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[I hope this is not off-topic here]

I'm trying to set up a PPTP tunnel between a Linux (Debian 6) Server and a Windows 7 Client.

The problem is, that the PPTP connection itself (ports 1723 and 47) must be tunneled via a custom program because the Linux server is behind a NAT. This tunnel is made by a custom Windows program that listens to ports 1723 and 47 (localhost) and forwards these TCP connections to to the remote server. This tunnel already works fine for generic connections like SSH and has been used for years now. It allows me to connect to any TCP port on the Linux server.

The problem with PPTP is, apparently, that it needs to transmit GRE packets which aren't TCP connections and thus don't reach the other network (and the VPN connection setup times out).

Can I configure the PPTP connection somehow so that it doesn't use these GRE packets or perhaps encapsulates them in a TCP connection?

Any other suggestions greatly appreciated.

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up vote 1 down vote accepted

No, this is not possible.

PPTP is using TCP port 1723 to build up the tunnel, but the data carried over the VPN always GRE.

This is then the IP protocol 47 (Not TCP!)

Anyway PPTP is security wise not a good solution and should be replaced by a better protocol.

OpenVPN is one of the flexible VPN solutions

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Thanks. I switched to OpenVPN. – Udo G May 13 '13 at 13:43

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