Send hosts MAC address to DHCP server?

Does anyone know why this setting is always grayed-out in my Win7 guest? (Parallels for Mac 5.0.9344) The description of the feature sounds like it would solve my problem at home, where my wireless AP will not give out two IP address (one to my Mac, one to my guest) when using bridged networking. Using NAT networking fixes this, of course, but for other reasons I want to stay in bridged mode at work and not have to switch to NAT at home just to get my guest talking on the network.

Anyway, the "Send host's MAC address to DHCP server" looks promising, but no matter what I change it never becomes active and "check-able." Is this feature not really implemented, yet, or am I doing something wrong?

 

It is likely because this option may no be edited while the VM is running. Please shutdown it and try to edit again

 

I should have specified in the original post... the setting is grayed-out whether the VM is running or completely shut down.

 

Try to explicitly select "AirPort", default won't work