Which company owns MAC address prefix D4:40:D0?

MAC address prefix D4:40:D0 is registered to OCOSMOS Co., LTD in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with D4:40:D0 has a network interface built by OCOSMOS Co., LTD.

What is the OUI D4:40:D0?

D4:40:D0 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to OCOSMOS Co., LTD. It covers every address from D4:40:D0:00:00:00 to D4:40:D0:FF:FF:FF, or 16,777,216 addresses in total. It is also written D4-40-D0.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in D4:40:D0:00:00:00 that is D4:40:D0 — 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 OCOSMOS Co., LTD located?

OCOSMOS Co., LTD is listed at (Tamnip-Dong) #1, 263-1 Techno 2-Ro Yuseong-Gu Daejeon Daejeon KR 34026 in the IEEE OUI registry entry for D4:40:D0. This is the address the organization registered with the IEEE, which may differ from its current operating address.

OCOSMOS Co., LTD

MAC address prefix D4:40:D0 is registered to OCOSMOS Co., LTD in the IEEE OUI registry. Any device whose MAC address begins with D4:40:D0 has a network interface built by OCOSMOS 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 D4:40:D0:00:00:00 to D4:40:D0:FF:FF:FF.

OUI prefix: D4:40:D0
Hyphen form: D4-40-D0
MAC range: D4:40:D0:00:00:00 – D4:40:D0:FF:FF:FF
Addresses in block: 16,777,216
Organization: OCOSMOS Co., LTD
Address: (Tamnip-Dong) #1, 263-1 Techno 2-Ro Yuseong-Gu Daejeon Daejeon KR 34026
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.

2020-05-13Assigned to "OCOSMOS Co., LTD"
archived source →
2026-07-17Assigned to "OCOSMOS Co., LTD"

Nearby in the registry

The prefixes assigned immediately before and after D4:40:D0:

FAQ

Which company owns MAC address prefix D4:40:D0?: MAC address prefix D4:40:D0 is registered to OCOSMOS Co., LTD in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with D4:40:D0 has a network interface built by OCOSMOS Co., LTD.
What is the OUI D4:40:D0?: D4:40:D0 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to OCOSMOS Co., LTD. It covers every address from D4:40:D0:00:00:00 to D4:40:D0:FF:FF:FF, or 16,777,216 addresses in total. It is also written D4-40-D0.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in D4:40:D0:00:00:00 that is D4:40:D0 — 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 OCOSMOS Co., LTD located?: OCOSMOS Co., LTD is listed at (Tamnip-Dong) #1, 263-1 Techno 2-Ro Yuseong-Gu Daejeon Daejeon KR 34026 in the IEEE OUI registry entry for D4:40:D0. This is the address the organization registered with the IEEE, which may differ from its current operating address.