Which vty configuration restricts remote device administration to secure, encrypted access only?

The transport input ssh command explicitly configures the Virtual Teletype (VTY) lines to accept only Secure Shell (SSH) connections. SSH provides encryption for remote administration, fulfilling the requirement for secure, encrypted access. transport input all would allow both Telnet (insecure) and SSH, which doesn't restrict to encrypted access only. transport input telnet ssh also allows Telnet, failing to enforce encryption. transport input none would prevent any remote access to the VTY lines, making administration impossible. The login local command ensures that user authentication is performed against the local user database on the device.