Network Interruptions

Posted on 2010-09-20
Last Modified: 2012-06-27
I have been having some intermittent network communication problems.  We have a SBS 2003 and about 15 client computers running XP pro SP3.  They are all connected to the same Gigabit switch, along with a neutopia router (dsl).  Exchange is running, Outlook 2003 as the email client.  A wireless access point is configured but the server provides dns and dhcp.  

We have noticed that periodically the connection to the server is lost, and then is regained by not doing much of anything.  Sometimes this only lasts for a short while.  I have noticed on two particular computers, exactly every 5 min I receive the "Network cable has been unplugged" message.  This occurs and there is no communication for literally one second, then reconnects.  I even pinged the server when the message appeared, got back hardware error.  One second later all is swell.  The two computers this is happening on have a similar NIC.  However all computers have experienced Network downtime for an extended period of time earlier this month and again days ago, which seemed to resolve itself for the time being....

I thought the error message I described was a local NIC at first, but now think it may be related to the network being unavailable for the extended period of time on those 2 occasions.  As far as what the cause may be...Im grasping at straws...the Gigabit unmanaged switch? Server? Virus?  
Question by:travilocity
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Accepted Solution

Ken Boone earned 500 total points
ID: 33721571
Well I don't ever recommend running a business's core function on an unmanaged switch as you have no visibility to what is going on inside the switch on each port.  So if you are getting  the hardware error, it is because that machine lost its connection and the nic is down.  So if this happens to all machines at one time or another it would not be a server thing but more of a network thing.  It sounds like it could be the switch problem.  I doubt its a virus, it sounds like it is more of a physical issue.  Signs point to the switch or cabling but odds are high that all of your cables are not bad and are getting banged around every 5 mins.  So it does sound like it is related to the unmanaged switch.

Expert Comment

ID: 33721983
I've seen this happen at sites that originally had CAT5 wiring, then upgraded PCs and switches to gigabit without upgrading the network cables in the walls.  The PCs are able to negotiate gigabit connections, but only just.  Every once in awhile, the link goes down and has to be renegotiated, resulting in the "Network cable has been unplugged" message appearing seemingly at random.  If it were a power or port issue with the switch, then either all PCs would lose the link at the same time or the same set of PCs would experience constant connectivity issues.  You could try temporarily disabling gigabit on a couple of PCs and see if the problem still occurs with them.  If not, then it's a fairly good indicator that the patch cords, jacks and/or in wall wiring does not support gigabit.

Author Comment

ID: 33725749
I am fairly certain this problem is not due to a gigabit/support compatibility issue because this network has had all of the same cables and switch for the last few years without a problem.  I appreciate both comments, I think I will try ruling out the switch if I can.  This morning I got called in, and was told nothing was working and nobody could get onto the server.  By the time I got here all computers could log on and access email, internet, and network resources.  However we are still experiencing many "hiccups". Disconnects and reconnects mostly noticed in Communicating with Exchange and email.  However not all computers are experiencing this...

Author Comment

ID: 33727623
We ordered a replacement switch.  I will hopefully be replacing it tomorrow afternoon/evening.  We went through the day mostly functional.  There are still communication problems for that split second every now and again, but mostly goes unnoticed, except for on the computers with the Intel NICs that the network cable unplugged error appears on.  I hope its just the switch and all will be fine when replaced.  If not I think I'm out of ideas.

Author Closing Comment

ID: 33772391
The new switch resolved the problems.

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