sFlow reporting on EX4200

Not seeing the interface utilization you expect to see from your Juniper EX4200 sFlow exports?

I was working with a customer exporting sFlow from an EX4200 to his sFlow Analyzer and was seeing extremely low utilization, even low for a sampling technology.

We opened a case with Juniper Networks for their help in resolving this and this is what they found.

Routed interfaces

sFlow exports from Juniper EX series switches with code versions 10.1 (S1, R2, R2, S6, etc.) may not report from routed interfaces accurately, specifically under-reporting.

For example, configuring:

xe-1/0/0 {
      unit 0 {
           family inet address 1.2.3.1/30;
      }
}

And then configuring sFlow sampling on xe-1/0/0.0, only traffic locally destined to the control panel is sampled. Transit traffic is not sampled.

Switched Interfaces

On switched interfaces:

xe-1/0/0 {
      unit 0 {
           family ethernet-switching {
               etc., etc.
           }
       }
}

sFlow sampling works fine and as expected.

Resolution

This has been corrected in release 10.2R3.10 and has been confirmed that sFlow exported from routed interfaces works fine in that version of code.

Thank you, Juniper Networks support, for your diligence and resolution for our customer’s issue.