SQL Server Native Client (SNAC) is not supported beyond SQL Server 2012. Avoid using SNAC in new development work, and plan to modify applications that currently use it. The Microsoft ODBC Driver for SQL Server provides native connectivity from Windows to Microsoft SQL Server and Microsoft Azure SQL Database.
When a connection is opened, SQL Server Native Client sets SQL_COPT_SS_MUTUALLY_AUTHENTICATED and SQL_COPT_SS_INTEGRATED_AUTHENTICATION_METHOD to the authentication method used to open the connection. For more information about SPNs, see Service Principal Names (SPNs) in Client Connections (ODBC).
For more information on using SQLConnect to connect to a Always On Availability Groups cluster, see SQL Server Native Client Support for High Availability, Disaster Recovery.