I had created on e box inside vagrant. In the Vagrantfile, I had given the network as
Create a private network, which allows host-only access to the machine
Finally! This is years later but I couldn't find more current info. For me, the problem was that I not only had a private network defined, but also a forwarded port, and all that was working well. I then commented out the private_network, replaced it with public_network, and couldn't reach anything. Tried everything I found here and elsewhere, no go. It's only when I commented out the port forwarding that things started working again, without any of the manual bridging/dhcp configuration rigamarole suggested.