DOMAIN Reverse Data File Format for TCP/IP

Purpose

Stores reverse name resolution information for the named daemon.

Description

The Reverse Data file is one of the DOMAIN data files and contains address to name resolution mapping information for all machines in the name server's zone of authority. The name of the reverse hosts data file is specified in the named boot file. There may be more than one reverse hosts data file per primary name server.

All entries in this file must be in Standard Resource Record Format. Valid resource records in this file are:

• Start of Authority (SOA)
• Name Server (NS)
• Pointer (PTR)

Except for comments (starting with a ; (semicolon) and continuing to the end of the line), the resource records in the data files generally follow the format of the resource records that the named daemon returns in response to queries from resolver routines.

Two awk scripts, addrs.awk and hosts.awk, are provided in the /usr/samples/tcpip directory to assist you in converting your existing /etc/hosts file to named data files. The awk scripts also contain instructions for their use. Refer to these files for more information on the conversion.

Examples

The following examples show the various ways to use the DOMAIN Reverse Data file. In these examples, two networks are represented: abc and xyz.

Network abc consists of:

• gobi.abc, the primary name server for the abc network, 192.9.201.2
• mojave.abc, a host machine, 192.9.201.6
• sandy.abc, secondary name server for the abc network and gateway between abc and xyz, 192.9.201.3

Network xyz consists of:

• kalahari.xyz, primary name server for the xyz network, 160.9.201.4
• lopnor.xyz, a host machine and cache-only name server for the xyz network, 160.9.201.5
• sahara.xyz, a host machine, 160.9.201.13
• sandy.xyz, a secondary name server for the xyz network and gateway between abc and xyz, 160.9.201.3
  Note: Host sandy, a gateway host, is on both networks and also serves as secondary name server for both.
  1. The reverse data file for gobi.abc, primary name server for network abc, contains these entries:

     ;
     ;primary reverse host data file for abc - gobi.abc
     ;
     @                          IN       SOA     gobi.abc.  root.gobi.abc.  (
                                                 1:1      ;serial
                                                 3600     ;refresh
                                                 600      ;retry
                                                 3600000;expire
                                                 86400    ;minimum
                                                 )
     ;nameservers for abc
                                         IN      NS       gobi.abc.
     ;other nameservers
                                         IN      NS       kalahari.xyz.
     4.201.9.160.in-addr.arpa   IN       PTR     kalahari.xyz
     ;
     ;define all hosts in abc
     2                                   IN      PTR      gobi.abc.
     3                                   IN      PTR      sandy.abc.
     6                                   IN      PTR      mojave.abc.

  2. The reverse data file for kalahari.xyz, primary name server for network xyz, contains these entries:

     ;
     ;primary reverse host data file for xyz - kalahari.xyz
     ;
     @                 IN       SOA      kalahari.xyz. root.kalahari.xyz. (
                                         1:1     ;serial
                                         3600    ;refresh
                                         600     ;retry
                                         3600000;expire
                                         86400   ;minimum
                                         )
     ;nameservers for xyz
                                         IN       NS      kalahari.xyz.
     ;other nameservers
                                         IN       NS      gobi.abc.
     2.201.9.192.in-addr.arpa   IN       PTR      gobi.abc
     ;
     ;define all hosts in xyz
     4.201                               IN       PTR     kalahari.xyz.
     13.201                              IN       PTR     sahara.xyz.
     5.201                               IN       PTR     lopnor.xyz.
     3.201                               IN       PTR     sandy.xyz.

Files