Playing with Ethernet Organisation Unique Identifiers

Ethernet remains the mostly widely used LAN technology. Since the invention of Ethernet in the early 1970s, the only part of the specification that remains unchanged is the format of the addresses. Ethernet was the first Local Area Network technology to introduce 48 bits long addresses. These addresses, sometimes called MAC addresses, are divided in two parts. The high order bits contain an Organisation Unique Identifier which identifies a company or organisation. Any organisation can register a OUI from which it can allocate Ethernet addresses. Most OUIs identify companies selling networking equipment, but there are a few exceptions.

The full list of allocated OUIs is maintained by IEEE and available from A cleaner version of this list is available from Some system administrators and networking vendors use this list to identify rogue Ethernet or WiFi adapters in their networks or try to debug problems. Knowing that some Ethernet and WiFi adapters can be configured to use any MAC address instead of the one stored in their ROM, some users have played games by using MAC addresses from unusual OUIs. Popular examples include:

00-20-91   (hex)		J125, National Security Agency
002091     (base 16)		J125, National Security Agency
	   	 		9800 Savage Road
				FT. Meade  MD  20755-6000

Which can cause surpises in government of military networks…

00-C0-1E   (hex)		LA Francaise DES Jeux
00C01E     (base 16)		LA Francaise DES Jeux
	   	 		Centre de Roussy/DTI

This is the French lotery company…

00-E0-7E   (hex)		Walt Disney Imagineering
00E07E     (base 16)		Walt Disney Imagineering
	   	 		1401 Flower ST.
				Glendale  CA  91221

There are probably other unexpected organisations that own an OUI.

Written on December 12, 2017