What must be modified on the administration page in Cisco UCM when designing layered security?

Configuring private VLANs for phones is a network-level security measure, typically done on network switches, not directly modified on the Cisco UCM administration page for phone settings access control.

Modifying nonstandard TCP ports is generally configured on firewalls or applications, not a primary setting on the Cisco UCM administration page for securing phone access.

Phone auto-registration is a deployment feature for initial phone setup; managing it affects how phones join the system, but not directly how access to phone settings is secured after registration.

Restricting access to phone settings on the Cisco UCM administration page enhances security by preventing unauthorized users from altering device configurations, accessing personal information, or making fraudulent calls directly from the phone interface.