It looks like we are going to be forced into upgrading vagrant based on some HashiCorp deprecation activities. See:
I'm still digging around for the vagrant commit that fixes this in newer versions - I just upgraded to the latest and that fixed it.
Currently, if you don't have centos6 or ubuntu14 locally, you see something like the following:
$ vagrant up
Bringing machine 'node1' up with 'virtualbox' provider...
==> node1: Box 'centos/6' could not be found. Attempting to find and install...
node1: Box Provider: virtualbox
node1: Box Version: >= 0
The box 'centos/6' could not be found or
could not be accessed in the remote catalog. If this is a private
box on HashiCorp's Atlas, please verify you're logged in via
`vagrant login`. Also, please double-check the name. The expanded
URL and error message are shown below:
Error: The requested URL returned error: 404 Not Found