L2TP over IPSec VPN with Radius

http://www.debuntu.org/how-to-set-up-a-l2tp-over-ipsec-vpn-using-a-radius-backend/
http://www.debuntu.org/how-to-set-up-a-l2tp-over-ipsec-vpn-using-a-radius-backend-page-2/
http://www.debuntu.org/how-to-set-up-a-l2tp-over-ipsec-vpn-using-a-radius-backend-page-3/