Reverse DNS lookup
A reverse DNS lookup may refer to any of the following:
1. Alternatively referred to as reverse resolving and rDNS, Reverse DNS lookup is the process of looking up an IP address to resolve a hostname instead of the other way around. This technique is often used to help diagnose networking related issues or to determine where network data is going.
2. A reverse lookup is also a method of locating an address from a phone number.