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 ]
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!