Chapter 4. Addressing, Neighbor Discovery, and Adjacencies

Finally, after three chapters, we leave concepts and generalities behind and begin examining the mechanics of the two protocols. The best place to begin is where the protocols themselves begin, which is to look at what they do when they first start up. First, the protocol must discover essential information about itself and the router it is running on, such as router IDs, area configurations, interface parameters, and the links the interfaces are connected to. Next, neighbors must be discovered; a routing protocol is not much good if it has no one to talk to. And with the discovery of neighbors, adjacencies must be established, so that the protocols know what to talk about.