What MAC Address to Give the Router when Declaring Dedicated IP with DHCP?

I want to give a dedicated IP to the known devices in the LAN so that all known devices are in a range between .20 and .99 (.20 to .39 for printers, phones etc.; .40 to .69 for mobile phones; .70 to .99 for computeres; etc.) and the free range for unknown devices get an IP in the range of .100 to .199 etc. Now Apple devices have a problem: the MAC shown in the info of the device is not the same as the MAC the router sees ... What MAC has to be declared to the router to address the Apple devices? Btw: it is not "fixed IP" as the device connects via DHCP to the router – and if the router detects the MAC it give the dedicated IP; otherwise it does not distribute this IP to a different device.