We have a 3CX Windows PBX at a data center with about 15 remote sites. If a remote site's internet goes down, the extensions loses its registration. When the internet comes back up, the extensions do not register back. We would have to change the IP on the phones in order for the extension to register again. Does anyone know a better method than to change the IPs on the phones to register the extensions after they go offline? Phones are Yealink SIP T19P E2 and some Polycoms.