IP addresses and geographical locations

A colleague of mine asked whether IP addresses could be "approximated" to physical location. As with most IT questions, "it depends" was a response I used frequently. Is there a service or program that can take a list of IP addresses and find/approximate the physical location to where the IP is?

Solution 1:

GeoIP databases, as folks are already mentioning, are the approximation of what you're talking about. The problem is that they're just that, data, and data that can be faulty.

As someone who works for a cable provider, whenever we do a fiber node move or shift a block of IPs from one CMTS to another, we can sometimes drastically mess up those databases until they're corrected.

As Maxmind explains:

We arrive at the accuracy figure by checking known IP address and location pairs against our database. We obtain the known IP location pairs from sites that ask the web visitor to provide their geographic location. The geographic location along with the web visitor's IP Address is forwarded to us.

Solution 2:

There's a free MaxMind GeoIP database, which I think is queryable online (or you can download the database and query against it). They also sell a more accurate database (as do other companies, I'm sure, but that's the one I know about).