Q. How do I test or check reverse DNS for given IP address under Linux or Windows XP/Server 2003?

A. Reverse DNS lookup (also known as rDNS) 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. A reverse lookup is often referred to simply as reverse resolving, or more specifically reverse DNS lookups.

The most common uses of the reverse DNS are:
=> Anti-spam
=> Network troubleshooting
=> Avoid spammers and phishers using a forward confirmed reverse DNS etc

You can use standard UNIX / Linux utilities such as nslookup, dig or hosts to find out reverse DNS of a given IP address.

Task: Find Reverse DNS for IP under Linux/UNIX

$ host
Output: domain name pointer cyberciti.org.

IP is reverse mapped to cyberciti.org.

Task: Find Reverse DNS for IP under Linux/UNIX/Windows

nslookup works under Windows and UNIX like oses:

Non-authoritative answer:      name = cyberciti.org.
Authoritative answers can be found from: