During Veeam replication jobs, your vCenter triggers the VM MAC conflict alarm. This happens because when a VM replica is created, it has the same MAC address and UUID as the original VM. This situation is totally expected because a newly created replica is an absolute copy of the original VM with exactly the same properties. This doesn’t create any issue, since the replicated virtual machine is not powered on, but more importantly because vCenter changes both replica’s MAC address and UUID. So, the issue is gone after a few moments, but the alarm remains in the console and it may be annoying. So, here’s how you can suppress the alarm.

First, we identify the error:

The alarm is defined and configued at the vCenter level. If you try to modify it directly inside the virtual machine alarms, you will notice that the Edit button will be disabled. In order to edit the alarm, we need to move all the way up into the tree on the left menu, select the vCenter itself and look at its Alarm Definitions. In this way, the Alarm can be edited:

Here, we don’t want to completely disable the alarm, as a MAC conflict can be a real issue if it happens for production virtual machines. But for Veeam replication jobs, we know that the conflict is not an issue, so we want to differentiate the two conditions. This can be easily done, because by default every Veeam replica VM is created with the _replica suffix in its name. So, we define this specific condition in the alarm:

As soon as we save the new version of the alarm, the error for the replicated VM immediately disappears, but if a “real” MAC conflict will happen in the future, the alarm will still be triggered.