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I look after an HP NNMi instance, a network management station which mainly does SNMP polling to get statistics from network devices.

I have been asked if it is possible to get utilisation statistics for a Vlan interface, but my initial investigations have revealed that the normal way to do this results in an SNMP counter sitting at 0 for input octets (ifInOctets), and therefore the ifInUtilizationPct is also sitting at 0.

For the output side, I can at least see some counters are non-zero, but the utilisation one is 0.

Is this a limitation of SNMP with respect to vlan interfaces, or is this something that can be fixed or worked around?

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  • Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could provide and accept your own answer. – Ron Maupin Aug 13 '17 at 3:06
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I'm not familiar with this specific model, but having no counter incrementation on vlan interfaces is pretty common. It's not so much a limitation of SNMP as a limitation of how the switch itself is built. The ASICs behind the interfaces often do not allow for updating per-vlan counters.

Also beware that if you look at the standard MIB2 counters, you're usually seeing either physical interfaces or layer 3 Vlan interfaces (SVIs). So even if you were to read a non-zero value there, it would be packets routed to or from that VLAN on layer 3, not packets switched within that VLAN on layer 2.

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