Create a VPN on Linux with Poptop

06 Jan 2010 at 00:00:00 - 0 comment(s)

You are using Linux and you need to create a VPN where both Windows and Linux users will be able to use really easily. This post is done for you. In few lines we will see how to install and configure Poptop, an open source PPTP server for Linux. On top of that we'll see the options you need in the kernel as well as how to configure iptables properly if ever you use it. Then how to connect to it using pptpclient on Linux which is the client for the proprietary Microsoft Point-to-Point Tunneling Protocol, PPTP. Finally we'll see how to connect to your VPN on Windows.

The Kernel

Most of the people don't compile their own kernel, I do. So for people like me, this might be useful to them. So simply in image what you need:

kernel options for PPTP


If you are using iptables, you have to add some rules:

iptables -A INPUT -i ppp+ -j ACCEPT
iptables -A OUTPUT -o ppp+ -j ACCEPT

iptables -A INPUT -p tcp --dport 1723 -j ACCEPT
iptables -A INPUT -p 47 -j ACCEPT
iptables -A OUTPUT -p 47 -j ACCEPT

iptables -F FORWARD
iptables -A FORWARD -j ACCEPT

iptables -A POSTROUTING -t nat -o eth0 -j MASQUERADE
iptables -A POSTROUTING -t nat -o ppp+ -j MASQUERADE

echo 1 > /proc/sys/net/ipv4/ip_forward

That's it for iptables.

Install and configure poptop

If you are using archlinux (the package name is probably similar or the same in other distributions)

pacman -S pptpd

You now need to configure poptop by editing its configuration file:

vi /etc/ppp/pptpd-options

An example of pptpd-options:


name pptpd




I am using mschap-v2 (it's Microsoft Challenge Handshake Authentication Protocol version 2) and MPPE 128-bit (Microsoft Point-to-Point Encryption). If you want to know more, you can check the documentation for this configuration file.

You need to add users that will be able to connect to your VPN by editing chap-secrets:

vi /etc/ppp/chap-secrets

Here is a sample:

# Secrets for authentication using CHAP
# client        server  secret                  IP addresses
marc            pptpd   "mypassword"            *

That's it, we are done with the installation and configuration of poptop. You can start it with /etc/rc.d/pptpd start (for archlinux, on debian based distributions such as ubuntu it will be /etc/init.d/pptpd start). Let's see how to connect to it on Linux using pptpclient.

Configuring the client on Linux with pptpclient

First you need to install pptpclient

pacman -S pptpclient

You need to create one file (you can call it the name you want):

vi /etc/ppp/peers/inebium

The content of the file is ( is the IP address of the server that hosts the VPN):

pty "pptp --nolaunchpppd"
name marc
remotename pptpd

As you did for the server you need to edit /etc/ppp/chap-secrets

# Secrets for authentication using CHAP
# client        server  secret                  IP addresses
marc            pptpd   "mypassword"            *

Done. You can now connect to the vpn like this (where what is following pon is the name of the peer file you created earlier):

pon inebium

Don't forget you need to have the proper ppp module loaded:

modprobe ppp_mppe

Configuring the client on Windows

On Windows XP, in Network Connections -> Create a new Connection -> Connect to private network (Virtual Private Network) -> Connection to Virtual Private Network -> Name of the company (you can put whatever) -> Then you are asked for the ip address of the server where you've configured poptop -> That's it, you enter the username and password you've put in the chap-secrets file and click on Connect.


In few basic steps, we've seen how to setup a VPN on GNU/Linux with poptop which is based on the PPTP protocol. We went through what was required in the kernel + the configuration of iptables and finally how to connect to our configured VPN using pptpclient on Linux. I hope this post will be helpful for you.


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