Sporadic loss of network connectivity

[kirbster73]

Hi all,

 

Looking for some pointers for the experts here.

 

Currently running 2 windows 2008r2 servers as DC, plus one other. Have approx 120 workstations almost all are windows 7, connected to a wired network.

 

At random points throughout the day, machines are losing their network connection, normally noticed by the internet dropping. When this happens I can ping various IP addresses around the network and the internet but I can't get anything to show in IE or Chrome, even local controllers like the proxy server or wireless controllers.

 

Currently we are fixing this by unplugging and repluggng the network cable from the machine and it seems to pick up all the network details again and all is fine.

 

We have a sonic wall and a censornet proxy server.

 

We're not massively technical but this problem has got us stuck. Can anyone suggest where we start looking?

Edited February 2, 2017 by kirbster73

[ZeroHour]

Do dns lookups work okay?

[HPlum78]

is this happening to all the computers on the network at the same time? or is it one or two at a time? Edited February 3, 2017 by HPlum78

[Sagima]

Does the network adapter show the name of the domain when it's not working? If it doesn't Windows' public firewall settings may be blocking communication for some reason (if you've not configured/disabled it)

[kirbster73]

Do dns lookups work okay?

Hi,

 

I've just had one user report the issue, in nslookup it came up as DNS request timed out. default Server: Unknown Address: 192.168.1.1

 

We pulled out the lead and plugged it in again and all was ok.

[kirbster73]

is this happening to all the computers on the network at the same time? or is it one or two at a time?

 

It's random users at random times from what I can tell. Never everyone!

[ZeroHour]

Hi,

 

I've just had one user report the issue, in nslookup it came up as DNS request timed out. default Server: Unknown Address: 192.168.1.1

 

We pulled out the lead and plugged it in again and all was ok.

 

What security software do you use? Does it have a firewall?

[Michael]

I'd try rebooting your switches and see if this clears the issue.

[HPlum78]

Hmmm a switch issue would be an interesting call, only affecting http traffic I am not seeing it. Firewall again if its that random and affecting more than just one workstation then again I can just not get there some kind of protection from say AV or Web filtering I could see but to be cleared after pulling the network cable is saying its a session based thing..... need more info before taking those kind of leaps.