Log in to the RHEV-M Admin Portal. Power off the virtual machine (VM). Select the Network Interface sub-tab for that VM and click “Edit”. Select “Custom MAC address” and change it to the desired value: Update the networking configuration inside the guest with the new MAC address.
In order to migrate, treat PROXOMOX VM as physical machine and do P2V conversion. i.e. the same way we’d convert a physical host. Obtain a P2V iso image, connect it to the guest to be converted in PROXOMOX, and boot the guest under PROXOMOX using the P2V image. The P2V image runs the P2V client.