MicrosoftAprilYoho Is there any specific doc or procedure you are referring to? From https://docs.microsoft.com/en-us/azure/virtual-network/virtual-network-network-interface, you can see the official doc says:
"
Azure assigns a MAC address to the network interface only after the network interface is attached to a virtual machine and the virtual machine is started the first time. You cannot specify the MAC address that Azure assigns to the network interface. The MAC address remains assigned to the network interface until the network interface is deleted or the private IP address assigned to the primary IP configuration of the primary network interface is changed. To learn more about IP addresses and IP configurations, see https://docs.microsoft.com/en-us/azure/virtual-network/ip-services/virtual-network-network-interface-addresses
"
