Chapter 4. Interior Gateway Protocols and Migration Strategies

This chapter reviews key concepts and characteristics of Interior Gateway Protocols (IGPs) commonly deployed in enterprise networks. It starts with a brief description of the three most common enterprise IGPs and provides examples of IGP configuration and operational analysis in a JUNOS software environment. The chapter also discusses current best practices to minimize network disruption when migrating from one IGP to another, with configuration examples for Routing Information Protocol to Open Shortest Path First (RIP to OSPF) and Enhanced Interior Gateway Routing Protocol to OSPF (EIGRP to OSPF) migration. The topics discussed in this chapter include:

  • IGP overview

  • RIP deployment case study

  • IGP migration

  • RIP to OSPF migration case study

  • EIGRP migration case study

From an IGP perspective, a Juniper Networks router supports RIP, the OSPF protocol, and the Intermediate System-to-Intermediate System (IS-IS) routing protocols. This chapter does not address IS-IS given that it is normally seen in service provider networks and rarely is found in the enterprise.

It should be noted that Juniper Networks routers do not support the Cisco Systems proprietary Interior Gateway Routing Protocol (IGRP), or the updated version known as EIGRP. Technical merits aside, licensing restrictions combined with the closed nature of these protocols prevent Juniper Networks from implementing either of these IGPs. Given that IGRP/EIGRP was commonly deployed in many small to medium-size enterprises, a large portion of this chapter focuses on migration strategies designed to ease such a transition between the two vendors.

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