Which device needs to be configured to allow Cisco Unified Presence to receive phone availability updates from subscribed users?

An H.323 Trunk is used for H.323 voice call routing between systems and does not support the SIP-based presence subscription mechanism that CUP requires.

The Presence Gateway is a configuration object in CUCM that establishes a trusted relationship between CUCM and the Cisco Unified Presence server, enabling CUP to send SIP SUBSCRIBE requests and receive NOTIFY messages carrying phone state changes (on-hook/off-hook) for monitored users. Without this configuration, CUP has no authorized channel through which to receive real-time phone availability updates.

An MGCP Gateway is used to control PSTN media gateway devices and has no role in delivering presence or phone availability data to Cisco Unified Presence.

The SIP Cisco Unified Personal Communicator Gateway handles SIP signaling between the CUPC client and CUCM, and is not the device responsible for publishing phone availability updates to CUP.

A CTI Gateway interfaces with CTI-based applications for call control and monitoring, and is not configured as the source of phone availability updates for Cisco Unified Presence.