Nexus 5010 SNMP bug?

Unanswered Question
May 27th, 2010

Hi,

We're running a set of 5010 switches and in preparation for some soak testing embarked on setting up our usual snmp based monitoring. After letting the graphs settle we started to see wild results in terms of the amount of traffic claiming to traverse all of the interfaces. A 10G switch it may be but with not much running behind it graphs claiming up to 15G were a little strange to say the least!

Anyways digging further and trawling for similar issues we came across an issue with versions < 4.1(3)N(2a) not supporting 64 bit counters for physical interfaces - these threads alluded that this version fixes the problem and we are infact currently running 4.1(3)N(1)

However we've seen a slight difference in this behaviour whereby both the 32 bit and 64 bit counters exist but claim to be reporting the same value - which is incorrect.

[root@poller1 ~]# snmpget x.x.x.x -c blahblah -v2c  ifHCInOctets.436215808
IF-MIB::ifHCInOctets.436215808 = Counter64: 407787321
IF-MIB::ifHCInOctets.436215808 = Counter64: 407787321
IF-MIB::ifHCInOctets.436215808 = Counter64: 407787321
[root@poller1 ~]# snmpget x.x.x.x -c blahblah -v2c  ifInOctets.436215808
IF-MIB::ifInOctets.436215808 = Counter32: 407787321

There are no references to any physical interfaces in the ifHCInOctet tree yet a value is still returned; and furthermore we see huge disparities in the value returned; peaks suggesting a huge spike in traffic, which as the number is no longer accumulative is playing havoc with our monitoring system's calculations

IF-MIB::ifHCInOctets.436215808 =  Counter64: 130822020033
root@poller1 ~]# snmpget x.x.x.x -c blahblah -v2c ifHCInOctets.436215808
IF-MIB::ifHCInOctets.436215808 = Counter64: 130822020033
root@poller1 ~]# snmpget x.x.x.x -c blahblah -v2c ifHCInOctets.436215808
IF-MIB::ifHCInOctets.436215808  = Counter64: 407517806         BACK TO NORMAL??
root@poller1 ~]# snmpget x.x.x.x -c blahblah -v2c ifHCInOctets.436215808
IF-MIB::ifHCInOctets.436215808 = Counter64: 407517806

Clearly something isn't right and my next course of action is to upgrade to try and circumvent the problem.

To put our minds at rest is this a common bug and has it been solved in version 4.2? Resolved caveats doesnt mention this, or the other issues

Many thanks,

Ed

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Gary Ross Fri, 08/20/2010 - 01:01

We hit, what appears to be, a similar bug in NX-OS 4.1.3a on our MDS 9513's.  I've since found

out this bug was resolved in NX-OS 4.2.x on the MDS side of things.

I would assume the same is true for the Nexus switches.

Sorry I don't have a definitive answer for you on this.

Gary

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