K, just something to say.
I dont think your connection is a good one to be hosting on, most likely you have small upload wich isnt good for running a server. If you dont know, just google it.
second sv_lan 0 is your friend. If that doesnt work find out how to get into your firewall and open port 27015. Dont ask me how, I have given way too many explinitaions on how to open a linksys router.
www.google.com will help you, or if you ironcally have a linksys router, search for it inside thiese forums.
Plus its been a while since I had to use a linksys router, I dont have one to mess with at the moment.