Reverse DNS Lookup and Why Useful

IP:
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What Is Reverse DNS Lookup? (using the tool above)

A Reverse DNS (Domain Name System) Lookup is merely the opposite sequence of a DNS lookup. Moreover, with a normal DNS lookup, you query the DNS or hostname to get the IP address. To clarify, with a Reverse DNS Lookup, you query the IP address to find the hostname. Therefore, 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 74.125.142.147. 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 the Address and Routing Parameter Area (ARPA) top-level domain of the Internet.

Reverse DNS Lookup Diagram

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.

Why Is This Useful?

Using the tool above is very useful for a variety of purposes:

  • Finding spam emails. From IP address alone, it’s difficult to differentiate legitimate mail servers from spam servers. However, certain generic rDNS names can provide clues that the mail server is spam. This is where the reverse DNS lookup comes in.
  • Knowing who is visiting your website. Website visit logs usually contain IP addresses, which aren’t particularly useful for tracking exactly who is visiting your website. The process can be used to find the hostname of your visitors to give you a better picture of who is visiting your website. This is especially useful for those operating B2B businesses.