Routing protocols determine the best path packets take to reach a destination in a network. A routing protocol does this by defining rules to communicate with neighboring routings and then sending information about the router's learned routes to neighboring routers. Routing protocols are divided into two classes based on how they interact with other autonomous systems: exterior gateway protocols (EGP) and interior gateway protocols (IGP).
An autonomous system (AS) refers to a group of networks under a common administrative domain.
IGPs exchange information within an AS. Examples include RIP, EIGRP, OSPF, and IS-IS.
EGPs exchange information between autonomous systems. BGP is ...