Networking Guide
Chapter 6, Configuring the Domain Name Service

PTR (domain name pointer) resource record

PTR (domain name pointer) resource record

PTR allows special names to point to some other location in the domain. The following example of a PTR record is used in setting up reverse pointers for the special in-addr.arpa domain. This line is from the example mynet.rev file. In this record, the ``name'' field is the network number of the host in reverse order. You only need to specify enough octets to make the name unique. For example, if all hosts are on network 132.147.118, then only the last octet needs to be specified. If hosts are on networks 132.147.118 and 132.147.246, then the last two octets need to be specified.

PTR records are needed by gethostbyaddr(SLIB). Note the trailing ''.'', which prevents the appending of the current $ORIGIN.

PTR names should be unique to the zone.

Here is an example of a PTR record:

   name   {ttl}   addr-class   PTR   real name
   3.118          IN           PTR   thames.mynet.COM.