Which company owns MAC address prefix D4:55:56?

MAC address prefix D4:55:56 is registered to Fiber Mountain Inc. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with D4:55:56 has a network interface built by Fiber Mountain Inc..

What is the OUI D4:55:56?

D4:55:56 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Fiber Mountain Inc.. It covers every address from D4:55:56:00:00:00 to D4:55:56:FF:FF:FF, or 16,777,216 addresses in total. It is also written D4-55-56.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in D4:55:56:00:00:00 that is D4:55:56 — 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 Fiber Mountain Inc. located?

Fiber Mountain Inc. is listed at 700 W Johnson Ave Cheshire CT US 06410 in the IEEE OUI registry entry for D4:55:56. This is the address the organization registered with the IEEE, which may differ from its current operating address.

Fiber Mountain Inc.

MAC address prefix D4:55:56 is registered to Fiber Mountain Inc. in the IEEE OUI registry. Any device whose MAC address begins with D4:55:56 has a network interface built by Fiber Mountain 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 D4:55:56:00:00:00 to D4:55:56:FF:FF:FF.

OUI prefix: D4:55:56
Hyphen form: D4-55-56
MAC range: D4:55:56:00:00:00 – D4:55:56:FF:FF:FF
Addresses in block: 16,777,216
Organization: Fiber Mountain Inc.
Address: 700 W Johnson Ave Cheshire CT US 06410
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 "Fiber Mountain Inc."
archived source →
2026-07-17Assigned to "Fiber Mountain Inc."

Nearby in the registry

The prefixes assigned immediately before and after D4:55:56:

FAQ

Which company owns MAC address prefix D4:55:56?: MAC address prefix D4:55:56 is registered to Fiber Mountain Inc. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with D4:55:56 has a network interface built by Fiber Mountain Inc..
What is the OUI D4:55:56?: D4:55:56 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Fiber Mountain Inc.. It covers every address from D4:55:56:00:00:00 to D4:55:56:FF:FF:FF, or 16,777,216 addresses in total. It is also written D4-55-56.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in D4:55:56:00:00:00 that is D4:55:56 — 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 Fiber Mountain Inc. located?: Fiber Mountain Inc. is listed at 700 W Johnson Ave Cheshire CT US 06410 in the IEEE OUI registry entry for D4:55:56. This is the address the organization registered with the IEEE, which may differ from its current operating address.