L2TP VPN Setup on Ubuntu Terminal

If you want to connect to a L2TP VPN server from your Ubuntu Terminal, you can do it using the xl2tpd package and the ppp (Point-to-Point Protocol) daemon.

Here's how:

Prerequisites

• A L2TP VPN server to connect to
• Ubuntu Terminal (version 18.04 or later)

Installation

First, install the necessary tools:

sudo apt-get update
sudo apt-get install xl2tpd ppp

Configuration

Create a file /etc/ppp/chap-secrets with the following content:

# Secrets for authentication using CHAP
# client        server  secret                  IP addresses
your_username   *       your_password_here      *

Replace your_username and your_password_here with your actual VPN username and password.

Next, create a file /etc/ppp/peers/l2tpd with the following content:

remotename l2tpd
linkname l2tpd
require-chap
refuse-pap
refuse-eap
refuse-mschap
noauth
# Example PPP configuration for a Linux client connecting to a
# SonicWALL device running L2TP Server:
# debug
# logfile /var/log/l2tpd.log
# connect-delay 5000
# noccp
# idle 1800
# mtu 1200
# mru 1200
# file /etc/ppp/options.l2tpd
# require-mppe
ipparam l2tpd
defaultroute
replacedefaultroute
usepeerdns
# make the VPN connection automatically reconnect after connection drops
persist

If you need to specify additional options, you can create a separate file /etc/ppp/options.l2tpd and include it in /etc/ppp/peers/l2tpd.

Next, edit the file /etc/xl2tpd/xl2tpd.conf and add the following lines at the end (replace vpn.example.com with your VPN server's domain or IP address):

[iprange]
    ip_range = 192.168.2.100-192.168.2.200
[lns default]
    ip range = 192.168.2.1-192.168.2.99
    local ip = 192.168.2.1
    require chap = yes
    refuse pap = yes
    require authentication = yes
    name = L2TPD Server
    ppp debug = yes
    pppoptfile = /etc/ppp/peers/l2tpd
    length bit = yes
    hostname = vpn.example.com

Replace 192.168.2.1 with your local IP address.

Finally, restart the services:

sudo service xl2tpd restart
sudo service pppd restart

Connect to the VPN

You can now connect to the VPN by running the following command:

sudo pon l2tpd

To disconnect, run:

sudo poff l2tpd

That's it! You should now be able to connect to your L2TP VPN server using the Ubuntu Terminal.

Troubleshooting

If you encounter any issues, check the logs for errors:

tail -f /var/log/syslog | grep pppd
tail -f /var/log/syslog | grep xl2tpd