Resolving VM MAC Conflict alarm with Veeam Replicas

It’s been awhile since I’ve deployed Veeam using replication with vSphere 6.0.  I recently implemented it for a customer who was replicating VMs to a secondary storage appliance in addition to backing the VMs up to a Data Domain.  Upon running the initial replication for the VM, a “VM MAC Conflict” alarm triggered on the replica VM.

vm mac conflict alarm triggered

Here’s a description of what’s going on and how to prevent the VM MAC Conflict alarm from triggering.

VM MAC Conflict Alarm

The VM MAC Conflict alarm is new to vCenter 6.0 Update 1a.  The intent of the alarm is to warn you if two vNICs on VMs within a vCenter instance have the same MAC address.  This can happen for a variety of reasons:

  1. vCenter malfunctioned and dynamically provided the same MAC address to two or more vNICs.
  2. Either intentionally or mistakenly, an admin or a third party product might have statically assigned a MAC address already in use within the environment.  In this case, Veeam created a copy of the VNX file with identical MAC addresses for the source and replica VM’s vNICs.

It’s a good alarm to have to notify you just in case.  But how do you keep this alarm while stopping it from triggering on replica VMs?

Stopping VM MAC Conflict Alarms from triggering for Veeam Replicas

The solution for preserving the VM MAC Conflict alarm while stopping it from triggering on Veeam replicas is quite simple.  You can modify the alarm itself by setting an exception to exclude VMs.  In the case of Veeam replicas, they have a “_replica” suffix within the VM name by default.  If you changed that suffix in the replica job, just adjust accordingly.

Go to the VM MAC Conflict alarm definition.  It’s in the vCenter inventory object under Manage > Alarm Definitions.  Click the alarm and on the right, click Edit.

Under the bottom box that reads, “The following conditions must be satisfied for the trigger to fire”, add a condition that says the VM name does not end with “_replica”.  Once applied, the alarm disappears for your replica VMs.

vm mac conflict alarm modified

That’s it!