16 NOV 2014
This guide has been tested with CentOS 7 server.
Setup PPTP Server
First we need to install pptp server using yum
# yum install ppp pptp pptpd pptp-setup
Then we need to configure the pptpd
# vim /etc/pptpd.conf
Add server IP and client IP at the end of the file like below
localip 192.168.0.1
remoteip 192.168.0.100-200
This sets up the PPTP server to use IP 192.168.0.1 while distributing the IP range 192.168.0.100 to 192.168.0.200 to PPTP clients. Change these as you wish as long as they are private IP addresses and do not conflict with IP addresses already used by your server.
Configure DNS servers to use when clients connect to this PPTP server
# vim /etc/ppp/options.pptpd
Uncomment the ms-dns and change them to google like below or OpenDNS
ms-dns 8.8.8.8
ms-dns 8.8.4.4
Now add a VPN user in /etc/ppp/chap-secrets file
# vim /etc/ppp/chap-secrets
The column is username. Second column is server name, you can put pptpd in there. Third column is password. The last column is the IP addresses, you can put * to allow all IP.
# client    server      secret          IP addresses
username    *       myPassword      *
Finally start your server
# service pptpd restart
To start PPTP Daemon automatically when rebooting next time, use the following command
# chkconfig pptpd on
Setup IP Forwarding
To enable IPv4 forward. Change /etc/sysctl.conf file, add forward rule bellow
# vim /etc/sysctl.conf
Add the following line
net.ipv4.ip_forward=1
Then reload the configuration
# sysctl -p
Add forward rule to iptables
# vim /etc/rc.local

iptables -t nat -A POSTROUTING -s 192.168.0.0/24 -o eth0 -j MASQUERADE
iptables -A FORWARD -p tcp --syn -s 192.168.0.0/24 -j TCPMSS --set-mss 1356
To ensure that /etc/rc.local script is executed during boot run the following
# chmod +x /etc/rc.d/rc.local
You are done. Just reboot your server and you should be able to connect to using PPTPD and send all your traffic through this server.
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