This PCNSA practice question tests your understanding of decryption and monitoring. 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.
A network administrator notices that some HTTPS sessions are not being decrypted by the firewall, even though the decryption policy rule is configured to decrypt traffic from a specific subnet. The firewall is in forward proxy mode. All other decryption rules work. 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
✓
A no-decrypt rule higher in the policy list matches the traffic before the decrypt rule.
In a forward proxy deployment, the firewall evaluates decryption policy rules in order from top to bottom. If a no-decrypt rule is placed higher in the policy list than the decrypt rule for the specific subnet, traffic matching that no-decrypt rule will bypass decryption entirely. This is the most likely cause because all other decryption rules work, indicating the decryption configuration itself is functional, but the order of rule evaluation prevents the intended rule from being applied.
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 traffic is using TLS 1.3 which is not supported by the firewall.
Why it's wrong here
Palo Alto firewalls support TLS 1.3 since PAN-OS 9.0; older versions may not, but this is less likely.
✗
The firewall's encryption algorithm settings do not match the server's cipher suite.
Why it's wrong here
Cipher mismatch causes decryption failure, not a lack of decryption action.
✗
The SSL/TLS decryption profile has 'Block sessions with expired certificates' enabled.
Why it's wrong here
This setting blocks sessions, but does not cause them to skip decryption; they would still be evaluated.
✓
A no-decrypt rule higher in the policy list matches the traffic before the decrypt rule.
Why this is correct
Decryption policy rules are evaluated top-down; a preceding no-decrypt rule would prevent decryption.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume the issue is with TLS version support or certificate validation, overlooking the fundamental rule-ordering logic in decryption policy that can cause a no-decrypt rule to preempt a decrypt rule.
Detailed technical explanation
How to think about this question
Palo Alto Networks firewalls process decryption policy rules in sequential order, similar to security policy rules. A no-decrypt rule (action set to 'no-decrypt') at a higher priority will match traffic based on source, destination, and service criteria, and the firewall will forward that traffic without attempting SSL/TLS interception. This is a common misconfiguration when administrators add a broad no-decrypt rule for trusted domains or internal resources without considering its placement relative to more specific decrypt rules.
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 network engineer segments a warehouse floor into three subnets: 20 scanners, 5 printers, and 2 management hosts. Picking the wrong mask wastes addresses or leaves too few usable hosts. Exam questions test whether you can apply CIDR notation, calculate block size, and identify the correct usable-host range for a given prefix.
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.
Decryption and Monitoring — This question tests Decryption and Monitoring — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: A no-decrypt rule higher in the policy list matches the traffic before the decrypt rule. — In a forward proxy deployment, the firewall evaluates decryption policy rules in order from top to bottom. If a no-decrypt rule is placed higher in the policy list than the decrypt rule for the specific subnet, traffic matching that no-decrypt rule will bypass decryption entirely. This is the most likely cause because all other decryption rules work, indicating the decryption configuration itself is functional, but the order of rule evaluation prevents the intended rule from being applied.
What should I do if I get this PCNSA 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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