Chapter 8: Routing Protocols

CCDA Topics Covered in this Chapter:

• Given a network design or a set of requirements evaluate a solution that meets routing protocol needs.

Who doesn’t like their car to run at its optimum? When the motor is tuned and purring like a cat, life is good. But when the engine sounds as if it’s coughing up hairballs, doesn’t turn over in the morning, or worse yet, stalls in the middle of an intersection, we all get pretty cranky.

You’re probably thinking, where is he going with this and how does it relate to routing protocols? Well, routing protocols compose the information (engine) for getting messages back and forth across networks. Knowing these processes is like knowing your car’s engine: it will help you troubleshoot any problems that occur and obtain peak performance from your systems.

Routing protocols are responsible for the exchange of IP address information on enterprise, intranet, and Internet networks. The information shared by routers enables two separate end systems to find a path from one to another, thus establishing communication. As discussed in Chapter 5, “Designing Network Topologies,” IP addressing schemes establish a hierarchy that makes path information both distinct and efficient. Routers receive route information via a given interface and then advertise that information out their other physical interfaces. The routing process occurs on Layer 3 of the OSI model.

This chapter will discuss each of the following routing protocols:

• RIP (Routing Information Protocol)

• IGRP (Internal Gateway Routing Protocol)

• EIGRP (Enhanced Internal Gateway Routing Protocol)

Each routing protocol is distinct in the way it functions. However, most routing protocols are one of two major types: link-state or distance-vector. We’ll discuss each type’s features and differences at the beginning of this chapter, because understanding how each protocol functions is a very important part of being able to troubleshoot a routing problem. Once you understand how a protocol calculates a route, you can fine-tune the protocol with configuration changes to make it perform at peak efficiency.

Note

OSPF, IS-IS, and NLSP are covered in Chapter 9, “Link-State and Bridging Protocols.”

Cisco routers implement several different protocols—some are Cisco proprietary, and others are open standard. The proprietary protocols discussed in this chapter are IGRP and Enhanced IGRP.

Okay, let’s get started learning how that engine is supposed to hum.