I am a college student, and trying to setup iptables so I can use direct connect (with dctc). The DC++ FAQ has some information about what I need to tell iptables to do (sorry, I don't have enough posts to include URLs), but before I can set this up I'll need to find out my external ip, router ip, and client ip. I contacted my residential computing department, and they politely informed me that they couldn't help me get this information because of the potential for illegal file sharing, so I need to find out this information myself (it seemed clear from the e-mail that this would be OK as long as they didn't help me explicitly).

I'm guessing that I can find out the router ip by monitoring where the packets my computer gets are sent from. Is this correct? If so, how would I do this?

I'm not really sure what is meant by the terms "external ip" and "client ip," but I'm guessing that one or both of these is given in the output of ifconfig, but I'm not sure what these would be labelled. What do these terms mean, and how can I find them out?

Use ifconfig to see which networkinterfacecards (NIC) are up and which ip, subnet they have.
You can also use iplooks to check out the packeets runing around on your computer.

The terms external IP refers to the ip that users on the inet see your computer as. The internal/client ip is the ip of your nic.

Would be nice if you laied out how you connect to the net. Either using pppd or pppoe.

try "route -n" to see your default gateway. The default gateway is probably your routers internal ip.
Check your external ip by visiting http://www.whatismyip.com/