Change OSPF Cost - One Interface

[RyanL841]

I am trying some things out in a lab environment for a DR suggestion.

So I have the same network being advertised on both R1 and R3 but these are "technically" not the same as R1 is production and the R3 is DR. So these are not "really" redundant connections they just to happen to be advertising the same network.

All of these routers connect to a switch to simulate a Metro/MPLS from a service provider. So there is only one physical uplink for all of these routers.

I am trying to see if there is a way to change the cost of one of those routes, instead of being equal. I know I can do this per interface (ip ospf cost) but I am not sure how I would be able to do this with only one interface ...

So here is the route table (showing ip route and omitting everything but OSPF routes) on R2:

O 172.20.2.0      [110/2] via 172.16.2.3, 00:21:06, FastEthernet0/0

                         [110/2] via 172.16.2.2, 00:21:06, FastEthernet0/0

I would like to see if there is a way to prefer 172.16.2.2, and not use 172.16.2.3 unless 2.2 is unavailable.

Suggestions?

Thanks for you help.

Ryan

[Rolf Fischer · Accepted solution]

Hi,

the switch simulates a service provider, so R1,R2 and R3 are under your administrative control?

If so, you simply could increase the seed costs of all the DR networks (ip ospf cost).

Or you could change the interface types to point-to-multipoint non-broadcast in order to use the cost option of the neighbor command:

(config-router)#neighbor 192.168.0.1 ?
 cost             OSPF cost for point-to-multipoint neighbor

Hope that helps

Rolf