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Monitoring trunk ports' individual VLAN bandwidth

Will White
Level 1
Level 1


Is there any way to get octet counters for individual subinterfaces on a VLAN trunk port on, say, 2900 or 3500 series? - For monitoring purposes.

Example: Port A is a trunk of VLANs 2,7,8

I can get the total sum of all the data (VLANs 2,7,8) in the physical port A by just looking at SNMP ifOctets, but is there any way to know how many bytes pass through each of the subinterfaces? I know that the SNMP counters for VLAN interfaces are wrong due to how the hardware works.

From what I have read, this is completely impossible??


2 Replies 2

Level 4
Level 4

I also don't think that it is possible. Sorry. Not even with mrtg or cacti because they only read the interface counters of the switch anyway...same way as you are.



Will White
Level 1
Level 1

Yes that is true. I do not know enough about the hardware, but could it be possible to force the switching to go through CPU? I know about "no ip route-cache" but that does not apply in here, right? Is there any other similar command for 2900 series?

Looking it at a different angle and forgetting SNMP. With Netflow it could be possible in my opinion - but even then it is difficult. Would need to setup the collector to aggregate all flows per VLAN (looking at source/destination subnets). Which is a lot of work. And anyways not supported on the hardware I have.

I just cannot believe that it is impossible, surely people need to know this kind of statistics and have found a way to do it.

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