Why Login failed for user 'Domainname\AppserverName'." If this type of user is added in the SQL Server Security section but has a different functional username configured within SQL, the error persists

Question

On the client’s network, the application server and database server are hosted on distinct machines (different servers). When accessing the database via an API developed using .NET Core 8, we encounter the following error:

Login failed for user 'Domainname\AppserverName'."

Here, ‘AppserverName’ represents the actual computer name of the application server. Additionally, to access the database, a connection string is created within the API layer.

 

We would like clarification on the following two points:

1. Scenario 1: When this type of user is not explicitly added to the SQL Server Security section for Windows Authentication, the above error is encountered.

Q: Why is this user required for authentication?

1. Scenario 2: If this type of user is added in the SQL Server Security section but has a different functional username configured within SQL, the error persists.

Q: What steps can we take to resolve this issue in such a scenario?

 

It may also be noted that our applications (on ASP .Net 4.6.2) are working and connecting on this environment; however, the .Net Core 8 application is facing above issues.

Answer 1

the error means the application is trying to connect to sqlserver using a trusted connection. for trusted connections the app pool account is used. but your app poo is using a local account, not a domain account. change the app pool account to a domain user that has access to the sqlserver.

note: you might check the app pool account for your working applications. also check their connect string to see if they used trusted or sql standard security.