DNS lookup is used to determine which IP address is associated with a hostname, while a reverse DNS lookup is used for the opposite, to determine which hostname is associated with an IP addressA valid reverse lookup zone consists of the network id's octets in reverse order, with in-addr.arpa
at the end of the name.
For example, the reverse in-addr.arpa domain name for the IP address 192.168.0.1 is:
1.0.168.192.in-addr.arpa.
