During installation you might receive an message (see image) that stops the installation because of a network connection issue:
"Unhanded exception has occurred in your application. If you click Continue, the application will ignore this error and attempt to continue. If you click Quit, the application will close immediately.
A network-related or instance-specific error occurred while establishing a connection to SQL Server. The serve wa not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error 40 - Could not open a connection to SQL Server)."
To Troubleshoot this issue:
1. Make sure you are running the installer on one of your SharePoint servers.
2. Verify that your SQL Connection is working from the SharePoint server by using SQL Management studio (or something similar) to connect to your SQL server using the same credentials. If you don't have SQL Management Studio on your SharePoint server then you may use PowerShell to perform the verification. Here is an example
3. Check the causes of this issue in this article http://blogs.msdn.com/b/sql_protocols/archive/2007/03/31/named-pipes-provider-error-40-could-not-open-a-connection-to-sql-server.aspx