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.
A large enterprise uses a custom application that communicates over TCP port 8080 using HTTP. The application traffic is correctly identified as 'custom-app' by App-ID. Recently, the development team changed the application to use HTTPS on the same port. The firewall administrator updated the security policy to allow the application, using the same application name, but now the traffic is being denied. The firewall logs show the application as 'ssl' and the action 'deny'. The security policy has a rule that allows 'custom-app' from inside to outside. What should the administrator do to resolve this issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Update the custom application definition to include SSL decryption and a hostname match.
Option B is correct because the custom application definition was designed for HTTP, not HTTPS. To identify the new HTTPS traffic as the custom application, the administrator must update the definition to include SSL decryption and a hostname match, so that App-ID correctly recognizes the encrypted traffic. Option A is wrong because an override would bypass App-ID, losing visibility. Option C is wrong because allowing all SSL traffic is too broad a security risk. Option D is wrong because disabling App-ID is not a best practice and reduces security.
Key principle: ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
Create an application override for the traffic on port 8080.
Why it's wrong here
This bypasses App-ID and does not leverage application identification.
✗
Disable App-ID for that traffic and use a port-based policy.
Why it's wrong here
This removes application visibility and is not recommended.
✗
Change the security policy rule to allow application 'ssl' instead.
Why it's wrong here
This would allow all SSL traffic, not just the custom application, creating a security risk.
✓
Update the custom application definition to include SSL decryption and a hostname match.
Why this is correct
This enables the firewall to decrypt and identify the HTTPS traffic as the custom application.
Related concept
Standard ACLs match source addresses.
Common exam traps
Common exam trap: ACLs stop at the first match
ACLs are processed top to bottom. The first matching entry wins, and an implicit deny usually exists at the end.
Detailed technical explanation
How to think about this question
ACL questions test precision: source, destination, protocol, port and direction. A generally correct ACL can still fail if it is applied on the wrong interface or in the wrong direction.
KKey Concepts to Remember
Standard ACLs match source addresses.
Extended ACLs can match source, destination, protocol and ports.
The first matching ACL entry is used.
There is usually an implicit deny at the end.
TExam Day Tips
→Check inbound versus outbound direction.
→Read the ACL from top to bottom.
→Look for a broader permit or deny above the intended line.
Key takeaway
ACLs process entries top to bottom and stop at the first match. Entry order and interface direction matter as much as the permit or deny statement.
Real-world example
How this comes up in practice
A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.
What to study next
Got this wrong? Here's your next step.
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PCNSE ACL questions on filtering logic and placement.
Securing Traffic and App-ID — This question tests Securing Traffic and App-ID — Standard ACLs match source addresses..
What is the correct answer to this question?
The correct answer is: Update the custom application definition to include SSL decryption and a hostname match. — Option B is correct because the custom application definition was designed for HTTP, not HTTPS. To identify the new HTTPS traffic as the custom application, the administrator must update the definition to include SSL decryption and a hostname match, so that App-ID correctly recognizes the encrypted traffic. Option A is wrong because an override would bypass App-ID, losing visibility. Option C is wrong because allowing all SSL traffic is too broad a security risk. Option D is wrong because disabling App-ID is not a best practice and reduces security.
What should I do if I get this PCNSE question wrong?
Review ACL processing order, placement rules (standard near destination, extended near source), and inbound vs outbound direction. Study wildcard masks and implicit deny. Then practise related PCNSE ACL questions on filtering logic and placement.
What is the key concept behind this question?
Standard ACLs match source addresses.
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Question Discussion
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