PCNSE Manage, Monitor and Operate Practice Question
This PCNSE practice question tests your understanding of manage, monitor and operate. 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.
Exhibit
Refer to the exhibit.
Apr 12 14:32:15 PA-500: IKE phase 1 negotiation failed for peer 203.0.113.10 [reason: No Proposal Chosen]
Apr 12 14:32:17 PA-500: IKE phase 1 negotiation failed for peer 203.0.113.10 [reason: No Proposal Chosen]
The firewall log shows repeated IKE phase 1 negotiation failures. The remote peer is a third-party VPN device. Which of the following 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.
Refer to the exhibit.
Apr 12 14:32:15 PA-500: IKE phase 1 negotiation failed for peer 203.0.113.10 [reason: No Proposal Chosen]
Apr 12 14:32:17 PA-500: IKE phase 1 negotiation failed for peer 203.0.113.10 [reason: No Proposal Chosen]
A
The remote peer's firewall is blocking UDP port 500.
Why wrong: Port blocking would lead to no response or timeout, not a 'No Proposal Chosen' error.
B
The pre-shared key is incorrect.
Why wrong: Incorrect PSK leads to authentication failure after proposal is selected, not 'No Proposal Chosen'.
C
The IKE encryption algorithm settings do not match between the local firewall and the remote peer.
Mismatched IKE parameters cause the 'No Proposal Chosen' error during phase 1 negotiation.
D
The IKE version (v1 vs v2) is mismatched between the two devices.
Why wrong: Version mismatch usually results in a 'No acceptable proposal' or 'Version not supported' error.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The IKE encryption algorithm settings do not match between the local firewall and the remote peer.
IKE phase 1 negotiation failures are most commonly caused by mismatched IKE parameters, particularly the encryption algorithm (e.g., AES-256 vs AES-128), hash algorithm, DH group, or lifetime. Since the remote peer is a third-party device, the local firewall and remote peer must agree on all IKE phase 1 proposals; if even one parameter (like encryption) does not match, the negotiation fails. Option C directly addresses this core requirement.
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 remote peer's firewall is blocking UDP port 500.
Why it's wrong here
Port blocking would lead to no response or timeout, not a 'No Proposal Chosen' error.
✗
The pre-shared key is incorrect.
Why it's wrong here
Incorrect PSK leads to authentication failure after proposal is selected, not 'No Proposal Chosen'.
✓
The IKE encryption algorithm settings do not match between the local firewall and the remote peer.
Why this is correct
Mismatched IKE parameters cause the 'No Proposal Chosen' error during phase 1 negotiation.
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 IKE version (v1 vs v2) is mismatched between the two devices.
Why it's wrong here
Version mismatch usually results in a 'No acceptable proposal' or 'Version not supported' error.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume pre-shared key mismatch is the most common cause of IKE phase 1 failures, but in reality, parameter mismatches (especially encryption algorithms) are more frequent and cause negotiation failures before authentication even begins.
Detailed technical explanation
How to think about this question
IKE phase 1 uses a series of SA payloads containing proposals with transforms (encryption, integrity, DH group, lifetime). The initiator sends all configured proposals, and the responder must match exactly one transform from each proposal. If no match is found, the responder sends a 'no proposal chosen' notification, and the initiator retries with the same proposals, leading to repeated failures. In Palo Alto firewalls, you can view the specific IKE phase 1 failure reason in the system logs (e.g., 'IKE phase 1 negotiation failed: no suitable proposal found').
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.
Manage, Monitor and Operate — This question tests Manage, Monitor and Operate — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The IKE encryption algorithm settings do not match between the local firewall and the remote peer. — IKE phase 1 negotiation failures are most commonly caused by mismatched IKE parameters, particularly the encryption algorithm (e.g., AES-256 vs AES-128), hash algorithm, DH group, or lifetime. Since the remote peer is a third-party device, the local firewall and remote peer must agree on all IKE phase 1 proposals; if even one parameter (like encryption) does not match, the negotiation fails. Option C directly addresses this core requirement.
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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