Below is the error I receive when trying to connect to database engine using ssms and alias.

A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: TCP Provider, error: 0 - No such host is known.) (Microsoft SQL Server, Error: 11001)

I have configured both 32 and 64bit alias in configuration manager have enable tcp and named pipes for remote connections have ticked box allow remote connections.

Have specified port 1433 in protocols for server in configuration manager for all ip versions.

Error 11001 occurs  because either the client cannot resolve the name of the server or the name of the server is incorrect.

Check the link

This error belongs  for either Named Pipes connections or TCP/IP connections.

https://www.mssqltips.com/sqlservertip/2340/resolving-could-not-open-a-connection-to-sql-server-errors/

Thanks for the replies

I can connect using management studio if I specify server name/instance name so shared memory works. if I use

tcp:server name/instance name to force a tcp connection then I get the error msg. below is
Screenshots of 32 and 64 bit client protocols with tcp enabled, then server network configuration showing tcp enabled and screenshot of tcp ip properties address and port are configured correctly.

I cannot connect using ip address i.e 127.13.xx.xx/instance.

• Edited by ghw123 10 hours 11 minutes ago

This would seem to be the problem...

The SQL Server Network Interface library could not register the Service Principal Name (SPN) [ MSSQLSvc/xxxx.xxxx.local:1433 ] for the SQL Server service. Windows return code: 0x200b, state: 15. Failure to register a SPN might cause integrated authentication to use NTLM instead of Kerberos. This is an informational message. Further action is only required if Kerberos authentication is required by authentication policies and if the SPN has not been manually registered.

• Marked as answer by ghw123 8 hours 32 minutes ago

IF SPN registration is the issue, then you should see the same on error log. If thats the case then you could register the same

https://msdn.microsoft.com/en-us/library/ms191153.aspx?f=255&MSPPError=-2147217396

Can you show us the alias configurations? Did you try both SSMS and SQLCMD?