pptpclient can act as either
This protocol allows you to implement a secure point-to-point connection by creating a tunnel in an insecure network.
The work of PPTP is to implement PPP frames in IP packets for transferring them to any IP network, including the Internet. In addition, this technology can be used to create a tunnel between local networks.
A TCP connection is used to service the created PPTP tunnel.
The protocol specification was published in 1999 in RFC2637, but the IETF community has not ratified it.
Less secure than IPSec, PPTP establishes a PPP session using the GRE protocol. The 1723 TCP port is used to control and initiate the GRE connection. Redirecting PPTP to the firewall is difficult because the protocol requires two sessions to be established simultaneously. Continue reading