IGRP / IGRP features

IGRP

IGRP features

7.3.1 This page will explain the main features and functions of IGRP.

IGRP is a distance vector IGP. Distance vector routing protocols measure distances to mathematically compare routes. This measurement is known as the distance vector. Routers that use distance vector protocols must send all or a portion of their routing table in a routing update message at regular intervals to each neighbor router. As routing information spreads throughout the network, routers perform the following functions:

• Identify new destinations

• Learn of failures

IGRP is a distance vector routing protocol developed by Cisco. IGRP sends routing updates at 90 second intervals. These updates advertise all the networks for a particular AS. Key design characteristics of IGRP are a follows:

• The versatility to automatically handle indefinite, complex topologies

• The flexibility needed to segment with different bandwidth and delay characteristics

• Scalability for functioning in very large networks

By default, the IGRP routing protocol uses bandwidth and delay as metrics. Additionally, IGRP can be configured to use a combination of variables to determine a composite metric. These variables are as follows:

• Bandwidth
• Delay
• Load
• Reliability

The next page will introduce the IGRP metrics.