So thier network cards are at least somewhat active. It is a bit hidden at the end of the first sentence (it would belong into the title), but he wants computers active enough to react to WakeOnLan orders. You can't it's like you saying you want to see a 747 fly that has no fuel in it to take off. How can I make a list of these machines and their MAC addresses in C# ? I don't know their IP addresses - I want ALL these machines that WOULD show up in the network folder IF they were turned on. I can find a lots of samples finding MAC address of the local machine and machines on-line but I need a list of MAC addresses on machines NOT turned on (but prepared for WakeOnLAN).