Nightmare - Multiple MBA on Network - Duplicate MAC addresses

Discussion in 'MacBook Air' started by lelandv, Mar 3, 2013.

  1. macrumors newbie

    Mar 3, 2013
    Could someone enlighten me as to which complete idiot at Apple decided that it would be a good idea to use the same MAC address for multiple MBAs ??

    We have three users with MBAs (each purchased separately and not as a bundle). All three of them have the same MAC address for the airport/wifi interface, and for the wired Gig-E adapter, likewise, they all have the same MAC address.

    The practical upshot of which is that when two or more users are connected on the same LAN, all hell breaks loose.

    Can someone please shoot the imbecile at Apple who came up with that hair-brained idea? and on a more practical matter, what would be the best way to persistently assign a unique MAC to these interfaces on the MBAs?

    I know that you can "spoof" or change the mac address using ifconfig, but is there a way on these things to keep it persistent, or at least automatic when the interface is brought up ?


  2. macrumors member

    Dec 19, 2006

    Are you positive? Check in the System Preferences->Network->Wi-Fi->Advanced tab, at the bottom of the screen that pops up, and then in System Information->Network->Wi-Fi.

    The odds of two MBA's manufactured having an identical WLAN MAC address is slim enough, but three? And three Ethernet adaptors? And then all being sold to the same person?? I just can't see it.
  3. thread starter macrumors newbie

    Mar 3, 2013

    Even between the MBAs tested, one was purchased in the US, the other in Germany. The users are trying to use them on the same LAN, and it's having some rather "CURIOUS" effects as I'm sure you can imagine.
    We use static DHCP assignments for that end network as well, which doesn't help matters.

    Essentially, MBA #1 and MBA #2, for example, both have b8:8d:12:53:26:14 for the gig-E adapter, and both have 60:c5:47:05:d0:1e for the airport/wifi.

    This smells a lot like clone-production rather than carefully planned manufacturing.

  4. macrumors 604


    Aug 10, 2010
    Poole, England
    What you have described is *impossible*. In theory.

    I am having a hard time believing that you have 3 MBAs that have the same MAC addresses. A MAC address is, by it's nature, a unique identifier. You have more of a chance of winning the lottery than finding 3 MBAs with the same MAC addresses. That makes me think that there is something else wrong with your network setup.

    I would suggest to go into network preferences and removing your LAN/TB adaptor and then adding it again as a first step.
  5. macrumors 6502a

    Oct 19, 2007
    Exactly. I also thought they are unique? Maybe you are using a software which is setting up a MAC address for the use in network. And maybe the default in that software is the same MAC address which is causing the problem...
  6. macrumors 604


    Aug 10, 2010
    Poole, England

  7. macrumors 601

    Aug 27, 2012
    If u were in front of me, I'd put down a thousand$ buxs right now, on the table, that you don't have 3 (THREE) same MAC.

    Most likely your switch is bad or needs a hard reset.
  8. macrumors newbie

    Dec 26, 2007
    You might lose! There were separate reports of identical MAC addresses in consumer routers a few years ago.
  9. thread starter macrumors newbie

    Mar 3, 2013
    @theSeb : While under normal circumstances I would agree with you that it would be next to impossible to have the same MAC address on multiple machines, what we are seeing is indeed just that.

    What is even more disconcerting is that the three MBA were purchased individually in different geographic locations, the most extreme being one in the US and one in Germany.

    Nevertheless, System Preferences->Network and simply "ifconfig" show the MAC addresses as follows:

    60:c5:47:05:0:1e for all three MBAs

    Gig-E adapter:
    b8:8d:12:53:26:14 for all three MBAs.

    Indeed when doing "sh mac addr dyna addr xx:xx:xx:xx:xx:xx" on the cisco switch that they're connected to (in the wired scenario), three different ports are shown for the same MAC address, corresponding to the three ports that they are actually physically connected to...

    This smells to me like someone simply trying to cut costs by CLONING on the production line...

  10. macrumors regular

    Jun 18, 2011
    Check the boxes and see if they are the same.
  11. edjs, Mar 3, 2013
    Last edited: Mar 3, 2013

    macrumors newbie

    Jun 15, 2012
    It beggars belief that three MBAs from different sources have the same MACs, without the issue coming up before now.

    I'd be inclined to check that there are no startup items that might be setting the MAC address at boot.

    If you look at About this Mac -> More Info -> System Report -> Network, it should show the burned-in MAC addresses. If they are the same there, you'll need to either set the MBAs to change the MAC at startup to something unique, or bring it up with Apple.

    Hmm. Took another look and I see that System Preferences->Network also shows the burned-in MAC, even if I change the MAC with ifconfig. <shrug>

    Makes no sense to me.
  12. macrumors newbie

    Jun 15, 2012
  13. macrumors 601

    Aug 27, 2012
    If this is not widespread (google) then the problem is local.
  14. thread starter macrumors newbie

    Mar 3, 2013
    To be perfectly fair, I did google the problem, and the only things that I found that were somewhat related where situations where a site has thousands of MBAs to administer centrally, with hundreds of the gig-E adapters. The site using Casper, and omitting to flag the dongles as removable mac addresses, thus generating duplicates in the database....

    We're mostly a Linux shop here, but we do have a few mac users... though have only ever encountered this issue with MBAs -- MBPs no problem.

    Awaiting the more detailed information from the people concerned to check the BIAs via the "About this Mac" menus, and further diagnosis...

  15. macrumors member

    Aug 28, 2008
    It's easy enough to spoof the mac address. You could script it and have it run at startup/login, or triggered by an event. I basically do this when I want to physically connect to my work network.
  16. macrumors 68000


    Jun 29, 2007

    you say you are using ethernet on MBA's. Does each computer have its own thunderbolt->ethernet adapter? Are you using USB ethernet adapters?

    Whatever type of adapter you are using is actually where the ethernet mac address is coming from, not the MBA itself.

    have you tried connecting the computers to the same wifi network? Or did you just notice that they all show the same MAC address for wifi as well?
  17. thread starter macrumors newbie

    Mar 3, 2013
    Well.. finally the mystery is solved...

    After further investigation, it turns out that the people reporting the problem were sharing the same adapters, which they failed to tell us here in Paris :mad:, hence the duplicate macs... :eek:

    We now return you to your regularly scheduled programming...

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