Vagrant (Virtualbox) host-only multiple node networking issue
The problem is that the interface has to be set to promiscuous mode through Vagrant, doing it inside the guest operating systems isn't enough.
For example, if you add two NICs, and the last NIC you define is the one that will be bridged to the VMs, your Vagrantfile should contain something like:
compute1_config.vm.customize ["modifyvm", :id, "--nicpromisc3", "allow-all"]