Interior Gateway Routing Protocol (IGRP): IGRP is a distance-vector Interior Gateway Protocol (IGP) developed by Cisco. It is used by routers to exchange routing data within an autonomous system. IGRP is a proprietary protocol. IGRP was created in order to overcome the limitation of RIP (maximum hop count of only 15, and a single routing metric) when used within large networks. IGRP supports multiple metrics for each router, including bandwidth, delay, load, and reliability to compare two routes their metrics are combined together into a single metric, using a formula which can be adjusted through the use of pre-set constants. By default, the IGRP composite metric is a sum of the segment delays and the lowest segment bandwidth. The maximum configuration hop count of IGRP routed packets is 255 (default 100), and routing updates are broadcast every 90 seconds by default. IGRP uses protocol number 9 for communication. IGRP is considered a classful routing protocol. Classful protocols have become less popular as they are wasteful of IP address space.
Autonomous System: An autonomous system (AS) is a network or a collection of networks that are all managed and supervised by a single entity or organization. An AS is also sometimes referred to as a routing domain. An AS is assigned a globally unique number, sometimes called an Autonomous System Number (ASN). Autonomous System numbers range from 1 to 65,535.
Table of Contents
IGRP timers
Update timer: it specifies the interval between the routing update message. The default is 90 seconds.
Invalid timers: it specifies how long a router should wait before declaring a route invalid if it doesn’t receive a specific update about it. The default is three times the update period i.e. 270 seconds.
Hold-down timers: the default is three times the update timer period plus 10 seconds i.e. 280 seconds.
Flush timer: there indicates how much time should pass before a route should be flushed from the routing table. The default is seven times the routing update period. If the update timer is 90 seconds by default the 7 x 90 = 630 seconds.
5 Topologies that are used in today’s world!
Syntax
Router(config)# router IGRP <autonomous system no.>
Router(config-router)# network x.x.x.x
Router(config-router)# network x.x.x.x
Configure for the IGRP on Router A is:
Router(config)# router IGRP 10
Router(config-router)# network 192.168.1.0
Router(config-router)# network 192.168.2.0
<==Access CCNA LAB’s for Free==>
Learn English with Hindi, Marathi, Urdu translation
Earn Money with Affiliate Marketing – Download 10+ eBooks
