What do you mean by the difference between network IP and pc IP? You mean their Internet IP and the IP address on their home network? IBIS will only see the former. And unless the player somehow owns a block of IP space (doubtful) they're not going to be able to just change their address on a whim. The best example of this I can think of is someone on a college network where the DHCP lease is very short. Also, you shouldnt be able to see the end user's MAC address of the device.