- A
The rule is placed after an allow rule that matches the traffic
Why wrong: If the block rule is below an allow rule, the allow rule will match first, but the administrator said the rule is placed correctly; this is a possible cause but less likely if ordering is verified.
- B
The source and destination zones are set to 'any'
Why wrong: Setting zones to 'any' would not prevent the rule from matching; it would broaden the match.
- C
There is an implicit allow rule that overrides the block rule
Why wrong: The implicit rule at the end is deny, not allow. Only explicit allow rules can override.
- D
The rule is configured in the PBF rulebase instead of the Security rulebase
Policy-Based Forwarding rules do not enforce security; they only redirect traffic. If the rule was accidentally placed in PBF, it would not block.
Quick Answer
The answer is that the rule was configured in the Policy-Based Forwarding (PBF) rulebase instead of the Security rulebase. This is correct because PBF rules are evaluated before security rules in the Palo Alto Networks firewall processing order, and a matching PBF rule can bypass the security rulebase entirely by forwarding traffic based on routing criteria rather than security policy. On the PCNSA exam, this concept tests your understanding of rule evaluation precedence and the common misconfiguration trap where administrators mistakenly place a block action in PBF, which only supports forwarding actions like next-hop or egress interface, not deny. A reliable memory tip is "PBF forwards first, security blocks later"—if traffic matches a PBF rule, it never reaches the security rulebase for inspection, so any block rule there is effectively ignored.
PCNSA Core Concepts Practice Question
This PCNSA practice question tests your understanding of core concepts. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
An administrator configures a security policy rule to block traffic from IP address 10.1.1.1 to 10.2.2.2 on any service. However, traffic from 10.1.1.1 to 10.2.2.2 is still passing through the firewall. After checking all rules, 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.
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 rule is configured in the PBF rulebase instead of the Security rulebase
Policy-Based Forwarding (PBF) rules are evaluated before security rules and can override security policy decisions. If the traffic matches a PBF rule, it may be forwarded without being subject to the security rulebase, even if a security rule explicitly blocks it. This is the most likely cause because the administrator configured the block in the wrong rulebase.
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 rule is placed after an allow rule that matches the traffic
Why it's wrong here
If the block rule is below an allow rule, the allow rule will match first, but the administrator said the rule is placed correctly; this is a possible cause but less likely if ordering is verified.
- ✗
The source and destination zones are set to 'any'
Why it's wrong here
Setting zones to 'any' would not prevent the rule from matching; it would broaden the match.
- ✗
There is an implicit allow rule that overrides the block rule
Why it's wrong here
The implicit rule at the end is deny, not allow. Only explicit allow rules can override.
- ✓
The rule is configured in the PBF rulebase instead of the Security rulebase
Why this is correct
Policy-Based Forwarding rules do not enforce security; they only redirect traffic. If the rule was accidentally placed in PBF, it would not block.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume all traffic filtering is done in the security rulebase and overlook the existence and precedence of the PBF rulebase, which can cause traffic to bypass security rules entirely.
Detailed technical explanation
How to think about this question
PBF rules are processed in a separate rulebase and can direct traffic based on source, destination, or application before security rules are applied. If a PBF rule matches, the firewall forwards the traffic according to the PBF action (e.g., forward to a next hop) without consulting the security rulebase, effectively bypassing any block rules. This is a common misconfiguration when administrators intend to block traffic but inadvertently place the rule in the PBF rulebase, which is designed for path selection, not access control.
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.
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Core Concepts — study guide chapter
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FAQ
Questions learners often ask
What does this PCNSA question test?
Core Concepts — This question tests Core Concepts — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The rule is configured in the PBF rulebase instead of the Security rulebase — Policy-Based Forwarding (PBF) rules are evaluated before security rules and can override security policy decisions. If the traffic matches a PBF rule, it may be forwarded without being subject to the security rulebase, even if a security rule explicitly blocks it. This is the most likely cause because the administrator configured the block in the wrong rulebase.
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.
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.
About these practice questions
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Last reviewed: Jun 25, 2026
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.
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