OK, that's what I thought. There is an issue currently with how VMware Tools 4.1 reacts to MAC address change in this specific combination, Windows 2008 R2 and VMXNET3. The issue with VMware Tools causes Windows to create new adaptor in response to MAC address change, and as all newly created adaptors, it is set to DHCP.
Any other Windows version or network adaptor type combinations are not exhibiting the same behavior, and guest OS adaptor and its settings remain the same when MAC address is changed.
This was actually reported even in v4
, as this affects full VM restore and replication in a similar manner.
I recommend changing adaptor type on source VM to any other. Default network adaptor for Windows 2008 R2 is still E1000 in vSphere 4.1, but you can use any other type as well, as the issue is only specific to VMXNET3. Please also note, that we had recommendation posted here from one customer suggesting to only use VMXNET3 for performance testing in lab conditions for now, as it is not quite ready for production yet (and some topics on VMware Communities actually prove that).
If you want to stick with VMXNET3, other option would be to assign static MAC address in production VM settings, this also prevents this issue as our product will preserve that as a part of backup.