Why does my office network randomly go down?

Jim Martin February 24, 2012
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I do tech work for an office. The entire network goes down frequently and the way they get it back up is by powering down the switch(s). At 1st I thought it was a switch. It was replaced, but problem still present. DHCP server is a Win 2003 server. Would static IP’s help or hurt? Any ideas?

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  1. CCIE
    February 26, 2012 at 9:01 pm

    What kind of switch is it? 

    What is in the ARP tables on the computers when it goes down?

    Can you ping between machines at all?

    Is there link on the machines and the switch?

    • Hdjimmi
      February 26, 2012 at 9:47 pm

      CCIE..

      Not sure what you mean re link on machines and the switch.

      We have 20+ clients. 2, 20 port switch's. Part of problem is I am not on sight when it goes down.

      I can have someone try and ping other computers when it goes down.

      When it does go down (24 times per week), the internet is gone and connection to the server shared folders is gone, so both internet and LAN is down. Resetting the switch(s) fixes it...DHCP is on a windows 2003 server

      They are cheap, trendnet switch's. Thinking of replacing with 1, 40 port managed switch but would like to pinpoint the issue 1st...

      Is there some way on the server I can set up to go back at the time it happened and see possible causes, such as duplicate IP's, etc??

      • Hdjimmi
        February 26, 2012 at 9:48 pm

        Soory, the net goes down 2-4 times a week, not 24....

      • CCIE
        February 28, 2012 at 12:44 pm

        Link is indicated by the LEDs on the switch and the computer where the network plugs in.

        You could look in the server's event viewer to see if there are any weird things happening, but it's not going to give you a lot of detail.

        Since everything just dies suddenly and it's not just one or two devices, it could be:

        1. The switch is faulty (Trendnet isn't the most the reliable).  Or the power supply for the switch.  You said that you replaced the switch, but did you replace the PS?

        2. There's a bridge loop (you have the switch plugged into itself, or the switches are connected together in more than one port).  This is not likely, but is a possible cause.

        3. Duplicate IP addresses.  Do you have more than one DHCP server?  What kind of router do you use?

        You might have a user take a photo of the state of the switches when it happens again.

        • Hdjimmi
          February 28, 2012 at 5:44 pm

          Oh...DUH....My Bad....Yes the link lights on the NICS and switch(s) are still active when the net goes down. I put the Trendnet in in place of another 16 port they had just to see if the problem would go away. It did not..

          Only 1 DHCP server on a 2003 SBS.

          I am going to replace the 2 16 port switch's with one 40 port....Do you have a recommendation on a good one?

          One thing I should add is they have a custom router made with an old HP desktop running Linux and Clear OS....

          Appreciate the help

          JIm

        • CCIE
          March 3, 2012 at 9:39 pm

          Any news?   Did you figure it out?

      • Rob Thomas
        February 29, 2012 at 5:15 pm

        This is where you need to use your skill as a professional and get the job done. Go buy the switch and install it. If it works, you are done. If the network continues to go down after that replace the nic on the server. If that fails have the cable tested for failures or replace the cable depending on distance between the two obviously. If you want to mess with it after that.  just add the switch back in after the new switch is installed so that you can keep it live but not make it affect any other machines on the network. 

  2. FIDELIS
    February 24, 2012 at 9:13 am

    Hello, are there any specific times when this happens?  or is it random?  How many devices are you talking about?  Besides replacing devices like switches, routers(if any), cables, etc, the only other cause could be ISP related.  Have you talked to ISP about your issue?  I know this may sound stupid but, does your server uses a static address?  If it does not, make sure it does.  Has any new device being introduced to the network recently?  Sometimes it happens that there is a scheduled task being run in the background that uses all your resources.

    • Hdjimmi
      February 25, 2012 at 2:45 pm

      It is random. There are approx 20 users. Most are desktops with several laptops also. We are using DHCP. Would putting all the desktops on Static help? I did replace 1 switch (They have 2 20 port switch's currently. Thinking about putting in 1 40 port, but I don't think replacing the one did any good. Are you saying to make sure that the server itself has a static address or the entire network. When it goes down, just about all users go down both internet and LAN. No new devises have been added. I am going to put a log sheet in the server room so I can get a better feel as to times it goes down and who was affected.

      • FIDELIS
        February 27, 2012 at 8:08 am

        Hello, I was referring to server having a static IP.  With server 2008 you can have dynamic addresses with server with less issues than server 2003.  Server 2003 already comes with a couple of tools you could use to check your server side: system monitor and performance logs and alerts.  It would be worth it for you to check if there is something there.  To access these tools you can do the following:

        -- click on Start
        -- Programs
        -- Administrative Tools
        -- Performance

        or you can type perfmon.msc in the run option.

        You can also install the Network Monitor tools if they are not installed from the installation CD:

        http://www.microsoft.com/download/en/details.aspx?id=4865

        You could use something like the software in next link to monitor your network:

        http://www.solarwinds.com/products/log-management/log-management.aspx

    • Hdjimmi
      February 25, 2012 at 2:47 pm

      PSS..Is there something I can setup to monitor in SBS that may help show me why the network goes down....

      Thanks in advance

  3. Anonymous
    February 24, 2012 at 8:50 am

     IP address conflict? Using Static IPs prevents address conflicts between devices and perhaps can help you to isolate and solve the problem. 

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