ssh
  vagrant@127.0.0.1 -p 2222
  -o LogLevel=FATAL -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -o IdentitiesOnly=yes
  -i D:/dev/Utils/Virtualization/Vagrant/insecure_private_key
  
issues:
https://github.com/mitchellh/vagrant/issues/7610
    Authentication failure after inserting new key with Vagrant 1.8.5. [PATCH] #7610

    The fix is:
        https://github.com/mitchellh/vagrant/pull/7611

embedded\gems\gems\vagrant-1.8.5\plugins\guests\linux\cap\public_key.rb
plugins/guests/linux/cap/public_key.rb 

    remote_path = "/tmp/vagrant-remove-pubkey-#{Time.now.to_i}"
-          Tempfile.open("vagrant-bsd-remove-public-key") do |f|
+          Tempfile.open("vagrant-linux-remove-public-key") do |f|
...
                mv ~/.ssh/authorized_keys.tmp ~/.ssh/authorized_keys
+               chmod 0600 ~/.ssh/authorized_keys