Interior Gateway Routing Protocol

Interior Gateway Routing Protocol
Interior Gateway Routing Protocol (IGRP)
was developed by Cisco in the mid-1980s to overcome
the distance limitations of the Routing Information Protocol (RIP). Instead of using the
hop count metric like RIP, IGRP uses a composite metric to overcome the distance limitations
of RIPv1. The composite metric is made up of the following four elements; by default, only
bandwidth and delay are used:

Bandwidth

Delay
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Load

Reliability
Maximum transmission unit (MTU) information is included in routing updates
but cannot be configured to be part of the composite metric.
IGRP does not use hop count as a variable in the composite metric; it does, however, track
hop count. IGRP can traverse 100 hops but can be configured to accommodate up to 255 hops.
Although IGRP does overcome the distance limitations of RIP, it still has its own limitations.
IGRP is a Cisco-proprietary routing protocol. This means IGRP cannot be used with other vendors’
products. The other limitation is that IGRP is a classful distance-vector routing protocol,
which means it doesn’t scale well for large internetworks.
In the next few sections, we will explore how IGRP operates and how to implement IGRP in
an internetwork.
While RIP depends on UDP for transport, utilizing port 520, IGRP, EIGRP, and
OSPF interface with the Internet