The answer is that the decryption rule is configured with the forward proxy method instead of the required SSL Inbound Inspection method. Inbound SSL decryption for a customer-facing web application demands the inbound inspection method because the firewall must use the server’s private key to decrypt the traffic without re-encrypting with its own certificate. When forward proxy is mistakenly applied, the firewall attempts to generate a new certificate on the fly, which causes a certificate mismatch with the server’s wildcard certificate, triggering the ‘secure connection’ error. On the PCNSA exam, this scenario tests your understanding of the critical distinction between outbound and inbound decryption methods—a common trap is assuming forward proxy works for all decryption rules. Remember the memory tip: “Inbound needs the key, outbound fakes the key.” For inbound inspection, you import the server’s private key; for forward proxy, the firewall generates its own.
PCNSA Decryption and Monitoring Practice Question
This PCNSA practice question tests your understanding of decryption and monitoring. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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 financial services firm deploys inbound SSL decryption to inspect all HTTPS traffic to their customer-facing web application. After enabling decryption, customers report that they are unable to connect to the web app and receive 'This site can’t provide a secure connection' errors. The firewall logs show no decryption errors, and traffic logs show the sessions are matched to the decryption rule but no decryption action is taken. The web app uses a wildcard certificate (*.example.com). The firewall's decryption certificate is imported from the server's private key. 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 decryption rule is configured with the forward proxy method.
Option D is correct because inbound SSL decryption requires the 'SSL Inbound Inspection' method, not the forward proxy method. Forward proxy is used for outbound decryption where the firewall generates a certificate on the fly. For inbound decryption, the firewall must use the server's private key to decrypt traffic, which is configured via an SSL Inbound Inspection rule. Since the rule is set to forward proxy, the firewall attempts to re-encrypt with its own certificate, causing a certificate mismatch and the 'secure connection' error.
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 firewall does not support wildcard certificates for inbound decryption.
Why it's wrong here
Palo Alto firewalls support wildcard certificates for SSL Inbound Inspection.
✗
The web server is not properly configured to handle decrypted traffic.
Why it's wrong here
The error occurs at the client side before the server is contacted, so server configuration is not the cause.
✗
The decryption profile is set to 'Block sessions with untrusted certificates'.
Why it's wrong here
If blocking were enabled, the logs would show a decryption action and error, but no decryption action is logged.
✓
The decryption rule is configured with the forward proxy method.
Why this is correct
Inbound decryption must use 'SSL Inbound Inspection'; forward proxy is for outbound and mismatches cause handshake failures.
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 confuse the forward proxy method (used for outbound decryption) with the SSL Inbound Inspection method (required for inbound decryption), assuming any decryption rule will work for inbound traffic as long as a certificate is imported.
Trap categories for this question
Command / output trap
If blocking were enabled, the logs would show a decryption action and error, but no decryption action is logged.
Detailed technical explanation
How to think about this question
In inbound SSL decryption, the firewall must be configured with an 'SSL Inbound Inspection' decryption rule that uses the server's private key to decrypt incoming traffic. The forward proxy method is designed for outbound scenarios where the firewall acts as a proxy for clients; using it for inbound traffic causes the firewall to present its own certificate to the client, which does not match the server's wildcard certificate, triggering browser warnings. The logs show 'no decryption action' because the rule is matched but the action (forward proxy) is inappropriate for inbound traffic, so the firewall passes the traffic without decrypting it, yet the client still sees a certificate error due to the proxy's certificate.
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 practitioner preparing for the PCNSA exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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: The decryption rule is configured with the forward proxy method. — Option D is correct because inbound SSL decryption requires the 'SSL Inbound Inspection' method, not the forward proxy method. Forward proxy is used for outbound decryption where the firewall generates a certificate on the fly. For inbound decryption, the firewall must use the server's private key to decrypt traffic, which is configured via an SSL Inbound Inspection rule. Since the rule is set to forward proxy, the firewall attempts to re-encrypt with its own certificate, causing a certificate mismatch and the 'secure connection' error.
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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