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I have three computers all wired into my router. The box I'm posting this from is running Ubuntu 11.10, and another machine is running Xubuntu 11.10 Both connected automatically when the ethernet cable was plugged in. However, my wife's computer, running Ubuntu 10.10, cannot connect to the eth0 connection. I checked the connection's properties and the MAC address is all zeroes! How do I determine what numbers to plug into the MAC Address field?

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im not sure, but that sounds like a hardware problem. what kind of network card are we talking about? – Dominik Nov 1 '11 at 23:06
Just put any hexadecimal number (0-9, a-f). Make sure that no other computer on your LAN have the same MAC address. – Anonymous Nov 1 '11 at 23:28
Can anyone verify that the comment above by Anonymous is a valid answer? I'd like a member's second opinion before I give it a try. – Shawn Nov 1 '11 at 23:58
@Shawn S/he is a real user with close to 400 rep. FYI – djeikyb Nov 2 '11 at 2:35

2 Answers

up vote 7 down vote accepted

Try this from a terminal:

ifconfig

Your MAC address is the one after HWaddr. If it is 00:00:00:00:00:00 I think something is wrong with either the hardware or the driver.

If you somehow erased your MAC-address from the network settings you can get it back by writing this in the terminal:

  1. sudo lshw > lshw.txt

  2. write password when prompted for it

    this takes approximately 20 seconds.

  3. gedit lshw.txt

Now you are looking at a list of all your hardware. But we only want the networking specs. Do a search for "network". A couple of lines under that line, there should be a line like this: 

serial: 01:21:ee:de:01:11

Only your numbers will be different. This is the MAC-address. Copy that address, and paste it into the network settings. Then you should have restored your original MAC-address.

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will manually entering a MAC address as mentioned above get the eth0 working? – Shawn Nov 2 '11 at 0:33
The MAC address is chosen by the production company, and can not just be set to something else. (Although programs such as macchanger can trick your computer to think so). If you are able to change it, just try. Pick some random numbers: 00:11:22:33:44:55. – Elvis Stressborg Nov 2 '11 at 1:02
up vote 5 down vote

First, open 'System settings'. Then select 'Network', and then you will be able to get it by copying what is after 'Hardware address'. Hope it helped you.

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