lanscan and look up the relevant info. For example:
$ lanscan Hardware Station Dev Hardware Net-Interface NM Encapsulation Mjr Path Address lu State NameUnit State ID Methods Num 2.0.2 0x08000935C99D 0 UP lan0 UP 4 ETHER 52Note: HP systems remove the :'s from the MAC address. In the case of this system, the MAC address is 08:00:09:35:C9:9D.