Networks

Just an issue one of my mates are having. He has this problem, the default gateway for the Local Area Network is not showing up. The network setup are as follows: All cables from individual PC are patched into a patch panel, patch cables from patch panel into 48 port switch, and 1x straight cable from switch into Router, and 1x crossover cable from the Routers WAN port into DSL Modem.

Whenever he takes off all the clients from the network (by taking off the cables on the switch) and putting them back on 1 by 1, the network runs fine and the default gateway shows up again for the LAN. But it would only run for a while and the default gateway would not show up again.

Any possible solution? Any help would be greatly appreciated.