Justin and I were trying to setup a Linux box as a router for our DS3 transition.  We spent most of Friday working on it and couldn't get it to work at all.  I mapped it all out in Visio, wired three computers up to a hub and set them all up.  After about 5 minutes of fiddeling with it I got it to route between the two nic cards.  I can kill the "router" computer if I do a ping flood though, it's kind of cool.