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What Is a MAC Address?

Tips on how to find a MAC address, Identifying Unknown Devices, DHCP and more.

When you think about networking, IP addresses are probably the first things that come to mind. But there's another type of network address called a MAC address that actually forms the foundation upon which IP address communication is built, at least where local area networks are concerned.

What Is a MAC Address?

A MAC (Media Access Control) address, sometimes referred to as a hardware address or physical address, is an ID code that's assigned to a network adapter or any device with built-in networking capability, such as a printer. While an IP address can potentially be assigned to any device, a MAC address is "burned into" a given device from the factory. A MAC address takes the form of six pairs of hexadecimal digits, usually separated by colons or dashes and will look something like this: 01:1F:33:69:BC:14. Hexadecimal digits can include only the numbers 0-9 and letters A-F.

The first three pairs of digits in the MAC address are called the OUI (Organizational Unique Identifier), which identifies the company that manufactured or sold the device. For example, a MAC address that begins with 00:1F:33 denotes a Netgear product. The last three pairs of digits are specific to the device and can be more or less considered a serial number of sorts. Together, the two parts of the MAC address form an ID that's unique to a particular device.

To understand how MAC addresses are used, first consider that when you type www.smallbusinesscomputing.com into your Web browser, it can't get there until a DNS (Domain Name Service) server looks up the corresponding IP address for the Web site allowing a connection to take place. While MAC addresses don't have any real significance on the Internet, they're used in a similar way on a LAN (local area network).

Given that IP addresses can't be permanently assigned to a device — after all, a particular address can belong to one computer today and another one tomorrow — MAC addresses allow communication between devices on a local network by making it possible to reliably distinguish one computer from another. Just as DNS matches a Web site name to an IP address on the Internet, a technology called ARP (Address Resolution Protocol) matches an IP address to the corresponding MAC address of a specific device to which that IP address is currently assigned.

Article excerpt courtesy of SmallBusinessComputing.com

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