Which company owns MAC address prefix AC:E9:AA?

MAC address prefix AC:E9:AA is registered to Hay Systems Ltd in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with AC:E9:AA has a network interface built by Hay Systems Ltd.

What is the OUI AC:E9:AA?

AC:E9:AA is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Hay Systems Ltd. It covers every address from AC:E9:AA:00:00:00 to AC:E9:AA:FF:FF:FF, or 16,777,216 addresses in total. It is also written AC-E9-AA.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in AC:E9:AA:00:00:00 that is AC:E9:AA — 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 Hay Systems Ltd located?

Hay Systems Ltd is listed at Watermark Livingston West Lothian GB EH54 7EG in the IEEE OUI registry entry for AC:E9:AA. This is the address the organization registered with the IEEE, which may differ from its current operating address.

Hay Systems Ltd

MAC address prefix AC:E9:AA is registered to Hay Systems Ltd in the IEEE OUI registry. Any device whose MAC address begins with AC:E9:AA has a network interface built by Hay Systems 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 AC:E9:AA:00:00:00 to AC:E9:AA:FF:FF:FF.

OUI prefix: AC:E9:AA
Hyphen form: AC-E9-AA
MAC range: AC:E9:AA:00:00:00 – AC:E9:AA:FF:FF:FF
Addresses in block: 16,777,216
Organization: Hay Systems Ltd
Address: Watermark Livingston West Lothian GB EH54 7EG
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.

2016-07-29Assigned to "Hay Systems Ltd"
archived source →
2026-07-17Assigned to "Hay Systems Ltd"

Nearby in the registry

The prefixes assigned immediately before and after AC:E9:AA:

FAQ

Which company owns MAC address prefix AC:E9:AA?: MAC address prefix AC:E9:AA is registered to Hay Systems Ltd in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with AC:E9:AA has a network interface built by Hay Systems Ltd.
What is the OUI AC:E9:AA?: AC:E9:AA is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Hay Systems Ltd. It covers every address from AC:E9:AA:00:00:00 to AC:E9:AA:FF:FF:FF, or 16,777,216 addresses in total. It is also written AC-E9-AA.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in AC:E9:AA:00:00:00 that is AC:E9:AA — 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 Hay Systems Ltd located?: Hay Systems Ltd is listed at Watermark Livingston West Lothian GB EH54 7EG in the IEEE OUI registry entry for AC:E9:AA. This is the address the organization registered with the IEEE, which may differ from its current operating address.