During the installation of SCCM 2012, we have to specify how the pre-requisite files are downloaded. There are two options
1.Download the files at the time of installation if there is internet connectivity to SCCM server.
2.Pre-download the files when there is no internet connectivity.
How to pre-download the files is explained below.
1.Open the installation media of SCCM 2012 and browse to the SMSSETUP\BIN\X64 directory.
2.Search for a file named “ SetupDL.exe”
3.Open a command prompt with administrative privileges on any machine that has internet connectivity.
4.Run the setupdl.exe and specify the download location.