I have upgraded to the latest Vagrant v1.8.5 and now running Virtualbox 5.1 on Windows and I have noticed that when setting up a new vagrant instance (aka 'vagrant up'), It seems its keeps displaying over and over "Warning: Authentication failure. Retrying...". The Vagrant VM is a CentOS 7.2 (64bit) VM. Example: ==> default: Preparing network interfaces based on configuration... default: Adapter 1