Routing Protocol Basics
Distance Vector Routing Protocols
Link State Routing Protocols
Interior and Exterior Gateway Protocols
Static or Dynamic Routing?
The last chapter explained what a router needs to know to correctly switch packets to their respective
destinations and how that information is put into the route table manually. This chapter shows how
routers can discover this information automatically and share that information with other routers via
dynamic routing protocols. A routing protocol is the language a router speaks with other routers in order
to share information about the reachability and status of networks.
Dynamic routing protocols not only perform these path determination and route table update functions but
also determine the next-best path if the best path to a destination becomes unusable. The capability to
compensate for topology changes is the most important advantage dynamic routing offers over static
routing.
Obviously, for communications to occur the communicators must speak the same language. There are
eight major IP routing protocols from which to choose; if one router speaks RIP and another speaks
OSPF, they cannot share routing information because they are not speaking the same language.
Subsequent chapters examine all the IP routing protocols in current use, and even consider how to make a
router "bilingual," but first it is necessary to explore some characteristics and issues common to all
routing protocols—IP or otherwise.