C:\Users\Administrator\Vagrant\centos7>vagrant up
Bringing machine 'default' up with 'virtualbox' provider...
==> default: Box 'centos/7' could not be found. Attempting to find and install...
default: Box Provider: virtualbox
default: Box Version: >= 0
==> default: Loading metadata for box 'centos/7'
default: URL: https://vagrantcloud.com/centos/7
==> default: Adding box 'centos/7' (v2004.01) for provider: virtualbox
default: Downloading: https://vagrantcloud.com/centos/boxes/7/versions/2004.01/providers/virtualbox.box
Download redirected to host: cloud.centos.org
default:
An error occurred while downloading the remote file. The error
message, if any, is reproduced below. Please fix this error and try
again.

解决了吗，我也遇到这个问题了