OSPF Path Selection with Neighbor Cost

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Task 1

Remove Task 2 configuration from the previous lab.

Task 2
The following prefixes (marked in red rectangle) are advertised by both R3 and R4 (pic. 2). Configure R1 so that it prefers R3 towards these destinations. R4 should only be backup router in case frame-relay circuit towards R3 is down.

Pic. 2 - Prefixes Advertised by Both R3 and R4.

Questions

Try to answer the following questions:

1. If the task did not stipulate that the configuration had to be done on R1, what would be the alternative methods of accomplishing the same goal?

Lab Solution

Solution configuration can be accessed below (if you want to save it, click the link, then go to File-->Download):
https://drive.google.com/file/d/0BwE5C95tpjZOak0wQ3AzUTEtaFE/edit?usp=sharing

Task 1

Remove Task 2 configuration from the previous lab.

R2 Config:
!
interface fastethernet0/0
 no bandwidth 10
!

Task 2
The following prefixes (marked in red rectangle) are advertised by both R3 and R4 (pic. 2). Configure R1 so that it prefers R3 towards these destinations. R4 should only be backup router in case frame-relay circuit towards R3 is down.

R1 Config:

!

router ospf 1

 neighbor 172.16.0.4 cost 100

!

Note!
This solution 'neighbor address cost value' can only be used in 'ospf network point-to-multipoint' mode.

Pic. 3 - Path Verification.

Study Drill

Of course, there are usually more than one methods of accomplishing the same goal. If the task did not stipulate that configuration was supposed to be done on R1, we could change the original metric of the prefix on the advertising router(s) using the 'ip ospf cost' command. In case it was not loopback interface, we could also use the bandwidth command to manipulate the original cost calculation.

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