Routers

Routers are any machine that listens to traffic and on one network, then directs it to go somewhere on another network. With this definition, HUBs would would not really fall under the definition of a router, but a switch might. A gateway is a router because it routes network traffic from one network to another. Routers can be a part of more than two networks. Routers can act as the gateway on many different networks all at the same time. Sometimes there can be more than one router connected to the same networks. With this kind of setup you can send network packets out one gateway address and receive the in coming packets from an entirely different machine and address.