- A
Confirm that the VoIP protocol is supported by App-ID.
Why wrong: The log shows it is identified, so App-ID supports it.
- B
Ensure that the security rule action is set to 'allow' and not 'deny'.
Why wrong: The logs indicate the rule allows 'voip', so this is not the issue.
- C
Verify that the application override is not set for this traffic.
Why wrong: Application override would force a different identification, but the log already shows identification as 'voip'.
- D
Check if a vulnerability protection profile is dropping the traffic based on a threat signature.
Correct: Security profiles can drop traffic even if the security rule allows the application.
Question 265 of 516
Why Is VoIP Traffic Dropped Even Though the Security Rule Allows It?
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 network security engineer is troubleshooting an issue where certain VoIP traffic is being dropped by the firewall. The traffic logs show that the application is identified as 'voip' and the security rule allows 'voip'. However, the traffic is still being dropped. What should the engineer check next?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Check if a vulnerability protection profile is dropping the traffic based on a threat signature.
Option D is correct because even when App-ID correctly identifies the traffic as 'voip' and a security rule allows it, a vulnerability protection profile applied to the rule can still drop the traffic if it matches a threat signature. This is a common scenario where the firewall's threat prevention engine, not the security rule, is responsible for the drop. The engineer should inspect the threat logs for any matching signatures.
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.
- ✗
Confirm that the VoIP protocol is supported by App-ID.
Why it's wrong here
The log shows it is identified, so App-ID supports it.
- ✗
Ensure that the security rule action is set to 'allow' and not 'deny'.
Why it's wrong here
The logs indicate the rule allows 'voip', so this is not the issue.
- ✗
Verify that the application override is not set for this traffic.
Why it's wrong here
Application override would force a different identification, but the log already shows identification as 'voip'.
- ✓
Check if a vulnerability protection profile is dropping the traffic based on a threat signature.
Why this is correct
Correct: Security profiles can drop traffic even if the security rule allows the application.
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 assume a security rule 'allow' action guarantees traffic passage, overlooking that threat prevention profiles (vulnerability, anti-spyware, etc.) can independently drop traffic after the rule is matched.
Trap categories for this question
Command / output trap
The log shows it is identified, so App-ID supports it.
Detailed technical explanation
How to think about this question
Under the hood, Palo Alto Networks firewalls process traffic through a multi-stage pipeline: first, App-ID identifies the application, then the security rule is evaluated, and finally, threat prevention profiles (such as vulnerability protection) inspect the traffic for exploits. Even if the security rule allows the traffic, a vulnerability protection profile with a signature matching a known VoIP exploit (e.g., SIP buffer overflow) will drop the packet and log it under the Threat log, not the Traffic log. In real-world scenarios, this often occurs with SIP or H.323 traffic where a signature for a CVE triggers a drop, requiring the engineer to create a vulnerability protection exception.
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 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.
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FAQ
Questions learners often ask
What does this PCNSE question test?
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: Check if a vulnerability protection profile is dropping the traffic based on a threat signature. — Option D is correct because even when App-ID correctly identifies the traffic as 'voip' and a security rule allows it, a vulnerability protection profile applied to the rule can still drop the traffic if it matches a threat signature. This is a common scenario where the firewall's threat prevention engine, not the security rule, is responsible for the drop. The engineer should inspect the threat logs for any matching signatures.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jul 4, 2026
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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