- A
Both firewalls have the same priority; the tie is broken by serial number, but due to simultaneous reboot, both came up as active. The solution is to reboot one firewall.
Why wrong: Priority and serial number determine active, but simultaneous reboot should still result in one active based on tie-breaker; split-brain typically indicates heartbeat failure.
- B
The HA configuration is set to active/active mode instead of active/passive.
Why wrong: In active/active, both are always active, but the question says active/passive.
- C
The heartbeat link between the firewalls is missing or fails, causing each to believe the other is down. The correct step is to restore the heartbeat link and then set the appropriate firewall as passive.
Split-brain is usually due to lost heartbeat; restoring it and setting one as passive resolves.
- D
The heartbeat interfaces are not configured on each firewall.
Why wrong: If heartbeat interfaces are configured but down, it would cause split-brain; but the correct fix is to first check them.
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.
Two Palo Alto Networks firewalls are configured in an active/passive HA pair. During a scheduled maintenance, the network team reboots both firewalls simultaneously. After reboot, both firewalls appear as 'active' in the HA state. What is the most likely cause and the correct troubleshooting step?
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 heartbeat link between the firewalls is missing or fails, causing each to believe the other is down. The correct step is to restore the heartbeat link and then set the appropriate firewall as passive.
In an active/passive HA pair, each firewall monitors the peer's health via the heartbeat link. If the heartbeat link fails, each firewall assumes the peer is down and transitions to active state to ensure traffic continuity. Simultaneous reboot does not cause both to become active unless the heartbeat link is absent or broken; restoring the heartbeat link and forcing one firewall to passive resolves the split-brain scenario.
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.
- ✗
Both firewalls have the same priority; the tie is broken by serial number, but due to simultaneous reboot, both came up as active. The solution is to reboot one firewall.
Why it's wrong here
Priority and serial number determine active, but simultaneous reboot should still result in one active based on tie-breaker; split-brain typically indicates heartbeat failure.
- ✗
The HA configuration is set to active/active mode instead of active/passive.
Why it's wrong here
In active/active, both are always active, but the question says active/passive.
- ✓
The heartbeat link between the firewalls is missing or fails, causing each to believe the other is down. The correct step is to restore the heartbeat link and then set the appropriate firewall as passive.
Why this is correct
Split-brain is usually due to lost heartbeat; restoring it and setting one as passive resolves.
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 heartbeat interfaces are not configured on each firewall.
Why it's wrong here
If heartbeat interfaces are configured but down, it would cause split-brain; but the correct fix is to first check them.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume simultaneous reboot causes a priority tie, but the real issue is the missing heartbeat link, which prevents the firewalls from detecting each other's state after reboot.
Detailed technical explanation
How to think about this question
The heartbeat link uses UDP port 2928 (or TCP for HA3) and carries keepalive messages every 1 second by default; if three consecutive keepalives are missed, the peer is considered down. In a split-brain scenario, both firewalls become active and may forward traffic, causing routing loops or duplicate IP address conflicts; the correct recovery is to restore the heartbeat link and issue 'request high-availability state passive' on the intended passive firewall.
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 practitioner preparing for the PCNSE exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
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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FAQ
Questions learners often ask
What does this PCNSE question test?
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: The heartbeat link between the firewalls is missing or fails, causing each to believe the other is down. The correct step is to restore the heartbeat link and then set the appropriate firewall as passive. — In an active/passive HA pair, each firewall monitors the peer's health via the heartbeat link. If the heartbeat link fails, each firewall assumes the peer is down and transitions to active state to ensure traffic continuity. Simultaneous reboot does not cause both to become active unless the heartbeat link is absent or broken; restoring the heartbeat link and forcing one firewall to passive resolves the split-brain scenario.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 25, 2026
This PCNSE 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 PCNSE exam.
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