SNMP mac address change notification trap problem

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Jan 22nd, 2009
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Hi everyone,

I have a bunch of 4948s sitting on top of racks, and some in access/distribution as well. I set up mac address notification SNMP traps, but for some reason I'm not receiving full content in the traps. Software is 12.2(46)SG. What I'm missing in the content is cmnHistMacChangedMsg. Instead of an octet string, I get a hex string. I.e. the switch only sends the operation type (added/removed) and doesn't send the vlan, port and mac address, thus rendering the traps useless. When I debug snmp packets, the switch sends:

cmnHistMacChangedMsg.xx = XX

Instead of:

cmnHistMacChangedMsg.xx = XX XX XX XX XX XX XX XX XX XX XX XX

Does anybody have any idea why is this happening? Is it just software related, or is it some platform limitation?

If it is a platform limitation, then is it posible do read the mac address notification history table with snmp get - since I receive the history entry number in the trap? This way I could at least use a workaround by setting up a trap handler that queries the history table and logs the entry.

Another thing is that in snmpv2 traps it sends cmnHistTimestamp as Integer, while it should be sending it as TimeTicks - but I can live with this, the main issue is cmnHistMacChangedMsg...

Many thanks,


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Overall Rating: 4 (1 ratings)
Yudong Wu Thu, 01/22/2009 - 14:07
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it should be related to bug

CSCsr84693 Incomplete MAC notification SNMP trap on 4500s

wojciechowczarek Fri, 01/23/2009 - 05:32
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Thanks, that explains a lot... "Fixed in" is currently "pending" for that bug - and nothing is mentioned in release notes for 12.2(50)SG - do you know if this release fixes this bug? I can't revert to 12.2(44)SG as we need the management ethernet ports on the switches - and this feature was only introduced in (46).

Best regards,


Yudong Wu Fri, 01/23/2009 - 07:54
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Based on info I had, it should be fixed in 12.2(50)SG.


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