Chapter 15 / 15.5 / 15.5.1

15.5.1 Packet Forwarding In Perspective

Every router maintains a routing table that identifies the networks it can reach and the next router, or next hop, that should receive packets destined for each network.

Rather than storing a route to every individual computer, routers maintain routes to networks. This hierarchical approach greatly reduces the amount of routing information that must be stored and exchanged.

A typical routing table contains information such as:

• the destination network;
• the network prefix;
• the next-hop router;
• the outgoing interface; and
• a routing metric indicating the preferred path.

When a packet arrives, the router compares the destination IP address with the entries in its routing table and selects the most appropriate route.