Which company owns MAC address prefix C4:C1:9F?

MAC address prefix C4:C1:9F is registered to National Oilwell Varco Instrumentation, Monitoring, and Optimization (NOV IMO) in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with C4:C1:9F has a network interface built by National Oilwell Varco Instrumentation, Monitoring, and Optimization (NOV IMO).

How do I find the manufacturer of a MAC address?

Take the first three octets of the address — in C4:C1:9F:00:00:00 that is C4:C1:9F — 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.

National Oilwell Varco Instrumentation, Monitoring, and Optimization (NOV IMO)

MAC address prefix C4:C1:9F is registered to National Oilwell Varco Instrumentation, Monitoring, and Optimization (NOV IMO) in the IEEE OUI registry. Any device whose MAC address begins with C4:C1:9F has a network interface built by National Oilwell Varco Instrumentation, Monitoring, and Optimization (NOV IMO). 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 C4:C1:9F:00:00:00 to C4:C1:9F:FF:FF:FF.

OUI prefix: C4:C1:9F
Hyphen form: C4-C1-9F
MAC range: C4:C1:9F:00:00:00 – C4:C1:9F:FF:FF:FF
Addresses in block: 16,777,216
Organization: National Oilwell Varco Instrumentation, Monitoring, and Optimization (NOV IMO)
Address: 1200 Cypress Creek Rd. Cedar Park TX US 78613
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 "National Oilwell Varco Instrumentation, Monitoring, and Optimization (NOV IMO)"
archived source →
2026-07-17Assigned to "National Oilwell Varco Instrumentation, Monitoring, and Optimization (NOV IMO)"

Nearby in the registry

The prefixes assigned immediately before and after C4:C1:9F:

FAQ

Which company owns MAC address prefix C4:C1:9F?: MAC address prefix C4:C1:9F is registered to National Oilwell Varco Instrumentation, Monitoring, and Optimization (NOV IMO) in the IEEE Organizationally Unique Identifier (OUI) registry. Any device whose MAC address begins with C4:C1:9F has a network interface built by National Oilwell Varco Instrumentation, Monitoring, and Optimization (NOV IMO).
What is the OUI C4:C1:9F?: C4:C1:9F is an Organizationally Unique Identifier — the first three octets (24 bits) of a MAC address, assigned by the IEEE to National Oilwell Varco Instrumentation, Monitoring, and Optimization (NOV IMO). It covers every address from C4:C1:9F:00:00:00 to C4:C1:9F:FF:FF:FF, or 16,777,216 addresses in total. It is also written C4-C1-9F.
How do I find the manufacturer of a MAC address?: Take the first three octets of the address — in C4:C1:9F:00:00:00 that is C4:C1:9F — 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 National Oilwell Varco Instrumentation, Monitoring, and Optimization (NOV IMO) located?: National Oilwell Varco Instrumentation, Monitoring, and Optimization (NOV IMO) is listed at 1200 Cypress Creek Rd. Cedar Park TX US 78613 in the IEEE OUI registry entry for C4:C1:9F. This is the address the organization registered with the IEEE, which may differ from its current operating address.