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| FWP_E_INVALID_CIPHER_TRANSFORM | FWP_E_INVALID_TRANSFORM_COMBINATION |
FWP_E_INCOMPATIBLE_CIPHER_TRANSFORM
FWP_E_INCOMPATIBLE_CIPHER_TRANSFORM means the cipher transform may be valid by itself, but it cannot be used with the selected IPsec policy.
What to check for FWP_E_INCOMPATIBLE_CIPHER_TRANSFORM
- Check policy mode, authentication method, and the complete transform suite together.
- Align local policy with the cryptographic proposal expected by the peer.
- Review IKE events after correcting local policy to see whether the remaining failure is negotiation-related.
Microsoft: capture IPsec events with netsh wfp
Microsoft: IKEEXT service guidance
Diagnostic discriminator: Validate the negotiated cipher and transform pair as one IPsec proposal. Individually valid transforms can still be incompatible together, so changing unrelated filter conditions will not repair this combination.
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