Unanswered Question
May 8th, 2007

what is CEF? anyone can give useful links regarding CEF?

I have this problem too.
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Overall Rating: 3.8 (3 ratings)
revilo3246 Wed, 05/09/2007 - 21:19

thanks! do you know where I can get Cisco IOS for 3620 routers?

adrian.chadd Tue, 05/08/2007 - 23:24

Sure can:

Cisco's CEF techonology page:


Circa IOS 12.0 CEF overview:


In a nutshell: CEF is a method of building a Forwarding Table in RAM (and later, on individual cards which support it (distributed CEF)) for making forwarding decisions in the "fast" interrupt path, rather than writing packets into an input queue to be serviced the "traditional" process switched way by a seperate "IP Input" process.

It gets more complicated than that, but thats the general gist of things.

Please rate if this helped,


mohammedmahmoud Tue, 05/08/2007 - 23:36


Kindly check the attachment, and please don't hesitate for any further questions.

HTH, please do rate if it does help,

Mohammed Mahmoud.

Richard Burts Thu, 05/10/2007 - 05:14


You get IOS from Cisco web site. The link that Mohammed provides is a good way to get there. Or from the main home page you can login, and under the support tab there is a link for download software.

Note that to download software you must be a registered user on the Cisco site and your profile must have software download privileges (usually dependent on having equipment with a maintenance agreement with Cisco).




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