Interior Gateway Protocol (IGP)

IGP, or Interior Gateway Protocol, is a type of routing protocol used for distributing routing information within autonomous systems in large internetworks based on the TCP/IP protocol.

What is IGP (Interior Gateway Protocol)?

A type of routing protocol used for distributing routing information within autonomous systems in large internetworks based on the TCP/IP protocol (such as the Internet).

How it works

Interior Gateway Protocols (IGPs) specify how routers within an autonomous system (AS) exchange routing information with other routers within the same autonomous system. This is in contrast to Exterior Gateway Protocols (EGPs), which facilitate the exchange of routing information between different autonomous systems.

Examples of IGPs for TCP/IP internetworks include the following:

  • Routing Information Protocol (RIP) for Internet Protocol (IP), which is based on the distance-vector algorithm. RIP is a popular protocol for small to medium-sized internetworks.
  • Open Shortest Path First (OSPF) Protocol, which is based on the link-state algorithm. OSPF is used mainly on medium to large-sized internetworks.
  • Interior Gateway Routing Protocol (IGRP), a distance-vector protocol developed by Cisco Systems.

Graphic I-7. A network using IGP to route information within an autonomous system and EGP to route information between autonomous systems.

NOTE

Microsoft Windows NT version 4 with the Routing and Remote Access Service (RRAS) installed and Windows 2000 with Routing and Remote Access installed support RIP for IP and for OSPF.