Interior Gateway Protcol (IGP) 1/6: Introduction

This is the first post in a 6 part series covering various interior gateway protocols(IGP). Over the next 6 posts we will touch on the most used routing protocols and their pros and cons. The goal is to help you better understand routing and allow you to pick the protocol that is best suited to your network.

 

First of all, what is an interior gateway protocol(IGP)?

 

IGP is a routing protocol used to exchange data between nodes within an autonomous system.

 

Interior gateway protocols fall under 2 categories. Distance-vector routing protocol and Link-state routing protocol.


Distance-vector routing protocol

 

In distance-vector routing protocols, routers do not have information about a network topology in it’s entirety. Routers only have the details of the neighboring routers and they rely on those routers to route packets efficiently based on their neighbors. Distance-vector protocols use the Bellman-Ford algorithm to determine the best route.

 

The 3 distance-vector routing protocols we will be going over the next few posts are as follows:


  • Routing Information Protocol (RIP)
  • Interior Gateway Routing Protocol (IGRP)
  • Enhanced Interior Gateway Routing Protocol (EIGRP)


Link-state routing protocol

 

Opposite of distance-vector protocols, link-state protocols contain information about the entire network topology. Each individual router is able to calculate the best route using the information contained in their local routing table.

 

The 2 link-state protocols we will look at are as follows:

 

  • Open Shortest Path First (OSPF)
  • Intermediate System to Intermediate System (IS-IS)