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CAS-004 Practice Question: A security analyst observes that SSH connections…

Network Topology
0 0 ACCEPT alllo * 0.0.0.0/0100 540 DROP tcp50 3000 ACCEPT tcp20 1200 ACCEPT tcpRefer to the exhibit.```

A security analyst observes that SSH connections to the server are failing, but HTTP and HTTPS traffic works. Based on the exhibit, what is the most likely cause?

⚠ Common exam trap

Watch out — candidates often assume SSH is failing due to a service misconfiguration (Option D) or an overly restrictive allow rule (Option C), but the exhibit clearly shows a specific drop rule for port 22, which is the definitive cause.

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

The SSH service is being blocked by a firewall rule that drops TCP port 22 traffic.

The exhibit shows a firewall rule that explicitly drops TCP port 22 traffic, which is the default port for SSH. Since HTTP (port 80) and HTTPS (port 443) are unaffected, the issue is isolated to SSH. This rule is the most direct cause of the connection failures, as it blocks all SSH traffic regardless of source or destination.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

  • The HTTPS rule is overriding the SSH rule.

    Why it's wrong here

    Rules are independent; HTTPS does not affect SSH.

  • The SSH service is being blocked by a firewall rule that drops TCP port 22 traffic.

    Why this is correct

    The DROP rule for tcp dpt:22 is blocking SSH.

  • The SSH service is only allowed from the 10.0.0.0/8 subnet.

    Why it's wrong here

    The drop rule does not have a source restriction; it blocks all SSH.

  • The SSH service is misconfigured and not listening on the correct interface.

    Why it's wrong here

    No evidence of misconfiguration; firewall is the issue.

Visual reference

Client Server SYN (seq=100) SYN-ACK (seq=200, ack=101) ACK (ack=201) Connection established — data transfer begins

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JA

Written by Johnson Ajibi, MSc IT Security

Senior Network & Security Engineer · founder of Courseiva

This CAS-005 practice question is part of Courseiva's free CompTIA certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the CAS-005 exam.