Networking OUI MAC address network device identification network troubleshooting vendor lookup

OUI Lookup Guide: How to Identify Network Device Manufacturers by MAC Address

Published on June 3, 2026 · Niwo

What is an OUI?

OUI stands for Organizationally Unique Identifier — a 24-bit (3-byte) code assigned by the IEEE Registration Authority to manufacturers of network equipment, network interface cards, and any device that communicates over a wired or wireless network. Every compliant network device carries an OUI as the first half of its MAC address.

The IEEE first established the OUI registry in the 1980s as part of the IEEE 802 networking standards. The purpose was simple: create a global, unambiguous way to identify which company manufactured a given network interface. Today, the OUI database contains over 45,000 registered assignments spanning everything from global networking giants like Cisco and Juniper to small IoT sensor manufacturers.

An OUI is expressed as six hexadecimal characters, typically grouped in pairs:

• Colon format: 00:1A:2B (Cisco/IETF standard)
• Hyphen format: 00-1A-2B (Windows/IEEE standard)
• Concatenated: 001A2B

These three representations are equivalent. The 00:1A:2B prefix, for example, tells you immediately that the device was manufactured by Cisco Systems, Inc.

🔍 Try our OUI Lookup Tool to check any MAC address — enter the full address or just the first 6 characters and get the manufacturer in seconds.

How MAC Addresses Work

A Media Access Control (MAC) address is a 48-bit (6-byte) hardware address assigned to every network interface controller (NIC) at the factory. It operates at Layer 2 of the OSI model and is used for local network communication — switching, bridging, and address resolution (ARP).

MAC Address Structure

A MAC address is divided into two 24-bit halves:

graph LR
    subgraph MAC["MAC Address Structure"]
        direction LR
        OUI["OUI (24 bits)<br/>00:1A:2B"] --- NIC["NIC-Specific (24 bits)<br/>3C:4D:5E"]
    end
    style OUI fill:#1559ed,color:#fff
    style NIC fill:#e67e22,color:#fff

The manufacturer buys a block of 2²⁴ (16,777,216) addresses starting with their OUI. Each interface they produce gets a unique NIC-specific portion, ensuring global uniqueness without central coordination beyond the OUI assignment.

Unicast vs. Multicast MAC

The least significant bit of the first byte (bit 0) indicates the frame type:

For example, the broadcast MAC FF:FF:FF:FF:FF:FF is a multicast address where all 48 bits are 1.

Globally Unique vs. Locally Administered

The second-least significant bit of the first byte (bit 1) determines uniqueness scope:

✅ When you perform an OUI lookup on a MAC address beginning with 02, 06, 0A, or 0E, the result will show manufacturer info for the OUI, but the address is likely a locally administered override rather than the factory-assigned hardware address. Our OUI Lookup Tool handles this correctly and shows the registered vendor regardless.

EUI-48 vs. EUI-64

The standard MAC address is technically an EUI-48 (Extended Unique Identifier — 48 bits). The newer EUI-64 format (used by IPv6 stateless address autoconfiguration and FireWire) expands the address to 64 bits by inserting FF:FE in the middle of the NIC portion:

EUI-48:  00:1A:2B:3C:4D:5E
EUI-64:  00:1A:2B:FF:FE:3C:4D:5E

This allows automatic generation of IPv6 interface IDs from existing MAC addresses.

Why OUI Lookup Matters

An OUI lookup — querying a MAC address prefix against the IEEE registry — is more than a curiosity. It is a practical tool used daily by network administrators, security professionals, and IT technicians.

Network Inventory Management

Corporate networks can contain thousands of devices. An OUI lookup lets you quickly classify every discovered device by manufacturer without physical inspection:

• Switch ports feeding into a block of Cisco MACs likely connect to Cisco switches.
• WiFi clients from Apple, Samsung, and Intel can be counted per manufacturer to audit device policy compliance.
• Unidentified OUIs flag devices from unknown or unexpected vendors — a potential sign of shadow IT or unauthorized hardware.

Tools like Nmap, Advanced IP Scanner, and SNMP-based inventory systems all perform OUI lookups internally to label discovered hosts. When they show “Cisco” or “Intel” next to an IP address, that label comes from the OUI database.

Security Auditing and Rogue Device Detection

OUI lookup is a first-line defense in network security:

1. Rogue access points: An unexpected OUI from a consumer-grade manufacturer (e.g., D-Link, TP-Link) on your corporate switch port could be a rogue AP.
2. MAC spoofing detection: If a device claiming to be a Cisco switch (OUI 00:1A:2B) appears with an OUI from a different vendor, something is wrong.
3. Vendor-specific vulnerabilities: Knowing the manufacturer of every device helps you correlate with known CVEs — an Intel WiFi NIC from a specific year might be vulnerable to a known exploit.
4. BYOD enforcement: Compare the OUIs of connected devices against approved manufacturer lists. A device with an obscure OUI from an unknown vendor may violate policy.

Troubleshooting and Forensics

When diagnosing network issues, knowing the manufacturer can shortcut your troubleshooting:

• Driver mismatch: Intel NICs use different drivers than Realtek or Broadcom. An OUI lookup tells you which driver stack applies.
• Firmware bugs: Certain firmware versions from specific manufacturers have known issues (e.g., Marvell Wi-Fi chips crashing under load).
• Physical location: In large deployments, a device’s OUI combined with CDP/LLDP neighbor information helps locate the physical switch and port.
• Incident response: During a forensic investigation, MAC addresses from firewall logs can be resolved to manufacturers, aiding in device attribution and timeline reconstruction.

Vendor Tracking and Procurement

Procurement teams and network architects use OUI data to:

• Verify that shipped equipment matches purchase orders (actual vs. expected OUI).
• Track hardware vendor distribution across the organization.
• Identify sole-vendor dependencies and plan diversification.
• Validate warranty and support eligibility by manufacturer.

Practical example:
You scan a /24 subnet and discover 30 devices. Using OUI lookup:
- 12 have OUIs from Cisco → core networking
- 8 from Intel → desktop PCs
- 5 from Apple → employee MacBooks
- 3 from Samsung → mobile devices
- 2 from TP-Link → potentially unauthorized consumer APs

🔍 Use our OUI Lookup to classify devices on your network in real time — supports all MAC formats and queries the complete IEEE database.

How to Use an OUI Lookup Tool

Using an OUI lookup tool is simple. Here is exactly how it works, using the Tecniwao OUI Lookup Tool as an example.

Step 1: Obtain a MAC Address

You need a MAC address to look up. Common sources:

Step 2: Enter the MAC Address

Go to the OUI Lookup Tool and enter the MAC address. The tool accepts any format:

00:1A:2B:3C:4D:5E
00-1A-2B-3C-4D-5E
001A2B3C4D5E
001a2b3c4d5e

You can also enter just the 6-character OUI prefix:

00:1A:2B
001A2B

Step 3: Read the Results

The tool extracts the first 6 hex characters (the OUI), normalizes the format, and queries the IEEE MA-L registry. The result shows:

• Manufacturer name — the registered organization
• Address — the registered street address of the manufacturer
• OUI prefix — the matched 6-character code

💡 Pro tip: For network inventory at scale, the OUI Lookup tool integrates into your workflow. Bookmark it, or use it alongside your network scanner to rapidly identify every device on the network.

🔍 Try the OUI Lookup Tool now — paste any MAC address and identify the manufacturer instantly.

OUI Lookup Examples

Here are some of the most common OUI prefixes you will encounter when scanning networks. These belong to major networking vendors and device manufacturers:

🔍 Look up any of these OUIs — or enter your own MAC address to see which manufacturer produced it. The tool works for any prefix in the IEEE database.

Interesting OUI Facts

• Cisco holds the most OUI registrations — over 200 — reflecting decades of hardware production across dozens of product lines.
• Xerox registered some of the earliest OUIs (the company invented Ethernet at Xerox PARC in the 1970s).
• VMware virtual machines all share a handful of OUIs (00:0C:29, 00:50:56), making virtual hosts trivially identifiable.
• Locally administered MACs (bit 1 set to 1) starting with 02, 06, 0A, or 0E are commonly used by Android and iOS for privacy MAC randomization.

OUI Database and IEEE Standards

The IEEE Registration Authority manages the global OUI registry under the IEEE SA (Standards Association). Understanding the database structure helps you interpret lookup results correctly.

Types of OUI Assignments

The IEEE offers three types of identifier blocks, covering different use cases:

MA-L is what most people mean by “OUI.” It is the classic 24-bit prefix that costs a one-time fee of approximately $3,500 (as of 2026) and gives the manufacturer control over 16.7 million addresses.

MA-M and MA-S are newer, lower-cost options for smaller manufacturers and IoT device makers who don’t need millions of addresses. An MA-M assignment costs around $2,000, and MA-S around $1,000.

When you use an OUI lookup tool, most queries match against MA-L (24-bit) entries. Some advanced tools also check MA-M and MA-S.

How the IEEE Registry Works

The IEEE maintains the database at regauth.standards.ieee.org. The update cycle works as follows:

1. A manufacturer submits an application and pays the fee.
2. IEEE assigns a unique OUI from the available pool.
3. The assignment is published in the IEEE MA-L public listing (usually within 1–3 business days).
4. The manufacturer can then assign addresses from their 24-bit block to their products.

The public listing is a CSV file containing every assigned OUI with:

• Registry (MA-L, MA-M, or MA-S)
• Assignment date
• Organization name
• Street address
• OUI prefix

🔍 Our OUI Lookup Tool syncs with the IEEE database so you always query the latest assignments without downloading the full CSV.

How Many OUIs Exist?

As of mid-2026, the IEEE has assigned over 45,000 MA-L blocks, plus approximately:

• 13,000+ MA-M (medium) assignments
• 8,000+ MA-S (small) assignments

This means there are over 66,000 registered identifiers in the IEEE database. However, many older assignments are unused or belong to defunct companies — the registry is not aggressively cleaned, so some entries point to inactive organizations.

Getting Your Own OUI

If you manufacture networking hardware and need globally unique MAC addresses, here is the process:

1. Apply online at https://regauth.standards.ieee.org/
2. Choose your block type — MA-L ($3,500), MA-M ($2,000), or MA-S ($1,000)
3. Provide company information — legal name, address, contact
4. Receive your OUI — typically within 2–5 business days
5. Begin assigning — you now control 16.7M (MA-L), 1M (MA-M), or 4K (MA-S) unique addresses

Most hardware manufacturers start with an MA-S for prototyping, then upgrade to MA-L for full production.

Frequently Asked Questions

How to find MAC address vendor?

Enter the MAC address into an OUI lookup tool. The tool extracts the first 6 hexadecimal characters (the OUI) and matches them against the IEEE MA-L registry. For example, entering 00:1A:2B:3C:4D:5E returns Cisco Systems as the vendor. You can use the Tecniwao OUI Lookup for instant results — it accepts any MAC format (colons, hyphens, or no separators) and supports lowercase input.

What is OUI in MAC address?

OUI (Organizationally Unique Identifier) is the first 24 bits (3 bytes, 6 hex characters) of a MAC address. It functions as a manufacturer ID — assigned and maintained by the IEEE Registration Authority. No two manufacturers share the same OUI, which guarantees that every MAC address on earth is globally unique (in the UAA case). The remaining 24 bits are assigned by that manufacturer as a unique serial number for each interface.

What is the best OUI lookup tool?

A good OUI lookup tool should: (1) accept multiple MAC formats, (2) query the official IEEE database, (3) return results instantly, and (4) require no installation. The Tecniwao OUI Lookup meets all these criteria — paste any MAC address, and it shows the registered manufacturer name and address from the latest IEEE registry. Command-line users can also use grep on the IEEE OUI CSV file or tools like arp-scan -l which perform OUI lookups automatically.

Can a MAC address be changed?

Yes, MAC addresses can be changed through software, though the hardware (burned-in) address is permanent. Operating systems allow overriding the MAC address via device manager (Windows), ifconfig/ip (Linux), or System Preferences (macOS). This is known as MAC spoofing and is used for: (1) privacy — randomizing WiFi MAC to prevent tracking, (2) network access — replacing a registered MAC, and (3) testing — simulating different devices. When a MAC is changed via software, it becomes a Locally Administered Address (LAA) — bit 1 of the first byte is set to 1. An OUI lookup on a spoofed LAA still returns the original manufacturer corresponding to that prefix.

How many OUIs exist?

As of mid-2026, the IEEE has assigned over 45,000 MA-L (24-bit) blocks, 13,000+ MA-M (28-bit) blocks, and 8,000+ MA-S (36-bit) blocks — totaling more than 66,000 registered identifiers. However, not all are actively used. Some date back to the 1980s and belong to companies that no longer exist. The actual number of active hardware manufacturers with OUIs is estimated at 30,000–35,000. The registry grows by roughly 1,500–2,000 new assignments per year.

What is the difference between MA-L, MA-M, and MA-S?

MA-L (formerly called OUI) is a 24-bit prefix giving 16.7 million addresses — suitable for large manufacturers like Cisco or Intel. MA-M (formerly OUI-36) is a 28-bit prefix giving about 1 million addresses — designed for medium-scale IoT production. MA-S (formerly OUI-12) is a 36-bit prefix giving 4,096 addresses — for small runs and prototypes. The IEEE introduced MA-M and MA-S in the early 2010s to make IEEE registration accessible to smaller companies. When most people say “OUI,” they mean MA-L.

Conclusion

OUI lookup is one of those skills that seems trivial once you know it, but genuinely changes how you approach network inventory, security monitoring, and troubleshooting. Every device on your network carries its manufacturer identity in the first six hex digits of its MAC address — and knowing how to read that identity gives you an immediate advantage.

Whether you are:

• Building a network inventory — classify every device by vendor without touching a single cable
• Investigating a security incident — trace firewall logs to specific manufacturers
• Troubleshooting a connectivity issue — identify driver families and known firmware bugs
• Planning procurement — audit your current vendor distribution for diversification

…OUI lookup is the technique that delivers answers in seconds.

Ready to Identify Your Network Devices?

• OUI Lookup Tool — Enter any MAC address and get the manufacturer instantly. Supports all formats (00:00:00, 00-00-00, 000000) and queries the complete IEEE database.
• Advanced IP Scanner — Discover all devices on your network, then use OUI lookup to classify them.

Every MAC address tells a story. An OUI lookup tells you who wrote it.

🔍 Try the OUI Lookup Tool now — paste a MAC address and discover the manufacturer in seconds.