Cisco CCNA (200-301)IP ServicesMedium
A network engineer is configuring a Cisco router to use SSH for secure remote access. After generating RSA keys and configuring local user accounts, the engineer tests the SSH connection but it fails. Upon checking the configuration, they find that the VTY lines are configured with 'transport input telnet'. Which command should replace 'transport input telnet' to enable SSH access on the VTY lines?
- Atransport input ssh
- Btransport input none
- Ctransport input console
- Dtransport input all
Show answer & explanationAnswer & explanation
Correct answer: D. transport input all
The 'transport input all' command on the VTY lines allows both Telnet and SSH connections, which is typically desired for flexibility during transition or for environments where both are still needed. If only SSH is desired, 'transport input ssh' would be used. Since the question implies enabling SSH without explicitly disabling Telnet, 'all' is a common and correct choice to ensure SSH works.
Why the other options are wrong
- A. This command explicitly allows only SSH, which would also work but 'all' is a more common initial step.
- B. This command disables all remote access, including SSH.
- C. This command is incorrect; 'console' is typically for the console port, not VTY lines.
Cisco VTY Transport Input
The 'transport input' command on Cisco VTY lines dictates which protocols (Telnet, SSH, or both) are permitted for remote access.
- Located under 'line vty' configuration mode.
- 'transport input telnet' allows only Telnet.
- 'transport input ssh' allows only SSH.
- 'transport input all' allows both Telnet and SSH.
- 'transport input none' disables all remote access.
Memory trick: Transport input: All means all, SSH for just SSH.