AIS AI2524 user manual Igrp Updates, Igrp Configuration Task List

Chapter 8: AI2524 Protocol Configuration Steps

AI2524 IGRP

TCP/IP

Configuration

Steps

The Interior Gateway Routing Protocol (IGRP) is a dynamic distance- vector routing protocol for an autonomous system that contains large, arbitrarily complex networks with diverse bandwidth and delay char- acteristics.

IGRP uses a combination of user-configurable metrics, including in ternetwork delay, bandwidth, reliability, and load.

IGRP Updates

By default, a router running IGRP sends an update broadcast every 90 seconds. It declares a route inaccessible if it does not receive an update from the first router in the route within 3 update periods (270 seconds). After 7 update periods (630 seconds), the Cisco IOS software removes the route from the routing table.

IGRP uses flash update and poison reverse updates to speed up th convergence of the routing algorithm. Flash updates are sent soone than the standard periodic update for notifying other routers of a metric change. Poison reverse updates are intended to defeat larger routing loops caused by increases in routing metrics. The poison reverse up- dates are sent to remove a route and place it in holddown, which keeps new routing information from being used for a certain period of time.

IGRP Configuration Task List

To configure IGRP, perform the tasks outlined in the next section. Cre- ating the IGRP routing process is mandatory; the other tasks are op tional.

zCreate the IGRP Routing Process

zAllow Point-to-Point Updates for IGRP

zDefine Unequal-Cost Load Balancing

zControl Traffic Distribution

zAdjust the IGRP Metric Weights

zDisable Holddown

zEnforce a Maximum Network Diamete

zValidate Source IP Addresses

August 1997	Page 8-11
2524UM