Understanding Cisco distance vector routing protocol.

In Cisco carrier, the concept of distance Vector protocols are the simplest among Routing Protocols. Distance vector routing protocols use the distance and direction (vector) to find paths to destinations.

A router which is running a Distance Vector routing protocol informs its neighbors about the network topology changes periodically, using limited broadcasts using destination IP address 255.255.255.255.

Distance Vector protocols use the Bellman-Ford algorithm for finding best paths to destinations.

Routers running Distance Vector protocols learn who their neighbors are by listening for routing broadcasts on their interfaces. Distance Vector protocols periodically send local limited broadcasts (255.255.255.255) to share routing information.

Distance Vector algorithms pass routing table updates to their immediate neighbors in all directions. At each exchange, the router increments the distance value received for a route, thereby applying its own distance value to it. The router who received this update again pass the updated table further outward, where receiving routers repeat the process.

The Distance Vector protocols do not check who is listening to the updates which they sent and Distance Vector protocols broadcast the updates periodically even if there is no change in the network topology.

Distance Vector protocols are the simplest among three types of dynamic routing protocols. They are easy to set-up and troubleshoot. They require less router resources. They receive the routing update, increment the metric, compare the result to the routes in the routing table, and update the routing table if necessary.

Examples of Distance Vector Routing protocols are Routing Information Protocol Version 1 (RIPv1) and Interior Gateway Routing Protocol (IGRP).

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