The answer is asymmetric routing without SSL decryption, which prevents the firewall from seeing the full TLS handshake. When a Palo Alto Networks firewall operates as a transparent bridge and lacks SSL decryption, it relies on the Server Name Indication (SNI) field and certificate exchange during the handshake to classify HTTPS traffic as 'ssl'. Asymmetric routing causes the firewall to see only one direction of the TCP handshake—such as the SYN or SYN-ACK—so it never observes the complete TLS negotiation. Without that full handshake, App-ID cannot extract the necessary signatures like TLS version or cipher suites, and it falls back to classifying the traffic as 'web-browsing' based solely on port 443. On the PCNSE exam, this tests your understanding of how App-ID behaves when decryption is off and routing is asymmetric; a common trap is assuming port-based classification is sufficient. Memory tip: no handshake, no SSL—asymmetric routing breaks the TLS conversation.
PCNSE Securing Traffic and App-ID Practice Question
This PCNSE practice question tests your understanding of securing traffic and app-id. 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.
During a security audit, it is discovered that some HTTP traffic is being incorrectly identified as 'web-browsing' instead of 'ssl' even though the traffic uses HTTPS. The firewall is positioned as a transparent bridge and no SSL decryption is configured. 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 is not seeing the full SSL handshake due to asymmetric routing.
When a firewall operates as a transparent bridge without SSL decryption, it relies on the Server Name Indication (SNI) field or the certificate exchange during the TLS handshake to identify HTTPS traffic as 'ssl'. Asymmetric routing causes the firewall to see only one direction of the TCP handshake (e.g., only the SYN or only the SYN-ACK), preventing it from observing the full TLS handshake. Without the complete handshake, App-ID cannot extract the necessary signatures (e.g., TLS version, cipher suites, certificate details) and falls back to classifying the traffic as 'web-browsing' based on port 443.
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.
✗
SSL decryption must be enabled for the firewall to correctly identify SSL traffic.
Why it's wrong here
SSL decryption is not required; App-ID can identify SSL traffic without decryption.
✓
The firewall is not seeing the full SSL handshake due to asymmetric routing.
Why this is correct
Asymmetric routing can prevent the firewall from seeing the SSL handshake, causing it to identify the traffic as HTTP.
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 default interzone rule is blocking the SSL identification packets.
Why it's wrong here
Interzone rules affect forwarding, not App-ID identification.
✗
The security policy allows 'web-browsing' before 'ssl' in the rule order.
Why it's wrong here
Rule order affects policy matching, not App-ID identification.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume SSL decryption is mandatory for SSL identification, but the firewall can identify HTTPS without decryption by inspecting the TLS handshake; the real issue is that asymmetric routing prevents the firewall from seeing the complete handshake, causing App-ID to fall back to port-based classification.
Detailed technical explanation
How to think about this question
App-ID uses multiple methods to identify SSL traffic: it inspects the TLS ClientHello for SNI, the ServerHello for the certificate, and the handshake completion. Asymmetric routing can cause the firewall to miss the ServerHello or Certificate messages, leading to an incomplete signature match. In real-world deployments, this often occurs in load-balanced environments where return traffic takes a different path, and the fix involves enabling 'asymmetric routing' support or using session distribution mechanisms like PBF (Policy Based Forwarding) to ensure symmetric flows.
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.
Securing Traffic and App-ID — This question tests Securing Traffic and App-ID — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The firewall is not seeing the full SSL handshake due to asymmetric routing. — When a firewall operates as a transparent bridge without SSL decryption, it relies on the Server Name Indication (SNI) field or the certificate exchange during the TLS handshake to identify HTTPS traffic as 'ssl'. Asymmetric routing causes the firewall to see only one direction of the TCP handshake (e.g., only the SYN or only the SYN-ACK), preventing it from observing the full TLS handshake. Without the complete handshake, App-ID cannot extract the necessary signatures (e.g., TLS version, cipher suites, certificate details) and falls back to classifying the traffic as 'web-browsing' based on port 443.
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.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Which THREE of the following can cause App-ID to incorrectly identify traffic?
hard
A.Multiple security rules are configured for the same traffic.
✓ B.Asymmetric routing causes the firewall to see only one direction of traffic.
✓ C.SSL decryption is not enabled for the traffic.
✓ D.IP fragmentation occurs before the firewall.
E.Traffic is forwarded through an HTTP proxy.
Why B: Asymmetric routing causes App-ID to see only one direction of traffic (e.g., SYN but no SYN-ACK). App-ID relies on bidirectional flow inspection to identify applications; without seeing both directions, the firewall cannot complete the application signature match or protocol handshake, leading to incorrect or failed identification.
Last reviewed: Jun 11, 2026
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This PCNSE practice question is part of Courseiva's free Palo Alto Networks certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCNSE exam.
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