vagrantをupして起動させようとした時、下記のようなエラーが出る場合がある。

$ vagrant up
Bringing machine 'default' up with 'virtualbox' provider...
==> default: Box 'bento/centos-6.7' could not be found. Attempting to find and install...
    default: Box Provider: virtualbox
    default: Box Version: >= 0
==> default: Loading metadata for box 'bento/centos-6.7'
    default: URL: https://atlas.hashicorp.com/bento/centos-6.7
==> default: Adding box 'bento/centos-6.7' (v2.2.7) for provider: virtualbox
    default: Downloading: https://atlas.hashicorp.com/bento/boxes/centos-6.7/versions/2.2.7/providers/virtualbox.box
An error occurred while downloading the remote file. The error
message, if any, is reproduced below. Please fix this error and try
again.

SSL read: error:00000000:lib(0):func(0):reason(0), errno 54
$ vagrant up
Bringing machine 'default' up with 'virtualbox' provider...
==> default: Box 'bento/centos-6.7' could not be found. Attempting to find and install...
    default: Box Provider: virtualbox
    default: Box Version: >= 0
==> default: Loading metadata for box 'bento/centos-6.7'
    default: URL: https://atlas.hashicorp.com/bento/centos-6.7
==> default: Adding box 'bento/centos-6.7' (v2.2.7) for provider: virtualbox
    default: Downloading: https://atlas.hashicorp.com/bento/boxes/centos-6.7/versions/2.2.7/providers/virtualbox.box
==> default: Box download is resuming from prior download progress
An error occurred while downloading the remote file. The error
message, if any, is reproduced below. Please fix this error and try
again.

HTTP server doesn't seem to support byte ranges. Cannot resume.

特に、初回は起動に数時間かかったりするので、途中でPCが落ちたりすると不安定に。

解決方法

~/.vagrant.d/tmp
内のboxフォルダを削除し、再試行。
（tmpフォルダはその名の通り、一時的なファイルなので消してOK）
Linuxのtmpディレクトリに移動し、「rm」コマンドで消すなどすること。
これでいけるはず。