Does XNA use specific game ports?  Can you set them?  I have a LAN game between 2 routers on the same network set as access points (the routers).  When I host a LAN game on one router and have someone try join on the other router it doesn't show up in the available sessions list.  It works if the two computers on on the same router though.  I'm thinking there are ports that are needed to be forwarded.  If so, what are they?  If not, how can I set them?  Thank you.

http://support.microsoft.com/kb/908874

Do those apply for LAN games?

Yep.

Thanks.