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Policy Evaluation and Management →hardMultiple ChoiceObjective-mapped

PCNSA Policy Evaluation and Management Practice Question

This PCNSA practice question tests your understanding of policy evaluation and management. 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 company has a Palo Alto Networks firewall with multiple virtual routers. The security policy has a rule that allows SSH from the 'Internal' zone to the 'DMZ' zone. Recently, a new subnet 10.10.20.0/24 was added to the Internal zone. Users in that subnet report they cannot SSH to a server at 192.168.1.10 in the DMZ, while users from other subnets in Internal can. The rule has source address object '10.0.0.0/8' which includes the new subnet. The rule's source zone is Internal, destination zone is DMZ, and application is SSH. The administrator confirms the new subnet's IPs are within 10.0.0.0/8. What is the most likely cause of the problem?

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.

A
The application is not correctly identified because the SSH server uses a non-standard port.
Why wrong: Incorrect. The problem is zone/VR-related, not application identification.
B
There is a deny rule placed above the allow rule that matches the new subnet but not the other subnets.
Why wrong: Incorrect. While possible, the question states other subnets in Internal work, so a deny rule specific to the new subnet is unlikely.
C
The firewall's route table has a more specific route for 10.10.20.0/24 pointing to a different virtual router, causing traffic from that subnet to enter via an interface in a different zone.
Correct. If the subnet's traffic enters via a different VR and zone, the security policy rule (which expects the Internal zone) will not match.
D
The rule's source address object is incorrectly defined as '10.0.0.0/8' but the new subnet is not actually within that range.
Why wrong: Incorrect. The subnet 10.10.20.0/24 is within 10.0.0.0/8, so the object includes it.

Full breakdown with real-world context →

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's route table has a more specific route for 10.10.20.0/24 pointing to a different virtual router, causing traffic from that subnet to enter via an interface in a different zone.

The most likely cause is that the new subnet 10.10.20.0/24 is routed through a different virtual router (VR) than the VR used by the Internal zone's interface. In Palo Alto firewalls, security rules are zone-based, and the zone is determined by the ingress interface. If the traffic from the new subnet enters via an interface in a different VR, the zone may not be 'Internal', so the rule allowing SSH from Internal to DMZ does not apply. Option C correctly identifies this scenario.

Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.

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 application is not correctly identified because the SSH server uses a non-standard port.
Why it's wrong here
Incorrect. The problem is zone/VR-related, not application identification.
✗
There is a deny rule placed above the allow rule that matches the new subnet but not the other subnets.
Why it's wrong here
Incorrect. While possible, the question states other subnets in Internal work, so a deny rule specific to the new subnet is unlikely.
✓
The firewall's route table has a more specific route for 10.10.20.0/24 pointing to a different virtual router, causing traffic from that subnet to enter via an interface in a different zone.
Why this is correct
Correct. If the subnet's traffic enters via a different VR and zone, the security policy rule (which expects the Internal zone) will not match.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
CIDR notation defines the prefix length.
✗
The rule's source address object is incorrectly defined as '10.0.0.0/8' but the new subnet is not actually within that range.
Why it's wrong here
Incorrect. The subnet 10.10.20.0/24 is within 10.0.0.0/8, so the object includes it.

Common exam traps

Common exam trap: usable hosts are not the same as total addresses

Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.

Detailed technical explanation

How to think about this question

Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.

KKey Concepts to Remember

CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.

TExam Day Tips

Write the block size before choosing the subnet.
Check whether the question asks for hosts, subnets or a specific address range.
Do not confuse /24, /25, /26 and /27 host counts.

Key takeaway

Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.

Real-world example

How this comes up in practice

A security administrator must allow nursing staff to reach a patient records server while blocking access from the guest Wi-Fi VLAN. After applying an extended ACL, traffic is still blocked from nursing workstations. The ACL was applied outbound instead of inbound on the wrong interface. Questions like this test ACL direction and placement rules.

Visual reference

What to study next

Got this wrong? Here's your next step.

Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related PCNSA subnetting questions on CIDR, address ranges, and subnet selection.

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FAQ

Questions learners often ask

What does this PCNSA question test?

Policy Evaluation and Management — This question tests Policy Evaluation and Management — CIDR notation defines the prefix length..

What is the correct answer to this question?

The correct answer is: The firewall's route table has a more specific route for 10.10.20.0/24 pointing to a different virtual router, causing traffic from that subnet to enter via an interface in a different zone. — The most likely cause is that the new subnet 10.10.20.0/24 is routed through a different virtual router (VR) than the VR used by the Internal zone's interface. In Palo Alto firewalls, security rules are zone-based, and the zone is determined by the ingress interface. If the traffic from the new subnet enters via an interface in a different VR, the zone may not be 'Internal', so the rule allowing SSH from Internal to DMZ does not apply. Option C correctly identifies this scenario.

What should I do if I get this PCNSA question wrong?

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?

CIDR notation defines the prefix length.

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This PCNSA 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 PCNSA exam.