RHEL 7.2 VMs are set up with the wrong network device
Submitted by Debarshi Ray
RHEL 7.2 VMs don't have broken networking in Boxes. This can be fixed by changing the network device to rtl8139 from virtio. I was told that this is due to missing virtio drivers on the guest.
(Thanks to Pavel Grunt and Victor Toso for helping me narrow this down.)
Interestingly, RHEL 7.3 VMs are also set up with virtio, but have functional networking (I guess due to the drivers being present), while RHEL 7.4 gets set up with rtl8139.