Asnumber

The AS Number Extension for Firefox displays the AS Number, and consequently the Internet Service Provider, of every website visited along with some additional interesting information for those interested in how the Internet works below the surface.  All data is updated daily and the prefix to AS number mapping is from a real DFZ BGP feed.

A nice little plug-in that can enumerate routing and ISP information to the target network you are testing.

It is available from here, a local version is available here.