Which company owns MAC address prefix C8:66:5D?

MAC address prefix C8:66:5D is registered to Extreme Networks, Inc. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with C8:66:5D has a network interface built by Extreme Networks, Inc..

What is the OUI C8:66:5D?

C8:66:5D is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Extreme Networks, Inc.. It covers every address from C8:66:5D:00:00:00 to C8:66:5D:FF:FF:FF, or 16,777,216 addresses in total. It is also written C8-66-5D.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in C8:66:5D:00:00:00 that is C8:66:5D — 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 Extreme Networks, Inc. located?

Extreme Networks, Inc. is listed at 2121 RDU Center Drive Morrisville NC US 27560 in the IEEE OUI registry entry for C8:66:5D. This is the address the organization registered with the IEEE, which may differ from its current operating address.

How many MAC prefixes does Extreme Networks, Inc. own?

Extreme Networks, Inc. holds 98 OUI prefixes in the IEEE registry, of which C8:66:5D is one. A device made by Extreme Networks, Inc. could carry a MAC address from any of them.

Extreme Networks, Inc.

MAC address prefix C8:66:5D is registered to Extreme Networks, Inc. in the IEEE OUI registry. Any device whose MAC address begins with C8:66:5D has a network interface built by Extreme Networks, 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 C8:66:5D:00:00:00 to C8:66:5D:FF:FF:FF.

OUI prefix: C8:66:5D
Hyphen form: C8-66-5D
MAC range: C8:66:5D:00:00:00 – C8:66:5D:FF:FF:FF
Addresses in block: 16,777,216
Organization: Extreme Networks, Inc.
Address: 2121 RDU Center Drive Morrisville NC US 27560
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 Extreme Networks, Inc.

Extreme Networks, Inc. holds 98 OUI prefixes in total. A device with this exact prefix could just as well carry any of these:

Assignment history (4)

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 "Aerohive Networks Inc."
archived source →
2020-03-21Renamed from "Aerohive Networks Inc." to "Extreme Networks, Inc."
archived source →
2024-02-15Renamed from "Extreme Networks, Inc." to "Extreme Networks Headquarters"
archived source →
2026-07-17Assigned to "Extreme Networks, Inc."

Nearby in the registry

The prefixes assigned immediately before and after C8:66:5D:

FAQ

Which company owns MAC address prefix C8:66:5D?: MAC address prefix C8:66:5D is registered to Extreme Networks, Inc. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with C8:66:5D has a network interface built by Extreme Networks, Inc..
What is the OUI C8:66:5D?: C8:66:5D is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Extreme Networks, Inc.. It covers every address from C8:66:5D:00:00:00 to C8:66:5D:FF:FF:FF, or 16,777,216 addresses in total. It is also written C8-66-5D.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in C8:66:5D:00:00:00 that is C8:66:5D — 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 Extreme Networks, Inc. located?: Extreme Networks, Inc. is listed at 2121 RDU Center Drive Morrisville NC US 27560 in the IEEE OUI registry entry for C8:66:5D. This is the address the organization registered with the IEEE, which may differ from its current operating address.
How many MAC prefixes does Extreme Networks, Inc. own?: Extreme Networks, Inc. holds 98 OUI prefixes in the IEEE registry, of which C8:66:5D is one. A device made by Extreme Networks, Inc. could carry a MAC address from any of them.