Cisco Systems CCNA 2 manual Dynamic Routing Overview, Introduction to routing protocols

6.2 Dynamic Routing Overview

Essential Labs:	None
Optional Labs:	None
Core TIs:	All
Optional TIs:	none

Course-Level Claim: Students can evaluate the characteristics of routing protocols.

Certification-Level Claim: Students can evaluate the characteristics of routing protocols.

Hands-on skills: none

6.2.1 Introduction to routing protocols

A routing protocol is a type of communication that is used between routers. A routing protocol allows one router to share information with other routers such as known networks and how close they are to the router. The information a router gets from another router through the routing protocol is used to build and maintain a routing table.

A routed protocol is used to direct user traffic. A routed protocol is a network protocol that provides enough information in its network layer address to allow a packet to be forwarded from one host to another host based on the addressing scheme. The Internet Protocol (IP) is an example of a routed protocol. Students should know the difference between a routed and routing protocol at the end of this TI. Identify the location of each protocol in the OSI model. Ask students the following questions:

•TCP is at which layer?

•IP is at which layer?

•Is the protocol connection-oriented or connectionless?

•RIP, IGRP, EIGRP, and OSPF are at which layer and what is the administrative distance of each?

6.2.2Autonomous systems

An autonomous system is a collection of networks under a common administration that share a common routing strategy. Some routing protocols use an autonomous system to communicate routing information. The routers are configured with the routing protocol and the autonomous system number. Each router can only communicate with other routers within the same autonomous system.

To demonstrate this concept, divide the classroom into groups and tell the students they can only talk to the people in their group. This is similar to a protocol that uses autonomous system numbers. It is possible for routers with different autonomous system numbers and different protocols to communicate if redistribution is used. Redistribution will not be covered in this section.

69 - 238 CCNA 2: Routers and Routing Basics v3.1 Instructor Guide – Module 6 Copyright ♥ 2004, Cisco Systems, Inc.