Applies to: SQL Server Original KB number: 4009936
There are various causes for connectivity issues in SQL Server. This article series helps you troubleshoot the most common SQL Server connectivity issues and describes the tools and methods you can use for troubleshooting.
Note
If multiple SQL Server instances in your environment are impacted, or the issue is intermittent, it usually indicates Windows policy or networking issues.
You can also use the ODBC Data Sources (64-bit) or ODBC Data Sources (32-bit) Administrator to configure and test an ODBC connection to SQL Server. For more information, see ODBC Data Source Administrator DSN options.
Discover if a port is blocked with PortQryUI
You can use the PortQryUI tool (a graphical user interface (GUI) port scanner) to help troubleshoot connectivity issues. For more information, see Use PortQryUI tool with SQL Server.
Microsoft product support engineers frequently use SQLCheck, which is a tool they built to diagnose causes of connection failures. You can follow the instructions to download and collect the SQLCheck report for in-depth analysis.