Cisco Unified Communications Manager Express Gateway Configuration

C.

The correct answer is C. voice register global.

Explanation:

Cisco Unified Communications Manager Express (CUCME) is a call-processing application that is part of Cisco's collaboration portfolio. CUCME enables small to medium-sized businesses to deploy voice, video, and other collaboration services on a single platform.

To configure a CUCME gateway to enable phones to register via SIP, the following steps are required:

1. Enter global configuration mode by typing "configure terminal" at the command prompt.
2. Enter the "voice service voip" command to begin configuring the gateway for voice services.
3. Enter the "voice register global" command to configure global parameters for Cisco Unified IP phones that will be connecting to the CUCME gateway via SIP. This command allows you to define things such as the domain name, the transport protocol (in this case, SIP), and the default registration and authentication settings for the phones.
4. Configure the phone's directory number (DN) by entering the "voice register dn" command. This command is used to assign a unique directory number to each phone that will be connecting to the CUCME gateway.
5. Finally, you can enable SIP connections on the gateway by entering the "allow-connections sip to sip" command. This command allows SIP calls to be routed through the gateway.

Therefore, option C (voice register global) is the top-level IOS command that is needed to begin the configuration of a Cisco Unified Communications Manager Express gateway to enable phones to be registered via SIP.