For IP addresses there are 10.x.x.x , 192.168.x.x IP address that can be used for private networks. Is there something similar for MAC address of network cards that can be safely used with virtual emulators and to be sure not to collide with any real network card (current or future)? Currently I am using MAC address 52:54:00:12:34:x I guess I got it form some example for qemu usage or similar. Martin