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One (or two) of the client computers lose internet, apparently randomly


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#1 bjorn.l

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Posted 17 February 2014 - 06:52 AM

Hi folks. Have had the opportunity to read and learn from this forum, but this is my first post for help.

I work three days a week as an MS-Office instructor at a course provider. There are no dedicated network admin in the company, so i have to try to solve challenges in this area as well. For the most part things are running ok.

Unntil now.

We have two separate wired lans. One for the staff and one for the students. The staff network, consisting of seven Win7 clients and a SBS 2011, runs without problems, so I dont think I will have to go in to that segment any further(?)... We also have two separate wireless lans, that also runs without any noticeable problems.

 

The student network (cable), with twenty Win7 clients and a Windows Server 2008, is where the problem occur.

The client computers runs (apparently) just fine, but out of a sudden, one (or sometimes two) of them loses connection to internet. For the most part it happens to only one computer at the time, and it varies whitch one. From the affected machine, I can ping other clients, printers, DHCP server - but i cannot ping the gateway or any external addresses.

It seems also like its more prone to happen, when all (or at least most of) the client computers are in use (it happens seldom with only a few students logged on).

 

Out of a sudden, the affected pc can suddenly connected to internet again, and the problem can affect another client after a while.
 

The lack of connection can last from minutes up to an hour. What makes the connection come back, I dont know. The problem may seem minor, but it have pretty negative impact of the affected student and the teaching situation.

 

We had two very old switches (64K) in this classrom, so I hoped the issue was related to them, and bought two new ones (GB standard). The same problem still exists though.

Have tried release/renew of ip and have tried to set static ip/dns on the affected machine, but with no affect.

 

I hope someone has an idea, or can point me in good direction. Im not an network expert (yet:)) - so have that in mind.

If more info on network/server setup/topology is required, I will provide as best as I can.

Thanks in advance.

 

 

Bjorn



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#2 d0nni

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Posted 17 February 2014 - 07:58 AM

Is it always the same machines, or would it vary from machine to machine?  just wondering could it be a cabling issue? or perhaps virus or malware causing it?  have you ran malwarebytes on the machines?  ran virus scans etc?


Edited by d0nni, 17 February 2014 - 07:59 AM.


#3 bjorn.l

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Posted 17 February 2014 - 08:31 AM

Hi, and thanks for the reply. No its not always the same machine. It varies from machine to machine.

As we speak, there is two affected machines. Earlier today, it was first one, then two completely others that got affected. When its at its worst, it seams like the problem moves from one to another.

 

We have Symantec Endpoint on the server, but the weekly scans does not come up with any issues. I will try mbam locally on the clients though, just so it has been tried.

 

The cabling issue is maybe something to digg into. Where would you start from? The firewall (Sonicwall) and work my way towards the machines - or the opposite way?



#4 dls62

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Posted 17 February 2014 - 08:40 AM

You might want to check the firewall settings to see if there is a limit on the number of nodes that can be active at any one time.



#5 d0nni

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Posted 17 February 2014 - 08:43 AM

Either or,  there are good we cabling devices you can get to check the cable for errors.  The firewall settings would also be a good shout from dls62.  run malwarebytes on the machines also,  never know.  hard to give a definitive answer for something like this as it can be one of many issues lol.  the joys of troubleshooting.



#6 bjorn.l

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Posted 17 February 2014 - 09:25 AM

Limitations on the firewall sounds (to me) as something that can have very relewans. I will check that out. Thanks for the tip, dsl62

I have come across some cat cables at the patch panel, that maybe has a bit too much curl and twist. These I will possibly try to replace. Thanks d0nni.

I also have a cable tester somewhere. It is not an expensive one, but maybe it can provide some answers too.

 

If the limitation on the firewall is not the issue, I understand that this will be a joy :)

 

 

I will start off with your suggestions, and come back with my results. Thanks guys for pointing me in a diection.

 

All the best.



#7 bjorn.l

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Posted 18 February 2014 - 03:05 PM

Problem is solved. It was actually the firewall. The log showed that addresses had been blocked due to limitations to nodes.
Restarted the box, and the log was cleared. Thus, we could start with a clean slate again. How long this will last, we have to see. With nearly everyone carrying smartphones and pads, the need for addresses have risen quite a bit in recent years, so we maybe have to upgrade to a FW with more licenses.

Thanks to d0nni - and kudos to dsl62 pointing me completely in the right direction :thumbup2:

 

 

 

Bjorn



#8 dls62

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Posted 18 February 2014 - 03:19 PM

Hi Bjorn,

I'm glad to hear that you solved the problem.

Happy networking!




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