IP CEF on switches - is it enabled by Default

Unanswered Question
Mar 23rd, 2010

Ladies/Gents,

Forgive me since this seems to be a grossly incompetent question.  I have been scouring cisco support and cannot find out what the deault

is for IP CEF on cat switch hardware (i.e. 35xx, 29xx, 37xx, 45xx and 65xx).

Is CEF only applicable on a MLS with "ip routing" enabled?

If someone could school me on this and also point to the body of literature it would be greatly appreciated.

James A. Abercromby II

732.614.9684

I have this problem too.
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Pronoy Dasgupta Tue, 03/23/2010 - 08:54

Hey James,

Not an incompetent question at all.

Well, what you wrote above was absolutely true (I am still trying to rake up documentation for the same), however CEF is enabled on layer 3 switches with IP Routing enabled only. And if I recollect correctly, you cannot turn it off (like on router platforms).

I distinctly remember having encountered this, if you try and enable CEF with IP routing disabled, the switch throws up an error message which explicitly asks you to enable IP routing first.

Would post you the doc as soon as I find one.

Thanks

Pronoy

JESlawinski Wed, 02/15/2012 - 12:02

It seems to depend on the switch model:

For a Cisco 3560v2 switch running:

Cisco IOS Software, C3560 Software (C3560-IPBASEK9-M), Version 12.2(58)SE1

Model number     : WS-C3560V2-48TS-S

A-05-38-S-01#sh cef state

CEF Status:

RP instance

common CEF disabled

IPv4 CEF Status:

CEF disabled/not running

dCEF disabled/not running

CEF switching disabled/not running

universal per-destination load sharing algorithm, id 8464B72F

IPv6 CEF Status:

CEF disabled/not running

dCEF disabled/not running

universal per-destination load sharing algorithm, id 8464B72F

When you run the command:

Test-Switch(config)#ip cef distributed

%Must enable ip routing first

For a Cisco 3750v2 switch running:

Cisco IOS Software, C3750 Software (C3750-IPBASEK9-M), Version 12.2(58)SE2, RELEASE SOFTWARE (fc1)

Model number                    : WS-C3750V2-48TS-S

A-08-25-S-01#sh cef stat

CEF Status:

RP instance

common CEF enabled

IPv4 CEF Status:

CEF enabled/running

dCEF enabled/running

CEF switching enabled/running

universal per-destination load sharing algorithm, id 400EC381

IPv6 CEF Status:

CEF disabled/not running

dCEF disabled/not running

universal per-destination load sharing algorithm, id 400EC381

On Cisco 3750v2 switches, cef is enabled by default  …

glen.grant Wed, 02/15/2012 - 14:19

Yes routing has to be turned on in order to use CEF on the 3560.

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