Catalyst 3560 single port collision problem

Discussion in 'Cisco' started by justin_ltg, Jun 27, 2006.

  1. justin_ltg

    justin_ltg Guest

    I have a catalyst 3560 48pt switch. Upon viewing the stats, I have 1
    port that has a high number of transmit and total collisions.

    Interface Unicast Multicast Broadcast Total Collisions
    Fa0/18 114168 344740 658914 0
    Fa0/19 595186 64387 156112 0
    Fa0/20 0 0 0 0
    Fa0/21 404368 344732 658575 0
    Fa0/22 454810 344740 655596 15717
    Fa0/23 0 0 0 0

    This port is connectecd to a PC. How can I find out what is causing
    the high collision rate for this port?

    justin_ltg, Jun 27, 2006
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  2. justin_ltg

    Newbie72 Guest

    I would suspect a bad nic card or ethernet cable or port speed

    Ethereal or some other packet sniffer should tell what type of packets
    are bad....

    Check the speed and duplex settings on the switch and the pc. If they
    are mismatched correct the issue. Also try to move the patch cord from
    fa0/22 to a different port. If the problem goes away then the issue is
    in the switch. If the problem stays then it is in the cable plant or
    pc. try new patch cords or test the cable using a cable tester to make
    sure you do not have a bad cable. try replacing the nic in the pc or
    replacing the pc all together. If you still have problems then it is
    time to have the cable plant tested for NEXT and other interference.

    Newbie72, Jun 27, 2006
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  3. justin_ltg

    anybody43 Guest

    Not at all. This is a perfectly normal collision rate.
    There is not enough information here to tell if there is a missmatch
    or not.
    There is *no* problem here.

    Here is what you need to do.
    Check that you do not have duplex mismatch using

    Basically if you have a mismatch the HD end *may* record
    late collisions and the FD end may record CRC and/or Frame
    (Align) and/or Runts. If the traffic is heavy you are pretty certain
    to see these reports.

    If you don't have a mismatch then you can decide whether you
    need or want to change the ports registering collisions from
    HD to Full Duplex. The chances are that for a PC it will make
    little measurable or noticable difference.

    Collisions (or as Mr Siefert would now call them Contention Events)
    are a perfectly normal part of ethernet operation.

    Plan B.
    You will *never* be happy until the collision counters are gone.
    Convert all links to FD immediately. Then carry out the same
    checks as above to make sure that you do not have
    duplex mismatches.
    anybody43, Jun 27, 2006
  4. justin_ltg

    justin_ltg Guest

    Thanks everyone.

    I got off easy. Brand new install so last thought was the patch
    cables. But this turned out to be an easy one. Bad patch cable from
    Switch to Panel.
    justin_ltg, Jun 27, 2006
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