IP Phone Resilience

Last Updated : Oct 01, 2024 |

Avaya IP phones registered with one system can automatically reregister with another system when resilience is required.

IP phone failover to an alternate gatekeeper is a feature of many IP phones. However, it requires the alternate gatekeeper to allow registration.

For an IP Office network:

  • During normal operation, the alternate gatekeeper blocks registration of phones already registered on another IP Office.

  • During failover the alternate gatekeeper allows registration of those phones.

Important:

  • IP phone resilience requires at least 1 physical phone (H323 or SIP). It will not operate using just softphone clients. The failover registration of IP phones is also the trigger for user, hunt group and voicemail resilience.

  • User changes to their settings during failover are lost after failback. In addition, the call history for calls during failover is lost after failback.

  • Failover disconnects calls handled by the IP Office system. Direct media calls may continue, see Call Resilience (Media Preservation).

  • Resilience fails if the failover server is restarted during failover. The backup user and registered phone settings received by the failover server during normal operation are held in its non-permanent memory. If during failover operation the server is rebooted, those records are lost.

  • Failover features require that the phones local to each system are still able to route data to the failover system.

  • When an IP phone fails over, the failover system allows it to operate as a "guest". The guest phones do not consume any licenses.

  • The features for user resilience are applied to the phone user. See User Resilience.

  • Hot desked users are automatically logged out. When their base extension fails back to the home system, the hot desked user is automatically logged in on that extension.

  • The failover server must be configured with matching settings for SIP and H.323 extension support. For example:

    • The IP Office systems must have an identity certificates signed by the same trusted root CA.

    • The SIP domain settings must match.

    • If supporting IPv6 extensions, the failover IP Office must also support IPv6.

Supported Telephones

Type

Supported phones

H.323

1600 Series, 9600 Series.

SIP

1120, B179[1], 1140, B199[1], 1220, H175, 1230, J100 Series, K100 Series.

SIP Softphones[2]

Avaya Workplace Clients

Others

All supported Avaya DECT R4 handsets. IP Office WebRTC SDK Clients[3]

  1. These Avaya SIP Phones require some manual configuration for resilience operation.

  2. Softphone resiliency requires physical IP desk phone resiliency to have occurred.

  3. Requires Avaya one-X® Portal for IP Office resilience to be configured.

When Does IP Phone Failover Occur?

If the home system is no longer visible to the failover system for at least 3 minutes, the failover system will allow IP phones to re-register with it. This requires at least one physical IP desk phone to trigger failover. Phones with existing calls using media connection preservation do not failover until that call ends.

The failover delay ensures that resilience is not invoked when it is not required, for example when the home system is simply being rebooted to complete configuration changes.

When Does IP Phone Failback Occur?

After the home system has been visible again for more than 10 minutes, any idle phones begin to re-register with the home system. If for some reason, a phone is unable to connect to the home system, there is a 5-minute grace period, where the phone can be logged in to either the home or failover system. This is called "homeless prevention".

Automatic failback to the home system is the default mode. For H323 IP phones, manual failback can be selected. In manual mode, the phone does not failback until either logged out or rebooted.

DHCP Resilience

When an IP Office provides extension data to the system that will back up the extensions it also provides DHCP data. The failover IP Office will provide DHCP service to the failover IP Phones - even if that system's DHCP is disabled. This operation relies on DHCP forwarding be allowed between networks or on the two servers being on the same subnet. A likely requirement is to have different SSONs for the two sets of phones.

Simultaneous Clients

If a user is in simultaneous mode on their home server when failover occurs, both their phones failover.

Limitations

  • Resilience fails if the failover server is restarted during failover. The backup user settings received by the failover server during normal operation are held in its non-permanent memory. If during failover operation the server is rebooted, those records are lost.

  • Internal twinning is not supported during resilience failover.

  • Fallback twinning is supported during failover. However, only after the phone has registered with the failover server.

Related information
Resilience Features