Preparing for installation
Before installing the SQL Server, complete the following tasks on the computer where you plan to install the server:
Install .NET Framework 3.5, which is required by SQL Server 2012. By default, .NET Framework 3.5 is not installed on Windows Server 2008 R2.
Turn off the Windows firewall to open TCP port 1443. By default, Microsoft Windows enables the Windows firewall, which closes port 1443 to prevent Internet computers from connecting to a default instance of the SQL Server.