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Hyper-v Identical MAC Address Range

Posted on 2013-06-06
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We have 7 new VM Host 2012 Standard servers all running hyper-v.  These hosts and VMs were all installed from scratch, there was no imaging, cloning or copying of images or VMs. When we started bringing up VMs on the last of these servers, we were experiencing erratic connection with VMs on one of the other servers.  After a lot of hair pulling we realized two of the host servers had identical Virtual Switch Address Ranges as shown in the attached image.  

We concluded this is causing a conflict and want to know how we go about changing the address pool on this host.  As the image shows, the MAC pool can be changed, but the warning below says "changing this setting does not affect adaptors already configured. To apply a new setting to an existing adaptor, recreate the network adaptor by removing it and adding it aging"

Exactly what adaptor are the talking about?  Are they saying to remove the adaptor from device manager on the host?  or removing the virtual switch and starting again?  Or removing the adaptor from the VM?

If anyone has a "How To" for correcting this problem it would be greatly appreciated.   Thank you!
VLAN.JPG
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Question by:Tonygret
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Eddie-Lopez earned 2000 total points
ID: 39228103
Hi,

It is refering to the VMs virtual network adapters. You should change you mac address range as needed, remove your VM network adapters, recreate them, and these new adapters will get mac addresses from your new range.

Regards,

Eddie
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Author Comment

by:Tonygret
ID: 39229115
Eddie,

When you say delete the VM network adaptors, do you mean delete the Virtual switch on the host, or logging into each VM and deleting the virtua/ NIC from device manager? Thanks!
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Author Closing Comment

by:Tonygret
ID: 39230247
To clarify the fix for this, here is how it’s done. Log into the Host machine.  Shut down all VMs. Go to the virtual switch manager.  Delete ay Virtual switches you may have created as they all depend on the same MAC Range.  Change the MAC Rage.  

For instance change this Range:
Minimum 00-15-5D-5F-59-00
Maximum   00-15-5D-5F-59-FF
To
Minimum 00-15-5D-5F-60-00
Maximum   00-15-5D-5F-60-FF

Then recreate a new Virtual switch.  Go into the settings of each VM and assign the new VLan switch under Networking.   Start the VMs as usual.  Problem is solved!
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