Which company owns MAC address prefix C4:EF:DA?

MAC address prefix C4:EF:DA is registered to Honeywell in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with C4:EF:DA has a network interface built by Honeywell.

What is the OUI C4:EF:DA?

C4:EF:DA is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Honeywell. It covers every address from C4:EF:DA:00:00:00 to C4:EF:DA:FF:FF:FF, or 16,777,216 addresses in total. It is also written C4-EF-DA.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in C4:EF:DA:00:00:00 that is C4:EF:DA — 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 Honeywell located?

Honeywell is listed at 9680 Old Bailes Rd, Fort Mill, SC 29707 Fort Mill SC US 29707 in the IEEE OUI registry entry for C4:EF:DA. This is the address the organization registered with the IEEE, which may differ from its current operating address.

How many MAC prefixes does Honeywell own?

Honeywell holds 4 OUI prefixes in the IEEE registry, of which C4:EF:DA is one. A device made by Honeywell could carry a MAC address from any of them.

Honeywell

MAC address prefix C4:EF:DA is registered to Honeywell in the IEEE OUI registry. Any device whose MAC address begins with C4:EF:DA has a network interface built by Honeywell. 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 C4:EF:DA:00:00:00 to C4:EF:DA:FF:FF:FF.

OUI prefix: C4:EF:DA
Hyphen form: C4-EF-DA
MAC range: C4:EF:DA:00:00:00 – C4:EF:DA:FF:FF:FF
Addresses in block: 16,777,216
Organization: Honeywell
Address: 9680 Old Bailes Rd, Fort Mill, SC 29707 Fort Mill SC US 29707
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 Honeywell

Honeywell holds 4 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.

2022-07-11Assigned to "Honeywell"
archived source →
2026-07-17Assigned to "Honeywell"

Nearby in the registry

The prefixes assigned immediately before and after C4:EF:DA:

FAQ

Which company owns MAC address prefix C4:EF:DA?: MAC address prefix C4:EF:DA is registered to Honeywell in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with C4:EF:DA has a network interface built by Honeywell.
What is the OUI C4:EF:DA?: C4:EF:DA is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Honeywell. It covers every address from C4:EF:DA:00:00:00 to C4:EF:DA:FF:FF:FF, or 16,777,216 addresses in total. It is also written C4-EF-DA.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in C4:EF:DA:00:00:00 that is C4:EF:DA — 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 Honeywell located?: Honeywell is listed at 9680 Old Bailes Rd, Fort Mill, SC 29707 Fort Mill SC US 29707 in the IEEE OUI registry entry for C4:EF:DA. This is the address the organization registered with the IEEE, which may differ from its current operating address.
How many MAC prefixes does Honeywell own?: Honeywell holds 4 OUI prefixes in the IEEE registry, of which C4:EF:DA is one. A device made by Honeywell could carry a MAC address from any of them.