[c-nsp] 6500 netflow export and the switch cpu

[Ivan Gasparik]

On Thursday 11 September 2008, sthaug at nethelp.no wrote:
> > You can enable sampling if it is not enabled. It should help
> > some.
>
> Highly unlikely. Sampling on the 6500 is performed interely in
> software, *after* the full set of flows has been received.

You have to distinguish between the cpu load seen as interrupt load 
(caused mostly by walking through the TCAM, collecting statistics and 
storing them in netflow cache) and the cpu load caused by NDE process 
(packet generation). Enabling netflow sampling you can decrease the 
second part of the load - the cpu will generate significantly less 
packets of export statistics.

Ivan