http://silverlinux.blogspot.hk/2012/05/how-to-pptp-vpn-on-ubuntu-1204-pptpd.html - https://www.google.com.hk/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8&client=ubuntu#q=ubuntu%20pptp%20server%20no%20encryption http://silverlinux.bl…