Q:

How to determine which traffic goes over the PPTP VPN?

I setup a PPTP VPN on mac os x lion, on the advanced tab I do not have the send all traffic over VPN connection checked. I only want traffic to a specific server connected to go through the vpn, everything else should not be sent over the vpn.
Where do I look to find out which IP addresses will be included for traffic over the vpn and which ones will not?

A:

Have you tried using the route command to declare a static route?
For instance, I use the following with my VPN:
sudo route -v -net 10.41.0.0 -netmask 255.255.0.0 -interface ppp0

This tells any traffic going to 10.41.x.x to go over the VPN interface (ppp0).

