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.
Exhibit
Refer to the exhibit.
admin@PA-5250> show routing route
IPv4 Route Table for virtual-router default
destination nexthop metric flags interface age
0.0.0.0/0 10.1.1.1 10 A S ethernet1/1 5m
10.1.1.0/24 10.1.1.100 0 A C ethernet1/1 5m
10.2.2.0/24 10.1.1.200 1 A S ethernet1/1 5m
10.3.3.0/24 10.1.1.200 1 A S ethernet1/1 5m
Refer to the exhibit. An administrator is troubleshooting traffic from a host at 10.2.2.10 to a server at 10.3.3.10. The firewall has a security rule allowing the traffic. However, traffic is failing. Based on the routing table, 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.
Refer to the exhibit.
admin@PA-5250> show routing route
IPv4 Route Table for virtual-router default
destination nexthop metric flags interface age
0.0.0.0/0 10.1.1.1 10 A S ethernet1/1 5m
10.1.1.0/24 10.1.1.100 0 A C ethernet1/1 5m
10.2.2.0/24 10.1.1.200 1 A S ethernet1/1 5m
10.3.3.0/24 10.1.1.200 1 A S ethernet1/1 5m
A
The next hop 10.1.1.200 for the destination 10.3.3.0/24 is unreachable.
If next hop is down, traffic cannot be forwarded.
B
The destination network 10.3.3.0/24 is not in the routing table.
Why wrong: 10.3.3.0/24 is present.
C
The source network 10.2.2.0/24 is not in the routing table.
Why wrong: 10.2.2.0/24 is present with next hop 10.1.1.200.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The next hop 10.1.1.200 for the destination 10.3.3.0/24 is unreachable.
The routing table shows a route to 10.3.3.0/24 with next hop 10.1.1.200. If that next hop is unreachable (e.g., due to an ARP failure, interface down, or no route to the next hop itself), the firewall cannot forward the packet to the destination, even though a security rule permits the traffic. This is the most likely cause of the failure because the route exists but the next hop is not reachable.
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 next hop 10.1.1.200 for the destination 10.3.3.0/24 is unreachable.
Why this is correct
If next hop is down, traffic cannot be forwarded.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The destination network 10.3.3.0/24 is not in the routing table.
Why it's wrong here
10.3.3.0/24 is present.
✗
The source network 10.2.2.0/24 is not in the routing table.
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume a missing route is the problem, but the question tests whether you recognize that a route can exist yet still fail if the next hop is unreachable.
Detailed technical explanation
How to think about this question
When a firewall forwards a packet, it performs a route lookup on the destination IP and then attempts to resolve the next-hop IP via ARP (for Ethernet interfaces). If the next-hop IP is unreachable (e.g., no ARP reply, interface down, or the next-hop itself has no route back), the firewall will drop the packet and may generate an ICMP Destination Unreachable (Host Unreachable) message. In production, this often occurs after a link failure or misconfiguration of the next-hop router, and can be diagnosed using 'show routing route' and 'ping' from the firewall to the next hop.
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.
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: The next hop 10.1.1.200 for the destination 10.3.3.0/24 is unreachable. — The routing table shows a route to 10.3.3.0/24 with next hop 10.1.1.200. If that next hop is unreachable (e.g., due to an ARP failure, interface down, or no route to the next hop itself), the firewall cannot forward the packet to the destination, even though a security rule permits the traffic. This is the most likely cause of the failure because the route exists but the next hop is not reachable.
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". 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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Question Discussion
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