[c-nsp] nfSen / nfDump

[Nick Hilliard]

Nick Cutting wrote:
> sflow sampling-rate 4096 <-- this is 512?

that means that out of every 4096 packets received on an interface, one
will be punted to the sflow collector.  You can check the hardware
sampling rate using the PortSampRate command in the broadcom shell, like
this:

> n3k# test hardware internal bcm-usd bcm-diag-shell
> Available Unit Numbers: 0
> bcm-shell.0> PortSampRate
>  xe0:	ingress: 1 out of 4096 packets,	egress: 1 out of 4096 packets,
>  xe1:	ingress: 1 out of 4096 packets,	egress: 1 out of 4096 packets,
[...]

Sflow sampling is handled in hardware and is reasonably accurate on the
broadcom chipset.

If you're seeing ~2x the number of packets, bear in mind that nxos
samples in both directions with no option for only ingress or only
egress.  There is no good reason for having this limitation, because
it's trivial to modify in using the bcm-shell with the portsamprate
command, and the lack of ability to specify the sampling direction makes
the sflow functionality on this operating system pretty useless.

Nick