The SIP Trunk Plus service includes a built-in auto-failover feature which means that if the set of servers in our primary data centre cannot be reached / are not functional then a second set of servers in our secondary data centre will immediately come into automatic use. This is achieved by a making use of DYN's DNS re-routing service.
The DNS process is used each time an internet address is referenced: DNS transforms domain names into IP addresses by the use of 'name servers'. By default, sip.sip-trunking-services.com will point to the IP address of the registration server in our primary data centre but in the case of failover - be it automatic due to a service issue, or manual as a part of scheduled maintenance - sip.sip-trunking-services.com will instead be set to point to the IP address of the registration server in our secondary data centre. sip.sip-trunking-services.com is set to have a low (two minutes) 'time to live' (TTL) to facilitate this failover and make it as swift as is practically possible.
In order to make best use of our auto-failover feature you should ensure the following:
(a) you register your trunks via our DNS record sip.sip-trunking-services.com, not via IP address (or you can use your own domain DNS C NAME record that points to sip.sip-trunking-services.com if preferred) - please refer to DNS Record Settings
(b) you set your trunk to have a low re-registration time - please refer to Registration Timeout Settings
(c) all good internet service providers should dynamically update their DNS records but some may not; if you do not know if your ISP caches DNS records or not we recommend that you use DNS name servers that are known to refresh quickly / dynamically, not by caching records - please refer to Recommended DNS / Name Servers
(d) your routers/firewall/gateway devices have been set up to accept all required IP addresses - please refer to What Is SIP Trunk Plus' Domain/Realm, IP Address(es)?
(e) ensure that DNS caches are set to be dynamic / refreshed quickly within your router / firewall / gateway devices