Howto:How can I make sure that PPTP connections are kept alive?

When permanent PPTP connections are used with dial-on demand dialup connections, the tunnel may not work because of the router closing the dialup connection after a timeout. To work around, the PPTP keep-alive timer can be adjusted.

Applies To

This information applies to all PPTP-capable innovaphone devices.

More Information

Problem Details

When permanent PPTP connections are used with dial-on demand dialup connections, the tunnel may not work because of the router closing the dialup connection after a timeout. This can happen for various reasons, e.g. because the payload traffic is sent as GRE protocol packets, not as TCP or UDP. Dialup implementations may not trigger the connection when GRE traffic is due.

Solution

A solution is to adjust the PPTP keep-alive timer for the PPTP control connection (which is TCP-based) such that it is shorter than the router timeout.

The configuration can be done in the config file:

config change PPTP /patience seconds

will force the PPTP module to send keep-alive messages through the control connection every seconds seconds.