Cisco Systems 78-11741-02 manual Configuring Eigrp, Cisco Eigrp Implementation, IPC-257

Configuring EIGRP

This chapter describes how to configure Enhanced Interior Gateway Routing Protocol (EIGRP). For a complete description of the EIGRP commands listed in this chapter, refer to the “EIGRP Commands” chapter of the Cisco IOS IP Command Reference, Volume 2 of 3: Routing Protocols publication. To locate documentation of other commands that appear in this chapter, use the command reference master index, or search online.

Refer to the Cisco IOS AppleTalk and Novell IPX Configuration Guide for information on AppleTalk EIGRP or Internetwork Packet Exchange (IPX) EIGRP.

For protocol-independent features that work with EIGRP, see the chapter “Configuring IP Routing Protocol-Independent Features” in this document.

EIGRP is an enhanced version of the IGRP developed by Cisco. EIGRP uses the same distance vector algorithm and distance information as IGRP. However, the convergence properties and the operating efficiency of EIGRP have improved substantially over IGRP.

The convergence technology is based on research conducted at SRI International and employs an algorithm referred to as the Diffusing Update Algorithm (DUAL). This algorithm guarantees loop-free operation at every instant throughout a route computation and allows all devices involved in a topology change to synchronize at the same time. Routers that are not affected by topology changes are not involved in recomputations. The convergence time with DUAL rivals that of any other existing routing protocol.

To identify the hardware platform or software image information associated with a feature, use the Feature Navigator on Cisco.com to search for information about the feature or refer to the software release notes for a specific release. For more information, see the “Identifying Supported Platforms” section in the “Using Cisco IOS Software” chapter in this book.

The Cisco EIGRP Implementation

EIGRP provides the following features:

•Automatic redistribution—IGRP routes can be automatically redistributed into EIGRP, and EIGRP routes can be automatically redistributed into IGRP. If desired, you can turn off redistribution. You can also completely turn off EIGRP and IGRP on the router or on individual interfaces.

•Increased network width—With IP Routing Information Protocol (RIP), the largest possible width of your network is 15 hops. When EIGRP is enabled, the largest possible width is increased to 100 hops, and the metric is large enough to support thousands of hops.

Cisco IOS IP Configuration Guide

IPC-257