Since SCCM 2012 or R2 requires installation of some prerequisites to be installed prior installing the SCCM; there are some shortcuts to do it, and not doing it while the SCCM gets installed.
Find/Locate for the SetupDL.EXE in your distribution or the download path you have stored in. Probably you will find it in the following folder:
Now issue the following command to download the files in a temporary directory:
Where the folder sccmrprereq directory is precreated. After issuing the command you will see that approximately 406 files will be downloaded, and it could be 384MB.
Download the following script and follow the instruction
SCCM 2012 R2 Prerequisite Downloader: http://gallery.technet.microsoft.com/scriptcenter/SCCM-2012-Prerequisites-1ce58746