Posted on December 22, 2020 5:25 pm
 |  Asked by cedric ayres
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I am trying to find samples rates for the 7280SR2A platform and how low the samples rates can go in hardware.

The doc does not highlight the rates and how low you can go.



Answered on December 29, 2020 11:56 am

Hi Cedric,

Thanks for reaching out.

Hardware-sampling rates are similar to that of CPU Sflow sampling rates.

switch(config)# sflow hardware acceleration sample ?
<1-4294967295> Rate              --->Hardware Accelerated sampling rate

switch(config)# sflow sample ?
<1-4294967295> Rate            --->CPU Sflow sampling rate

Also from the above TOI it states the following:

Sample rate configuration
By default, hardware-accelerated sFlow uses the same sample rate as software sFlow, as configured with “sflow sample <rate>“. A different rate can be configured (or reset) for hardware-accelerated sFlow with the following command: Arista(config)#[no|default] sflow hardware acceleration sample <rate>.


I have tested in the lab regarding the HW sampling rate as to how low(extensive) it can go in hardware by generating continuous source of packets via Ethxmit.

switch(conf)#bash sudo ethxmit --ip-dst= --ip-src= -D 73:48:96:d5:6e:7f -S 83:62:12:4f:5e:6f et49_1 -c

I have configured the minimum sampling rate to 1 (i.e aggressive sampling) which means that it would sample every packet from that particular flow.

Sflow Configs on switch:

switch(config)#sh run sec sflow
sflow sample 1
sflow destination
sflow run
sflow hardware acceleration
sflow hardware acceleration sample 1

Below is the result observed:

switch(config)#show sflow detail

Running: Yes
Hardware acceleration running: Yes   -->HW sampling is enabled and is running on the device.
Polling On: Yes (default)
Sampling On: Yes (default)
Sample Truncation Size for SW sFlow: 128 (default)
Sample Truncation Size for HW sFlow: 128

Total Packets: 0
Number of Samples: 41791208  
Sample Pool: 41791208                --->Every packet is getting sampled since HW sampling rate is 1.
Hardware Trigger: 94048845
Number of Datagrams: 5971577
Number of Samples Discarded: 0 -->No packet is getting discarded which means that it is sampling every packet for that particular flow.

So the minimum sampling rate in Hardware can go till 1(which is the most aggressive sampling rate).




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