CEF When to use it?

Unanswered Question
Dec 1st, 2009

Hello Everyone,

I have a router that is a stub, it's a 7200 series (old model) that is connected to another router (which is acting like it's gateway) model 7300 series.

There connection between both routers is a POS, and everything is working fine.

When we attempted to add another POS circuit therefore trying to create redundancy we noticed that the CPU on the 7200 series router is increasing with the increase in traffic.

I'm suspecting that the 7200 has a hard time load-balacing the 2 links, because as of now ISIS is what is balancing the traffic.

I was thinking of introducing CEF, but I don't know if it's possible.

Any Suggestions??


I have this problem too.
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Giuseppe Larosa Tue, 12/01/2009 - 07:15

Hello Paolo,

a C7200 is software based and adding a second POS STM-1 to it is not a minor change.

What you see is probably normal for this kind of device.

CEF load balancing is efficient here the problem should be that CEF tables cannot be loaded on ASICs to perform HW based forwarding there is just the main cpu.

There are few cases where it is needed to disable CEF and your scenario should be not one of them.

Hope to help


Mavrick25 Wed, 12/02/2009 - 01:10


I didn't quite understand your last statement could you clarify?

"There are few cases where it is needed to disable CEF and your scenario should be not one of them."

My situation is or is not one of them?

Thanks again for all your help


Giuseppe Larosa Wed, 12/02/2009 - 01:41

Hello Paolo,

sorry if it was unclear

in your case CEF has to be kept enabled on all interfaces and in global mode

Hope to help



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