Newbie question re back-to-back serial cables

Discussion in 'Cisco' started by familyjewelz@hairyballs.com, Oct 17, 2007.

  1. Guest

    I've just started working in my Cisco lab and I heard somewhere that
    you shouldn't disconnect back-to-back serial cables from the
    interfaces while the routers are powered on. Is there any truth to
    this?

    Thanks for any info.
     
    , Oct 17, 2007
    #1
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  2. Trendkill Guest

    On Oct 17, 1:33 pm, wrote:
    > I've just started working in my Cisco lab and I heard somewhere that
    > you shouldn't disconnect back-to-back serial cables from the
    > interfaces while the routers are powered on. Is there any truth to
    > this?
    >
    > Thanks for any info.


    Not sure what you mean by back to back serial cables, but I see no
    reason why this warning is legit, and have never encountered such a
    problem in any of my labs back in the day. Perhaps Merv or Mike has
    some additional input.
     
    Trendkill, Oct 17, 2007
    #2
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  3. With old routers you may burn the port. Also, if you plug the cable
    "on-fly", your controller may fail - cable itself defines what type of
    interface to initialize. For example, if you connect V.35 cable, the same
    controller will initialize the same port as V.35 interface, but if you plug
    RS-232 cable, the port will be RS-232 port. Also there is a difference if
    controller is initialized as DTE or DCE. And all of this is determined
    during bootup, depending on that is connected to the serial port.

    Good luck,

    Mike
    CCNP, CCDP, CCSP, Cisco Voice, MCSE W2K, MCSE+I, Security+, etc.
    CCIE R&S (in progress), CCIE Voice (in progress)
    ------
    Headset Adapters for Cisco IP Phones
    www.ciscoheadsetadapter.com
    www.headsetadapter.com



    <> wrote in message
    news:...
    > I've just started working in my Cisco lab and I heard somewhere that
    > you shouldn't disconnect back-to-back serial cables from the
    > interfaces while the routers are powered on. Is there any truth to
    > this?
    >
    > Thanks for any info.
     
    headsetadapter.com, Oct 18, 2007
    #3
  4. Scott Perry Guest

    The word "should" puts uncertianty into this. I lean more towards this
    being a relatively safe activity.

    In ten years of working with 2500 and 2600 series up to 3600 and 7200, I
    have plugged/unplugged serial interface cables while both ends were powered
    on and not burned up any equipment. I would have cared less about the 2500
    series than controllers for the 3600 and 7200. When the links are not up, a
    software shutdown/no-shutdown often clears links if problems are
    experienced. I have even witnessed a serial cable getting plugged in upside
    down which bent the plug housing, but after reverting the cable back the
    connection still worked.

    It is probably not a bad idea to keep devices off when connecting and
    disconnecting cables unless it creates unneccesary inconvenience. If you
    are wanting to connect or disconnect a serial cable and might have to wait
    until network downtime or a maintenance period, I would support just
    connecting a cable or disconnecting a cable while the device is powered on
    to get things done. It depends on how prudent and cautious you and your
    company want to be in facing the risk. In my experience, I have had no more
    trouble with connecting/disconnecting while powered on than I have with a
    PS/2 style keyboard or mouse cable on a PC.

    --

    ===========
    Scott Perry
    ===========
    Indianapolis, Indiana
    ________________________________________
    <> wrote in message
    news:...
    > I've just started working in my Cisco lab and I heard somewhere that
    > you shouldn't disconnect back-to-back serial cables from the
    > interfaces while the routers are powered on. Is there any truth to
    > this?
    >
    > Thanks for any info.
     
    Scott Perry, Oct 22, 2007
    #4
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