Routing

Routing is the process of moving packets through an internetwork, such as the Internet.

Routing actually consists of two separate, but related, tasks:

1. Defining paths for the transmission of packets through an internetwork.
2. Forwarding packets based upon the defined paths.

Routing vs. Bridging and Switching

Routing is distinguished from bridging or switching by operating at the Network Layer of the OSI Model. Bridging and switching occur on the Data Link Layer.

Static vs. Dynamic Routing

Routing can be accomplished by manually entering the information necessary for packets to reach any part of the internetwork into each router. This is called static routing.

Static routing works reasonably well for very small networks, but does not scale well. When using static routing, the routing tables on each router must be updated each time the network topology changes -- such as when a network link fails..

In most networks, routing is managed automatically through the use of dynamic routing. In dynamic routing, routing protocols create and maintain the routing tables automatically. Dynamic routing responds much more quickly to network changes (and network failures) than static routing.