Which company owns MAC address prefix 00:21:91?

MAC address prefix 00:21:91 is registered to D-Link Corporation in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 00:21:91 has a network interface built by D-Link Corporation.

What is the OUI 00:21:91?

00:21:91 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to D-Link Corporation. It covers every address from 00:21:91:00:00:00 to 00:21:91:FF:FF:FF, or 16,777,216 addresses in total. It is also written 00-21-91.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 00:21:91:00:00:00 that is 00:21:91 — 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 D-Link Corporation located?

D-Link Corporation is listed at NO.289, Sinhu 3rd Rd., Neihu District, Taipei City TW 114 in the IEEE OUI registry entry for 00:21:91. This is the address the organization registered with the IEEE, which may differ from its current operating address.

How many MAC prefixes does D-Link Corporation own?

D-Link Corporation holds 27 OUI prefixes in the IEEE registry, of which 00:21:91 is one. A device made by D-Link Corporation could carry a MAC address from any of them.

D-Link Corporation

MAC address prefix 00:21:91 is registered to D-Link Corporation in the IEEE OUI registry. Any device whose MAC address begins with 00:21:91 has a network interface built by D-Link Corporation. 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 00:21:91:00:00:00 to 00:21:91:FF:FF:FF.

OUI prefix: 00:21:91
Hyphen form: 00-21-91
MAC range: 00:21:91:00:00:00 – 00:21:91:FF:FF:FF
Addresses in block: 16,777,216
Organization: D-Link Corporation
Address: NO.289, Sinhu 3rd Rd., Neihu District, Taipei City TW 114
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.

Other prefixes from D-Link Corporation

D-Link Corporation holds 27 OUI prefixes in total. A device with this exact prefix could just as well carry any of these:

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 "D-Link Corporation"
archived source →
2026-07-17Assigned to "D-Link Corporation"

Nearby in the registry

The prefixes assigned immediately before and after 00:21:91:

FAQ

Which company owns MAC address prefix 00:21:91?: MAC address prefix 00:21:91 is registered to D-Link Corporation in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 00:21:91 has a network interface built by D-Link Corporation.
What is the OUI 00:21:91?: 00:21:91 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to D-Link Corporation. It covers every address from 00:21:91:00:00:00 to 00:21:91:FF:FF:FF, or 16,777,216 addresses in total. It is also written 00-21-91.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 00:21:91:00:00:00 that is 00:21:91 — 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 D-Link Corporation located?: D-Link Corporation is listed at NO.289, Sinhu 3rd Rd., Neihu District, Taipei City TW 114 in the IEEE OUI registry entry for 00:21:91. This is the address the organization registered with the IEEE, which may differ from its current operating address.
How many MAC prefixes does D-Link Corporation own?: D-Link Corporation holds 27 OUI prefixes in the IEEE registry, of which 00:21:91 is one. A device made by D-Link Corporation could carry a MAC address from any of them.