Reverse DNS Testing
Reverse DNS lookup is a process to determine the hostname associated with a given IP address.
Typically, the DNS is used to determine what IP address is associated with a given hostname;
so to reverse resolve a known IP address is to lookup what the associated hostname for it is.
A reverse lookup is often referred to simply as reverse resolving, or more specifically
reverse DNS lookups.
Reverse DNS lookups for IPv4 addresses use the special domain in-addr.arpa. An IPv4 address
is represented in the in-addr.arpa domain by a sequence of bytes in reverse order,
represented as decimal numbers, separated by dots with the suffix .in-addr.arpa.
For example, the reverse lookup domain name corresponding to the IPv4 address
220.127.116.11 is 18.104.22.168.in-addr.arpa. A host name for 22.214.171.124 can be obtained
by issuing a DNS query for the PTR record for that special address 126.96.36.199.in-addr.arpa...