PPTP

A PPTP^4.4 VPN type works by providing a PPP session with the recipient through the tunneling GRE protocol. It needs another network connection to start and manage PPP session that runs on port 1723 TCP. In IPBrick's case, you have to indicate who are the users that access VPN-PPTP connections, as well as the address range that will be used by clients.

Footnotes

... PPTP^4.4

Point-to-Point Tunneling Protocol