Inside the Routing Table

A router job is to forward each packet toward its destination. To do this it consults a routing table, a list of known networks and how to reach them. Every packet that arrives is checked against this table to choose the next step. This lesson opens the routing table and explains the entries a router uses to make forwarding decisions.

Each routing table entry maps a destination network to a next hop and an outgoing interface. The destination is written as a network and prefix, like 10.0.0.0/8. The next hop is the address of the next router on the path, and the interface is the port to send through. Some entries also list a metric and the route source.