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Embed code for: 23.2 Overview of Routing Protocols
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23.2 Overview of Routing Protocols
Overview of Routing Protocols Section 23: Implementing Dynamic Routing Routing is the process of determining where to send the data packets that are destined for addresses that are outside the local network. Routers gather and maintain routing information that can enable the transmission and receipt of these data packets. Routing information takes the form of entries in a routing table, with one entry for each identified route. The router can use a routing protocol to create and maintain the routing table dynamically so that network changes can be accommodated whenever they occur. To manage an IP network effectively, you must understand the operation of static versus dynamic routing protocols and the impact that they have on an IP network. Routers can forward packets over static routes or dynamic routes, based on the router configuration. There are two ways to tell the router how to forward packets to networks that are not directly connected. Static The router learns routes when an administrator manually configures the static route. The administrator must manually update this static route entry whenever an internetwork topology change requires an update. Static routes are userdefined routes that specify the path that packets take when they move between a source and a destination. These administratordefined routes enable precise control over the routing behavior of the IP internetwork. Dynamic The router dynamically learns routes after an administrator configures a routing protocol that helps determine routes. Unlike the situation with static routes, after the network administrator enables dynamic routing, the routing process automatically updates route knowledge whenever new topology information is received. The router learns and maintains routes to the remote destinations by exchanging routing updates with other routers in the internetwork. Dynamic routing relies on a routing protocol to provide knowledge. A routing protocol defines the rules that a router uses when it communicates with neighboring routers to determine the paths to remote networks, and the protocol maintains those networks in the routing tables. The figure illustrates that a router in the network can have knowledge of networks that are not directly connected to an interface on that device. These routes must be configured statically or learned via routing protocols. The goals of a routing protocol include the following: Discovering remote networks: There is no need to manually define the available destination (routes). The routing protocol discovers remote networks and updates the internal routing table of the router. Maintaining uptodate routing information: The routing table contains entries about remote networks. When changes happen in the network, routing tables are automatically updated. Choosing the best path to destination networks: Routing protocols discover remote networks. More paths to the destinations are possible, and the best paths enter the routing table. Finding a new best path if the current path is no longer available: The routing table is constantly updated, and new paths may also be added. When the current best path is not available or better paths are found, the routing protocol selects a new best path. Up Next: Routed Protocol Versus Routing Protocol