This is a small tip to change mac address automatically after reboot, it's very useful especially to connect often in hotspots or public networks. i tested in kalilinux 2.0 and ubuntu and works fine.
Open and terminal and type:
put your interface inside like that:
macchanger -r eth0
macchanger -r wlan0
macchanger -r wlan1
macchanger -r wlan2
save the script and make it executeble.
chmod +x /etc/network/if-pre-up.d/changemac
reboot and your interface change the mac address
this is me