How to replicate MAC address during vNIC upgrade or P2V

When you upgrade a virtual machine's virtual network adapter you actually remove the old vNIC and then recreate a new vNIC and this new vNIC would have a new MAC address. In a different scenario during P2V we delete the old physical NICs and add new vNICs this also changes MAC address.
What if you have an application that is tied to the MAC address for licensing. In these situations you will have to replicate the old MAC address to the new vNIC. 

In case of vNIC upgrade it can be simply done from edit VM settings(can be done only for VMware reserved MAC address range i.e. 00:50:56:XX:YY:ZZ , where XX is a valid hexadecimal number between 00 and 3F, and YY and ZZ are valid hexadecimal numbers between 00 and FF) however to replicate the MAC address in case of P2V, you will have to edit the vmname.vmx file (as the physical server's NIC MAC address will be other than VMware reserved address range).

Note: If the MAC addressed is prefixed with 00:50:56 but it is outside of the [00-3F]:XX:XX range, it is still considered invalid and the VM will fail to power on.

Make sure you noted down the MAC address of old network card before removing it, there are many ways of checking the MAC address like using ipconfig or getmac command etc.

In case of vNIC upgrade: Open VM settings, select desired vNIC => Select manual and then change xx:xx:xx (xx:xx:xx is just to highlight by default its blank after 00:50:56:  ) with the required number.

Only in few cases like P2V where MAC address range is different from VMware approved range you will have edit the .vmx file as you can’t be replicate that MAC from VM settings.

• Shut down the virtual machine.
• Now right-click the virtual machine and click Remove from Inventory. 
• Download the .vmx configuration file for the virtual machine to your desktop using the Datastore Browser and open it using text editor 
• Now replace this line ethernet0.generatedAddress = "00:50:56:xx:xx:xx" with 

ethernetN.addressType = "static"
ethernetN.checkMACAddress = "false"
ethernetN.address = "xx:xx:xx:xx:xx:xx"

Where N is the vNIC number (Network Adapter 1 -> ethernet0 Network Adapter 2 -> ethernet1 etc.) and XX:XX:XX:XX:XX:XX is the new desired MAC address for the virtual machine.

Note: For more info, refer to VMware vSphere Documentation Center, KB# 219, 2035707

Other Thoughts: Yes of-course you can spoof the MAC address from inside the OS too but the problem is, in that case you will have to set MAC address change security policy to accept from vSwitch properties,

This is what that most of the VMware admins don't want to change.

That's it.... :)