- A
Reboot both firewalls simultaneously to reset the HA state.
Why wrong: Rebooting is a temporary workaround but does not prevent recurrence; the configuration issue remains.
- B
Disable link speed and duplex settings on the HA interfaces to force a failover.
Why wrong: Changing link settings can cause interface instability and is not a recommended method to resolve HA state issues.
- C
Configure the HA mode with the 'preemptive' option and set the device priority higher on the intended active firewall.
Preemptive ensures the higher-priority device becomes active after recovery, preventing both firewalls from staying active.
- D
Set the HA mode to 'active/active' to allow both firewalls to process traffic.
Why wrong: Active/active mode is not appropriate for this situation and would not resolve the split active issue; it requires different configuration.
Resolving Active/Passive HA Split-Brain with Preemptive Option
This PCNSE practice question tests your understanding of managing troubleshooting and high availability. 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 deployed two PA-3220 firewalls in an active/passive high availability configuration. During normal operation, the active firewall (FW-A) handles all traffic. The network team notices that after a brief power outage, both firewalls report as active in the HA pair, causing network instability. The administrator needs to resolve this issue and prevent it from recurring. Which course of action should the administrator take?
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
Configure the HA mode with the 'preemptive' option and set the device priority higher on the intended active firewall.
Option C is correct because configuring the HA mode with the 'preemptive' option ensures that when both firewalls recover from a power outage, the firewall with the higher device priority (the intended active unit) will automatically preempt the other and become active. Without preemption, both firewalls may come up as active if they lose HA heartbeat synchronization during the outage, leading to a split-brain scenario. Setting the device priority higher on FW-A guarantees it is preferred as the active unit upon recovery.
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.
- ✗
Reboot both firewalls simultaneously to reset the HA state.
Why it's wrong here
Rebooting is a temporary workaround but does not prevent recurrence; the configuration issue remains.
- ✗
Disable link speed and duplex settings on the HA interfaces to force a failover.
Why it's wrong here
Changing link settings can cause interface instability and is not a recommended method to resolve HA state issues.
- ✓
Configure the HA mode with the 'preemptive' option and set the device priority higher on the intended active firewall.
Why this is correct
Preemptive ensures the higher-priority device becomes active after recovery, preventing both firewalls from staying active.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Set the HA mode to 'active/active' to allow both firewalls to process traffic.
Why it's wrong here
Active/active mode is not appropriate for this situation and would not resolve the split active issue; it requires different configuration.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume rebooting or resetting the HA state (Option A) is sufficient, but they overlook the need for preemption to automatically resolve the split-brain condition after a power failure, which is a common cause of HA instability in production environments.
Trap categories for this question
Scenario analysis trap
Active/active mode is not appropriate for this situation and would not resolve the split active issue; it requires different configuration.
Detailed technical explanation
How to think about this question
In Palo Alto Networks active/passive HA, the 'preemptive' option (enabled via 'set deviceconfig high-availability group <id> preemptive yes') forces the firewall with the higher priority to become active after both units recover, preventing a split-brain scenario. The device priority (1-65535, higher is preferred) is configured under the HA group settings, and the election process uses this value along with the management IP address as a tiebreaker. In real-world scenarios, power outages can cause both firewalls to boot simultaneously without a heartbeat, and without preemption, they may both assume active state because neither sees the other as the designated active unit.
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.
Visual reference
What to study next
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FAQ
Questions learners often ask
What does this PCNSE question test?
Managing Troubleshooting and High Availability — This question tests Managing Troubleshooting and High Availability — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Configure the HA mode with the 'preemptive' option and set the device priority higher on the intended active firewall. — Option C is correct because configuring the HA mode with the 'preemptive' option ensures that when both firewalls recover from a power outage, the firewall with the higher device priority (the intended active unit) will automatically preempt the other and become active. Without preemption, both firewalls may come up as active if they lose HA heartbeat synchronization during the outage, leading to a split-brain scenario. Setting the device priority higher on FW-A guarantees it is preferred as the active unit upon recovery.
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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Last reviewed: Jul 4, 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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