Controlling IP Address Resolution

HostNameLookups on

If you set the HostNameLookups directive to on then Apache will try to determine (resolve) the hostname corresponding to the client's IP-address when it logs the request.

With HostNameLookups set to off, an access_log entry may look like

192.168.200.4  someuser [12/Jun/2005:08:33:34      +0500] "GET /example.png HTTP/1.0" 200 1234

And with HostNameLookups set to on, the same entry would look like

unit12.example.com - someuser [12/Jun/2005:08:33:34      +0500] "GET /example.png HTTP/1.0" 200 1234

The next section explains the reverse process, how to replace IP addresses in logs with hostnames.