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Fixed/static MAC addresses for Azure VMs - for software licensing reasons

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Friday, September 7, 2018 11:41 AM | 1 vote

We have a number of Linux VMs in Azure which run a 3rd party application. This software is licensed against the MAC address of the ethernet interface. If the MAC address changes then we can update the license but this can take anywhere from a few hours to a few days as we depend on our supplier to re-issue the licenses.

Is it possible to configure our VMs to have a permanently fixed/static MAC address?

If not, under what circumstances might the MAC address change?

The events which I am assuming could cause a MAC address change are:

  • Stop/Deallocate
  • Redeploy
  • Unplanned Hardware Maintenance Event (Live Migration)
  • Unexpected Downtime
  • Planned Maintenance events

See /en-us/azure/virtual-machines/linux/manage-availability for definitions of the above events.

These VMs are spread across multiple Azure regions to give us some protection against unexpected MAC address changes but we would like to know exactly where we stand and what options there are to prevent this from occurring.

My research so far has led me to these resources, but none are yet conclusive:

Thanks.

All replies (4)

Tuesday, September 18, 2018 9:00 AM ✅Answered | 2 votes

Microsoft Support have responded (September 2018) with the following...

**MAC preservation was fully deployed to all prod public cloud regions, RDFE and NRP on August 2nd, 2016 (8/2/2016). **

**No customer action is required for MAC preservation to be effective for new or existing VMs. This means all management operations (e.g. stop/stopdeallocate/restart/redeploy) against a new or existing VM will preserve the MAC address. The only exceptions are that deleting and recreating the VM from the same disk will not preserve the MAC address, and if you use the Azure static IP feature to set a static IP, the MAC address will be changed when you enable the static IP, will remain the same as long as the same static IP is set, and will change again if you ever change or remove the static IP. Note that setting a static IP address in the guest in TCP/IP properties is still unsupported and should not be done. **

Your Private IP is tagged to your MAC address. So if you make that as static or reserved, you MAC Address will not change.

I then asked if they could confirm whether the MAC address will stay static for these events too?

• Unplanned Hardware Maintenance Event (Live Migration)
• Unexpected Downtime
• Planned Maintenance events

Their response was:

Yes , MAC will not change for below events unless you make your Private IP static.

Friday, September 7, 2018 7:26 PM

This work should already be completed. 

Are you seeing issues with this behavior? 

Monday, September 10, 2018 11:52 PM

Any update on this? 

Wednesday, September 12, 2018 9:11 AM

Hi, I'm still waiting for a definitive and detailed answer, without any "should" - I have a ticket open with Microsoft Support. There are other places where someone has claimed that it's possible but then there are comments that disagree, for example: https://feedback.azure.com/forums/216843-virtual-machines/suggestions/5217933-static-mac-address

This isn't a problem we're experiencing, it's something we want to plan for - so I'm not "seeing issues with this behaviour".

Thanks.