PCNSE Core Concepts and Architecture Practice Question
This PCNSE practice question tests your understanding of core concepts 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 company has configured a security policy that allows HTTP traffic from the internal network 10.0.0.0/8 to the internet. However, users from subnet 10.2.0.0/24 are unable to access external websites. The firewall logs show that traffic from 10.2.0.100 to 203.0.113.1 on port 80 is being denied. Which action should the administrator take to resolve the issue?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Add a new security rule allowing traffic from 10.2.0.0/24 and place it above the existing deny rule.
Option C is correct because in a stateful firewall like Palo Alto Networks, security rules are evaluated in order from top to bottom, and the first matching rule is applied. If a deny rule exists above any allow rule for the 10.2.0.0/24 subnet, traffic from that subnet will be denied. Adding a new allow rule for 10.2.0.0/24 and placing it above the existing deny rule ensures that HTTP traffic from that subnet is permitted before reaching the deny rule.
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.
✗
Modify the existing allow rule to include the entire 10.2.0.0/24 subnet in the source.
Why it's wrong here
Modifying the existing rule might not work if there is a deny rule above it still matching.
✗
Change the destination zone of the allow rule to 'any'.
Why it's wrong here
Changing the destination zone is not relevant; the issue is rule order.
✓
Add a new security rule allowing traffic from 10.2.0.0/24 and place it above the existing deny rule.
Why this is correct
A rule placed higher in the order matches first. Adding an allow rule above the deny rule will permit the traffic.
Related concept
Read the scenario before looking for a memorised answer.
✗
Delete the deny rule that is blocking the traffic.
Why it's wrong here
Deleting the deny rule could expose other traffic that should be blocked.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume modifying the existing allow rule or deleting the deny rule will fix the issue, but they overlook the fundamental principle of rule order in a first-match firewall, where a higher-priority deny rule will block traffic even if a lower-priority allow rule exists.
Detailed technical explanation
How to think about this question
Palo Alto Networks firewalls use a first-match rule evaluation model, meaning that once a rule matches, no further rules are evaluated. This is critical when overlapping subnets exist; a deny rule for a broader range (e.g., 10.0.0.0/8) can inadvertently block a more specific subnet if placed above an allow rule. In real-world scenarios, administrators often use rule placement and specific source/destination objects to create granular access without disrupting existing security policies.
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.
Core Concepts and Architecture — This question tests Core Concepts and Architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add a new security rule allowing traffic from 10.2.0.0/24 and place it above the existing deny rule. — Option C is correct because in a stateful firewall like Palo Alto Networks, security rules are evaluated in order from top to bottom, and the first matching rule is applied. If a deny rule exists above any allow rule for the 10.2.0.0/24 subnet, traffic from that subnet will be denied. Adding a new allow rule for 10.2.0.0/24 and placing it above the existing deny rule ensures that HTTP traffic from that subnet is permitted before reaching the deny rule.
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.
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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