Knife VSphere plugin we use to change the MAC address on the cloned VM's network adapter.

vsphere-plugin-mac-change.rb

require 'rbvmomi'

class KnifeVspherePlugin
  def data=(cplugin_data)
    @mac_address = cplugin_data
  end

  def reconfig_vm(target_vm)
    if (!@mac_address)
      abort ("MAC address not provided")
    end

    card = target_vm.config.hardware.device.grep(RbVmomi::VIM::VirtualEthernetCard).find { |x| x.deviceInfo.label == "Network adapter 1" } or
      abort "Can't find source network card to customize"

    card.macAddress = @mac_address

    card_spec = {
      :deviceChange => [
                        {
                          :operation => :edit,
                          :device => card
                        }
                       ]
    }
    target_vm.ReconfigVM_Task(:spec => card_spec).wait_for_completion
    puts "Finished Changing the MAC to #{@mac_address}"
  end

end