= Bind Zone Files =

'''BIND zone files''' come in two categories: '''forward zones''' (located in `/var/named/primary/*`) and '''reverse zones''' (located in `/var/named/reverse/*`).

Note that this format, standardized in [[https://tools.ietf.org/html/rfc1035|RFC 1035]], has been widely adopted outside of the BIND project.

<<TableOfContents>>

----



== Forward Zone ==

To check the configuration of the forward zone file for `example.com`, run...

{{{
named-checkzone -d example.com /var/named/primary/example.com
}}}



=== Example ===

This is a forward zone file for `example.com`.

{{{
$TTL 1D
@             IN      SOA       host1.example.com.  me.example.com.  (
                                10             ; Serial
                                8H             ; Refresh
                                2H             ; Retry
                                4W             ; Expire
                                1D )           ; Minimum
;
              IN      NS       host1
              IN      MX  10   host1
;
example.com.  IN      A        192.168.1.1
host1         IN      A        192.168.1.1
www           IN      CNAME    host1
ftp           IN      CNAME    host1
;
host2         IN      A        192.168.1.201
host3         IN      A        192.168.1.202
}}}



=== Structure ===

The first column is the '''fully qualified domain name''' ('''FQDN'''). If this column is omitted, the last-defined FQDN is implicitly referenced.

The second and third columns are the record type. The second column is almost always '''Internet''' ('''IN''').



=== Start of Authority ===

This line indicates that host1.example.com is the '''Start of Authority''' ('''SOA''') for the zone, and that `me@example.com` is the technical contact. `@` is a macro for the fully qualified domain name, defined in the `bind(8)` configuration.

{{{
@             IN      SOA       host1.example.com. me.example.com. 
}}}

Note the period is mandatory to indicate that they are FQDNs.



=== Name Server ===

This line indicates that the previously-defined FQDN is also the '''Name Server''' ('''NS''') for this zone.

{{{
              IN      NS       host1
}}}



=== Mail Exchange ===

This line indicates that the previously-defined FQDN is also hosting a mail server (or '''Mail Exchange''') ('''MX'''). It should be defined with a priority; here that is set to 10.

{{{
              IN      MX  10   galaxy
}}}

There are additional considerations for public MX records; see [[Email/DNSRecords|here]] for details.



=== Address ===

To define the address for a domain name, use '''Address''' ('''A''') records.

{{{
example.com.  IN      A        192.168.1.1
host1         IN      A        192.168.1.1
}}}

As with the SOA record, trailing periods are required to indicate a FQDN.

After this line, `host1` can be referenced as an address.

{{{
www           IN      CNAME    host1
}}}



----

== Reverse Zone ==

To check the configuration of the reverse zone file for `192.168.1.0/24`, run...

{{{
named-checkzone -d 1.168.192.in-addr.arpa /var/named/reverse/192.168.1
}}}



=== Example ===

This is a reverse zone file for `192.168.1.0/24`.

{{{
$TTL 1D
@             IN      SOA       host1.example.com.  me.example.com.  (
                                10             ; Serial
                                8H             ; Refresh
                                2H             ; Retry
                                4W             ; Expire
                                1D )           ; Minimum
;
              IN      NS        host1.example.com.
1             IN      PTR       host1.example.com.
;
201           IN      PTR       host2.example.com.     ; IP address for 'host2'
202           IN      PTR       host3.example.com.     ; IP address for 'host3'
}}}



----
CategoryRicottone