How to use the Reverse DNS Tool
Reverse DNS is merely the reverse sequence of a DNS lookup. The Reverse DNS Tool requires you to enter the any IP address that has a corresponding host name. By entering the IP address into the Reverse DNS Lookup Tool, you are able to find the domain name associated with the corresponding IP.
For example, one IP address of Google.com is 126.96.36.199. If you were to type this IP address in the Reverse DNS Lookup Tool, it will return the host name of Google as listed in the database of ARPA, the Address and Routing Parameter Area (arpa) top-level domain of the Internet.
Note that some IP addresses will not return a domain name because there may be records indicating multiple domain names for a given IP address. Common examples of this include shared web hosting, where one IP address of the server is shared among one or more domains.