Evening,

I just wanted to write this quick blog post to help people who use Veeam to replicate their VMs on vCenter 6 U1B or newer. Apparently somewhere in the vCenter 6 lifeline it was decided that an alarm will trigger if a MAC address conflict was detected. I personally am all for this trigger as it flags on the new VM. But first a little background on the issue.

Why is this alarm triggering?

In all honesty the reason it’s triggering is because both Veeam & VMware are both doing their job perfectly (SHOCK HORROR!). When Veeam creates a replica, initially it is a complete byte for byte replica, the only differences between the VMs are the data committed after the snapshot generation and the name of the VMs. Once Veeam has finished making the replica VMware steps in, notices that there’s a MAC Address Conflict and moves to resolve it. The only missing step is that VMware isn’t clearing that alarm afterwards.

What the forums have been saying compared to what I say:

I searched the Veeam forums and saw a few people complaining about this and the Veeam support engineers repeating my message above “it’s actually just doing its job”. This has lead many people to state “just disable the alarm”. Now that in itself will fix the problem, but by doing so we’re limiting how helpful VMware actually can be when we’re troubleshooting a problem. Since it’s possible to manually create a duplicate MAC address quite easily why should we make our job harder. Here’s what I did instead:

I navigated to my vCenter instances on the vCenter Web Client, clicked manage and then alarm definitions. Scrolled through the list to find the alarm called “VM MAC Conflict”. Instead of choosing disable I chose edit, clicked next to get to the triggers and added some simple conditional logic.

Argument: VM name

Operator: does not end with

Value: _replica

This is the default suffix for replicas in Veeam and if you’ve set this to something else you’ll just need to update the value to whichever suffix you’ve chosen.

Conclusion:

That’s it, now our Veeam replicas won’t create alarms in VMware but we still have this great feature in hand to notify us of potential conflicts. I hope this saved you some time!