For download and install offline yum packages use the below commands. These commands are for those who want to use offline packages in system where there is no internet connectivity. I have tested these commands in CentOS 7 and its working very well.
Note: These commands are tested on CentOS 7.
For downloading all the packages from the system where internet connectivity available:
yum install --downloadonly --downloaddir='/path/to/directory' package-name
For installing all the packages to the system where there is no internet connectivity:
yum localinstall --disablerepo=* '/path/to/rpm-directory/*.rpm'