Deep understanding of Distance Vector Routing Protocol

In the age of the Internet, we often encounter problems with the distance vector routing protocol. Next we will introduce the knowledge about the distance vector routing protocol, including how to determine the adjacent router to your network.

Why is it important to determine the adjacent router?

Determining the adjacent router in a small network is not a major problem. When a router fails, other routers can converge within an acceptable period of time. However, in a large network, the latency of a faulty router may be high. Knowing that the adjacent router can accelerate convergence, because the router can know the faulty router more quickly, because the interval of hello messages is shorter than the interval of router information exchange.

When a router using the distance vector routing protocol does not send route update information to the adjacent router, it can be found that the adjacent router is no longer reachable. This time is generally 10 ~ 90 seconds. The router that uses the link status routing protocol does not receive the hello message, it can be found that the adjacent router is not reachable, this interval is generally 10 seconds.

How can I find the adjacent router through distance vector routing protocol and link status routing protocol?

A Router using the Distance Vector Routing Protocol needs to create a route table, including the network directly connected to it), and it will send the route table to the router directly connected to it. The adjacent router combines the received route table into its own route table, and also sends its route table to its adjacent router.

A connection status table is created for the router that uses the link status routing protocol, including the list of the entire network destination site. In the UPDATE message, Each router sends its entire list. When the adjacent router receives the update packet, it copies the content and sends the information to its neighbor. It is not necessary to recalculate the content of the route table.

Note that the hello message is broadcast by the routers of IGRP and VPN to discover the adjacent station and exchange route update information like OSPF. For each network layer protocol, it includes the address of the neighboring station, the number of packets waiting to be sent in the queue, and the average time required to receive or send packets to the neighboring station, and the time when no message is received from the neighboring station before the link is confirmed to be disconnected.