This document describes how to determine your device's Ethernet or Wireless hardware address(es). You need to know your hardware address(es) in order to register your device in the Princeton University Host Database.
If you need assistance following these instructions, or need assistance determining the Ethernet or Wireless hardware address of a platform not covered by this document, please contact the OIT Support and Operations Center (phone 609-258-HELP, firstname.lastname@example.org).
If your computer has both an Ethernet interface and a Wireless interface, each will have its own unique hardware address.
An Ethernet or Wireless hardware address is a 6-byte hexadecimal number; for example: 080007A9B2FC. Each byte is written as two hexadecimal digits, so there are twelve hexadecimal digits; each hex digit is a number from 0-9 or a letter from A-F. The letters A-F may be uppercase or lowercase.
Sometimes an '0x' is written before the value to make explicit that the following value should interpreted as hexadecimal. This '0x' is not part of the value.
Ethernet and Wireless hardware addresses are often written in other forms, to make them easier to understand. It is common separate the six pairs of hexadecimal digits (the A-F are considered hexadecimal digits, rather than letters) with colons or dashes, like: 08:00:07:A9:B2:FC or 00-00-94-ba-0e-cc. When using colons or dashes to separate the address into six pairs, sometimes any leading zero in each pair of digits is dropped; e.g. 8:0:7:A9:B2:FC or 0:0:94:ba:e:cc. (When dropping leadings zeroes in a hardware address, '00' becomes '0' -- you never completely eliminate any of the six pairs of digits.)
Do not confuse an Ethernet or Wireless hardware address with an Internet Protocol v4 ("IPv4") address; that's a number assigned to some computers and printers by the Princeton University, and looks something like: 220.127.116.11 or 18.104.22.168. Your Ethernet or Wireless hardware address is also not your email address, which typically looks something like email@example.com.
If your computer or printer has a built-in Ethernet or Wireless interface, you may find a label attached to the back or bottom of the computer displaying the hardware address.
If you find a label, make sure it really is a hardware address; the section above describes what an Ethernet or Wireless hardware address looks like. For example, if you see letters of the alphabet other than A-F, you can be sure you're not looking at an Ethernet or Wireless hardware address; perhaps it is a model number or serial number for your computer.
In some cases, you will not find a hardware address displayed on the box, the Ethernet or Wireless interface, or the computer or printer. (Or you may have discarded the box, and opening the computer or printer to examine the interface card inside may not be a good choice.) In these cases, there is usually software you can run on the computer or printer that will display the Ethernet or Wireless hardware address. Instructions for some popular configurations appear below.
Many devices can be reconfigured so that instead of using the hardware address assigned by the manufacturer, they instead forge another hardware address of your own choosing. This is sometimes called "spoofing" or "cloning" a hardware address, particularly when the forged hardware address is one that belongs to another device.
Because a device's hardware address is one of the most important ways the device is identified on the campus network, forging a hardware address is not acceptable on the campus network. No device attached to the campus network should be configured to forge its hardware address; instead, every device attached to the campus network should use the unique hardware address assigned to it by the manufacturer.
Some devices automatically change their network interface's hardware address from time to time, for example, by generating a new random (or pseudo-random) hardware address. Some do so periodically. Some do so each time the network interface attaches to a different network.
Such devices do so in the belief that it promotes privacy. More often than not, such devices limit this feature to Wireless network interfaces.
For some devices, this is a behavior which can be user-configured; for other devices, it is not user-configurable.
For the most part, we do not support use of such devices on the University's networks. Each device attached via an Ethernet or Wireless network interface at the University is expected to use the unique hardware address assigned by the manufacturer to that network interface, not to generate random values or to change the value periodically or each time it connects to a different network.
If your device allows you to configure it to generate random hardware addresses or to use its real hardware address, you should configure it to use its real hardware address. If your device generates random hardware addresses and offers no way to disable this behavior, the device is not appropriate for use on the University network.
There is a specific exception where such behavior is acceptable on the University network. When a Wireless interface is probing (scanning) to locate available wireless networks, it may choose to use a random hardware address for the wireless frames it transmits to perform those probes. The remainder of the Wireless frames the device transmits (for example, once it decides it wishes to connect to a particular wireless network) use the unique hardware address assigned by the manufacturer to that device's Wireless network interface. This behavior is acceptable.
The process of obtaining your ethernet address is fairly simple in Windows 95, Windows 98, and Windows ME. You need to have, at least, installed the Microsoft TCPIP protocol to use this method. If you have installed the MS TCPIP protocol do the following:
If you are unable to see your Ethernet interface in the window displayed by the winipcfg command, refer to the OIT KnowledgeBase solution: http://helpdesk.princeton.edu/kb/display.plx?ID=5094.
You can find your ethernet address using Microsoft's ipconfig utility:
You can find your machine's Ethernet or Wireless hardware addresses using Microsoft's ipconfig utility:
You can find your machine's Ethernet or Wireless hardware addresses using Microsoft's getmac utility:
You can find your machine's Ethernet or Wireless hardware address using Microsoft's getmac utility.
To display your Apple OS X device's Ethernet or Wireless hardware addresses:
The System Preferences application is also sometimes available in the Dock. It's also available in the Applications folder (in OS X 10.6 - 10.11, macOS 10.12) or the Utilities folder (in OS X 10.4 - 10.5).
In this Location pop-up menu, select a location that includes the network interface of interest.
For OS X 10.5 - 10.11, macOS 10.12: You can verify that a network interface (port) is a member of a location by selecting that location, then verifying that the network interface of interest appears in the network ports list on the left side of the window. Verify that the interface's status (which appears in grey just below the name of the interface) is anything other than "Inactive."
For OS X 10.4: You can verify that a network interface (port) is a member of a location by selecting that location, then in the Show pop-up menu, selecting Network Port Configurations. Verify that network interface of interest appears in the port list, and is turned "on" (its checkbox is checked).
This program is normally located in the Utilities folder, which in turn is located in the Applications folder.
In this upper-right pane, select the item for the Ethernet or AirPort (a.k.a. "Wireless") interface in which you are interested.
Each interface's hardware address is the value labelled Ethernet address, MAC address, or Hardware (MAC) address This is true even if the device is actually a wireless interface. (It is not the item labelled RouterHardwareAddress or the item labelled ARPResolvedHardwareAddress. Make a note of the value; this is the information you were seeking.
To display your Apple iOS (or iPhone OS) device's Wireless hardware address:
To display your Android device's Wireless hardware address:
Some vendors locate this category underneath some other category; this can vary from device to device.
This item also might be named something else, for example, About tablet.
When executed as root, the following command will show the hardware address for each Ethernet interface that is plumbed on the system:
# /usr/sbin/ifconfig -a lo0: flags=1000849
mtu 8232 index 1 inet 127.0.0.1 netmask ff000000 hme0: flags=1000843 mtu 1500 index 2 inet 192.168.1.2 netmask fffffc00 broadcast 192.168.1.0 ether 8:0:20:4:5:6