OSPF Path Selection

[rodrigo.cisco]

Hi guys,

I have some doubts about how can I configure the OSPF on routers A,B,C and D to force they to use the path through routers A->C or B->A->C for packets from/to route 10.0.1.0/24 and path through routers B->D or A->B->D for packets from/to route 10.0.2.0/24 but keeping the alternate path in case of link problems. I will apreciate any help or just listen your option.

Below a draft of the topology:

Regards,

Rodrigo Alves

[Ganesh Hariharan]

OSPF uses path cost as its basic routing metric, which was defined by the standard not to equate to any standard value such as speed,In practice, it is determined by the speed (bandwidth) of the interface addressing the given route, although that tends to need network-specific scaling factors now that links faster than 100 Mbit/s are common.

Cisco uses a metric like 10^8/bandwidth. So, a 100Mbit/s link will have a cost of 1, a 10Mbit/s a cost of 10 and so on. But for links faster than 100Mbit/s, the cost would be <1.

IP OSPF Cost under interface configuration

This command is used to manually set the OSPF link cost. This is typically done for traffic engineering purposes to modify what link OSPF will prefer. Lower is better.

Hope to Help !!

Ganesh.H

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[rodrigo.cisco]

Ganesh,

I understand your point of view, but I have to say that this solution can't help me. For instance, If I worse the path between routers A and C, all of my traffic will use the path between routers B and D. I would like to do something like PBR but using some OSPF policy to change de metric (cost) based on the source network.

I hope I have clarify a little more.

Anyway thank you in advance for you help!