Network goes down very morning

Posted on 2009-04-21
Last Modified: 2012-05-06
We have been experiencing problems with the network three days in a row .
We are using 3com 5500 switches, Stacked 4.
What happens is the network totally freezez in the mornings .The users get a network connection but the status remains at Acquiring IP address.The switches seem to be working like normal with all the green lights blinking and all The problem lasts for about an hour or so.It happens again during the day but for a few minutes only. I have tried isolating the problem and looking for bad connections but nothing specific so far.I have tried restarting the switches .. no change.  I checked for connections that were showing AMBER lights( possible errors) and disconnecting them does not change anything... I replace all the connctions . But after an hour of fumbling the network is back working like normal. This repeats again the next moning.This morning (third day)it happened early before anyone started their pc's and lasted for a very short time.Only one user noticed it.

Th first day all connections were affected during the outage taht ,Second day only some were affected( about 8 to 10 users complained) and today it hapenned to just one user who was in before office hours and it was ok after some time. I was not even in yet

Could it be one of the switches that is faulty that is causing this. Then why does it work normally for the rest of the day. How can I find if it is a faulty device.

Question by:ssosw
    LVL 32

    Accepted Solution

    Are these stacked and configured to run as a stack?
    Or, are they daisy-chained (cascaded) with an crossover cable/port?

    Four switches in a cascade will do terrible things to your LAN, including bringing it to its functional.

    In a stack, the firmware should be updated to the same version before stacking.  The auto-upgrades may work in theory, but have never had 100% success.  The commander in the stack is supposed to push out new firmware to all members.  If you do it before assembling the stack, you don't run the risk of failed/partial upgrades, or getting a flaky switch that degrades to an expensive brick.
    LVL 14

    Assisted Solution

    You might want to consider capturing snmp data from the switches to assess whether there are any faults and test the throughput of the ports.


    Author Comment

    The switches are stackable and are configured to run as one unit.
    LVL 5

    Assisted Solution

    there are 100 things to look at, but this sounds similar to a problem i once had.  confirm no one is "ghosting" or running an image capture/deploy when the problem occurs.  i found that symantec ghost would bring our nortel switches to their knees with multicast traffic and this exact scenario would occur.  it didn't happen immediately upon a ghost session.  sometimes it would take 15 minutes for the network to become overwhelmed.  look for any product that could be using multcast traffic.

    Author Comment

    It was not the switches after all. The AD server was bad and that coupled with Internet leased line problem were to blame.

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