RPC_S_UNSUPPORTED_AUTHN_LEVEL - 1821 (0x71D)
The requested authentication level is not supported.
Updated: Feb 21, 2026
Technical Meaning
The RPC_S_UNSUPPORTED_AUTHN_LEVEL error indicates that the authentication level requested for a Remote Procedure Call (RPC) is not supported by the system or service.
Error Details
This error typically occurs when an application attempts to establish an RPC connection with a specified authentication level, and the remote endpoint does not support this level. The RPC_S_UNSUPPORTED_AUTHN_LEVEL error code is returned to inform the caller that the requested security context cannot be established.
Usage Context
This error can arise in various scenarios where RPC calls are made over a network or between processes. It is commonly encountered when dealing with authentication mechanisms such as Kerberos, NTLM, or other custom authentication protocols.
Developer Interpretation
Developers should interpret this error as an indication that the security context requested for the RPC call is not supported by the target service or endpoint. This could be due to several reasons, including mismatched security configurations, unsupported authentication levels, or misconfigured services.
Related Errors
RPC_S_ACCESS_DENIED(1794) - Indicates a permission issue rather than an unsupported authentication level.RPC_S_INVALID_AUTH_IDENTITY(2038) - Occurs when the authentication identity is invalid.RPC_S_NO_CONTEXT_AVAILABLE(1825) - Indicates that no security context could be established, possibly due to other issues such as network connectivity or service availability.
FAQ
Q: What does RPC_S_UNSUPPORTED_AUTHN_LEVEL mean?
A: It means the requested authentication level for an RPC call is not supported by the target endpoint.
Q: How can I resolve this error?
A: Ensure that both the client and server are configured to support the same authentication levels. Verify the security settings and configurations on both sides of the RPC connection.
Summary
The RPC_S_UNSUPPORTED_AUTHN_LEVEL error code is a specific indication that an unsupported authentication level was requested for an RPC call. Developers should focus on ensuring compatibility between client and server security configurations to resolve this issue.