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CEF

hi,

Is CEF and Layer3 switching is same ?

regards

Neo

6 REPLIES

Re: CEF

Hi!

Well CEF that is Cisco Express Forwarding is an advanced Layer 3 IP switching technology, so CEF is a method of performing Layer 3 switching. Layer 3 switching can be performed using both hardware and software. CEF is the software method of performing it. CEF is a better method as it less CPU intensive, so mor e of CPU can be dedicated to other services.

For more please refer the following links -->

http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/switch_c/xcprt2/xcdcef.htm

http://www.ciscopress.com/articles/article.asp?p=102093&rl=1

Hope this helps.

Please rate all helpful posts.

Regards,

AbhisheK

New Member

Re: CEF

Please correct me if I'm wrong but I was under the impression that CEF was hardware based as opposed to process switching which is software based!?

Hall of Fame Super Gold

Re: CEF

CEF is not hardware based. CEF uses a different approach to building and managing the caches used to optimize making the forwarding decision for IP packets.

HTH

Rick

Bronze

Re: CEF

Rick,

I was under the (perhaps mistaken) impression from my recent exposure to BCMSN material that the wire speed performance in cisco multilayer switches running IOS is due to specific hardware, such that a 'normal' IP packet that would usually require router processing could be switched between different VLANs using hardware (sending the oddball packets to the L3 engine). The book calls this CEF.

In other words, cisco L3/L4 switches implement CEF caching for routine IP traffic in hardware whereas routers implement it in software (and probably in varying ways due to the different architecture of each routing platform - a 7500 has different plumbing than a 2500).

John

New Member

Re: CEF

Hi John

That was also my understanding.

New Member

Re: CEF

L3 switching refers to hardware based processing of L3 packets (not necessarily CEF). However, there are different methods for building and maintaining the data structures used to make the forwarding decisions. CEF and Process switching are two of those methods. Please take a look at the following document which compares and discusses the characteristics of CEF, as well as, Process switching (and others).

http://www.cisco.com/en/US/tech/tk827/tk831/technologies_white_paper09186a00800a62d9.shtml

Thanks,

Scott

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