In order to appreciate the role of a router, we need to take a look at how communication happens between hosts on different networks in a routed environment. For the purpose of these illustrations, I’m going to assume that our network is running the most popular routed protocol suite, TCP/IP. We’ll begin with a look at a simple internetwork consisting of two networks, both connected to a single router. This will be followed by a look at a larger internetwork, where multiple networks are connected via many routers.
