In a real-world scenario, networks under the same administration are generally scattered geographically. There may exist a requirement of connecting two different networks of the same kind as well as of different kinds. Routing between two networks is called internetworking.
Networks can be considered different based on various parameters such as, Protocol, topology, Layer-2 network and addressing scheme.
In internetworking, routers have knowledge of each other’s addresses and address beyond them. They can be statically configured go on different networks or they can learn by using an internetworking routing protocol.
Routing protocols that are used within an organization or administration are called Interior Gateway Protocols or IGP. RIP, OSPF are examples of IGP. Routing between different organizations or administrations may have Exterior Gateway Protocol, and there is only one EGP i.e. Border Gateway Protocol.
