Multiple (but not all) VPN clients failing in Windows 8 and 8.1

Question

Big question for VPN gurus, with a long story.  I got a new machine with Windows 8 in late December 2012.  I work remotely
for a bunch of different customers, so 100% of my work is done via VPNs.  My customers use a wide variety of VPN types.  These were all working fine up through early December 2013.  Suddenly a bunch of them stopped working.  I tried a ton
of stuff:
- Uninstalling all VPN clients and reinstalling them one at a time
- Reinstalling / updating network drivers
- Turning off and uninstalling antivirus and firewall software
- Verified problem was on my machine, not local network, both by testing other machines on local network and by testing this machine on other networks
The following VPN clients would not work:
Cisco VPN Client
FortiSSL
Microsoft built-in
The following VPN clients had no problems:
Cisco AnyConnect
ShrewSoft
Juniper web-based SSL VPN
Check Point web-based SSL VPN
As you can imagine, having to use a second (Windows XP) machine to connect to half my customers was a source of some serious headaches.  After 3 weeks of beating my head against this, I finally upgraded my OS to Windows 8.1.  The hail mary worked;
my VPN problems went away!
Two weeks later, the exact same symptoms resurfaced.  I've gone back through a bunch of the steps that didn't help the first time around, with the same results.  I expect a system refresh would probably do the trick, probably temporarily like the
OS upgrade, but I can't afford to spend a week reinstalling dozens of critical applications only to have the problem resurface after another couple of weeks.
At this point, the closest thing I have to a clue is that in both cases the problems started soon after installing an update to the Cisco AnyConnect client.  After uninstalling the client, the problems do not go away.
Exactly what do I mean when I say the VPN clients don't work?  That varies from one client to the next:
Microsoft built-in: Error 720
FortiSSL: variable - sometimes won't finish connecting, sometimes connects for about a second
Cisco: variable - sometimes won't finish connecting, sometimes "connects" but I can't access anything
Has anybody seen this sort of behavior before?  Any suggestions for fixes I may not have tried yet?  Thanks in advance.

Answer 1

Hi.
I have been similar issues with VPN clients. In my case cause of this problems seems to be "Deterministic Network Enhancer". So turning this component on and off usually helps.
Actually I writed one script to fix this probleem for my clients.
<#
.Synopsis
   This script is ment for a fixing of network problems which may occur when you use Windows 8/8.1 with Client Hyper-V
.DESCRIPTION
   This script will disable and then enable again Deterministic Network Enhancer (dni_dne) component from network connections.
   Parameter RegisterScheduledTask will register this script as a scheduled task which will be triggered at every  time when computer starts.
.EXAMPLE
   Fix-Network.ps1
.EXAMPLE
   Fix-Network.ps1 -RegisterScheduledTask
#>
param
    [switch]$RegisterScheduledTask
function Test-IsRunAsAdministrator
   $currentUser = New-Object Security.Principal.WindowsPrincipal( [Security.Principal.WindowsIdentity]::GetCurrent())
   $currentUser.IsInRole( [Security.Principal.WindowsBuiltInRole]::Administrator)
function Get-RunAsAdministrator
    if(!(Test-IsRunAsAdministrator))
        [string[]]$argumentList = @('-NoProfile' , '-File', $MyInvocation.ScriptName)
        if($RegisterScheduledTask)
            $argumentList += '-RegisterScheduledTask'
        Start-Process PowerShell.exe -Verb Runas -WorkingDirectory $PWD.Path -ArgumentList $argumentList
        break
Get-RunAsAdministrator
if($RegisterScheduledTask)
    $actionArgument = '-ExecutionPolicy Bypass -File  "' + $PSCommandPath + '"'
    $action = New-ScheduledTaskAction -Execute "C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe" -Argument $actionArgument
    $trigger  = New-ScheduledTaskTrigger -AtStartup
    $principal = New-ScheduledTaskPrincipal "SYSTEM" -LogonType ServiceAccount -RunLevel Highest
    Register-ScheduledTask -TaskName Fix-Network -Trigger $trigger -Action $action -description "Fix network for Windows 6.X with Hyper-V" -Principal $principal
else
    $bindings = Get-NetAdapterBinding | Where-Object { ($_.ComponentID -eq "dni_dne") -and ($_.Enabled)}
    $bindings | Set-NetAdapterBinding -Enabled $false
    $bindings | Set-NetAdapterBinding -Enabled $true
    $date = Get-Date
    "Done:  $date" > $PSScriptRoot\Fix-Network.log
Hope that this will help.
Br,
Heiki