service policy & CEF

Answered Question
Jul 10th, 2007

Hi,

Is it mandatory to have CEF enabled for proper functioning of policy-map applied on interface..

How & why ?

regards,

Gaurav

Correct Answer by a.shaik about 9 years 7 months ago

Hi Gaurav,

Please see this excellent document which explains why CEF is required.

http://www.cisco.com/en/US/tech/tk39/tk824/technologies_tech_note09186a0080094978.shtml

Hope this helps you

regards

Shaik ASSANA

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mohammedmahmoud Tue, 07/10/2007 - 02:49

Hi,

The link provided by Shaik ASSANA is very useful, in brief many useful class-based QoS features are supported only on routers that run CEF, ex: NBAR, CB-Marking, ..., and accordingly if you reqiure these features you'll need to run CEF.

HTH,

Mohammed Mahmoud.

vinay_verma80 Tue, 07/10/2007 - 04:04

we use CEF because policy map is like access-list , and we have to transfer at wired rate

if we do in software it will slow down the router as it has to match very large no of packets

use command in global config mode

ip cef ( this is enable by default on all new router which support cef)

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