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What Is MAC Address Lookup
A MAC (Media Access Control) address lookup identifies the manufacturer of a network device by examining the first three octets (24 bits) of its 48-bit hardware address. Every network interface card (NIC)—whether in a laptop, smartphone, router, IoT device, or server—is assigned a globally unique MAC address at manufacture. The first half of this address is the Organizationally Unique Identifier (OUI), which maps to the device manufacturer.
MAC address lookup is a fundamental tool for network administration, security operations, and device inventory management. When you see an unknown device on your network, the OUI lookup tells you whether it is an Apple iPhone, a Dell server, a Raspberry Pi, or a Hikvision camera—providing immediate context for security decisions and troubleshooting.
How MAC Addresses Work
A MAC address is a 48-bit identifier written as six pairs of hexadecimal digits: AA:BB:CC:DD:EE:FF. The IEEE (Institute of Electrical and Electronics Engineers) manages MAC address allocation:
| Portion | Bits | Name | Purpose |
|---|---|---|---|
| First 3 octets | 24 | OUI (Organizationally Unique Identifier) | Identifies the manufacturer |
| Last 3 octets | 24 | NIC-specific | Unique within the manufacturer |
Special MAC address types:
- Unicast: Identifies a single device (least significant bit of first octet is 0)
- Multicast: Addresses a group of devices (LSB of first octet is 1)
- Broadcast: FF:FF:FF:FF:FF:FF — reaches all devices on the local network
- Locally administered: Second least significant bit of first octet is 1; assigned by software, not by IEEE
MAC randomization: Modern operating systems (iOS 14+, Android 10+, Windows 10/11) randomize MAC addresses when scanning for Wi-Fi networks and may use random addresses per network. This privacy feature means OUI lookups may return "Private" or "Locally Administered" for mobile devices.
Common Use Cases
- Network inventory: Identify the manufacturer of every device connected to your network
- Security monitoring: Detect unauthorized or unexpected device types (e.g., a Raspberry Pi on a corporate network)
- Troubleshooting: Determine device type when DHCP hostnames are missing or unhelpful
- IoT security: Identify IoT device manufacturers to assess firmware update status and known vulnerabilities
- Forensic investigation: Trace network activity to specific hardware manufacturers as part of incident response
Best Practices
- Cross-reference OUI with DHCP and DNS data — MAC address alone identifies the manufacturer; combine with hostname and IP for full device identification
- Account for MAC randomization — Mobile devices increasingly use random MACs; check the locally administered bit before trusting OUI results
- Maintain an internal MAC inventory — Track known device MACs alongside asset tags for rapid identification during security incidents
- Update OUI databases regularly — The IEEE assigns new OUIs weekly; use current databases for accurate lookups
- Use MAC filtering cautiously — MAC addresses can be spoofed; MAC filtering is a minor deterrent, not a security control
References & Citations
- IEEE Registration Authority. (2024). IEEE OUI Public Listing. Retrieved from https://standards.ieee.org/products-programs/regauth/ (accessed January 2025)
- IEEE Computer Society. (2016). IEEE 802 LAN/MAN Standards. Retrieved from https://ieeexplore.ieee.org/document/7428776 (accessed January 2025)
Note: These citations are provided for informational and educational purposes. Always verify information with the original sources and consult with qualified professionals for specific advice related to your situation.
Key Security Terms
Understand the essential concepts behind this tool
Frequently Asked Questions
Common questions about the MAC Address Lookup
A MAC (Media Access Control) address is a unique 48-bit identifier assigned to network interfaces by manufacturers. Written as six pairs of hexadecimal digits (e.g., 00:1A:2B:3C:4D:5E), the first three octets identify the manufacturer (OUI), while the last three are device-specific. MAC addresses operate at Layer 2 of the OSI model for local network communication.