Which company owns MAC address prefix A4:21:8A?

MAC address prefix A4:21:8A is registered to Nortel Networks in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with A4:21:8A has a network interface built by Nortel Networks.

What is the OUI A4:21:8A?

A4:21:8A is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Nortel Networks. It covers every address from A4:21:8A:00:00:00 to A4:21:8A:FF:FF:FF, or 16,777,216 addresses in total. It is also written A4-21-8A.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in A4:21:8A:00:00:00 that is A4:21:8A — 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 Nortel Networks located?

Nortel Networks is listed at CARRETERA BASE AEREA # 5850 Zapopan Jalisco MX 44130 in the IEEE OUI registry entry for A4:21:8A. This is the address the organization registered with the IEEE, which may differ from its current operating address.

How many MAC prefixes does Nortel Networks own?

Nortel Networks holds 68 OUI prefixes in the IEEE registry, of which A4:21:8A is one. A device made by Nortel Networks could carry a MAC address from any of them.

Nortel Networks

MAC address prefix A4:21:8A is registered to Nortel Networks in the IEEE OUI registry. Any device whose MAC address begins with A4:21:8A has a network interface built by Nortel Networks. 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 A4:21:8A:00:00:00 to A4:21:8A:FF:FF:FF.

OUI prefix: A4:21:8A
Hyphen form: A4-21-8A
MAC range: A4:21:8A:00:00:00 – A4:21:8A:FF:FF:FF
Addresses in block: 16,777,216
Organization: Nortel Networks
Address: CARRETERA BASE AEREA # 5850 Zapopan Jalisco MX 44130
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 Nortel Networks

Nortel Networks holds 68 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 "Nortel Networks"
archived source →
2026-07-17Assigned to "Nortel Networks"

Nearby in the registry

The prefixes assigned immediately before and after A4:21:8A:

FAQ

Which company owns MAC address prefix A4:21:8A?: MAC address prefix A4:21:8A is registered to Nortel Networks in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with A4:21:8A has a network interface built by Nortel Networks.
What is the OUI A4:21:8A?: A4:21:8A is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Nortel Networks. It covers every address from A4:21:8A:00:00:00 to A4:21:8A:FF:FF:FF, or 16,777,216 addresses in total. It is also written A4-21-8A.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in A4:21:8A:00:00:00 that is A4:21:8A — 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 Nortel Networks located?: Nortel Networks is listed at CARRETERA BASE AEREA # 5850 Zapopan Jalisco MX 44130 in the IEEE OUI registry entry for A4:21:8A. This is the address the organization registered with the IEEE, which may differ from its current operating address.
How many MAC prefixes does Nortel Networks own?: Nortel Networks holds 68 OUI prefixes in the IEEE registry, of which A4:21:8A is one. A device made by Nortel Networks could carry a MAC address from any of them.