Purpose of Routing
Routes are created to allow nodes to communicate data packets across networks. In order to route data packets to their destination, they travel along a series of links, each link having a single direction (one-way). A link is formed by joining two adjacent routers together; the router at either end of a link is called the ingress or egress router.
The purpose of routing is to find the best path between two points. Routers exchange information about what routes exist between them using standard protocols. When a packet of data arrives at a router, the router will examine its header to determine where it should send the packet. If the router does not know how to reach the specified destination address, it sends the message to an adjacent router via a neighboring node. Each router stores a table of addresses it knows about. These tables are known as routing tables.