Which company owns MAC address prefix 5C:91:FD?

MAC address prefix 5C:91:FD is registered to Jaewoncnc in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 5C:91:FD has a network interface built by Jaewoncnc.

What is the OUI 5C:91:FD?

5C:91:FD is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Jaewoncnc. It covers every address from 5C:91:FD:00:00:00 to 5C:91:FD:FF:FF:FF, or 16,777,216 addresses in total. It is also written 5C-91-FD.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 5C:91:FD:00:00:00 that is 5C:91:FD — 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 Jaewoncnc located?

Jaewoncnc is listed at A-501~507, H-Businesspark, 25 Beobwon-ro11gil, Songpa-gu, Seoul, Korea Seoul KR 05836 in the IEEE OUI registry entry for 5C:91:FD. This is the address the organization registered with the IEEE, which may differ from its current operating address.

Jaewoncnc

MAC address prefix 5C:91:FD is registered to Jaewoncnc in the IEEE OUI registry. Any device whose MAC address begins with 5C:91:FD has a network interface built by Jaewoncnc. 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 5C:91:FD:00:00:00 to 5C:91:FD:FF:FF:FF.

OUI prefix: 5C:91:FD
Hyphen form: 5C-91-FD
MAC range: 5C:91:FD:00:00:00 – 5C:91:FD:FF:FF:FF
Addresses in block: 16,777,216
Organization: Jaewoncnc
Address: A-501~507, H-Businesspark, 25 Beobwon-ro11gil, Songpa-gu, Seoul, Korea Seoul KR 05836
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.

2020-08-05Assigned to "Jaewoncnc"
archived source →
2026-07-17Assigned to "Jaewoncnc"

Nearby in the registry

The prefixes assigned immediately before and after 5C:91:FD:

FAQ

Which company owns MAC address prefix 5C:91:FD?: MAC address prefix 5C:91:FD is registered to Jaewoncnc in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 5C:91:FD has a network interface built by Jaewoncnc.
What is the OUI 5C:91:FD?: 5C:91:FD is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Jaewoncnc. It covers every address from 5C:91:FD:00:00:00 to 5C:91:FD:FF:FF:FF, or 16,777,216 addresses in total. It is also written 5C-91-FD.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 5C:91:FD:00:00:00 that is 5C:91:FD — 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 Jaewoncnc located?: Jaewoncnc is listed at A-501~507, H-Businesspark, 25 Beobwon-ro11gil, Songpa-gu, Seoul, Korea Seoul KR 05836 in the IEEE OUI registry entry for 5C:91:FD. This is the address the organization registered with the IEEE, which may differ from its current operating address.