This week I answered to this question to someone on Twitter and then I saw it again at VMware internal forums.

– How to persist MAC Address during recompose operations?

Persisting MAC address during Linked Clone recompose operations is critical for many organizations. The ability to persist MAC address is directly related to the ability to automatically place desktops in specific VLANs, license applications that require MAC address registration, re-register an already existing IP address that has been recomposed with an existing MAC address automatically via DNS and DHCP, or even if for any reason you require to spoof MAC addresses in your network (yes, I have seen this one).

Prior to VMware View 5.0 only the Linked Clone refresh operation would maintain MAC address because refresh operation is actually a snapshot rever-back operation. After a desktop is customized, the VM is shutdown and a snapshot is taken for this VM (vmname-checkpoint.vmdk) and then the VM is powered on for inital use.

When a refresh operation is then triggered the VM is shutdown and reverted back to the snapshot maintaining the MAC address for the VM. Please note that this behavior was changed in VMware View 4.5, where prior to that the MAC address would also change for refresh operations.

What about Linked Clone recompose operations?

Starting with VMware View 5.1 all Linked Clone recompose operations will preserve the MAC address for both assigned and unassigned VMs. Prior to VMware View 5.1, Linked Clone recompose operations preserved the VM MAC address of assigned VMs only, while unassigned VMs would be recreated and assigned new MAC addresses.

That behavior is particularly useful for non-persistent desktops in floating desktop pools and will also persist MAC addresses when re-balancing Linked Clones across datastores.

This article was first published by Andre Leibovici (@andreleibovici) at myvirtualcloud.net.