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Question

Difficulty: MediumRemote Access Technologies and Tools

A systems administrator needs to configure a network firewall to allow remote command-line administration of a headless Linux web server over an untrusted external network. The management session must ensure that login credentials and command outputs are fully encrypted in transit. Which of the following default protocol and port combinations should the administrator permit through the firewall?

  1. SSH over TCP port 22Answer
  2. B
    Telnet over TCP port 23
  3. C
    RDP over TCP port 3389
  4. D
    VNC over TCP port 5900

Answer

SSH over TCP port 22 is the correct choice because it provides secure, encrypted command-line access for remote administration over untrusted networks.
SSH (Secure Shell) operating on default TCP port 22 is designed specifically to establish secure, encrypted shell/command-line sessions over unsecure public networks, ensuring confidentiality of administrator credentials and transmitted data.

Step-by-Step Solution

1
Identify the remote management interface requirement.
The scenario specifies command-line (terminal) administration of a Linux server.
Choosing between command-line and graphical interface tools narrows down protocol candidates (SSH/Telnet vs RDP/VNC).
2
Evaluate security and encryption requirements.
The network connection passes through an untrusted external network, requiring end-to-end transport encryption.
Unencrypted protocols such as Telnet expose credentials to packet sniffing.
3
Select the correct protocol and default network port.
SSH encrypts all traffic and listens on TCP port 22 by default.
Permitting TCP port 22 on the firewall satisfies both the security encryption requirement and the command-line interface requirement.

Key Concept

SSH vs Telnet and default port assignments for secure remote command-line administration
Estimated Time:1m 0s
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Topics

Remote Access Technologies and Tools

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