You want to run an OpenVPN server on a debian-like system with a dynamic IP address (f.i. behind a consumer cable modem access)
You need to provide a fixed IP address in the openvpn configuration
Ensure the OpenVPN configuration is updated with each IP address change and reload the server
In order to run an application upon IP address change, you need to create a hook inside /etc/dhcp/dhclient-exit-hooks.d .