SSTP Tunnel establishing successful - but no stable RDP

[a.woll]

Good morning/afternoon/evening/night everybody,

i set up Softether VPN on Ubuntu LTS 12.04.4.
The server seems to work normally, users are authenticated and receive via dhcp ip addresses from LAN.

A normal ping from the client to a lan server succeeds without packet loss.
But an RDP connection breaks a lot of time or is simply unstable.

I've got only one public address served by an Bintec RS120 router which NAT port 443 TCP to the Softether VPN server.

I'm still playing with MTU setting on the nic which connects the VPN server to the router, but the results aren't satisfying.

MTU on the WAN interface is set automatically by the router itself. The internet connection is established by PPPoE.

I've got no tunnel shutdowns or break ups. The tunnels are stable.
Ping results are ok from client to an lan server behind the VPN server.
Ping results from VPN server to client are sometimes lost. I hope to get
rid of this by finding good settings.

I'm not using SecureNAT on the VPN server.
My VirtualHub is bridged to internal LAN interface.

Do you have an idea, where else I've got to look?

Thank you.

[thisjun]

Is there any error message in VPN server log or RDP client or sever log?

[a.woll]

I found my mistakes,

interestingly I got issues within debian based linux. I tested Ubuntu and Debian in 32bit and 64bit flavours.

watch d ifconfig -a showed always droppings of RX-Packets after set the nics with static IPs. This issue didn't show up by using DHCP on all interfaces.

I set up the machine on CentOS 6.5 now and it's working like a charm. :-)
No packet droppings anymore.

Unfortunately I wasn't able to find out, why the linux distributions on Debian made things complicated.

Andreas