Database Connection from RedHat Linux CentOS 8 RStudio Server to MS SQL Server Named Specific Instance

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Hi Community,

I am trying to establish connection to MS SQL server Database Specific Names Instance from RedHat Linux CentOs 8 RStudio Server using Windows Authentication. The issue I am facing here is Unless I Have Access to Default Instance, I Am Unable to Connect to Specific Named Instance.

**We are using Kerberos Token and AD System to use Windows Authentication"

MS SQL Server:
Default Instance: DefaultInstance
Named Instance: NamedInstance

If I have Access on\DefaultInstance and\NamedInstance then, below code works

                           driver = "ODBC Driver 17 for SQL Server",
                           server = "\NamedInstance",
                           port = "1433"
                           trusted_connection = "yes")

If the Access to\DefaultInstance is revoked, the above code throws error nanodbc/nanodbc.cpp:983: 00000: [Microsoft][ODBC Driver 17 for SQL Server][SQL Server]Login failed for user XXXXXX. [Microsoft][ODBC Driver 17 for SQL Server]Invalid connection string attribute

odbc 1.2.2
DBI 1.1.0
R Version 3.6.0

Is that a limitation to have access on default instance to access named instance on the same server? If not is there any other argument that I need to pass to connect directly to named instance even when I don’t have access on default instance?

Any help is really appreciated. Thank you in advance.