■環境
centos7.0

■エラーメッセージ
・vagrant up時

Bringing machine 'default' up with 'virtualbox' provider...
==> default: Checking if box 'chef/centos-7.0' is up to date...
==> default: There was a problem while downloading the metadata for your box
==> default: to check for updates. This is not an error, since it is usually due
==> default: to temporary network problems. This is just a warning. The problem
==> default: encountered was:
==> default:
==> default: The requested URL returned error: 404 Not Found
==> default:
==> default: If you want to check for box updates, verify your network connection
==> default: is valid and try again.
==> default: Clearing any previously set forwarded ports...
==> default: Clearing any previously set network interfaces...
==> default: Preparing network interfaces based on configuration...
    default: Adapter 1: nat
    default: Adapter 2: hostonly
==> default: Forwarding ports...
    default: 8000 => 12345 (adapter 1)
    default: 22 => 2222 (adapter 1)
==> default: Booting VM...
==> default: Waiting for machine to boot. This may take a few minutes...
    default: SSH address: 127.0.0.1:2222
    default: SSH username: vagrant
    default: SSH auth method: private key
    default: Warning: Connection timeout. Retrying...
    default: Warning: Connection timeout. Retrying...
    default: Warning: Connection timeout. Retrying...

・vagrant ssh時

ssh_exchange_identification: Connection closed by remote host

■hosts.allow

ALL : 127.0.0.1
sshd : ALL

known_hostsは削除済みです。作業しているなかで突然このような状態になりました。
解決策をご教示いただけませんでしょうか。

CentOS7はvirtualBoxの中に立ち上げたゲストOSです。

---

ssh -vvv -p 2222 -i ~/.vagrant.d/insecure_private_key -l vagrant 127.0.0.1
を実行したところ、下記のメッセージが出ました。
どのように対処すればよいでしょうか？

OpenSSH_6.9p1, LibreSSL 2.1.8
debug1: Reading configuration data /Users/mae/.ssh/config
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 21: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to 127.0.0.1 [127.0.0.1] port 2222.
debug1: Connection established.
debug1: key_load_public: No such file or directory
debug1: identity file /Users/mae/.vagrant.d/insecure_private_key type -1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/mae/.vagrant.d/insecure_private_key-cert type -1
debug1: identity file /Users/mae/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /Users/mae/.ssh/id_rsa-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_6.9
ssh_exchange_identification: Connection closed by remote host