By @sskaje
Link: https://sskaje.me/2013/10/notes-pptpl2tp-server-on-ubuntu/

From: https://help.ubuntu.com/community/PPTPServer and https://help.ubuntu.com/community/L2TPServer

This is an integrated & simplified intro about installing pptp/l2tp server on ubuntu 12.04.

Install

pptpd, xl2tpd, openswan are needed.
ppp should be installed by default, you can apt-get install ppp just for sure.
dnsmasq is needed to simplify dns issue.
So, just type commands:

sudo apt-get install pptpd openswan l2tpd dnsmasq

1	sudo apt-get install pptpd openswan l2tpd dnsmasq

Environment

Server ip is assigned as: 192.168.210.1
Client ip are in : 192.168.210.100~192.168.210.200

Notes: PPTP/L2TP Server on Ubuntu by @sskaje: https://sskaje.me/2013/10/notes-pptpl2tp-server-on-ubuntu/