Recapping Routers

Hours 1, “What Is TCP/IP?,” and 9, “Network Hardware,” introduced you to the essential networking device known as a router. You learned that the role of the router is to forward datagrams by IP address. A router, therefore, is a network hardware device that implements the IP addressing scheme discussed in Hour 4, “The Internet Layer.” As you'll recall, a router is similar to a computer with multiple network cards connected to multiple network segments (refer to Figure 9.2). When a router receives a datagram through one of its ports, it inspects the datagram to determine the destination IP address. If the destination address is located on the network segment from which the message came, there is no need to forward the datagram, ...

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