Bringing machine 'default' up with 'virtualbox' provider...
==> default: Box 'bento/centos-6.8' could not be found. Attempting to find and install...
default: Box Provider: virtualbox
default: Box Version: >= 0
The box 'bento/centos-6.8' could not be found or
could not be accessed in the remote catalog. If this is a private
box on HashiCorp's Vagrant Cloud, please verify you're logged in via
`vagrant login`. Also, please double-check the name. The expanded
URL and error message are shown below:

URL: ["https://vagrantcloud.com/bento/centos-6.8"]
Error: Failed to connect to vagrantcloud.com port 443: Timed out
このようなエラーが出てきます