Snom phones support two failover methods:
Failover IdentityThe failover identity feature is a basic way to ensure the phone always has an operational line to make calls. When the Primary Identity goes down, the phone will only see this upon the next REGISTER attempt. The phone will consider the Identity as ‘unregistered’ and set the specified Failover Identity to the primary line for calls. Once the initial Identity is re-registered, the phone will switch back to that identity for calls. Since the Failover Identity feature is based on registration state, it is recommended that registration timers be set low to ensure this feature responds quickly in the event of a dropped identity.
Registration is fine on all accounts.
Primary registrar server goes down.
Calling a number via primary failes.
Phone has no idea about the failed server until next reregistration.
It marks the account as unregistered.
Calling a number via primary detects that the primary is down (regstate!) and set the failover identity as current identity. for the call.
Primary registrar goes up again.
Phone will route outgoing calls via secondary server until primary reregistration succeeds again.
You can configure the failover identity via the setting Failover Identity.
Failover/Load balancing via SRV/NAPTRSee Failover/Load balancing via SRV/NAPTR