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5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark AndrewsSection 6. BIND 9 Configuration Reference</H1>
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark AndrewsBIND 9 configuration is broadly similar to BIND 8.x; however, there are a few new areas of configuration, such as views. BIND 8.x configuration files should work with few alterations in BIND 9, although more complex configurations should be reviewed to check if they can be more efficiently implemented using the new features found in BIND 9.</P>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan HuntBIND 4 configuration files can be converted to the new format using the shell script<BR>
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark AndrewsConfiguration File Elements</H3>
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark AndrewsFollowing is a list of elements used throughout the BIND configuration file documentation:</P>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Huntacl_name</EM>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Huntaddress_match_list</EM>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt statement.</P>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Huntaddress_match_list</EM>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Huntacl_name</EM>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Hunt elements, as described in <A HREF="Bv9ARM.6.html#28183" CLASS="XRef">
d856585f5fe37cc2ea82115c10339578d2b517b1Automatic UpdaterAddress Match Lists</A>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Huntdomain_name</EM>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan HuntA quoted string which will be used as a DNS name, for example "<EM CLASS="URL">
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Huntdotted_decimal</EM>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan HuntOne or more integers valued 0 through 255 separated only by dots (`.'), such as <CODE CLASS="Program-Process">
990d0e893f5b70e735cdf990af66e9ec6e91fa78Tinderbox User89.123.45.67</CODE>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Huntip4_addr</EM>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan HuntAn IPv4 address with exactly four elements in <EM CLASS="variable">
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Huntdotted_decimal</EM>
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrews notation.</P>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Huntip6_addr</EM>
14a656f94b1fd0ababd84a772228dfa52276ba15Evan HuntAn IPv6 address, such as <CODE CLASS="Program-Process">
14a656f94b1fd0ababd84a772228dfa52276ba15Evan Huntfe80::200:f8ff:fe01:9742</CODE>
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrewsip4_addr</EM>
5a4557e8de2951a2796676b5ec4b6a90caa5be14Mark Andrewsip6_addr</EM>
is limited to 0 through 65535, with values below 1024 typically restricted to root-owned processes. In some cases an asterisk (`*') character can be used as a placeholder to select a random high-numbered port.</P>
, followed by a slash (`/') and then the number of bits in the netmask. For example, <CODE CLASS="Program-Process">
A non-negative integer with an entire range limited by the range of a C language signed integer (2,147,483,647 on a machine with 32 bit integers). Its acceptable value might further be limited by the context in which it is used.</P>
Integer storage overflow is currently silently ignored during conversion of scaled values, resulting in values less than intended, possibly even negative. Using <EM CLASS="variable">
<CODE><STRONG>address_match_list</STRONG></CODE> <EM>=</EM> <VAR>address_match_list_element</VAR> <EM>;</EM><BR>
<CODE>key</CODE> <VAR>key_id</VAR> <EM>|</EM> <VAR>acl_name</VAR> <EM>| {</EM> <VAR>address_match_list</VAR> <EM>} )</EM>
Address match lists are primarily used to determine access control for various server operations. They are also used to define priorities for querying other nameservers and to set the addresses on which <CODE CLASS="Program-Process">
will listen for queries. The elements which constitute an address match list can be any of the following:</P>
Elements can be negated with a leading exclamation mark (`!') and the match list names "any," "none," "localhost" and "localnets" are predefined. More information on those names can be found in the description of the acl statement.</P>
The addition of the key clause made the name of this syntactic element something of a misnomer, since security keys can be used to validate access without regard to a host or network address. Nonetheless, the term "address match list" is still used throughout the documentation.</P>
When a given IP address or prefix is compared to an address match list, the list is traversed in order until an element matches. The interpretation of a match depends on whether the list is being used for access control, defining listen-on ports, or as a topology, and whether the element was negated.</P>
When used as an access control list, a non-negated match allows access and a negated match denies access. If there is no match, access is denied. The clauses <CODE CLASS="Program-Process">
all use address match lists this. Similarly, the listen-on option will cause the server to not accept queries on any of the machine's addresses which do not match the list.</P>
When used with the topology clause, a non-negated match returns a distance based on its position on the list (the closer the match is to the start of the list, the shorter the distance is between it and the server). A negated match will be assigned the maximum distance from the server. If there is no match, the address will get a distance which is further than any non-negated list element, and closer than any negated element.</P>
Because of the first-match aspect of the algorithm, an element that defines a subset of another element in the list should come before the broader element, regardless of whether either is negated. For example, in<BR>
the 1.2.3.13 element is completely useless because the algorithm will match any lookup for 1.2.3.13 to the 1.2.3/24 element. Using <CODE CLASS="Program-Process">
fixes that problem by having 1.2.3.13 blocked by the negation but all other 1.2.3.* hosts fall through.</P>
The BIND 9 comment syntax allows for comments to appear anywhere that white space may appear in a BIND configuration file. To appeal to programmers of all kinds, they can be written in C, C++, or shell/perl constructs.</P>
C-style comments start with the two characters /* (slash, star) and end with */ (star, slash). Because they are completely delimited with these characters, they can be used to comment only a portion of a line or to span multiple lines.</P>
C-style comments cannot be nested. For example, the following is not valid because the entire comment ends with the first */:</P>
C++-style comments start with the two characters // (slash, slash) and continue to the end of the physical line. They cannot be continued across multiple physical lines; to have one logical comment span multiple lines, each line must use the // pair.</P>
Shell-style (or perl-style, if you prefer) comments start with the character # (number sign) and continue to the end of the physical line, as in C++ comments.</P>
WARNING: you cannot use the semicolon (`;') character to start a comment such as you would in a zone file. The semicolon indicates the end of a configuration statement.</P>
A BIND 9 configuration consists of statements and comments. Statements end with a semicolon. Statements and comments are the only elements that can appear without enclosing braces. Many statements contain a block of substatements, which are also terminated with a semicolon.</P>
<CODE CLASS="Program-Process">acl </CODE><EM CLASS="variable">acl-name</EM><CODE CLASS="Program-Process"> {</CODE>
statement assigns a symbolic name to an address match list. It gets its name from a primary use of address match lists: Access Control Lists (ACLs).</P>
<EM CLASS="Optional-meta-syntax">[ </EM><CODE CLASS="Program-Process">inet</CODE> <EM CLASS="Optional-meta-syntax">(</EM><EM CLASS="variable">ip_addr</EM><EM CLASS="Optional-meta-syntax">|</EM><EM CLASS="variable">*</EM><EM CLASS="Optional-meta-syntax">)</EM> <CODE CLASS="Program-Process">port</CODE> <EM CLASS="variable">ip_port</EM> <CODE CLASS="Program-Process">allow </CODE><EM CLASS="grammar_literal">{</EM><CODE CLASS="Program-Process"> </CODE><EM CLASS="variable">address_match_list</EM><CODE CLASS="Program-Process"> } </CODE><EM CLASS="grammar_literal">;</EM><EM CLASS="Optional-meta-syntax">
<EM CLASS="Optional-meta-syntax">[ </EM><CODE CLASS="Program-Process">unix</CODE> <EM CLASS="variable">string</EM> <CODE CLASS="Program-Process">permission</CODE> <EM CLASS="variable">number</EM> <CODE CLASS="Program-Process">owner</CODE> <EM CLASS="variable">number</EM> <CODE CLASS="Program-Process">group</CODE> <EM CLASS="variable">number</EM> <EM CLASS="grammar_literal">;</EM><EM CLASS="Optional-meta-syntax">
[ </EM><CODE CLASS="Program-Process">unix</CODE><EM CLASS="Optional-meta-syntax">...</EM><EM CLASS="grammar_literal">;</EM><EM CLASS="Optional-meta-syntax">[..]]]</EM>
statement declares control channels to be used by system administrators to affect the operation of the local nameserver. These control channels are used by the <CODE CLASS="Program-Process">
A UNIX control channel is a "first in first out" (FIFO) named pipe in the file system, and access to it is controlled by normal file system permissions. It is created by <CODE CLASS="Program-Process">
so the number is interpreted as octal. Also note that the user and group ownership specified as owner and group must be given as numbers, not names. It is recommended that the permissions be restricted to administrative personnel only to prevent random users on the system from having the ability to manage the local nameserver.</P>
control channel is a TCP/IP socket accessible to the Internet, created at the specified <CODE CLASS="Program-Process">
used, and this only if you trust all non-privileged users on the local host to manage your nameserver.</P>
statement is not yet implemented in BIND 9. The server always listens for control connections on IP address 127.0.0.1, port 953.</EM>
statement facilitates the administration of configuration files by permitting the reading or writing of some things but not others. For example, the statement could include private keys that are readable only by a nameserver.</P>
<CODE CLASS="Program-Process">key </CODE><EM CLASS="variable">key_id</EM><CODE CLASS="Program-Process"> </CODE><EM CLASS="grammar_literal">{<BR></EM><CODE CLASS="Program-Process">
algorithm </CODE><EM CLASS="variable">string</EM><EM CLASS="grammar_literal">;<BR></EM><CODE CLASS="Program-Process">
statement defines a shared secret key for use with TSIG. See <A HREF="Bv9ARM.4.html#42283" CLASS="XRef">
, also known as the key name, is a domain name uniquely identifying the key. It can be used in a "server" statement to cause requests sent to that server to be signed with this key, or in address match lists to verify that incoming requests have been signed with a key matching this name, algorithm, and secret.</P>
is a string that specifies a security/authentication algorithm. The only algorithm currently supported with TSIG authentication is <KBD CLASS="Literal-user-input">
<EM CLASS="Optional-meta-syntax">[ </EM><CODE CLASS="Program-Process">channel</CODE> <EM CLASS="variable">channel_name</EM> <CODE CLASS="Program-Process">{</CODE>
<EM CLASS="grammar_literal">( </EM><CODE CLASS="Program-Process">file</CODE> <EM CLASS="variable">path name</EM>
<EM CLASS="Optional-meta-syntax">[ </EM><CODE CLASS="Program-Process">versions</CODE> <EM CLASS="grammar_literal">( </EM><EM CLASS="variable">number</EM> <EM CLASS="Optional-meta-syntax">|</EM> <EM CLASS="grammar_literal">unlimited</EM> <EM CLASS="grammar_literal">)</EM> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[ </EM><CODE CLASS="Program-Process">size</CODE> <EM CLASS="variable">size spec</EM><EM CLASS="Optional-meta-syntax"> ]</EM>
<EM CLASS="Optional-meta-syntax">| </EM><CODE CLASS="Program-Process">syslog</CODE> <EM CLASS="grammar_literal">( </EM><EM CLASS="production_target">syslog_facility</EM><EM CLASS="grammar_literal"> </EM>
<EM CLASS="Optional-meta-syntax">|</EM> <EM CLASS="variable">null</EM> <EM CLASS="grammar_literal">);</EM>
<EM CLASS="Optional-meta-syntax">[ </EM><CODE CLASS="Program-Process">severity</CODE> <EM CLASS="grammar_literal">(critical</EM> <EM CLASS="Optional-meta-syntax">| </EM><EM CLASS="grammar_literal">error</EM> <EM CLASS="Optional-meta-syntax">| </EM><EM CLASS="grammar_literal">warning</EM> <EM CLASS="Optional-meta-syntax">|</EM> <EM CLASS="grammar_literal">notice</EM> <EM CLASS="Optional-meta-syntax">|</EM>
<EM CLASS="grammar_literal">info</EM> <EM CLASS="Optional-meta-syntax">|</EM> <EM CLASS="grammar_literal">debug</EM> <EM CLASS="Optional-meta-syntax">[ </EM><EM CLASS="variable">level</EM> <EM CLASS="Optional-meta-syntax">] |</EM> <EM CLASS="grammar_literal">dynamic</EM> <CODE CLASS="Program-Process">;</CODE> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[ </EM><CODE CLASS="Program-Process">print-category</CODE> <EM CLASS="variable">yes or no</EM><EM CLASS="grammar_literal">;</EM><EM CLASS="Optional-meta-syntax"></EM>
<EM CLASS="Optional-meta-syntax">[ </EM><CODE CLASS="Program-Process">print-severity</CODE> <EM CLASS="variable">yes or no</EM><EM CLASS="grammar_literal">;</EM><EM CLASS="Optional-meta-syntax"> ]</EM>
<EM CLASS="Optional-meta-syntax">[ </EM><CODE CLASS="Program-Process">print-time</CODE> <EM CLASS="variable">yes or no</EM><EM CLASS="grammar_literal">;</EM><EM CLASS="Optional-meta-syntax"> ]</EM>
<EM CLASS="Optional-meta-syntax">[ </EM><CODE CLASS="Program-Process">category</CODE> <EM CLASS="variable">category_name</EM> <EM CLASS="grammar_literal">{</EM>
<EM CLASS="variable">channel_name</EM> <CODE CLASS="Program-Process">;</CODE> <EM CLASS="Optional-meta-syntax">[ </EM><EM CLASS="variable">channel_name</EM> <EM CLASS="grammar_literal">;</EM><EM CLASS="Optional-meta-syntax"> ... ]</EM>
<CODE CLASS="Program-Process"> };</CODE> <EM CLASS="Optional-meta-syntax">]</EM> <EM CLASS="Optional-meta-syntax">
statement configures a wide variety of logging options for the nameserver. Its <CODE CLASS="Program-Process">
phrase associates output methods, format options and severity levels with a name that can then be used with the <CODE CLASS="Program-Process">
statement is used to define as many channels and categories as are wanted. If there is no <CODE CLASS="Program-Process">
In BIND 9, the logging configuration is only established when the entire configuration file has been parsed. In BIND 8, it was established as soon as the <CODE CLASS="Program-Process">
statement was parsed. When the server is starting up, all logging messages regarding syntax errors in the configuration file go to the default channels, or to standard error if the "<CODE CLASS="Program-Process">
Every channel definition must include a clause that says whether messages selected for the channel go to a file, to a particular syslog facility, or are discarded. It can optionally also limit the message severity level that will be accepted by the channel (the default is <CODE CLASS="Program-Process">
-generated time stamp, the category name and/or severity level (the default is not to include any).</P>
as the destination option for the channel will cause all messages sent to it to be discarded; in that case, other options for the channel are meaningless.</P>
clause can include limitations both on how large the file is allowed to become, and how many versions of the file will be saved each time the file is opened.</P>
option for files is simply a hard ceiling on log growth. If the file ever exceeds the size, then <CODE CLASS="Program-Process">
will not write anything more to it until the file is reopened; exceeding the size does not automatically trigger a reopen. The default behavior is not to limit the size of the file.</P>
will retain that many backup versions of the file by renaming them when opening. For example, if you choose to keep 3 old versions of the file <EM CLASS="pathname">
. No rolled versions are kept by default; any existing log file is simply appended. The <CODE CLASS="Program-Process">
file "example.log" versions 3 size 20m;
's "priorities," except that they can also be used if you are writing straight to a file rather than using <CODE CLASS="Program-Process">
. Messages which are not at least of the severity level given will not be selected for the channel; messages of higher severity levels will be accepted.</P>
priorities will also determine what eventually passes through. For example, defining a channel facility and severity as <CODE CLASS="Program-Process">
The server can supply extensive debugging information when it is in debugging mode. If the server's global debug level is greater than zero, then debugging mode will be active. The global debug level is set either by starting the <CODE CLASS="Program-Process">
). The global debug level can be set to zero, and debugging mode turned off, by running <CODE CLASS="Program-Process">
. All debugging messages in the server have a debug level, and higher debug levels give more detailed output. Channels that specify a specific debug severity, for example:</P>
will get debugging output of level 3 or less any time the server is in debugging mode, regardless of the global debugging level. Channels with <CODE CLASS="Program-Process">
is requested, then the category of the message will be logged as well. Finally, if <CODE CLASS="Program-Process">
options may be used in any combination, and will always be printed in the following order: time, category, severity. Here is an example where all three <CODE CLASS="Program-Process">
's default logging as follows. How they are used is described in <A HREF="Bv9ARM.6.html#36082" CLASS="XRef">
// of "named.run"
in the server's working directory. For security reasons, when the "<CODE CLASS="Program-Process">
is starting up and still running as root is discarded. If you need to capture this output, you must run the server with the "<CODE CLASS="Program-Process">
Once a channel is defined, it cannot be redefined. Thus you cannot alter the built-in channels directly, but you can modify the default logging by pointing categories at channels you have defined.</P>
There are many categories, so you can send the logs you want to see wherever you want, without seeing logs you don't want. If you don't specify a list of channels for a category, then log messages in that category will be sent to the <CODE CLASS="Program-Process">
category instead. If you don't specify a default category, the following "default default" is used:</P>
<CODE><STRONG>category "default" { "default_syslog"; "default_debug"; };
As an example, let's say you want to log security events to a file, but you also want keep the default logging behavior. You'd specify the following:</P>
To discard all messages in a category, specify the <CODE CLASS="Program-Process">null</CODE> channel:</P>
Following are the available categories and brief descriptions of the types of log information they contain<EM CLASS="EquationVariables">
The default category defines the logging options for those categories where no specific configuration has been defined.</P>
Messages relating to the databases used internally by the name server to store zone and cache data.</P>
DNS resolution, such as the recursive lookups performed on behalf of clients by a caching name server.</P>
[ </EM><KBD CLASS="Literal-user-input">version</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">version_string</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">directory</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">path_name</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">named-xfer</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">path_name</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">tkey-domain</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">domainname</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">tkey-dhkey</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">keyname</EM><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">keyid</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">dump-file</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">path_name</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">memstatistics-file</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">path_name</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">pid-file</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">path_name</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">statistics-file</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">path_name</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">auth-nxdomain</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">yes_or_no</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">deallocate-on-exit</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">yes_or_no</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">dialup</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">yes_or_no</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">fake-iquery</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">yes_or_no</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">fetch-glue</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">yes_or_no</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">has-old-clients</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">yes_or_no</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">host-statistics</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">yes_or_no</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">multiple-cnames</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">yes_or_no</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">notify</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">yes_or_no</EM><EM CLASS="grammar_literal">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">recursion</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">yes_or_no</EM><EM CLASS="grammar_literal">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">rfc2308-type1</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">yes_or_no</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">use-id-pool</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">yes_or_no</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">maintain-ixfr-base</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">yes_or_no</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">forward</KBD><EM CLASS="Optional-meta-syntax"> </EM><KBD CLASS="Literal-user-input">( only </KBD><EM CLASS="Optional-meta-syntax">|</EM><KBD CLASS="Literal-user-input"> first )</KBD><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">forwarders</KBD><EM CLASS="Optional-meta-syntax"> </EM><KBD CLASS="Literal-user-input">{ </EM><EM CLASS="Optional-meta-syntax">[ </EM><EM CLASS="variable">in_addr</EM><EM CLASS="Optional-meta-syntax"> </EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> [ </EM><EM CLASS="variable">in_addr</EM><EM CLASS="Optional-meta-syntax"> </EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ... ] ] </EM><KBD CLASS="Literal-user-input">}; </EM><EM CLASS="Optional-meta-syntax">]
[ </EM><KBD CLASS="Literal-user-input">check-names ( master</KBD><EM CLASS="Optional-meta-syntax"> | </EM><KBD CLASS="Literal-user-input">slave</EM><EM CLASS="Optional-meta-syntax"> | </EM><KBD CLASS="Literal-user-input">response )( warn</EM><EM CLASS="Optional-meta-syntax"> | </EM><KBD CLASS="Literal-user-input">fail</EM><EM CLASS="Optional-meta-syntax"> | </EM><KBD CLASS="Literal-user-input">ignore );</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">allow-query {</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">address_match_list</EM><EM CLASS="Optional-meta-syntax"> </EM><KBD CLASS="Literal-user-input">};</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">allow-transfer</KBD><EM CLASS="EquationVariables"> </EM><KBD CLASS="Literal-user-input">{ </KBD><EM CLASS="variable">address_match_list</EM><KBD CLASS="Literal-user-input"> };</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">allow-recursion {</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">address_match_list</EM><KBD CLASS="Literal-user-input"> };</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">blackhole {</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">address_match_list</EM> <KBD CLASS="Literal-user-input"> };</EM> <EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">listen-on</KBD><EM CLASS="Optional-meta-syntax"> [ </EM><KBD CLASS="Literal-user-input">port</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">ip_port</EM><EM CLASS="Optional-meta-syntax"> ] </EM><KBD CLASS="Literal-user-input">{</EM><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">address_match_list</EM><EM CLASS="Optional-meta-syntax"> </EM><KBD CLASS="Literal-user-input">};</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">query-source</KBD><EM CLASS="Optional-meta-syntax"> [ </EM><KBD CLASS="Literal-user-input">address</KBD><EM CLASS="Optional-meta-syntax"> </EM><KBD CLASS="Literal-user-input">( </EM><EM CLASS="variable">ip_addr</EM><EM CLASS="Optional-meta-syntax"> | </EM><EM CLASS="variable">*</EM><EM CLASS="Optional-meta-syntax"> </EM><KBD CLASS="Literal-user-input">)</EM><EM CLASS="Optional-meta-syntax"> ] [ </EM><KBD CLASS="Literal-user-input">port</EM><EM CLASS="Optional-meta-syntax"> </EM><KBD CLASS="Literal-user-input">(</EM><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">ip_port</EM><EM CLASS="Optional-meta-syntax"> | </EM><EM CLASS="variable">*</EM><EM CLASS="Optional-meta-syntax"> </EM><KBD CLASS="Literal-user-input">)</EM><EM CLASS="Optional-meta-syntax"> ]</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">max-transfer-time-in</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">max-transfer-time-out</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">max-transfer-idle-in</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">max-transfer-idle-out</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">tcp-clients</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">recursive-clients</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">serial-queries</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">transfer-format ( one-answer | many-answers );</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">transfers-in</KBD><EM CLASS="Optional-meta-syntax"> </EM><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">transfers-out </KBD><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">transfers-per-ns </KBD><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">transfer-source </KBD><EM CLASS="variable">ip4_addr</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">transfer-source-v6 </KBD><EM CLASS="variable">ip6_addr</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">also-notify { </KBD><EM CLASS="variable">ip_addr</EM><KBD CLASS="Literal-user-input">; </EM><EM CLASS="Optional-meta-syntax">[ </EM><EM CLASS="variable">ip_addr</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ... ]</EM><KBD CLASS="Literal-user-input"> };</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">max-ixfr-log-size </KBD><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ] [ </EM><KBD CLASS="Literal-user-input">coresize </KBD><EM CLASS="variable">size_spec</EM><KBD CLASS="Literal-user-input"> ;</EM><EM CLASS="Optional-meta-syntax"> ] [ </EM><KBD CLASS="Literal-user-input">datasize </KBD><EM CLASS="variable">size_spec</EM><KBD CLASS="Literal-user-input"> ;</EM><EM CLASS="Optional-meta-syntax"> ] [ </EM><KBD CLASS="Literal-user-input">files </KBD><EM CLASS="variable">size_spec</EM><KBD CLASS="Literal-user-input"> ;</EM><EM CLASS="Optional-meta-syntax"> ] [ </EM><KBD CLASS="Literal-user-input">stacksize </KBD><EM CLASS="variable">size_spec</EM><KBD CLASS="Literal-user-input"> ;</EM><EM CLASS="Optional-meta-syntax"> ] [ </EM><KBD CLASS="Literal-user-input">cleaning-interval </KBD><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">; </EM><EM CLASS="Optional-meta-syntax">] [ </EM><KBD CLASS="Literal-user-input">heartbeat-interval </KBD><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ] [ </EM><KBD CLASS="Literal-user-input">interface-interval </KBD><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ] [ </EM><KBD CLASS="Literal-user-input">statistics-interval </EM><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">topology { </KBD><EM CLASS="variable">address_match_list</EM><KBD CLASS="Literal-user-input"> };</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">sortlist { </KBD><EM CLASS="variable">address_match_list</EM><KBD CLASS="Literal-user-input"> }; </EM><EM CLASS="Optional-meta-syntax">]
[ </EM><KBD CLASS="Literal-user-input">rrset-order { </KBD><EM CLASS="variable">order_spec</EM><KBD CLASS="Literal-user-input"> ; </EM><EM CLASS="Optional-meta-syntax">[ </EM><EM CLASS="variable">order_spec</EM><KBD CLASS="Literal-user-input"> ;</EM><EM CLASS="Optional-meta-syntax"> ... ] ] </EM><KBD CLASS="Literal-user-input">};</EM><EM CLASS="Optional-meta-syntax"> [ </EM><KBD CLASS="Literal-user-input">lame-ttl </EM><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">; </EM><EM CLASS="Optional-meta-syntax">] [ </EM><KBD CLASS="Literal-user-input">max-ncache-ttl </EM><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">; </EM><EM CLASS="Optional-meta-syntax">]
[ </EM><KBD CLASS="Literal-user-input">max-cache-ttl </KBD><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">; </EM><EM CLASS="Optional-meta-syntax">]
[ </EM><KBD CLASS="Literal-user-input">sig-validity-interval </KBD><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input"> ;</EM><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">min-roots </KBD><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">use-ixfr </KBD><EM CLASS="variable">yes_or_no</EM><KBD CLASS="Literal-user-input"> ;</KBD><EM CLASS="Optional-meta-syntax"> ]
[ </EM><KBD CLASS="Literal-user-input">treat-cr-as-space </KBD><EM CLASS="variable">yes_or_no</EM><KBD CLASS="Literal-user-input"> ;</KBD><EM CLASS="Optional-meta-syntax"> ]</EM>
statement sets up global options to be used by BIND. This statement may appear only once in a configuration file. If more than one occurrence is found, the first occurrence determines the actual options used, and a warning will be generated. If there is no <CODE CLASS="Program-Process">
The working directory of the server. Any non-absolute pathnames in the configuration file will be taken as relative to this directory. The default location for most server output files (e.g. <EM CLASS="pathname1">
) is this directory. If a directory is not specified, the working directory defaults to `<EM CLASS="pathname1">
', the directory from which the server was started. The directory specified should be an absolute path.</P>
exchange, it may or may not specify the desired name for the key. If present, the name of the shared key will be "<EM CLASS="variable">
The Diffie-Hellman key used by the server to generate shared keys with clients using the Diffie-Hellman mode of <CODE CLASS="Program-Process">
. The server must be able to load the public and private keys from files in the working directory. In most cases, the keyname should be the server's host name.</P>
The pathname of the file the server dumps the database to when it receives <CODE CLASS="Program-Process">
The pathname of the file the server writes memory usage statistics to on exit. If not specified, the default is <EM CLASS="pathname1">
The pathname of the file the server writes its process ID in. If not specified, the default is operating system dependent, but is usually<BR>
The pathname of the file the server appends statistics to. If not specified, the default is <EM CLASS="pathname1">
bit is always set on NXDOMAIN responses, even if the server is not actually authoritative. The default is <KBD CLASS="Literal-user-input">
; this is a change from BIND 8. If you are using very old DNS software, you may need to set it to <KBD CLASS="Literal-user-input">
This option was used in BIND 8 to enable checking for memory leaks on exit. BIND 9 ignores the option and always performs the checks.</P>
, then the server treats all zones as if they are doing zone transfers across a dial on demand dialup link, which can be brought up by traffic originating from this server. This has different effects according to zone type and concentrates the zone maintenance so that it all happens in a short interval, once every <CODE CLASS="Program-Process">
and hopefully during the one call. It also suppresses some of the normal zone maintenance traffic. The default is <KBD CLASS="Literal-user-input">
If the zone is a master then the server will send out a NOTIFY request to all the slaves. This will trigger the zone serial number check in the slave (providing it supports NOTIFY) allowing the slave to verify the zone while the connection is active.</P>
If the zone is a slave or stub then the server will suppress the regular "zone up to date" queries and only perform them when the<BR>
In BIND 8, this option was used to enable simulating the obsolete DNS query type IQUERY. BIND 9 never does IQUERY simulation.</P>
(the default), the server will fetch glue resource records it doesn't have when constructing the additional data section of a response. <CODE CLASS="Program-Process">
to prevent the server's cache from growing or becoming corrupted (at the cost of requiring more work from the client). <EM CLASS="EquationVariables">
This option was incorrectly implemented in BIND 8, and is ignored by BIND 9. To achieve the intended effect of<BR>
, then statistics are kept for every host that the nameserver interacts with. The default is <KBD CLASS="Literal-user-input">
. It was used in BIND 8 to determine whether a transaction log was kept for Incremental Zone Transfer. BIND 9 maintains a transaction log whenever possible. If you need to disable outgoing incremental zone transfers, use <CODE CLASS="Program-Process">
This option was used in BIND 8 to allow a domain name to allow multiple CNAME records in violation of the DNS standards. BIND 9 currently does not check for multiple CNAMEs in zone data loaded from master files, but such checks may be introduced in a later release. BIND 9 always strictly enforces the CNAME rules in dynamic updates.</P>
(the default), DNS NOTIFY messages are sent when a zone the server is authoritative for changes. See <A HREF="Bv9ARM.3.html#35205" CLASS="XRef">
statement. It would only be necessary to turn off this option if it caused slaves to crash<EM CLASS="EquationVariables">
, and a DNS query requests recursion, then the server will attempt to do all the work required to answer the query. If recursion is not on, the server will return a referral to the client if it doesn't know the answer. The default is <KBD CLASS="Literal-user-input">
will cause the server to send NS records along with the SOA record for negative answers. The default is <KBD CLASS="Literal-user-input">
", to facilitate loading of zone files on a UNIX system that were generated on an NT or DOS machine. In BIND 9, both UNIX "<CODE CLASS="Program-Process">
The forwarding facility can be used to create a large site-wide cache on a few servers, reducing traffic over links to external nameservers. It can also be used to allow queries by servers that do not have direct access to the Internet, but wish to look up exterior names anyway. Forwarding occurs only on those queries for which the server is not authoritative and does not have the answer in its cache.</P>
This option is only meaningful if the forwarders list is not empty. A value of <EM CLASS="variable">
, the default, causes the server to query the forwarders first, and if that doesn't answer the question the server will then look for the answer itself. If <EM CLASS="variable">
Specifies the IP addresses to be used for forwarding. The default is the empty list (no forwarding).</P>
Forwarding can also be configured on a per-domain basis, allowing for the global forwarding options to be overridden in a variety of ways. You can set particular domains to use different forwarders, or have a different <CODE CLASS="Program-Process">
The server can check domain names based upon their expected client contexts. For example, a domain name used as a hostname can be checked for compliance with the RFCs defining valid hostnames.</P>
Names are checked against their expected client contexts. Invalid names are logged, but processing continues normally.</P>
Names are checked against their expected client contexts. Invalid names are logged, and the offending data is rejected.</P>
The server can check names in three areas: master zone files, slave zone files, and in responses to queries the server has initiated. If <CODE CLASS="Program-Process">
has been specified, and answering the client's question would require sending an invalid name to the client, the server will send a REFUSED response code to the client.</P>
Access to the server can be restricted based on the IP address of the requesting system. See <A HREF="Bv9ARM.6.html#28183" CLASS="XRef">
Specifies which hosts are allowed to make recursive queries through this server. If not specified, the default is to allow recursive queries from all hosts. </P>
Specifies which hosts are allowed to receive zone transfers from the server. <CODE CLASS="Program-Process">
Specifies a list of addresses that the server will not accept queries from or use to resolve a query. Queries from these addresses will not be responded to. The default is <KBD CLASS="Literal-user-input">
The interfaces and ports that the server will answer queries from may be specified using the <CODE CLASS="Program-Process">
. The server will listen on all interfaces allowed by the address match list. If a port is not specified, port 53 will be used.</P>
will enable the nameserver on port 53 for the IP address 5.6.7.8, and on port 1234 of an address on the machine in net 1.2 that is not 1.2.3.4.</P>
option is used to specify the ports on which the server will listen for incoming queries sent using IPv6.</P>
The server does not bind a separate socket to each IPv6 interface address as it does for IPv4. Instead, it always listens on the IPv6 wildcard address. Therefore, the only values allowed for the <EM CLASS="EquationVariables">
If the server doesn't know the answer to a question, it will query other nameservers. <CODE CLASS="Program-Process">
specifies the address and port used for such queries. For queries sent over IPv6, there is a separate <CODE CLASS="Program-Process">
currently applies only to UDP queries; TCP queries always use a wildcard IP address and a random unprivileged port.</P>
BIND has mechanisms in place to facilitate zone transfers and set limits on the amount of load that transfers place on the system. The following options apply to zone transfers.</P>
Defines a global list of IP addresses that are also sent NOTIFY messages whenever a fresh copy of the zone is loaded. This helps to ensure that copies of the zones will quickly converge on stealth servers. If an <CODE CLASS="Program-Process">
list will not be sent NOTIFY messages for that zone. The default is the empty list (no global notification list).</P>
Inbound zone transfers running longer than this many minutes will be terminated. The default is 120 minutes (2 hours).</P>
Inbound zone transfers making no progress in this many minutes will be terminated. The default is 60 minutes (1 hour).</P>
Outbound zone transfers running longer than this many minutes will be terminated. The default is 120 minutes (2 hours).</P>
Outbound zone transfers making no progress in this many minutes will be terminated. The default is 60 minutes</P>
Slave servers will periodically query master servers to find out if zone serial numbers have changed. Each such query uses a minute amount of the slave server's network bandwidth, but more importantly each query uses a small amount of memory in the slave server while waiting for the master server to respond. The <CODE CLASS="Program-Process">
option sets the maximum number of concurrent serial-number queries allowed to be outstanding at any given time. The default is 4. Note: If a server loads a large (tens or hundreds of thousands) number of slave zones, then this limit should be raised to the high hundreds or low thousands, otherwise the slave server may never actually become aware of zone changes in the master servers. Beware, though, that setting this limit arbitrarily high can spend a considerable amount of your slave server's network, CPU, and memory resources. As with all tunable limits, this one should be changed gently and monitored for its effects. <EM CLASS="EquationVariables">
is more efficient, but is only known to be understood by BIND 9, BIND 8.x and patched versions of BIND 4.9.5. The default is <CODE CLASS="Program-Process">
The maximum number of inbound zone transfers that can be running concurrently. The default value is <EM CLASS="grammar_literal">
may speed up the convergence of slave zones, but it also may increase the load on the local system.</P>
The maximum number of outbound zone transfers that can be running concurrently. Zone transfer requests in excess of the limit will be refused. The default value is <EM CLASS="grammar_literal">
The maximum number of inbound zone transfers that can be concurrently transferring from a given remote nameserver. The default value is <EM CLASS="grammar_literal">
may speed up the convergence of slave zones, but it also may increase the load on the remote nameserver. <CODE CLASS="Program-Process">
determines which local address will be bound to IPv4 TCP connections used to fetch zones transferred inbound by the server. If not set, it defaults to a system controlled value which will usually be the address of the interface "closest to" the remote end. This address must appear in the remote end's <CODE CLASS="Program-Process">
option for the zone being transferred, if one is specified. This statement sets the <CODE CLASS="Program-Process">
The server's usage of many system resources can be limited. Some operating systems don't support some of the limits. On such systems, a warning will be issued if the unsupported limit is used. Some operating systems don't support limiting resources.</P>
Scaled values are allowed when specifying resource limits. For example, <CODE CLASS="Program-Process">
uses the limit that was in force when the server was started. See the description of <CODE CLASS="Program-Process">
The maximum number of files the server may have open concurrently. The default is <EM CLASS="grammar_literal">
. Note: on some operating systems the server cannot set an unlimited value and cannot determine the maximum number of open files the kernel can support. On such systems, choosing <EM CLASS="grammar_literal">
will be used in a future release of the server to limit the size of the transaction log kept for Incremental Zone Transfer. <EM CLASS="EquationVariables">
The maximum number of simultaneous recursive lookups the server will perform on behalf of clients. The default is <EM CLASS="grammar_literal">
The maximum number of simultaneous client TCP connections that the server will accept. The default is <EM CLASS="grammar_literal">
, interface scanning will only occur when the configuration file is loaded. After the scan, listeners will be started on any new interfaces (provided they are allowed by the <CODE CLASS="Program-Process">
All other things being equal, when the server chooses a nameserver to query from a list of nameservers, it prefers the one that is topologically closest to itself. The <CODE CLASS="Program-Process">
and interprets it in a special way. Each top-level list element is assigned a distance. Non-negated elements get a distance based on their position in the list, where the closer the match is to the start of the list, the shorter the distance is between it and the server. A negated match will be assigned the maximum distance from the server. If there is no match, the address will get a distance which is further than any non-negated list element, and closer than any negated element. For example,</P>
will prefer servers on network 10 the most, followed by hosts on network 1.2.0.0 (netmask 255.255.0.0) and network 3, with the exception of hosts on network 1.2.3 (netmask 255.255.255.0), which is preferred least of all.</P>
Resource Records (RRs) are the data associated with the names in a domain name space. The data is maintained in the form of sets of RRs. The order of RRs in a set is, by default, not significant. Therefore, to control the sorting of records in a set of resource records, or <EM CLASS="EquationVariables">
When returning multiple RRs the nameserver will normally return them in <EM CLASS="EquationVariables">
order, that is, after each request the first RR is put at the end of the list. The client resolver code should rearrange the RRs as appropriate, that is, using any addresses on the local net in preference to other addresses. However, not all resolvers can do this or are correctly configured. When a client is using a local server the sorting can be performed in the server, based on the client's address. This only requires configuring the nameservers, not all the clients.</P>
with one or two elements. The first element (which may be an IP address, an IP prefix, an ACL name or a nested <CODE CLASS="Program-Process">
) of each top level list is checked against the source address of the query until a match is found.</P>
Once the source address of the query has been matched, if the top level statement contains only one element, the actual primitive element that matched the source address is used to select the address in the response to move to the beginning of the response. If the statement is a list of two elements, then the second element is treated the same as the <CODE CLASS="Program-Process">
statement. Each top level element is assigned a distance and the address in the response with the minimum distance is moved to the beginning of the response.</P>
In the following example, any queries received from any of the addresses of the host itself will get responses preferring addresses on any of the locally connected networks. Next most preferred are addresses on the 192.168.1/24 network, and after that either the 192.168.2/24 or<BR>
192.168.3/24 network with no preference shown between these two networks. Queries received from a host on the 192.168.1/24 network will prefer other addresses on that network to the 192.168.2/24 and<BR>
192.168.3/24 networks. Queries received from a host on the 192.168.4/24 or the 192.168.5/24 network will only prefer other addresses on their directly connected networks.</P>
The following example will give reasonable behavior for the local host and hosts on directly connected networks. It is similar to the behavior of the address sort in BIND 8.x. Responses sent to queries from the local host will favor any of the directly connected networks. Responses sent to queries from any other hosts on a directly connected network will prefer addresses on that same network. Responses to other queries will not be sorted.</P>
When multiple records are returned in an answer it may be useful to configure the order of the records placed into the response. For example, the records for a zone might be configured always to be returned in the order they are defined in the zone file. Or perhaps a random shuffle of the records as they are returned is wanted. The <CODE CLASS="Program-Process">
statement permits configuration of the ordering made of the records in a multiple record response. The default, if no ordering is defined, is a cyclic ordering (round robin).</P>
<EM>[ </EM><CODE CLASS="Program-Process">class</CODE> <VAR>class_name</VAR> <EM> ][ </EM><CODE CLASS="Program-Process">type</CODE> <VAR>type_name</VAR> <EM>][</EM> <CODE>name</CODE> <VAR>"domain_name"</VAR><EM>]</EM>
class IN type A name "host.example.com" order random;
" as a suffix, to always be returned in random order. All other records are returned in cyclic order.</P>
Sets the number of seconds to cache a lame server indication. 0 disables caching. (This is NOT recommended.) Default is <EM CLASS="grammar_literal">
To reduce network traffic and increase performance the server stores negative answers. <CODE CLASS="Program-Process">
sets the maximum time for which the server will cache ordinary (positive) answers. The default is one week (7 days).</P>
The minimum number of root servers that is required for a request for the root servers to be accepted. Default is <KBD CLASS="Literal-user-input">
Specifies the number of days into the future when DNSSEC signatures automatically generated as a result of dynamic updates (see <A HREF="Bv9ARM.4.html#39835" CLASS="XRef">
days. The signature inception time is unconditionally set to one hour before the current time to allow for a limited amount of clock skew.</P>
is deprecated in BIND 9. If you need to disable IXFR to a particular server or servers see the information on the <CODE CLASS="Program-Process">
<KBD CLASS="Literal-user-input">server </KBD><EM CLASS="variable">ip_addr</EM><KBD CLASS="Literal-user-input"> {</KBD><BR CLEAR="left">
<EM CLASS="Optional-meta-syntax">[ </EM><KBD CLASS="Literal-user-input">bogus </KBD><EM CLASS="variable">yes_or_no</EM><KBD CLASS="Literal-user-input"> ; </KBD><EM CLASS="Optional-meta-syntax">]</EM><EM CLASS="grammar_literal"></EM>
<EM CLASS="Optional-meta-syntax">[ </EM><KBD CLASS="Literal-user-input">provide-ixfr </KBD><EM CLASS="variable">yes_or_no</EM><KBD CLASS="Literal-user-input"> ; </KBD><EM CLASS="Optional-meta-syntax">]</EM><EM CLASS="grammar_literal"></EM>
<EM CLASS="Optional-meta-syntax">[ </EM><KBD CLASS="Literal-user-input">request-ixfr </KBD><EM CLASS="variable">yes_or_no</EM><KBD CLASS="Literal-user-input"> ; </KBD><EM CLASS="Optional-meta-syntax">]</EM><EM CLASS="grammar_literal"></EM>
<EM CLASS="Optional-meta-syntax">[ </EM><KBD CLASS="Literal-user-input">transfers </KBD><EM CLASS="variable">number</EM><KBD CLASS="Literal-user-input"> ; </KBD><EM CLASS="Optional-meta-syntax">]</EM><EM CLASS="grammar_literal"></EM>
<EM CLASS="Optional-meta-syntax">[ </EM><KBD CLASS="Literal-user-input">transfer-format </KBD><EM CLASS="Optional-meta-syntax">( </EM><EM CLASS="grammar_literal">one-answer </EM><EM CLASS="Optional-meta-syntax">|</EM><EM CLASS="grammar_literal"> many-answers </EM><EM CLASS="Optional-meta-syntax">)</EM><KBD CLASS="Literal-user-input"> ; </KBD><EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="grammar_literal"> </EM><EM CLASS="Optional-meta-syntax">[ </EM><KBD CLASS="Literal-user-input">keys { </KBD><EM CLASS="variable">string</EM><KBD CLASS="Literal-user-input"> ; </KBD><EM CLASS="Optional-meta-syntax">[</EM><EM CLASS="grammar_literal"> </EM><EM CLASS="variable">string</EM><KBD CLASS="Literal-user-input"> ; </KBD><EM CLASS="Optional-meta-syntax">[...]]</EM><KBD CLASS="Literal-user-input"> } ; </KBD><EM CLASS="Optional-meta-syntax">]</EM>
If you discover that a remote server is giving out bad data, marking it as bogus will prevent further queries to it. The default value of <CODE CLASS="Program-Process">
clause determines whether the local server, acting as master, will respond with an incremental zone transfer when the given remote server, a slave, requests it. If set to <CODE CLASS="Program-Process">
, all transfers to the remote server will be nonincremental. If not set, the value of the <CODE CLASS="Program-Process">
clause determines whether the local server, acting as a slave, will request incremental zone transfers from the given remote server, a master. If not set, the value of the <CODE CLASS="Program-Process">
IXFR requests to servers that do not support IXFR will automatically fall back to AXFR. Therefore, there is no need to manually list which servers support IXFR and which ones do not; the global default of <CODE CLASS="Program-Process">
clauses is to make it possible to disable the use of IXFR even when both master and slave claim to support it, for example if one of the servers is buggy and crashes or corrupts data when IXFR is used.</P>
is more efficient, but is only known to be understood by BIND 9, BIND 8.x, and patched versions of BIND 4.9.5. You can specify which method to use for a server with the <CODE CLASS="Program-Process">
is used to limit the number of concurrent inbound zone transfers from the specified server. If no <CODE CLASS="Program-Process">
statement, to be used for transaction security when talking to the remote server. The <CODE CLASS="Program-Process">
statement that references it. When a request is sent to the remote server, a request signature will be generated using the key specified here and appended to the message. A request originating from the remote server is not required to be signed by this key.</P>
</KBD><EM CLASS="Optional-meta-syntax">[ </EM><EM CLASS="variable">string number number number string</EM><EM CLASS="grammar_literal"> ; </EM><EM CLASS="Optional-meta-syntax">[...]]</EM><EM CLASS="grammar_literal">
DNSSEC</A> for a description. A security root is defined when the public key for a non-authoritative zone is known, but cannot be securely obtained through DNS, either because it is the DNS root zone or its parent zone is unsigned. Once a key has been configured as a trusted key, it is treated as if it had been validated and proven secure. The resolver attempts DNSSEC validation on all DNS data in subdomains of a security root.</P>
statement can contain multiple key entries, each consisting of the key's domain name, flags, protocol, algorithm, and the base-64 representation of the key data.</P>
<KBD CLASS="Literal-user-input"> view </KBD><EM CLASS="variable">view name</EM><KBD CLASS="Literal-user-input"> {</KBD>
<KBD CLASS="Literal-user-input">match_clients {</KBD> <EM CLASS="variable">address_match_list</EM><KBD CLASS="Literal-user-input"> } ; </KBD>
<EM CLASS="Optional-meta-syntax">[</EM><CODE CLASS="grammar_literal">view_option</CODE><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ...]</EM><CODE CLASS="grammar_literal">
<EM CLASS="Optional-meta-syntax">[</EM><CODE CLASS="grammar_literal">zone_statement</CODE><KBD CLASS="Literal-user-input">;</KBD><EM CLASS="Optional-meta-syntax"> ...]]</EM>
statement is a powerful new feature of BIND 9 that lets a name server answer a DNS query differently depending on who is asking. It is particularly useful for implementing split DNS setups without having to run multiple servers.</P>
statement defines a view of the DNS namespace that will be seen by those clients whose IP addresses match the <EM CLASS="variable">
statements is significant--a client query will be resolved in the context of the first <CODE CLASS="Program-Process">
. By defining a zone of the same name in multiple views, different zone data can be given to different clients, for example, "internal" and "external" clients in a split DNS setup.</P>
statement, and then apply only when resolving queries with that view. When no a view-specific value is given, the value in the <CODE CLASS="Program-Process">
statement is used as a default. Also, zone options can have default values specified in the <CODE CLASS="Program-Process">
statement; these view-specific defaults take precedence over those in the <CODE CLASS="Program-Process">
statements in the config file, a default view that matches any client is automatically created in class IN, and any <CODE CLASS="Program-Process">
statements specified on the top level of the configuration file are considered to be part of this default view. If any explicit <CODE CLASS="Program-Process">
') does not strictly define a zone. Therefore, it should not be included in a <CODE CLASS="Program-Process">
// Provide a complete view of the example.com zone
zone "example.com" {
file "example-internal.db";
// Provide a restricted view of the example.com zone
zone "example.com" {
file "example-external.db";
<KBD CLASS="literal-user-input">zone</KBD> <EM CLASS="variable">zone name</EM> <EM CLASS="Optional-meta-syntax">[</EM><EM CLASS="variable">class</EM><EM CLASS="Optional-meta-syntax">] [</EM><KBD CLASS="literal-user-input">{</KBD>
<KBD CLASS="Literal-user-input">type</KBD> <EM CLASS="Optional-meta-syntax">( </EM><KBD CLASS="literal-user-input">master</KBD><EM CLASS="Optional-meta-syntax">|</EM><KBD CLASS="literal-user-input">slave</KBD><EM CLASS="Optional-meta-syntax">|</EM><KBD CLASS="literal-user-input">hint</KBD><EM CLASS="Optional-meta-syntax">|</EM><KBD CLASS="literal-user-input">stub</KBD><EM CLASS="Optional-meta-syntax">|</EM><KBD CLASS="literal-user-input">forward </KBD><EM CLASS="Optional-meta-syntax">)</EM><KBD CLASS="literal-user-input"> ;</KBD>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">allow-query</KBD> <KBD CLASS="literal-user-input">{</KBD> <EM CLASS="variable">address_match_list</EM> } <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">allow-transfer</KBD> <KBD CLASS="literal-user-input">{</KBD> <EM CLASS="variable">address_match_list</EM> } <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">allow-update</KBD> <KBD CLASS="literal-user-input">{</KBD> <EM CLASS="variable">address_match_list</EM> } <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">update-policy</KBD> <KBD CLASS="literal-user-input">{</KBD> <EM CLASS="variable">update_policy_rule</EM><EM CLASS="Optional-meta-syntax">[...]</EM> <EMCLASS="grammar_literal">} ;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">allow-update-forwarding</KBD> <KBD CLASS="literal-user-input">{</KBD> <EM CLASS="variable">address_match_list</EM> <KBD CLASS="literal-user-input">} ;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">also-notify</KBD> <KBD CLASS="literal-user-input">{</KBD> <EM CLASS="Optional-meta-syntax">[</EM> <EM CLASS="variable">ip_addr</EM> <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">[</EM><EM CLASS="variable">ip_addr</EM> <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">[...]]]</EM> <KBD CLASS="literal-user-input">} ;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">check-names</KBD> <KBD CLASS="literal-user-input">(warn</KBD><EM CLASS="Optional-meta-syntax">|</EM><KBD CLASS="literal-user-input">fail</KBD><EM CLASS="Optional-meta-syntax">|</EM><KBD CLASS="literal-user-input">ignore)</KBD> <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">dialup</KBD> <EM CLASS="variable">true_or_false</EM> <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">file</KBD> <EM CLASS="variable">string</EM> <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">forward</KBD> <KBD CLASS="literal-user-input">(only</KBD><EM CLASS="Optional-meta-syntax">|</EM><KBD CLASS="literal-user-input">first)</KBD> <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">forwarders</KBD> <KBD CLASS="literal-user-input">{</KBD> <EM CLASS="Optional-meta-syntax">[</EM> <EM CLASS="variable">ip_addr</EM> <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">[</EM> <EM CLASS="variable">ip_addr</EM> <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">[...]]]</EM> <KBD CLASS="literal-user-input">} ;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">ixfr-base</KBD> <EM CLASS="variable">string</EM> <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">ixfr-tmp-file</KBD> <EM CLASS="variable">string</EM> <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">maintain-ixfr-base</KBD> <EM CLASS="variable">true_or_false</EM> <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">masters</KBD> <EM CLASS="Optional-meta-syntax">[</EM>port <EM CLASS="variable">number</EM><EM CLASS="Optional-meta-syntax">]</EM> <KBD CLASS="literal-user-input">{</KBD> <EM CLASS="variable">ip_addr</EM> ; <EM CLASS="Optional-meta-syntax">[</EM><EM CLASS="variable">ip_addr</EM> ; <EM CLASS="Optional-meta-syntax">[...]]</EM> <KBD CLASS="literal-user-input">}</KBD> <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">max-ixfr-log-size</KBD> <EM CLASS="variable">number</EM> ; <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">max-transfer-idle-in</KBD> <EM CLASS="variable">number </EM><KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">max-transfer-idle-out</KBD> <EM CLASS="variable">number </EM><KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">max-transfer-time-in</KBD> <EM CLASS="variable">number </EM><KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">max-transfer-time-out</KBD> <EM CLASS="variable">number </EM><KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">notify</KBD> <EM CLASS="variable">true_or_false</EM> <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">pubkey</KBD> <EM CLASS="variable">number number number</EM> <EM CLASS="variable">string</EM> ; <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">transfer-source</KBD> <KBD CLASS="literal-user-input">(</KBD><EM CLASS="variable">ip4_addr</EM> <EM CLASS="Optional-meta-syntax">|</EM> <EM CLASS="variable">*</EM><KBD CLASS="literal-user-input">)</KBD> <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[</EM> <KBD CLASS="literal-user-input">transfer-source-v6</KBD> <KBD CLASS="literal-user-input">(</KBD><EM CLASS="variable">ip6_addr</EM> <EM CLASS="Optional-meta-syntax">|</EM> <EM CLASS="variable">*</EM><KBD CLASS="literal-user-input">)</KBD> <KBD CLASS="literal-user-input">;</KBD> <EM CLASS="Optional-meta-syntax">]</EM>
<EM CLASS="Optional-meta-syntax">[ </EM><KBD CLASS="literal-user-input">sig-validity-interval </KBD><EM CLASS="variable">number</EM><KBD CLASS="literal-user-input"> ;</KBD><EM CLASS="Optional-meta-syntax"> ]</EM><KBD CLASS="literal-user-input">}</KBD><EM CLASS="Optional-meta-syntax">]</EM>
The server has a master copy of the data for the zone and will be able to provide authoritative answers for it.</P>
A slave zone is a replica of a master zone. The masters list specifies one or more IP addresses that the slave contacts to update its copy of the zone. If a port is specified, the slave then checks to see if the zone is current and zone transfers will be done to the port given. If a file is specified, then the replica will be written to this file whenever the zone is changed, and reloaded from this file on a server restart. Use of a file is recommended, since it often speeds server start-up and eliminates a needless waste of bandwidth. Note that for large numbers (in the tens or hundreds of thousands) of zones per server, it is best to use a two level naming scheme for zone file names. For example, a slave server for the zone <EM CLASS="URL">
is just the first two letters of the zone name. (Most operating systems behave very slowly if you put 100K files into a single directory.)</P>
A stub zone is similar to a slave zone, except that it replicates only the NS records of a master zone instead of the entire zone. Stub zones are not a standard part of the DNS; they are a peculiarity of BIND 4 and BIND 8 that relies heavily on the particular way the zone data is structured in those servers. BIND 9 attempts to emulate the BIND 4/8 stub zone feature for backwards compatibility, but we do not recommend its use in new configurations.</P>
In BIND 4/8, zone transfers of a parent zone included the NS records from stub children of that zone. This meant that, in some cases, users could get away with configuring child stubs only in the master server for the parent zone. BIND 9 never mixes together zone data from different zones in this way. Therefore, if a BIND 9 master serving a parent zone has child stub zones configured, all the slave servers for the parent zone also need to have the same child stub zones configured..</P>
A "forward zone" is a way to configure forwarding on a per-domain basis. A <CODE CLASS="Program-Process">
statement, which will apply to queries within the domain given by the zone name. If no <CODE CLASS="Program-Process">
is given, then no forwarding will be done for the domain, cancelling the effects of any forwarders in the <CODE CLASS="Program-Process">
statement. Thus if you want to use this type of zone to change the behavior of the global <CODE CLASS="Program-Process">
option (that is, "forward first to", then "forward only", or vice versa, but want to use the same servers as set globally) you need to respecify the global forwarders. <EM CLASS="EquationVariables">
The initial set of root nameservers is specified using a "hint zone". When the server starts up, it uses the root hints to find a root nameserver and get the most recent list of root nameservers. If no hint zone is specified for class IN, the server users a compiled-in default set of root servers hints. Classes other than IN have no built-in defaults hints.</P>
The zone's name may optionally be followed by a class. If a class is not specified, class <EM CLASS="grammar_literal">
class is named for an information service from MIT's Project Athena. It is used to share information about various systems databases, such as users, groups, printers and so on. The keyword <EM CLASS="grammar_literal">
Another MIT development is CHAOSnet, a LAN protocol created in the mid-1970s. Zone data for it can be specified with the <EM CLASS="grammar_literal">
Specifies which hosts are allowed to submit Dynamic DNS updates for master zones. The default is to deny updates from all hosts.</P>
Specifies a "Simple Secure Update" policy. See description in <A HREF="Bv9ARM.6.html#13905" CLASS="XRef">
Specifies which hosts are allowed to submit Dynamic DNS updates to slave zones to be forwarded to the master. The default is to deny update forwarding from all hosts. <EM CLASS="EquationVariables">
message for this zone is made up of all the listed nameservers (other than the primary master) for the zone plus any IP addresses specified with <CODE CLASS="Program-Process">
value causes the lookup to fail after trying the forwarders and getting no answer, while <CODE CLASS="Program-Process">
Used to override the list of global forwarders. If it is not specified in a zone of type <CODE CLASS="Program-Process">
Was used in BIND 8 to specify the name of the transaction log (journal) file for dynamic update and IXFR. BIND 9 ignores the option and constructs the name of the journal file by appending ".<EM CLASS="pathname1">
In BIND 8, this option was intended for specifying a public zone key for verification of signatures in DNSSEC signed zones when they are loaded from disk. BIND 9 does not verify signatures on loading and ignores the option.</P>
Determines which local address will be bound to the IPv4 TCP connection used to fetch this zone. If not set, it defaults to a system controlled value which will usually be the address of the interface "closest to" the remote end. This address must appear in the remote end's <CODE CLASS="Program-Process">
BIND 9 supports two alternative methods of granting clients the right to perform dynamic updates to a zone, configured by the <CODE CLASS="Program-Process">
clause works the same way as in previous versions of BIND. It grants given clients the permission to update any record of any name in the zone.</P>
clause is new in BIND 9 and allows more fine-grained control over what updates are allowed. A set of rules is specified, where each rule either grants or denies permissions for one or more names to be updated by one or more identities. If the dynamic update request message is signed (that is, it includes either a TSIG or SIG(0) record), the identity of the signer can be determined.</P>
<EM>(</EM> <CODE><STRONG>grant</STRONG></CODE> <EM>|</EM> <CODE><STRONG>deny</STRONG></CODE> <EM>)</EM> <EM>identity nametype name [ <CODE>types</CODE> ]</EM>
Each rule grants or denies privileges. Once a messages has successfully matched a rule, the operation is immediately granted or denied and no further rules are examined. A rule is matched when the signer matches the identity field, the name matches the name field, and the type is specified in the type field.</P>
The identity field specifies a name or a wildcard name. The nametype field has 4 values: <EM CLASS="variable">
If no types are specified, the rule matches all types except SIG, NS, SOA, and NXT. Types may be specified by name, including "ANY" (ANY matches all types except NXT, which can never be updated).</P>
This section, largely borrowed from RFC 1034, describes the concept of a Resource Record (RR) and explains when each is used. Since the publication of RFC 1034, several new RRs have been identified and implemented in the DNS. These are also included.</P>
A domain name identifies a node. Each node has a set of resource information, which may be empty. The set of resource information associated with a particular name is composed of separate RRs. The order of RRs in a set is not significant and need not be preserved by nameservers, resolvers, or other parts of the DNS. However, sorting of multiple RRs is permitted for optimization purposes, for example, to specify that a particular nearby server be tried first. See <A HREF="Bv9ARM.6.html#39491" CLASS="XRef">
an encoded 16 bit value that specifies the type of the resource in this resource record. Types refer to abstract resources.</P>
the time to live of the RR. This field is a 32 bit integer in units of seconds, and is primarily used by resolvers when they cache RRs. The TTL describes how long a RR can be cached before it should be discarded.</P>
of valid RRs (some of these listed, although not obsolete, are experimental (x) or historical (h) and no longer in general use):</P>
for delegation of reverse addresses. Replaces the domain name specified with another name to be looked up. Described in RFC 2672.</P>
used in DNSSEC to securely indicate that RRs with an owner name in a certain name interval do not exist in a zone and indicate what RR types are present for an existing name. See RFC 2535 for details.</P>
(x) route-through binding for hosts that do not have their own direct wide area network addresses. Experimental.</P>
("signature") contains data authenticated in the secure DNS. See RFC 2535 for details.</P>
(h) information about which well known network services, such as SMTP, that a domain supports. Historical, replaced by newer RR SRV.</P>
maps a domain name to an IPv6 address, with a provision for indirection for leading "prefix" bits.</P>
provides alternate naming to an entire subtree of the domain name space, rather than to a single node. It causes some suffix of a queried name to be substituted with a name from the DNAME record's RDATA.</P>
a 16 bit preference value (lower is better) followed by a host name willing to act as a mail exchange for the owner domain.</P>
The owner name is often implicit, rather than forming an integral part of the RR. For example, many nameservers internally form tree or hash structures for the name space, and chain RRs off nodes. The remaining RR parts are the fixed header (type, class, TTL) which is consistent for all RRs, and a variable part (RDATA) that fits the needs of the resource being described.</P>
The meaning of the TTL field is a time limit on how long an RR can be kept in a cache. This limit does not apply to authoritative data in zones; it is also timed out, but by the refreshing policies for the zone. The TTL is assigned by the administrator for the zone where the data originates. While short TTLs can be used to minimize caching, and a zero TTL prohibits caching, the realities of Internet performance suggest that these times should be on the order of days for the typical host. If a change can be anticipated, the TTL can be reduced prior to the change to minimize inconsistency during the change, and then increased back to its former value following the change.</P>
The data in the RDATA section of RRs is carried as a combination of binary strings and domain names. The domain names are frequently used as "pointers" to other data in the DNS.</P>
RRs are represented in binary form in the packets of the DNS protocol, and are usually represented in highly encoded form when stored in a nameserver or resolver. In the examples provided in RFC 1034, a style similar to that used in master files was employed in order to show the contents of RRs. In this format, most RRs are shown on a single line, although continuation lines are possible using parentheses.</P>
The start of the line gives the owner of the RR. If a line begins with a blank, then the owner is assumed to be the same as that of the previous RR. Blank lines are often included for readability.</P>
Following the owner, we list the TTL, type, and class of the RR. Class and type use the mnemonics defined above, and TTL is an integer before the type field. In order to avoid ambiguity in parsing, type and class mnemonics are disjoint, TTLs are integers, and the type mnemonic is always last. The IN class and TTL values are often omitted from examples in the interests of clarity.</P>
The resource data or RDATA section of the RR are given using knowledge of the typical representation for the data.</P>
The MX RRs have an RDATA section which consists of a 16 bit number followed by a domain name. The address RRs use a standard IP address format to contain a 32 bit internet address.</P>
As described above, domain servers store information as a series of resource records, each of which contains a particular piece of information about a given domain name (which is usually, but not always, a host). The simplest way to think of a RR is as a typed pair of datum, a domain name matched with relevant data, and stored with some additional type information to help systems determine when the RR is relevant.</P>
MX records are used to control delivery of email. The data specified in the record is a priority and a domain name. The priority controls the order in which email delivery is attempted, with the lowest number first. If two priorities are the same, a server is chosen randomly. If no servers at a given priority are responding, the mail transport agent will fall back to the next largest priority. Priority numbers do not have any absolute meaning - they are relevant only respective to other MX records for that domain name. The domain name given is the machine to which the mail will be delivered. It <EM CLASS="Emphasis">
For a given domain, if there is both a CNAME record and an MX record, the MX record is in error, and will be ignored. Instead, the mail will be delivered to the server specified in the MX record pointed to by the CNAME.</P>
The time to live of the RR field is a 32 bit integer represented in units of seconds, and is primarily used by resolvers when they cache RRs. The TTL describes how long a RR can be cached before it should be discarded. The following three types of TTL are currently used in a zone file.</P>
The last field in the SOA is the negative caching TTL. This controls how long other servers will cache no-such-domain (NXDOMAIN) responses from you.</P>
The $TTL directive at the top of the zone file (before the SOA) gives a default TTL for every RR without a specific TTL set.</P>
Each RR can have a TTL as the second field in the RR, which will control how long other servers can cache the it.</P>
All of these TTLs default to units of seconds, though units can be explicitly specified, for example, <EM CLASS="grammar_literal">
Reverse name resolution (that is, translation from IP address to name) is achieved by means of the <EM CLASS="URL">
domain and PTR records. Entries in the in-addr.arpa domain are made in least-to-most significant order, read left to right. This is the opposite order to the way IP addresses are usually written. Thus, a machine with an IP address of 10.1.2.3 would have a corresponding in-addr.arpa name of<BR>
3.2.1.10.in-addr.arpa. This name should have a PTR resource record whose data field is the name of the machine or, optionally, multiple PTR records if the machine has more than one name. For example, in the <EM CLASS="Optional-meta-syntax">
3 IN PTR foo.example.com.
lines in the examples are for providing context to the examples only--they do not necessarily appear in the actual usage. They are only used here to indicate that the example is relative to the listed origin.)</P>
The Master File Format was initially defined in RFC 1035 and has subsequently been extended. While the Master File Format itself is class independent all records in a Master File must be of the same class.</P>
sets the domain name that will be appended to any unqualified records. When a zone is first read in there is an implicit <CODE CLASS="Program-Process">
is specified differs from that described in RFC 1035. The origin and current domain revert to the values they were prior to the <CODE CLASS="Program-Process">
Set the default Time To Live (TTL) for subsequent records with undefined TTLs. Valid TTLs are of the range 0-2147483647 seconds.</P>
is used to create a series of resource records that only differ from each other by an iterator. <CODE CLASS="Program-Process">
can be used to easily generate the sets of records required to support sub /24 reverse delegations described in RFC 2317: Classless IN-ADDR.ARPA delegation.</P>
$ORIGIN 0.0.192.IN-ADDR.ARPA.
This can be one of two forms: start-stop or start-stop/step. If the first form is used then step is set to 1. All of start, stop and step must be positive.</P>
describes the owner name of the resource records to be created. Any single <CODE CLASS="Program-Process">
side are replaced by the iterator value. To get a $ in the output use a double <CODE CLASS="Program-Process">
directive is a BIND extension and not part of the standard zone file format. <EM CLASS="EquationVariables">