Little about Interior Gateway Routing Protocol (IGRP)

by Nideesh C on January 30, 2011 · 0 comments

in Networking




The Interior Gateway Routing Protocol, or IGRP, is a networking routing protocol that is designed to enable routing inside of an autonomous system or AS. The protocol was developed by Cisco in the later 1980s in response to shortcomings found with the existing Routing Information Protocol (RIP) when scaled to medium or large-sized networks. As Cisco routers became more popular, IGRP began to be used by a number of large networks and was later replaced by the enhanced, ITRP in the early 1990s in order to improve the overall efficiency of network routing.

How Does the Interior Gateway Routing Protocol Work?

The Interior Gateway Routing Protocol is labeled a distance vector protocol and uses a mathematical comparison of network traffic routes to calculate a measure of distance required to travel. The protocol is similar to a link-state routing protocol that transmits connection information to all note in the network. The IGRP supports multipath routing when calculating network distances and directing traffic on a network. The protocol will automatically choose the network path that is calculated to be most efficient or the shortest path. If this path goes down, it will automatically change to the alternative path that will successfully delivery the network packet to the desired destination. The network administrator can also implement a variance to use in network calculations to tweak the paths used for traffic delivery.

What is the Interior Gateway Routing Protocol Structure?

There are eight components in the Interior Gateway Routing Protocol structure. These components include the version, the opcode that indicates if it is an update or request message type, the edition of the packet which is the serial number that is incremented when there is a modification or change to the routing table, an autonomous system number which is where a gateway can be involved in more than one system with each running its own IGRP, and the Ninterior, Nsystem, and Nexterior entries followed by the checksum.

How was IGRP Improved with the Enhanced Protocol?

The Enhanced Interior Gateway Protocol improves on the IGRP by keeping a copy of its neighbor’s routing tables. If it cannot find a route to a desired destination, then the protocol will ask neighboring routers to query their neighbor’s to find a successful path to the desired destination of the network traffic. When router tables are modified or changed, the neighbor’s are then notified and the protocol uses the Diffusing-Update Algorithm (DUAL) to determine the least cost route in a more efficient manner than the legacy IGRP.

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