L2TP ipsec vpn setup scripts

This is a collection of scripts to help setup an L2TP IPSec client on CentOS 7. There are a bunch of tutorials out there, but I had a hard time finding a working solutiion. 🔥

If you used hwdsl2/setup-ipsec-vpn for the server, then these scripts should work. 👍

Tested on CentOS Linux release 7.5.1804 (Core). The client setup is mostly inspired by Archlinux wiki: Openswan L2TP/IPsec VPN client setup and adapted for CentOS 7

Getting started

1. Clone the project
2. Make sure scripts are executable
3. Setup your environment variables
4. Execute the setup script
5. Each time you want to connect, run the start script start_vpn_client.sh with sudo

git clone https://github.com/GabLeRoux/l2tp-ipsec-vpn-setup-scripts.git
cd l2tp-ipsec-vpn-setup-scripts
cp .env.example .env
vim .env
sudo setup_vpn_client.sh

sudo start_vpn_client.sh

Why Centos?

Please don't ask, that wasn't my idea.

Is this safe?

Read the scripts, I'm not your mom 😉. Running things from the internet as sudo is never safe friend.

Is this working?

Yes, it does work. Only the part for routing needs some manual actions. Refer to Archlinux wiki Routing section

Let's say there is this IP behind the VPN: xxx.xxx.xxx.xxx and you'd like your system to reach it using the ppp0 device (your vpn tunnel). You first need to get your ppp0 device peer ip:

ip a show dev ppp0

5: ppp0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1280 qdisc pfifo_fast state UNKNOWN group default qlen 3
    link/ppp
    inet 192.168.42.10 peer 192.168.42.1/32 scope global ppp0
       valid_lft forever preferred_lft forever

In my case, it's 192.168.42.1. We can get this with the following magic command:

ip -o -4 a show dev ppp0 | awk -F '[ /]+' '/global/ {print $4}'

Then you need to update your routing table to let your system know how to reach the desired server behind vpn using your ppp0 device. Command looks like that:

ip route add xxx.xxx.xxx.xxx via yyy.yyy.yyy.yyy dev pppX

or in my case:

ip route add xxx.xxx.xxx.xxx via 192.168.42.1 dev ppp0

What's my local ip?

ip a

It should be somewhere in here, look for eth0 or wlan0 if you're on a wifi.

Vagrant

Yeah I prefer Docker, but I had to setup something on an actual machine and docker has no such thing as systemctl. Here's how you can try this on vagrant:

cp .env.example .env
vim .env
vagrant up
vagrant ssh
sudo /app/setup_vpn_client.sh

It's a good idea to try it on a VM first so you don't polute your server before knowing it works.

I'm stuck with 'Errno 22: Invalid argument'

Yup, me too. See issue #1. Help me! 🔥

Contributing

Contributions are welcome, I may not maintain this project much, but you can open issues or send pull-requests. ✌️

License

MIT © Gabriel Le Breton