An administrator wants to add and configure an ephone-dn via the Cisco Unified Communications Manager Express web GUI. Which feature must be defined under telephony service configuration?

auto-reg-ephone enables automatic registration of IP phones but has no effect on whether directory numbers are editable through the web GUI.

auto-reg-dn is not a valid Cisco CME telephony-service command and does not control web-based DN editing.

max-ephones sets the maximum number of ephones that can register to CME but does not enable web-based DN configuration.

max-dn sets the maximum number of directory numbers supported but does not grant web GUI access to configure those DNs.

The dn-webedit command, configured under telephony-service, explicitly enables the web GUI interface to display and modify ephone-dn settings. Without this command, the directory number configuration options are not exposed in the CME web administration interface.