MAC Address
A unique hardware identifier assigned to network interface cards, used for communication on the local network segment at the data link layer.
What is a MAC Address?
A MAC (Media Access Control) address is a unique identifier assigned to a network interface controller (NIC) for communications at the data link layer (Layer 2). Also called a hardware address or physical address, it identifies devices on a local network segment.
MAC Address Format
MAC addresses are 48 bits long, typically displayed as six pairs of hexadecimal digits:
- Example: 00:1A:2B:3C:4D:5E
- OUI (first 3 bytes): Identifies the manufacturer
- NIC-specific (last 3 bytes): Unique identifier for the device
How MAC Addresses Work
When data travels on a local network, devices use MAC addresses to identify the source and destination. Switches maintain MAC address tables to forward frames only to the appropriate port, rather than flooding all ports.
MAC vs. IP Address
- MAC Address: Hardware-based, used on local networks, doesn't change
- IP Address: Software-assigned, used for routing, can change
Security Considerations
MAC addresses can be spoofed, so they shouldn't be the sole basis for security controls. MAC filtering provides only basic access control.