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, 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 - will instead be set to point to the IP address of the registration server in our secondary data centre. 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, not via IP address (or you can use your own domain DNS C NAME record that points to 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