Routing Protocols

Used to allow cooperating routers to exchange information about routes they know.

Allow routers (and hosts) to advertise info of the type "I can reach network AAA.BBB.CCC.DDD at a price of X".

When a router receives such information, it might update its routing table, so that its "next hop" to each network AAA.BBB.CCC.DDD will be the advertising router.

Normally, each routing protocol also allows the administrator to inject routes not learned via that given protocol (either routes defined statically or routes learned via different routing protocols).