How to solve problems encountered during static routing configuration

Many people may not have a special understanding of static routing configuration. So I studied how to solve the problems encountered during static routing configuration. I will share with you here, I hope it will be useful to you. When the routing selection table process checks a DNS static route that uses an intermediate address (the routing table is used as the IP address referenced by the next hop), this check is always completed in the category mode, whether or not the ip classless command is used, if the intermediate address in the category mode cannot be resolved in the route selection table, the static route is deleted.

If you use the classless method and a default route exists, a high management distance backup statement routing will never go into the routing table when the master static route fails. This is because any static route configuration that points to a non-existent intermediate address will use the default route for resolution. The CISCO Route Selection table process calls a Check Route Selection table every 60 s to configure static routes to install or delete static routes according to the dynamically changing route selection table.

Static Routing and intermediate address

Static Routing can be created using an intermediate network address or an outbound interface. In most cases, it is more effective to use the outbound interface to parse static routes in the route selection table process. As long as the intermediate IP address can be resolved in the routing selection table, it does not need to be a real next hop router interface. A static network route (such as an intermediate address) must be eventually resolved to a route entry with an outbound interface in the routing selection table. When a route table process needs to use a static route table entry for the x. x. x.0/24 network, it also needs to parse the intermediate address y. y, which is called recursive search. An additional route query may not affect the performance of the route selection process. However, multiple recursive searches are used to obtain the resolution configuration of static routes, which may affect the performance.

Static route optimization

To avoid recursive search: Serial Network: Ethernet network, which uses both an intermediate address and an outbound interface.

Install and delete static routes repeatedly

Use the outbound interface instead of the intermediate address as much as possible to configure Static Routing.

Use discarded routes

Sometimes a loop occurs in the network. You can view the result of the Route Selection loop through the counter on the router interface periodically. The routing loop problem creates a black hole in the network. Once the TTL in the IP header is reduced to 0, the group is discarded.

Solution 1: no ip classless routing -- use no ip classless on the user's network router. when at least one known subnet exists, the router does not use any supernetwork or default route. But not the first choice. Because it changes the query behavior of the Route Selection table of all groups.

Solution 2: Use a discarded route. When no specific match exists in the route selection table and an over-network or default route is used to forward those groups, A discarded route sends the group to null0, that is, the bit bucket. The next command line is used to configure another discarded route that is used only when the master route fails. You can change the default Management Distance of the configured static route to a value higher than the Management Distance of the used dynamic route protocol.