CCSM Advanced Firewall Troubleshooting Practice Question
A Check Point administrator is investigating why a VPN tunnel between two gateways is not establishing. The administrator runs 'vpn debug ikeon' and reviews the IKE debug output, which shows 'Received notification from peer: NO_PROPOSAL_CHOSEN'. What is the most likely cause of this error?
⚠ Common exam trap
The trap here is assuming that any VPN negotiation failure is due to authentication issues like pre-shared keys or certificates, when 'NO_PROPOSAL_CHOSEN' specifically points to a mismatch in IKE Phase 1 proposal parameters.
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
✓
The IKE Phase 1 proposal settings (encryption, hash, DH group) do not match between the two gateways.
The correct answer is that the IKE Phase 1 proposal settings do not match. 'NO_PROPOSAL_CHOSEN' is an explicit error indicating that the responder rejected the initiator's proposal because no acceptable proposal was found. This is resolved by aligning the encryption, hash, DH group, and lifetime settings on both gateways. Other issues like pre-shared key or certificates would produce different errors.
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 pre-shared key is incorrect on one of the gateways.
Why it's wrong here
An incorrect pre-shared key typically results in an authentication failure, not 'NO_PROPOSAL_CHOSEN'. The error 'NO_PROPOSAL_CHOSEN' indicates that the IKE proposal (encryption, hash, DH group) does not match between peers. The pre-shared key is used in the authentication phase, which occurs after proposal selection. Therefore, this is not the likely cause of the specific error message.
- ✗
The gateway's certificate has expired, causing IKE negotiation to fail.
Why it's wrong here
An expired certificate would cause an authentication failure, not 'NO_PROPOSAL_CHOSEN'. The certificate is used for authentication, which happens after the proposal is accepted. The error 'NO_PROPOSAL_CHOSEN' indicates a proposal mismatch, so certificate issues are not the cause. The administrator should check certificate validity separately if authentication fails after proposal agreement.
- ✓
The IKE Phase 1 proposal settings (encryption, hash, DH group) do not match between the two gateways.
Why this is correct
'NO_PROPOSAL_CHOSEN' is a standard IKE error indicating that the responder could not agree on a proposal from the initiator. This means the IKE Phase 1 proposal settings (encryption algorithm, hash algorithm, authentication method, DH group, and lifetime) do not match. The administrator should compare the IKE properties on both gateways and ensure they are identical. This is the most common cause of this error.
- ✗
The VPN community is not configured to allow the specific encryption domain.
Why it's wrong here
If the encryption domain does not match, the error would typically be 'NO_PROPOSAL_CHOSEN' only if the proposal itself is mismatched. However, encryption domain issues usually result in different errors, such as 'INVALID_ID_INFORMATION' or 'NO_PROPOSAL_CHOSEN' in Phase 2. The error in Phase 1 specifically points to proposal mismatch. Encryption domain is checked later, so this is not the primary cause.
Visual reference
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Check Point exam blueprint
This CCSM practice question is part of Courseiva's free Check Point 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 CCSM exam.