devilsdean writes "What happens when we run out of MAC Addresses? IP v4 provides a 32 bit address, ip v6 provides a 128 bit address, while MAC provides a 48 bit address. MAC addresses are broken up into 24 bits for the OUI and 24 bits for the host. so that provides 2^24th unique mac addresses. If every client on the Internet must have a unique MAC address, what replaces MAC like IPv6 will replace IPv4."