EIGRP protocol: Basic concept and its configuration
Introduction
EIGRP is an important topic of Cisco exam certification. EIGRP stands for enhanced interior gateway routing protocol. We use it for finding the best path in the computer internetwork. It works on Cisco devices, but a few years ago, Cisco declared it standardized as open. EIGRP protocol is a successor of IGRP.
It is a hybrid routing protocol. Moreover, It has the features of both distance vector and link-state routing protocols. So, hybrid routing protocol, or advanced distance vector routing protocol.
How does EIGRP work?
EIGRP routers start their work by discovering their neighbor after its configuration. It sends hello messages to each other via multicast IP address 224.0.0.10, where they will meet each other. When the EIGRP-speaking router receives hello messages via multicast address, it finds that another router wants its neighbor. After receiving a hello message from the speaking router, it checks some parameters to become its neighbor. It uses the DUAL algorithm to reach its destination. The DUAL algorithm uses different parameters as its metric: bandwidth, delay, reliability, and load. Based on these metrics, it calculates its best path to reach its destination. EIGRP metric is called composite metric because it uses different parameters to reach its destination. When two EIGRP-speaking routers want to communicate with each other for the first time, then it checks the following parameters for its neighbor adjacency.
- Authentication
- A.S number
- Subnet mask
- K values
Features of EIGRP Protocol
It has various features which make it unique from other routing protocols.
Backup Route
EIGRP router has primary routes as well as backup routes. Based on the backup route, EIGRP has the fastest convergence time.
Load Balancing
It provides the feature of load balancing so that we can do equal cost and unequal cost load balancing. equal cost and unequal cost means, that we can send same as well as different traffic on the links.
Summarization
EIGRP has the feature of summarization, so we can summarize routes on every router and on the interface level.
Supported Routed protocol
It doesn’t provide communication only to the IP address, but we can configure it for Apple Talk, novel IPX, etc.
Fast Convergence
If some EIGRP route goes down due to some reason, then it transfers its load to an alternative path very quickly.
EIGRP Protocol lab topology
In this lab, we will configure EIGRP on two routers which are R2 and R2. R1 is directly connected with R2. Each router has its own LAN, on which one PC is connected directly to the router. Configure IP addresses as given below in the image.
Check the routing table of both the routers.
Running EIGRP on both the routers with Autonomous system number 1.
Show the routing table of both the routers.
As highlighted in the screenshot, D denotes the DUAL algorithm, which indicates that this route has been reached via EIGRP.
The next phase is to check the EIGRP neighbor table. The neighbor table is a data structure that stores information on EIGRP directly connected routers.
Check the running protocol on the router.
