Now you should edit /etc/pptpd.conf and add the following lines
NOTE: Where localip is IP address of your server and remoteip are IPs that will be assigned to clients that connect to it.
Setup Authentication for PPTP
NOTE: Where client is the username, server is type of service – pptpd for our example, secret is the password, and IP addresses specifies which IP address may authenticate. By setting * in IP addresses field, you specify that you would accept username/password pair for any IP.
Add DNS Server
Restart PPTP Service
It is important to enable IP forwarding on your PPTP server.
This will allow you to forward packets between public IP and private IPs that you setup with PPTP.
Create a NAT rule for iptables
Setup PPTP Clients
Install PPTP Client
Open Network Connections, VPN tab, click on Add button.
Select Point-to-Point Tunneling Protocol (PPTP) from the list then click Create button
On the Gateway type the PPTP Server public IP Address
Click on the Advanced button to open PPTP advanced Options.
On the Security and Compression check ONLY Use Point-to-Point Encryption (MPPE), Security: All available (Default), allow Deflate data compression, Use TCP header compression.
Fix GRE Protocol
If you are behind firewall/squid you may be face GRE Protocol errors