Tiniest mac changer, keeps your manufacturer hardware prefix.

mac-changer.sh

#!/bin/bash

if [ "$#" -lt 1 ]; then
	echo "Usage: $0 <interface label>"
else
	NEW_MAC=$(ip link show $1 | tail -n1 | grep -Po 'link/ether \K[[:xdigit:]:]{8,8}')

	for i in {0..2}; do
		printf -v BYTE "%02x" $(($RANDOM%256))
		NEW_MAC=$NEW_MAC:$BYTE
	done

	ip link set dev $1 address $NEW_MAC
fi