Reverse DNS Hostname Lookup

This page will attempt to make a lookup of a given hostname or IP address, and attempt to match it to the lookup of the result. It currently only supports IPv4 addresses. This tool will attempt to handle multihoming and other such tricks, so be sure to check the actual returned values to note if it is an exact match or not.

Enter a hostname or IP Address:

If the hostnames do not match, that may indicate that someone else is actually the owner of the network in question. Use common sense. : )

If a match is found, that is called a 'Forward Confirmed Reverse DNS', or FCrDNS, which is strongly suggested by RFC 1912 - "Make sure your PTR and A records match". There are several benefits of doing this:

1. Mail servers receiving mail from a system will perform such a check on the sending mail server as a loose check to verify that your machine is actually the owner of the address in question. This allows them to filter out zombie machines, for example.
2. It lets curious people know that the server administrator knows the basics of what they are doing, and care enough to do so according to RFC 1033 'Adding a host'. Check vekseid.com, for example.
3. If you configure your webserver properly, people can actually get to your site by typing in your ip address, as a sort of last resort if their DNS resolution fails.