Console and VTY

4.1 Troubleshoot device management

📘CCNP Enterprise – ENARSI (300-410)

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Device management is about how you access and control a network device, like a router or switch, so you can configure it, monitor it, and troubleshoot issues. Cisco devices can be accessed through console ports or VTY (Virtual Teletype) lines. Understanding how these work and troubleshooting them is crucial for the exam.

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4.1.a Console Access

What is Console Access?

• Console port is a physical port on the device (usually RJ-45 or USB) that allows direct local access.
• It’s used when the network connection isn’t working, or initial configuration is needed.
• You connect to it using a console cable and terminal software (like PuTTY, Tera Term, or SecureCRT).

Key Points for Troubleshooting Console Access

1. Cable Type:
   • Use the correct cable: RJ-45 to DB9 console cable (older devices) or USB console cable (newer devices).
   • Wrong cable → you won’t get access.
2. Terminal Settings:
   • Typical terminal settings:
     • Baud rate: 9600 bps (default)
     • Data bits: 8
     • Parity: None
     • Stop bits: 1
     • Flow control: None
   • Mismatched settings → garbled output or no output.
3. Device Not Responding:
   • Check the cable connection.
   • Ensure the terminal program is running correctly.
   • Ensure the device is powered on.

Example Commands for Console

• Console is mainly used for local login, so you’ll see prompts like: Router> Router#
• If the device is new or reset, you might need to enter setup mode.

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4.1.a VTY Access

What is VTY Access?

• VTY (Virtual Teletype) lines allow remote access over the network using protocols like:
  • Telnet (insecure, sends data in clear text)
  • SSH (secure, encrypted)
• VTY lines are logical ports, not physical.
• Typically, Cisco devices have 5 VTY lines by default (0–4), meaning up to 5 simultaneous remote sessions.

Key Points for Troubleshooting VTY Access

1. VTY Configuration:
   • Check VTY lines using: show running-config line vty 0 4 login local transport input ssh
   • Make sure transport input includes the protocol you want (Telnet/SSH).
     Example: If you try SSH but it’s set to transport input telnet, connection fails.
2. User Authentication:
   • VTY lines require authentication:
     • Local username/password: username admin privilege 15 secret cisco123
     • Or RADIUS/TACACS+ for centralized authentication.
3. Network Issues:
   • Ensure the device has an IP address on a reachable interface.
   • Check ACLs that may block remote access.
4. SSH Troubleshooting:
   • SSH requires:
     • A hostname and domain-name configured.
     • A crypto key generated: crypto key generate rsa
     • Correct username/password.

Example Commands for VTY

• Check active sessions: show users
• Check line settings: show line
• Test connectivity: ping <device-ip>

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Differences Between Console and VTY (Exam Focus)

Feature	Console	VTY (Telnet/SSH)
Access Type	Physical, local	Remote, logical
Usage	Initial setup, emergency access	Remote configuration
Security	Physical access required	Password, SSH for encryption
Max Connections	1	Usually 5 (0–4)

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Common Exam Troubleshooting Scenarios

1. Cannot access device via console:
   • Check cable type and connection.
   • Verify terminal settings.
   • Ensure device is powered on.
2. Cannot access device via SSH:
   • Check IP connectivity.
   • Verify username/password.
   • Confirm SSH is enabled (crypto key, transport input ssh).
3. Telnet fails:
   • Check if transport input telnet is allowed.
   • Verify network connectivity and ACLs.
4. VTY sessions are maxed out:
   • Only 5 sessions allowed by default. You may need to increase VTY lines: line vty 0 15

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Exam Tips

• Remember: Console is local, VTY is remote. Many exam questions test this concept.
• Know the basic troubleshooting commands: show running-config, show line, show users, ping.
• Always check authentication method and transport protocols first when remote access fails.