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Will a VM's MAC Address Change if it migrates from one node to another?

  • 8 December 2022
  • 2 replies
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Howdy,

We have a VM that is licensed by hardware. We needed to do some after hours work on the network so we shut down the VMs and cluster. When it came back online the software unlicensed itself.

Looking at the 4th bullet point has be wondering from this KB: How to set MAC address for VM NIC on AHV cluster

Not finding much luck to my question but I was curious if the NIC MAC changes if it moved from one node to another when it came back online?

Also, is there anyway to see if the system had a prior MAC NIC?

Thanks,

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Best answer by jangliss_ci 8 December 2022, 16:27

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Thanks that is kind of what I was thinking also this helps, but still left with the conundrum.

The MAC address on a NIC will remain the same after a shutdown and bringing it back up on another node. It’d be terrible behavior if the MAC changed if you migrated host after a shutdown.

The comment in bullet point 4 is basically saying if you have multiple protection domains, say 2 separate clusters in 2 different data centers, and you move between the two it’d stay the same, but if you were to clone the VM it’d generate a new MAC address.

Depending on the software, and what hardware it’s using to fingerprint the “server”, it might be looking at other things like the computer’s serial number, memory serial numbers, etc.  I did a quick test on a windows machine, after shutdown and power up on a different host mac the bios serial number stayed the same, there is no memory serial numbers, and CPU serial numbers haven’t existing since Intel PIII. 

I’d imagine the fingerprinting is going based on some additional hardware.