Key Configuration Requirement for Hybrid Message Service High Availability Deployment with Multiple IM and Presence Clusters

A.

In a Hybrid Message Service deployment with multiple IM and Presence clusters, High Availability (HA) is a critical requirement. This ensures that in the event of a failure in one cluster, the services can still be provided from another cluster. To achieve this, there are several key configuration requirements:

1. Intercluster Sync Agent: This is a service that synchronizes configuration data between multiple IM and Presence clusters. It is important to have this service working across all IM and Presence clusters to ensure that the configuration data is consistent and up-to-date in all clusters.

2. Intercluster Lookup Service: This is a service that provides routing information for messages between different clusters. It is important to have this service working across all IM and Presence clusters to ensure that messages can be properly routed between clusters.

3. Multiple Device Messaging: This feature allows a user to receive messages on multiple devices simultaneously. However, in a HA deployment with multiple clusters, it is recommended to disable this feature to avoid message duplication and ensure that messages are properly routed to a single device.

4. AXL Service: This is a service that allows external applications to communicate with the Cisco Unified Communications Manager (CUCM). It is important to activate this service only on the publisher of each IM and Presence cluster to avoid conflicts between multiple AXL connections.

Out of these key configuration requirements, the most relevant one to the question is the requirement for the Intercluster Sync Agent to be working across all IM and Presence clusters. Therefore, option A is the correct answer.