:: What is PPTP
The Point-to-Point Tunneling Protocol (PPTP) is a method for implementing virtual private networks. PPTP uses a control channel over TCP and a GRE tunnel operating to encapsulate PPP packets. – WikiPedia
:: Verifying PPTPd is working

:: How to setup pptpd vpn in Debian Linux
+ Installing pptpd

+ Configure pptpd

setup or change on these line:

* = your server ip
** = ip address for clients
+ Setup DNS Server for clients (Google public DNS)

uncomment or setup in these line, like:

+ Create user login info for PPTP VPN

add username anda password for the clients, example:

+ Setup MTU

add this line :

+ Restarting pptpd

:: Setup Firewall
+ Enable NAT connection

* = your server ip
+ Save configuration

:: Enable ip forwarding

add this line:

then apply the configuration

:: Links
+ Google
+ PutDispenserHere