <td>
8820                       <p><span><strong class="command">RR</strong></span></p>
8821                     </td>
8822 <td>
8823                       <p>
8824                         IPv6 responses received.
8825                       </p>
8826                     </td>
8827 </tr>
8828 <tr>
8829 <td>
8830                       <p><span><strong class="command">NXDOMAIN</strong></span></p>
8831                     </td>
8832 <td>
8833                       <p><span><strong class="command">RNXD</strong></span></p>
8834                     </td>
8835 <td>
8836                       <p>
8837                         NXDOMAIN received.
8838                       </p>
8839                     </td>
8840 </tr>
8841 <tr>
8842 <td>
8843                       <p><span><strong class="command">SERVFAIL</strong></span></p>
8844                     </td>
8845 <td>
8846                       <p><span><strong class="command">RFail</strong></span></p>
8847                     </td>
8848 <td>
8849                       <p>
8850                         SERVFAIL received.
8851                       </p>
8852                     </td>
8853 </tr>
8854 <tr>
8855 <td>
8856                       <p><span><strong class="command">FORMERR</strong></span></p>
8857                     </td>
8858 <td>
8859                       <p><span><strong class="command">RFErr</strong></span></p>
8860                     </td>
8861 <td>
8862                       <p>
8863                         FORMERR received.
8864                       </p>
8865                     </td>
8866 </tr>
8867 <tr>
8868 <td>
8869                       <p><span><strong class="command">OtherError</strong></span></p>
8870                     </td>
8871 <td>
8872                       <p><span><strong class="command">RErr</strong></span></p>
8873                     </td>
8874 <td>
8875                       <p>
8876                         Other errors received.
8877                       </p>
8878                     </td>
8879 </tr>
8880 <tr>
8881 <td>
8882                       <p><span><strong class="command">EDNS0Fail</strong></span></p>
8883                                                  </td>
8884 <td>
8885                       <p><span><strong class="command"></strong></span></p>
8886                     </td>
8887 <td>
8888                       <p>
8889                         EDNS(0) query failures.
8890                       </p>
8891                     </td>
8892 </tr>
8893 <tr>
8894 <td>
8895                       <p><span><strong class="command">Mismatch</strong></span></p>
8896                     </td>
8897 <td>
8898                       <p><span><strong class="command">RDupR</strong></span></p>
8899                     </td>
8900 <td>
8901                       <p>
8902                         Mismatch responses received.
8903                       </p>
8904                     </td>
8905 </tr>
8906 <tr>
8907 <td>
8908                       <p><span><strong class="command">Truncated</strong></span></p>
8909                     </td>
8910 <td>
8911                       <p><span><strong class="command"></strong></span></p>
8912                     </td>
8913 <td>
8914                       <p>
8915                         Truncated responses received.
8916                       </p>
8917                     </td>
8918 </tr>
8919 <tr>
8920 <td>
8921                       <p><span><strong class="command">Lame</strong></span></p>
8922                     </td>
8923 <td>
8924                       <p><span><strong class="command">RLame</strong></span></p>
8925                     </td>
8926 <td>
8927                       <p>
8928                         Lame delegations received.
8929                       </p>
8930                     </td>
8931 </tr>
8932 <tr>
8933 <td>
8934                       <p><span><strong class="command">Retry</strong></span></p>
8935                     </td>
8936 <td>
8937                       <p><span><strong class="command">SDupQ</strong></span></p>
8938                     </td>
8939 <td>
8940                       <p>
8941                         Query retries performed.
8942                       </p>
8943                     </td>
8944 </tr>
8945 <tr>
8946 <td>
8947                       <p><span><strong class="command">QueryAbort</strong></span></p>
8948                     </td>
8949 <td>
8950                       <p><span><strong class="command"></strong></span></p>
8951                     </td>
8952 <td>
8953                       <p>
8954                         Queries aborted due to quota control.
8955                       </p>
8956                     </td>
8957 </tr>
8958 <tr>
8959 <td>
8960                       <p><span><strong class="command">QuerySockFail</strong></span></p>
8961                     </td>
8962 <td>
8963                       <p><span><strong class="command"></strong></span></p>
8964                     </td>
8965 <td>
8966                       <p>
8967                         Failures in opening query sockets.
8968                         One common reason for such failures is a
8969                         failure of opening a new socket due to a
8970                         limitation on file descriptors.
8971                       </p>
8972                     </td>
8973 </tr>
8974 <tr>
8975 <td>
8976                       <p><span><strong class="command">QueryTimeout</strong></span></p>
8977                     </td>
8978 <td>
8979                       <p><span><strong class="command"></strong></span></p>
8980                     </td>
8981 <td>
8982                       <p>
8983                         Query timeouts.
8984                       </p>
8985                     </td>
8986 </tr>
8987 <tr>
8988 <td>
8989                       <p><span><strong class="command">GlueFetchv4</strong></span></p>
8990                     </td>
8991 <td>
8992                       <p><span><strong class="command">SSysQ</strong></span></p>
8993                     </td>
8994 <td>
8995                       <p>
8996                         IPv4 NS address fetches invoked.
8997                       </p>
8998                     </td>
8999 </tr>
9000 <tr>
9001 <td>
9002                       <p><span><strong class="command">GlueFetchv6</strong></span></p>
9003                     </td>
9004 <td>
9005                       <p><span><strong class="command">SSysQ</strong></span></p>
9006                     </td>
9007 <td>
9008                       <p>
9009                         IPv6 NS address fetches invoked.
9010                       </p>
9011                     </td>
9012 </tr>
9013 <tr>
9014 <td>
9015                       <p><span><strong class="command">GlueFetchv4Fail</strong></span></p>
9016                     </td>
9017 <td>
9018                       <p><span><strong class="command"></strong></span></p>
9019                     </td>
9020 <td>
9021                       <p>
9022                         IPv4 NS address fetch failed.
9023                       </p>
9024                     </td>
9025 </tr>
9026 <tr>
9027 <td>
9028                       <p><span><strong class="command">GlueFetchv6Fail</strong></span></p>
9029                     </td>
9030 <td>
9031                       <p><span><strong class="command"></strong></span></p>
9032                     </td>
9033 <td>
9034                       <p>
9035                         IPv6 NS address fetch failed.
9036                       </p>
9037                     </td>
9038 </tr>
9039 <tr>
9040 <td>
9041                       <p><span><strong class="command">ValAttempt</strong></span></p>
9042                     </td>
9043 <td>
9044                       <p><span><strong class="command"></strong></span></p>
9045                     </td>
9046 <td>
9047                       <p>
9048                         DNSSEC validation attempted.
9049                       </p>
9050                     </td>
9051 </tr>
9052 <tr>
9053 <td>
9054                       <p><span><strong class="command">ValOk</strong></span></p>
9055                     </td>
9056 <td>
9057                       <p><span><strong class="command"></strong></span></p>
9058                     </td>
9059 <td>
9060                       <p>
9061                         DNSSEC validation succeeded.
9062                       </p>
9063                     </td>
9064 </tr>
9065 <tr>
9066 <td>
9067                       <p><span><strong class="command">ValNegOk</strong></span></p>
9068                     </td>
9069 <td>
9070                       <p><span><strong class="command"></strong></span></p>
9071                     </td>
9072 <td>
9073                       <p>
9074                         DNSSEC validation on negative information succeeded.
9075                       </p>
9076                     </td>
9077 </tr>
9078 <tr>
9079 <td>
9080                       <p><span><strong class="command">ValFail</strong></span></p>
9081                     </td>
9082 <td>
9083                       <p><span><strong class="command"></strong></span></p>
9084                     </td>
9085 <td>
9086                       <p>
9087                         DNSSEC validation failed.
9088                       </p>
9089                     </td>
9090 </tr>
9091 <tr>
9092 <td>
9093                       <p><span><strong class="command">QryRTTnn</strong></span></p>
9094                     </td>
9095 <td>
9096                       <p><span><strong class="command"></strong></span></p>
9097                     </td>
9098 <td>
9099                       <p>
9100                         Frequency table on round trip times (RTTs) of
9101                         queries.
9102                         Each <span><strong class="command">nn</strong></span> specifies the corresponding
9103                         frequency.
9104                         In the sequence of
9105                         <span><strong class="command">nn_1</strong></span>,
9106                         <span><strong class="command">nn_2</strong></span>,
9107                         ...,
9108                         <span><strong class="command">nn_m</strong></span>,
9109                         the value of <span><strong class="command">nn_i</strong></span> is the
9110                         number of queries whose RTTs are between
9111                         <span><strong class="command">nn_(i-1)</strong></span> (inclusive) and
9112                         <span><strong class="command">nn_i</strong></span> (exclusive) milliseconds.
9113                         For the sake of convenience we define
9114                         <span><strong class="command">nn_0</strong></span> to be 0.
9115                         The last entry should be represented as
9116                         <span><strong class="command">nn_m+</strong></span>, which means the
9117                         number of queries whose RTTs are equal to or over
9118                         <span><strong class="command">nn_m</strong></span> milliseconds.
9119                       </p>
9120                     </td>
9121 </tr>
9122 </tbody>
9123 </table></div>
9124 </div>
9125 <div class="sect3" lang="en">
9126 <div class="titlepage"><div><div><h4 class="title">
9127 <a name="id2598332"></a>Socket I/O Statistics Counters</h4></div></div></div>
9128 <p>
9129               Socket I/O statistics counters are defined per socket
9130               types, which are
9131               <span><strong class="command">UDP4</strong></span> (UDP/IPv4),
9132               <span><strong class="command">UDP6</strong></span> (UDP/IPv6),
9133               <span><strong class="command">TCP4</strong></span> (TCP/IPv4),
9134               <span><strong class="command">TCP6</strong></span> (TCP/IPv6),
9135               <span><strong class="command">Unix</strong></span> (Unix Domain), and
9136               <span><strong class="command">FDwatch</strong></span> (sockets opened outside the
9137               socket module).
9138               In the following table <span><strong class="command">&lt;TYPE&gt;</strong></span>
9139               represents a socket type.
9140               Not all counters are available for all socket types;
9141               exceptions are noted in the description field.
9142             </p>
9143 <div class="informaltable"><table border="1">
9144 <colgroup>
9145 <col>
9146 <col>
9147 </colgroup>
9148 <tbody>
9149 <tr>
9150 <td>
9151                       <p>
9152                         <span class="emphasis"><em>Symbol</em></span>
9153                       </p>
9154                     </td>
9155 <td>
9156                       <p>
9157                         <span class="emphasis"><em>Description</em></span>
9158                       </p>
9159                     </td>
9160 </tr>
9161 <tr>
9162 <td>
9163                       <p><span><strong class="command">&lt;TYPE&gt;Open</strong></span></p>
9164                     </td>
9165 <td>
9166                       <p>
9167                         Sockets opened successfully.
9168                         This counter is not applicable to the
9169                         <span><strong class="command">FDwatch</strong></span> type.
9170                       </p>
9171                     </td>
9172 </tr>
9173 <tr>
9174 <td>
9175                       <p><span><strong class="command">&lt;TYPE&gt;OpenFail</strong></span></p>
9176                     </td>
9177 <td>
9178                       <p>
9179                         Failures of opening sockets.
9180                         This counter is not applicable to the
9181                         <span><strong class="command">FDwatch</strong></span> type.
9182                       </p>
9183                     </td>
9184 </tr>
9185 <tr>
9186 <td>
9187                       <p><span><strong class="command">&lt;TYPE&gt;Close</strong></span></p>
9188                     </td>
9189 <td>
9190                       <p>
9191                         Sockets closed.
9192                       </p>
9193                     </td>
9194 </tr>
9195 <tr>
9196 <td>
9197                       <p><span><strong class="command">&lt;TYPE&gt;BindFail</strong></span></p>
9198                     </td>
9199 <td>
9200                       <p>
9201                         Failures of binding sockets.
9202                       </p>
9203                     </td>
9204 </tr>
9205 <tr>
9206 <td>
9207                       <p><span><strong class="command">&lt;TYPE&gt;ConnFail</strong></span></p>
9208                     </td>
9209 <td>
9210                       <p>
9211                         Failures of connecting sockets.
9212                       </p>
9213                     </td>
9214 </tr>
9215 <tr>
9216 <td>
9217                       <p><span><strong class="command">&lt;TYPE&gt;Conn</strong></span></p>
9218                     </td>
9219 <td>
9220                       <p>
9221                         Connections established successfully.
9222                       </p>
9223                     </td>
9224 </tr>
9225 <tr>
9226 <td>
9227                       <p><span><strong class="command">&lt;TYPE&gt;AcceptFail</strong></span></p>
9228                     </td>
9229 <td>
9230                       <p>
9231                         Failures of accepting incoming connection requests.
9232                         This counter is not applicable to the
9233                         <span><strong class="command">UDP</strong></span> and
9234                         <span><strong class="command">FDwatch</strong></span> types.
9235                       </p>
9236                     </td>
9237 </tr>
9238 <tr>
9239 <td>
9240                       <p><span><strong class="command">&lt;TYPE&gt;Accept</strong></span></p>
9241                     </td>
9242 <td>
9243                       <p>
9244                         Incoming connections successfully accepted.
9245                         This counter is not applicable to the
9246                         <span><strong class="command">UDP</strong></span> and
9247                         <span><strong class="command">FDwatch</strong></span> types.
9248                       </p>
9249                     </td>
9250 </tr>
9251 <tr>
9252 <td>
9253                       <p><span><strong class="command">&lt;TYPE&gt;SendErr</strong></span></p>
9254                     </td>
9255 <td>
9256                       <p>
9257                         Errors in socket send operations.
9258                         This counter corresponds
9259                         to <span><strong class="command">SErr</strong></span> counter of
9260                         <span><strong class="command">BIND</strong></span> 8.
9261                       </p>
9262                     </td>
9263 </tr>
9264 <tr>
9265 <td>
9266                       <p><span><strong class="command">&lt;TYPE&gt;RecvErr</strong></span></p>
9267                     </td>
9268 <td>
9269                       <p>
9270                         Errors in socket receive operations.
9271                         This includes errors of send operations on a
9272                         connected UDP socket notified by an ICMP error
9273                         message.
9274                       </p>
9275                     </td>
9276 </tr>
9277 </tbody>
9278 </table></div>
9279 </div>
9280 <div class="sect3" lang="en">
9281 <div class="titlepage"><div><div><h4 class="title">
9282 <a name="id2598842"></a>Compatibility with <span class="emphasis"><em>BIND</em></span> 8 Counters</h4></div></div></div>
9283 <p>
9284               Most statistics counters that were available
9285               in <span><strong class="command">BIND</strong></span> 8 are also supported in
9286               <span><strong class="command">BIND</strong></span> 9 as shown in the above tables.
9287               Here are notes about other counters that do not appear
9288               in these tables.
9289             </p>
9290 <div class="variablelist"><dl>
9291 <dt><span class="term"><span><strong class="command">RFwdR,SFwdR</strong></span></span></dt>
9292 <dd><p>
9293                     These counters are not supported
9294                     because <span><strong class="command">BIND</strong></span> 9 does not adopt
9295                     the notion of <span class="emphasis"><em>forwarding</em></span>
9296                     as <span><strong class="command">BIND</strong></span> 8 did.
9297                   </p></dd>
9298 <dt><span class="term"><span><strong class="command">RAXFR</strong></span></span></dt>
9299 <dd><p>
9300                     This counter is accessible in the Incoming Queries section.
9301                   </p></dd>
9302 <dt><span class="term"><span><strong class="command">RIQ</strong></span></span></dt>
9303 <dd><p>
9304                     This counter is accessible in the Incoming Requests section.
9305                   </p></dd>
9306 <dt><span class="term"><span><strong class="command">ROpts</strong></span></span></dt>
9307 <dd><p>
9308                     This counter is not supported
9309                     because <span><strong class="command">BIND</strong></span> 9 does not care
9310                     about IP options in the first place.
9311                   </p></dd>
9312 </dl></div>
9313 </div>
9314 </div>
9315 </div>
9316 </div>
9317 <div class="navfooter">
9318 <hr>
9319 <table width="100%" summary="Navigation footer">
9320 <tr>
9321 <td width="40%" align="left">
9322 <a accesskey="p" href="Bv9ARM.ch05.html">Prev</a> </td>
9323 <td width="20%" align="center"> </td>
9324 <td width="40%" align="right"> <a accesskey="n" href="Bv9ARM.ch07.html">Next</a>
9325 </td>
9326 </tr>
9327 <tr>
9328 <td width="40%" align="left" valign="top">Chapter 5. The <acronym class="acronym">BIND</acronym> 9 Lightweight Resolver </td>
9329 <td width="20%" align="center"><a accesskey="h" href="Bv9ARM.html">Home</a></td>
9330 <td width="40%" align="right" valign="top"> Chapter 7. <acronym class="acronym">BIND</acronym> 9 Security Considerations</td>
9331 </tr>
9332 </table>
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