PCNSE Core Concepts and Architecture Practice Question
A Palo Alto Networks firewall is configured with two virtual routers: VR-A (trust) and VR-B (untrust). An interface is placed in VR-A. A static route to 10.0.0.0/8 via next-hop 192.168.1.1 exists in VR-A. The firewall receives a packet from the trust zone destined to 10.1.1.1. The route lookup succeeds in VR-A. Which statement is true about the forwarding decision?
⚠ Common exam trap
Many exam-takers assume the packet will be dropped because the destination is in a different VR (Option C), but they overlook that the route lookup succeeded in the ingress VR, meaning the egress interface is within the same VR, and the real security mechanism is the RPF check on the source IP.
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
✓
The firewall will perform a reverse path forwarding (RPF) check on the source IP.
When a packet enters a Palo Alto Networks firewall, after a successful route lookup, the firewall performs an RPF check on the source IP address to ensure that the source is reachable via the ingress interface. This is a fundamental security mechanism to prevent spoofed traffic. Since the ingress interface is in VR-A and the route lookup succeeded, the RPF check verifies that the source IP of the packet is reachable through that same interface; if not, the packet is dropped.
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 firewall will automatically redistribute the route to VR-B if needed.
Why it's wrong here
Redistribution must be configured explicitly; it is not automatic.
- ✓
The firewall will perform a reverse path forwarding (RPF) check on the source IP.
Why this is correct
RPF ensures the source IP is reachable via the incoming interface; if not, the packet may be dropped.
- ✗
The packet will be dropped because the destination is not in the same VR as the ingress interface.
Why it's wrong here
The destination is in VR-A, which matches the ingress interface's VR.
- ✗
The firewall will use the zone of the egress interface to determine the security policy.
Why it's wrong here
Policy lookup uses ingress and egress zones; the egress zone is based on the route, but the statement is true in general, however the question asks about the forwarding decision specifically.
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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.