i'm not a senior member, but you aren't entirely on track because if he is using a NAT scheme, the router/firewall knows where to forward the communication based on port... ex: 3 computers behind a firewall, NAT enabled w/ dhcp. computer 1 talking to google, computer 2 talking to yahoo, and computer 3 talking to AO all using port 80, all appearing to be the same IP address, but behind the router the comuters have been moved to ephemeral ports (typically greater than 1024) and the router knows which computer is using which ephemeral port.