The correct approach is to do nothing, because by default, inter-zone traffic from DMZ to Untrust is already blocked. This is due to the fundamental security principle of implicit deny for inter-zone traffic on Palo Alto Networks firewalls: any traffic crossing between different security zones is denied unless an explicit security policy rule permits it. Since the administrator only created a rule allowing web traffic from Untrust to DMZ, no rule exists for the reverse direction, so the implicit deny automatically blocks any DMZ-initiated connections to the Untrust zone without additional configuration. On the PCNSA exam, this concept tests your understanding of zone-based security and the default deny-all posture—a common trap is assuming you need to create a deny rule, when in fact the absence of a permit rule is sufficient. Remember the memory tip: “No rule, no route—implicit deny does the work for you.”
PCNSA Palo Alto Networks Platforms and Architecture Practice Question
This PCNSA practice question tests your understanding of palo alto networks platforms and architecture. 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 firewall is configured with multiple security zones. Traffic from the 'Untrust' zone to the 'DMZ' zone is allowed for web services. The administrator wants to ensure that the DMZ servers cannot initiate connections to the Untrust zone. What is the correct approach?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Do nothing; by default, inter-zone traffic from DMZ to Untrust is blocked.
Option D is correct because, by default, Palo Alto Networks firewalls use an implicit deny rule for all inter-zone traffic that is not explicitly allowed. Since the administrator has only created a rule permitting traffic from Untrust to DMZ for web services, no rule exists to permit traffic from DMZ to Untrust, so the implicit deny blocks any DMZ-initiated connections to the Untrust zone without any additional configuration.
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.
✗
Configure a zone protection profile on the DMZ zone.
Why it's wrong here
Zone protection profiles prevent attacks, not outbound connections.
✗
Create a rule allowing traffic from Untrust to DMZ and another rule allowing DMZ to Untrust.
Why it's wrong here
This would allow DMZ to initiate connections, which is not desired.
✗
Create a rule allowing traffic from DMZ to Untrust with a deny action.
Why it's wrong here
This would create an explicit deny, but the default already blocks; this adds unnecessary complexity.
✓
Do nothing; by default, inter-zone traffic from DMZ to Untrust is blocked.
Why this is correct
The default inter-zone rule blocks all traffic that is not explicitly allowed.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume they must create an explicit deny rule to block traffic from DMZ to Untrust, not realizing that Palo Alto Networks firewalls already block all inter-zone traffic by default unless a permit rule is explicitly configured.
Detailed technical explanation
How to think about this question
Palo Alto Networks firewalls enforce a default-deny policy for all inter-zone traffic, meaning that unless an explicit security rule permits traffic from a source zone to a destination zone, the traffic is dropped. This behavior is based on the zone-based security model, where each zone is a logical grouping of interfaces, and inter-zone rules are evaluated in order; if no matching rule is found, the implicit deny rule (which is not visible in the rulebase) applies. In real-world scenarios, this default behavior simplifies security by ensuring that only explicitly allowed traffic flows between zones, reducing the risk of misconfiguration.
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 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.
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.
Palo Alto Networks Platforms and Architecture — This question tests Palo Alto Networks Platforms and Architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Do nothing; by default, inter-zone traffic from DMZ to Untrust is blocked. — Option D is correct because, by default, Palo Alto Networks firewalls use an implicit deny rule for all inter-zone traffic that is not explicitly allowed. Since the administrator has only created a rule permitting traffic from Untrust to DMZ for web services, no rule exists to permit traffic from DMZ to Untrust, so the implicit deny blocks any DMZ-initiated connections to the Untrust zone without any additional configuration.
What should I do if I get this PCNSA question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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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.
Question Discussion
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