If the DHCP server on the network he is trying to join is working properly, it should provide the correct default gateway address for him, as well as DNS server addresses, unless he has some forced manually settings on his machine. Another point that might be relevant is that that address is a bit unusual for a default gateway, which is usually x.x.x.254, i.e. in his case I would have expected to see : 192.168.0.254.