How to troubleshoot the message "no proposal chosen" when it appeares in event logs?

Zyxel_Emily

Question:
How to troubleshoot the message "no proposal chosen" when it appeares in event logs?

Answer:
Site-to-Site VPN (Both sites are Nebula firewalls)
On nebula, there is no configuration for phase 1 and phase 2 proposal in Site-to-Site VPN. You can check phase 1 and phase 2 proposal using command via SSH.
[ATP/FLEX] How to check the phase 1 and phase 2 proporal of Site-to-Site VPN?

Site-to-Site VPN (Non-Nebula VPN peers)
Click IPSec policy > Default. Verify Phase 1 and Phase 2 Settings. Ensure both sides use the same encryption, hash algorithms, Diffie-Hellman group for key exchange and PFS settings.

Remote access VPN
Go to ADVANCED OPTIONS > Policy > Default. Verify Phase 1 and Phase 2 Settings. Ensure the VPN client supports the encryption, hash algorithms, Diffie-Hellman group for key exchange and PFS settings.