IEEE Registration Authority mac prefix

The main problem is that those websites have an outdated concept of how OUIs work. Manufacturer prefixes are not always 24 bits long – they used to be in the past, but now IEEE offers both 28-bit and 36-bit prefixes (for a reduced price).

So when you see a 24-bit prefix that is allocated to IEEE itself, that means it's the "base" from which IEEE assigns those longer prefixes. For example, 40-ED-98-3 is assigned to Knox and 40-ED-98-7 is assigned to Vaisala Oyj.

You'll find the real assignments beginning with 40-ED-98 in the OUI-28 (MA-M) registry. There are three vendor prefix registries:

• MA-L: http://standards-oui.ieee.org/oui/oui.txt
• MA-M: http://standards-oui.ieee.org/oui28/mam.txt
• MA-S: http://standards-oui.ieee.org/oui36/oui36.txt

with a web-based search page here (select "All MAC (MA-L, MA-M, MA-S)" as the database).

(It's a very similar situation as with IPv4 "classful" addresses – everyone used to get the same size block, and it turned out that there are not enough possible 'prefixes', and at the same time many manufacturers really need a much smaller block than is offered. So the solution was to designate a block of longer prefixes.)

Some MAC addresses from the Wireshark database

40:ED:98:00:00:00/28    Tsinghua    Tsinghua Tongfang Co., LTD
40:ED:98:10:00:00/28    Guangzho    GuangZhou FiiO Electronics Technology Co.,Ltd
40:ED:98:20:00:00/28    A-Iox       A-Iox Inc.
40:ED:98:30:00:00/28    Knox        Knox Company
40:ED:98:40:00:00/28    Kendrion    Kendrion Kuhnke Automation GmbH
40:ED:98:50:00:00/28    Cape        
40:ED:98:60:00:00/28    Shanghai    Shanghai Broadwan Communications Co.,Ltd
40:ED:98:70:00:00/28    VaisalaO    Vaisala Oyj
40:ED:98:80:00:00/28    Guangzho    Guangzhou Auric Intelligent Technology Co.,Ltd.
40:ED:98:90:00:00/28    Teratron    TeraTron GmbH
40:ED:98:A0:00:00/28    Integrat    Integrated Design Ltd
40:ED:98:B0:00:00/28    SiebertI    Siebert Industrieelektronik GmbH
40:ED:98:C0:00:00/28    Bloomsky    BloomSky,Inc.
40:ED:98:D0:00:00/28    Hangzhou    Hangzhou GANX Technology Co.,Ltd.
40:ED:98:E0:00:00/28    BordaTec    Borda Technology

That is a prefix for a 20-bit sub-block allocated by IEEE. You need to look at the next nybble for company ID in the MAC Address Block Medium (MA-M) list.