- A
The HA pair is in active/active mode
Why wrong: Active/active syncs all sessions.
- B
The failover delay timer is too long
Why wrong: Failover delay affects timing, not session preservation.
- C
UDP sessions are not synchronized by default in active/passive mode
Only TCP sessions are synced by default; UDP sessions require additional configuration.
- D
Session synchronization is disabled on the passive firewall
Why wrong: Session sync is generally enabled on both.
Question 489 of 516
UDP Session Not Synchronized by Default in Active/Passive HA
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.
During a failover test, an engineer observes that after the active firewall fails, the passive firewall takes over, but existing UDP sessions are not maintained. What is the most likely reason?
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
✓
UDP sessions are not synchronized by default in active/passive mode
In an active/passive HA pair, session synchronization is enabled by default for TCP sessions but not for UDP sessions. UDP is considered connectionless, and the firewall does not maintain state information for UDP flows in the same way as TCP. Therefore, when a failover occurs, existing UDP sessions are not preserved because their state was never synchronized to the passive firewall.
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 HA pair is in active/active mode
Why it's wrong here
Active/active syncs all sessions.
- ✗
The failover delay timer is too long
Why it's wrong here
Failover delay affects timing, not session preservation.
- ✓
UDP sessions are not synchronized by default in active/passive mode
- ✗
Session synchronization is disabled on the passive firewall
Why it's wrong here
Session sync is generally enabled on both.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume all sessions are synchronized by default in active/passive HA, but the PCNSE exam specifically tests the nuance that UDP sessions are not synchronized unless explicitly configured.
Detailed technical explanation
How to think about this question
Palo Alto Networks firewalls use a session table that tracks TCP and UDP flows, but only TCP sessions are synchronized to the passive firewall by default in active/passive HA. This is because UDP is stateless and many UDP-based applications (e.g., DNS, VoIP) can tolerate brief interruptions or re-establish flows. To synchronize UDP sessions, you must explicitly enable 'session sync' for UDP under the HA configuration, which adds overhead and is typically only needed for critical UDP-based services.
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: UDP sessions are not synchronized by default in active/passive mode — In an active/passive HA pair, session synchronization is enabled by default for TCP sessions but not for UDP sessions. UDP is considered connectionless, and the firewall does not maintain state information for UDP flows in the same way as TCP. Therefore, when a failover occurs, existing UDP sessions are not preserved because their state was never synchronized to the passive firewall.
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.
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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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