Although the survivable remote server is the acting call controller, the branch gateway attempts to register with the main server every 30 s or whenever there are no active calls. This signaling also acts as keep-alive messages to the main server. The first registration request with the main server sets up encryption on the TCP link for H.248 messages. The branch gateway keeps the survivable remote registration until the branch gateway is accepted by the main server. Once registered with the main server, the branch gateway drops the survivable remote link. Once all branch gateways have migrated from the survivable remote server, that server unregisters all IP endpoints, which automatically reregister with the main server.

This automatic migration of branch gateways to the main server is administered to happen immediately (default), when there are no active calls, or at a scheduled time of a day.