I beg your pardon? Waterboarding is not torture? I'm sorry, but by any definition you care to mention being exposed to "simulated drowning" is torture. If you read up on the practice you'll find that it's slightly more serious than someone splashing a bit of water on you. For extra points go read http://en.wikipedia.org/wiki/Waterboarding and become enlightened. Yes, it doesn't involve cutting people's hands off, breaking legs, setting fire to their eyeballs or anything of a more graphical nature. However, calling it "not torture" is ignorant at best.

If you use anything bigger/better/faster/stronger than simple un-managed switches, such as Cisco, HP, Extreme (and so on), you will find that the switch exports its MAC/CAM table via SNMP. This means that you can poll MAC tables of managed switches in different switching domains (separated by routers). If you are interested, tools like http://www.netdisco.org/ will do this for you quite nicely.