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Thread: MAC Addresses keep resetting after change

  1. #1
    Join Date
    Nov 2012

    Question MAC Addresses keep resetting after change

    Hi All!

    I'm on Ubuntu 12.10. I have several (12) USB to Ethernet Adapters which all show the same mac address assigned by the kernal, this is a problem since I'm using them to communicate with real switches to simulate a cisco lab w/ GNS3 and the switches think there are routing loops :O

    That aside I've tried to set the mac addresses with both macchanger and ifconfig, and they do change but for about 5 minutes then they revert back to their mac's all being the same (except for 2 of them for some reason those two #7 & 8 seem to be keeping their assigned mac.

    Now I have read that changing the macs via /etc/networking/interfaces would do the trick, but when I tried for just a single NIC my Ubuntu installation would not boot, hung and had to be repaired (remove that config) before able to boot again. I don't want this to happen, and I'm thinking perhaps the syntax was older/incorrect

    This is what I used previously:

    iface net1 inet dhcp
    hwaddress ether 01:02:03:04:05:06

    2nd issue is that I've had to add entries to /etc/udev/rules.d to make sure the usb NICs are assigned interfaces based on their port, and upon reboot they are assigned the incorrect interface unless I unplug and replug them then they are assigned correctly. I'm sure there must be a way to refresh this with a script so I do not have to unplug/replug so if someone could enlighten me I would be eternally grateful!

    If it helps here is what that config looks like:

    4 Port PCI Bottom Port 1 (from left)
    SUBSYSTEMS=="usb", ACTION=="add", KERNELS=="12-1:1.0", NAME="net1"

    #4 Port PCI Bottom Port 2 (from left)
    SUBSYSTEMS=="usb", ACTION=="add", KERNELS=="12-2:1.0", NAME="net2"

    #4 Port PCI Bottom Port 3 (from left)
    SUBSYSTEMS=="usb", ACTION=="add", KERNELS=="13-1:1.0", NAME="net3"

    #4 Port PCI Bottom Port 4 (from left)
    SUBSYSTEMS=="usb", ACTION=="add", KERNELS=="13-2:1.0", NAME="net4"

    Thanks in advance I've been working on this several days and am at my wits end!


  2. #2
    Join Date
    Oct 2010
    Ubuntu 12.04 Precise Pangolin

    Re: MAC Addresses keep resetting after change

    Edit this file:

    sudo gedit /etc/udev/rules.d/70-persistent-net.rules

    It explains it self what to chache on that.

    This definetelly work on Ubuntu Servers. I've done it several times. Give it a try !

    Then do a:

    service networking restart

  3. #3
    Join Date
    Nov 2012

    Re: MAC Addresses keep resetting after change

    I've only been successful changing the name with 70-persistent-rules, and i copied what i have in that file in the first post. Any other ideas for statically assigning mac address?


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