Windows SBS 2011 - NAT-T Traversal VPN

Good Afternoon,

We have recently installed an SBS 2011 domain into a building where we do not control the access to the outside world. The ISP has enabled Port 1723 to forward to our SBS 2011 server.

The problem is that after setting up Routing and Remote Access I can't dial in (using the PPTP VPN), nor actually can any machine on the domain dial out to any Windows VPN - i.e. if I wanted to connect to my home VPN.

The ISP is saying this is to do with NAT-T Traversal, is there or how do I:

a) Fix this on the RAS box allowing incoming connections
b) Tweak this to allow machines on the network to connect to other VPNs!

Many thanks

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Cliff GaliherCommented:
If you don't control the network edge then you simply can't. You need port 1723 and the GRE protocol (not port) forwarded. It sounds like the network edge is blocking GRE this PPTP inbound and outbound would fail. If they won't fix it, there is nothing you can do.

mattstannardAuthor Commented:
Hi Cliff,

I'm speaking nicely to them - the GRE Protocol also applies to Windows I take it :-)

Cliff GaliherCommented:
GRE is part of the PPTP RFC, so all PPTP tunnels require it, Linux, windows, doesn't matter.


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