What exact LMS version are you using?
As you said the configuration wasn't right and had incorrect commands on 3550-12G, what was it? Please share the commands configured on it.
You can verify which command LMS should ideally use, from this document :
List of Commands to Enable MAC Notification Traps on Devices
You can check the file MACCommands.XML from NMSROOT/campus/etc/cwsi/ from where LMS picks the MAC commands.
You can share this file and also check yourself if it has the correct commands as per the device sysObjectID.
If the device and its sysObjectID has missing entry, it may have the error coming as null.
-Thanks
Vinod
-Thanks
Vinod
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