Ubuntu – L2TP IPsec VPN client on Ubuntu 14.10

That's not the best way (because Openswan has been removed from Unicorn (14.10) by some security reasons), but it works pretty good for me:

1. Download and install an appropriate Openswan package from the http://www.ubuntuupdates.org/pm/openswan

I use package trusty (14.04) for my Unicorn (14.10) and it works without any issues.

2. Then you need to install Network Manager L2TP plugin. I use the bellow one, it has a version for Unicorn:

   sudo apt-add-repository ppa:seriy-pr/network-manager-l2tp
   sudo apt-get update
   sudo apt-get install network-manager-l2tp-gnome
   sudo service xl2tpd stop
   sudo update-rc.d xl2tpd disable
   

3. Then just go to the Network manager, choose VPN connections and create l2tp. You need only set up a username, password and the IPSec PSK in the IPSec additional settings

Hope it'll help you! And good luck

You can use

sudo add-apt-repository ppa:nm-l2tp/network-manager-l2tp  
sudo apt-get update  
sudo apt-get install network-manager-l2tp
sudo apt-get install network-manager-l2tp-gnome

To install the network manager l2tp that supports L2TP for ubuntu 16.04

Walkthrough for building from source: http://blog.z-proj.com/enabling-l2tp-over-ipsec-on-ubuntu-16-04/