joining two network ports together
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Thread: joining two network ports together

  1. #1
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    joining two network ports together

    i am not sure what you call this
    loopbacking?
    at work we have two ports side by side to plug you computer/laptop into.


    if you take one network cable and plug one end into one output and the other end into the other output this crashes the network

    is there a way to pick up where this happens or prevent the network from crashing?

    the network is dhcp
    switched
    and uses an proxy prior

    (if i have repeted this sorry)
    like life, this is a test

  2. #2
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    What kind of router / switch is this?

    I know what your talking about, as I accidentally plugged the same switch into itself by accident once which brought down all nodes on that switch. However, I cannot think of the term right now. Though loopback does sound plausible.

    Depending on the router / switch it might be able to log when this happens, if its a lower end switch, I would imagine that your somewhat out of luck as far as being to catch this electronic wise via logging.

    Next question would be, why are you having this probelm in the first place? is anyone allowed to plug / unplug cables into the router switch?
    =

  3. #3
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    this does not have to happen at the switch level (these are locked away anyhow)

    basically where the network cables come out of the wall if you unplug one
    from the wall, unplug the second cable from the back of the other computer and then plug that back in the now empty slot you get network shutdown

    do not know if it is logged as i takes ages to go around the site to find where it happens
    like life, this is a test

  4. #4
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    ahh..I c.

    That does present a bit of a problem.

    Is it the same jack / network plate all the time that someone is doing this? Or is someone doing this at random jacks?
    =

  5. #5
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    If you use Cisco switches you can use "bdpu guard" to prevent a loop from taking down a network.

  6. #6
    Disgruntled Postal Worker fourdc's Avatar
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    Another way to prevent this of course is to disconnect the premise wiring from the switch at the patch panel. This would also prevent unauthorized workstations from getting on your LAN.
    ddddc

    "Somehow saying I told you so just doesn't cover it" Will Smith in I, Robot

  7. #7
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    Quote Originally Posted by Net2Infinity
    If you use Cisco switches you can use "bdpu guard" to prevent a loop from taking down a network.
    Is there anything similiar to that for HP Procurve managed switches?
    =

  8. #8
    THE Bastard Sys***** dinowuff's Avatar
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    Don't all switches these days use spanning tree protocols?

    http://www.cisco.com/univercd/cc/td/...an2/stpapp.htm
    09:F9:11:02:9D:74:E3:5B8:41:56:C5:63:56:88:C0

  9. #9
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    That's a loopback alright. I'm sure most modern umanaged switches will detect it and I'm quite sure managed switches support STP..

    But STP might be the cause the network is "crashing". Recalculating the tree can take a long time if not configured correctly and the entire network will be down in the mean time.
    If the network is anything like I've seen, add a switch here, there.. Few months later another there.. etc.. it might need a major reconfiguration.

    Another good thing to do (and boost your security a bit) is to disable all unused ports on your switches. You can stick anything[*] in a disabled port, it won't work.
    [*] Not really anything though.. 220 volts does some fecking gawdawful things to a switch
    Last edited by SirDice; November 12th, 2007 at 07:15 PM.
    Oliver's Law:
    Experience is something you don't get until just after you need it.

  10. #10
    THE Bastard Sys***** dinowuff's Avatar
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    Quote Originally Posted by SirDice
    That's a loopback alright. I'm sure most modern umanaged switches will detect it and I'm quite sure managed switches support STP..

    But STP might be the cause the network is "crashing". Recalculating the tree can take a long time if not configured correctly and the entire network will be down in the mean time.
    If the network is anything like I've seen, add a switch here, there.. Few months later another there.. etc.. it might need a major reconfiguration.

    Another good thing to do (and boost your security a bit) is to disable all unused ports on your switches. You can stick anything[*] in a disabled port, it won't work.[*] Not really anything though.. 220 volts does some fecking gawdawful things to a switch
    True I didn't think about multiple switches, different firmware, hardware, stuff like that.

    #1 rule of thumb is the locking unused ports. Most of the higher end switches you can configure to allow "registered mac addresses" but that's a whole nother story.

    So uh Dice...

    Why do I get the feeling that you have first hand knowledge of 220 volts pulsing through a rj 45 port?
    09:F9:11:02:9D:74:E3:5B8:41:56:C5:63:56:88:C0

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