vagrant up時にThe box 'bento/centos-6.8' could not be foundと表示される


vagrant upしようとすると下記メッセージが出て失敗する。

$vagrant up
Bringing machine 'webserver' up with 'virtualbox' provider...
Bringing machine 'database' up with 'virtualbox' provider...
==> webserver: Box 'bento/centos-6.8' could not be found. Attempting to find and install...
    webserver: Box Provider: virtualbox
    webserver: 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 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:

URL: [""]
Error: The requested URL returned error: 404 Not Found にリダイレクトされたので表示されているURLが古いっぽい。



$vagrant --version
Vagrant 1.9.3


$vagrant --version
Vagrant 2.1.2