VM MAC address changes when changing port group after migrating VM to another vCenter and back

Products

• VMware vCenter Server

Issue/Introduction

• The VM's MAC address changed when its port group was modified.
  
  
• The following event was recorded when changing the VM's port group
  
  Changed MAC address from 00:50:56:##:##:## to 00:50:56:##:##:## for adapter <portgroup name> for <vm name>
  
  
• /var/log/vmware/vpxd/vpxd.log contains entries like
  
  [timestamp] info vpxd[52300] [Originator@6876 sub=InvtId opID=<opID>] VM <VM name> has conflict mac [00:50:56:##:##:##] with deny list, new mac [00:50:56:##:##:##].
  
  
  
• The affected virtual machine was previously moved to another vCenter using Cross vCenter vMotion and was later moved back to the original vCenter.

Environment

vCenter Server 7.x

Cause

MAC addresses of VMs moved to another vCenter by Cross vCenter vMotion are tracked on a deny list.
In vCenter Server 7.x, when a VM moved by Cross vCenter vMotion is moved back to the original vCenter, its MAC address is not removed from the deny list.
When the port group is changed for such a VM, a conflict with the deny list may be detected and the MAC address can be automatically changed.

Resolution

This issue is resolved in vCenter Server 8.0 and later.
MAC addresses are correctly removed from the deny list when a VM is migrated back to the original vCenter.

Note: MAC address entries that remained in the deny list while running vCenter Server 7.x are not removed automatically after an upgrade to vCenter Server 8.x.