Bad crossover cable?

Discussion in 'Cisco' started by Dmitry, Nov 4, 2003.

  1. Dmitry

    Dmitry Guest

    Hi,

    I recently found an improperly wired crossover cable between two of my
    switches as shown below.
    Pin1 <---> Pin6
    Pin2 <---> Pin3

    So in essence, I have a reversed polarity between send and receive.
    TX+ <-----> RX-
    TX- <-----> RX+

    The network still functions but with interrmitent connectivity
    problems.

    Anyone know what the actual effect is of crossing pin 1 with pin 6 and
    pin 2 with pin 3 on a 100BaseT network?

    I am also wondering how it worked at all.

    Thanks in advance
    Dmitry, Nov 4, 2003
    #1
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  2. Dmitry

    D. Abaimov Guest

    Both networked devices have operational amps/comparators that only pick up
    the voltage difference between the two conductors. It's called "balanced
    signal" Therefore, it does not really matter what polarity it is. Well, this
    is in theory. In reality though, the actual transmit/receive circuitry is
    pretty complex, and in some cases it may be sensitive to noises that could
    have been filtered out if the polarity was right.
    --
    Dmitri Abaimov
    http://www.cabling-design.com
    Residential Cabling Guide and other useful online resources for premises
    wiring users and professionals
    http://www.cabling-design.com/resources/documents/residential.html
    Residential Cabling Guide 2003

    "Dmitry" <> wrote in message
    news:...
    > Hi,
    >
    > I recently found an improperly wired crossover cable between two of my
    > switches as shown below.
    > Pin1 <---> Pin6
    > Pin2 <---> Pin3
    >
    > So in essence, I have a reversed polarity between send and receive.
    > TX+ <-----> RX-
    > TX- <-----> RX+
    >
    > The network still functions but with interrmitent connectivity
    > problems.
    >
    > Anyone know what the actual effect is of crossing pin 1 with pin 6 and
    > pin 2 with pin 3 on a 100BaseT network?
    >
    > I am also wondering how it worked at all.
    >
    > Thanks in advance
    D. Abaimov, Nov 4, 2003
    #2
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