I have followed this guide to setup a pptp VPN server in Ubuntu (which is a VM in a Windows Host, bridged adapters): https://help.ubuntu.com/community/PPTPServer
My usage of the VPN is to overcome geoblock as I will be travelling to China.
I can connect to the VPN on my Android phone using the 4G connection, and when I type ifconfig in the terminal in Ubuntu it does show
ppp0 Link encap:Point-to-Point Protocol
However as soon as I connect to the VPN I loose internet on my phone.
My Ubuntu (and the Windows host) is behind a router, which I have port-forwarded 1723, alongside with ports 8080 for web servers etc.