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OSPF- link flapping behaviour

Brett Martin
Beginner
Beginner

Hello,

I was hoping someone could explain to me how OSPF handles link flapping. My scenario is we typically have a preferred primary path through the network, a secondary and then a backup over leased lines. The primary path has been created by applying ospf costs to interfaces. Ideally we want traffic to remain over this primary path.

If the primary path fails, it takes about 15-20 seconds on our network to converge and take the secondary path. The concern I have is if the primary fails, recovers, fails, etc...could we be in a state where the network would remain down whils OSPF is in a constant state of reconvergence?

Are there any mechanisms built into the routing protocol to detect and prevent this--kind of like hysterisis we have in loop switch devices for DS1 rings? There are reverting timers where the primary path needs to be up error free for a certain period of time before the circuit reverts.

Thanks!

Brett

1 Reply 1

Peter Paluch
Hall of Fame Cisco Employee Hall of Fame Cisco Employee
Hall of Fame Cisco Employee

Brett,

Have you been looking into interface dampening? That could perhaps be useful.

http://www.cisco.com/en/US/docs/ios/12_0s/feature/guide/s_ipevdp.html

Best regards,

Peter

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