Enable Automatic Phone Reregistration in Cisco UCM

A.

Cisco Unified SRST provides Cisco Unified CM with fallback support for Cisco Unified IP phones that are attached to a Cisco router on your local network.

Cisco Unified SRST enables routers to provide call-handling support for Cisco Unified IP phones when they lose connection to remote primary, secondary, or tertiary Cisco Unified CM installations or when the WAN connection is down.

When configuring Cisco Unified Communications Manager (UCM), one of the critical considerations is ensuring high availability of the system. In the event that the connection between a phone and the subscriber server is lost, it is necessary to configure a mechanism to allow the phone to automatically re-register to the publisher server to maintain uninterrupted service. This is known as automatic failover, and it can be achieved using the Cisco UCM group configuration.

Option D: Cisco UCM Group

The Cisco UCM group is a logical entity that consists of one or more UCM servers, including a primary and one or more backup servers. The primary server is typically the publisher server, while the backup servers are the subscriber servers. The UCM group acts as a single entity that phones register to, and the group provides a load-balancing mechanism for call processing.

When a phone registers to the UCM group, it is configured with a primary server and a backup server. If the connection to the primary server is lost, the phone will automatically switch to the backup server to continue receiving service. When the primary server becomes available again, the phone will automatically re-register to the primary server.

Therefore, Option D: Cisco UCM Group enables phones to automatically re-register to a Cisco UCM publisher when the connection to the subscriber is lost. The other options listed, such as SRST, Route Group, and Device Pool, are all important configurations in UCM but are not directly related to enabling phones to automatically re-register to a UCM publisher.