Which company owns MAC address prefix AC:91:A1?

MAC address prefix AC:91:A1 is registered to Dell Inc. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with AC:91:A1 has a network interface built by Dell Inc..

What is the OUI AC:91:A1?

AC:91:A1 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Dell Inc.. It covers every address from AC:91:A1:00:00:00 to AC:91:A1:FF:FF:FF, or 16,777,216 addresses in total. It is also written AC-91-A1.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in AC:91:A1:00:00:00 that is AC:91:A1 — 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 Dell Inc. located?

Dell Inc. is listed at One Dell Way Round Rock TX US 78682 in the IEEE OUI registry entry for AC:91:A1. This is the address the organization registered with the IEEE, which may differ from its current operating address.

How many MAC prefixes does Dell Inc. own?

Dell Inc. holds 184 OUI prefixes in the IEEE registry, of which AC:91:A1 is one. A device made by Dell Inc. could carry a MAC address from any of them.

Dell Inc.

MAC address prefix AC:91:A1 is registered to Dell Inc. in the IEEE OUI registry. Any device whose MAC address begins with AC:91:A1 has a network interface built by Dell Inc.. 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 AC:91:A1:00:00:00 to AC:91:A1:FF:FF:FF.

OUI prefix: AC:91:A1
Hyphen form: AC-91-A1
MAC range: AC:91:A1:00:00:00 – AC:91:A1:FF:FF:FF
Addresses in block: 16,777,216
Organization: Dell Inc.
Address: One Dell Way Round Rock TX US 78682
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 Dell Inc.

Dell Inc. holds 184 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.

2023-07-11Assigned to "Dell Inc."
archived source →
2026-07-17Assigned to "Dell Inc."

Nearby in the registry

The prefixes assigned immediately before and after AC:91:A1:

FAQ

Which company owns MAC address prefix AC:91:A1?: MAC address prefix AC:91:A1 is registered to Dell Inc. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with AC:91:A1 has a network interface built by Dell Inc..
What is the OUI AC:91:A1?: AC:91:A1 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Dell Inc.. It covers every address from AC:91:A1:00:00:00 to AC:91:A1:FF:FF:FF, or 16,777,216 addresses in total. It is also written AC-91-A1.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in AC:91:A1:00:00:00 that is AC:91:A1 — 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 Dell Inc. located?: Dell Inc. is listed at One Dell Way Round Rock TX US 78682 in the IEEE OUI registry entry for AC:91:A1. This is the address the organization registered with the IEEE, which may differ from its current operating address.
How many MAC prefixes does Dell Inc. own?: Dell Inc. holds 184 OUI prefixes in the IEEE registry, of which AC:91:A1 is one. A device made by Dell Inc. could carry a MAC address from any of them.