I was actually surprised that this was not one of the pre-created default alarms in vCenter Server as I can see this being extremely useful to have out of the box.

It turns out there is an out of the box event called ' VM Mac conflict' which can be triggered using a vCenter Server alarm when a duplicated MAC Address is detected for a VM. While performing some research in my lab environment the other day, I accidentally stumbled onto this little tidbit in vCenter Server. I definitely recommend creating an alarm for both Events for the vCenter Alarm. UPDATE (4/22) - Thanks to Petr, it turns out there is another MAC Address conflict event which I did not know about specifically for detecting duplicate entries for manually assigned MAC Addresses called ' VM static MAC conflict'. What would be nice is to be able to automatically detect that a MAC Address conflict has occurred and provide the necessary information of the offending VMs. In both of these scenarios, when a duplicate MAC Address occurs, time is of the essence to quickly pin-point the source of the duplicated entry and quickly resolving the conflict.

You migrate a VM from one vCenter Server to another and the destination vCenter Server has already assigned the MAC Address of the migrated VM.

You manually assign a static MAC Address versus using dynamic assignment (includes VM import) and it conflicts with an already assigned MAC Address.

There are two cases that I can think of where a duplicate MAC Address can potentially occur: Having a duplicate VM MAC Address in your environment can lead to an extremely painful day of troubleshooting and it can also be tough to prevent depending on how and where you provision your VMs.

Convert mac address to pin