Install VirtualBox v5.0.26 from here: https://www.virtualbox.org/wiki/Download_Old_Builds_5_0
Install vagrant v1.8.4 from here: https://releases.hashicorp.com/vagrant/1.8.4/ (1.8.5 seems to be current, but there’s a documented bug around ssh auth).
Install vagrant-hostmanager plugin.
vagrant plugin install vagrant-hostmanager.
Clone dcos-vagrant.