Can you explain better exactly what you are trying to do?
The slingbox needs a port forwarded to it so you can contact it from outside. By default that is port 5001. If you then need access to more machines on the internal network, you would map additional ports to those machines. So for example, if you have an SSH server running, you could map port 22 on the router to port 22 on the SSH server. If you have an additional SSH server, you could then map the router's port 2222 to 22 on the secondary server's IP address (assuming your router can map port X to port Y, some only allow X to X, which in that case you would change the SSH server to listen to port 2222).