Which company owns MAC address prefix 40:A5:EF?

MAC address prefix 40:A5:EF is registered to Shenzhen Four Seas Global Link Network Technology Co., Ltd. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 40:A5:EF has a network interface built by Shenzhen Four Seas Global Link Network Technology Co., Ltd..

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 40:A5:EF:00:00:00 that is 40:A5:EF — 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.

How many MAC prefixes does Shenzhen Four Seas Global Link Network Technology Co., Ltd. own?

Shenzhen Four Seas Global Link Network Technology Co., Ltd. holds 3 OUI prefixes in the IEEE registry, of which 40:A5:EF is one. A device made by Shenzhen Four Seas Global Link Network Technology Co., Ltd. could carry a MAC address from any of them.

Shenzhen Four Seas Global Link Network Technology Co., Ltd.

MAC address prefix 40:A5:EF is registered to Shenzhen Four Seas Global Link Network Technology Co., Ltd. in the IEEE OUI registry. Any device whose MAC address begins with 40:A5:EF has a network interface built by Shenzhen Four Seas Global Link Network Technology Co., Ltd.. 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:A5:EF:00:00:00 to 40:A5:EF:FF:FF:FF.

OUI prefix: 40:A5:EF
Hyphen form: 40-A5-EF
MAC range: 40:A5:EF:00:00:00 – 40:A5:EF:FF:FF:FF
Addresses in block: 16,777,216
Organization: Shenzhen Four Seas Global Link Network Technology Co., Ltd.
Address: Room 607-610, Block B, TAOJINDI Electronic Business Incubation Base Tenglong Road, Longhua District, Shenzhen Guangdong CN 518000
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 Shenzhen Four Seas Global Link Network Technology Co., Ltd.

Shenzhen Four Seas Global Link Network Technology Co., Ltd. holds 3 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.

2016-07-29Assigned to "Shenzhen Four Seas Global Link Network Technology Co., Ltd."
archived source →
2026-07-17Assigned to "Shenzhen Four Seas Global Link Network Technology Co., Ltd."

Nearby in the registry

The prefixes assigned immediately before and after 40:A5:EF:

FAQ

Which company owns MAC address prefix 40:A5:EF?: MAC address prefix 40:A5:EF is registered to Shenzhen Four Seas Global Link Network Technology Co., Ltd. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 40:A5:EF has a network interface built by Shenzhen Four Seas Global Link Network Technology Co., Ltd..
What is the OUI 40:A5:EF?: 40:A5:EF is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to Shenzhen Four Seas Global Link Network Technology Co., Ltd.. It covers every address from 40:A5:EF:00:00:00 to 40:A5:EF:FF:FF:FF, or 16,777,216 addresses in total. It is also written 40-A5-EF.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 40:A5:EF:00:00:00 that is 40:A5:EF — 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 Shenzhen Four Seas Global Link Network Technology Co., Ltd. located?: Shenzhen Four Seas Global Link Network Technology Co., Ltd. is listed at Room 607-610, Block B, TAOJINDI Electronic Business Incubation Base Tenglong Road, Longhua District, Shenzhen Guangdong CN 518000 in the IEEE OUI registry entry for 40:A5:EF. This is the address the organization registered with the IEEE, which may differ from its current operating address.
How many MAC prefixes does Shenzhen Four Seas Global Link Network Technology Co., Ltd. own?: Shenzhen Four Seas Global Link Network Technology Co., Ltd. holds 3 OUI prefixes in the IEEE registry, of which 40:A5:EF is one. A device made by Shenzhen Four Seas Global Link Network Technology Co., Ltd. could carry a MAC address from any of them.