- A
The default route is not in the same virtual router as the internal zones.
If internal zones are in a different VR, traffic from them cannot use the default route, resulting in no route to host.
- B
The new internet circuit does not allow ICMP.
Why wrong: ICMP blocking would not cause 'no route to host'; it would cause timeouts or unreachable messages.
- C
The internal hosts have incorrect DNS settings.
Why wrong: Incorrect DNS settings would cause name resolution failures, not route drops.
- D
The ARP table for the gateway is stale.
Why wrong: A stale ARP entry would cause intermittent issues, but the error would be 'no ARP' not 'no route to host'.
Question 347 of 516
Resolve Internet Traffic Failure Due to Virtual Router Mismatch
This PCNSE practice question tests your understanding of troubleshoot. 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 healthcare organization recently replaced their primary internet circuit and changed the next-hop IP for the default route from 203.0.113.1 to 198.51.100.1. After the change, all internet traffic is failing. The firewall is a PA-220 running PAN-OS 9.1. The administrator verifies that the new default route is present in the virtual router and that the security policies are unchanged. The IP address configuration on the ethernet interface is correct and the link is up. When pinging 8.8.8.8 from the firewall's management interface, it succeeds. But traffic from internal hosts fails. The traffic log shows 'drop' with reason 'route - no route to host'. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Clue:
"primary"Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
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 default route is not in the same virtual router as the internal zones.
The traffic log shows 'route - no route to host', which indicates the firewall cannot find a valid path for the traffic. Even though the default route is present in the virtual router, if the internal zones (e.g., trust zone) are in a different virtual router than the one containing the default route, the firewall will not use that default route for traffic from those zones. Each virtual router maintains its own routing table, and inter-virtual-router routing requires explicit route leaking or redistribution.
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 default route is not in the same virtual router as the internal zones.
Why this is correct
If internal zones are in a different VR, traffic from them cannot use the default route, resulting in no route to host.
Clue confirmation
The clue words "most likely", "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The new internet circuit does not allow ICMP.
Why it's wrong here
ICMP blocking would not cause 'no route to host'; it would cause timeouts or unreachable messages.
- ✗
The internal hosts have incorrect DNS settings.
Why it's wrong here
Incorrect DNS settings would cause name resolution failures, not route drops.
- ✗
The ARP table for the gateway is stale.
Why it's wrong here
A stale ARP entry would cause intermittent issues, but the error would be 'no ARP' not 'no route to host'.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume a default route in any virtual router applies globally, but PAN-OS enforces strict virtual router isolation per zone, so the route must be in the same virtual router as the source zone's interface.
Detailed technical explanation
How to think about this question
In PAN-OS, virtual routers are isolated routing domains; a default route in one virtual router is not automatically used by zones bound to another virtual router. This is analogous to VRF-lite in Cisco IOS, where each VRF has its own routing table. The 'route - no route to host' drop occurs when the firewall performs a longest-prefix match lookup in the virtual router associated with the ingress zone and finds no matching route, including the default route if it resides in a different virtual router.
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 practitioner preparing for the PCNSE exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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.
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Troubleshoot — study guide chapter
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FAQ
Questions learners often ask
What does this PCNSE question test?
Troubleshoot — This question tests Troubleshoot — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The default route is not in the same virtual router as the internal zones. — The traffic log shows 'route - no route to host', which indicates the firewall cannot find a valid path for the traffic. Even though the default route is present in the virtual router, if the internal zones (e.g., trust zone) are in a different virtual router than the one containing the default route, the firewall will not use that default route for traffic from those zones. Each virtual router maintains its own routing table, and inter-virtual-router routing requires explicit route leaking or redistribution.
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.
Are there clue words in this question I should notice?
Yes — watch for: "most likely", "primary". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
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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