IP Routing Protocols

IGRP

Let us start with IGRP. First, it is similar to RIP in that it is a distance-vector protocol. However, IGRP uses more elaborate metrics than a simple hop count. IGRP advertises three types of routes, as shown in Figure 8-1.

Figure 8-1. Types of Routes

Interior routes are routes between subnets in a network attached to a router. The network must be subnetted, otherwise, IGRP will not advertise the interior routes. System routes are routes within an autonomous system. System routes do not include subnet information. Exterior routes are routes to networks outside the autonomous system and are called a gateway of last resort. IGRP provides ...