[c-nsp] ip cef / ospf redundancy testing

Adam Greene maillist at webjogger.net
Tue Dec 30 14:14:30 EST 2008

Maybe someone could point me in the right direction ...

I'm doing some redundancy testing in the lab ...

I basically have two 3750's linked together redundantly via OSPF. IP CEF is enabled. Both switches are running 12.2(25)SEE2. Switch B is receiving redundant default routes from switch A.  

According to "sh ip cef exact-route" issued on switch B, traffic from <src1B> to <dest1A> and from <src2B> to <dest2A> should be all be travelling over a single link, leaving the other one empty of traffic. However, what I am actually seeing is that traffic from <src1B> to <dest1A>  is flowing over one link, and from <src2B> to <dest2A> is travelling over the other.

"sh ip cef detail" confirms that per-destination load balancing should be occurring, and when I run a single stream of traffic, indeed round-robin per-packet load-sharing is not occurring.

Why would the traffic be following a different path than what the "sh ip cef exact-route" command suggests it should?

Maybe I need to provide more detail for anyone to be able to opine ...


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