Ubuntu Old VPN

Ubuntu has stopped shipping L2TP over IPSec support for Ubuntu since Precise. A workaround for this exists using network-manager-l2tp.

First you must install the prerequisites:

sudo apt install intltool
sudo apt install libtool
sudo apt install network-manager-dev
sudo apt install libnm-util-dev
sudo apt install libnm-glib-dev
sudo apt install libnm-glib-vpn-dev
sudo apt install libnm-gtk-dev
sudo apt install libnm-dev
sudo apt install libnma-dev
sudo apt install ppp-dev
sudo apt install libdbus-glib-1-dev
sudo apt install libsecret-1-dev
sudo apt install libgtk-3-dev
sudo apt install libglib2.0-dev
sudo apt install xl2tpd
sudo apt install strongswan

Then build the network manager again:

git clone https://github.com/nm-l2tp/network-manager-l2tp.git  
cd network-manager-l2tp  
autoreconf -fi  
intltoolize

Make sure no errors have occurred.
Configure the build:

./configure \
  --disable-static --prefix=/usr \
  --sysconfdir=/etc --libdir=/usr/lib/x86_64-linux-gnu \
  --libexecdir=/usr/lib/NetworkManager \
  --localstatedir=/var \
  --with-pppd-plugin-dir=/usr/lib/pppd/2.4.7

Make sure no errors occurred.
Then make it:

make  
sudo make install

Remove AppArmor settings for IPSec:

sudo apparmor_parser -R /etc/apparmor.d/usr.lib.ipsec.charon
sudo apparmor_parser -R /etc/apparmor.d/usr.lib.ipsec.stroke

Replace x2ltpd with libpcap:

sudo apt remove xl2tpd  
sudo apt install libpcap0.8-dev

wget https://github.com/xelerance/xl2tpd/archive/v1.3.6/xl2tpd-1.3.6.tar.gz
tar xvzf xl2tpd-1.3.6.tar.gz
cd xl2tpd-1.3.6
make
sudo make install

Now restart your machine. Network Manager should now have an option to use a L2TP VPN connection.

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

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