Yes, the update to agent settings is a push method... Did you enable the Run mini-scan when IP Address changes setting in your agent? That way the device should send a mini-scan with it's IP address as soon as it connect with VPN and gets a new IP. You do need to enable communication between the client and the LANDesk Core Server over port 5007 (inventory) for this to work.
Thanks for the information Frank. I dont have the mini-scan running but I will enable it which will resolve a couple problems.
It will for sure make your systems more managable. Still, you need somehow to update the agent and that will be your challenge... Maybe use an Advance Agent msi in a GPO to re-install the agent?