Troubleshooting VNC and local network connectivity issues

Posted on 2009-02-09
Last Modified: 2013-11-30
I am having an issue with a cluster of Windows XP workstations and connecting to them with VNC. When initiating a session,  the screen on the target workstation loads about halfway down then the session stalls, breaking the connection. Currently, I'm using RealVNC 4.x server and have tried a variety of client viewers with the same result.

This issue is only prevalent when connecting to any machine in a  particular cluster of workstations that share the same Cisco Catalyst 2950 ethernet switch in unmanaged mode (default boot-up settings). Connections to other workstations and servers on the same lan and IP subnet connected through other switches (two other 2950's with assigned IP's and several other unmanaged workgroup switches do no exhibit this problem.

The workstations in question also typically fail to load the logon script from the domain controller on initial startup because the network adapters lag when acquiring a DHCP address or experience delays in connecting to the network on if assigned a static address. I suspect the two issues are  related and have something to do with the network adatpers. The workstations in question were purchased from the same vendor and installed at the same time all within the past year or so, and older machines on the same switch behave properly. Details about the network adapter problem can be found in this former question:

Any assistance would be appreciated.
Question by:Nozmoking
    LVL 63

    Accepted Solution

    1)  Do you have the latest NIC drivers ?

    2) have you tried a different NIC as a test ?

    3) Have you checked firewall settings, and reset the firewall config ?

    rom johnb6767

    What I like to do on any network problem....Is to reset it ALL....

    netsh int ip reset reset.log
    netsh firewall reset
    netsh winsock reset

    Then remove ALL NIC's from the device manager..
    In the Device Manager, select View>Show Hidden Devices

    (If the Show Hidden devices is not presetn, do the following command from a command prompt..)

    set devmgr_show_nonpresent_devices=1

    More information on that command here....
    Device Manager does not display devices that are not connected to the Windows XP-based computer

    Go back to Network Adapters, and make sure your adapters are all gone, including any older ones. (there will be several ' miniport' devices that are not able to be uninstalled....)
    Once they are all gone, reboot and let Windows reinstall them...

    Thats a total rebuild of your network connections, to hopefully correct any problems with Basic connectivity.

    I hope this helps !

    Author Closing Comment

    Thanks - the on-board NIC drivers had been updated a couple of times but it did not fix the problem. I threw another adapter in one of the machines and everything snapped into place nicely, so I went back to the OEM hardware supplier and was able to get yet a third updated driver for the on-board adapter. That one did the trick. Thanks.

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