Cisco Cisco E-Mail Manager Unity Integration Option Design Guide

When PG side A fails, PG side B becomes active.

PG side B registers all dialed numbers and phones, and call processing continues. Phones and 
gateways stay registered and operational with Unified CM subscriber A; they do not fail-over.

Agents with calls in progress will stay in progress, but with no third-party call control (conference, 
transfer, and so forth) available from their agent desktop softphones. Agents that were not on calls 
may notice their CTI desktop disable their agent state or third-party call control buttons on the 
desktop during the failover to the B-Side PG. Once the failover is complete, the agent desktop 
buttons are restored. However, the barge-in and conference calls will not be rebuilt properly, and 
calls will disappear from the desktop when either of the participants drops out of the call.

When PG side A recovers, PG side B remains active and uses the CTI Manager on Unified CM 
subscriber B.

 shows a failure on Unified CM subscriber A. The CTI Manager services are running on 

Unified CM subscribers C and D, and the CTI Manager on Unified CM subscriber C is actively 
connected to the Unified CM Peripheral Gateway (PG) side A. However, all phones and gateways are 
registered with Unified CM subscriber A. All phones and devices will re-home individually to the 
backup Unified CM subscriber B. If the device is in use (a phone on a call), it will re-home to backup 
Unified CM subscriber B after it is no longer in use.

The following conditions apply to this scenario:

All phones and gateways are registered with Unified CM subscriber A.

All phones and gateways are configured to re-home to Unified CM subscriber B (that is, B is the 
backup server).

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Unified CM B

Unified CM A

ICM synchronzation messages
Unified CM intra-cluster messages
JTAPI messages
H323 or MGCP messages
SCCP messages

Agent PG A

Fails

Agent PG B