Middlebury

Advanced Network Troubleshooting

Generic Network Troubleshooting Tips

When you're dealing with an intermittent or seemingly unresolvable network issue, try this tip: update BIOS, update NIC driver, use a NEW and SHORTER (!) ethernet cable.

How to check the NIC speed

Windows XP: https://mediawiki.middlebury.edu/wiki/LIS/Image:Check_NIC_speed_in_XP.JPG

In which order does Windows connect to the network when connected wired and wireless

See http://technet.microsoft.com/en-us/library/bb878031.aspx  and http://arstechnica.com/civis/viewtopic.php?f=10&t=34661

It is possible to specify a specific order: Start => Control Panel => Network => Advanced menu => Advanced Settings. Use the arrows to move the wired (LAN - local ethernet) above wireless.

Troubleshooting Vista Connectivity Issues

Ideally, you would test the jack with a known good computer or the Fluke NetTool (the gameboy). If you find that the jack is working with another computer (or with the nettool), proceed down this list for ideas to try:

  • Try plugging a hub into the wall jack, then plug the vista machine in the hub - does this resolve the issue? If so the problem is signal strength (yes, the wired network also depends on a signal).
  • Update drivers
  • Disable IPv6
  • Disable firewall (Windows or 3rd party)
  • Disable autotuning (cmd => netsh interface tcp set global autotuninglevel=disabled ), per http://support.microsoft.com/kb/934430
Disabled TCP auto-tuning with command "netsh interface tcp set global autotuninglevel=disabled)
Disabled TCP receive-side scaling state with command "netsh interface tcp set global rss=disabled)
Dear All
I had the same issues, tried all the stuff but nothing helped until I stumbled over the following Technet Article
http://technet2.microsoft.com/WindowsVista/en/library/3ed3d027-5ae8-4cb0-ade5-0a7c446cd4f71033.mspx?mfr=true
And by simply using the command
netsh wlan show all

I saw that my WLAN adapter (in a 4 years old Thinkpad R50P) was not supporting the WAP PSK option with AES but only with TKIP.
After adjusting this little setting, the issues were gone.
Cheers and good luck
  • In regedit, navigate to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\(your wireless network adapter) Set DWORD DhcpConnForceBroadcastFlag to 0
  • May be a routing issue on the client:
To verify the routing to this address, I disconnected all cables and deactivated the wireless card, and consulted the routing table using the command:
ROUTE PRINT
and it showed a spurious entry of 0.0.0.0. I deleted it using:
ROUTE DELETE 0.0.0.0

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