Thank you, researched your answer, you as usual, are always correct and equally as usual, informative.
http://en.wikipedia.org/wiki/Organizationally_unique_identifier
The OUI is normally discussed and represented as a set of octets in hexadecimal notation separated by dashes (i.e., FF-FF-FF) or as a set of octets separated by colons in bit-reversed notation (i.e., FF:FF:FF).[1]
The two least-significant-bits of the second nibble of the first octet of the hexadecimal representation (i.e., the two least significant bits of the first octet) of the OUI are reserved as flag bits for some protocols (e.g., 'M' bit and 'X' bit), flags to indicate whether the address is part of an individual (unicast) or group (multicast) address block (e.g., Individual / Group [I / G] bit or Unicast / Multicast [U / M] bit), flags to indicate whether an address is universally or locally administered (e.g., Universal / Local [U / L] bit), etc., and should not contain the values 1,2,3,5,6,7,9,a, b,d, e, or f, unless these values reflect the true meaning of these flag bits – if the organization that owns the OUI does set one of these bits when creating an identifier, then the value of the second nibble of the first octet changes accordingly in representations of the OUI (e.g., if the hexadecimal value of the second nibble of the first octet is 'C' and the least-significant-bit is set, then the value becomes 'D').
