PCNSE Deploy and Configure Firewalls Practice Question
This PCNSE practice question tests your understanding of deploy and configure firewalls. 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.
Exhibit
set shared decryption rule MyRule from trust to untrust source 10.1.1.0/24 destination any application ssl decryption forward-proxy
Refer to the exhibit. An administrator has configured this decryption policy but users in the 10.1.1.0/24 subnet receive certificate warnings when accessing HTTPS sites. 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 certificate is not trusted by clients
Option D is correct because certificate warnings occur when the decryption certificate used by the firewall is not trusted by the client machines. In a forward proxy decryption scenario, the firewall generates a new certificate on-the-fly for each HTTPS session, and if that certificate is not installed in the client's trusted root store, the browser will display a security warning. This is the most common cause of certificate warnings in decryption deployments.
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 rule should be at the top of the rulebase
Why it's wrong here
Rule order may affect matching but would not cause certificate warnings.
✗
The destination address should be specific
Why it's wrong here
Destination 'any' is valid and does not affect certificate warnings.
✗
The application should be web-browsing
Why it's wrong here
SSL is the correct application for HTTPS; web-browsing is for HTTP.
✓
The decryption certificate is not trusted by clients
Why this is correct
Clients must trust the firewall's CA certificate for seamless decryption; otherwise, certificate warnings appear.
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
Palo Alto Networks often tests the distinction between rule configuration issues (like order or application matching) and certificate trust issues, leading candidates to focus on policy settings rather than the fundamental requirement that clients must trust the decryption CA.
Detailed technical explanation
How to think about this question
When a Palo Alto Networks firewall performs SSL forward proxy decryption, it intercepts the client's ClientHello and generates a new certificate signed by the firewall's CA certificate. The client must have the firewall's CA certificate installed in its Trusted Root Certification Authorities store; otherwise, the browser cannot validate the certificate chain, resulting in a warning. This is distinct from inbound inspection (SSL Inbound Inspection) where the firewall uses the server's actual 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 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.
Deploy and Configure Firewalls — This question tests Deploy and Configure Firewalls — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The decryption certificate is not trusted by clients — Option D is correct because certificate warnings occur when the decryption certificate used by the firewall is not trusted by the client machines. In a forward proxy decryption scenario, the firewall generates a new certificate on-the-fly for each HTTPS session, and if that certificate is not installed in the client's trusted root store, the browser will display a security warning. This is the most common cause of certificate warnings in decryption deployments.
What should I do if I get this PCNSE 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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