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What does the preference field mean in the routing table? I believe many inexperienced people are helpless about it. For this reason, this article summarizes the causes and solutions of the problem. Through this article, I hope you can solve this problem.

The Preference field represents the routing priority in the routing table. Equipment manufacturers specify different priorities for different routing protocols in their products.

Routers often support multiple routing protocols, and the support of multiple routing protocols has a problem of selecting and coordinating multiple routes. In order to solve this problem, the concept of preference is introduced into the parameters of routing.

Each routing protocol generally sets a fixed preference value, and the smaller the preference value, the higher the priority of the route corresponding to the protocol. In general, routing priorities are defined as follows:

routed directly 0OSPF routing 10IS-IS level 1 routing 15IS-IS level 2 routing 18 SPF routing of NSFnet backbone 19 Silent Gateway and EGP Default 20 redirected routes 30 routes derived from route socket 40 Routes added by network management 50 Routes discovered by routers 55 Static routing 60Cisco IGRP Routes 80DCN hello routing RIP routing for 90Berkeley 100 Point-to-point interface aggregation routing 110 Interface routing in down state 120 Default route priority for aggregation 130 Extended Routing for OSPF 140BGP routing 170EGP routing 200

The concept of route priority is that a new route with a higher priority can replace a route with a lower priority and the same destination, and vice versa. However, it is possible that certain changes will be made in the specific implementation. RIP-2 under quidway2501, for example, provides a command to change RIP routing priority. This command changes the priority of RIP routing. Quidway2501 can also specify route priorities when configuring static routes, which is application-specific processing. However, we do not encourage priority modification.

The difference is between metric and preference. Metric is for the same routing protocol, for different protocols, because the meaning of the representation is different, it is meaningless to compare the metric of different protocols, so to choose between two different protocols with the same destination route, only the priority of the route can be compared. In contrast, preference is the priority of routes of the same protocol for different protocols, and metric is the criterion for choosing between two routes of the same destination.

After reading the above, do you know what the preference field means in the routing table? If you still want to learn more skills or want to know more related content, welcome to pay attention to the industry information channel, thank you for reading!

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