Managing Mission - Critical Domains and DNS

PTR

Think of a PTR record as the flipside of an A record or a hostname lookup. A records specify IP addresses of a hostname, while PTR records go the opposite direction: they look up the hostname of a given IP address.

Here is the PTR RR Syntax:

<OWNER-NAME> IN PTR <hostname>

In PTR records, the OWNER-NAME will be an IP address, expressed in reverse or inverted notation, relative to the current $ORIGIN of the zone; while the Right-Hand Side (RHS) will be a hostname.

What people often miss is that we are actually talking about two completely different branches of the DNS tree when we discuss a forward and a reverse lookup.

Consider the following:

www.example.com.    IN A     192.168.13.56

We are looking at this branch:

• Level 0: (the internet root) ...