NIU Math Help - Mac Ethernet Address

NIU Department of Mathematical Sciences
Determining the Ethernet Address of a Macintosh

Network interfaces and software

Every computer on an Ethernet network has a unique hardware address assigned by the manufacturer of the network interface. This address is not usually needed by the user, but it is used in many cases to automatically assign a "higher level" identity (such as the Internet address) to the Mac.

The exact method of determining the hardware address depends on two variables:

is the Mac hooked up using a factory-installed Ethernet adapter or a third-party add-on?
what network software is being used: the older MacTCP, or the new Open Transport?

If the network cable goes into a jack that looks like an integral part of the computer, or into a factory-installed network card in one of the expansion slots, the Mac is using built-in Ethernet. This is the most common situation.

If a network card was purchased separately, or if an external adapter (a small box plugged into the SCSI port) is being used, the methods described below might not work and you may have to use special software provided by the adapter's manufacturer.

Now pull down the leftmost (Apple) menu and select "Control Panels". If you see an item called "MacTCP" there, the Mac is using the older Internet software. If you see "AppleTalk" and "TCP/IP" on the list, you are using Open Transport. If all three are present, you are likely to run into trouble - the two methods can conflict with each other.

MacTCP

Open the "MacTCP" control panel. You should see one or more icons representing various network hardware. Locate the one labelled "Ethernet Built-In", or - if you have a third-party adapter - one that has a name related to that adapter (e.g. "Asante MiniSCSI" or some such). Press and hold the Option key and click on that icon. If a number such as 80:A0:00:12:34:56 shows up, that's it! Jot it down, remembering that there must be six groups of one- or two-digit hexadecimal numbers (i.e. the only characters you should see in it are 0-9 and A-F).

If nothing like that shows up, try the software utility described below.

Open Transport

Open the "TCP/IP" control panel. Click on the "Info" button in the lower left. If the software is properly installed and you are using a built-in adapter, you will see the "Hardware address" listed there. Again, it's six groups of two-digit hex numbers.

Apple Lan Utility

This is one of several publicly available programs which are used to find the Ethernet address if other methods fail. You can download a copy by clicking here, or accessing Apple's software site at http://swupdates.info.apple.com/

This utility will in some cases allow you to change the address assigned by the manufacturer. Please don't do it, unless the network manager clearly told you to do so.

Configuring the connection

Chances are that the networking people asked you for the Ethernet address in order to put it in a database which will assign an Internet (IP) address to your Mac automatically when it tries to access the Internet. Ask them if they are going to add it to a "BootP server".

If the answer is "yes", you must configure the network software accordingly. In MacTCP, select the button "Server" in the "Obtain address" section. If you have Open Transport, in the TCP/IP control panel select "using BootP server" from the "Configure" pull-down menu.

You can read (much) more about MacTCP, Open Transport and Mac networking in general by clicking this link.

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