Duplicate MACs cause ePO to see different machines as the same node even if the GUID is different, so the workaround is to set ePO to ignore MACs when communicating with an "unknown" machine.
The "HKEY_LOCAL_MACHINE\SOFTWARE\Network Associates\ePolicy Orchestrator\Options\DisableMACSearch" Key is mentioned to be left in place long enough to have all your nodes communicate with the ePO server and then removed, although I've left it in place indefinitely because our vpn software tends to cause duplicate MACs, causing issues with duplicate MACs causing duplicate GUIDs.
I've left it in place indefinitely because our vpn software tends to cause duplicate MACs, causing issues with duplicate MACs causing duplicate GUIDs.
ePO actually has a separate mechanism for dealing with VPN connections - it's effectively a "targetted DisableMacSearch" function that is only applied to certain MAC address families. Have a look at KB52949 for more details.
We really don't recommend leaving the global DisableMacSearch function enabled permanently - this should give you the best of both worlds