Configuring a Preference Value for IPv4 IS-IS

If multiple routes to the same destination are discovered by different routing protocols, configure the highest priority value for IS-IS so that a route discovered by IS-IS can be selected preferentially.

Context

If multiple routes to the same destination are discovered by different routing protocols running on the same device, the route discovered by the protocol with the highest priority is selected.

For example, if both OSPF and IS-IS are configured on a network, the route discovered by OSPF is used because OSPF has a higher priority than IS-IS by default.

To prefer a route discovered by IS-IS, configure a higher priority value for IS-IS. In addition, you can configure a routing policy to increase the priority of specified IS-IS routes, without affecting route selection.

Procedure

Configure the IS-IS priority value.
1. Run system-view
  The system view is displayed.
2. Run isis [ process-id ]
  The IS-IS view is displayed.
3. Run preference preference
  The IS-IS priority value is configured.
  
  A smaller preference value indicates a higher preference.
4. Run commit
  The configuration is committed.
Configure a priority value for specified IS-IS routes.
1. Run system-view
  The system view is displayed.
2. Run isis [ process-id ]
  The IS-IS view is displayed.
3. Run preference { { route-policy route-policy-name | route-filter route-filter-name } | preference } ^*
  A preference is configured for the IS-IS routes that match the specified route-policy.
  
  preference takes effect only on IS-IS routes that match the specified routing policy.
4. Run commit
  The configuration is committed.