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Hi,

Last week, I restored a full VM whose IP is DHCP assigned, but fount out that, after the restore, its MAC address was changed.

According to support, it’s normal because the MAC address is assigned by VMware, so, unless the original VM was deleted prior to the restore, VMware would always assign a different MAC address to the restored VM.

The issue is, users who ask for a VM restore don’t usually want to delete the original one prior to the restore, not until they check the restored one to see if it works…

Strange thing to me is that, in Netbackup, when I do a full VM restore, the MAC address is not changed, regardless the original one is present or not…

 

So, I just wonder if there is a hidden switch somewhere in the restore setting that does the trick ? Or it is indeed the case that Commvault works differently to Netbackup in this scenario ?

 

Thanks,

Kelvin

 

Kelvin,

When we restore a VM and there are no changes in the networking config we are just pushing the same network settings back to the VM.  What we see there is that VMware detects two VMs with the same mac address and automatically changes the mac address of the newly created VM.  One thing that may be relevant is the type of the network that is involved here?  Is this a DVSwitch, a standard switch or NSX?  From that we can take a bit of a deeper look and see if there is something that we can do.  

 

 

Hi Henry,

Thanks for the reply. However, what really makes me wonder is why VMware doesn’t change the MAC address of a VM restored by Netbackup? It can’t be possibly the case that VMware distinguish between Commvault and Netbackup ? 

 

 

Regards,

 

Kelvin

Kelvin, 

The article that you linked isn’t saying the exact same thing here.  Netbackup doesn’t change the mac address, and because they don’t change the mac address, VMware detects the conflict and changes the mac address.  While VMware changes the mac address an alarm is generated that says a mac address conflict was detected. 

The article also states “If there is a mac address conflict, VMware eventually changes the mac address of the new VM”.  In my experience, this isn’t “eventually” but “immediately” and the changing of the mac address and the generation of the alarm happen simultaneously.

 

When Commvault restores a VM we do the same thing (assuming no network reconfiguration as part of the restore)  we put the vm back with the exact same network settings, but we know that there can be a mac address conflict, and we also know that you requested a VM to be restored.  So since this is a known reason for the mac address conflict and this isn’t a situation of someone trying to spoof a mac address; We clear the alarm on the restored VM before we complete the restore.  

 

So are you actually seeing a situation of 2 vms registered in vCenter on the same switch that have the same Mac address?  if so please let me know the details of the network configuration; and I’ll take a look, but my experience around this area has been that VMware doesn’t allow it.

 

 

Hi Henry,

I just did a VMware test restore by Netbackup, and you were right :thumbsup_tone4:  the MAC address of the restore VM was too changed by VMware.

 

Thanks very much for the explanation!

 

Kelvin

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