MAC Address Validator - Network Hardware Address Validation
MAC Address Validator
Validate and normalize MAC (Media Access Control) addresses
About MAC Addresses
A MAC (Media Access Control) address is a unique identifier assigned to network interfaces for communications on the
physical network segment. MAC addresses are used in the data link layer of the OSI model and are essential for local
network communication. They are hardcoded into network interface cards (NICs) by manufacturers, though they can be
changed through software on most modern operating systems.
MAC Address Structure
A MAC address consists of 48 bits (6 bytes) typically represented as 12 hexadecimal digits:
- First 24 bits (3 bytes): OUI (Organizationally Unique Identifier) - identifies manufacturer
- Last 24 bits (3 bytes): NIC (Network Interface Controller) specific - unique to device
MAC Address Formats
MAC addresses can be written in several standard formats:
| Format |
Example |
Common Usage |
| Colon notation |
00:1A:2B:3C:4D:5E |
Linux, Unix, most common |
| Hyphen notation |
00-1A-2B-3C-4D-5E |
Windows, Microsoft |
| Dot notation (Cisco) |
001A.2B3C.4D5E |
Cisco networking equipment |
| No separator |
001A2B3C4D5E |
Databases, programming |
MAC Address Types
MAC addresses can be classified based on their first octet (byte):
- Unicast: Least significant bit of first octet is 0 (e.g., 00:xx:xx:xx:xx:xx)
- Multicast: Least significant bit of first octet is 1 (e.g., 01:xx:xx:xx:xx:xx)
- Broadcast: All bits set to 1 (FF:FF:FF:FF:FF:FF)
OUI (Organizationally Unique Identifier)
The first three bytes of a MAC address identify the manufacturer:
| OUI |
Manufacturer |
| 00:1A:2B |
Apple Inc. |
| 00:50:56 |
VMware, Inc. |
| 00:0C:29 |
VMware, Inc. |
| 08:00:27 |
Oracle VirtualBox |
| 00:15:5D |
Microsoft Corporation |
When to Use MAC Validation
- Network Management: Validate MAC addresses in network device configurations
- Access Control: MAC-based authentication and filtering
- Asset Tracking: Inventory management using MAC addresses
- DHCP Configuration: Static IP assignment based on MAC address
- Network Monitoring: Track devices on network by MAC address
- ARP Tables: Validate entries in Address Resolution Protocol tables
MAC Address vs IP Address
| Feature |
MAC Address |
IP Address |
| OSI Layer |
Data Link Layer (Layer 2) |
Network Layer (Layer 3) |
| Scope |
Local network segment |
Global (Internet-wide) |
| Assignment |
Manufacturer assigned |
Network administrator/DHCP |
| Format |
48-bit hexadecimal |
32-bit (IPv4) or 128-bit (IPv6) |
| Changeability |
Hardware-fixed (but can be spoofed) |
Can change frequently |
Special MAC Addresses
- FF:FF:FF:FF:FF:FF: Broadcast address (all devices on local network)
- 01:00:5E:xx:xx:xx: IPv4 multicast
- 33:33:xx:xx:xx:xx: IPv6 multicast
- 01:80:C2:00:00:00: Spanning Tree Protocol
- 00:00:00:00:00:00: Invalid/null MAC address
MAC Address Randomization
Modern operating systems implement MAC address randomization for privacy:
- iOS: Uses random MAC addresses when scanning for WiFi networks
- Android: MAC randomization enabled by default on Android 10+
- Windows 10: Random hardware addresses feature available
- Purpose: Prevents tracking of devices across different networks
- Impact: Makes MAC-based access control less reliable
Test MAC Addresses
| Type |
Example |
| Standard Unicast |
00:1A:2B:3C:4D:5E |
| Multicast |
01:00:5E:00:00:01 |
| Broadcast |
FF:FF:FF:FF:FF:FF |
| Locally Administered |
02:00:00:00:00:01 |
Locally vs Globally Administered
The second-least significant bit of the first octet indicates administration type:
- Globally Administered (bit=0): Assigned by manufacturer, guaranteed unique
- Locally Administered (bit=1): Software-assigned, may not be globally unique
Example: 02:xx:xx:xx:xx:xx is locally administered, 00:xx:xx:xx:xx:xx is globally administered
Security Considerations
Security Notes:
- MAC addresses can be easily spoofed (changed in software)
- Don't rely solely on MAC filtering for security
- MAC addresses are visible to anyone on the local network
- Use MAC filtering as one layer in defense-in-depth strategy
- Combine with encryption and strong authentication
- Be aware of MAC randomization in modern devices
Best Practices
- Normalize MAC addresses to a consistent format for storage
- Use uppercase hexadecimal for consistency
- Store MAC addresses without separators in databases
- Implement format conversion for different systems (Cisco, Windows, Linux)
- Validate MAC addresses in network configuration scripts
- Consider MAC randomization when implementing access control
- Keep OUI database updated for manufacturer identification
Common Use Cases
- DHCP Reservations: Assign static IPs based on MAC address
- WiFi Access Control: Allow/deny devices by MAC address
- Wake-on-LAN: Power on computers remotely using MAC address
- Network Troubleshooting: Identify devices causing network issues
- Asset Management: Track hardware inventory by MAC address
- License Management: Tie software licenses to MAC addresses
Additional Resources