Tuesday, May 5, 2009

OSPF routing part XI - preferred neighbor

A hub router in an OSPF topology has two neighbors connected over a single serial interface. The hub router is learning the same routes from both neighbors. How can the hub router be configured to prefer routers from a particular neighbor?

The solution to this problem brought to light a configuration parameter that had previously missed my attention. When using the ospf 'neighbor' command a cost can also be applied to routes learned from that neighbor.

Hence to achieve the requirement laid out simply required this parameter to be set accordingly

i.e. below i set a lower cost for neighbor 2. This could be usefull in the scenario where neighbor 2 has a connection with greater bandwidth or reliability.

router ospf 1
neighbor {ip address 1} cost 200
neighbir (ip address 2} cost 100

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