Which company owns MAC address prefix DC:21:B9?

MAC address prefix DC:21:B9 is registered to Sentec Co.Ltd in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with DC:21:B9 has a network interface built by Sentec Co.Ltd.

What is the OUI DC:21:B9?

DC:21:B9 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Sentec Co.Ltd. It covers every address from DC:21:B9:00:00:00 to DC:21:B9:FF:FF:FF, or 16,777,216 addresses in total. It is also written DC-21-B9.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in DC:21:B9:00:00:00 that is DC:21:B9 — 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 Sentec Co.Ltd located?

Sentec Co.Ltd is listed at 10, Baekseokgongdan 1-ro, Seobuk-gu Cheonan-si Chungcheongnam-do KR 31094 in the IEEE OUI registry entry for DC:21:B9. This is the address the organization registered with the IEEE, which may differ from its current operating address.

Sentec Co.Ltd

MAC address prefix DC:21:B9 is registered to Sentec Co.Ltd in the IEEE OUI registry. Any device whose MAC address begins with DC:21:B9 has a network interface built by Sentec 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 DC:21:B9:00:00:00 to DC:21:B9:FF:FF:FF.

OUI prefix: DC:21:B9
Hyphen form: DC-21-B9
MAC range: DC:21:B9:00:00:00 – DC:21:B9:FF:FF:FF
Addresses in block: 16,777,216
Organization: Sentec Co.Ltd
Address: 10, Baekseokgongdan 1-ro, Seobuk-gu Cheonan-si Chungcheongnam-do KR 31094
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.

2018-12-21Assigned to "Sentec Co.Ltd"
archived source →
2026-07-17Assigned to "Sentec Co.Ltd"

Nearby in the registry

The prefixes assigned immediately before and after DC:21:B9:

FAQ

Which company owns MAC address prefix DC:21:B9?: MAC address prefix DC:21:B9 is registered to Sentec Co.Ltd in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with DC:21:B9 has a network interface built by Sentec Co.Ltd.
What is the OUI DC:21:B9?: DC:21:B9 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Sentec Co.Ltd. It covers every address from DC:21:B9:00:00:00 to DC:21:B9:FF:FF:FF, or 16,777,216 addresses in total. It is also written DC-21-B9.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in DC:21:B9:00:00:00 that is DC:21:B9 — 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 Sentec Co.Ltd located?: Sentec Co.Ltd is listed at 10, Baekseokgongdan 1-ro, Seobuk-gu Cheonan-si Chungcheongnam-do KR 31094 in the IEEE OUI registry entry for DC:21:B9. This is the address the organization registered with the IEEE, which may differ from its current operating address.