Wingate VPN and PPOE problem

[LMAG]

I'm using the latest VPN client (v1.2.3) and Wingate server software. When using the VPN client software on a ADSL PPOE PC (Internet provider Bostream in Sweden tested from two different locations) with Windows XP SP1a the service doesn't work OK.
It's possible to connect and ping computes behind the Wingate server but as soon as you put some load on the connection it dosen't work. The connection remains on but i'ts not possible to ping (time out) the Wingate server or the other computers behind it. With load I mean a SQL server application or VNC Viewer as some examles. The VNC viewer allows log in but you only get a black window. You have to disconnect the VPN connection and connect again to get the ping tor work again.
I have tested the client from several ADSL connections without PPOE and it works OK to the same Wingate server.
Any suggestions?

[adrien]

Hi

This sounds like an MTU issue. WIth PPPoE, the MTU of your link is normally reduced by about 8 bytes, and the VPN reduces it further. I think we have a registry key override you can set to tell WinGate VPN to use a reduced MTU - will get the guys that know this one to respond.

Adrien

[genie]

Hi,

Yes, there is a registry key to reduce MTU forcefully. However, it does not affect TCP traffic going through VPN channel - it is supposed to be discovered by the client' system. To make sure this problem MTU-related one, try reducing MTU value on the client side: for 2k/XP systems locate registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces then find the interface your client computer communicates with Wingate and inside this interface key add DWORD value MTU with decimal value 1400 (for example). You might need to reboot the client machine after having made this change. Let me know if this alteration makes a difference.

[genie]

One more thing to try (and probably it should be the first one) - try reducing MTU on the server for this PPPoE interface - if it is reduced the VPN channel that uses this interface will reduce it's own MTU and re-negotiate channel MTU with the other side.

[LMAG]

I've tested to reduce the MTU value to 1400 decimal on the client machine and now it works OK!

[genie]

That's great! However, we will need to fix our MTU discovery mechanism for VPN...