Router configuration details that are easy to ignore

This article attempts to find and summarize vro configuration errors from the perspective of the routing protocol. These errors are caused by incorrect configuration of the routing protocol rather than incorrect configuration on the host side, although it may not be the most common mistake, it often occurs and can be easily solved through the solution proposed in this article.

Details 1. Unmatched neighbor parameters in OSPF

To establish an association with neighboring nodes, OSPF-based routers usually need to maintain several common parameters. These parameters include authentication, Region ID, mask, Hello interval, and router extinction interval. In actual network deployment, incorrect neighbor parameters, such as nonstandard configurations and incorrect passwords, may cause node Association failure. For such errors, the network administrator can easily find out whether the errors are caused by mismatched neighbor parameters by Debugging commands related to OSPF joining and which parameters are incorrect, then modify.

Detail 2: Ignore filtering when route reallocation

When re-assigning a route (redistributing routing) to a router, You need to enable the routing filtering function to delete the paths that may cause loop. Therefore, if you do not apply a routing filter policy, errors are usually caused. However, it is complicated for administrators to filter out a large network without complete global information, and the path here or there may be missed. Therefore, the best way to avoid this problem is to try not to re-allocate routes. In fact, re-allocating routes is usually a bad strategy, in fact, we can find the correct solution to the problem without re-assigning the route.

Details 3: the configuration of the OSPF metric is unreasonable.

For administrators, it is usually difficult to adjust the network traffic measurement indicators reasonably. In general, sending business traffic over Internet VPN may be more reasonable than using a low-bandwidth Frame Relay line, so more traffic should be allocated to the former. Bandwidth and latency indicators seem easy to set. However, for administrators, if they want to add all the metrics they have set to the target function formula for weighting, it is difficult to assess whether the expected traffic distribution effect can be achieved.

Details 4. Forgetting to configure Metrics (Metrics)

If you find that all the path information is lost when you re-allocate routes in the network based on the VPN protocol, it is very likely that the Administrator forgot to configure the route measurement index (Metrics ). For example, a Cisco router rejects the function of automatically setting the route measurement by default, and forces the Administrator to manually set the measurement. Therefore, if the Administrator does not set a measurement indicator, re-assigning the route will not succeed. At the same time, it can be seen that when the network is used, re-routing is not a reasonable choice.

To solve this problem, the administrator should set the measurement indicator by running the "default-metric bandwidth delay reliability loading mtu" command, alternatively, you can directly use "metric" as the keyword of the redistribute command when re-allocating a route.

Details 5: The subnet password is missing when the route is re-allocated.

When you re-allocate routes to an OSPF-based network, another common error is that several paths are lost, this is usually because the Administrator network attaches the subnet keyword to the end of the reallocation command. For example, for a Cisco router, The subnet keyword is critical when OSPF re-allocates a subnet route. If there is no keyword with the subnet mask, OSPF only re-allocates network routes outside the subnet.