I have three Mac's on the same network for printer and file sharing. There are two routers also on the same network. One has IP 192.168.1.1 and the other 192.168.1.254. I have set it up so that two of the Mac's only communicate with one of the routers. And that the third Mac only communicates with the other router. It is crucial that the Mac's only communicate with the router they are supposed to. I am concerned that the Network control panel on one of the Mac's might some time in the future revert to the default settings. That might happen as a result of, for instance, the Mac crashing, or the malfunction of a third party application (such as Diskwarrior or Tech Tool Pro). As the default is for the gateway address to be assigned dynamically the Mac might then communicate with the wrong router. At present I cannot see any way of preventing that happening and also have all three macs on the same network for printer and file sharing. It seems that to provide protection from this happening I have to disconnect the third Mac from the network. Of course then I would I have to find another way to do printer and file sharing. Anyone have any better ideas?