A protocol that enables the exchange of routing tables between routers in an internetwork. Routing protocols are the software implementation of specific routing algorithms, which are mathematical procedures for determining the cost of various paths or routes through an internetwork so that traffic can be routed most efficiently.
Routing protocols are generally implemented in medium to large-sized TCP/IP internetworks to simplify the administration of routing tables. Common routing protocols include the following:
Dynamic routers talk to each other using routing protocols and are essentially self-configuring (except for the first one installed in an internetwork). Static routers do not talk to each other and must be configured independently.
Remember that a routing protocol is different from a routable protocol. A routing protocol is used by routers to communicate with each other. A routable protocol, on the other hand, is a network protocol such as TCP/IP or IPX/SPX that can be routed between networks within an internetwork.