Exterior gateway protocol

An exterior gateway protocol is an IP routing protocol used to exchange routing information between autonomous [system (Internet)|autonomous systems]. This exchange is crucial for communications across the Internet. Notable exterior gateway protocols include Exterior Gateway Protocol, now obsolete, and Border Gateway Protocol.
By contrast, an interior gateway protocol is a type of protocol used for exchanging routing information between gateways within an autonomous system. This routing information can then be used to route network-level protocols like IP.