Hardware addresses

Note that Residence Life also maintains some information about configuring computers, including finding hardware addresses -- their documentation is here.

What is my hardware address?

The hardware address, or MAC address, of a machine is a unique 48-bit address that is encoded directly on the ethernet interface of the computer (thus, the "hardware" address, as opposed to an IP, appletalk, DECnet, or similar address which is configured entirely in the operating system software). It serves to uniquely identify the physical network interface of the computer, regardless of the IP address it may have at the moment.

Why register it?

With the growing popularity of DHCP, a protocol which allows users to obtain IP addresses and other configuration information automatically as needed, the IP address of a particular computer may change frequently and without notice. As a result, we need some other mechanism by which we can identify a particular machine on the network. The hardware address does not change even when the IP address changes, so it makes a good "name tag."

To assist network managers in being aware of how their network is utilized, the campus DHCP server is generally configured to provide service only to client computers whose hardware address is known.

How do I find my hardware address?

It depends on what kind of computer you have. We can't account for every possible operating system here, so if you can't find the information you need, consult your computer's documentation. You may also call CCIT's Workgroup and Network Consulting at 621-ENET; they can help with many of the more common systems.

For Windows 95/98:

Go to the Start menu and select Run. When it asks you what to open, enter winipcfg. The hardware address is listed under "adapter address" in the window that comes up. Note: please make sure the correct adapter is selected! The currently selected adapter is the first item of information in the window, and in some configurations there may be more than one available - for example, ethernet, AOL, and PPP adapters. You must register the address of the ethernet adapter that is connected to the campus network.

For Windows NT:

Open a Command Prompt window and type ipconfig /all. This will then show the ip configuration of the machine including the hardware address.

For Macintosh:

It depends a bit on what version of the Mac OS you are running. On the older Macs, your TCP/IP implementation is called MacTCP (you want version 2.0.6), which is a control panel in the system folder. On newer PowerMacs, this is called Open Transport. The latest version at this time is 1.3. You will only be concerned with the TCP/IP control panel.

If you are on an older, non-PPC Mac, and you have MacTCP:

1) Open MacTCP in your Control Panels Folder (in your system folder):

2) Hold down the option key and click on the ethernet icon. The ethernet icon is the one that looks like a globe impaled on a pole with arrows goiung in both directions. When you option-click this icon, you should see a string of 12 letters or numbers appear under the icon. This is your MAC address.

If you are on a PPC-based Mac running Open Transport:

1) Open the TCP/IP control panel (Its in your control panels in the system folder):

2) When the TCP/IP config dialog box comes up, click on the "Info" button. In the "Info" dialog box, there is a listing for the hardware address:

For Mac OS X (thanks to Anthony Hess and Joel Snyder)

There are at least a couple ways to go about this.

One:

Open the System Profiler application in the Utilities folder. Under the first tab on the left, called System Profile there is something like this:

"Ethernet address" is the hardware address.

You can also get this output by going to the Apple menu and selecting "About This Mac," and then pushing the "More Info..." button. That is a short-cut to getting to the System Profiler and a little easier than going to the Utilities folder.

Two:

In the Applications:Utilities folder there are two places you could find the information. One: launch the 'Terminal' application and then type

ifconfig -a

. The output looks like this:

[hostname:~] prompt% ifconfig -a
lo0: flags=8049 mtu 16384
        inet 127.0.0.1 netmask 0xff000000
en0: flags=8863 mtu 1500
        inet 10.10.10.10 netmask 0xffffffc0 broadcast 10.10.10.255
        ether 00:30:65:64:fa:54
        media: autoselect (100baseTX ) status: active
        supported media: none autoselect 10baseT/UTP 
10baseT/UTP  100baseTX  100baseTX

The hardware address is at:

ether 00:30:65:64:fa:54