If you cannot connect to a PPTP server, check the following items.
To check that your connection to the Internet is working properly
1. Ping www.microsoft.com.
2. If ping does not reach www.microsoft.com, type:
ping 207.68.156.163. If ping succeeds, you are properly connected to the Internet but you are not properly connected to your DNS server.
4. If ping fails, you might not be connected to the Internet. Contact your ISP.
Ping the IP address of the PPTP server.
If you receive a response, you are properly connected to the PPTP server, and you might have entered an incorrect user name or password.
If you do not receive a response, the administrator of the PPTP server might have turned on PPTP filtering. This prevents you from pinging the PPTP server. Contact the administrator of the PPTP server.
Firewalls sometimes filter out PPTP packets. Contact your ISP and the administrator of your corporate server and ask if they are using a firewall. If they are, request that they pass TCP port 1723 and IP protocol 47.
Note IP protocol 47 is the Generic Routing Encapsulation (GRE) protocol.
Because PPTP is a secure protocol, adding TCP port 1723 and IP protocol 47 will not affect the security of the firewall.
Contact your ISP and ask if it filters out GRE packets. If so, request that it pass GRE protocol 47.
It is not possible to create a PPTP tunnel that passes through a proxy server such as a computer running Microsoft Proxy Server. Therefore, if your internal network’s proxy server handles all Internet traffic, including PPTP traffic, you will not be able to create a PPTP tunnel to access resources on the internal network.
However, it is possible to configure a proxy server as a PPTP server in order to securely access resources on the proxy server. It is also possible to set up a secure PPTP connection on a separate computer instead of sending your packets through a proxy server. For more information, contact the administrator of the PPTP server.