What is a MAC Address?

MAC, Media Access Control, address is a globally unique identifier assigned to network devices, and therefore it is often referred to as hardware or physical address. MAC addresses are 6-byte (48-bits) in length, and are written in MM:MM:MM:SS:SS:SS format. The first 3-bytes are the ID number of the manufacturer, which is assigned by an Internet standards body. The second 3-bytes are serial numbers assigned by the manufacturer.

MAC layer represents layer 2 of the TCP/IP (adopted from OSI Reference Model), where IP represents layer 3. MAC address can be thought of as supporting hardware implementation whereas IP address supports software implementation. MAC addresses are permanently burned into hardware by the hardware manufacturer, but IP addresses are assigned to the network devices by a network administrator. DHCP relies on MAC addresses to assign IP addresses to network devices.

How do I find the MAC address of the network device?

Operating Systems support various command-line and GUI utilities to allow users to find the MAC address of the system. On Unix variants including Solaris and Linux support "ifconfig -a", "ip link list" or "ip address show" command that displays MAC address of the network device among other useful information. Windows including NT, 2000, XP and 2003 support "ipconfig /all" command that displays MAC address. On a MacOS, one can find the MAC address by opening "System Preferences", and then selecting "Network".