19.3.4. Reverse Name Resolution Zone Files
A reverse name resolution zone file is used to translate an IP address in a particular namespace into an FQDN. It looks very similar to a standard zone file, except that
PTR
resource records are used to link the IP addresses to a fully qualified domain name.
The following illustrates the layout of a
PTR
record:
<last-IP-digit> IN PTR <FQDN-of-system>
<last-IP-digit> IN PTR <FQDN-of-system> <last-IP-digit> IN PTR <FQDN-of-system> <last-IP-digit> IN PTR <FQDN-of-system> <last-IP-digit> IN PTR <FQDN-of-system>
The <last-IP-digit> is the last number in an IP address which points to a particular system's FQDN.
In the following example, IP addresses
10.0.1.1
through 10.0.1.6
are pointed to corresponding FQDNs. It can be located in /var/named/example.com.rr.zone
.
This zone file would be called into service with a
zone
statement in the named.conf
file similar to the following:
There is very little difference between this example and a standard
zone
statement, except for the zone name. Note that a reverse name resolution zone requires the first three blocks of the IP address reversed followed by .in-addr.arpa
. This allows the single block of IP numbers used in the reverse name resolution zone file to be associated with the zone.