:: 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:

* 1.2.3.4 = your server ip
** 10.0.0.1-200 = 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

* 1.2.3.4 = your server ip
 
+ Save configuration

 
:: Enable ip forwarding

add this line:

then apply the configuration

 
:: Links
+ Google
+ PutDispenserHere