Patent ID: 8111614

Claim:
A method of providing back-up voice services, comprising: periodically sending from an IP-PBX server to an IP-Centrex server remote from the IP-PBX server sufficient information to provide at least one of dialing and incoming call routing by the IP-Centrex server should the IP-PBX server become unresponsive without having to request additional information from any server associated with a company hosting the IP-PBX server after the IP-PBX server becomes unresponsive; periodically sending to the IP-Centrex server status information about plural user voice terminals serviced by the IP-PBX server for use by the IP-Centrex server after the IP-PBX server becomes unresponsive; detecting that the IP-PBX server serving the plural user voice terminals has become unresponsive; configuring the IP-Centrex server to handle voice calls for the unresponsive IP-PBX server without having to request additional information from any server associated with the company hosting the IP-PBX server after the IP-PBX server becomes unresponsive; configuring a DNS server to provide to the plural user voice terminals, in response to a request to resolve a name of the unresponsive IP-PBX server, a first IP address of the IP-Centrex server remote from the unresponsive IP-PBX server instead of a second IP address of the unresponsive IP-PBX server; handling calls from the plural user voice terminals at the IP-Centrex server at the first IP address; detecting that the unresponsive IP-PBX server has come back online; configuring the DNS server to provide to the plural user voice terminals, in response to a request to resolve the name of the IP-PBX server, the second IP address of the IP-PBX server after detected that the previously unresponsive IP-PBX server has come back online; and handling calls from the plural user voice terminals at the IP-PBX server at the second IP address.