Point to Point Tunneling Protocol

lastmod 2025-07-17created 2014-10-0212 edits

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.

Troubleshooting

Describes how to solve problems related to PPTP.

When there is no internet access while connected to a VPN (client) on Windows

• When there is no internet access while connected to a VPN (client)

Describes how to fix the problem where the internet connection does not work while the client side is connected to a VPN on Windows.

1. Network Connections
2. Right-click the Virtual Private Network (VPN) icon
3. Properties
4. Networking tab
5. Select Internet Protocol (TCP/IP)
6. Properties
7. Advanced
8. General tab
9. Uncheck "Use default gateway on remote network"

Troubleshooting remote access VPN on Windows

• [http://msdn.microsoft.com/ko-kr/library/cc772616(v=ws.10.aspx Troubleshooting remote access VPN]

If error message 800, saying the VPN server connection is not possible, occurs, solve it as follows.

• If ping is allowed rather than blocked between the client and the VPN server, ping the VPN server. Make sure you are connected to the network and that packet filters configured on the VPN server are not blocking communication.
• By default, when you configure the Routing and Remote Access service in the VPN server role, only PPTP and L2TP/IPsec packets are allowed on the VPN server's internet interface. ICMP (Internet Control Message Protocol) packets used by the ping command are filtered. To use ping on the VPN server, you must add input and output filters that allow ICMP traffic.
• To allow PPTP traffic, configure the network firewall to open TCP port 1723 and forward IP protocol 47 for GRE (Generic Routing Encapsulation) traffic to the VPN server. Some firewalls refer to IP protocol 47 as VPN or PPTP passthrough. Some firewalls do not support IP protocol 47. You may need to upgrade the firmware.
• To allow L2TP traffic, configure the network firewall to open UDP port 1701 and allow IPsec ESP-formatted packets (IP protocol 50).
• Verify that the VPN server is listening for PPTP traffic on TCP port 1723 and L2TP traffic on UDP port 1701. Enter the following at the command line on the VPN server.

netstat -aon

See also

• VPN
• PPTP
• Poptop: The PPTP Server for Linux
• VPN Activator: L2TP & PPTP VPN server for MAC.
• Layer 2 Tunneling Protocol (L2TP)

Favorite site

• Wikipedia (en) description of PPTP
• Creating a VPN server (PPTP) on Windows and sharing the internet connection ¹
• Windows-7 PPTP virtual private network (VPN) settings ²
• VPN frequently asked questions ³

References