PCNSE Core Concepts and Architecture Practice Question
A company needs to deploy a firewall in transparent inline mode to filter traffic between two switches without requiring any IP address changes on existing devices. Which interface type should be configured?
⚠ Common exam trap
Watch out — candidates often confuse Layer2 interfaces with Virtual Wire, assuming any transparent mode works the same, but Layer2 interfaces require bridge groups or VLAN configuration and do not provide the same zero-touch inline deployment as Virtual Wire.
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
✓
Virtual Wire
Virtual Wire (VWire) is the correct interface type because it allows the firewall to operate in transparent inline mode without requiring any IP address changes on existing devices. In VWire mode, the firewall acts as a Layer 2 bump in the wire, forwarding traffic between two interfaces based on MAC addresses without participating in routing or requiring IP configuration on the firewall interfaces themselves.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Virtual Wire
Why this is correct
Virtual Wire binds two interfaces into a transparent pair that forwards traffic without MAC or IP addressing, so existing switches and devices keep their addresses unchanged. It filters inline between the switches while remaining invisible at layer three.
- ✗
Tap
Why it's wrong here
Tap interfaces receive mirrored traffic passively and cannot forward or block it inline; transparent mode requires traffic to traverse the firewall. It is tempting because taps monitor without IP changes, but they only copy frames, so they cannot filter between the two switches as required.
- ✗
Layer3
Why it's wrong here
Layer3 interfaces require IP addresses and route between subnets, which changes the existing addressing scheme the scenario forbids. It tempts because Layer3 is the standard firewall deployment, but transparent inline filtering needs a virtual wire binding two Layer2 interfaces, not routed interfaces.
- ✗
Layer2
Why it's wrong here
Layer2 interfaces carry traffic without IP addressing, but transparent mode on Palo Alto firewalls requires a virtual wire pairing two Layer2 interfaces, so a single Layer2 interface cannot bridge the two switches. It tempts because Layer2 is genuinely the transparent-mode building block, yet the vwire object is what forwards frames.
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
Go deeper
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.