I have a computer I'll call Laptop, connected to a Netgear router, connected to a cable modem, connected to the internet.
I have another computer I'll call Desktop, connected to an Asus router, connected to a DSL modem, connected to the internet.
Both computers are running openSUSE 12.3 and using KDE.
I have krdc available on Desktop and krfb available on Laptop.
I want to control Laptop from Desktop. I can set up an invitation on Laptop but, because it's behind a router, it shows the address as 192.168.nn.nn. Obviously, Desktop cannot find that address. If I use the actual address of the router, (not the real address) and the port number, I still get no connection.

My intention is to help a friend with his system. He's not comfortable with removing his computer from the router and creating a direct connection. I need to go through his router. So, how can I get this to work?