Interfaces randomly swapped?



  • After a power outage, a router froze as the power came back on.  It's not on a UPS, so I can assume the power was choppy during the first few moments.  I powered it down, then rebooted again.  It came right back up, only the LAN and WAN interfaces had been swapped.  Very odd - any theories on this?

    Running 1.2.3-RC1 built on Mon Apr 20 12:40:07 EDT 2009.  I know it's time to upgrade, but I was more concerned about getting the box back online at the moment.



  • What are the interface names? (e.g. fxp0, em1, vr2 etc)

    Its hard to image how this might have happened.

    If your interfaces are PCI devices their names will depend upon the driver that claims ownership and the order in which FreeBSD finds them as it scans the PCI device tree and that won't change UNLESS you changed the slots between the time you configured the system and the time you started it up again.

    If your interfaces are USB devices I suspect the device names could be a bit more problematic - the device names MIGHT depend a bit on what other USB devices are present and what they are doing.



  • They're both PCI cards….em0 and em1.  The MACs are very close, but I can't imagine that having anything to do with it.  One is ::::*:e0 the other ends with :ee.



  • If your bios has pnp enabled, it may have made changes similar to swapping slots without you actually doing anything. I suppose the bios could have been reset during the power outage if the motherboard battery died.


  • Rebel Alliance Developer Netgate

    This kind of swapping is due to the probe order being changed somehow. IIRC, FreeBSD always probes the same way, but this can be influenced based on BIOS settings.

    Typically it's BIOS or hardware related, but it would likely happen regardless of the OS in your case.


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