What does Windows error code 13874 (ERROR_IPSEC_IKE_INVALID_AUTH_ALG) mean?

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: The IKE peer proposed an invalid or unsupported authentication algorithm.

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ERROR_IPSEC_IKE_INVALID_ENCRYPT_ALG	ERROR_IPSEC_IKE_INVALID_SIG

ERROR_IPSEC_IKE_INVALID_AUTH_ALG

ERROR_IPSEC_IKE_INVALID_AUTH_ALG (0x00003632) The authentication/integrity algorithm offered in the IKE negotiation does not match the local policy or supported implementation. It is not solved by changing firewall ports; the peer proposals must be aligned.

What to check

Compare the integrity/authentication algorithms configured on both peers.
Check whether the connection uses a legacy template that no longer matches the current security baseline.
Use an IKE trace to identify the exact proposal rejected by Windows.

Get-NetIPsecMainModeRule

Microsoft: Get-NetIPsecMainModeRule

Microsoft: Netsh network tracing

Microsoft: IPsec/IKE system error codes

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