When configuring Cisco Unified Communications Manager, which configuration enables phones to automatically register to a Cisco Unified Communications publisher when the connection to the subscriber…

A Cisco Unified CM Group defines a prioritized list of Cisco Unified Communications Manager servers (e.g., Publisher, Subscriber A, Subscriber B). When a phone loses its connection to its primary registered server (often a subscriber), it automatically attempts to register with the next available server in its assigned Cisco Unified CM Group, which could be the publisher, providing redundancy and ensuring service continuity.

A Device Pool groups devices and applies common configurations like regions, locales, and Cisco Unified CM Groups, but the Device Pool itself does not define the failover sequence for registration; it merely assigns a CM Group.

SRST (Survivable Remote Site Telephony) provides call processing redundancy for phones at remote sites when the WAN link to the central CUCM is lost, allowing them to register to a local gateway for basic call services, but it is not for registration failover between CUCM servers within the same cluster.

A Route Group defines a prioritized list of gateways or trunks for outbound call routing, not for phone registration failover.