This is related to BackTrack how? Unless there is a Backrack connection this post is where discussion on this will have to end, we are not a general IT support forum.
If the local box is Internet connected, I would assume that your system with the Internet accessible IP address (probably your router) is using NAT to allow that box to talk to the Net. You need to port forward the appropriate ports (TCP 22 if you want SSH access) from the router to that local box.




