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Accepted
Eric
Asked: 2010-12-18 09:16:17 +0800 CST

Someone crashed a whole network with a single switch

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This might not be a real question, my apologies, but I'm pretty sure it will make your doomsday scenario enjoyment work a little.

My company act as a contractor for a larger company. We need to plug various devices on their internal network. They have a (security) limitation that prevents us from plugging a switch or router to any ethernet jack they have available. (why does that even make sense?)

Now since we do need more than one jack, we asked them to lift that restriction for us. They told us that they did. When we arrived on site, we plugged a single switch (very basic stuff) to the jack, and then the whole world came to an end. They experienced major network failure and received logs of "duplicate ips, duplicate macs" and such and the whole plant came to a grinding halt.

Of course we are accused of being responsible for this mess. My coworkers and I totaly fail to see how this could happen. Do you have any idea of why a single switch can crash a whole network?

networking switch

4 Answers

  1. Best Answer

    I agree with a few of the answers: It could have been caused by STP. Depending on the STP configuration on your switch (if it was configured for STP) and their switches, it could have caused their switches to see your switch as the STP root bridge or as a designated bridge, disrupting the normal packet flow as implemented and designed by your client. It may very well have also introduced a switch loop in to their network. It also could have disrupted traffic, depending on which version of STP is in use, by causing an STP topology recalculation when you plugged in your switch.

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  2. Sounds like Spanning Tree perhaps - but if you literally just uplinked a switch using a single port, that isn't supposed to happen.

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  3. The only way it could be you or your co workers is:

    • your laptops have static ips
    • your accidently created a switching loop (In which case if its a large network they should have STP setup)
    • one of your machines has a DHCP server installed.

    Otherwise I cannot see how you caused an entire network to fail. If they have the security you say they do this wouldnt not have happend by plugging in a switch. I think you can sleep easily.

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  4. If the switch you plugged into the network was managed, and also happened to have same static IP address assigned to it as a backbone switch. Sounds like could have added problems mentioned already. Can you attach link of switch or model you brought in?

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