Troubleshoot connectivity issues in SQL Server

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. Although this series of articles provides guidance, it may not effectively troubleshoot some specific scenarios.

Preparation

Before you start troubleshooting, check Recommended prerequisites and checklist for troubleshooting connectivity issues for logs that you should collect to assist with troubleshooting. There's also a list of quick actions to avoid common connectivity errors when working with SQL Server.

Common connectivity issues

Use the following list to navigate to the appropriate article page for detailed troubleshooting steps for your scenario:

• A network-related or instance-specific error occurred while establishing a connection to SQL Server

• Cannot generate SSPI context

• Login failed for user

  Covers the following Login errors:

  • "Login failed for user 'NT AUTHORITY\ANONYMOUS LOGON'"
  • "Login failed for user '(null)'"
  • "Login failed for user (empty)"
  • "Login failed for user '<username>'"
  • "Login failed for user '<domain>\<username>'"

• Timeout expired. The timeout period elapsed prior to completion of the operation or the server is not responding

• An existing connection was forcibly closed by the remote host

• Token-based server access validation failed with an infrastructure error. Check for previous errors

• The certificate chain was issued by an authority that is not trusted

Tools and methods that help you troubleshoot connectivity issues

The following articles provide details for various tools and procedures to troubleshoot different connectivity errors:

• Configure firewalls to work with SQL Server

  Describes how to configure Windows firewall for successful connections to instances.

• Test connections to SQL Server by using Universal Data Link (UDL) files

  Describes how to test connections between SQL Server and clients using UDL files.

• Use PortQryUI tool with SQL Server

  Describes how to use the PortQryUI tool (a graphical user interface (GUI) port scanner) to help troubleshoot connectivity issues.

• Check whether SQL Server is listening on dynamic or static ports

  Provides steps to check whether SQL Server is listening on dynamic or static ports.

• Use Kerberos Configuration Manager to fix SPN issues

  Describes how to use Kerberos Configuration Manager to fix Service Principal Name (SPN) issues.

See also

CSS SQL Connectivity Wiki