PCNSE Deploy and Configure Firewalls Practice Question
This PCNSE practice question tests your understanding of deploy and configure firewalls. 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 firewall is configured with multiple virtual wire interfaces. Traffic passes through but the firewall cannot enforce security policies based on source/destination IP addresses. What is the reason?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Virtual wire mode does not support IP-based policies
In virtual wire mode, the firewall operates as a transparent Layer 2 bridge, forwarding frames based on MAC addresses without performing any IP routing or inspection of Layer 3 headers. Because the firewall does not see the source or destination IP addresses in the traffic, it cannot enforce security policies that rely on IP-based criteria. Option D correctly identifies that virtual wire mode inherently does not support IP-based policies.
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 virtual wire is not configured with zones
Why it's wrong here
Zones are required but even with zones, IP-based policies are not available in virtual wire mode.
✗
The virtual wire requires a VLAN tag
Why it's wrong here
VLAN tagging is optional and does not enable IP-based policies.
✗
The security policy is in layer 3 mode
Why it's wrong here
Layer 3 mode is for routed interfaces; virtual wire is Layer 2.
✓
Virtual wire mode does not support IP-based policies
Why this is correct
In virtual wire mode, the firewall acts as a transparent bridge and cannot inspect IP addresses for policy matching.
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 may assume virtual wire mode still allows IP-based policies because the firewall can see IP packets, but they forget that the firewall does not process Layer 3 headers in this mode, making IP-based policy enforcement impossible.
Detailed technical explanation
How to think about this question
Virtual wire mode leverages a pair of interfaces that are logically bonded together, acting as a wire between two network segments. The firewall inspects only Layer 2 headers and can apply policies based on MAC addresses, VLAN tags, or application signatures (via App-ID), but it never performs IP routing or NAT. In real-world deployments, virtual wire is often used for inline traffic inspection without changing the IP topology, such as in data center leaf-spine architectures or when inserting a firewall into an existing Layer 2 network.
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 help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
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: Virtual wire mode does not support IP-based policies — In virtual wire mode, the firewall operates as a transparent Layer 2 bridge, forwarding frames based on MAC addresses without performing any IP routing or inspection of Layer 3 headers. Because the firewall does not see the source or destination IP addresses in the traffic, it cannot enforce security policies that rely on IP-based criteria. Option D correctly identifies that virtual wire mode inherently does not support IP-based policies.
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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Question Discussion
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