. . the Linksys wireless Cable/DSL router with 4-port switch. Others like other brands but this one has worked OK for me. You don't have to use the cable/DSL port at all, just use it as a switch, or you can have it route through the Cable/DSL port to any other network.

I used one to route between two 192.168.n.n networks in a case where the client didn't want most of his network able to access the accounting network but wanted accounting to have access to the same Internet connection as everyone else.