The answer is that an explicit firewall rule dropping TCP port 22 traffic is the most likely cause of the SSH connection failures. This is correct because SSH operates by default on TCP port 22, and the firewall rule shown in the exhibit directly blocks that port while leaving HTTP (port 80) and HTTPS (port 443) unaffected, isolating the issue to SSH traffic. On the CompTIA SecurityX CAS-005 exam, this scenario tests your ability to correlate service-specific failures with firewall ACLs, a common troubleshooting trap where candidates overlook that a deny rule for a single port can coexist with permissive rules for other services. Remember that SSH failures with working web traffic almost always point to a port 22 block—think of it as the “22 hurdle” where HTTP and HTTPS clear the firewall, but SSH gets dropped.
CAS-004 Security Architecture Practice Question
This CAS-004 practice question tests your understanding of security architecture. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Network Topology
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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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 clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may 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.
Detailed technical explanation
How to think about this question
Firewall rules are typically processed in a top-down order, with an implicit deny at the end. A 'drop' rule for TCP port 22 will silently discard packets, causing SSH clients to time out rather than receive a reset (RST). In contrast, a 'reject' rule would send an ICMP unreachable or TCP RST, which would give a faster failure response. Understanding the difference between drop and reject is critical for troubleshooting connectivity issues in security architectures.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Security Architecture — This question tests Security Architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: 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.
What should I do if I get this CAS-004 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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