Which company owns MAC address prefix A4:45:CD?

MAC address prefix A4:45:CD is registered to IoT Diagnostics in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with A4:45:CD has a network interface built by IoT Diagnostics.

What is the OUI A4:45:CD?

A4:45:CD is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to IoT Diagnostics. It covers every address from A4:45:CD:00:00:00 to A4:45:CD:FF:FF:FF, or 16,777,216 addresses in total. It is also written A4-45-CD.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in A4:45:CD:00:00:00 that is A4:45:CD — 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 IoT Diagnostics located?

IoT Diagnostics is listed at 10052 Commerce Park Drive Cincinnati OH US 45246 in the IEEE OUI registry entry for A4:45:CD. This is the address the organization registered with the IEEE, which may differ from its current operating address.

IoT Diagnostics

MAC address prefix A4:45:CD is registered to IoT Diagnostics in the IEEE OUI registry. Any device whose MAC address begins with A4:45:CD has a network interface built by IoT Diagnostics. 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 A4:45:CD:00:00:00 to A4:45:CD:FF:FF:FF.

OUI prefix: A4:45:CD
Hyphen form: A4-45-CD
MAC range: A4:45:CD:00:00:00 – A4:45:CD:FF:FF:FF
Addresses in block: 16,777,216
Organization: IoT Diagnostics
Address: 10052 Commerce Park Drive Cincinnati OH US 45246
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.

2019-07-04Assigned to "IoT Diagnostics"
archived source →
2026-07-17Assigned to "IoT Diagnostics"

Nearby in the registry

The prefixes assigned immediately before and after A4:45:CD:

FAQ

Which company owns MAC address prefix A4:45:CD?: MAC address prefix A4:45:CD is registered to IoT Diagnostics in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with A4:45:CD has a network interface built by IoT Diagnostics.
What is the OUI A4:45:CD?: A4:45:CD is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to IoT Diagnostics. It covers every address from A4:45:CD:00:00:00 to A4:45:CD:FF:FF:FF, or 16,777,216 addresses in total. It is also written A4-45-CD.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in A4:45:CD:00:00:00 that is A4:45:CD — 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 IoT Diagnostics located?: IoT Diagnostics is listed at 10052 Commerce Park Drive Cincinnati OH US 45246 in the IEEE OUI registry entry for A4:45:CD. This is the address the organization registered with the IEEE, which may differ from its current operating address.