Meaning – The term interior gateway, refers to a gateway that communicates only with its own autonomous system. They communicate with each other using the Routing Information Protocol (RIP), Routing Information Protocol Next Generation (RIPng), Intermediate System to Intermediate System protocol, Open Shortest Path First (OSPF) protocol, or the HELLO Protocol (HELLO).
Example of usage – “Consider two autonomous systems. The first is all the networks administered by the Widget Company. The second is all the networks administered by the Gadget Company. The Widget Company has one machine, called apple, which is Widget’s gateway to the Internet. The Gadget Company has one machine, called orange, which is Gadget’s gateway to the Internet. Both companies have several different networks internal to the companies. The gateways connecting the internal networks are interior gateways. But apple and orange are exterior gateways.”