CCSM Advanced VPN Troubleshooting Practice Question
Exhibit
IKE_DEBUG: [VPN] Proposal mismatch: Proposed: AES256-SHA256-DH14, Configured: AES128-SHA1-DH2
Refer to the exhibit. An administrator sees this log entry while troubleshooting a site-to-site VPN. What is the most efficient way to resolve this error?
⚠ Common exam trap
Candidates often attempt to disable VPN encryption or change the gateway's global settings, rather than matching the specific proposal requirements of the peer defined in the VPN Community.
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
✓
Update the VPN Community settings to match the proposal sent by the peer.
This error clearly identifies a cryptographic mismatch between the peers. The peer is proposing high-security parameters (AES256, SHA256) while the local gateway is configured for lower standards (AES128, SHA1). The administrator must update the VPN Community settings to include the stronger proposals, ensuring compatibility while maintaining security standards. This is critical for preventing unauthorized connections while ensuring legitimate tunnels succeed without unnecessary downtime.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Force a VPN tunnel reset using the vpn tu command.
Why it's wrong here
The vpn tu command resets existing Security Associations but does not change the underlying cryptographic policy. If the configuration mismatch persists, the tunnel will fail to re-establish immediately, as the proposal conflict remains defined in the Security Gateway policy database.
- ✓
Update the VPN Community settings to match the proposal sent by the peer.
Why this is correct
VPN Communities define the acceptable encryption and hash suites for all members. Since the log shows a proposal mismatch, the local community settings must be updated to include the peer's proposed settings, ensuring that the IKE proposal negotiation succeeds during the next attempt.
- ✗
Reinstall the security policy on the Management Server.
Why it's wrong here
Reinstalling the policy pushes the current configuration to the gateway. Since the current configuration contains an incompatible proposal set, re-pushing it without modifying the VPN Community settings will not resolve the mismatch error, leaving the site-to-site tunnel in a down state.
- ✗
Disable Perfect Forward Secrecy (PFS) in the tunnel configuration.
Why it's wrong here
PFS is a separate security feature that forces a new Diffie-Hellman exchange for each re-keying process. Disabling it does not solve a cryptographic proposal mismatch during the initial phase, as the basic algorithms must still agree before any tunnel parameters can be negotiated.
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.