IP Routing Protocols

EIGRP

EIGRP has all the features of IGRP, and supports route aggregation with CIDR prefixes. It also has improved operations to ensure loop-free paths during network changes. It also adds Hello messages, sequencing, and reliable transport operations.

Cisco routers use an administrative distance to assign a rating to routing information. Each method of route discovery is assigned a value, which identifies each specific method. The range of values is 0 to 255, with the smaller numbers being more trusted route discovery methods.

Table 8-2 shows the administrative default distances for the various methods of finding a route. Most of the entries pertain to routing protocols, the others are about manually configured static routes, and routes found ...