Overview

High Availability (HA) creates a secondary SIP account that handles calls when the primary account is unavailable. HA is a paid add-on to the SIP Trunk subscription.

HA Modes

Modes are available : 

• High Availability
• High Availability 2T
• High Availability 4T
• High Availability 2T and 4T 

High Availability (There is tab High Availability): 

High availability enables your system to operate continuously without interruption for a designated period of time and ensures that it meets an agreed-upon level of operational performance.

There are 3 modes:

• Only Primary: all calls use the Primary SIP account.
• Load Balacancing
• Auto Fail-over

Mode 1: Only Primary (Default)

• All calls use the Primary SIP account. The secondary account exists but receives no traffic.

Mode 2: Load Balancing

• Distributes calls between the Primary and Secondary SIP accounts in round-robin order.

Behaviour:

• Distributes incoming call traffic in round-robin between both SIP accounts.
• Does not check whether either SIP account is registered — routes regardless of status. No automatic retry if a call fails.
• Primary and Secondary accounts share the same concurrent call pool.
• Outbound caller ID follows the Primary account's settings.

Mode 3: Auto Failover

Routes calls to the Secondary SIP account when a specific failure condition is detected on the Primary. The system evaluates each call outcome to determine whether failover should be triggered.

Failover trigger rule: Failover is only triggered for far-end failure conditions — specific SIP response errors and connection failures from the remote end. Client-side issues and authentication errors do not trigger failover.

Conditions that trigger failover (Failover = TRUE)

Conditions that do NOT trigger failover (Failover = FALSE)

Both accounts share the same concurrent call pool. Total simultaneous calls cannot exceed the allocated limit on the Primary account.

Secondary SIP Account Configuration

Configure the secondary account under Configuration → Secondary Region tab:

SIP Label

Authentication Mode

IP Address List

Advanced HA — 2T and 4T

Advanced HA extends redundancy across multiple availability zones and regions.

Configuration	Architecture	Behaviour
HA 2T	1 region, 2 zones	Round-robin between 2 zones within the same region. If one zone fails, all traffic moves to the other.
HA 4T	2 regions, 1 zone each	All calls go to the primary region. Fails over to the secondary region when the primary region is down.
HA 2T + 4T	2 regions, 2 zones each	Within a region: fail over between zones. If both zones in a region fail: fail over to the other region.