Background

DNN uses sql server express or sql server as it's backend database. Sometimes when attempting an install, there may be problems during the install wizard when it attempts to connect to the database and the user will see an issue such as:

Connection Error(s):

Index #: 0

Source: .Net SqlClient Data Provider

Class: 14

Number: 18456

Message: Sql login failed

This is perfectly fine and typically indicates that the user has mistyped a username, password or the server details, but sometimes all the credentials appear to be correct. This often means that the database is not accessible (e.g. it may not have the option to allow remote connections enabled, or perhaps a firewall is blocking access to necessary ports), but it can be annoying to determine the issue.

One suggestion is to remove DNN from the problem altogether and to test the connectivity another way. An easy way to do this is to utilise Microsoft universal data link files.

This blog talks you through the steps or else follow the suggested steps below:

• Create a file on the server called test.udl.
• Double-click the test.udl file.
• Click the Provider tab.
• Select Microsoft OLE DB Provider for SQL Server.
• Click Next.
• On the Connection tab, enter the connection information entered for the database connection:
  In the Select or enter a server name field, type the SQL server name in the following format: \,
  NOTE: If no named instance is in use, use the following format: ,
• Type the SQL database credentials.
• Click Test Connection.