From: Greg Wendel (gwendel@gmail.com)
Date: Mon Mar 03 2008 - 03:06:34 ARST
Tony,
Could you be more specific in your criticisms instead of attacking Rik? You
just added to the confusion.
On Sun, Mar 2, 2008 at 11:59 PM, Tony Varriale <tvarriale@flamboyaninc.com>
wrote:
> Any chance you would be able to do some research first and not propagate
> incorrect information regarding CEF? It would certainly help the original
> poster's confusion.
>
> Tony
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Rik
> Guyler
> Sent: Sunday, March 02, 2008 10:31 PM
> To: 'Gaurav Prakash'; 'groupstudy groupstudy'
> Subject: RE: Load balancing
>
> If you have CEF (Cisco Express Forwarding) enabled then you are running
> per-destination load balancing. CEF relies on a route cache concept that
> only performs a route table lookup on the first packet of the flow and
> then
> relies on a hardware-based cache for the remainder of the packets. Since
> the lookup only takes place once during the lifecycle of the flow the CPU
> utilization is minimized and the actual packet switching process is much
> faster. This is one of the fast switching paths in Cisco architecture.
>
> In contrast, per packet load balancing, which is called process switching
> (CEF/ip route cache disabled) requires a route table lookup for each
> packet
> so the processor has to work extra hard to do this. The switching
> function
> between interfaces is slower in this mode.
>
> CEF is usually a good thing and typically turned on by default these days.
> Many things require CEF, such as QoS but there are times when you need to
> enable process switching (turn off CEF) such as when you want to run
> certain
> packet debugs. In those cases process switching is the only solution as
> fast switching will not take the packets through the debug process. You
> can
> turn off fast switching globally by typing "no ip cef" or on an interface
> by
> typing "no ip route-cache".
>
> This is just a general explanation for typical devices. Some of the
> higher
> end devices have more options than this.
>
> Rik
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
> Gaurav Prakash
> Sent: Sunday, March 02, 2008 11:01 PM
> To: groupstudy groupstudy
> Subject: Load balancing
>
> Hi,
>
> I have CEF on on my router, I want to be sure which method of load
> balancing will eat more CPU.
>
> Per packet Load balancing or Per Destination Load Balancing
> A brief explanation plz..
>
> Regards,
> Gaurav
>
>
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>
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-- Gregory Wendel Springfield VA, 22153
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