EIGRP Basic Knowledge

First, Introduction

Multiple EIGRP process domains are not able to communicate with each other

Distance vector routing protocol based on Bellman-fore algorithm, its disadvantage: easy to generate routing loop, counting to infinity

Measures to avoid loops by distance vector Routing protocol: Horizontal segmentation, toxicity reversal and suppression timer

EIGRP is a class-free routing protocol that supports VLSM and CIDR

Second, the basic principle and realization

EIGRP contains four components: protocol-dependent modules, reliable transfer protocols, neighbor Discovery and recovery, and diffusion update algorithms

EIGRP-supported protocols: IP, IPX, AppleTalk, if IP eigrp processes and IGRP processes are within the same autonomous system, they are automatically reassigned

1. Reliable Transfer Protocol (TRP): A Transport layer protocol that ensures that EIGRP packets are sent in the order of all neighbors. Used to manage the sending and receiving of EIGRP packets. Reliability means that the sending is guaranteed, and the packet is sent in an orderly manner. In order to send is in each packet contains two serial numbers EIGRP use the multicast address is: 224.0.0.10 eigrp maximum hop limit to 224,igrp maximum hop limit of 255

EIGRP encapsulated in IP packet, protocol number 88

Type of EIGRP Package

2. Neighbor Discovery and recovery

EIGRP's neighbor discovery mechanism allows routers to dynamically learn about other routers in their directly connected networks, and to detect neighbors unreachable or not running properly through the Hello packet.

Through the hello package to achieve, Hello packet transmission frequency is divided into two kinds, one is 5 s, the other is 60S, how to distinguish? Hello grouping on T1 or lower-speed multicast interfaces, sending a Hello packet per 60S, on LAN and other serial interfaces, when bandwidth is greater than T1 ( 1.544M), send hello once per 5 s.

Modify Hello times and hold Time

Hello:ip Hello interval eigrp {as number} {time}

Hold:ip hold-time EIGRP {as number} {time}

3. Diffusion update algorithm: is a convergence algorithm, refers to to be able to break the routing loop at any time, and the use of diffusion update calculation to carry out a distributed shortest path route selection.

Dual has built-in decision processes to perform all routing calculations, tracking all the routes of all neighbor advertisements, and selecting a loop-efficient path to destinations based on measures.