vagrant up でエラーが出たので、画面手順にそって操作してみた。

vagrant up
Bringing machine 'default' up with 'virtualbox' provider...
==> default: Checking if box 'centos/7' is up to date...
==> default: A newer version of the box 'centos/7' is available! You currently
==> default: have version '1603.01'. The latest is version '1606.01'. Run
==> default: `vagrant box update` to update.
==> default: Running provisioner: shell...

が表示されます。そのまま続行すると以下の様なエラーが出ました。

The guest machine entered an invalid state while waiting for it
to boot. Valid states are 'starting, running'. The machine is in the
'paused' state. Please verify everything is configured
properly and try again.

If the provider you're using has a GUI that comes with it,
it is often helpful to open that and watch the machine, since the
GUI often has more helpful error messages than Vagrant can retrieve.
For example, if you're using VirtualBox, run `vagrant up` while the
VirtualBox GUI is open.

The primary issue for this error is that the provider you're using
is not properly configured. This is very rarely a Vagrant issue.

ベースのイメージのバージョンが古いそうなので、指示に従ってコマンドを実行します。

vagrant box update

こんなエラーも出ていました

SSH authentication failed! This is typically caused by the public/private
keypair for the SSH user not being properly set on the guest VM. Please
verify that the guest VM is setup with the proper public key, and that
the private key path for Vagrant is setup properly as well.

http://qiita.com/cock1doodledoo/items/b32382776f76fb2d627c

に書いてある対応をすればいいようです。