PPTP VPN is most simple and convenient way for remote users to connect to a network. For PPTP to work following are the requirement.
1. The VPN router has to have a public IP on it.
2. Port 1723 should be made open by ISP.
(or)
1. Port 1723 should be made open by ISP.
2. The modem should be configured to do port forwarding to VPN routers WAN side private IP, so whenever there is a VPN traffic comming in for port 1723 on the non VPN modem/router it will be forwarded to the VPN router on the LAN.
Note: Port forwarding is not a reliable solution. It is recommended to set the VPN router in such a way it gets the public IP.
