Archived from groups: comp.dcom.vpn (More info?
> anyone knows which ports I have to open up on the router in order to use
> Microsoft's PPTP wan drivers - VPN?
Firstly, you need to open up for GRE protocol, which has no ports - it's
not TCP or UDP, it's its own protocol. Not all routers will support you
making an exception for this protocol.
In addition to that, you need TCP port 1723.