Networking Guide
Chapter 6, Configuring the Domain Name Service

Sample /etc/named.rev file

Sample /etc/named.rev file

The in-addr.arpa domain was created because Internet host addresses do not fall within domain boundaries. This special domain allows inverse mapping: that of IP addresses to domain names. The in-addr.arpa domain has several labels preceding it -- an inverse reading of the host portion of the host's Internet address. For example, the host 132.147.118.1 is located in the domain 147.132.in-addr.arpa. This reversal of the address is awkward to read but allows for the natural grouping of hosts in a network.

The reverse hosts file, named.rev(SFF) (or databasename.rev), is a special hosts file for the reverse domain. As with all hosts files, it starts with SOA (start of authority) and NS (name server) records. These are followed by a series of PTR (pointer) records, each of which points from a reverse mapping of the machine's IP address to its hostname.

Here is a sample of mynet.rev: 

   ;
   ;    @(#)mynet.rev    2.0      94/05/27
   ;
   @            IN   SOA   volga.mynet.COM. dave.mynet.COM (
                           1993091901 ; Serial
                           10800     ; Refresh
                           1800      ; Retry
                           3600000   ; Expire
                           259200 )   ; Minimum
                IN   NS    volga.mynet.COM
                IN   NS    istanbul.mynet.COM
   1.118        IN   PTR   volga.mynet.COM
   2.118        IN   PTR   columbia.mynet.COM
   3.118        IN   PTR   thames.mynet.COM
   4.118        IN   PTR   seine.mynet.COM
   5.118        IN   PTR   yangtze.mynet.COM
   6.118        IN   PTR   mekong.mynet.COM
   ; additional addresses to follow in the same format
   1.246        IN   PTR   volga.mynet.COM
   2.246        IN   PTR   london.mynet.COM
   3.246        IN   PTR   paris.mynet.COM
   ; additional addresses to follow in the same format