Which requirement is mandatory to allow an MGCP gateway to download its configuration from the Cisco Unified Communications Manager cluster?

The 'ccm-manager redundant host' command configures a secondary CUCM fallback address for redundancy and is optional, not required for initial configuration download.

A domain name on the gateway is not required for TFTP-based configuration retrieval - the gateway can reference the TFTP server by IP address.

A T1 interface is a physical telephony hardware port used for PSTN connectivity and has no role in the MGCP configuration download process.

When an MGCP gateway boots or resets, it contacts the Cisco Unified Communications Manager TFTP service to retrieve its configuration file containing endpoint definitions and dial plan information. Without a Cisco TFTP server running and reachable on the network, the gateway has no mechanism to obtain this configuration and cannot register its endpoints with CUCM.