vpn pasthrough? Are you sure? We don't need to configure it normally.
http://www.tp-link.com/en/faq-558.html

Hi,

thanx for the link.

All TP-LINK routers support VPN Passthrough for PPTP, L2TP and IPSec (ESP).

That doesn´t mean it´s already enabled, and, I can´t find a point in the config, that´s like the screenshot or sounds similiar.

Before the TP-Link only a W900V internet router passes the vpn requests to the local network. Works fine for a long time.
Now the tp-link is between the W900V and my local network and I cannot authenticate to my inner Server via VPN anymore.

Any ideas?