A method and system, employing IP telephony, for providing continuous, uninterrupted voice communications during disaster conditions wherein the disaster site telephone infrastructure has been rendered inoperable or inaccessible. The system uses Voice over IP (VoIP) and emerging IP telephony standards to enable users to receive telephone calls, normally destined for their work phone, at a personal computer terminal connected to the Internet. Users can also place calls from their terminal to the PSTN or to other users on the system. Combining telephone line redirection with IP telephony capabilities enables the construction of a system that provides users with unlimited flexibility in responding to a severe business interruption with full voice communications. The system can be customized so calling parties will be presented with precisely the same greetings and messages, for each user telephone extension, that were present in the disaster site's telephone system. Switching from the disaster site's telephone infrastructure to the system can be accomplished in minutes.