clients lose network connection at random times !!

[jheyrman]

We have a strange network problem on our LAN.

At certain times (randomly) our network clients seem to lose their network connection to a server, when this occurs they can't connect to one server but are still able to connect to other servers.
This results in many strange things and errors.

"Disk or network error" (MS-Access)
"Cannot save document you must select another file name" (MS-Word en MS-Excell)
"The file is in use by another user… " (MS-Excell)

We have the impression that the problem exists more when network traffic is low.
As a result of this we started pinging the servers every second from a client PC connected to the same switch as the servers. And we discovered that when this error occurs the server in question gives no replies on the ping command. (Sometimes for more than 15 seconds and this happens about 20 times a day)

We discovered now that when we open PcAnywhere sessions to the servers the problem disappears.
The server consoles need to be unlocked and the CPU monitor needs to be visible (to send more data over the PcAnywhere session).
When the sessions are open the servers can respond to the ping command at all times and the clients don't lose their network connections to the servers anymore. When we keep the servers very busy (CPU and LAN) then the clients also seem to keep their connections alive.

Does anyone know of this phenomena or knows a solution?


Here are some specs of the things we have.

Servers:
Poweredge 1300 WinNT 4.0 SP6a (with Intel pro 10/100 LAN card)
Poweredge 4200 WinNT 4.0 SP6a (with 3com 3c980 server LAN card)
Poweredge 2500 WinNT 4.0 SP6a (with Intel 8255xx-based 10/100 LAN card)

Network:
Cisco Ethernet switch model 3524
All servers are connected to this switch and they negotiate 100Mbit Full Duplex.

Things we already tested but didn't help:
We tested with other switches (baystack, 3com) and hubs (Intel)
We changed the cabling.
Forced the auto-negotiation to 100/full 100/half 10/full 10/half
Other network cards (in clients and servers)
Checked out the temp directories on clients (MS KB: Q150943)
We disabled all the power saving on clients (NT4 Server has no power saving)


Best regards
Johan

 

[jgercken]

Um keepalives? Try hard coding the nic speeds/duplexes. 3Com nics have a tendancy to sometimes get it wrong. ----------------------------------------
Wassabi Pop Tarts! Write Kellogs today!

 

[jheyrman]

what do you mean by
Um keepalives ???

The hard coding of the speed and duplexes we already tried.

 

[byteya]

Turn off all power management on the server. You say that it happens when not much is happening. Well, maybe the hard drives or system is going into power saving mode and then having a problem getting out of it when a request comes in over the network.

Just an idea.

Jay *J*

 

[jheyrman]

thanks indeed a cool idea, NT4 server doen't support power saving !!!!!

 

[jgercken]

Keepalive - Devices will send them to maintain the socket connections during periods on inactivity. PC Anywhere sends almost a continuous stream of packets so no keepalives are needed to maintain the connection. Perhaps your timeout values are too low. Try streaming a long file to confirm (like install a shoutcast server (MP3) or something). Check your TCP/IP registry settings. For info see

http://support.microsoft.com/search/preview.aspx?scid=kb;en-us;Q120642

for the key & value details.

Did you know that you're probably not using the onboard processor on your server & pro cards. Check the registry:
System Key: [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TcpipParameters]
Value Name: DisableTaskOffload
Data Type: REG_DWORD (DWORD Value)
Value Data: (0 = Use NIC Processor, 1 = Disable NIC Processor)

You could also try spritzing your servers with holy water. ----------------------------------------
Wassabi Pop Tarts! Write Kellogs today!

 

[keith101]

I have the same problem. Connections are lost and can not ping from a w2k workstation. I don't know why. We also use Intel pro 10/100 LAN cards on nt4. I am trying to see if its cabling problems. I have also been monitoring the following w2k performance logs: Conection Failures, Connection Active, Connections Established, Connections Reset, Segments/sec. The Active and Reset rise to high values during the course of the day while the segments/sec are high during the rise times.

Keith

 

[jheyrman]

Up

 

[NewbieGirl]

We have the same problem, it was caused by our trunking port. So we had to replace our fiber jumpers and everything worked fine. Thanks,
Danielle