What is the format of a valid MAC address ?

A normal MAC address looks like this: 00:09:5B:EC:EE:F2. It is composed of six octets. The first half (00:09:5B) of each MAC address is known as the Organizationally Unique Identifier (OUI). Simply put, it is the card manufacturer. The second half (EC:EE:F2) is known as the extension identifier and is unique to each network card within the specific OUI. Many access points will ignore MAC addresses with invalid OUIs. So make sure you use a valid OUI code when you make up MAC addresses. Otherwise, your packets may be ignored by the Access Point. The current list of OUIs may be found here. Make sure that that the last bit of first octet is 0. This corresponds to unicast addresses. If it is set to 1, this indicates a group address, which is normally exclusively used by multicast traffic. MAC addresses with a source set to multicast are invalid and will be dropped. Examples of valid OUIs: 00:1B:23, 08:14:43, AA:00:04 because 0, 8 and A are even Examples of invalid OUIs: 01:1B:23, 03:23:32 ... more