Find a MAC Address in Windows
Use the ipconfig utility (with the /all option) to display the computer’s MAC address in modern versions of Windows. Older versions of Windows (Windows 95 and Windows 98) used the winipcfg utility. Both winipcfg and ipconfig may display multiple MAC addresses for one computer. One MAC address exists for each installed network card. Additionally, Windows maintains one or more MAC addresses that are not associated with hardware cards. For example, Windows dial-up networking uses virtual MAC addresses to manage the phone connection as if it were a network card. Some Windows VPN clients have their own MAC addresses. The MAC addresses of these virtual network adapters are the same length and format as true hardware addresses.
Find a MAC Address in Unix or Linux
The specific command used in Unix to find a MAC address varies depending on the version of the operating system. In Linux and in some forms of Unix, the command ifconfig -a returns MAC addresses. MAC addresses in Unix and Linux are also found in the boot message sequence. These operating systems display the computer’s MAC address onscreen as the system reboots. Additionally, boot-up messages are retained in a log file (usually var/log/messages or /var/adm/messages).
Find a MAC Address on a Mac
To find MAC addresses on Apple Mac computers, click System Preferences > Network > Advanced > Hardware.
Summary: How to Find a MAC Address
In summary, here’s how to find a computer’s MAC address:
Windows: ipconfig/all, or winipcfgLinux and some Unix: ifconfig -a (note the first “f” in ifconfig; this is easy to confuse with Windows’ ipconfig)Macintosh: Settings > Network > Advanced > Hardware
MAC addresses are fixed numbers that cannot be changed. However, there are several valid reasons to change a MAC address.
Change a MAC Address to Work With Your ISP
Most internet subscriptions provide the customer with a single IP address. The internet service provider (ISP) may assign one static (fixed) IP address to each customer. This approach, however, is an inefficient use of IP addresses. The ISP more commonly issues each customer a dynamic IP address that changes each time the customer connects to the internet. ISPs ensure each customer receives only one dynamic address using several methods. Dial-up and many DSL services typically require the customer to log in with a username and password. Cable modem services, on the other hand, do this by registering and tracking the MAC address of the device that connects to the ISP. The device with the MAC address that is monitored by an ISP can be the cable modem, a broadband router, or the PC that hosts the internet connection. The customer is free to build a network behind this equipment, but the ISP expects the MAC address to match the registered value at all times. When a customer replaces that device, however, or changes the network adapter inside it, the MAC address of the new equipment will no longer match the one registered at the ISP. In this case, the ISP typically disables the customer’s internet connection for security (and billing) reasons.
Change a MAC Address Through Cloning
Some people contact their ISPs to request they update the MAC addresses associated with their subscriptions. This process works but takes time, and internet service is unavailable until the provider takes action. To quickly work around this problem, change the MAC address on the new device so that it matches the address of the original device. Although you cannot change a physical MAC address in hardware, you can emulate it in software. This process is called cloning. Many broadband routers support MAC address cloning as an advanced configuration option. The emulated MAC address appears to the service provider as identical to the original hardware address. The specific procedure of cloning varies depending on the type of router; consult the product documentation for details.
MAC Addresses and Cable Modems
In addition to MAC addresses tracked by ISPs, some broadband modems also track the MAC address of the host computer’s network adapter within the home network. If you swap the computer connected to the broadband modem or change its network adapter, your internet connection might not function afterward. In this case, MAC address cloning is not required. Resetting (including recycling power) on both the cable modem and the host computer will change the MAC address stored inside the modem automatically.
Change MAC Addresses Through the Operating System
Windows offers an easy way to change MAC addresses.
In Linux and Unix
In Linux and some versions of Unix, ifconfig supports changing MAC addresses if the necessary network card and driver support exist.
