The answer is that the IKE gateway's rekey lifetime is shorter than the IPsec security association lifetime. This mismatch causes the GlobalProtect tunnel rekey failed error because the IKE Phase 1 SA expires before the Phase 2 IPsec SA can complete its rekey process, forcing the tunnel to drop and disconnecting users. On the PCNSE exam, this scenario tests your understanding of IKE and IPsec lifecycle management, often appearing as a troubleshooting question where logs show frequent disconnections despite correct pre-shared keys. A common trap is assuming the error points to a certificate or authentication issue, but the root cause is always a lifetime misconfiguration. To remember: think of IKE Phase 1 as the "master key" that must outlast the "room keys" (Phase 2 SAs) it creates; if the master key expires first, all rooms lock simultaneously.
PCNSE Secure Access and VPN Practice Question
This PCNSE practice question tests your understanding of secure access and vpn. 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.
An administrator is troubleshooting a GlobalProtect VPN where users report frequent disconnections. The administrator notices that the GlobalProtect gateway logs show 'Tunnel rekey failed' errors. 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 the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The IKE gateway's rekey lifetime is shorter than the IPSec security association lifetime.
The 'Tunnel rekey failed' error indicates that the IPsec security association (SA) rekey process failed. This most commonly occurs when the IKE gateway's rekey lifetime is shorter than the IPsec SA lifetime, causing the IKE phase 1 SA to expire before the IPsec phase 2 SA can be rekeyed. As a result, the tunnel drops and the client disconnects.
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 GlobalProtect app's cookie integrity is corrupted.
Why it's wrong here
Cookie integrity is for authentication, not tunnel rekey.
✓
The IKE gateway's rekey lifetime is shorter than the IPSec security association lifetime.
Why this is correct
If the IKE rekey lifetime expires before the IPSec SA, the tunnel may be torn down unexpectedly.
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 GlobalProtect client needs to be reinstalled.
Why it's wrong here
Reinstall is not a typical troubleshooting step for rekey failures.
✗
The user-id agent is not resolving usernames correctly.
Why it's wrong here
User-ID does not impact tunnel rekey.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume client-side issues (like app corruption or reinstallation) are the cause, when the error is clearly a gateway-side IPsec rekey misconfiguration.
Detailed technical explanation
How to think about this question
In IPsec VPNs, the IKE phase 1 SA is used to securely negotiate phase 2 IPsec SAs. If the IKE phase 1 lifetime (e.g., 8 hours) is set shorter than the IPsec SA lifetime (e.g., 1 hour), the IKE SA may expire before the IPsec SA needs rekeying, causing the rekey to fail. The correct configuration is to ensure the IKE gateway lifetime is longer than the IPsec SA lifetime, typically by a factor of 2 or more, to allow for successful rekey operations.
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.
Secure Access and VPN — This question tests Secure Access and VPN — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The IKE gateway's rekey lifetime is shorter than the IPSec security association lifetime. — The 'Tunnel rekey failed' error indicates that the IPsec security association (SA) rekey process failed. This most commonly occurs when the IKE gateway's rekey lifetime is shorter than the IPsec SA lifetime, causing the IKE phase 1 SA to expire before the IPsec phase 2 SA can be rekeyed. As a result, the tunnel drops and the client disconnects.
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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Question Discussion
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