Which company owns MAC address prefix 00:21:53?

MAC address prefix 00:21:53 is registered to SeaMicro Inc. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 00:21:53 has a network interface built by SeaMicro Inc..

What is the OUI 00:21:53?

00:21:53 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to SeaMicro Inc.. It covers every address from 00:21:53:00:00:00 to 00:21:53:FF:FF:FF, or 16,777,216 addresses in total. It is also written 00-21-53.

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in 00:21:53:00:00:00 that is 00:21:53 — 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 SeaMicro Inc. located?

SeaMicro Inc. is listed at 3250 Jay Street Santa Clara CA US 95054 in the IEEE OUI registry entry for 00:21:53. This is the address the organization registered with the IEEE, which may differ from its current operating address.

How many MAC prefixes does SeaMicro Inc. own?

SeaMicro Inc. holds 2 OUI prefixes in the IEEE registry, of which 00:21:53 is one. A device made by SeaMicro Inc. could carry a MAC address from any of them.

SeaMicro Inc.

MAC address prefix 00:21:53 is registered to SeaMicro Inc. in the IEEE OUI registry. Any device whose MAC address begins with 00:21:53 has a network interface built by SeaMicro 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 00:21:53:00:00:00 to 00:21:53:FF:FF:FF.

OUI prefix: 00:21:53
Hyphen form: 00-21-53
MAC range: 00:21:53:00:00:00 – 00:21:53:FF:FF:FF
Addresses in block: 16,777,216
Organization: SeaMicro Inc.
Address: 3250 Jay Street Santa Clara CA US 95054
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 SeaMicro Inc.

SeaMicro Inc. holds 2 OUI prefixes in total. A device with this exact prefix could just as well carry any of these:

00:22:99

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 "SeaMicro Inc."
archived source →
2026-07-17Assigned to "SeaMicro Inc."

Nearby in the registry

The prefixes assigned immediately before and after 00:21:53:

FAQ

Which company owns MAC address prefix 00:21:53?: MAC address prefix 00:21:53 is registered to SeaMicro Inc. in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with 00:21:53 has a network interface built by SeaMicro Inc..
What is the OUI 00:21:53?: 00:21:53 is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to SeaMicro Inc.. It covers every address from 00:21:53:00:00:00 to 00:21:53:FF:FF:FF, or 16,777,216 addresses in total. It is also written 00-21-53.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in 00:21:53:00:00:00 that is 00:21:53 — 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 SeaMicro Inc. located?: SeaMicro Inc. is listed at 3250 Jay Street Santa Clara CA US 95054 in the IEEE OUI registry entry for 00:21:53. This is the address the organization registered with the IEEE, which may differ from its current operating address.
How many MAC prefixes does SeaMicro Inc. own?: SeaMicro Inc. holds 2 OUI prefixes in the IEEE registry, of which 00:21:53 is one. A device made by SeaMicro Inc. could carry a MAC address from any of them.