<
p><
span><
strong class="command">none</
strong></
span></
p>
<
p><
span><
strong class="command">localhost</
strong></
span></
p>
Matches the IPv4 and IPv6 addresses of all network
interfaces on the system.
<
p><
span><
strong class="command">localnets</
strong></
span></
p>
Matches any host on an IPv4 or IPv6 network
for which the system has an interface.
Some systems do not provide a way to determine the prefix
In such a case, <
span><
strong class="command">localnets</
strong></
span>
IPv6 addresses, just like <
span><
strong class="command">localhost</
strong></
span>.
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2544381"></
a><
span><
strong class="command">controls</
strong></
span> Statement Grammar</
h3></
div></
div></
div>
<
pre class="programlisting"><
span><
strong class="command">controls</
strong></
span> {
[ inet ( ip_addr | * ) [ port ip_port ] allow { <
em class="replaceable"><
code> address_match_list </
code></
em> }
keys { <
em class="replaceable"><
code>key_list</
code></
em> }; ]
[ 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> }; ]
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="controls_statement_definition_and_usage"></
a><
span><
strong class="command">controls</
strong></
span> Statement Definition and
Usage</
h3></
div></
div></
div>
The <
span><
strong class="command">controls</
strong></
span> statement declares control
channels to be used by system administrators to control the
operation of the name server. These control channels are
used by the <
span><
strong class="command">rndc</
strong></
span> utility to send
commands to and retrieve non-DNS results from a name server.
An <
span><
strong class="command">inet</
strong></
span> control channel is a TCP socket
listening at the specified <
span><
strong class="command">ip_port</
strong></
span> on the
specified <
span><
strong class="command">ip_addr</
strong></
span>, which can be an IPv4 or IPv6
address. An <
span><
strong class="command">ip_addr</
strong></
span> of <
code class="literal">*</
code> is
interpreted as the IPv4 wildcard address; connections will be
accepted on any of the system's IPv4 addresses.
To listen on the IPv6 wildcard address,
use an <
span><
strong class="command">ip_addr</
strong></
span> of <
code class="literal">::</
code>.
If you will only use <
span><
strong class="command">rndc</
strong></
span> on the local host,
using the loopback address (<
code class="literal">127.0.0.1</
code>
or <
code class="literal">::1</
code>) is recommended for maximum security.
If no port is specified, port 953 is used.
"<
code class="literal">*</
code>" cannot be used for <
span><
strong class="command">ip_port</
strong></
span>.
The ability to issue commands over the control channel is
restricted by the <
span><
strong class="command">allow</
strong></
span> and
<
span><
strong class="command">keys</
strong></
span> clauses.
Connections to the control channel are permitted based on the
<
span><
strong class="command">address_match_list</
strong></
span>. This is for simple
IP address based filtering only; any <
span><
strong class="command">key_id</
strong></
span>
elements of the <
span><
strong class="command">address_match_list</
strong></
span>
An <
span><
strong class="command">unix</
strong></
span> control channel is a UNIX domain
socket listening at the specified path in the file system.
Access to the socket is specified by the <
span><
strong class="command">perm</
strong></
span>,
<
span><
strong class="command">owner</
strong></
span> and <
span><
strong class="command">group</
strong></
span> clauses.
Note on some platforms (SunOS and Solaris) the permissions
(<
span><
strong class="command">perm</
strong></
span>) are applied to the parent directory
as the permissions on the socket itself are ignored.
The primary authorization mechanism of the command
channel is the <
span><
strong class="command">key_list</
strong></
span>, which
contains a list of <
span><
strong class="command">key_id</
strong></
span>s.
Each <
span><
strong class="command">key_id</
strong></
span> in the <
span><
strong class="command">key_list</
strong></
span>
is authorized to execute commands over the control channel.
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 “Administrative Tools”</
a>)
for information about configuring keys in <
span><
strong class="command">rndc</
strong></
span>.
If no <
span><
strong class="command">controls</
strong></
span> statement is present,
<
span><
strong class="command">named</
strong></
span> will set up a default
control channel listening on the loopback address 127.0.0.1
and its IPv6 counterpart ::1.
In this case, and also when the <
span><
strong class="command">controls</
strong></
span> statement
is present but does not have a <
span><
strong class="command">keys</
strong></
span> clause,
<
span><
strong class="command">named</
strong></
span> will attempt to load the command channel key
from the file <
code class="filename">
rndc.key</
code> in
<
code class="filename">/etc</
code> (or whatever <
code class="varname">sysconfdir</
code>
was specified as when <
span class="acronym">BIND</
span> was built).
To create a <
code class="filename">
rndc.key</
code> file, run
<
strong class="userinput"><
code>rndc-confgen -a</
code></
strong>.
The <
code class="filename">
rndc.key</
code> feature was created to
ease the transition of systems from <
span class="acronym">BIND</
span> 8,
which did not have digital signatures on its command channel
messages and thus did not have a <
span><
strong class="command">keys</
strong></
span> clause.
It makes it possible to use an existing <
span class="acronym">BIND</
span> 8
configuration file in <
span class="acronym">BIND</
span> 9 unchanged,
and still have <
span><
strong class="command">rndc</
strong></
span> work the same way
<
span><
strong class="command">ndc</
strong></
span> worked in BIND 8, simply by executing the
command <
strong class="userinput"><
code>rndc-confgen -a</
code></
strong> after BIND 9 is
Since the <
code class="filename">
rndc.key</
code> feature
is only intended to allow the backward-compatible usage of
<
span class="acronym">BIND</
span> 8 configuration files, this
have a high degree of configurability. You cannot easily change
the key name or the size of the secret, so you should make a
<
code class="filename">
rndc.conf</
code> with your own key if you
those things. The <
code class="filename">
rndc.key</
code> file
permissions set such that only the owner of the file (the user that
<
span><
strong class="command">named</
strong></
span> is running as) can access it.
desire greater flexibility in allowing other users to access
<
span><
strong class="command">rndc</
strong></
span> commands then you need to create
<
code class="filename">
rndc.conf</
code> and make it group
that contains the users who should have access.
To disable the command channel, use an empty
<
span><
strong class="command">controls</
strong></
span> statement:
<
span><
strong class="command">controls { };</
strong></
span>.
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2544674"></
a><
span><
strong class="command">include</
strong></
span> Statement Grammar</
h3></
div></
div></
div>
<
pre class="programlisting">include <
em class="replaceable"><
code>filename</
code></
em>;</
pre>
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2544689"></
a><
span><
strong class="command">include</
strong></
span> Statement Definition and
Usage</
h3></
div></
div></
div>
The <
span><
strong class="command">include</
strong></
span> statement inserts the
specified file at the point where the <
span><
strong class="command">include</
strong></
span>
statement is encountered. The <
span><
strong class="command">include</
strong></
span>
statement facilitates the administration of configuration
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 the name server.
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2544712"></
a><
span><
strong class="command">key</
strong></
span> Statement Grammar</
h3></
div></
div></
div>
<
pre class="programlisting">key <
em class="replaceable"><
code>key_id</
code></
em> {
algorithm <
em class="replaceable"><
code>string</
code></
em>;
secret <
em class="replaceable"><
code>string</
code></
em>;
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2544733"></
a><
span><
strong class="command">key</
strong></
span> Statement Definition and Usage</
h3></
div></
div></
div>
The <
span><
strong class="command">key</
strong></
span> statement defines a shared
secret key for use with TSIG (see <
a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called “TSIG”</
a>)
(see <
a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and Usage">the section called “<
span><
strong class="command">controls</
strong></
span> Statement Definition and
The <
span><
strong class="command">key</
strong></
span> statement can occur at the
of the configuration file or inside a <
span><
strong class="command">view</
strong></
span>
statement. Keys defined in top-level <
span><
strong class="command">key</
strong></
span>
statements can be used in all views. Keys intended for use in
a <
span><
strong class="command">controls</
strong></
span> statement
(see <
a href="Bv9ARM.ch06.html#controls_statement_definition_and_usage" title="controls Statement Definition and Usage">the section called “<
span><
strong class="command">controls</
strong></
span> Statement Definition and
must be defined at the top level.
The <
em class="replaceable"><
code>key_id</
code></
em>, also known as the
key name, is a domain name uniquely identifying the key. It can
be used in a <
span><
strong class="command">server</
strong></
span>
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.
The <
em class="replaceable"><
code>algorithm_id</
code></
em> is a string
algorithm currently supported with TSIG authentication is
<
code class="literal">hmac-md5</
code>. The
<
em class="replaceable"><
code>secret_string</
code></
em> is the secret
used by the algorithm, and is treated as a base-64 encoded
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2544805"></
a><
span><
strong class="command">logging</
strong></
span> Statement Grammar</
h3></
div></
div></
div>
<
pre class="programlisting"><
span><
strong class="command">logging</
strong></
span> {
[ <
span><
strong class="command">channel</
strong></
span> <
em class="replaceable"><
code>channel_name</
code></
em> {
( <
span><
strong class="command">file</
strong></
span> <
em class="replaceable"><
code>path name</
code></
em>
[ <
span><
strong class="command">versions</
strong></
span> ( <
em class="replaceable"><
code>number</
code></
em> | <
span><
strong class="command">unlimited</
strong></
span> ) ]
[ <
span><
strong class="command">size</
strong></
span> <
em class="replaceable"><
code>size spec</
code></
em> ]
| <
span><
strong class="command">syslog</
strong></
span> <
em class="replaceable"><
code>syslog_facility</
code></
em>
| <
span><
strong class="command">stderr</
strong></
span>
| <
span><
strong class="command">null</
strong></
span> );
[ <
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> |
<
code class="option">info</
code> | <
code class="option">debug</
code> [ <
em class="replaceable"><
code>level</
code></
em> ] | <
code class="option">dynamic</
code> ); ]
[ <
span><
strong class="command">print-category</
strong></
span> <
code class="option">yes</
code> or <
code class="option">no</
code>; ]
[ <
span><
strong class="command">print-severity</
strong></
span> <
code class="option">yes</
code> or <
code class="option">no</
code>; ]
[ <
span><
strong class="command">print-time</
strong></
span> <
code class="option">yes</
code> or <
code class="option">no</
code>; ]
[ <
span><
strong class="command">category</
strong></
span> <
em class="replaceable"><
code>category_name</
code></
em> {
<
em class="replaceable"><
code>channel_name</
code></
em> ; [ <
em class="replaceable"><
code>channel_name</
code></
em> ; ... ]
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2544931"></
a><
span><
strong class="command">logging</
strong></
span> Statement Definition and
Usage</
h3></
div></
div></
div>
The <
span><
strong class="command">logging</
strong></
span> statement configures a
variety of logging options for the name server. Its <
span><
strong class="command">channel</
strong></
span> phrase
associates output methods, format options and severity levels with
a name that can then be used with the <
span><
strong class="command">category</
strong></
span> phrase
to select how various classes of messages are logged.
Only one <
span><
strong class="command">logging</
strong></
span> statement is used to
as many channels and categories as are wanted. If there is no <
span><
strong class="command">logging</
strong></
span> statement,
the logging configuration will be:
<
pre class="programlisting">logging {
category default { default_syslog; default_debug; };
category unmatched { null; };
In <
span class="acronym">BIND</
span> 9, the logging configuration
the entire configuration file has been parsed. In <
span class="acronym">BIND</
span> 8, it was
established as soon as the <
span><
strong class="command">logging</
strong></
span>
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="option">-g</
code>" option
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2545051"></
a>The <
span><
strong class="command">channel</
strong></
span> Phrase</
h4></
div></
div></
div>
All log output goes to one or more <
span class="emphasis"><
em>channels</
em></
span>;
you can make as many of them as you want.
Every channel definition must include a destination clause that
says whether messages selected for the channel go to a file, to a
particular syslog facility, to the standard error stream, or are
discarded. It can optionally also limit the message severity level
that will be accepted by the channel (the default is
<
span><
strong class="command">info</
strong></
span>), and whether to include a
<
span><
strong class="command">named</
strong></
span>-generated time stamp, the
and/
or severity level (the default is not to include any).
The <
span><
strong class="command">null</
strong></
span> destination clause
causes all messages sent to the channel to be discarded;
in that case, other options for the channel are meaningless.
The <
span><
strong class="command">file</
strong></
span> destination clause directs
to a disk file. It can include limitations
both on how large the file is allowed to become, and how many
of the file will be saved each time the file is opened.
If you use the <
span><
strong class="command">versions</
strong></
span> log file
<
span><
strong class="command">named</
strong></
span> will retain that many backup
renaming them when opening. For example, if you choose to keep 3
of the file <
code class="filename">
lamers.log</
code> then just
You can say <
span><
strong class="command">versions unlimited</
strong></
span> to
If a <
span><
strong class="command">size</
strong></
span> option is associated with
then renaming is only done when the file being opened exceeds the
indicated size. No backup versions are kept by default; any
log file is simply appended.
The <
span><
strong class="command">size</
strong></
span> option for files is used
growth. If the file ever exceeds the size, then <
span><
strong class="command">named</
strong></
span> will
stop writing to the file unless it has a <
span><
strong class="command">versions</
strong></
span> option
associated with it. If backup versions are kept, the files are
described above and a new one begun. If there is no
<
span><
strong class="command">versions</
strong></
span> option, no more data will
until some out-of-band mechanism removes or truncates the log to
maximum size. The default behavior is not to limit the size of
Example usage of the <
span><
strong class="command">size</
strong></
span> and
<
span><
strong class="command">versions</
strong></
span> options:
<
pre class="programlisting">channel an_example_channel {
The <
span><
strong class="command">syslog</
strong></
span> destination clause
channel to the system log. Its argument is a
syslog facility as described in the <
span><
strong class="command">syslog</
strong></
span> man
page. Known facilities are <
span><
strong class="command">kern</
strong></
span>, <
span><
strong class="command">user</
strong></
span>,
<
span><
strong class="command">mail</
strong></
span>, <
span><
strong class="command">daemon</
strong></
span>, <
span><
strong class="command">auth</
strong></
span>,
<
span><
strong class="command">syslog</
strong></
span>, <
span><
strong class="command">lpr</
strong></
span>, <
span><
strong class="command">news</
strong></
span>,
<
span><
strong class="command">uucp</
strong></
span>, <
span><
strong class="command">cron</
strong></
span>, <
span><
strong class="command">authpriv</
strong></
span>,
<
span><
strong class="command">ftp</
strong></
span>, <
span><
strong class="command">local0</
strong></
span>, <
span><
strong class="command">local1</
strong></
span>,
<
span><
strong class="command">local2</
strong></
span>, <
span><
strong class="command">local3</
strong></
span>, <
span><
strong class="command">local4</
strong></
span>,
<
span><
strong class="command">local5</
strong></
span>, <
span><
strong class="command">local6</
strong></
span> and
<
span><
strong class="command">local7</
strong></
span>, however not all facilities
How <
span><
strong class="command">syslog</
strong></
span> will handle messages
this facility is described in the <
span><
strong class="command">
syslog.conf</
strong></
span> man
page. If you have a system which uses a very old version of <
span><
strong class="command">syslog</
strong></
span> that
only uses two arguments to the <
span><
strong class="command">openlog()</
strong></
span> function,
then this clause is silently ignored.
The <
span><
strong class="command">severity</
strong></
span> clause works like <
span><
strong class="command">syslog</
strong></
span>'s
"priorities", except that they can also be used if you are writing
straight to a file rather than using <
span><
strong class="command">syslog</
strong></
span>.
Messages which are not at least of the severity level given will
not be selected for the channel; messages of higher severity
If you are using <
span><
strong class="command">syslog</
strong></
span>, then the <
span><
strong class="command">
syslog.conf</
strong></
span> priorities
will also determine what eventually passes through. For example,
defining a channel facility and severity as <
span><
strong class="command">daemon</
strong></
span> and <
span><
strong class="command">debug</
strong></
span> but
only logging <
span><
strong class="command">
daemon.warning</
strong></
span> via <
span><
strong class="command">
syslog.conf</
strong></
span> will
cause messages of severity <
span><
strong class="command">info</
strong></
span> and
<
span><
strong class="command">notice</
strong></
span> to
be dropped. If the situation were reversed, with <
span><
strong class="command">named</
strong></
span> writing
messages of only <
span><
strong class="command">warning</
strong></
span> or higher,
then <
span><
strong class="command">syslogd</
strong></
span> would
print all messages it received from the channel.
The <
span><
strong class="command">stderr</
strong></
span> destination clause
channel to the server's standard error stream. This is intended
use when the server is running as a foreground process, for
when debugging a configuration.
The server can supply extensive debugging information when
it is in debugging mode. If the server's global debug level is
than zero, then debugging mode will be active. The global debug
level is set either by starting the <
span><
strong class="command">named</
strong></
span> server
with the <
code class="option">-d</
code> flag followed by a positive integer,
or by running <
span><
strong class="command">rndc trace</
strong></
span>.
can be set to zero, and debugging mode turned off, by running <
span><
strong class="command">ndc
notrace</
strong></
span>. 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:
<
pre class="programlisting">channel specific_debug_level {
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 <
span><
strong class="command">dynamic</
strong></
span>
server's global debug level to determine what messages to print.
If <
span><
strong class="command">print-time</
strong></
span> has been turned on,
the date and time will be logged. <
span><
strong class="command">print-time</
strong></
span> may
be specified for a <
span><
strong class="command">syslog</
strong></
span> channel,
pointless since <
span><
strong class="command">syslog</
strong></
span> also prints
time. If <
span><
strong class="command">print-category</
strong></
span> is
category of the message will be logged as well. Finally, if <
span><
strong class="command">print-severity</
strong></
span> is
on, then the severity level of the message will be logged. The <
span><
strong class="command">print-</
strong></
span> options may
be used in any combination, and will always be printed in the
order: time, category, severity. Here is an example where all
three <
span><
strong class="command">print-</
strong></
span> options
<
code class="computeroutput">28-Feb-2000 15:05:32.863 general: notice: running</
code>
There are four predefined channels that are used for
<
span><
strong class="command">named</
strong></
span>'s default logging as follows.
used is described in <
a href="Bv9ARM.ch06.html#the_category_phrase" title="The category Phrase">the section called “The <
span><
strong class="command">category</
strong></
span> Phrase”</
a>.
<
pre class="programlisting">channel default_syslog {
syslog daemon; // send to syslog's daemon
severity info; // only send priority info
// Note: stderr is used instead
// if the server is started
severity dynamic; // log at the server's
stderr; // writes to stderr
severity info; // only send priority info
null; // toss anything sent to
The <
span><
strong class="command">default_debug</
strong></
span> channel has the
property that it only produces output when the server's debug
nonzero. It normally writes to a file <
code class="filename">
named.run</
code>
in the server's working directory.
For security reasons, when the "<
code class="option">-u</
code>"
command line option is used, the <
code class="filename">
named.run</
code> file
is created only after <
span><
strong class="command">named</
strong></
span> has
new UID, and any debug output generated while <
span><
strong class="command">named</
strong></
span> 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="option">-g</
code>"
option and redirect standard error to a file.
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
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="the_category_phrase"></
a>The <
span><
strong class="command">category</
strong></
span> Phrase</
h4></
div></
div></
div>
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
in that category will be sent to the <
span><
strong class="command">default</
strong></
span> category
instead. If you don't specify a default category, the following
"default default" is used:
<
pre class="programlisting">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
<
pre class="programlisting">channel my_security_channel {
To discard all messages in a category, specify the <
span><
strong class="command">null</
strong></
span> channel:
<
pre class="programlisting">category xfer-out { null; };
category notify { null; };
Following are the available categories and brief descriptions
of the types of log information they contain. More
categories may be added in future <
span class="acronym">BIND</
span> releases.
<
div class="informaltable"><
table border="1">
<
p><
span><
strong class="command">default</
strong></
span></
p>
The default category defines the logging
options for those categories where no specific
<
p><
span><
strong class="command">general</
strong></
span></
p>
The catch-all. Many things still aren't
classified into categories, and they all end up here.
<
p><
span><
strong class="command">database</
strong></
span></
p>
Messages relating to the databases used
internally by the name server to store zone and cache
<
p><
span><
strong class="command">security</
strong></
span></
p>
Approval and denial of requests.
<
p><
span><
strong class="command">config</
strong></
span></
p>
Configuration file parsing and processing.
<
p><
span><
strong class="command">resolver</
strong></
span></
p>
DNS resolution, such as the recursive
lookups performed on behalf of clients by a caching name
<
p><
span><
strong class="command">xfer-in</
strong></
span></
p>
Zone transfers the server is receiving.
<
p><
span><
strong class="command">xfer-out</
strong></
span></
p>
Zone transfers the server is sending.
<
p><
span><
strong class="command">notify</
strong></
span></
p>
<
p><
span><
strong class="command">client</
strong></
span></
p>
Processing of client requests.
<
p><
span><
strong class="command">unmatched</
strong></
span></
p>
Messages that named was unable to determine the
class of or for which there was no matching <
span><
strong class="command">view</
strong></
span>.
A one line summary is also logged to the <
span><
strong class="command">client</
strong></
span> category.
This category is best sent to a file or stderr, by
the <
span><
strong class="command">null</
strong></
span> channel.
<
p><
span><
strong class="command">network</
strong></
span></
p>
<
p><
span><
strong class="command">update</
strong></
span></
p>
<
p><
span><
strong class="command">update-security</
strong></
span></
p>
Approval and denial of update requests.
<
p><
span><
strong class="command">queries</
strong></
span></
p>
Specify where queries should be logged to.
At startup, specifing the category <
span><
strong class="command">queries</
strong></
span> will also
enable query logging unless <
span><
strong class="command">querylog</
strong></
span> option has been
The query log entry reports the client's IP address and
query name, class and type. It also reports whether the
flag was set (+ if set, - if not set), EDNS was in use
<
code class="computeroutput">client 127.0.0.1#62536: query:
www.example.com IN AAAA +SE</
code>
<
code class="computeroutput">client ::1#62537: query:
www.example.net IN AAAA -SE</
code>
<
p><
span><
strong class="command">dispatch</
strong></
span></
p>
Dispatching of incoming packets to the
server modules where they are to be processed.
<
p><
span><
strong class="command">dnssec</
strong></
span></
p>
DNSSEC and TSIG protocol processing.
<
p><
span><
strong class="command">lame-servers</
strong></
span></
p>
Lame servers. These are misconfigurations
in remote servers, discovered by BIND 9 when trying to
those servers during resolution.
<
p><
span><
strong class="command">delegation-only</
strong></
span></
p>
Delegation only. Logs queries that have have
been forced to NXDOMAIN as the result of a
a <
span><
strong class="command">delegation-only</
strong></
span> in a
hint or stub zone declaration.
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2546486"></
a><
span><
strong class="command">lwres</
strong></
span> Statement Grammar</
h3></
div></
div></
div>
This is the grammar of the <
span><
strong class="command">lwres</
strong></
span>
statement in the <
code class="filename">
named.conf</
code> file:
<
pre class="programlisting"><
span><
strong class="command">lwres</
strong></
span> {
[<
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>]
[<
span class="optional"> view <
em class="replaceable"><
code>view_name</
code></
em>; </
span>]
[<
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>]
[<
span class="optional"> ndots <
em class="replaceable"><
code>number</
code></
em>; </
span>]
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2546560"></
a><
span><
strong class="command">lwres</
strong></
span> Statement Definition and Usage</
h3></
div></
div></
div>
The <
span><
strong class="command">lwres</
strong></
span> statement configures the
server to also act as a lightweight resolver server, see
<
a href="Bv9ARM.ch05.html#lwresd" title="Running a Resolver Daemon">the section called “Running a Resolver Daemon”</
a>. There may be be multiple
<
span><
strong class="command">lwres</
strong></
span> statements configuring
lightweight resolver servers with different properties.
The <
span><
strong class="command">listen-on</
strong></
span> statement specifies a
addresses (and ports) that this instance of a lightweight resolver
should accept requests on. If no port is specified, port 921 is
If this statement is omitted, requests will be accepted on
The <
span><
strong class="command">view</
strong></
span> statement binds this
lightweight resolver daemon to a view in the DNS namespace, so that
response will be constructed in the same manner as a normal DNS
matching this view. If this statement is omitted, the default view
used, and if there is no default view, an error is triggered.
The <
span><
strong class="command">search</
strong></
span> statement is equivalent to
<
span><
strong class="command">search</
strong></
span> statement in
which are appended to relative names in queries.
The <
span><
strong class="command">ndots</
strong></
span> statement is equivalent to
<
span><
strong class="command">ndots</
strong></
span> statement in
number of dots in a relative domain name that should result in an
exact match lookup before search path elements are appended.
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2546624"></
a><
span><
strong class="command">masters</
strong></
span> Statement Grammar</
h3></
div></
div></
div>
<
pre class="programlisting">
<
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>] };
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2546667"></
a><
span><
strong class="command">masters</
strong></
span> Statement Definition and
Usage</
h3></
div></
div></
div>
<
p><
span><
strong class="command">masters</
strong></
span>
lists allow for a common set of masters to be easily used by
multiple stub and slave zones.
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2546682"></
a><
span><
strong class="command">options</
strong></
span> Statement Grammar</
h3></
div></
div></
div>
This is the grammar of the <
span><
strong class="command">options</
strong></
span>
statement in the <
code class="filename">
named.conf</
code> file:
<
pre class="programlisting">options {
[<
span class="optional"> version <
em class="replaceable"><
code>version_string</
code></
em>; </
span>]
[<
span class="optional"> hostname <
em class="replaceable"><
code>hostname_string</
code></
em>; </
span>]
[<
span class="optional"> server-id <
em class="replaceable"><
code>server_id_string</
code></
em>; </
span>]
[<
span class="optional"> directory <
em class="replaceable"><
code>path_name</
code></
em>; </
span>]
[<
span class="optional"> key-directory <
em class="replaceable"><
code>path_name</
code></
em>; </
span>]
[<
span class="optional"> named-xfer <
em class="replaceable"><
code>path_name</
code></
em>; </
span>]
[<
span class="optional"> tkey-domain <
em class="replaceable"><
code>domainname</
code></
em>; </
span>]
[<
span class="optional"> tkey-dhkey <
em class="replaceable"><
code>key_name</
code></
em> <
em class="replaceable"><
code>key_tag</
code></
em>; </
span>]
[<
span class="optional"> dump-file <
em class="replaceable"><
code>path_name</
code></
em>; </
span>]
[<
span class="optional"> memstatistics-file <
em class="replaceable"><
code>path_name</
code></
em>; </
span>]
[<
span class="optional"> pid-file <
em class="replaceable"><
code>path_name</
code></
em>; </
span>]
[<
span class="optional"> statistics-file <
em class="replaceable"><
code>path_name</
code></
em>; </
span>]
[<
span class="optional"> zone-statistics <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> auth-nxdomain <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> deallocate-on-exit <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> dialup <
em class="replaceable"><
code>dialup_option</
code></
em>; </
span>]
[<
span class="optional"> fake-iquery <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> fetch-glue <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> flush-zones-on-shutdown <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> has-old-clients <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> host-statistics <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> host-statistics-max <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> minimal-responses <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> multiple-cnames <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
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>]
[<
span class="optional"> recursion <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> rfc2308-type1 <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> use-id-pool <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> maintain-ixfr-base <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> dnssec-enable <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> dnssec-lookaside <
em class="replaceable"><
code>domain</
code></
em> trust-anchor <
em class="replaceable"><
code>domain</
code></
em>; </
span>]
[<
span class="optional"> dnssec-must-be-secure <
em class="replaceable"><
code>domain yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> forward ( <
em class="replaceable"><
code>only</
code></
em> | <
em class="replaceable"><
code>first</
code></
em> ); </
span>]
[<
span class="optional"> forwarders { <
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>]
[<
span class="optional"> dual-stack-servers [<
span class="optional">port <
em class="replaceable"><
code>ip_port</
code></
em></
span>] {
( <
em class="replaceable"><
code>domain_name</
code></
em> [<
span class="optional">port <
em class="replaceable"><
code>ip_port</
code></
em></
span>] |
<
em class="replaceable"><
code>ip_addr</
code></
em> [<
span class="optional">port <
em class="replaceable"><
code>ip_port</
code></
em></
span>] ) ;
[<
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> )
( <
em class="replaceable"><
code>warn</
code></
em> | <
em class="replaceable"><
code>fail</
code></
em> | <
em class="replaceable"><
code>ignore</
code></
em> ); </
span>]
[<
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>]
[<
span class="optional"> check-wildcard <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> check-integrity <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> check-sibling <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> allow-notify { <
em class="replaceable"><
code>address_match_list</
code></
em> }; </
span>]
[<
span class="optional"> allow-query { <
em class="replaceable"><
code>address_match_list</
code></
em> }; </
span>]
[<
span class="optional"> allow-query-cache { <
em class="replaceable"><
code>address_match_list</
code></
em> }; </
span>]
[<
span class="optional"> allow-transfer { <
em class="replaceable"><
code>address_match_list</
code></
em> }; </
span>]
[<
span class="optional"> allow-recursion { <
em class="replaceable"><
code>address_match_list</
code></
em> }; </
span>]
[<
span class="optional"> allow-update { <
em class="replaceable"><
code>address_match_list</
code></
em> }; </
span>]
[<
span class="optional"> allow-update-forwarding { <
em class="replaceable"><
code>address_match_list</
code></
em> }; </
span>]
[<
span class="optional"> allow-v6-synthesis { <
em class="replaceable"><
code>address_match_list</
code></
em> }; </
span>]
[<
span class="optional"> blackhole { <
em class="replaceable"><
code>address_match_list</
code></
em> }; </
span>]
[<
span class="optional"> avoid-v4-udp-ports { <
em class="replaceable"><
code>port_list</
code></
em> }; </
span>]
[<
span class="optional"> avoid-v6-udp-ports { <
em class="replaceable"><
code>port_list</
code></
em> }; </
span>]
[<
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>]
[<
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>]
[<
span class="optional"> query-source ( ( <
em class="replaceable"><
code>ip4_addr</
code></
em> | <
em class="replaceable"><
code>*</
code></
em> )
[<
span class="optional"> port ( <
em class="replaceable"><
code>ip_port</
code></
em> | <
em class="replaceable"><
code>*</
code></
em> ) </
span>] |
[<
span class="optional"> address ( <
em class="replaceable"><
code>ip4_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>]
[<
span class="optional"> query-source-v6 ( ( <
em class="replaceable"><
code>ip6_addr</
code></
em> | <
em class="replaceable"><
code>*</
code></
em> )
[<
span class="optional"> port ( <
em class="replaceable"><
code>ip_port</
code></
em> | <
em class="replaceable"><
code>*</
code></
em> ) </
span>] |
[<
span class="optional"> address ( <
em class="replaceable"><
code>ip6_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>]
[<
span class="optional"> max-transfer-time-in <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> max-transfer-time-out <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> max-transfer-idle-in <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> max-transfer-idle-out <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> tcp-clients <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> recursive-clients <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> serial-query-rate <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> serial-queries <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> tcp-listen-queue <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> transfer-format <
em class="replaceable"><
code>( one-answer | many-answers )</
code></
em>; </
span>]
[<
span class="optional"> transfers-in <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> transfers-out <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> transfers-per-ns <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
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>]
[<
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>]
[<
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>]
[<
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>]
[<
span class="optional"> use-alt-transfer-source <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
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>]
[<
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>]
[<
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>]
[<
span class="optional"> max-ixfr-log-size <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> max-journal-size <
em class="replaceable"><
code>size_spec</
code></
em>; </
span>]
[<
span class="optional"> coresize <
em class="replaceable"><
code>size_spec</
code></
em> ; </
span>]
[<
span class="optional"> datasize <
em class="replaceable"><
code>size_spec</
code></
em> ; </
span>]
[<
span class="optional"> files <
em class="replaceable"><
code>size_spec</
code></
em> ; </
span>]
[<
span class="optional"> stacksize <
em class="replaceable"><
code>size_spec</
code></
em> ; </
span>]
[<
span class="optional"> cleaning-interval <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> heartbeat-interval <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> interface-interval <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> statistics-interval <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> topology { <
em class="replaceable"><
code>address_match_list</
code></
em> }</
span>];
[<
span class="optional"> sortlist { <
em class="replaceable"><
code>address_match_list</
code></
em> }</
span>];
[<
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>] };
[<
span class="optional"> lame-ttl <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> max-ncache-ttl <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> max-cache-ttl <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> sig-validity-interval <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> min-roots <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> use-ixfr <
em class="replaceable"><
code>yes_or_no</
code></
em> ; </
span>]
[<
span class="optional"> provide-ixfr <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> request-ixfr <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> treat-cr-as-space <
em class="replaceable"><
code>yes_or_no</
code></
em> ; </
span>]
[<
span class="optional"> min-refresh-time <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> max-refresh-time <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> min-retry-time <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> max-retry-time <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> port <
em class="replaceable"><
code>ip_port</
code></
em>; </
span>]
[<
span class="optional"> additional-from-auth <
em class="replaceable"><
code>yes_or_no</
code></
em> ; </
span>]
[<
span class="optional"> additional-from-cache <
em class="replaceable"><
code>yes_or_no</
code></
em> ; </
span>]
[<
span class="optional"> random-device <
em class="replaceable"><
code>path_name</
code></
em> ; </
span>]
[<
span class="optional"> max-cache-size <
em class="replaceable"><
code>size_spec</
code></
em> ; </
span>]
[<
span class="optional"> match-mapped-addresses <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
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>]
[<
span class="optional"> edns-udp-size <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> root-delegation-only [<
span class="optional"> exclude { <
em class="replaceable"><
code>namelist</
code></
em> } </
span>] ; </
span>]
[<
span class="optional"> querylog <
em class="replaceable"><
code>yes_or_no</
code></
em> ; </
span>]
[<
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>]
[<
span class="optional"> use-additional-cache <
em class="replaceable"><
code>yes_or_no</
code></
em> ; </
span>]
[<
span class="optional"> acache-cleaning-interval <
em class="replaceable"><
code>number</
code></
em>; </
span>]
[<
span class="optional"> max-acache-size <
em class="replaceable"><
code>size_spec</
code></
em> ; </
span>]
[<
span class="optional"> clients-per-query <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> max-clients-per-query <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> masterfile-format (<
code class="constant">text</
code>|<
code class="constant">raw</
code>) ; </
span>]
[<
span class="optional"> empty-server <
em class="replaceable"><
code>name</
code></
em> ; </
span>]
[<
span class="optional"> empty-contact <
em class="replaceable"><
code>name</
code></
em> ; </
span>]
[<
span class="optional"> empty-zones-enable <
em class="replaceable"><
code>yes_or_no</
code></
em> ; </
span>]
[<
span class="optional"> disable-empty-zone <
em class="replaceable"><
code>zone_name</
code></
em> ; </
span>]
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="options"></
a><
span><
strong class="command">options</
strong></
span> Statement Definition and
Usage</
h3></
div></
div></
div>
The <
span><
strong class="command">options</
strong></
span> statement sets up global
to be used by <
span class="acronym">BIND</
span>. This statement
once in a configuration file. If there is no <
span><
strong class="command">options</
strong></
span>
statement, an options block with each option set to its default will
<
div class="variablelist"><
dl>
<
dt><
span class="term"><
span><
strong class="command">directory</
strong></
span></
span></
dt>
The working directory of the server.
Any non-absolute pathnames in the configuration file will be
as relative to this directory. The default location for most
If a directory is not specified, the working directory
defaults to `<
code class="filename">.</
code>', the directory from
was started. The directory specified should be an absolute
<
dt><
span class="term"><
span><
strong class="command">key-directory</
strong></
span></
span></
dt>
When performing dynamic update of secure zones, the
directory where the public and private key files should be
if different than the current working directory. The
must be an absolute path.
<
dt><
span class="term"><
span><
strong class="command">named-xfer</
strong></
span></
span></
dt>
<
span class="emphasis"><
em>This option is obsolete.</
em></
span>
It was used in <
span class="acronym">BIND</
span> 8 to
specify the pathname to the <
span><
strong class="command">named-xfer</
strong></
span> program.
In <
span class="acronym">BIND</
span> 9, no separate <
span><
strong class="command">named-xfer</
strong></
span> program is
needed; its functionality is built into the name server.
<
dt><
span class="term"><
span><
strong class="command">tkey-domain</
strong></
span></
span></
dt>
The domain appended to the names of all
shared keys generated with
<
span><
strong class="command">TKEY</
strong></
span>. When a client
requests a <
span><
strong class="command">TKEY</
strong></
span> exchange, it
the desired name for the key. If present, the name of the
key will be "<
code class="varname">client specified part</
code>" +
"<
code class="varname">tkey-domain</
code>".
Otherwise, the name of the shared key will be "<
code class="varname">random hex
digits</
code>" + "<
code class="varname">tkey-domain</
code>". In most cases,
the <
span><
strong class="command">domainname</
strong></
span> should be the
<
dt><
span class="term"><
span><
strong class="command">tkey-dhkey</
strong></
span></
span></
dt>
The Diffie-Hellman key used by the server
to generate shared keys with clients using the Diffie-Hellman
of <
span><
strong class="command">TKEY</
strong></
span>. The server must be
public and private keys from files in the working directory.
most cases, the keyname should be the server's host name.
<
dt><
span class="term"><
span><
strong class="command">dump-file</
strong></
span></
span></
dt>
The pathname of the file the server dumps
the database to when instructed to do so with
<
span><
strong class="command">rndc dumpdb</
strong></
span>.
If not specified, the default is <
code class="filename">
named_dump.db</
code>.
<
dt><
span class="term"><
span><
strong class="command">memstatistics-file</
strong></
span></
span></
dt>
The pathname of the file the server writes memory
usage statistics to on exit. If not specified,
<
dt><
span class="term"><
span><
strong class="command">pid-file</
strong></
span></
span></
dt>
The pathname of the file the server writes its process ID
in. If not specified, the default is <
code class="filename">/
var/
run/
named.pid</
code>.
The pid-file is used by programs that want to send signals to
name server. Specifying <
span><
strong class="command">pid-file none</
strong></
span> disables the
use of a PID file — no file will be written and any
existing one will be removed. Note that <
span><
strong class="command">none</
strong></
span>
is a keyword, not a file name, and therefore is not enclosed
<
dt><
span class="term"><
span><
strong class="command">statistics-file</
strong></
span></
span></
dt>
The pathname of the file the server appends statistics
to when instructed to do so using <
span><
strong class="command">rndc stats</
strong></
span>.
If not specified, the default is <
code class="filename">
named.stats</
code> in the
server's current directory. The format of the file is
in <
a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called “The Statistics File”</
a>
<
dt><
span class="term"><
span><
strong class="command">port</
strong></
span></
span></
dt>
The
UDP/
TCP port number the server uses for
receiving and sending DNS protocol traffic.
The default is 53. This option is mainly intended for server
a server using a port other than 53 will not be able to
<
dt><
span class="term"><
span><
strong class="command">random-device</
strong></
span></
span></
dt>
The source of entropy to be used by the server. Entropy is
for DNSSEC operations, such as TKEY transactions and dynamic
zones. This options specifies the device (or file) from which
entropy. If this is a file, operations requiring entropy will
file has been exhausted. If not specified, the default value
(or equivalent) when present, and none otherwise. The
<
span><
strong class="command">random-device</
strong></
span> option takes
the initial configuration load at server startup time and
is ignored on subsequent reloads.
<
dt><
span class="term"><
span><
strong class="command">preferred-glue</
strong></
span></
span></
dt>
If specified the listed type (A or AAAA) will be emitted
in the additional section of a query response.
The default is not to preference any type (NONE).
<
dt><
span class="term"><
span><
strong class="command">root-delegation-only</
strong></
span></
span></
dt>
Turn on enforcement of delegation-only in TLDs and root zones
Note some TLDs are NOT delegation only (
e.g. "DE", "LV", "US"
<
pre class="programlisting">
root-delegation-only exclude { "de"; "lv"; "us"; "museum"; };
<
dt><
span class="term"><
span><
strong class="command">disable-algorithms</
strong></
span></
span></
dt>
Disable the specified DNSSEC algorithms at and below the
Multiple <
span><
strong class="command">disable-algorithms</
strong></
span>
Only the most specific will be applied.
<
dt><
span class="term"><
span><
strong class="command">dnssec-lookaside</
strong></
span></
span></
dt>
When set <
span><
strong class="command">dnssec-lookaside</
strong></
span>
validator with an alternate method to validate DNSKEY records
top of a zone. When a DNSKEY is at or below a domain
deepest <
span><
strong class="command">dnssec-lookaside</
strong></
span>, and
the normal dnssec validation
has left the key untrusted, the trust-anchor will be append to
name and a DLV record will be looked up to see if it can
key. If the DLV record validates a DNSKEY (similarly to the
record does) the DNSKEY RRset is deemed to be trusted.
<
dt><
span class="term"><
span><
strong class="command">dnssec-must-be-secure</
strong></
span></
span></
dt>
Specify hierarchies which must / may not be secure (signed and
If <
strong class="userinput"><
code>yes</
code></
strong> then named will only accept
If <
strong class="userinput"><
code>no</
code></
strong> then normal dnssec validation
allowing for insecure answers to be accepted.
The specified domain must be under a <
span><
strong class="command">trusted-key</
strong></
span> or
<
span><
strong class="command">dnssec-lookaside</
strong></
span> must be
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="boolean_options"></
a>Boolean Options</
h4></
div></
div></
div>
<
div class="variablelist"><
dl>
<
dt><
span class="term"><
span><
strong class="command">auth-nxdomain</
strong></
span></
span></
dt>
If <
strong class="userinput"><
code>yes</
code></
strong>, then the <
span><
strong class="command">AA</
strong></
span> bit
is always set on NXDOMAIN responses, even if the server is
authoritative. The default is <
strong class="userinput"><
code>no</
code></
strong>;
a change from <
span class="acronym">BIND</
span> 8. If you
are using very old DNS software, you
may need to set it to <
strong class="userinput"><
code>yes</
code></
strong>.
<
dt><
span class="term"><
span><
strong class="command">deallocate-on-exit</
strong></
span></
span></
dt>
This option was used in <
span class="acronym">BIND</
span>
for memory leaks on exit. <
span class="acronym">BIND</
span> 9 ignores the option and always performs
<
dt><
span class="term"><
span><
strong class="command">dialup</
strong></
span></
span></
dt>
If <
strong class="userinput"><
code>yes</
code></
strong>, then the
server treats all zones as if they are doing zone transfers
a dial on demand dialup link, which can be brought up by
originating from this server. This has different effects
to zone type and concentrates the zone maintenance so that
happens in a short interval, once every <
span><
strong class="command">heartbeat-interval</
strong></
span> and
hopefully during the one call. It also suppresses some of
zone maintenance traffic. The default is <
strong class="userinput"><
code>no</
code></
strong>.
The <
span><
strong class="command">dialup</
strong></
span> option
may also be specified in the <
span><
strong class="command">view</
strong></
span> and
<
span><
strong class="command">zone</
strong></
span> statements,
in which case it overrides the global <
span><
strong class="command">dialup</
strong></
span>
If the zone is a master zone then the server will send out a
request to all the slaves (default). This should trigger the
number check in the slave (providing it supports NOTIFY)
to verify the zone while the connection is active.
The set of servers to which NOTIFY is sent can be controlled
<
span><
strong class="command">notify</
strong></
span> and <
span><
strong class="command">also-notify</
strong></
span>.
zone is a slave or stub zone, then the server will suppress
"zone up to date" (refresh) queries and only perform them
<
span><
strong class="command">heartbeat-interval</
strong></
span> expires in
Finer control can be achieved by using
<
strong class="userinput"><
code>notify</
code></
strong> which only sends NOTIFY
<
strong class="userinput"><
code>notify-passive</
code></
strong> which sends NOTIFY
suppresses the normal refresh queries, <
strong class="userinput"><
code>refresh</
code></
strong>
which suppresses normal refresh processing and sends refresh
when the <
span><
strong class="command">heartbeat-interval</
strong></
span>
<
strong class="userinput"><
code>passive</
code></
strong> which just disables normal
<
div class="informaltable"><
table border="1">
<
p><
span><
strong class="command">no</
strong></
span> (default)</
p>
<
p><
span><
strong class="command">yes</
strong></
span></
p>
<
p><
span><
strong class="command">notify</
strong></
span></
p>
<
p><
span><
strong class="command">refresh</
strong></
span></
p>
<
p><
span><
strong class="command">passive</
strong></
span></
p>
<
p><
span><
strong class="command">notify-passive</
strong></
span></
p>
Note that normal NOTIFY processing is not affected by
<
span><
strong class="command">dialup</
strong></
span>.
<
dt><
span class="term"><
span><
strong class="command">fake-iquery</
strong></
span></
span></
dt>
In <
span class="acronym">BIND</
span> 8, this option
enabled simulating the obsolete DNS query type
IQUERY. <
span class="acronym">BIND</
span> 9 never does
<
dt><
span class="term"><
span><
strong class="command">fetch-glue</
strong></
span></
span></
dt>
In BIND 8, <
strong class="userinput"><
code>fetch-glue yes</
code></
strong>
caused the server to attempt to fetch glue resource records
didn't have when constructing the additional
data section of a response. This is now considered a bad
and BIND 9 never does it.
<
dt><
span class="term"><
span><
strong class="command">flush-zones-on-shutdown</
strong></
span></
span></
dt>
When the nameserver exits due receiving SIGTERM,
flush / do not flush any pending zone writes. The default
<
span><
strong class="command">flush-zones-on-shutdown</
strong></
span> <
strong class="userinput"><
code>no</
code></
strong>.
<
dt><
span class="term"><
span><
strong class="command">has-old-clients</
strong></
span></
span></
dt>
This option was incorrectly implemented
in <
span class="acronym">BIND</
span> 8, and is ignored by <
span class="acronym">BIND</
span> 9.
To achieve the intended effect
<
span><
strong class="command">has-old-clients</
strong></
span> <
strong class="userinput"><
code>yes</
code></
strong>, specify
the two separate options <
span><
strong class="command">auth-nxdomain</
strong></
span> <
strong class="userinput"><
code>yes</
code></
strong>
and <
span><
strong class="command">rfc2308-type1</
strong></
span> <
strong class="userinput"><
code>no</
code></
strong> instead.
<
dt><
span class="term"><
span><
strong class="command">host-statistics</
strong></
span></
span></
dt>
In BIND 8, this enables keeping of
statistics for every host that the name server interacts
Not implemented in BIND 9.
<
dt><
span class="term"><
span><
strong class="command">maintain-ixfr-base</
strong></
span></
span></
dt>
<
span class="emphasis"><
em>This option is obsolete</
em></
span>.
It was used in <
span class="acronym">BIND</
span> 8 to
determine whether a transaction log was
kept for Incremental Zone Transfer. <
span class="acronym">BIND</
span> 9 maintains a transaction
log whenever possible. If you need to disable outgoing
transfers, use <
span><
strong class="command">provide-ixfr</
strong></
span> <
strong class="userinput"><
code>no</
code></
strong>.
<
dt><
span class="term"><
span><
strong class="command">minimal-responses</
strong></
span></
span></
dt>
If <
strong class="userinput"><
code>yes</
code></
strong>, then when generating
responses the server will only add records to the authority
and additional data sections when they are required (
e.g. delegations, negative responses). This may improve the
performance of the server.
The default is <
strong class="userinput"><
code>no</
code></
strong>.
<
dt><
span class="term"><
span><
strong class="command">multiple-cnames</
strong></
span></
span></
dt>
This option was used in <
span class="acronym">BIND</
span> 8 to allow
a domain name to have multiple CNAME records in violation of
the DNS standards. <
span class="acronym">BIND</
span> 9.2 onwards
always strictly enforces the CNAME rules both in master
files and dynamic updates.
<
dt><
span class="term"><
span><
strong class="command">notify</
strong></
span></
span></
dt>
If <
strong class="userinput"><
code>yes</
code></
strong> (the default),
DNS NOTIFY messages are sent when a zone the server is
changes, see <
a href="Bv9ARM.ch04.html#notify" title="Notify">the section called “Notify”</
a>. The messages are
servers listed in the zone's NS records (except the master
in the SOA MNAME field), and to any servers listed in the
<
span><
strong class="command">also-notify</
strong></
span> option.
If <
strong class="userinput"><
code>master-only</
code></
strong>, notifies are only
If <
strong class="userinput"><
code>explicit</
code></
strong>, notifies are sent only
servers explicitly listed using <
span><
strong class="command">also-notify</
strong></
span>.
If <
strong class="userinput"><
code>no</
code></
strong>, no notifies are sent.
The <
span><
strong class="command">notify</
strong></
span> option may also be
specified in the <
span><
strong class="command">zone</
strong></
span>
in which case it overrides the <
span><
strong class="command">options notify</
strong></
span> statement.
It would only be necessary to turn off this option if it
<
dt><
span class="term"><
span><
strong class="command">recursion</
strong></
span></
span></
dt>
If <
strong class="userinput"><
code>yes</
code></
strong>, and a
DNS query requests recursion, then the server will attempt
all the work required to answer the query. If recursion is
and the server does not already know the answer, it will
referral response. The default is
<
strong class="userinput"><
code>yes</
code></
strong>.
Note that setting <
span><
strong class="command">recursion no</
strong></
span> does not prevent
clients from getting data from the server's cache; it only
prevents new data from being cached as an effect of client
Caching may still occur as an effect the server's internal
operation, such as NOTIFY address lookups.
See also <
span><
strong class="command">fetch-glue</
strong></
span> above.
<
dt><
span class="term"><
span><
strong class="command">rfc2308-type1</
strong></
span></
span></
dt>
Setting this to <
strong class="userinput"><
code>yes</
code></
strong> will
cause the server to send NS records along with the SOA
answers. The default is <
strong class="userinput"><
code>no</
code></
strong>.
<
div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<
h3 class="title">Note</
h3>
Not yet implemented in <
span class="acronym">BIND</
span>
<
dt><
span class="term"><
span><
strong class="command">use-id-pool</
strong></
span></
span></
dt>
<
span class="emphasis"><
em>This option is obsolete</
em></
span>.
<
span class="acronym">BIND</
span> 9 always allocates query
<
dt><
span class="term"><
span><
strong class="command">zone-statistics</
strong></
span></
span></
dt>
If <
strong class="userinput"><
code>yes</
code></
strong>, the server will collect
statistical data on all zones (unless specifically turned
on a per-zone basis by specifying <
span><
strong class="command">zone-statistics no</
strong></
span>
in the <
span><
strong class="command">zone</
strong></
span> statement).
These statistics may be accessed
using <
span><
strong class="command">rndc stats</
strong></
span>, which will
dump them to the file listed
in the <
span><
strong class="command">statistics-file</
strong></
span>. See
also <
a href="Bv9ARM.ch06.html#statsfile" title="The Statistics File">the section called “The Statistics File”</
a>.
<
dt><
span class="term"><
span><
strong class="command">use-ixfr</
strong></
span></
span></
dt>
<
span class="emphasis"><
em>This option is obsolete</
em></
span>.
If you need to disable IXFR to a particular server or
the information on the <
span><
strong class="command">provide-ixfr</
strong></
span> option
in <
a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and Usage">the section called “<
span><
strong class="command">server</
strong></
span> Statement Definition and
<
a href="Bv9ARM.ch04.html#incremental_zone_transfers" title="Incremental Zone Transfers (IXFR)">the section called “Incremental Zone Transfers (IXFR)”</
a>.
<
dt><
span class="term"><
span><
strong class="command">provide-ixfr</
strong></
span></
span></
dt>
<
span><
strong class="command">provide-ixfr</
strong></
span> in
<
a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and Usage">the section called “<
span><
strong class="command">server</
strong></
span> Statement Definition and
<
dt><
span class="term"><
span><
strong class="command">request-ixfr</
strong></
span></
span></
dt>
<
span><
strong class="command">request-ixfr</
strong></
span> in
<
a href="Bv9ARM.ch06.html#server_statement_definition_and_usage" title="server Statement Definition and Usage">the section called “<
span><
strong class="command">server</
strong></
span> Statement Definition and
<
dt><
span class="term"><
span><
strong class="command">treat-cr-as-space</
strong></
span></
span></
dt>
This option was used in <
span class="acronym">BIND</
span>
the server treat carriage return ("<
span><
strong class="command">\r</
strong></
span>") characters the same way
as a space or tab character,
to facilitate loading of zone files on a UNIX system that
on an NT or DOS machine. In <
span class="acronym">BIND</
span> 9, both UNIX "<
span><
strong class="command">\n</
strong></
span>"
and
NT/
DOS "<
span><
strong class="command">\r\n</
strong></
span>" newlines
and the option is ignored.
<
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>
These options control the behavior of an authoritative
answering queries which have additional data, or when
When both of these options are set to <
strong class="userinput"><
code>yes</
code></
strong>
query is being answered from authoritative data (a zone
configured into the server), the additional data section of
reply will be filled in using data from other authoritative
and from the cache. In some situations this is undesirable,
as when there is concern over the correctness of the cache,
in servers where slave zones may be added and modified by
untrusted third parties. Also, avoiding
the search for this additional data will speed up server
at the possible expense of additional queries to resolve
otherwise be provided in the additional section.
For example, if a query asks for an MX record for host <
code class="literal">
foo.example.com</
code>,
and the record found is "<
code class="literal">MX 10
mail.example.net</
code>", normally the address
records (A and AAAA) for <
code class="literal">
mail.example.net</
code> will be provided as well,
if known, even though they are not in the
example.com zone.
Setting these options to <
span><
strong class="command">no</
strong></
span>
disables this behavior and makes
the server only search for additional data in the zone it
These options are intended for use in authoritative-only
servers, or in authoritative-only views. Attempts to set
them to <
span><
strong class="command">no</
strong></
span> without also
<
span><
strong class="command">recursion no</
strong></
span> will cause the
ignore the options and log a warning message.
Specifying <
span><
strong class="command">additional-from-cache no</
strong></
span> actually
disables the use of the cache not only for additional data
but also when looking up the answer. This is usually the
behavior in an authoritative-only server where the
the cached data is an issue.
When a name server is non-recursively queried for a name
below the apex of any served zone, it normally answers with
"upwards referral" to the root servers or the servers of
known parent of the query name. Since the data in an
comes from the cache, the server will not be able to provide
referrals when <
span><
strong class="command">additional-from-cache no</
strong></
span>
has been specified. Instead, it will respond to such
with REFUSED. This should not cause any problems since
upwards referrals are not required for the resolution
<
dt><
span class="term"><
span><
strong class="command">match-mapped-addresses</
strong></
span></
span></
dt>
If <
strong class="userinput"><
code>yes</
code></
strong>, then an
IPv4-mapped IPv6 address will match any address match
list entries that match the corresponding IPv4 address.
Enabling this option is sometimes useful on IPv6-enabled
systems, to work around a kernel quirk that causes IPv4
TCP connections such as zone transfers to be accepted
on an IPv6 socket using mapped addresses, causing
address match lists designed for IPv4 to fail to match.
The use of this option for any other purpose is discouraged.
<
dt><
span class="term"><
span><
strong class="command">ixfr-from-differences</
strong></
span></
span></
dt>
When 'yes' and the server loads a new version of a master
zone from its zone file or receives a new version of a slave
file by a non-incremental zone transfer, it will compare
the new version to the previous one and calculate a set
of differences. The differences are then logged in the
zone's journal file such that the changes can be transmitted
to downstream slaves as an incremental zone transfer.
By allowing incremental zone transfers to be used for
non-dynamic zones, this option saves bandwidth at the
expense of increased CPU and memory consumption at the
In particular, if the new version of a zone is completely
different from the previous one, the set of differences
will be of a size comparable to the combined size of the
old and new zone version, and the server will need to
temporarily allocate memory to hold this complete
<
p><
span><
strong class="command">ixfr-from-differences</
strong></
span>
also accepts <
span><
strong class="command">master</
strong></
span> and
<
span><
strong class="command">slave</
strong></
span> at the view and options
<
span><
strong class="command">ixfr-from-differences</
strong></
span> to apply to
all <
span><
strong class="command">master</
strong></
span> or
<
span><
strong class="command">slave</
strong></
span> zones respectively.
<
dt><
span class="term"><
span><
strong class="command">multi-master</
strong></
span></
span></
dt>
This should be set when you have multiple masters for a zone
addresses refer to different machines. If 'yes' named will
when the serial number on the master is less than what named
has. The default is <
strong class="userinput"><
code>no</
code></
strong>.
<
dt><
span class="term"><
span><
strong class="command">dnssec-enable</
strong></
span></
span></
dt>
Enable DNSSEC support in named. Unless set to <
strong class="userinput"><
code>yes</
code></
strong>
named behaves as if it does not support DNSSEC.
The default is <
strong class="userinput"><
code>no</
code></
strong>.
<
dt><
span class="term"><
span><
strong class="command">querylog</
strong></
span></
span></
dt>
Specify whether query logging should be started when named
If <
span><
strong class="command">querylog</
strong></
span> is not specified
is determined by the presence of the logging category <
span><
strong class="command">queries</
strong></
span>.
<
dt><
span class="term"><
span><
strong class="command">check-names</
strong></
span></
span></
dt>
This option is used to restrict the character set and syntax
certain domain names in master files
and/
or DNS responses
from the network. The default varies according to usage
<
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> zones the default
is <
span><
strong class="command">warn</
strong></
span>.
For answer received from the network (<
span><
strong class="command">response</
strong></
span>)
the default is <
span><
strong class="command">ignore</
strong></
span>.
The rules for legal hostnames / mail domains are derived
from RFC 952 and RFC 821 as modified by RFC 1123.
<
p><
span><
strong class="command">check-names</
strong></
span>
applies to the owner names of A, AAA and MX records.
It also applies to the domain names in the RDATA of NS, SOA
It also applies to the RDATA of PTR records where the owner
name indicated that it is a reverse lookup of a hostname
<
dt><
span class="term"><
span><
strong class="command">check-mx</
strong></
span></
span></
dt>
Check whether the MX record appears to refer to a IP address.
The default is to <
span><
strong class="command">warn</
strong></
span>. Other possible
values are <
span><
strong class="command">fail</
strong></
span> and
<
span><
strong class="command">ignore</
strong></
span>.
<
dt><
span class="term"><
span><
strong class="command">check-wildcard</
strong></
span></
span></
dt>
This option is used to check for non-terminal wildcards.
The use of non-terminal wildcards is almost always as a
to understand the wildcard matching algorithm (RFC 1034).
affects master zones. The default (<
span><
strong class="command">yes</
strong></
span>) is to check
for non-terminal wildcards and issue a warning.
<
dt><
span class="term"><
span><
strong class="command">check-integrity</
strong></
span></
span></
dt>
Perform post load zone integrity checks on master
zones. This checks that MX and SRV records refer
to address (A or AAAA) records and that glue
address records exist for delegated zones. For
MX and SRV records only in-zone hostnames are
checked (for out-of-zone hostnames use named-checkzone).
For NS records only names below top of zone are
checked (for out-of-zone names and glue consistancy
checks use named-checkzone). The default is
<
span><
strong class="command">yes</
strong></
span>.
<
dt><
span class="term"><
span><
strong class="command">check-sibling</
strong></
span></
span></
dt>
When performing integrity checks also check that
sibling glue exists. The default is <
span><
strong class="command">yes</
strong></
span>.
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2550145"></
a>Forwarding</
h4></
div></
div></
div>
The forwarding facility can be used to create a large site-wide
cache on a few servers, reducing traffic over links to external
name servers. It can also be used to allow queries by servers that
do not have direct access to the Internet, but wish to look up
names anyway. Forwarding occurs only on those queries for which
the server is not authoritative and does not have the answer in
<
div class="variablelist"><
dl>
<
dt><
span class="term"><
span><
strong class="command">forward</
strong></
span></
span></
dt>
This option is only meaningful if the
forwarders list is not empty. A value of <
code class="varname">first</
code>,
the default, causes the server to query the forwarders
if that doesn't answer the question the server will then
the answer itself. If <
code class="varname">only</
code> is
server will only query the forwarders.
<
dt><
span class="term"><
span><
strong class="command">forwarders</
strong></
span></
span></
dt>
Specifies the IP addresses to be used
for forwarding. The default is the empty list (no
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
or have a different <
span><
strong class="command">forward
only/
first</
strong></
span> behavior,
or not forward at all, see <
a href="Bv9ARM.ch06.html#zone_statement_grammar" title="zone Statement Grammar">the section called “<
span><
strong class="command">zone</
strong></
span>
Statement Grammar”</
a>.
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2550272"></
a>Dual-stack Servers</
h4></
div></
div></
div>
Dual-stack servers are used as servers of last resort to work
problems in reachability due the lack of support for either IPv4
<
div class="variablelist"><
dl>
<
dt><
span class="term"><
span><
strong class="command">dual-stack-servers</
strong></
span></
span></
dt>
Specifies host names / addresses of machines with access to
both IPv4 and IPv6 transports. If a hostname is used the
to resolve the name using only the transport it has. If the
stacked then the <
span><
strong class="command">dual-stack-servers</
strong></
span> have no effect unless
access to a transport has been disabled on the command line
(
e.g. <
span><
strong class="command">named -4</
strong></
span>).
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="access_control"></
a>Access Control</
h4></
div></
div></
div>
Access to the server can be restricted based on the IP address
of the requesting system. See <
a href="Bv9ARM.ch06.html#address_match_lists" title="Address Match Lists">the section called “Address Match Lists”</
a> for
details on how to specify IP address lists.
<
div class="variablelist"><
dl>
<
dt><
span class="term"><
span><
strong class="command">allow-notify</
strong></
span></
span></
dt>
Specifies which hosts are allowed to
notify this server, a slave, of zone changes in addition
<
span><
strong class="command">allow-notify</
strong></
span> may also be
<
span><
strong class="command">zone</
strong></
span> statement, in which case
<
span><
strong class="command">options allow-notify</
strong></
span>
statement. It is only meaningful
for a slave zone. If not specified, the default is to
only from a zone's master.
<
dt><
span class="term"><
span><
strong class="command">allow-query</
strong></
span></
span></
dt>
Specifies which hosts are allowed to
ask ordinary DNS questions. <
span><
strong class="command">allow-query</
strong></
span> may also
be specified in the <
span><
strong class="command">zone</
strong></
span>
case it overrides the <
span><
strong class="command">options allow-query</
strong></
span> statement.
<
span><
strong class="command">allow-query-cache</
strong></
span> may also be
overrides access to the cache.
If not specified, the default is to allow queries from all
<
dt><
span class="term"><
span><
strong class="command">allow-query-cache</
strong></
span></
span></
dt>
Specifies which hosts are allowed to get answers
from the cache. If not set <
span><
strong class="command">allow-query</
strong></
span> applies.
The recommended way to set query access to the cache is now
<
span><
strong class="command">allow-query-cache</
strong></
span> rather than
<
span><
strong class="command">allow-query</
strong></
span>.
Inheritance from <
span><
strong class="command">allow-query</
strong></
span>
<
div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<
h3 class="title">Note</
h3>
If <
span><
strong class="command">allow-query-cache</
strong></
span> is set
level and not set in the view it will still override a
<
span><
strong class="command">allow-query</
strong></
span> set at the view
<
dt><
span class="term"><
span><
strong class="command">allow-recursion</
strong></
span></
span></
dt>
Specifies which hosts are allowed to
make recursive queries through this server. If not
default is to allow recursive queries from all hosts.
Note that disallowing recursive queries for a host does not
host from retrieving data that is already in the server's
<
dt><
span class="term"><
span><
strong class="command">allow-update</
strong></
span></
span></
dt>
Specifies which hosts are allowed to
submit Dynamic DNS updates for master zones. The default is
updates from all hosts. Note that allowing updates based
on the requestor's IP address is insecure; see
<
a href="Bv9ARM.ch07.html#dynamic_update_security" title="Dynamic Update Security">the section called “Dynamic Update Security”</
a> for details.
<
dt><
span class="term"><
span><
strong class="command">allow-update-forwarding</
strong></
span></
span></
dt>
Specifies which hosts are allowed to
submit Dynamic DNS updates to slave zones to be forwarded to
master. The default is <
strong class="userinput"><
code>{ none; }</
code></
strong>,
means that no update forwarding will be performed. To
update forwarding, specify
<
strong class="userinput"><
code>allow-update-forwarding { any; };</
code></
strong>.
Specifying values other than <
strong class="userinput"><
code>{ none; }</
code></
strong> or
<
strong class="userinput"><
code>{ any; }</
code></
strong> is usually
the responsibility for update access control should rest
master server, not the slaves.
Note that enabling the update forwarding feature on a slave
may expose master servers relying on insecure IP address
access control to attacks; see <
a href="Bv9ARM.ch07.html#dynamic_update_security" title="Dynamic Update Security">the section called “Dynamic Update Security”</
a>
<
dt><
span class="term"><
span><
strong class="command">allow-v6-synthesis</
strong></
span></
span></
dt>
This option was introduced for the smooth transition from
to A6 and from "nibble labels" to binary labels.
However, since both A6 and binary labels were then
this option was also deprecated.
It is now ignored with some warning messages.
<
dt><
span class="term"><
span><
strong class="command">allow-transfer</
strong></
span></
span></
dt>
Specifies which hosts are allowed to
receive zone transfers from the server. <
span><
strong class="command">allow-transfer</
strong></
span> may
also be specified in the <
span><
strong class="command">zone</
strong></
span>
case it overrides the <
span><
strong class="command">options allow-transfer</
strong></
span> statement.
If not specified, the default is to allow transfers to all
<
dt><
span class="term"><
span><
strong class="command">blackhole</
strong></
span></
span></
dt>
Specifies a list of addresses that the
server will not accept queries from or use to resolve a
from these addresses will not be responded to. The default
is <
strong class="userinput"><
code>none</
code></
strong>.
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2550681"></
a>Interfaces</
h4></
div></
div></
div>
The interfaces and ports that the server will answer queries
from may be specified using the <
span><
strong class="command">listen-on</
strong></
span> option. <
span><
strong class="command">listen-on</
strong></
span> takes
an optional port, and an <
code class="varname">address_match_list</
code>.
The server will listen on all interfaces allowed by the address
match list. If a port is not specified, port 53 will be used.
Multiple <
span><
strong class="command">listen-on</
strong></
span> statements are
<
pre class="programlisting">listen-on { 5.6.7.8; };
listen-on port 1234 { !1.2.3.4;
1.2/
16; };
will enable the name server on port 53 for the IP address
5.6.7.8, and on port 1234 of an address on the machine in net
If no <
span><
strong class="command">listen-on</
strong></
span> is specified, the
server will listen on port 53 on all interfaces.
The <
span><
strong class="command">listen-on-v6</
strong></
span> option is used to
specify the interfaces and the ports on which the server will
for incoming queries sent using IPv6.
<
pre class="programlisting">{ any; }</
pre>
as the <
code class="varname">address_match_list</
code> for the
<
span><
strong class="command">listen-on-v6</
strong></
span> option,
the server does not bind a separate socket to each IPv6 interface
address as it does for IPv4 if the operating system has enough API
support for IPv6 (specifically if it conforms to RFC 3493 and RFC
Instead, it listens on the IPv6 wildcard address.
If the system only has incomplete API support for IPv6, however,
the behavior is the same as that for IPv4.
A list of particular IPv6 addresses can also be specified, in
the server listens on a separate socket for each specified
regardless of whether the desired API is supported by the system.
Multiple <
span><
strong class="command">listen-on-v6</
strong></
span> options can
<
pre class="programlisting">listen-on-v6 { any; };
listen-on-v6 port 1234 { !2001:db8::/32; any; };
will enable the name server on port 53 for any IPv6 addresses
(with a single wildcard socket),
and on port 1234 of IPv6 addresses that is not in the prefix
2001:db8::/32 (with separate sockets for each matched address.)
To make the server not listen on any IPv6 address, use
<
pre class="programlisting">listen-on-v6 { none; };
If no <
span><
strong class="command">listen-on-v6</
strong></
span> option is
the server will not listen on any IPv6 address.
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2550770"></
a>Query Address</
h4></
div></
div></
div>
If the server doesn't know the answer to a question, it will
query other name servers. <
span><
strong class="command">query-source</
strong></
span> specifies
the address and port used for such queries. For queries sent over
IPv6, there is a separate <
span><
strong class="command">query-source-v6</
strong></
span> option.
If <
span><
strong class="command">address</
strong></
span> is <
span><
strong class="command">*</
strong></
span> or is omitted,
a wildcard IP address (<
span><
strong class="command">INADDR_ANY</
strong></
span>)
If <
span><
strong class="command">port</
strong></
span> is <
span><
strong class="command">*</
strong></
span> or is omitted,
a random unprivileged port will be used, <
span><
strong class="command">avoid-v4-udp-ports</
strong></
span>
and <
span><
strong class="command">avoid-v6-udp-ports</
strong></
span> can be used
from selecting certain ports. The defaults are
<
pre class="programlisting">query-source address * port *;
query-source-v6 address * port *;
<
div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<
h3 class="title">Note</
h3>
The address specified in the <
span><
strong class="command">query-source</
strong></
span> option
is used for both UDP and TCP queries, but the port applies only
UDP queries. TCP queries always use a random
<
div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<
h3 class="title">Note</
h3>
See also <
span><
strong class="command">transfer-source</
strong></
span> and
<
span><
strong class="command">notify-source</
strong></
span>.
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="zone_transfers"></
a>Zone Transfers</
h4></
div></
div></
div>
<
span class="acronym">BIND</
span> 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.
<
div class="variablelist"><
dl>
<
dt><
span class="term"><
span><
strong class="command">also-notify</
strong></
span></
span></
dt>
Defines a global list of IP addresses of name servers
that are also sent NOTIFY messages whenever a fresh copy of
zone is loaded, in addition to the servers listed in the
This helps to ensure that copies of the zones will
quickly converge on stealth servers. If an <
span><
strong class="command">also-notify</
strong></
span> list
is given in a <
span><
strong class="command">zone</
strong></
span> statement,
the <
span><
strong class="command">options also-notify</
strong></
span>
statement. When a <
span><
strong class="command">zone notify</
strong></
span>
is set to <
span><
strong class="command">no</
strong></
span>, the IP
addresses in the global <
span><
strong class="command">also-notify</
strong></
span> list will
not be sent NOTIFY messages for that zone. The default is
list (no global notification list).
<
dt><
span class="term"><
span><
strong class="command">max-transfer-time-in</
strong></
span></
span></
dt>
Inbound zone transfers running longer than
this many minutes will be terminated. The default is 120
(2 hours). The maximum value is 28 days (40320 minutes).
<
dt><
span class="term"><
span><
strong class="command">max-transfer-idle-in</
strong></
span></
span></
dt>
Inbound zone transfers making no progress
in this many minutes will be terminated. The default is 60
(1 hour). The maximum value is 28 days (40320 minutes).
<
dt><
span class="term"><
span><
strong class="command">max-transfer-time-out</
strong></
span></
span></
dt>
Outbound zone transfers running longer than
this many minutes will be terminated. The default is 120
(2 hours). The maximum value is 28 days (40320 minutes).
<
dt><
span class="term"><
span><
strong class="command">max-transfer-idle-out</
strong></
span></
span></
dt>
Outbound zone transfers making no progress
in this many minutes will be terminated. The default is 60
hour). The maximum value is 28 days (40320 minutes).
<
dt><
span class="term"><
span><
strong class="command">serial-query-rate</
strong></
span></
span></
dt>
Slave servers will periodically query master servers
to find out if zone serial numbers have changed. Each such
a minute amount of the slave server's network bandwidth. To
amount of bandwidth used, BIND 9 limits the rate at which
sent. The value of the <
span><
strong class="command">serial-query-rate</
strong></
span> option,
an integer, is the maximum number of queries sent per
<
dt><
span class="term"><
span><
strong class="command">serial-queries</
strong></
span></
span></
dt>
In BIND 8, the <
span><
strong class="command">serial-queries</
strong></
span>
set the maximum number of concurrent serial number queries
allowed to be outstanding at any given time.
BIND 9 does not limit the number of outstanding
serial queries and ignores the <
span><
strong class="command">serial-queries</
strong></
span> option.
Instead, it limits the rate at which the queries are sent
as defined using the <
span><
strong class="command">serial-query-rate</
strong></
span> option.
<
dt><
span class="term"><
span><
strong class="command">transfer-format</
strong></
span></
span></
dt>
Zone transfers can be sent using two different formats,
<
span><
strong class="command">one-answer</
strong></
span> and
<
span><
strong class="command">many-answers</
strong></
span>.
The <
span><
strong class="command">transfer-format</
strong></
span> option is used
on the master server to determine which format it sends.
<
span><
strong class="command">one-answer</
strong></
span> uses one DNS message per
resource record transferred.
<
span><
strong class="command">many-answers</
strong></
span> packs as many resource
records as possible into a message.
<
span><
strong class="command">many-answers</
strong></
span> is more efficient, but is
only supported by relatively new slave servers,
such as <
span class="acronym">BIND</
span> 9, <
span class="acronym">BIND</
span>
8.x and <
span class="acronym">BIND</
span> 4.9.5 onwards.
The <
span><
strong class="command">many-answers</
strong></
span> format also supported by
recent Microsoft Windows nameservers.
The default is <
span><
strong class="command">many-answers</
strong></
span>.
<
span><
strong class="command">transfer-format</
strong></
span> may be overridden on a
per-server basis by using the <
span><
strong class="command">server</
strong></
span>
<
dt><
span class="term"><
span><
strong class="command">transfers-in</
strong></
span></
span></
dt>
The maximum number of inbound zone transfers
that can be running concurrently. The default value is <
code class="literal">10</
code>.
Increasing <
span><
strong class="command">transfers-in</
strong></
span> may
of slave zones, but it also may increase the load on the
<
dt><
span class="term"><
span><
strong class="command">transfers-out</
strong></
span></
span></
dt>
The maximum number of outbound zone transfers
that can be running concurrently. Zone transfer requests in
of the limit will be refused. The default value is <
code class="literal">10</
code>.
<
dt><
span class="term"><
span><
strong class="command">transfers-per-ns</
strong></
span></
span></
dt>
The maximum number of inbound zone transfers
that can be concurrently transferring from a given remote
The default value is <
code class="literal">2</
code>.
Increasing <
span><
strong class="command">transfers-per-ns</
strong></
span>
speed up the convergence of slave zones, but it also may
the load on the remote name server. <
span><
strong class="command">transfers-per-ns</
strong></
span> may
be overridden on a per-server basis by using the <
span><
strong class="command">transfers</
strong></
span> phrase
of the <
span><
strong class="command">server</
strong></
span> statement.
<
dt><
span class="term"><
span><
strong class="command">transfer-source</
strong></
span></
span></
dt>
<
dd><
p><
span><
strong class="command">transfer-source</
strong></
span>
determines which local address will be bound to IPv4
TCP connections used to fetch zones transferred
inbound by the server. It also determines the
source IPv4 address, and optionally the UDP port,
used for the refresh queries and forwarded dynamic
updates. 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
<
span><
strong class="command">allow-transfer</
strong></
span> option for the
zone being transferred, if one is specified. This
<
span><
strong class="command">transfer-source</
strong></
span> for all zones,
but can be overridden on a per-view or per-zone
<
span><
strong class="command">transfer-source</
strong></
span> statement within
the <
span><
strong class="command">view</
strong></
span> or
<
span><
strong class="command">zone</
strong></
span> block in the configuration
<
dt><
span class="term"><
span><
strong class="command">transfer-source-v6</
strong></
span></
span></
dt>
The same as <
span><
strong class="command">transfer-source</
strong></
span>,
except zone transfers are performed using IPv6.
<
dt><
span class="term"><
span><
strong class="command">alt-transfer-source</
strong></
span></
span></
dt>
An alternate transfer source if the one listed in
<
span><
strong class="command">transfer-source</
strong></
span> fails and
<
span><
strong class="command">use-alt-transfer-source</
strong></
span> is
<
div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<
h3 class="title">Note</
h3>
If you do not wish the alternate transfer source
to be used you should set
<
span><
strong class="command">use-alt-transfer-source</
strong></
span>
appropriately and you should not depend upon
getting a answer back to the first refresh
<
dt><
span class="term"><
span><
strong class="command">alt-transfer-source-v6</
strong></
span></
span></
dt>
An alternate transfer source if the one listed in
<
span><
strong class="command">transfer-source-v6</
strong></
span> fails and
<
span><
strong class="command">use-alt-transfer-source</
strong></
span> is
<
dt><
span class="term"><
span><
strong class="command">use-alt-transfer-source</
strong></
span></
span></
dt>
Use the alternate transfer sources or not. If views are
specified this defaults to <
span><
strong class="command">no</
strong></
span>
<
span><
strong class="command">yes</
strong></
span> (for BIND 8
<
dt><
span class="term"><
span><
strong class="command">notify-source</
strong></
span></
span></
dt>
<
dd><
p><
span><
strong class="command">notify-source</
strong></
span>
determines which local source address, and
optionally UDP port, will be used to send NOTIFY
messages. This address must appear in the slave
server's <
span><
strong class="command">masters</
strong></
span> zone clause or
in an <
span><
strong class="command">allow-notify</
strong></
span> clause. This
statement sets the <
span><
strong class="command">notify-source</
strong></
span>
for all zones, but can be overridden on a per-zone /
per-view basis by including a
<
span><
strong class="command">notify-source</
strong></
span> statement within
the <
span><
strong class="command">zone</
strong></
span> or
<
span><
strong class="command">view</
strong></
span> block in the configuration
<
dt><
span class="term"><
span><
strong class="command">notify-source-v6</
strong></
span></
span></
dt>
Like <
span><
strong class="command">notify-source</
strong></
span>,
but applies to notify messages sent to IPv6 addresses.
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2551634"></
a>Bad UDP Port Lists</
h4></
div></
div></
div>
<
p><
span><
strong class="command">avoid-v4-udp-ports</
strong></
span>
and <
span><
strong class="command">avoid-v6-udp-ports</
strong></
span> specify a list
of IPv4 and IPv6 UDP ports that will not be used as system
assigned source ports for UDP sockets. These lists
prevent named from choosing as its random source port a
port that is blocked by your firewall. If a query went
out with such a source port, the answer would not get by
the firewall and the name server would have to query
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2551649"></
a>Operating System Resource Limits</
h4></
div></
div></
div>
The server's usage of many system resources can be limited.
Scaled values are allowed when specifying resource limits. For
example, <
span><
strong class="command">1G</
strong></
span> can be used instead of
<
span><
strong class="command">1073741824</
strong></
span> to specify a limit of
gigabyte. <
span><
strong class="command">unlimited</
strong></
span> requests
maximum available amount. <
span><
strong class="command">default</
strong></
span>
that was in force when the server was started. See the description
<
span><
strong class="command">size_spec</
strong></
span> in <
a href="Bv9ARM.ch06.html#configuration_file_elements" title="Configuration File Elements">the section called “Configuration File Elements”</
a>.
The following options set operating system resource limits for
the name server process. Some operating systems don't support
any of the limits. On such systems, a warning will be issued if
unsupported limit is used.
<
div class="variablelist"><
dl>
<
dt><
span class="term"><
span><
strong class="command">coresize</
strong></
span></
span></
dt>
The maximum size of a core dump. The default
is <
code class="literal">default</
code>.
<
dt><
span class="term"><
span><
strong class="command">datasize</
strong></
span></
span></
dt>
The maximum amount of data memory the server
may use. The default is <
code class="literal">default</
code>.
This is a hard limit on server memory usage.
If the server attempts to allocate memory in excess of this
limit, the allocation will fail, which may in turn leave
the server unable to perform DNS service. Therefore,
this option is rarely useful as a way of limiting the
amount of memory used by the server, but it can be used
to raise an operating system data size limit that is
too small by default. If you wish to limit the amount
of memory used by the server, use the
<
span><
strong class="command">max-cache-size</
strong></
span> and
<
span><
strong class="command">recursive-clients</
strong></
span>
<
dt><
span class="term"><
span><
strong class="command">files</
strong></
span></
span></
dt>
The maximum number of files the server
may have open concurrently. The default is <
code class="literal">unlimited</
code>.
<
dt><
span class="term"><
span><
strong class="command">stacksize</
strong></
span></
span></
dt>
The maximum amount of stack memory the server
may use. The default is <
code class="literal">default</
code>.
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2551764"></
a>Server Resource Limits</
h4></
div></
div></
div>
The following options set limits on the server's
resource consumption that are enforced internally by the
server rather than the operating system.
<
div class="variablelist"><
dl>
<
dt><
span class="term"><
span><
strong class="command">max-ixfr-log-size</
strong></
span></
span></
dt>
This option is obsolete; it is accepted
and ignored for BIND 8 compatibility. The option
<
span><
strong class="command">max-journal-size</
strong></
span> performs a
similar function in BIND 9.
<
dt><
span class="term"><
span><
strong class="command">max-journal-size</
strong></
span></
span></
dt>
Sets a maximum size for each journal file
(<
a href="Bv9ARM.ch04.html#journal" title="The journal file">the section called “The journal file”</
a>). When the journal file
the specified size, some of the oldest transactions in the
will be automatically removed. The default is
<
code class="literal">unlimited</
code>.
<
dt><
span class="term"><
span><
strong class="command">host-statistics-max</
strong></
span></
span></
dt>
In BIND 8, specifies the maximum number of host statistic
Not implemented in BIND 9.
<
dt><
span class="term"><
span><
strong class="command">recursive-clients</
strong></
span></
span></
dt>
The maximum number of simultaneous recursive lookups
the server will perform on behalf of clients. The default
<
code class="literal">1000</
code>. Because each recursing
bit of memory, on the order of 20 kilobytes, the value of
<
span><
strong class="command">recursive-clients</
strong></
span> option may
on hosts with limited memory.
<
dt><
span class="term"><
span><
strong class="command">tcp-clients</
strong></
span></
span></
dt>
The maximum number of simultaneous client TCP
connections that the server will accept.
The default is <
code class="literal">100</
code>.
<
dt><
span class="term"><
span><
strong class="command">max-cache-size</
strong></
span></
span></
dt>
The maximum amount of memory to use for the
server's cache, in bytes. When the amount of data in the
reaches this limit, the server will cause records to expire
prematurely so that the limit is not exceeded. In a server
multiple views, the limit applies separately to the cache of
view. The default is <
code class="literal">unlimited</
code>, meaning that
records are purged from the cache only when their TTLs
<
dt><
span class="term"><
span><
strong class="command">tcp-listen-queue</
strong></
span></
span></
dt>
The listen queue depth. The default and minimum is 3.
If the kernel supports the accept filter "dataready" this
many TCP connections that will be queued in kernel space
some data before being passed to accept. Values less than 3
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2551897"></
a>Periodic Task Intervals</
h4></
div></
div></
div>
<
div class="variablelist"><
dl>
<
dt><
span class="term"><
span><
strong class="command">cleaning-interval</
strong></
span></
span></
dt>
The server will remove expired resource records
from the cache every <
span><
strong class="command">cleaning-interval</
strong></
span> minutes.
The default is 60 minutes. The maximum value is 28 days
If set to 0, no periodic cleaning will occur.
<
dt><
span class="term"><
span><
strong class="command">heartbeat-interval</
strong></
span></
span></
dt>
The server will perform zone maintenance tasks
for all zones marked as <
span><
strong class="command">dialup</
strong></
span> whenever this
interval expires. The default is 60 minutes. Reasonable
to 1 day (1440 minutes). The maximum value is 28 days
If set to 0, no zone maintenance for these zones will occur.
<
dt><
span class="term"><
span><
strong class="command">interface-interval</
strong></
span></
span></
dt>
The server will scan the network interface list
every <
span><
strong class="command">interface-interval</
strong></
span>
is 60 minutes. The maximum value is 28 days (40320 minutes).
If set to 0, interface scanning will only occur when
the configuration file is loaded. After the scan, the
begin listening for queries on any newly discovered
interfaces (provided they are allowed by the
<
span><
strong class="command">listen-on</
strong></
span> configuration), and
stop listening on interfaces that have gone away.
<
dt><
span class="term"><
span><
strong class="command">statistics-interval</
strong></
span></
span></
dt>
Name server statistics will be logged
every <
span><
strong class="command">statistics-interval</
strong></
span>
60. The maximum value is 28 days (40320 minutes).
If set to 0, no statistics will be logged.
<
div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<
h3 class="title">Note</
h3>
<
span class="acronym">BIND</
span>9.
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="topology"></
a>Topology</
h4></
div></
div></
div>
All other things being equal, when the server chooses a name
to query from a list of name servers, it prefers the one that is
topologically closest to itself. The <
span><
strong class="command">topology</
strong></
span> statement
takes an <
span><
strong class="command">address_match_list</
strong></
span> and
in a special way. Each top-level list element is assigned a
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.
<
pre class="programlisting">topology {
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.
<
pre class="programlisting"> topology { localhost; localnets; };
<
div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<
h3 class="title">Note</
h3>
The <
span><
strong class="command">topology</
strong></
span> option
is not implemented in <
span class="acronym">BIND</
span> 9.
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="the_sortlist_statement"></
a>The <
span><
strong class="command">sortlist</
strong></
span> Statement</
h4></
div></
div></
div>
The response to a DNS query may consist of multiple resource
records (RRs) forming a resource records set (RRset).
The name server will normally return the
RRs within the RRset in an indeterminate order
(but see the <
span><
strong class="command">rrset-order</
strong></
span>
statement in <
a href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">the section called “RRset Ordering”</
a>).
The client resolver code should rearrange the RRs as appropriate,
that is, using any addresses on the local net in preference to
However, not all resolvers can do this or are correctly
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 name servers, not all the clients.
The <
span><
strong class="command">sortlist</
strong></
span> statement (see below)
an <
span><
strong class="command">address_match_list</
strong></
span> and
more specifically than the <
span><
strong class="command">topology</
strong></
span>
does (<
a href="Bv9ARM.ch06.html#topology" title="Topology">the section called “Topology”</
a>).
Each top level statement in the <
span><
strong class="command">sortlist</
strong></
span> must
itself be an explicit <
span><
strong class="command">address_match_list</
strong></
span> with
one or two elements. The first element (which may be an IP
an IP prefix, an ACL name or a nested <
span><
strong class="command">address_match_list</
strong></
span>)
of each top level list is checked against the source address of
the query until a match is found.
Once the source address of the query has been matched, if
the top level statement contains only one element, the actual
element that matched the source address is used to select the
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 <
span><
strong class="command">address_match_list</
strong></
span> in
a <
span><
strong class="command">topology</
strong></
span> statement. Each top
is assigned a distance and the address in the response with the
distance is moved to the beginning of the response.
In the following example, any queries received from any of
the addresses of the host itself will get responses preferring
on any of the locally connected networks. Next most preferred are
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/
24 192.168.3/
24 networks. Queries received from a host on the
or the
192.168.5/
24 network will only prefer other addresses on
their directly connected networks.
<
pre class="programlisting">sortlist {
{ localhost; // IF the local host
{ localnets; // THEN first fit on the
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 <
span class="acronym">BIND</
span>
4.9.x. Responses sent
to queries from the local host will favor any of the directly
networks. Responses sent to queries from any other hosts on a
connected network will prefer addresses on that same network.
to other queries will not be sorted.
<
pre class="programlisting">sortlist {
{ localhost; localnets; };
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="rrset_ordering"></
a>RRset Ordering</
h4></
div></
div></
div>
When multiple records are returned in an answer it may be
useful to configure the order of the records placed into the
The <
span><
strong class="command">rrset-order</
strong></
span> statement permits
of the ordering of the records in a multiple record response.
See also the <
span><
strong class="command">sortlist</
strong></
span> statement,
<
a href="Bv9ARM.ch06.html#the_sortlist_statement" title="The sortlist Statement">the section called “The <
span><
strong class="command">sortlist</
strong></
span> Statement”</
a>.
An <
span><
strong class="command">order_spec</
strong></
span> is defined as
[<
span class="optional">class <
em class="replaceable"><
code>class_name</
code></
em></
span>]
[<
span class="optional">type <
em class="replaceable"><
code>type_name</
code></
em></
span>]
[<
span class="optional">name <
em class="replaceable"><
code>"domain_name"</
code></
em></
span>]
order <
em class="replaceable"><
code>ordering</
code></
em>
If no class is specified, the default is <
span><
strong class="command">ANY</
strong></
span>.
If no type is specified, the default is <
span><
strong class="command">ANY</
strong></
span>.
If no name is specified, the default is "<
span><
strong class="command">*</
strong></
span>".
The legal values for <
span><
strong class="command">ordering</
strong></
span> are:
<
div class="informaltable"><
table border="1">
<
p><
span><
strong class="command">fixed</
strong></
span></
p>
Records are returned in the order they
are defined in the zone file.
<
p><
span><
strong class="command">random</
strong></
span></
p>
Records are returned in some random order.
<
p><
span><
strong class="command">cyclic</
strong></
span></
p>
Records are returned in a round-robin
<
pre class="programlisting">rrset-order {
will cause any responses for type A records in class IN that
suffix, to always be returned
in random order. All other records are returned in cyclic order.
If multiple <
span><
strong class="command">rrset-order</
strong></
span> statements
they are not combined — the last one applies.
<
div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<
h3 class="title">Note</
h3>
The <
span><
strong class="command">rrset-order</
strong></
span> statement
is not yet fully implemented in <
span class="acronym">BIND</
span> 9.
BIND 9 currently does not fully support "fixed" ordering.
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="tuning"></
a>Tuning</
h4></
div></
div></
div>
<
div class="variablelist"><
dl>
<
dt><
span class="term"><
span><
strong class="command">lame-ttl</
strong></
span></
span></
dt>
Sets the number of seconds to cache a
lame server indication. 0 disables caching. (This is
<
span class="bold"><
strong>NOT</
strong></
span> recommended.)
Default is <
code class="literal">600</
code> (10 minutes).
<
code class="literal">1800</
code> (30 minutes).
<
dt><
span class="term"><
span><
strong class="command">max-ncache-ttl</
strong></
span></
span></
dt>
To reduce network traffic and increase performance
the server stores negative answers. <
span><
strong class="command">max-ncache-ttl</
strong></
span> is
used to set a maximum retention time for these answers in
<
span><
strong class="command">max-ncache-ttl</
strong></
span> is <
code class="literal">10800</
code> seconds (3 hours).
<
span><
strong class="command">max-ncache-ttl</
strong></
span> cannot exceed
be silently truncated to 7 days if set to a greater value.
<
dt><
span class="term"><
span><
strong class="command">max-cache-ttl</
strong></
span></
span></
dt>
<
dd><
p><
span><
strong class="command">max-cache-ttl</
strong></
span>
sets the maximum time for which the server will
cache ordinary (positive) answers. The default is
<
dt><
span class="term"><
span><
strong class="command">min-roots</
strong></
span></
span></
dt>
The minimum number of root servers that
is required for a request for the root servers to be
is <
strong class="userinput"><
code>2</
code></
strong>.
<
div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<
h3 class="title">Note</
h3>
Not implemented in <
span class="acronym">BIND</
span>9.
<
dt><
span class="term"><
span><
strong class="command">sig-validity-interval</
strong></
span></
span></
dt>
Specifies the number of days into the
future when DNSSEC signatures automatically generated as a
of dynamic updates (<
a href="Bv9ARM.ch04.html#dynamic_update" title="Dynamic Update">the section called “Dynamic Update”</
a>)
will expire. The default is <
code class="literal">30</
code> days.
The maximum value is 10 years (3660 days). The signature
inception time is unconditionally set to one hour before the
to allow for a limited amount of clock skew.
<
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>
These options control the server's behavior on refreshing a
(querying for SOA changes) or retrying failed transfers.
Usually the SOA values for the zone are used, but these
are set by the master, giving slave server administrators
control over their contents.
These options allow the administrator to set a minimum and
refresh and retry time either per-zone, per-view, or
These options are valid for slave and stub zones,
and clamp the SOA refresh and retry times to the specified
<
dt><
span class="term"><
span><
strong class="command">edns-udp-size</
strong></
span></
span></
dt>
Sets the advertised EDNS UDP buffer size. Valid
values are 512 to 4096 (values outside this range
will be silently adjusted). The default value is
4096. The usual reason for setting edns-udp-size to
a non default value it to get UDP answers to pass
through broken firewalls that block fragmented
packets
and/
or block UDP packets that are greater
<
dt><
span class="term"><
span><
strong class="command">masterfile-format</
strong></
span></
span></
dt>
<
dd><
p><
span><
strong class="command">masterfile-format</
strong></
span> specifies
the file format of zone files (see
<
a href="Bv9ARM.ch06.html#zonefile_format" title="Additional File Formats">the section called “Additional File Formats”</
a>).
The default value is <
code class="constant">text</
code>, which is the
standard textual representation. Files in other formats
than <
code class="constant">text</
code> are typically expected
to be generated by the <
span><
strong class="command">named-compilezone</
strong></
span>.
Note that when a zone file in a different format than
<
code class="constant">text</
code> is loaded, <
span><
strong class="command">named</
strong></
span>
may omit some of the checks which would be performed for a
file in the <
code class="constant">text</
code> format. In particular,
<
span><
strong class="command">check-names</
strong></
span> checks do not apply
for the <
code class="constant">raw</
code> format. This means
a zone file in the <
code class="constant">raw</
code> format
must be generated with the same check level as that
specified in the <
span><
strong class="command">named</
strong></
span> configuration
file. This statement sets the
<
span><
strong class="command">masterfile-format</
strong></
span> for all zones,
but can be overridden on a per-zone / per-view basis
by including a <
span><
strong class="command">masterfile-format</
strong></
span>
statement within the <
span><
strong class="command">zone</
strong></
span> or
<
span><
strong class="command">view</
strong></
span> block in the configuration
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="builtin"></
a>Built-in server information zones</
h4></
div></
div></
div>
The server provides some helpful diagnostic information
through a number of built-in zones under the
pseudo-top-level-domain <
code class="literal">bind</
code> in the
<
span><
strong class="command">CHAOS</
strong></
span> class. These zones are part
built-in view (see <
a href="Bv9ARM.ch06.html#view_statement_grammar" title="view Statement Grammar">the section called “<
span><
strong class="command">view</
strong></
span> Statement Grammar”</
a>) of
<
span><
strong class="command">CHAOS</
strong></
span> which is separate from the
class <
span><
strong class="command">IN</
strong></
span>; therefore, any global
such as <
span><
strong class="command">allow-query</
strong></
span> do not apply
If you feel the need to disable these zones, use the options
below, or hide the built-in <
span><
strong class="command">CHAOS</
strong></
span>
defining an explicit view of class <
span><
strong class="command">CHAOS</
strong></
span>
that matches all clients.
<
div class="variablelist"><
dl>
<
dt><
span class="term"><
span><
strong class="command">version</
strong></
span></
span></
dt>
The version the server should report
via a query of the name <
code class="literal">
version.bind</
code>
with type <
span><
strong class="command">TXT</
strong></
span>, class <
span><
strong class="command">CHAOS</
strong></
span>.
The default is the real version number of this server.
Specifying <
span><
strong class="command">version none</
strong></
span>
disables processing of the queries.
<
dt><
span class="term"><
span><
strong class="command">hostname</
strong></
span></
span></
dt>
The hostname the server should report via a query of
with type <
span><
strong class="command">TXT</
strong></
span>, class <
span><
strong class="command">CHAOS</
strong></
span>.
This defaults to the hostname of the machine hosting the
found by gethostname(). The primary purpose of such queries
identify which of a group of anycast servers is actually
answering your queries. Specifying <
span><
strong class="command">hostname none;</
strong></
span>
disables processing of the queries.
<
dt><
span class="term"><
span><
strong class="command">server-id</
strong></
span></
span></
dt>
The ID of the server should report via a query of
the name <
code class="filename">
ID.SERVER</
code>
with type <
span><
strong class="command">TXT</
strong></
span>, class <
span><
strong class="command">CHAOS</
strong></
span>.
The primary purpose of such queries is to
identify which of a group of anycast servers is actually
answering your queries. Specifying <
span><
strong class="command">server-id none;</
strong></
span>
disables processing of the queries.
Specifying <
span><
strong class="command">server-id hostname;</
strong></
span> will cause named to
use the hostname as found by gethostname().
The default <
span><
strong class="command">server-id</
strong></
span> is <
span><
strong class="command">none</
strong></
span>.
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="empty"></
a>Built-in Empty Zones</
h4></
div></
div></
div>
Named has some built-in empty zones (SOA and NS records only).
These are for zones that should normally be answered locally
and which queries should not be sent to the Internet's root
servers. The offical servers which cover these namespaces
return NXDOMAIN responses to these queries. In particular
these cover the reverse namespace for addresses from RFC 1918 and
RFC 3330. They also include the reverse namespace for IPv6 local
address (locally assigned), IPv6 link local addresses, the IPv6
loopback address and the IPv6 unknown addresss.
Named will attempt to determine if a built in zone already exists
or is active (covered by a forward-only forwarding declaration)
and will not not create a empty zone in that case.
The current list of empty zones is:
<
div class="itemizedlist"><
ul type="disc">
Empty zones are settable at the view level and only apply to
views of class IN. Disabled empty zones are only inherited
from options if there are no disabled empty zones specified
at the view level. To override the options list of disabled
zones you can disable the root zone at the view level
(disable-empty-zone ".";).
If you are using the address ranges covered here you should
already have reverse zones covering the addresses you use.
In practice this appears to not be the case with many queries
being made to the infrustucture servers for names in these
spaces. So many in fact that sacrificial servers were needed
to be deployed to channel the query load away from the
<
div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<
h3 class="title">Note</
h3>
The real parent servers for these zones should disable all
empty zone under the parent zone they serve. For the real
root servers this is all built in empty zones. This will
enable them to return referrals to deeper in the tree.
<
div class="variablelist"><
dl>
<
dt><
span class="term"><
span><
strong class="command">empty-server</
strong></
span></
span></
dt>
Specify what server name will appear in the returned
SOA record for empty zones. If none is specified then
the zone's name will be used.
<
dt><
span class="term"><
span><
strong class="command">empty-contact</
strong></
span></
span></
dt>
Specify what contact name will appear in the returned
SOA record for empty zones. If none is specified then
<
dt><
span class="term"><
span><
strong class="command">empty-zones-enable</
strong></
span></
span></
dt>
Enable / disable all empty zones. By default they
<
dt><
span class="term"><
span><
strong class="command">disable-empty-zone</
strong></
span></
span></
dt>
Disable a indiviual empty zones. By default none are
disabled. This option can be specified multiple times.
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="statsfile"></
a>The Statistics File</
h4></
div></
div></
div>
The statistics file generated by <
span class="acronym">BIND</
span> 9
is similar, but not identical, to that
generated by <
span class="acronym">BIND</
span> 8.
The statistics dump begins with the line <
span><
strong class="command">+++ Statistics Dump
+++ (973798949)</
strong></
span>, where the number in parentheses is a standard
Unix-style timestamp, measured as seconds since January 1, 1970.
that line are a series of lines containing a counter type, the
counter, optionally a zone name, and optionally a view name.
The lines without view and zone listed are global statistics for
Lines with a zone and view name for the given view and zone (the
omitted for the default view). The statistics dump ends
with the line <
span><
strong class="command">--- Statistics Dump --- (973798949)</
strong></
span>, where the
number is identical to the number in the beginning line.
The following statistics counters are maintained:
<
div class="informaltable"><
table border="1">
<
p><
span><
strong class="command">success</
strong></
span></
p>
successful queries made to the server or zone. A
is defined as query which returns a NOERROR response
<
p><
span><
strong class="command">referral</
strong></
span></
p>
The number of queries which resulted
<
p><
span><
strong class="command">nxrrset</
strong></
span></
p>
The number of queries which resulted in
NOERROR responses with no data.
<
p><
span><
strong class="command">nxdomain</
strong></
span></
p>
of queries which resulted in NXDOMAIN responses.
<
p><
span><
strong class="command">failure</
strong></
span></
p>
The number of queries which resulted in a
failure response other than those above.
<
p><
span><
strong class="command">recursion</
strong></
span></
p>
The number of queries which caused the server
to perform recursion in order to find the final answer.
Each query received by the server will cause exactly one of
<
span><
strong class="command">success</
strong></
span>,
<
span><
strong class="command">referral</
strong></
span>,
<
span><
strong class="command">nxrrset</
strong></
span>,
<
span><
strong class="command">nxdomain</
strong></
span>, or
<
span><
strong class="command">failure</
strong></
span>
to be incremented, and may additionally cause the
<
span><
strong class="command">recursion</
strong></
span> counter to be
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="acache"></
a>Additional Section Caching</
h4></
div></
div></
div>
The additional section cache, also called <
span><
strong class="command">acache</
strong></
span>,
is an internal cache to improve the response performance of BIND 9.
When additional section caching is enabled, BIND 9 will
cache an internal short-cut to the additional section content for
Note that <
span><
strong class="command">acache</
strong></
span> is an internal caching
mechanism of BIND 9, and is not related to the DNS caching
Additional section caching does not change the
response content (except the RRsets ordering of the additional
section, see below), but can improve the response performance
It is particularly effective when BIND 9 acts as an authoritative
server for a zone that has many delegations with many glue RRs.
In order to obtain the maximum performance improvement
from additional section caching, setting
<
span><
strong class="command">additional-from-cache</
strong></
span>
to <
span><
strong class="command">no</
strong></
span> is recommended, since the current
implementation of <
span><
strong class="command">acache</
strong></
span>
does not short-cut of additional section information from the
One obvious disadvantage of <
span><
strong class="command">acache</
strong></
span> is
that it requires much more
memory for the internal cached data.
Thus, if the response performance does not matter and memory
consumption is much more critical, the
<
span><
strong class="command">acache</
strong></
span> mechanism can be
disabled by setting <
span><
strong class="command">use-additional-cache</
strong></
span> to
<
span><
strong class="command">no</
strong></
span>.
It is also possible to specify the upper limit of memory
for acache by using <
span><
strong class="command">max-acache-size</
strong></
span>.
Additional section caching also has a minor effect on the
RRset ordering in the additional section.
Without <
span><
strong class="command">acache</
strong></
span>,
<
span><
strong class="command">cyclic</
strong></
span> order is effective for the additional
section as well as the answer and authority sections.
However, additional section caching fixes the ordering when it
first caches an RRset for the additional section, and the same
ordering will be kept in succeeding responses, regardless of the
setting of <
span><
strong class="command">rrset-order</
strong></
span>.
The effect of this should be minor, however, since an
RRset in the additional section
typically only contains a small number of RRs (and in many cases
it only contains a single RR), in which case the
ordering does not matter much.
The following is a summary of options related to
<
span><
strong class="command">acache</
strong></
span>.
<
div class="variablelist"><
dl>
<
dt><
span class="term"><
span><
strong class="command">use-additional-cache</
strong></
span></
span></
dt>
If <
span><
strong class="command">yes</
strong></
span>, additional section caching is enabled.
The default value is <
span><
strong class="command">yes</
strong></
span>.
<
dt><
span class="term"><
span><
strong class="command">acache-cleaning-interval</
strong></
span></
span></
dt>
The server will remove stale cache entries, based on an LRU
algorithm, every <
span><
strong class="command">acache-cleaning-interval</
strong></
span> minutes.
The default is 60 minutes.
If set to 0, no periodic cleaning will occur.
<
dt><
span class="term"><
span><
strong class="command">max-acache-size</
strong></
span></
span></
dt>
The maximum amount of memory to use for the server's acache,
When the amount of data in the acache reaches this limit,
will clean more aggressivly so that the limit is not
In a server with multiple views, the limit applies
The default is <
code class="literal">unlimited</
code>,
entries are purged from the acache only at the
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="server_statement_grammar"></
a><
span><
strong class="command">server</
strong></
span> Statement Grammar</
h3></
div></
div></
div>
<
pre class="programlisting">server <
em class="replaceable"><
code>ip_addr[/prefixlen]</
code></
em> {
[<
span class="optional"> bogus <
em class="replaceable"><
code>yes_or_no</
code></
em> ; </
span>]
[<
span class="optional"> provide-ixfr <
em class="replaceable"><
code>yes_or_no</
code></
em> ; </
span>]
[<
span class="optional"> request-ixfr <
em class="replaceable"><
code>yes_or_no</
code></
em> ; </
span>]
[<
span class="optional"> edns <
em class="replaceable"><
code>yes_or_no</
code></
em> ; </
span>]
[<
span class="optional"> edns-udp-size <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> transfers <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> transfer-format <
em class="replaceable"><
code>( one-answer | many-answers )</
code></
em> ; ]</
span>]
[<
span class="optional"> keys <
em class="replaceable"><
code>{ string ; [<
span class="optional"> string ; [<
span class="optional">...</
span>]</
span>] }</
code></
em> ; </
span>]
[<
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>]
[<
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>]
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="server_statement_definition_and_usage"></
a><
span><
strong class="command">server</
strong></
span> Statement Definition and
Usage</
h3></
div></
div></
div>
The <
span><
strong class="command">server</
strong></
span> statement defines
to be associated with a remote name server. If a prefix length is
specified then a range of servers is covered. Only the most
server clause applies regardless of the order in
The <
span><
strong class="command">server</
strong></
span> statement can occur at
configuration file or inside a <
span><
strong class="command">view</
strong></
span>
If a <
span><
strong class="command">view</
strong></
span> statement contains
one or more <
span><
strong class="command">server</
strong></
span> statements, only
apply to the view and any top-level ones are ignored.
If a view contains no <
span><
strong class="command">server</
strong></
span>
any top-level <
span><
strong class="command">server</
strong></
span> statements are
If you discover that a remote server is giving out bad data,
marking it as bogus will prevent further queries to it. The
value of <
span><
strong class="command">bogus</
strong></
span> is <
span><
strong class="command">no</
strong></
span>.
The <
span><
strong class="command">provide-ixfr</
strong></
span> clause determines
the local server, acting as master, will respond with an
zone transfer when the given remote server, a slave, requests it.
If set to <
span><
strong class="command">yes</
strong></
span>, incremental transfer
whenever possible. If set to <
span><
strong class="command">no</
strong></
span>,
to the remote server will be non-incremental. If not set, the
of the <
span><
strong class="command">provide-ixfr</
strong></
span> option in the
global options block is used as a default.
The <
span><
strong class="command">request-ixfr</
strong></
span> clause determines
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 <
span><
strong class="command">request-ixfr</
strong></
span> option in
global options block is used as a default.
IXFR requests to servers that do not support IXFR will
fall back to AXFR. Therefore, there is no need to manually list
which servers support IXFR and which ones do not; the global
of <
span><
strong class="command">yes</
strong></
span> should always work.
The purpose of the <
span><
strong class="command">provide-ixfr</
strong></
span> and
<
span><
strong class="command">request-ixfr</
strong></
span> clauses is
to make it possible to disable the use of IXFR even when both
and slave claim to support it, for example if one of the servers
is buggy and crashes or corrupts data when IXFR is used.
The <
span><
strong class="command">edns</
strong></
span> clause determines whether
the local server will attempt to use EDNS when communicating
with the remote server. The default is <
span><
strong class="command">yes</
strong></
span>.
The <
span><
strong class="command">edns-udp-size</
strong></
span> option sets the EDNS UDP size
that is advertised by named when querying the remote server.
Valid values are 512 to 4096 (values outside this range will be
silently adjusted). This option is useful when you wish to
advertises a different value to this server than the value you
advertise globally, for example, when there is a firewall at the
remote site that is blocking large replies.
The server supports two zone transfer methods. The first, <
span><
strong class="command">one-answer</
strong></
span>,
uses one DNS message per resource record transferred. <
span><
strong class="command">many-answers</
strong></
span> packs
as many resource records as possible into a message. <
span><
strong class="command">many-answers</
strong></
span> is
more efficient, but is only known to be understood by <
span class="acronym">BIND</
span> 9, <
span class="acronym">BIND</
span>
8.x, and patched versions of <
span class="acronym">BIND</
span>
4.9.5. You can specify which method
to use for a server with the <
span><
strong class="command">transfer-format</
strong></
span> option.
If <
span><
strong class="command">transfer-format</
strong></
span> is not
specified, the <
span><
strong class="command">transfer-format</
strong></
span>
by the <
span><
strong class="command">options</
strong></
span> statement will be
<
p><
span><
strong class="command">transfers</
strong></
span>
is used to limit the number of concurrent inbound zone
transfers from the specified server. If no
<
span><
strong class="command">transfers</
strong></
span> clause is specified, the
limit is set according to the
<
span><
strong class="command">transfers-per-ns</
strong></
span> option.
The <
span><
strong class="command">keys</
strong></
span> clause identifies a
<
span><
strong class="command">key_id</
strong></
span> defined by the <
span><
strong class="command">key</
strong></
span> statement,
to be used for transaction security (TSIG, <
a href="Bv9ARM.ch04.html#tsig" title="TSIG">the section called “TSIG”</
a>)
when talking to the remote server.
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
to be signed by this key.
Although the grammar of the <
span><
strong class="command">keys</
strong></
span>
allows for multiple keys, only a single key per server is
The <
span><
strong class="command">transfer-source</
strong></
span> and
<
span><
strong class="command">transfer-source-v6</
strong></
span> clauses specify
address to be used for zone transfer with the remote server,
For an IPv4 remote server, only <
span><
strong class="command">transfer-source</
strong></
span> can
Similarly, for an IPv6 remote server, only
<
span><
strong class="command">transfer-source-v6</
strong></
span> can be
Form more details, see the description of
<
span><
strong class="command">transfer-source</
strong></
span> and
<
span><
strong class="command">transfer-source-v6</
strong></
span> in
<
a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called “Zone Transfers”</
a>.
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2554419"></
a><
span><
strong class="command">trusted-keys</
strong></
span> Statement Grammar</
h3></
div></
div></
div>
<
pre class="programlisting">trusted-keys {
<
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"> <
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>]
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2554468"></
a><
span><
strong class="command">trusted-keys</
strong></
span> Statement Definition
and Usage</
h3></
div></
div></
div>
The <
span><
strong class="command">trusted-keys</
strong></
span> statement defines
security roots. DNSSEC is described in <
a href="Bv9ARM.ch04.html#DNSSEC" title="DNSSEC">the section called “DNSSEC”</
a>. A
security root is defined when the public key for a
zone is known, but cannot be securely obtained through DNS, either
because it is the DNS root zone or because its parent zone is
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
The <
span><
strong class="command">trusted-keys</
strong></
span> statement can
multiple key entries, each consisting of the key's domain name,
flags, protocol, algorithm, and the Base-64 representation of the
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="view_statement_grammar"></
a><
span><
strong class="command">view</
strong></
span> Statement Grammar</
h3></
div></
div></
div>
<
pre class="programlisting">view <
em class="replaceable"><
code>view_name</
code></
em>
[<
span class="optional"><
em class="replaceable"><
code>class</
code></
em></
span>] {
match-clients { <
em class="replaceable"><
code>address_match_list</
code></
em> };
match-destinations { <
em class="replaceable"><
code>address_match_list</
code></
em> };
match-recursive-only <
em class="replaceable"><
code>yes_or_no</
code></
em> ;
[<
span class="optional"> <
em class="replaceable"><
code>view_option</
code></
em>; ...</
span>]
[<
span class="optional"> <
em class="replaceable"><
code>zone_statement</
code></
em>; ...</
span>]
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2554538"></
a><
span><
strong class="command">view</
strong></
span> Statement Definition and Usage</
h3></
div></
div></
div>
The <
span><
strong class="command">view</
strong></
span> statement is a powerful
of <
span class="acronym">BIND</
span> 9 that lets a name server
answer a DNS query differently
depending on who is asking. It is particularly useful for
split DNS setups without having to run multiple servers.
Each <
span><
strong class="command">view</
strong></
span> statement defines a view
DNS namespace that will be seen by a subset of clients. A client
a view if its source IP address matches the
<
code class="varname">address_match_list</
code> of the view's
<
span><
strong class="command">match-clients</
strong></
span> clause and its
destination IP address matches
the <
code class="varname">address_match_list</
code> of the
<
span><
strong class="command">match-destinations</
strong></
span> clause. If not
<
span><
strong class="command">match-clients</
strong></
span> and <
span><
strong class="command">match-destinations</
strong></
span>
default to matching all addresses. In addition to checking IP
<
span><
strong class="command">match-clients</
strong></
span> and <
span><
strong class="command">match-destinations</
strong></
span>
can also take <
span><
strong class="command">keys</
strong></
span> which provide an
client to select the view. A view can also be specified
as <
span><
strong class="command">match-recursive-only</
strong></
span>, which
means that only recursive
requests from matching clients will match that view.
The order of the <
span><
strong class="command">view</
strong></
span> statements is
a client request will be resolved in the context of the first
<
span><
strong class="command">view</
strong></
span> that it matches.
Zones defined within a <
span><
strong class="command">view</
strong></
span>
be only be accessible to clients that match the <
span><
strong class="command">view</
strong></
span>.
By defining a zone of the same name in multiple views, different
zone data can be given to different clients, for example,
and "external" clients in a split DNS setup.
Many of the options given in the <
span><
strong class="command">options</
strong></
span> statement
can also be used within a <
span><
strong class="command">view</
strong></
span>
apply only when resolving queries with that view. When no
value is given, the value in the <
span><
strong class="command">options</
strong></
span> statement
is used as a default. Also, zone options can have default values
in the <
span><
strong class="command">view</
strong></
span> statement; these
take precedence over those in the <
span><
strong class="command">options</
strong></
span> statement.
Views are class specific. If no class is given, class IN
is assumed. Note that all non-IN views must contain a hint zone,
since only the IN class has compiled-in default hints.
If there are no <
span><
strong class="command">view</
strong></
span> statements in
file, a default view that matches any client is automatically
in class IN. Any <
span><
strong class="command">zone</
strong></
span> statements
the top level of the configuration file are considered to be part
this default view, and the <
span><
strong class="command">options</
strong></
span>
apply to the default view. If any explicit <
span><
strong class="command">view</
strong></
span>
statements are present, all <
span><
strong class="command">zone</
strong></
span>
occur inside <
span><
strong class="command">view</
strong></
span> statements.
Here is an example of a typical split DNS setup implemented
using <
span><
strong class="command">view</
strong></
span> statements.
<
pre class="programlisting">view "internal" {
// This should match our internal networks.
match-clients { 10.0.0.0/8; };
// Provide recursive service to internal clients only.
// including addresses of internal hosts.
// Match all clients not matched by the previous view.
// Refuse recursive service to external clients.
// containing only publicly accessible hosts.
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="zone_statement_grammar"></
a><
span><
strong class="command">zone</
strong></
span>
Statement Grammar</
h3></
div></
div></
div>
<
pre class="programlisting">zone <
em class="replaceable"><
code>zone_name</
code></
em> [<
span class="optional"><
em class="replaceable"><
code>class</
code></
em></
span>] [<
span class="optional">{
type ( master | slave | hint | stub | forward | delegation-only ) ;
[<
span class="optional"> allow-notify { <
em class="replaceable"><
code>address_match_list</
code></
em> }; </
span>]
[<
span class="optional"> allow-query { <
em class="replaceable"><
code>address_match_list</
code></
em> }; </
span>]
[<
span class="optional"> allow-transfer { <
em class="replaceable"><
code>address_match_list</
code></
em> }; </
span>]
[<
span class="optional"> allow-update { <
em class="replaceable"><
code>address_match_list</
code></
em> }; </
span>]
[<
span class="optional"> update-policy { <
em class="replaceable"><
code>update_policy_rule</
code></
em> [<
span class="optional">...</
span>] }; </
span>]
[<
span class="optional"> allow-update-forwarding { <
em class="replaceable"><
code>address_match_list</
code></
em> }; </
span>]
[<
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>]
[<
span class="optional"> check-names (<
code class="constant">warn</
code>|<
code class="constant">fail</
code>|<
code class="constant">ignore</
code>) ; </
span>]
[<
span class="optional"> check-mx (<
code class="constant">warn</
code>|<
code class="constant">fail</
code>|<
code class="constant">ignore</
code>) ; </
span>]
[<
span class="optional"> check-wildcard <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
span class="optional"> check-integrity <
em class="replaceable"><
code>yes_or_no</
code></
em> ; </
span>]
[<
span class="optional"> dialup <
em class="replaceable"><
code>dialup_option</
code></
em> ; </
span>]
[<
span class="optional"> delegation-only <
em class="replaceable"><
code>yes_or_no</
code></
em> ; </
span>]
[<
span class="optional"> file <
em class="replaceable"><
code>string</
code></
em> ; </
span>]
[<
span class="optional"> masterfile-format (<
code class="constant">text</
code>|<
code class="constant">raw</
code>) ; </
span>]
[<
span class="optional"> journal <
em class="replaceable"><
code>string</
code></
em> ; </
span>]
[<
span class="optional"> forward (<
code class="constant">only</
code>|<
code class="constant">first</
code>) ; </
span>]
[<
span class="optional"> forwarders { <
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>]
[<
span class="optional"> ixfr-base <
em class="replaceable"><
code>string</
code></
em> ; </
span>]
[<
span class="optional"> ixfr-tmp-file <
em class="replaceable"><
code>string</
code></
em> ; </
span>]
[<
span class="optional"> maintain-ixfr-base <
em class="replaceable"><
code>yes_or_no</
code></
em> ; </
span>]
[<
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>]
[<
span class="optional"> max-ixfr-log-size <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> max-transfer-idle-in <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> max-transfer-idle-out <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> max-transfer-time-in <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> max-transfer-time-out <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
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>]
[<
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>]
[<
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>]
[<
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>]
[<
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>]
[<
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>]
[<
span class="optional"> use-alt-transfer-source <
em class="replaceable"><
code>yes_or_no</
code></
em>; </
span>]
[<
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>]
[<
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>]
[<
span class="optional"> zone-statistics <
em class="replaceable"><
code>yes_or_no</
code></
em> ; </
span>]
[<
span class="optional"> sig-validity-interval <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> database <
em class="replaceable"><
code>string</
code></
em> ; </
span>]
[<
span class="optional"> min-refresh-time <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> max-refresh-time <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> min-retry-time <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> max-retry-time <
em class="replaceable"><
code>number</
code></
em> ; </
span>]
[<
span class="optional"> multi-master <
em class="replaceable"><
code>yes_or_no</
code></
em> ; </
span>]
[<
span class="optional"> key-directory <
em class="replaceable"><
code>path_name</
code></
em>; </
span>]
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2555337"></
a><
span><
strong class="command">zone</
strong></
span> Statement Definition and Usage</
h3></
div></
div></
div>
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2555345"></
a>Zone Types</
h4></
div></
div></
div>
<
div class="informaltable"><
table border="1">
<
code class="varname">master</
code>
The server has a master copy of the data
for the zone and will be able to provide authoritative
<
code class="varname">slave</
code>
A slave zone is a replica of a master
zone. The <
span><
strong class="command">masters</
strong></
span> list
specifies one or more IP addresses
of master servers that the slave contacts to update
Masters list elements can also be names of other
By default, transfers are made from port 53 on the
be changed for all servers by specifying a port number
list of IP addresses, or on a per-server basis after
Authentication to the master can also be done with
If a file is specified, then the
replica will be written to this file whenever the zone
and reloaded from this file on a server restart. Use
recommended, since it often speeds server start-up and
a needless waste of bandwidth. Note that for large
tens or hundreds of thousands) of zones per server, it
use a two level naming scheme for zone file names. For
a slave server for the zone <
code class="literal">
example.com</
code> might place
the zone contents into a file called
<
code class="filename">
ex/
example.com</
code> where <
code class="filename">ex/</
code> is
just the first two letters of the zone name. (Most
behave very slowly if you put 100 000 files into
<
code class="varname">stub</
code>
A stub zone is similar to a slave zone,
except that it replicates only the NS records of a
of the entire zone. Stub zones are not a standard part
they are a feature specific to the <
span class="acronym">BIND</
span> implementation.
Stub zones can be used to eliminate the need for glue
in a parent zone at the expense of maintaining a stub
a set of name server addresses in <
code class="filename">
named.conf</
code>.
This usage is not recommended for new configurations,
supports it only in a limited way.
In <
span class="acronym">BIND</
span> 4/8, zone
transfers of a parent zone
included the NS records from stub children of that
that, in some cases, users could get away with
only in the master server for the parent zone. <
span class="acronym">BIND</
span>
9 never mixes together zone data from different zones
way. Therefore, if a <
span class="acronym">BIND</
span> 9 master serving a parent
zone has child stub zones configured, all the slave
parent zone also need to have the same child stub
Stub zones can also be used as a way of forcing the
of a given domain to use a particular set of
For example, the caching name servers on a private
RFC1918 addressing may be configured with stub zones
to use a set of internal name servers as the
<
code class="varname">forward</
code>
A "forward zone" is a way to configure
forwarding on a per-domain basis. A <
span><
strong class="command">zone</
strong></
span> statement
of type <
span><
strong class="command">forward</
strong></
span> can
contain a <
span><
strong class="command">forward</
strong></
span>
and/
or <
span><
strong class="command">forwarders</
strong></
span>
which will apply to queries within the domain given by
name. If no <
span><
strong class="command">forwarders</
strong></
span>
an empty list for <
span><
strong class="command">forwarders</
strong></
span> is given, then no
forwarding will be done for the domain, canceling the
any forwarders in the <
span><
strong class="command">options</
strong></
span> statement. Thus
if you want to use this type of zone to change the
global <
span><
strong class="command">forward</
strong></
span> option
to", then "forward only", or vice versa, but want to
servers as set globally) you need to re-specify the
<
code class="varname">hint</
code>
The initial set of root name servers is
specified using a "hint zone". When the server starts
the root hints to find a root name server and get the
list of root name servers. If no hint zone is
IN, the server uses a compiled-in default set of root
Classes other than IN have no built-in defaults hints.
<
code class="varname">delegation-only</
code>
This is used to enforce the delegation only
status of infrastructure zones (
e.g. COM, NET, ORG).
is received without a explicit or implicit delegation
section will be treated as NXDOMAIN. This does not
apex. This SHOULD NOT be applied to leaf zones.
<
code class="varname">delegation-only</
code> has no
effect on answers received
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2555764"></
a>Class</
h4></
div></
div></
div>
The zone's name may optionally be followed by a class. If
a class is not specified, class <
code class="literal">IN</
code> (for <
code class="varname">Internet</
code>),
is assumed. This is correct for the vast majority of cases.
The <
code class="literal">hesiod</
code> class is
named for an information service from MIT's Project Athena. It
used to share information about various systems databases, such
as users, groups, printers and so on. The keyword
<
code class="literal">HS</
code> is
Another MIT development is CHAOSnet, a LAN protocol created
in the mid-1970s. Zone data for it can be specified with the <
code class="literal">CHAOS</
code> class.
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2555865"></
a>Zone Options</
h4></
div></
div></
div>
<
div class="variablelist"><
dl>
<
dt><
span class="term"><
span><
strong class="command">journal</
strong></
span></
span></
dt>
Allow the default journal's file name to be overridden.
The default is the zone's file with "<
code class="filename">.jnl</
code>" appended.
This is applicable to <
span><
strong class="command">master</
strong></
span> and <
span><
strong class="command">slave</
strong></
span> zones.
<
dt><
span class="term"><
span><
strong class="command">allow-notify</
strong></
span></
span></
dt>
<
span><
strong class="command">allow-notify</
strong></
span> in <
a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called “Access Control”</
a>
<
dt><
span class="term"><
span><
strong class="command">allow-query</
strong></
span></
span></
dt>
<
span><
strong class="command">allow-query</
strong></
span> in <
a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called “Access Control”</
a>
<
dt><
span class="term"><
span><
strong class="command">allow-transfer</
strong></
span></
span></
dt>
See the description of <
span><
strong class="command">allow-transfer</
strong></
span>
in <
a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called “Access Control”</
a>.
<
dt><
span class="term"><
span><
strong class="command">allow-update</
strong></
span></
span></
dt>
See the description of <
span><
strong class="command">allow-update</
strong></
span>
in <
a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called “Access Control”</
a>.
<
dt><
span class="term"><
span><
strong class="command">update-policy</
strong></
span></
span></
dt>
Specifies a "Simple Secure Update" policy. See
<
a href="Bv9ARM.ch06.html#dynamic_update_policies" title="Dynamic Update Policies">the section called “Dynamic Update Policies”</
a>.
<
dt><
span class="term"><
span><
strong class="command">allow-update-forwarding</
strong></
span></
span></
dt>
See the description of <
span><
strong class="command">allow-update-forwarding</
strong></
span>
in <
a href="Bv9ARM.ch06.html#access_control" title="Access Control">the section called “Access Control”</
a>.
<
dt><
span class="term"><
span><
strong class="command">also-notify</
strong></
span></
span></
dt>
Only meaningful if <
span><
strong class="command">notify</
strong></
span>
active for this zone. The set of machines that will
<
code class="literal">DNS NOTIFY</
code> message
for this zone is made up of all the listed name servers
the primary master) for the zone plus any IP addresses
with <
span><
strong class="command">also-notify</
strong></
span>. A port
with each <
span><
strong class="command">also-notify</
strong></
span>
address to send the notify
messages to a port other than the default of 53.
<
span><
strong class="command">also-notify</
strong></
span> is not
meaningful for stub zones.
The default is the empty list.
<
dt><
span class="term"><
span><
strong class="command">check-names</
strong></
span></
span></
dt>
This option is used to restrict the character set and
certain domain names in master files
and/
or DNS responses
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>
zones the default is <
span><
strong class="command">warn</
strong></
span>.
<
dt><
span class="term"><
span><
strong class="command">check-mx</
strong></
span></
span></
dt>
<
span><
strong class="command">check-mx</
strong></
span> in <
a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called “Boolean Options”</
a>.
<
dt><
span class="term"><
span><
strong class="command">check-wildcard</
strong></
span></
span></
dt>
<
span><
strong class="command">check-wildcard</
strong></
span> in <
a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called “Boolean Options”</
a>.
<
dt><
span class="term"><
span><
strong class="command">check-integrity</
strong></
span></
span></
dt>
<
span><
strong class="command">check-integrity</
strong></
span> in <
a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called “Boolean Options”</
a>.
<
dt><
span class="term"><
span><
strong class="command">check-sibling</
strong></
span></
span></
dt>
<
span><
strong class="command">check-sibling</
strong></
span> in <
a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called “Boolean Options”</
a>.
<
dt><
span class="term"><
span><
strong class="command">database</
strong></
span></
span></
dt>
Specify the type of database to be used for storing the
zone data. The string following the <
span><
strong class="command">database</
strong></
span> keyword
is interpreted as a list of whitespace-delimited words.
identifies the database type, and any subsequent words are
as arguments to the database to be interpreted in a way
The default is <
strong class="userinput"><
code>"rbt"</
code></
strong>, BIND 9's
red-black-tree database. This database does not take
Other values are possible if additional database drivers
have been linked into the server. Some sample drivers are
with the distribution but none are linked in by default.
<
dt><
span class="term"><
span><
strong class="command">dialup</
strong></
span></
span></
dt>
<
span><
strong class="command">dialup</
strong></
span> in <
a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called “Boolean Options”</
a>.
<
dt><
span class="term"><
span><
strong class="command">delegation-only</
strong></
span></
span></
dt>
The flag only applies to hint and stub zones. If set
to <
strong class="userinput"><
code>yes</
code></
strong> then the zone will also be
is also a delegation-only type zone.
<
dt><
span class="term"><
span><
strong class="command">forward</
strong></
span></
span></
dt>
Only meaningful if the zone has a forwarders
list. The <
span><
strong class="command">only</
strong></
span> value causes
after trying the forwarders and getting no answer, while <
span><
strong class="command">first</
strong></
span> would
allow a normal lookup to be tried.
<
dt><
span class="term"><
span><
strong class="command">forwarders</
strong></
span></
span></
dt>
Used to override the list of global forwarders.
If it is not specified in a zone of type <
span><
strong class="command">forward</
strong></
span>,
no forwarding is done for the zone; the global options are
<
dt><
span class="term"><
span><
strong class="command">ixfr-base</
strong></
span></
span></
dt>
Was used in <
span class="acronym">BIND</
span> 8 to
of the transaction log (journal) file for dynamic update
<
span class="acronym">BIND</
span> 9 ignores the option
and constructs the name of the journal
file by appending "<
code class="filename">.jnl</
code>"
<
dt><
span class="term"><
span><
strong class="command">ixfr-tmp-file</
strong></
span></
span></
dt>
Was an undocumented option in <
span class="acronym">BIND</
span> 8.
Ignored in <
span class="acronym">BIND</
span> 9.
<
dt><
span class="term"><
span><
strong class="command">max-transfer-time-in</
strong></
span></
span></
dt>
<
span><
strong class="command">max-transfer-time-in</
strong></
span> in <
a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called “Zone Transfers”</
a>.
<
dt><
span class="term"><
span><
strong class="command">max-transfer-idle-in</
strong></
span></
span></
dt>
<
span><
strong class="command">max-transfer-idle-in</
strong></
span> in <
a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called “Zone Transfers”</
a>.
<
dt><
span class="term"><
span><
strong class="command">max-transfer-time-out</
strong></
span></
span></
dt>
<
span><
strong class="command">max-transfer-time-out</
strong></
span> in <
a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called “Zone Transfers”</
a>.
<
dt><
span class="term"><
span><
strong class="command">max-transfer-idle-out</
strong></
span></
span></
dt>
<
span><
strong class="command">max-transfer-idle-out</
strong></
span> in <
a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called “Zone Transfers”</
a>.
<
dt><
span class="term"><
span><
strong class="command">notify</
strong></
span></
span></
dt>
<
span><
strong class="command">notify</
strong></
span> in <
a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called “Boolean Options”</
a>.
<
dt><
span class="term"><
span><
strong class="command">pubkey</
strong></
span></
span></
dt>
In <
span class="acronym">BIND</
span> 8, this option was
a public zone key for verification of signatures in DNSSEC
zones when they are loaded from disk. <
span class="acronym">BIND</
span> 9 does not verify signatures
on load and ignores the option.
<
dt><
span class="term"><
span><
strong class="command">zone-statistics</
strong></
span></
span></
dt>
If <
strong class="userinput"><
code>yes</
code></
strong>, the server will keep
information for this zone, which can be dumped to the
<
span><
strong class="command">statistics-file</
strong></
span> defined in
<
dt><
span class="term"><
span><
strong class="command">sig-validity-interval</
strong></
span></
span></
dt>
<
span><
strong class="command">sig-validity-interval</
strong></
span> in <
a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called “Tuning”</
a>.
<
dt><
span class="term"><
span><
strong class="command">transfer-source</
strong></
span></
span></
dt>
<
span><
strong class="command">transfer-source</
strong></
span> in <
a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called “Zone Transfers”</
a>
<
dt><
span class="term"><
span><
strong class="command">transfer-source-v6</
strong></
span></
span></
dt>
<
span><
strong class="command">transfer-source-v6</
strong></
span> in <
a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called “Zone Transfers”</
a>
<
dt><
span class="term"><
span><
strong class="command">alt-transfer-source</
strong></
span></
span></
dt>
<
span><
strong class="command">alt-transfer-source</
strong></
span> in <
a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called “Zone Transfers”</
a>
<
dt><
span class="term"><
span><
strong class="command">alt-transfer-source-v6</
strong></
span></
span></
dt>
<
span><
strong class="command">alt-transfer-source-v6</
strong></
span> in <
a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called “Zone Transfers”</
a>
<
dt><
span class="term"><
span><
strong class="command">use-alt-transfer-source</
strong></
span></
span></
dt>
<
span><
strong class="command">use-alt-transfer-source</
strong></
span> in <
a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called “Zone Transfers”</
a>
<
dt><
span class="term"><
span><
strong class="command">notify-source</
strong></
span></
span></
dt>
<
span><
strong class="command">notify-source</
strong></
span> in <
a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called “Zone Transfers”</
a>
<
dt><
span class="term"><
span><
strong class="command">notify-source-v6</
strong></
span></
span></
dt>
<
span><
strong class="command">notify-source-v6</
strong></
span> in <
a href="Bv9ARM.ch06.html#zone_transfers" title="Zone Transfers">the section called “Zone Transfers”</
a>.
<
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>
See the description in <
a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called “Tuning”</
a>.
<
dt><
span class="term"><
span><
strong class="command">ixfr-from-differences</
strong></
span></
span></
dt>
<
span><
strong class="command">ixfr-from-differences</
strong></
span> in <
a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called “Boolean Options”</
a>.
<
dt><
span class="term"><
span><
strong class="command">key-directory</
strong></
span></
span></
dt>
<
span><
strong class="command">key-directory</
strong></
span> in <
a href="Bv9ARM.ch06.html#options" title="options Statement Definition and Usage">the section called “<
span><
strong class="command">options</
strong></
span> Statement Definition and
<
dt><
span class="term"><
span><
strong class="command">multi-master</
strong></
span></
span></
dt>
See the description of <
span><
strong class="command">multi-master</
strong></
span> in
<
a href="Bv9ARM.ch06.html#boolean_options" title="Boolean Options">the section called “Boolean Options”</
a>.
<
dt><
span class="term"><
span><
strong class="command">masterfile-format</
strong></
span></
span></
dt>
See the description of <
span><
strong class="command">masterfile-format</
strong></
span>
in <
a href="Bv9ARM.ch06.html#tuning" title="Tuning">the section called “Tuning”</
a>.
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="dynamic_update_policies"></
a>Dynamic Update Policies</
h4></
div></
div></
div>
<
span class="acronym">BIND</
span> 9 supports two alternative
methods of granting clients
the right to perform dynamic updates to a zone,
configured by the <
span><
strong class="command">allow-update</
strong></
span>
<
span><
strong class="command">update-policy</
strong></
span> option,
The <
span><
strong class="command">allow-update</
strong></
span> clause works the
way as in previous versions of <
span class="acronym">BIND</
span>. It grants given clients the
permission to update any record of any name in the zone.
The <
span><
strong class="command">update-policy</
strong></
span> clause is new
in <
span class="acronym">BIND</
span>
9 and allows more fine-grained control over what updates are
A set of rules is specified, where each rule either grants or
permissions for one or more names to be updated by one or more
If the dynamic update request message is signed (that is, it
either a TSIG or SIG(0) record), the identity of the signer can
Rules are specified in the <
span><
strong class="command">update-policy</
strong></
span> zone
option, and are only meaningful for master zones. When the <
span><
strong class="command">update-policy</
strong></
span> statement
is present, it is a configuration error for the <
span><
strong class="command">allow-update</
strong></
span> statement
to be present. The <
span><
strong class="command">update-policy</
strong></
span>
examines the signer of a message; the source address is not
This is how a rule definition looks:
<
pre class="programlisting">
( <
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>]
Each rule grants or denies privileges. Once a message has
successfully matched a rule, the operation is immediately
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 in accordance with the nametype field, and the type
the types specified in the type field.
The identity field specifies a name or a wildcard name.
is the name of the TSIG or SIG(0) key used to sign the update
TKEY exchange has been used to create a shared secret, the
shared secret is the same as the identity of the key used to
TKEY exchange. When the <
em class="replaceable"><
code>identity</
code></
em> field specifies a
wildcard name, it is subject to DNS wildcard expansion, so the
to multiple identities. The <
em class="replaceable"><
code>identity</
code></
em> field must
contain a fully qualified domain name.
The <
em class="replaceable"><
code>nametype</
code></
em> field has 4
<
code class="varname">name</
code>, <
code class="varname">subdomain</
code>,
<
code class="varname">wildcard</
code>, and <
code class="varname">self</
code>.
<
div class="informaltable"><
table border="1">
<
code class="varname">name</
code>
Exact-match semantics. This rule matches when the
name being updated is identical to the contents of the
<
em class="replaceable"><
code>name</
code></
em> field.
<
code class="varname">subdomain</
code>
This rule matches when the name being updated
is a subdomain of, or identical to, the contents of
<
em class="replaceable"><
code>name</
code></
em> field.
<
code class="varname">wildcard</
code>
The <
em class="replaceable"><
code>name</
code></
em> field
subject to DNS wildcard expansion, and this rule
being updated name is a valid expansion of the
<
code class="varname">self</
code>
This rule matches when the name being updated
matches the contents of the <
em class="replaceable"><
code>identity</
code></
em> field.
The <
em class="replaceable"><
code>name</
code></
em> field
is ignored, but should be
the same as the <
em class="replaceable"><
code>identity</
code></
em> field. The
<
code class="varname">self</
code> nametype is most
useful when allowing using
one key per name to update, where the key has the same
to be updated. The <
em class="replaceable"><
code>identity</
code></
em> would be
specified as <
code class="constant">*</
code> in
In all cases, the <
em class="replaceable"><
code>name</
code></
em>
specify a fully qualified domain name.
If no types are explicitly specified, this rule matches all
RRSIG, NS, SOA, and NSEC. Types may be specified by name, including
"ANY" (ANY matches all types except NSEC, which can never be
Note that when an attempt is made to delete all records
name, the rules are checked for each existing record type.
<
div class="sect1" lang="en">
<
div class="titlepage"><
div><
div><
h2 class="title" style="clear: both">
<
a name="id2557480"></
a>Zone File</
h2></
div></
div></
div>
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
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>
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
and implemented in the DNS. These are also included.
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2557498"></
a>Resource Records</
h4></
div></
div></
div>
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 name servers, 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.ch06.html#the_sortlist_statement" title="The sortlist Statement">the section called “The <
span><
strong class="command">sortlist</
strong></
span> Statement”</
a> and <
a href="Bv9ARM.ch06.html#rrset_ordering" title="RRset Ordering">the section called “RRset Ordering”</
a>.
The components of a Resource Record are:
<
div class="informaltable"><
table border="1">
The domain name where the RR is found.
An encoded 16 bit value that specifies
the type of the resource record.
The time to live of the RR. This field
is a 32 bit integer in units of seconds, and is
resolvers when they cache RRs. The TTL describes how
be cached before it should be discarded.
An encoded 16 bit value that identifies
a protocol family or instance of a protocol.
The resource data. The format of the
data is type (and sometimes class) specific.
The following are <
span class="emphasis"><
em>types</
em></
span> of valid RRs:
<
div class="informaltable"><
table border="1">
A host address. In the IN class, this is a
32-bit IP address. Described in RFC 1035.
IPv6 address. Described in RFC 1886.
IPv6 address. This can be a partial
address (a suffix) and an indirection to the name
address (the prefix) can be found. Experimental.
Location of AFS database servers.
Experimental. Described in RFC 1183.
Address prefix list. Experimental.
Holds a digital certificate.
Identifies the canonical name of an alias.
Replaces the domain name specified with
another name to be looked up, effectively aliasing an
subtree of the domain name space rather than a single
as in the case of the CNAME RR.
Stores a public key associated with a signed
DNS zone. Described in RFC 4034.
Stores the hash of a public key associated with a
signed DNS zone. Described in RFC 4034.
Specifies the global position. Superseded by LOC.
Identifies the CPU and OS used by a host.
Representation of ISDN addresses.
Experimental. Described in RFC 1183.
Stores a public key associated with a
DNS name. Used in original DNSSEC; replaced
by DNSKEY in DNSSECbis, but still used with
SIG(0). Described in RFCs 2535 and 2931.
Identifies a key exchanger for this
DNS name. Described in RFC 2230.
For storing GPS info. Described in RFC 1876.
Identifies a mail exchange for the domain.
a 16 bit preference value (lower is better)
followed by the host name of the mail exchange.
Described in RFC 974, RFC 1035.
Name authority pointer. Described in RFC 2915.
A network service access point.
The authoritative name server for the
domain. Described in RFC 1035.
Used in DNSSECbis to securely indicate that
RRs with an owner name in a certain name interval do
a zone and indicate what RR types are present for an
Used in DNSSEC to securely indicate that
RRs with an owner name in a certain name interval do
a zone and indicate what RR types are present for an
Used in original DNSSEC; replaced by NSEC in
A pointer to another part of the domain
name space. Described in RFC 1035.
Provides mappings between RFC 822 and X.400
addresses. Described in RFC 2163.
Information on persons responsible
for the domain. Experimental. Described in RFC 1183.
Contains DNSSECbis signature data. Described
Route-through binding for hosts that
do not have their own direct wide area network
Experimental. Described in RFC 1183.
Contains DNSSEC signature data. Used in
original DNSSEC; replaced by RRSIG in
DNSSECbis, but still used for SIG(0).
Described in RFCs 2535 and 2931.
Identifies the start of a zone of authority.
Information about well known network
services (replaces WKS). Described in RFC 2782.
Text records. Described in RFC 1035.
Information about which well known
network services, such as SMTP, that a domain
Representation of X.25 network addresses.
Experimental. Described in RFC 1183.
The following <
span class="emphasis"><
em>classes</
em></
span> of resource records
are currently valid in the DNS:
<
div class="informaltable"><
table border="1">
CHAOSnet, a LAN protocol created at MIT in the
Rarely used for its historical purpose, but reused for
built-in server information zones,
e.g.,
Hesiod, an information service
developed by MIT's Project Athena. It is used to share
about various systems databases, such as users,
The owner name is often implicit, rather than forming an
part of the RR. For example, many name servers internally form
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)
fits the needs of the resource being described.
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
data in zones; it is also timed out, but by the refreshing
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
of Internet performance suggest that these times should be on
order of days for the typical host. If a change can be
the TTL can be reduced prior to the change to minimize
during the change, and then increased back to its former value
The data in the RDATA section of RRs is carried as a combination
of binary strings and domain names. The domain names are
used as "pointers" to other data in the DNS.
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2558981"></
a>Textual expression of RRs</
h4></
div></
div></
div>
RRs are represented in binary form in the packets of the DNS
protocol, and are usually represented in highly encoded form
stored in a name server or resolver. In the examples provided
RFC 1034, a style similar to that used in master files was
in order to show the contents of RRs. In this format, most RRs
are shown on a single line, although continuation lines are
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
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
parsing, type and class mnemonics are disjoint, TTLs are
and the type mnemonic is always last. The IN class and TTL
are often omitted from examples in the interests of clarity.
The resource data or RDATA section of the RR are given using
knowledge of the typical representation for the data.
For example, we might show the RRs carried in a message as:
<
div class="informaltable"><
table border="1">
<
code class="literal">MX</
code>
<
code class="literal">MX</
code>
<
code class="literal">A</
code>
<
code class="literal">128.9.0.32</
code>
<
code class="literal">A</
code>
<
code class="literal">10.1.0.52</
code>
<
code class="literal">A</
code>
<
code class="literal">10.2.0.27</
code>
<
code class="literal">A</
code>
<
code class="literal">128.9.0.33</
code>
The MX RRs have an RDATA section which consists of a 16 bit
number followed by a domain name. The address RRs use a
IP address format to contain a 32 bit internet address.
This example shows six RRs, with two RRs at each of three
<
div class="informaltable"><
table border="1">
<
code class="literal">IN A</
code>
<
code class="literal">10.0.0.44</
code>
<
code class="literal">CH A</
code>
<
code class="literal">
MIT.EDU. 2420</
code>
This example shows two addresses for
<
code class="literal">
XX.LCS.MIT.EDU</
code>, each of a different class.
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2559433"></
a>Discussion of MX Records</
h3></
div></
div></
div>
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 data, a domain name matched with a relevant datum,
and stored with some additional type information to help systems
determine when the RR is relevant.
MX records are used to control delivery of email. The data
specified in the record is a priority and a domain name. The
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 numbers do not have any absolute meaning — they are
only respective to other MX records for that domain name. The
name given is the machine to which the mail will be delivered.
It <
span class="emphasis"><
em>must</
em></
span> have an associated address record
(A or AAAA) — CNAME is not sufficient.
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.
the mail will be delivered to the server specified in the MX
<
div class="informaltable"><
table border="1">
<
code class="literal">IN</
code>
<
code class="literal">MX</
code>
<
code class="literal">10</
code>
<
code class="literal">IN</
code>
<
code class="literal">MX</
code>
<
code class="literal">10</
code>
<
code class="literal">IN</
code>
<
code class="literal">MX</
code>
<
code class="literal">20</
code>
<
code class="literal">IN</
code>
<
code class="literal">A</
code>
<
code class="literal">10.0.0.1</
code>
<
code class="literal">IN</
code>
<
code class="literal">A</
code>
<
code class="literal">10.0.0.2</
code>
Mail delivery will be attempted to <
code class="literal">
mail.example.com</
code> and
any order), and if neither of those succeed, delivery to <
code class="literal">
mail.backup.org</
code> will
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="Setting_TTLs"></
a>Setting TTLs</
h3></
div></
div></
div>
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
<
div class="informaltable"><
table border="1">
The last field in the SOA is the negative
caching TTL. This controls how long other servers will
(NXDOMAIN) responses from you.
negative caching is 3 hours (3h).
The $TTL directive at the top of the
zone file (before the SOA) gives a default TTL for every
Each RR can have a TTL as the second
field in the RR, which will control how long other
All of these TTLs default to units of seconds, though units
can be explicitly specified, for example, <
code class="literal">1h30m</
code>.
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2559985"></
a>Inverse Mapping in IPv4</
h3></
div></
div></
div>
Reverse name resolution (that is, translation from IP address
to name) is achieved by means of the <
span class="emphasis"><
em>
in-addr.arpa</
em></
span> domain
and PTR records. Entries in the
in-addr.arpa domain are made in
least-to-most significant order, read left to right. This is the
opposite order to the way IP addresses are usually written. Thus,
a machine with an IP address of 10.1.2.3 would have a
whose data field is the name of the machine or, optionally,
PTR records if the machine has more than one name. For example,
in the [<
span class="optional">
example.com</
span>] domain:
<
div class="informaltable"><
table border="1">
<
code class="literal">$ORIGIN</
code>
<
code class="literal">3</
code>
<
div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<
h3 class="title">Note</
h3>
The <
span><
strong class="command">$ORIGIN</
strong></
span> lines in the examples
are for providing context to the examples only-they do not
appear in the actual usage. They are only used here to indicate
that the example is relative to the listed origin.
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2560180"></
a>Other Zone File Directives</
h3></
div></
div></
div>
The Master File Format was initially defined in RFC 1035 and
has subsequently been extended. While the Master File Format
is class independent all records in a Master File must be of the
Master File Directives include <
span><
strong class="command">$ORIGIN</
strong></
span>, <
span><
strong class="command">$INCLUDE</
strong></
span>,
and <
span><
strong class="command">$TTL.</
strong></
span>
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2560202"></
a>The <
span><
strong class="command">$ORIGIN</
strong></
span> Directive</
h4></
div></
div></
div>
Syntax: <
span><
strong class="command">$ORIGIN</
strong></
span>
<
em class="replaceable"><
code>domain-name</
code></
em>
[<
span class="optional"><
em class="replaceable"><
code>comment</
code></
em></
span>]
<
p><
span><
strong class="command">$ORIGIN</
strong></
span>
sets the domain name that will be appended to any
unqualified records. When a zone is first read in there
is an implicit <
span><
strong class="command">$ORIGIN</
strong></
span>
<<
code class="varname">zone-name</
code>><
span><
strong class="command">.</
strong></
span>
The current <
span><
strong class="command">$ORIGIN</
strong></
span> is appended to
the domain specified in the <
span><
strong class="command">$ORIGIN</
strong></
span>
argument if it is not absolute.
<
pre class="programlisting">
<
pre class="programlisting">
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2560263"></
a>The <
span><
strong class="command">$INCLUDE</
strong></
span> Directive</
h4></
div></
div></
div>
Syntax: <
span><
strong class="command">$INCLUDE</
strong></
span>
<
em class="replaceable"><
code>filename</
code></
em>
<
em class="replaceable"><
code>origin</
code></
em> </
span>]
[<
span class="optional"> <
em class="replaceable"><
code>comment</
code></
em> </
span>]
Read and process the file <
code class="filename">filename</
code> as
if it were included into the file at this point. If <
span><
strong class="command">origin</
strong></
span> is
specified the file is processed with <
span><
strong class="command">$ORIGIN</
strong></
span> set
to that value, otherwise the current <
span><
strong class="command">$ORIGIN</
strong></
span> is
The origin and the current domain name
revert to the values they had prior to the <
span><
strong class="command">$INCLUDE</
strong></
span> once
<
div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<
h3 class="title">Note</
h3>
RFC 1035 specifies that the current origin should be restored
an <
span><
strong class="command">$INCLUDE</
strong></
span>, but it is silent
domain name should also be restored. BIND 9 restores both of
This could be construed as a deviation from RFC 1035, a
<
div class="sect3" lang="en">
<
div class="titlepage"><
div><
div><
h4 class="title">
<
a name="id2560332"></
a>The <
span><
strong class="command">$TTL</
strong></
span> Directive</
h4></
div></
div></
div>
Syntax: <
span><
strong class="command">$TTL</
strong></
span>
<
em class="replaceable"><
code>default-ttl</
code></
em>
<
em class="replaceable"><
code>comment</
code></
em> </
span>]
Set the default Time To Live (TTL) for subsequent records
with undefined TTLs. Valid TTLs are of the range 0-2147483647
<
p><
span><
strong class="command">$TTL</
strong></
span>
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="id2560437"></
a><
span class="acronym">BIND</
span> Master File Extension: the <
span><
strong class="command">$GENERATE</
strong></
span> Directive</
h3></
div></
div></
div>
Syntax: <
span><
strong class="command">$GENERATE</
strong></
span>
<
em class="replaceable"><
code>range</
code></
em>
<
em class="replaceable"><
code>lhs</
code></
em>
[<
span class="optional"><
em class="replaceable"><
code>ttl</
code></
em></
span>]
[<
span class="optional"><
em class="replaceable"><
code>class</
code></
em></
span>]
<
em class="replaceable"><
code>type</
code></
em>
<
em class="replaceable"><
code>rhs</
code></
em>
[<
span class="optional"><
em class="replaceable"><
code>comment</
code></
em></
span>]
<
p><
span><
strong class="command">$GENERATE</
strong></
span>
is used to create a series of resource records that only
differ from each other by an
iterator. <
span><
strong class="command">$GENERATE</
strong></
span> can be used to
easily generate the sets of records required to support
sub /24 reverse delegations described in RFC 2317:
$GENERATE 1-2 0 NS SERVER$.EXAMPLE.
$GENERATE 1-127 $ CNAME $.0</
pre>
<
div class="informaltable"><
table border="1">
<
p><
span><
strong class="command">range</
strong></
span></
p>
This can be one of two forms: start-stop
1. All of start, stop and step must be positive.
<
p><
span><
strong class="command">lhs</
strong></
span></
p>
<
p><
span><
strong class="command">lhs</
strong></
span>
describes the owner name of the resource records
to be created. Any single <
span><
strong class="command">$</
strong></
span>
symbols within the <
span><
strong class="command">lhs</
strong></
span> side
are replaced by the iterator value.
To get a $ in the output you need to escape the
<
span><
strong class="command">$</
strong></
span> using a backslash
<
span><
strong class="command">\</
strong></
span>,
e.g. <
span><
strong class="command">\$</
strong></
span>. The
<
span><
strong class="command">$</
strong></
span> may optionally be followed
by modifiers which change the offset from the
iterator, field width and base.
Modifiers are introduced by a
<
span><
strong class="command">{</
strong></
span> immediately following the
<
span><
strong class="command">$</
strong></
span> as
<
span><
strong class="command">${offset[,width[,base]]}</
strong></
span>.
e.g. <
span><
strong class="command">${-20,3,d}</
strong></
span> which
subtracts 20 from the current value, prints the
result as a decimal in a zero padded field of
Available output forms are decimal
(<
span><
strong class="command">d</
strong></
span>), octal
(<
span><
strong class="command">o</
strong></
span>) and hexadecimal
(<
span><
strong class="command">x</
strong></
span> or <
span><
strong class="command">X</
strong></
span>
for uppercase). The default modifier is
<
span><
strong class="command">${0,0,d}</
strong></
span>. If the
<
span><
strong class="command">lhs</
strong></
span> is not absolute, the
current <
span><
strong class="command">$ORIGIN</
strong></
span> is appended
For compatibility with earlier versions <
span><
strong class="command">$$</
strong></
span> is still
recognized a indicating a literal $ in the output.
<
p><
span><
strong class="command">ttl</
strong></
span></
p>
<
p><
span><
strong class="command">ttl</
strong></
span>
specifies the ttl of the generated records. If
not specified this will be inherited using the
normal ttl inheritance rules.
<
p><
span><
strong class="command">class</
strong></
span>
and <
span><
strong class="command">ttl</
strong></
span> can be
<
p><
span><
strong class="command">class</
strong></
span></
p>
<
p><
span><
strong class="command">class</
strong></
span>
specifies the class of the generated records.
This must match the zone class if it is
<
p><
span><
strong class="command">class</
strong></
span>
and <
span><
strong class="command">ttl</
strong></
span> can be
<
p><
span><
strong class="command">type</
strong></
span></
p>
At present the only supported types are
PTR, CNAME, DNAME, A, AAAA and NS.
<
p><
span><
strong class="command">rhs</
strong></
span></
p>
rhs is a domain name. It is processed
The <
span><
strong class="command">$GENERATE</
strong></
span> directive is a <
span class="acronym">BIND</
span> extension
and not part of the standard zone file format.
BIND 8 does not support the optional TTL and CLASS fields.
<
div class="sect2" lang="en">
<
div class="titlepage"><
div><
div><
h3 class="title">
<
a name="zonefile_format"></
a>Additional File Formats</
h3></
div></
div></
div>
In addition to the standard textual format, BIND 9
supports the ability to read or dump to zone files in
other formats. The <
code class="constant">raw</
code> format is
currently available as an additional format. It is a
binary format representing BIND 9's internal data
structure directly, thereby remarkably improving the
For a primary server, a zone file in the
<
code class="constant">raw</
code> format is expected to be
generated from a textual zone file by the
<
span><
strong class="command">named-compilezone</
strong></
span> command. For a
secondary server or for a dynamic zone, it is automatically
generated (if this format is specified by the
<
span><
strong class="command">masterfile-format</
strong></
span> option) when
<
span><
strong class="command">named</
strong></
span> dumps the zone contents after
zone transfer or when applying prior updates.
If a zone file in a binary format needs manual modification,
it first must be converted to a textual form by the
<
span><
strong class="command">named-compilezone</
strong></
span> command. All
necessary modification should go to the text file, which
should then be converted to the binary form by the
<
span><
strong class="command">named-compilezone</
strong></
span> command again.
Although the <
code class="constant">raw</
code> format uses the
network byte order and avoids architecture-dependent
data alignment so that it is as much portable as
possible, it is primarily expected to be used inside
the same single system. In order to export a zone
file in the <
code class="constant">raw</
code> format or make a
portable backup of the file, it is recommended to
convert the file to the standard textual representation.
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