Which component is needed to facilitate the connection between Cisco Unified Communications Manager and Cisco Unified Presence Server?

CUCM and Cisco Unified Presence Server (CUPS) communicate over a SIP trunk, which carries SIP SUBSCRIBE and NOTIFY messages used for presence state exchange. Without this SIP trunk, the two servers cannot share user availability information, and features like presence-enabled contacts in Cisco Unified Personal Communicator will not function.

H.323 gateways connect CUCM to PSTN or legacy PBX systems using the H.323 protocol and are not used for server-to-server presence integration.

A Gatekeeper provides H.323 call routing, address resolution, and bandwidth control functions, which are unrelated to the CUCM-CUPS integration.

MGCP gateways are used to control analog or digital telephony endpoints such as FXS/FXO ports, not to integrate presence servers.

Cisco Unified Border Element (CUBE) is a session border controller for inter-enterprise SIP calls and is not required for internal CUCM-to-CUPS connectivity.