Interior Gateway Routing Protocol

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Interior Gateway Routing Protocol (IGRP) is a kind of IGP which is a proprietary distance-vector routing protocol invented by Cisco, used by routers to exchange routing data within an autonomous system.

IGRP was created in part to overcome the limitations of RIP (maximum hop count of only 15, and a single routing metric) when used within large networks. IGRP supports multiple metrics for each route, including bandwidth, load, delay, mtu, and reliability; to compare two routes these metrics are combined together into a single metric, using a formula which can be adjusted through the use of pre-set constants. The maximum hop count of IGRP-routed packets is 255.

IGRP is considered a classful routing protocol. As the protocol has no field for a subnet mask the router assumes that all interface addresses have the same subnet mask as the router itself. This contrasts with classless routing protocols that can use variable length subnet masks. Classful protocols have become less popular as they are wasteful of ip address space.

Its successor is EIGRP, that adds Diffusing Update Algorithm (DUAL) ideas to the basic distance-vector mechanism of IGRP.de:Interior Gateway Routing Protocol es:IGRP fr:Interior Gateway Routing Protocol it:Interior Gateway Routing Protocol he:Interior Gateway Routing Protocol pl:IGRP pt:Interior Gateway Routing Protocol sv:Interior Gateway Routing Protocol