Router knowledge points: understand the practical application of router protocols

All users who use routing know that the router protocol is a very important part. Many people may not know what to pay attention to in the actual application of the router protocol, after reading this article, you must have gained a lot. I hope this article will teach you more things.

1. When will I use the multi-Router Protocol? When two different routing protocols need to exchange routing information, the multi-Router Protocol is required. Of course, route redistribution can also exchange route information. In the following cases, you do not need to use the multi-route protocol: update the old version of the Internal Gateway Protocol (IGP) to the new version of IGP.

To use another vro protocol, you must retain the original one. You want to terminate the internal route to avoid interference from other routers that do not strictly filter the monitoring function. You are in an environment composed of routers from multiple manufacturers.

2. What is distance vector Router Protocol? The Distance Vector Router Protocol is designed for a small network environment. In a large network environment, such protocols will generate large traffic when learning routes and maintaining routes, occupying excessive bandwidth. If the route selection table update is not received from the adjacent site within 90 seconds, the adjacent site is considered inaccessible. Every 30 seconds, the distance vector Router Protocol sends the entire route selection table to the adjacent site to update the route selection table of the adjacent site. In this way, it can collect a list of networks from other sites (directly connected or connected in other ways) for route selection. Distance Vector router uses the number of hops as the metric value to calculate the number of routers to pass to the destination.

For example, RIP uses the Bellman-Ford algorithm to determine the shortest path, that is, it can reach the destination line as long as it passes through the smallest hop count. The maximum number of hops allowed is usually set to 15. Terminals that must pass through more than 15 vrouters are considered inaccessible. Distance Vector router protocols include IPRIP, IPXRIP, AppleTalkRTMP, and IGRP.

3. What is the connection status Router Protocol? The connection status Router Protocol is more suitable for large networks. However, due to its complexity, the router needs more CPU resources. It can detect broken links or newly connected routers in a shorter time, so that the convergence time of the Protocol is shorter than that of the Distance Vector Router Protocol. Generally, if you do not receive the HELLO Message from the neighboring station within 10 seconds, the neighboring station is considered inaccessible. A connection status router sends an update message to its neighbor to notify it of all the links it knows. It determines that the measurement value of the optimal path is a numerical cost, which is generally determined by the bandwidth of the link. Links with the minimum cost are considered optimal. In the Shortest Path priority algorithm, the maximum possible cost is almost unlimited.

If the network does not change, the router only needs to periodically refresh the route selection table that has not been updated (the duration of the cycle can be from 30 minutes to 2 hours ). The connection status router protocols include IPOSPF, IPXNLSP, and IS-IS. Can a router use the distance vector Router Protocol and the link status Router Protocol? Yes. Each interface can be configured to use different router protocols, but they must be able to exchange routing information through the redistribution of routing.

4. What is an access table? The access table is a series of rules that the manager adds to control data packets input and output in the vro. It is not generated by the router itself. The Access Table allows or disables data packets from entering or outputting to the destination. The table items for accessing the table are executed sequentially. When the data packet arrives, the system first checks whether it is restricted by the first table item. If not, it is executed sequentially; if it matches the first table item, you do not have to perform the following table item check whether it is allowed or disabled.

5. When will route redistribution be used? Route redistribution is usually configured on routers responsible for learning routes from one autonomous system and then broadcasting to another autonomous system. If you are using IGRP or VPN, route redistribution is usually automatically executed.

6. What is Management Distance? Management Distance refers to the route reliability of a vro protocol. Each router protocol is assigned a level of trust from high to low reliability. This level of trust is called the Management Distance. For the routing information from two different router protocols to one destination, the router first determines which Protocol to trust based on the Management Distance.