Cisco CCNA 200-301 Practice Question

To require a password when accessing a Cisco router via Telnet, the administrator must set a password on the vty lines (virtual terminal lines used for Telnet and SSH connections) and enable the login command on those lines. This configuration prompts users for a password when they attempt to establish a Telnet session.

Setting an enable secret password secures access to privileged EXEC mode but does not affect Telnet access authentication. Creating a local user account with a password is not sufficient on its own; additional configuration is required to authenticate Telnet sessions using local usernames and passwords. Enabling the service password-encryption feature encrypts passwords in the configuration file but does not enforce password authentication for Telnet sessions.