【正文】 of NetLibraries must be active on the client puter and the server puter to support the work protocol that you want to use. For example, if you want to enable a client application to municate with a specific instance of SQL Server across TCP/IP, the client TCP/IP Sockets NetLibrary () must be configured to connect to the server on the client puter. Likewise, the server TCP/IP Sockets NetLibrary () must listen on the server puter. In this scenario, the TCP/IP protocol stack must be installed on both the client puter and the server puter. After you install SQL Server 2021, you can configure the properties of the client NetLibraries by using Client Network Utility. You can configure the properties of the server NetLibraries by using Server Network Utility (). The server NetLibraries are installed during the installation of the server tools in SQL Servef Setup. However, some of the server NetLibraries may not be active. By default, SQL Server 2021 enables and listens on TCP/IP, named pipes, and Shared Memory. Therefore, for a client to connect to a server puter, the client must connect by using a client NetLibrary that matches one of the server NetLibraries that is currently being used by the instance of SQL Server. For additional information about SQL Server munication ponents and NetLibraries, see the following topics in SQL Server Books Online: . Communication Components . Client and Server NetLibraries . Managing Clients Troubleshoot connectivity issues Most of the connectivity issues that you may notice in SQL Server 2021 0ccur because of problems with TCP/IP, Windows authentication, or a bination of TCP/IP and Windows authentication. 8 Important Before you start to troubleshoot connectivity issues in SQL Server 2021, make sure that the MSSQLServer service is started on the puter that is running SQL Server. Verify your DNS settings The name resolution process in Domain Name System (DNS) is used to resolve the IP address to the name of the instance of SQL Server. If the name resolution process does not work correctly, the instance of SQL Server is not reachable, and you may receive one or more of the following error messages: SQL Server does not exist or access denied General Network Error Cannot Generate SSPI Context To verify that the name resolution process is resolving the correct server, you can ping the server by using the server name and the lP address of the server. To do so, follow these steps: 1. Click Start, and then click Run. 2. In the Run dialog box, type cmd in the Open box, and then click OK. 3. At the mand prompt, run the following mand: ping Server Name Note the lP address that is returned. 4. At the mand prompt, run the following mand (where IP address is the lP address that you noted in step 3): ping a IP address Verify that the mand resolves to the correct server name. If either of the specified mands are not successful, time out, or do not return the correct values, the DNS lookup is not working correctly or the problem occurs because of other working or routing issues. To see your current DNS settings, run the following mand at a mand prompt: ipconfig /all To work around this problem, add an entry for the server to the %systemroot%\system32\drivers\etc\hosts file on the clienr puter. You can also work around the problem by connecting to the server by using the Named Pipes Netlibrary. Verify the enabled protocols and aliases Connectivity problems may occur if the alias on the client puter is set incorrectly. You can view the aliases by using Client Network Utility. To do so, follow these steps: l. Start Client Network Utility. If the SQL Server client tools are installed on the puter that is running the client application, follow these steps to start Client Network Utility: a. Click Start, and then point to Programs. b. Point to Microsoft SQL Server, and then click Client Network Utility. If the SQL Server client tools are not installed on the clieni puter, follow these steps ro start Client Network Utility: a. Click Start, and then click Run. b. In the Run dialog box, type cliconfg in the Open box, and then click OK. 2. In the SQL Server Client Network Utility window, click the General tab, and ihen enable all the protocols that you want to use. Note You must at least enable the TCP/IP protocol and the named pipes protocol. 9 3. Click the Alias tab, and then verify the aliases that are configured for the instance of SQL Server. 4. Verify the properties of the aliases to make sure that the server name or IP address and the protocol are configured corfectly. You can create a new alias to test the connectivity by using the server name, the lP address, Of even by using a different protocoL Note Earlier versions of Microsoft Data Access Components (MDAC) have a different user interface for Client Network Utility. Therefore, if you do not see the options that are listed in this article, install a later version of MDAC on the puter that is running the client application. Verify that the instance of SQL Server listening correctly To verify that the instance of SQL Server is listening on named pipes, TCP/IP, or another protocol that you are using at the client application, open the current SQL Server error log file. The SQL Server error log file may contain entries that are similar to the following: 20211106 09:49: server SQL server listening on TCP, Shared Memory, Named Pipes. 20211 I 06 09:49:36. 1 7 server SQL server listening on I : 1433, 1 . I : 1433. If you analyze the entries in