The answer is to create a security policy rule that allows traffic from the internal zone to the external zone. This is correct because in a Layer 3 deployment with virtual wire subinterfaces, the firewall still relies on security policy rules as the primary mechanism for traffic inspection, regardless of the interface type. Even though virtual wire subinterfaces operate transparently at Layer 2, when deployed in Layer 3 mode, the firewall must enforce zone-based policies to inspect and control traffic between the internal and external zones. On the PCNSA exam, this question tests your understanding that security policies, not interface configuration alone, govern traffic inspection—a common trap is assuming virtual wire subinterfaces bypass policy enforcement. Remember the memory tip: "Virtual wire, real policy"—the subinterface type does not change the need for a zone-to-zone rule to enable inspection.
PCNSA Device Management and Services Practice Question
This PCNSA practice question tests your understanding of device management and services. 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.
A security engineer needs to ensure that all traffic from the internal network to the internet is inspected by the firewall. The firewall is deployed in layer 3 mode with virtual wire subinterfaces. Which configuration is required to achieve this?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create a security policy rule that allows traffic from the internal zone to the external zone
Option A is correct because in a Layer 3 firewall deployment with virtual wire subinterfaces, traffic inspection is governed by security policy rules. A rule allowing traffic from the internal zone to the external zone ensures that all outbound traffic is evaluated and inspected by the firewall, as security policies are the primary mechanism for controlling and logging traffic in Palo Alto Networks firewalls.
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.
✓
Create a security policy rule that allows traffic from the internal zone to the external zone
Why this is correct
Security policies enforce inspection and control.
Related concept
Read the scenario before looking for a memorised answer.
✗
Define a NAT policy to translate internal IPs to the external interface
Why it's wrong here
NAT does not enable inspection; it translates addresses.
✗
Enable SSL decryption on the firewall
Why it's wrong here
Decryption is for encrypted traffic, not a requirement for general inspection.
✗
Configure a virtual wire between the internal and external interfaces
Why it's wrong here
Virtual wire is for transparent mode, not layer 3.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse NAT or decryption as the primary mechanism for traffic inspection, but in Palo Alto Networks firewalls, security policies are the fundamental control that enables inspection and logging of traffic.
Detailed technical explanation
How to think about this question
In Palo Alto Networks firewalls, security policies are evaluated in order, and traffic must match a security rule to be inspected and allowed or denied. Virtual wire subinterfaces allow multiple VLANs to be carried over a single physical interface in Layer 3 mode, enabling inter-VLAN routing and policy enforcement. Without a security policy rule that permits traffic from the internal zone to the external zone, all traffic would be denied by default, even if NAT or decryption is configured.
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.
Device Management and Services — This question tests Device Management and Services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a security policy rule that allows traffic from the internal zone to the external zone — Option A is correct because in a Layer 3 firewall deployment with virtual wire subinterfaces, traffic inspection is governed by security policy rules. A rule allowing traffic from the internal zone to the external zone ensures that all outbound traffic is evaluated and inspected by the firewall, as security policies are the primary mechanism for controlling and logging traffic in Palo Alto Networks firewalls.
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.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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This PCNSA 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 PCNSA exam.
Question Discussion
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