Configure PPTP in Ubuntu

Install packages

apt-get install pptp-linux

Configure password

vi /etc/ppp/chap-secrets

The format should be

pptpuser    PPTP    pptppassword    *

Create route script

Create file /etc/ppp/ip-up.d/route-traffic

#!/bin/bash

route add -net 192.168.1.0/8 dev ppp0

Change mode to executable

chmod +x /etc/ppp/ip-up.d/route-traffic

Create dial up configure

The name of file is defined as connection name, such as /etc/ppp/peers/<CONNECTON>

pty "pptp <HOST> --nolaunchpppd"
name <USER>
remotename PPTP
require-mppe-128
file /etc/ppp/options.pptp
ipparam <CONNECTON>

Open filewall

iptables -A INPUT -i pptp -j ACCEPT
iptables -A OUTPUT -o pptp -j ACCEPT

Connect and disconnect

pon <CONNECTON>
poff <CONNECTION>

Troubleshooting

If didn't configure PPTP Passthrough on your NAT, then PPTP will failed.

PPTP uses a TCP channel on port 1723 for control and the GRE protocol to encapsulate data and create a VPN tunnel. The issue isn’t really PTPP itself but GRE; GRE doesn’t use ports. Since a requirement of NAT is that the connection must use an IP address and port number it doesn’t work with GRE. This is what PTPP passthrough addresses.

References

Set up Linux PPTP Client from the Terminal
Connect to PPTP server via command line on Ubuntu
pptp - 'Administrative Shutdown'. Error code is 0, Cause code is 0