1. Open the ODBC Data Source Administrator
  2. Select the System DSN tab
  3. Select the appropriate data source and click Configure
  4. Click Next, then Client Configuration
  5. Unmark the Dynamically determine port checkbox
  6. Enter the appropriate port number and click OK
  7. Unmark the Connect to SQL Server... checkbox and click Next
  8. Click Next, Finish to complete the changes

Note: Refer to How to find the port being used by SQL Server (BB134012) to determine the appropriate port to be used.