Chapter 16. A dynamic routing protocols crash course
In the last chapter, you had to manually configure static routes to enable IP connectivity throughout your network. In this chapter, you’re going to automate this process by configuring two of the most popular dynamic routing protocols: Cisco’s very own Enhanced Interior Gateway Routing Protocol (EIGRP) and Open Shortest Path First (OSPF). But before you learn how these two protocols work and how to configure them, it helps to understand why they exist in the first place.
Network nerds sometimes refer to dynamic routing protocols as interior gateway protocols (IGPs). For brevity, I’ll use this acronym throughout the rest of the chapter. IGPs automate the process of advertising subnets to other routers in the network. Although this may not sound particularly exciting, it can save you a lot of work.
IGPs do other things as well. If there are multiple paths or routes to a subnet, an IGP will choose the best one—the best usually being the shortest and fastest path. An IGP can also automatically route around link failures if another path is available. The downside to IGPs is that they’re more complicated to configure, as you’ll find out in this chapter.
To illustrate these features, you’ll be configuring the topology shown in figure 16.1.
