The answer is that the last failover was caused by the HA1 keepalive from the peer being lost. This occurs when the passive firewall in an active/passive pair stops receiving the periodic keepalive messages sent by the active peer over the dedicated HA1 control link. If these messages are not received within the configured hello interval and hold timer—defaulting to one and three seconds respectively—the passive unit assumes the active peer has failed and triggers a failover to take over as active. On the Palo Alto Networks PCNSE exam, this scenario tests your understanding of high availability monitoring and failover triggers, often appearing in exhibits showing the "last failover reason" field under device state. A common trap is confusing HA1 keepalive loss with HA2 data link failures or link monitoring events, but remember that HA1 is strictly for control-plane heartbeats. Memory tip: think of HA1 as the "heartbeat" link—if the heart stops beating, the passive takes over.
PCNSE Practice Question: Managing Troubleshooting and High Availability
This PCNSE practice question tests your understanding of managing troubleshooting and high availability. 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.
Exhibit
Refer to the exhibit.
admin@PA-5050> show high-availability state
HA state: active
peer HA state: passive
link status: up
HA1 link status: up
HA2 link status: up
last failure reason: peer HA1 keepalive lost
Based on the exhibit, what caused the last failover?
Refer to the exhibit.
admin@PA-5050> show high-availability state
HA state: active
peer HA state: passive
link status: up
HA1 link status: up
HA2 link status: up
last failure reason: peer HA1 keepalive lost
A
The HA2 link went down.
Why wrong: The HA2 link status is up.
B
A preemption event occurred.
Why wrong: No preemption is indicated.
C
The peer firewall was rebooted.
Why wrong: The output does not mention reboot; it specifically says keepalive lost.
D
The HA1 keepalive from the peer was lost.
The output shows 'last failure reason: peer HA1 keepalive lost'.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The HA1 keepalive from the peer was lost.
The exhibit shows 'HA1 keepalive from the peer was lost' as the last failover reason. In an active/passive HA pair, the passive firewall monitors HA1 keepalive messages from the active peer. When these keepalives are not received within the configured hello interval (default 1 second) and hold timer (default 3 seconds), the passive firewall assumes the active peer has failed and initiates a failover to become active.
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 HA2 link went down.
Why it's wrong here
The HA2 link status is up.
✗
A preemption event occurred.
Why it's wrong here
No preemption is indicated.
✗
The peer firewall was rebooted.
Why it's wrong here
The output does not mention reboot; it specifically says keepalive lost.
✓
The HA1 keepalive from the peer was lost.
Why this is correct
The output shows 'last failure reason: peer HA1 keepalive lost'.
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 confuse the HA1 link (control link for keepalives) with the HA2 link (data link for session sync), leading them to incorrectly select Option A when the actual failover trigger is loss of HA1 keepalive, not HA2 link failure.
Trap categories for this question
Command / output trap
The output does not mention reboot; it specifically says keepalive lost.
Detailed technical explanation
How to think about this question
The HA1 keepalive mechanism uses UDP port 694 by default, with packets sent every 1 second (hello interval) and a hold timer of 3 seconds (3 missed hellos). The failover reason is logged in the HA state transition log and can be viewed via 'show high-availability state' or in the GUI under Device > High Availability > General > Last Failover Reason. In real-world scenarios, a flapping HA1 link or asymmetric routing can cause intermittent keepalive loss, leading to unnecessary failovers even if the active firewall is still processing traffic.
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.
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: The HA1 keepalive from the peer was lost. — The exhibit shows 'HA1 keepalive from the peer was lost' as the last failover reason. In an active/passive HA pair, the passive firewall monitors HA1 keepalive messages from the active peer. When these keepalives are not received within the configured hello interval (default 1 second) and hold timer (default 3 seconds), the passive firewall assumes the active peer has failed and initiates a failover to become active.
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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