From: Arun Arumuganainar (aarumuga@hotmail.com)
Date: Tue Sep 20 2005 - 00:43:13 GMT-3
CEF is not the default on all platform . Catalyst Switches --> It's Yes .
But not on all low end IOS based router Platforms. Also note that you can
disable cef on Routers using no ip cef command . But this is not possible on
Cat switches .
Rule of Thumb : Features that are in forwarding plane could be affected by
CEF ( By Forwarding plane : I mean features that are triggered when the
packet arrives )
Some common Examples for Forwarding plane features : NBAR and other advance
QoS features , MPLS Forwarding , Packet filtering via accesslists , PBR etc
Note : Legacy features( eg : access-list , firewall etc ) can still work
with Fast switching or Process switching
CEF does not have any effect on signaling plane features. Typical Example .
Routing protocol features . Notable exception to this rule : MPLS Signaling
My recommendation : Always turn CEF on . It never harms you . On the other
side it may help you avoid some troubles when you do QoS sections .
Thanks and Regards
Arun
----- Original Message -----
From: "Marvin Wu" <marvinwu@gmail.com>
To: "Private Ryan" <pv.ryan@gmail.com>
Cc: "Cisco certification" <ccielab@groupstudy.com>
Sent: Monday, September 19, 2005 11:26 PM
Subject: Re: which feature require to enable "ip cef" ?
> NBAR also, but.. why not keep ip cef enabled? cef is the default switching
> method now anyway.
>
> -Marvin
>
>
> On 9/19/05, Private Ryan <pv.ryan@gmail.com> wrote:
> >
> > Some IOS feature require you to enable "ip cef".
> > Sometime, IOS may remind you to enable it, Sometimes, may not.
> > It is difficult to memorize when to enable "ip cef"
> >
> > As I remember, The following require "ip cef"
> > - ip verify unicast reverse-path
> > - CBWFQ
> >
> > any more ?
> >
> > Regards,
> > Ryan
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