The answer is that the firewall rule restricts the source port to 6514, but the syslog client uses a random ephemeral source port. This is the most likely cause because when a syslog-ng client sends logs over TCP or TLS, it dynamically selects an ephemeral port from the high range (typically above 1024) as its source, not a fixed port like 6514. The firewall on the central logging server at 10.0.0.10 is configured to only allow traffic with a source port of 6514, so the client’s packets are dropped before they reach the server. On the ISC2 Certified in Cybersecurity CC exam, this scenario tests your understanding of how firewalls filter traffic based on port numbers and the common misconfiguration of confusing a destination port with a source port. A frequent trap is assuming the client uses the same port as the server’s listening port. Remember the memory tip: “Clients are ephemeral, servers are fixed”—clients always use random high ports for outbound connections, while servers listen on well-known ports.
ISC2 CC Business Continuity, DR & Incident Response Practice Question
This CC practice question tests your understanding of business continuity, dr & incident response. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
The exhibit shows a syslog-ng client configuration and a firewall rule on the central logging server (IP 10.0.0.10). The client (192.168.1.100) is not sending logs to the server. 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 firewall rule restricts source port 6514, but the client uses a random ephemeral source port
The firewall rule on the central logging server (10.0.0.10) specifies a source port of 6514. However, syslog-ng clients, when sending over TCP or TLS, typically use a random ephemeral source port (e.g., above 1024) rather than a fixed source port. Since the firewall restricts the source port to exactly 6514, the client's packets are dropped, preventing logs from reaching the server.
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 syslog-ng configuration uses TLS, but the firewall rule does not allow TLS traffic
Why it's wrong here
TLS over TCP is still TCP; the firewall rule permits TCP, so TLS is allowed.
✓
The firewall rule restricts source port 6514, but the client uses a random ephemeral source port
Why this is correct
The rule includes 'eq 6514' which matches only if source port is 6514; clients use dynamic ports.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The syslog-ng client uses UDP by default, but the firewall allows only TCP
Why it's wrong here
The client configuration explicitly uses TCP transport (tls).
✗
The firewall rule does not include the client IP 192.168.1.100
Why it's wrong here
The rule includes the host 192.168.1.100 as the destination, which is correct for server receiving logs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume the firewall rule's source port 6514 is irrelevant or that the client must use the same port as the server, when in fact the client uses an ephemeral source port, making the rule overly restrictive and the cause of the failure.
Detailed technical explanation
How to think about this question
In syslog-ng, when using TCP or TLS transport, the client initiates a connection using a random ephemeral source port (typically in the range 49152–65535 per RFC 6335) and connects to the server's well-known destination port (e.g., 6514 for syslog-over-TLS). Firewall rules that specify a fixed source port (like 6514) are almost always incorrect because clients do not use that port as a source; this is a common misconfiguration in centralized logging setups where administrators mistakenly think the source port must match the destination port.
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 developer is choosing between AES-256 (symmetric) and RSA-2048 (asymmetric) for encrypting a large file that will be sent to a partner. Symmetric encryption is fast but requires key exchange; asymmetric is slower but solves the key distribution problem. A hybrid approach — encrypt the file with AES, encrypt the AES key with RSA — is standard. Questions like this test whether you understand when each approach applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this CC question in full detail.
Business Continuity, DR & Incident Response — This question tests Business Continuity, DR & Incident Response — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The firewall rule restricts source port 6514, but the client uses a random ephemeral source port — The firewall rule on the central logging server (10.0.0.10) specifies a source port of 6514. However, syslog-ng clients, when sending over TCP or TLS, typically use a random ephemeral source port (e.g., above 1024) rather than a fixed source port. Since the firewall restricts the source port to exactly 6514, the client's packets are dropped, preventing logs from reaching the server.
What should I do if I get this CC 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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