PPTP does not work externally

Question

I have a PPTP server that I can connect to using its LAN IP, but not using the external IP. My router is set up to forward PPTP to the correct machine and the server can access the internet. However, I cannot use my public IP to connect to the server.
Is there a setting in pptpd that blocks external connections, or is this more likely to be a problem with my router?
I have successfully used a PPTP server on the same network before.
(It was running on the same machine, but the OS has since been reinstalled. Could that have an effect on the current setup? What about assigning it a new local IP?)

Running ubuntu server 14.04

Answer 1

You don't provide much informations.

Basically, for the PPTP tunnel to be built, two things are needed :

. a TCP connection ( over port 1723 by default. I'll assume you'll be using TCP 1723 )

. a GRE connection ( GRE is IP protocol 47 )

First the TCP 1723 connection will be set-up, then the GRE tunnel will be built beside.

my advice : watch your /var/log/syslog file to monitor exactly what datas manage to reach your PPTP server, and to monitor the PPTP connection build-up process. Samely, running wireshark on the PPTP server while attempting a connection will show you what's really happening.

You don't say what OS and distro the PPTP server is ( I assume it's a Linux distro). From my experience, there are no special setup on the pptp server side for wan access.

( But my experience is limited to running PPTP servers on Debian )

As for the router, you need [TCP 1723] forwarded to [your pptp server IP/ TCP 1723 port].

Finally, your router MIGHT not enjoy you performing "External access FROM the lan" ( because of GRE, routers'firewalls have a hard time with PPTP). I don't have this problem, but you might. So too try a Wan connection FROM the real ouside.