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    Question dual boot = dual MAC address?!


    I gave my network administator the MAC address reported under Linux for my network card. He assigned a static IP and everything is great. However, when I rebooted in Win98 and tried to configure the network there, it reports a different MAC address for the same card and, obviously, won't connect to that IP. I tried spoofing the MAC address through the card properties dialog, and now winipcfg shows the address I entered, i.e., the same address that Linux reports, but the card is still not recognized. What could be going on here?

    John
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    while in windows do a nbtstat -A youripaddress and write down the mac address. How does this compare to the Linux boot?

    I would suspect the Linux driver is virualizing the mac address.

    You can do the same if the nic driver supports it under 98. If you go to the nic properties and look for advanced properties and the network address. You can manually put in a mac address.

    So your options would be to change the linux boot to match the mac address in 98 or visa versa.
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    Thanks for the reply.

    nbtstat won't work because Windows deactivates the card when it fails to connect it with the configured IP address on startup. I've already tried changing the MAC address manually, such that winipcfg now tells ME that the card has the address I set (i.e., the one that is reported under Linux), but the DHCP server is obviously still reading the hard-wired MAC address.

    Also, I can't imagine why Linux would be virtualizing the MAC address, since I never configured it to do so. Since spoofing it has no effect under Windows, I'm not sure that it would work under Linux either. Also, it would involve more experimentation and changes to the DHCP database than the adminstrator will probably have patience for or interest in.
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    I have no idea why Linux would have a different mac address then the default as found in Windows.

    I am just saying that that I would believe the mac address as found in windows.

    Spoofing, to my knowledge, is done with ip not mac. You are not "spoofing" a mac address but assigning a mac address to override the hardware default.

    DHCP would just see this as another node request [if different mac address then before] and would go ahead and assign another ip address. This "deactivation' indicated to me you are not reaching the dhcp server.

    Simple test - get a ip address in your subnet range you can manually assign in Windows.
    Do not use the manual entered mac address.
    Get up and running and then do the nbtstat to get the cards default mac address.

    Unless what you mean by hardwired dhcp is that your admin has setup RESERVED ip addresses in dhcp. This means the first registered mac address is now reserved to that ip address. This is not a default of dhcp but must be manually configured. If this is the case set the Windows card back from the manual assigned address and you're now up and working.

    But this would mean that dhcp has NO unreserved ip addresses if with a different mac address you don't get an assignment. That would be foolishness on your network admins part [but I have seen these security zealots go haywire in their quest for security]

    If you can get Windows working with dhcp then use that mac address in Linux.

    Or come up with an explaination why you think Linux has a different mac address then windows. If windows connects or had connected then that mac address must be right.
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    Sorry, I don't mean DHCP. I've been assigned a static IP. Whatever authenticates that is not authenticating it. The exact Windows warning reads "The system has detected a conflict for IP address xxx.xxx.xxx.xxx with the system having hardware address XX:XX:XX:XX:XX:XX. The interface has been disabled.." I do know that folks who use DHCP rather than a static IP on this network must register their cards' MAC addresses else they don't get configured with an IP.
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    It is true that when a user gets a dhcp address the mac address is associated with that ip address.

    But what you describe is not an assigned static ip address but a reserved ip address in dhcp.

    The difference here is a static ip address DOES NOT REQUIRE A MAC ADDRESS.

    But a RESERVED dhcp address DOES REQUIRE A MAC ADDRESS. That's how dhcp knows to assign that ip address to that mac address.

    You need to give your administrator your windows mac address. Easy solution to this issue would be to get TWO reserved ip addresses. One for you linux and one for your windows boot.

    Still doesn't answer the question of two mac addresses depending on OS boot. You should be able to download a nic utility for the manufacturers web site that can properly id, without the OS, the true mac address. Worse case pull the card. The mac address should be printed on the card. Than you can work on figuring out which OS is reporting the mac address correctly and work on figuring out why the other isn't.

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