On the switch, all standard routing protocols have default preference values that determine the routing priority of the protocol. The router uses default preferences to select the best route when a clash exists in preference between the protocols.
You can modify the global preference for a protocol to give the protocol a higher or lower priority than other protocols. If you change the global preference for a static route and all best routes remain best routes, only the local route tables change. However, if the protocol preference change causes best routes to no longer be best routes, the change affects neighboring route tables.
Important
Changing route preferences is a process-intensive operation that can affect system performance and network reach while you perform route preference procedures. As a best practice, if you want to change preferences for static routes or routing protocols, do so when you configure routes or during a maintenance window.
If a router learns a route with the same network mask and cost values from multiple sources, the router uses the route preferences to select the best route to add to the forwarding database.
Note
To modify the preference for a route, you do not need to disable a route before you edit the configuration.