Distributed CEF

[jpl861]

Hi, I read some information about dCEF wherein a copy of the FIB will be pushed to the linecard to offload traffic from the RP. My question is, is this applicable to 6500 switches with cards that has DFCs? I have a 6500 switch with Sup720-3B, some linecards does not have DFC, some have CFC, and some have DFCs. Would it be better to turn on "ip cef distributed"? Is the performance going to improve? If I enable distributed CEF, is there going to be an impact or downtime? I know it is always advisable to do this during window time but we are running 24/7. Thanks in advance. JL

[Joseph W. Doherty]

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

Distributed CEF might be the default for 6500's DFCs.  (I recall back in the 7500 days, you needed to explictly enable it for VIP cards to run CEF too.)

Try show cef state, and see if you see dCEF enabled/running in the output.

If you have DFC, yes it's better for distributed CEF to be active.  Whether you would "see" a performance difference is a "it depends" answer.

I'm not positive, but I suspect enabling or disabling dCEF would cause no or minimal impact (minimal, as in, drop a few packets in transit).

[Jon Marshall]

John

Yes it is applicable to 6500 linecards with DFCs in them. The supervisor will download a copy of the FIB to the linecard so it can make local forwarding decisions without having to send a part of the packet to the supervisor.

On the 6500 "ip cef distributed" is enabled by default so you shouldn't need to turn anything on ie. if you have DFC linecards they should already be using a local FIB for switching decisions.

Jon