I’ve seen this a few times now, where SNMP traps are being sent from vCenter even though there is no matching alarm on the management console. I haven’t managed to identify the main cause but find restarting the “VMware ESX Management services” on the relevant ESX host and the “VMware VirtualCenter Server” service appear to resolve the problem.

[root@esx01 init.d]# service mgmt-vmware restart

Stopping VMware ESX Management services:

VMware ESX Host Agent Watchdog [ OK ]

VMware ESX Host Agent [ OK ]

Starting VMware ESX Management services:

VMware ESX Host Agent (background) [ OK ]

Availability report startup (background) [ OK ]

[root@esx01 init.d]# service vmware-vpxa restart

Stopping vmware-vpxa: [ OK ]

Starting vmware-vpxa: [ OK ]

[root@esx01 init.d]#

Additionally, if you acknowledge any alarms in vCenter it will stop sending the SNMP traps until a new condition is met. Therefore, be sure that you want to do this!