Cascading Connectivity Issues

Posted on 2012-09-13
Last Modified: 2013-01-28

We have a client that is working in a small 7-10 computer environment.  There have continuing issues of connectivity loss between network shares on the Server 2003 box as well as internet connectivity issues.  Initially I had figured it to be the switches because it would start with one computer losing network connectivity and progressively each workstation would go down a few minutes a part from each other in a cascading fashion.  Replacing the switch did not resolve the issue and I am beginning to think it may be a DNS issue, but any suggestions would be helpful.

Question by:AJ524
    LVL 24

    Expert Comment

    How is the network setup? How are devices connected to server? 1 switch? Multiple?

    Need a basic layout to start to help

    Is it just connection to the server that drops? So pc's can communicate with each other during the outage? Or does the network card drop connection, and get a new IP for example?

    Author Comment

    There are several patch panels throughout the office that have been tested and are working.  Every station is running off a single 10/100 switch that has just been replaced about 3 days ago.  

    It starts with a single station losing both internet connectivity as well as network connectivity and one by one every station begins to lose connection in a cascading fashion.  They are unable to access network drives/shares during the outage.  I unfortunately have not been present when the outage occurs to test if users can communicate to each other.  The outage only occurs for a short while until it comes back, but it happens 2-3 times per week.

    I am just curious at this point if anyone has had a similar issue or heard of network machines going down in a cascading fashion.
    LVL 24

    Expert Comment

    Right, well since the switch was replaced that takes it out of the loop...

    Loses connection to the server/internet

    How is the network configured? Router doing DHCP or server? This an SBS server by chance?
    Never experienced the 'cascading' effect you refer to, but normally my diags start with ping tests

    Eg, on a workstation run the following tests(i.e. during the outage)
    ping <server-dns-name>
    ping <server-by-ip>
    ping <router>

    What the pings will determine is where the breakdown is happening, if you can ping by IP but not DNS name then points to a DNS issue for example.
    If you can't ping even by IP then that normally means a switch issue - but since its a new switch that further points to possibly a server nic issue(or in the case of a failed ping to router a failing router/router nic)

    That's where I'd start...

    Anything in event viewer on server during the outage? Since the switch was already replaced I'd start with server, since I doubt all your workstations are having an issue all at the same time(all the same make/model machines?)

    Author Comment

    Its not an SBS server just server 2003. Its running DHCP and DNS, and when looking at the event viewer logs I noticed that there were some logs about DNS issues but nothing pressing.  The only problem with doing diags during the outage is that being an outsourced IT firm we are not in-house and cannot respond to the outage quick enough to do any diagnostics.  The last IT company improperly set up a few roles on the server and we are in the process of correcting those.

    It may be a NIC issue on the server itself, but the manner of each station going down one after the other is very strange and new to me.

    They all have different workstations running XP.
    LVL 24

    Expert Comment

    Ok, well you could try a different approach, setup a basic batch file on one of the stations desktop, during the outage get the users to double click this batch file which in turn is just running the ping tests...

    The commands I'd run are
    ping serverbydns > serverbydns.txt
    ping serverbyip > serverbyip.txt
    ping router > router.txt

    This will log the results into 3 txt files, which you can then review when you get onsite...

    Next question I'd ask is, how long the outage? 5 minutes? More/less?
    Managed switch by any chance?
    Since there's an internet outage and the server is doing DNS it more than likely still points to a server issue, or as you mention a DNS issue, the eventviewer should reveal more details I think, but the ping results will get to an answer faster

    Author Comment

    Ok I will make those batch files and disperse them to the client..

    According to them the outage usually lasts around 10-15 minutes.

    Its a cheap 24-port Netgear unmanaged switch.

    I will try what you suggested and I will post the results.  Thanks for your help!

    Accepted Solution

    This turned out to be a weird DHCP issue.  Rebuilt the DHCP server component and the problem went away.

    Author Closing Comment

    Just a weird DHCP issue.

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