FAQ-What Are the Rules for Selecting Routes Belonging to Different OSPF Processes

Publication Date:  2015-05-05 Views:  130 Downloads:  0
Issue Description
What Are the Rules for Selecting Routes Belonging to Different OSPF Processes?
Solution
OSPF supports multi-processes. Multiple OSPF processes can run on the same router independently.

Assume that a router is configured with two OSPF processes: process 1 and process 2. They are independent of each other. Therefore, both of the routes belonging to process 1 and process 2 are advertised to the routing management (RM) module. Route selection between the two processes complies with the following rules:

1.  The RM module checks the protocol preference of process 1 and process 2. The route belonging to the process with higher protocol preference is selected as the optimal route.

NOTE:
To set the preference of an OSPF route in the specified process, run the preference [ ase ] { preference | route-policy route-policy-name } * command. The default preference of an OSPF route is 10. When an ASE is specified, the default value is 150.

2.  When the protocol preferences of the two processes are the same, the RM module compare the cost of the two routes. The route with smaller cost value is selected as the optimal route.

NOTE:
When selecting the optimal route, the RM module first compares the protocol preference. The RM module compares the cost of routes only when the protocol preferences are the same.

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