Unsolvable network problems

[johanneke69]

We have a strange network problem on our LAN.

At certain random times 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 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, Cisco) and hubs (Intel,3Com)
We changed the cabling.
Forced the auto-negotiation to 100/full 100/half 10/full 10/half
Other network cards (in clients and servers)
Other network card Drivers (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

 

[bcastner]

http://support.microsoft.com/default.aspx?scid=kb;en-us;Q138365

On the server
HKLM\System\CCS\Services\LanManServer\Parameters\Autodisconnect=0x0000FFFF

Note: The preceding entry must be located on the computer that offers the share or shares.
The valid value range if you edit the LAN Autodisconnect parameter in the registry is 0 to 4294967295
(0xffffffff).

- For a Windows 2000 Server in a Domain, running either as a domain controller or as a server, the maximum value is 65,535 (0xffff). Values set above this will be returned to 0xffff after policy refresh. Windows 2000 Servers in a
workgroup may be set to any value as indicated.

On the client

HKLM\System\CCS\Services\LanManWorkstation\Parameters\KeepConn=65535

Value : KeepConn REG_DWORD 1 to 65535 seconds
Default: 600 (10 minutes)
The value of KeepConn specifies the maximum amount of time that a connection can be left dormant.

Note:
Windows 2000 processes the KEEPCONN registry key differently than Microsoft Windows NT 4.0, and permits the connection to the target server to time out.

 

[johanneke69]

We tested this but it didn't work.
This is also no sulution for the windows 98/95 clients.

Best regards
Johan

 

[mojo31]

Does the machine completely lose network connection? Check pagefile size and location(preferably not on the system partition)
I had a similar problem with a w2k member server a while back where it seems that as soon as there were a number of users banging away on it, it just froze up and didnt allow any more users into files/apps on the server.
Make sure you have your network file and print settings set for to Maximize throughput for
network applications or file sharing(whichever is appropriate.
I then added the Reg keys:HKEY/LOCALMACHINE/SYSTEM/CurentControlSet/Services/lanmanserver DWORD_REG keys MaxWorkItems val=65535,
MaxRawWorkItems val=512, MaxFreeConnections val=100, MinFreeConnections
val=32.

seemed to sort it

 

[routerman]

Can you check the amount of broadcast traffic, its possible that may causing NIC problems. This would give you all sorts of apparently random problems.

The switch stats should help here.

 

[bjzielinski]

I'd start by making sure the machine does not have any viruses and has the latest patches. We had the Nachi/Welchia virus hit our networks hard last month; a building with hubs was completely out of service, other buildings with switches crawled but were operational. I easily tracked the culprit computers by listening to ARP traffic, which the infected computer generated TONS of.

Bill Zielinski
bzielinski@co.midland.mi.us
County of Midland, Michigan

 

[johanneke69]

still no solutions ?