What does Windows error code 1748 (RPC_S_UNKNOWN_AUTHN_LEVEL) mean?

 
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RPC_S_UNKNOWN_AUTHN_SERVICE RPC_S_INVALID_AUTH_IDENTITY

RPC_S_UNKNOWN_AUTHN_LEVEL

RPC_S_UNKNOWN_AUTHN_LEVEL means that the requested RPC authentication level is not recognized. Authentication level controls the protection applied to the call, such as connection authentication, integrity or packet privacy.

Why it matters

Choosing the wrong level can weaken security or make a valid deployment fail before the call reaches the server. The level must be compatible with both the authentication service and the intended transport.

What to check

  • Use the documented RPC_C_AUTHN_LEVEL_* constants.
  • Keep the requested level in configuration as a named value rather than an unexplained integer.
  • Confirm whether the server requires integrity or packet privacy for the interface being called.

Microsoft: Authentication-Level Constants · RpcBindingSetAuthInfo


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