Which company owns MAC address prefix 00:21:BB?

MAC address prefix 00:21:BB is registered to Riken Keiki Co., Ltd. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 00:21:BB has a network interface built by Riken Keiki Co., Ltd..

What is the OUI 00:21:BB?

00:21:BB is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Riken Keiki Co., Ltd.. It covers every address from 00:21:BB:00:00:00 to 00:21:BB:FF:FF:FF, or 16,777,216 addresses in total. It is also written 00-21-BB.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 00:21:BB:00:00:00 that is 00:21:BB — and look that prefix up in the IEEE OUI registry. If the second-lowest bit of the first octet is set, the address is locally administered (a randomized or private MAC), which belongs to no manufacturer and will not resolve; modern phones and laptops use these by default on each network.

Where is Riken Keiki Co., Ltd. located?

Riken Keiki Co., Ltd. is listed at 2-7-6 Azusawa Itabashi-Ku Tokyo JP 174-8744 in the IEEE OUI registry entry for 00:21:BB. This is the address the organization registered with the IEEE, which may differ from its current operating address.

Riken Keiki Co., Ltd.

MAC address prefix 00:21:BB is registered to Riken Keiki Co., Ltd. in the IEEE OUI registry. Any device whose MAC address begins with 00:21:BB has a network interface built by Riken Keiki Co., Ltd.. This prefix (the OUI, or Organizationally Unique Identifier) is assigned by the IEEE and is the first three octets of the address — it covers every MAC from 00:21:BB:00:00:00 to 00:21:BB:FF:FF:FF.

OUI prefix: 00:21:BB
Hyphen form: 00-21-BB
MAC range: 00:21:BB:00:00:00 – 00:21:BB:FF:FF:FF
Addresses in block: 16,777,216
Organization: Riken Keiki Co., Ltd.
Address: 2-7-6 Azusawa Itabashi-Ku Tokyo JP 174-8744
Source: IEEE OUI registry

Have a full MAC address? Look it up— we'll also tell you if it's a randomized (private) address rather than a real manufacturer prefix.

Assignment history (2)

The IEEE registry publishes current state only — this is the change record we've kept since we started tracking it daily.

2016-07-29Assigned to "Riken Keiki Co., Ltd."
archived source →
2026-07-17Assigned to "Riken Keiki Co., Ltd."

Nearby in the registry

The prefixes assigned immediately before and after 00:21:BB:

FAQ

Which company owns MAC address prefix 00:21:BB?: MAC address prefix 00:21:BB is registered to Riken Keiki Co., Ltd. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 00:21:BB has a network interface built by Riken Keiki Co., Ltd..
What is the OUI 00:21:BB?: 00:21:BB is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Riken Keiki Co., Ltd.. It covers every address from 00:21:BB:00:00:00 to 00:21:BB:FF:FF:FF, or 16,777,216 addresses in total. It is also written 00-21-BB.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 00:21:BB:00:00:00 that is 00:21:BB — and look that prefix up in the IEEE OUI registry. If the second-lowest bit of the first octet is set, the address is locally administered (a randomized or private MAC), which belongs to no manufacturer and will not resolve; modern phones and laptops use these by default on each network.
Where is Riken Keiki Co., Ltd. located?: Riken Keiki Co., Ltd. is listed at 2-7-6 Azusawa Itabashi-Ku Tokyo JP 174-8744 in the IEEE OUI registry entry for 00:21:BB. This is the address the organization registered with the IEEE, which may differ from its current operating address.