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IGP versus EGP

IGP versus EGP
6.3.4
This page will help students understand the differences between interior and exterior routing protocols.
Interior routing protocols are designed for use in a network that is controlled by a single organization. The design criteria for an interior routing protocol require it to find the best path through the network. In other words, the metric and how that metric is used is the most important element in an interior routing protocol.
An exterior routing protocol is designed for use between two different networks that are under the control of two different organizations. These are typically used between ISPs or between a company and an ISP. For example, a company would run BGP, an exterior routing protocol, between one of its routers and a router inside an ISP. IP exterior gateway protocols require the following three sets of information before routing can begin:
  • A list of neighbor routers with which to exchange routing information
  • A list of networks to advertise as directly reachable
  • The autonomous system number of the local router
An exterior routing protocol must isolate autonomous systems. Remember, autonomous systems are managed by different administrations. Networks must have a protocol to communicate between these different systems.
Each AS must have a 16-bit identification number, which is assigned by ARIN or a provider, to use routing protocols such as IGRP and EIGRP.
The Interactive Media Activity will help students identify interior and exterior routing protocols.
This page concludes this lesson. The next page will summarize the main points from this module.

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