A processor of a mobile device operates to establish communications for a communications application by performing the following acts upon invocation of the application when the mobile device is connected in a communication network outside of a private network. Initially, the processor causes a request for a VPN connection with the private network to be communicated, and awaits the establishment of the VPN connection. If the VPN connection is established within a predetermined period of time, the processor operates to receive a private IP address of the private network and cause a request for registration using the private IP address to be communicated to a registration server for the private network. If the VPN connection is not established within the predetermined period of time, the processor causes a request for registration using a public IP address to be communicated to a registration server for the communication network.