Understanding CEF

Unanswered Question
Aug 6th, 2009

Hi all

Just wanted to know how CEF works. What happen to first packet: - it get routed or switched.

I have this problem too.
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Peter Paluch Thu, 08/06/2009 - 00:09


With CEF, even the first packet is switched. The CEF is built using the routing table as the source of information. Therefore, it is topology-driven and does not require actual packets to flow through the router as the normal route cache does.

This article is a wonderful overview of various switching methods in Cisco IOS, including CEF. Check it out!


Best regards,


Chetan Kumar Ress Thu, 08/06/2009 - 02:47

CEF is Packet forwarding Mechanism ………..

In simple words …… I can say It will Map your Entire routing table to Next Hop ………

So any User want to Communicate the packed will receive by router & it will see CEF table were to forward …….. The time for each packet will reduce ……… and your Packet forwarding will be fast ………..


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