Install VirtualBox
Users of Oracle Linux 5, 6 and 7 can use the public yum repository and enable the el5_addons (OEL5), the ol6_addons (OL6) or the ol7_addons (OL7). If a public-yum repo file already exists in /etc/yum.repos.d, do not overwrite it but just enable the addons! After that, do
yum install VirtualBox-5.1
See following page for more detailes: https://www.virtualbox.org/wiki/Linux_Downloads
Check and Configure the Host-only Network Configuration
If you already had VirtualBox installed, check that you have a Host-only network configured on the host. If this is a fresh install of VirtualBox, check that the Host-only network adapter is configured as below.
Use the Oracle VM VirtualBox Manager GUI, Select File --> Preferences, then in the VirtualBox - Settings window, select Network. In the Network pane, select the Host-only Networks tab and check you have an entry named vboxnet0. If not, click the add host-only network button to add it. Make sure, that you defined following ip address subnet to it: 192.168.56.1
If you already have one Host-only Network configuration in the Virtual Box settings which you cannot change, please create a new one eg. vboxnet1 with subnetwork 192.168.56.1. You will afterwards have to change the machine_setup script appropriatelly.