Which company owns MAC address prefix 40:A9:CF?

MAC address prefix 40:A9:CF is registered to Amazon Technologies Inc. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 40:A9:CF has a network interface built by Amazon Technologies Inc..

What is the OUI 40:A9:CF?

40:A9:CF is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Amazon Technologies Inc.. It covers every address from 40:A9:CF:00:00:00 to 40:A9:CF:FF:FF:FF, or 16,777,216 addresses in total. It is also written 40-A9-CF.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 40:A9:CF:00:00:00 that is 40:A9:CF — 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 Amazon Technologies Inc. located?

Amazon Technologies Inc. is listed at P.O Box 8102 Reno NV US 89507 in the IEEE OUI registry entry for 40:A9:CF. This is the address the organization registered with the IEEE, which may differ from its current operating address.

How many MAC prefixes does Amazon Technologies Inc. own?

Amazon Technologies Inc. holds 201 OUI prefixes in the IEEE registry, of which 40:A9:CF is one. A device made by Amazon Technologies Inc. could carry a MAC address from any of them.

Amazon Technologies Inc.

MAC address prefix 40:A9:CF is registered to Amazon Technologies Inc. in the IEEE OUI registry. Any device whose MAC address begins with 40:A9:CF has a network interface built by Amazon Technologies 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 40:A9:CF:00:00:00 to 40:A9:CF:FF:FF:FF.

OUI prefix: 40:A9:CF
Hyphen form: 40-A9-CF
MAC range: 40:A9:CF:00:00:00 – 40:A9:CF:FF:FF:FF
Addresses in block: 16,777,216
Organization: Amazon Technologies Inc.
Address: P.O Box 8102 Reno NV US 89507
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 Amazon Technologies Inc.

Amazon Technologies Inc. holds 201 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.

2020-11-28Assigned to "Amazon Technologies Inc."
archived source →
2026-07-17Assigned to "Amazon Technologies Inc."

Nearby in the registry

The prefixes assigned immediately before and after 40:A9:CF:

FAQ

Which company owns MAC address prefix 40:A9:CF?: MAC address prefix 40:A9:CF is registered to Amazon Technologies Inc. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 40:A9:CF has a network interface built by Amazon Technologies Inc..
What is the OUI 40:A9:CF?: 40:A9:CF is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Amazon Technologies Inc.. It covers every address from 40:A9:CF:00:00:00 to 40:A9:CF:FF:FF:FF, or 16,777,216 addresses in total. It is also written 40-A9-CF.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 40:A9:CF:00:00:00 that is 40:A9:CF — 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 Amazon Technologies Inc. located?: Amazon Technologies Inc. is listed at P.O Box 8102 Reno NV US 89507 in the IEEE OUI registry entry for 40:A9:CF. This is the address the organization registered with the IEEE, which may differ from its current operating address.
How many MAC prefixes does Amazon Technologies Inc. own?: Amazon Technologies Inc. holds 201 OUI prefixes in the IEEE registry, of which 40:A9:CF is one. A device made by Amazon Technologies Inc. could carry a MAC address from any of them.