detecting VPN connect/disconnect on Ubuntu
 

Hi
I'm using Ubuntu's Network Manager to connect to a PPTP VPN.
I have a data mining application that should only run when VPN is connected.
I need to run it when VPN connected & Kill it when VPN disconnected.
How Can I detect VPN connect/disconnect using shell script.

Would it be sufficient to detect the VPN being up or down by pinging the server to be connected to, and using the output (grep for 'bytes from') to determine if the server is reachable or not?

I need to check my own box's VPN connection to see it is connected or not & the server is not important for me (the network manager should handle it)
It's possible that VPN server be reachable (and connectable) but the VPN connection be disconnected! (User disconnect it, connection dropped & ...)