ansible SSH connection fail

mkdir /etc/ansible
cat > hosts
default ansible_ssh_host=127.0.0.1 ansible_ssh_port=2222 ansible_ssh_user=vagrant ansible_ssh_private_key_file=.vagrant/machines/default/virtualbox/private_key

Go to your playbook directory and run ansible all -m ping or ansible ping -m "server-group-name"

I had this issue, but it was for a different reason than was documented in other answers. My host that I was trying to deploy to was only available by going through a jump box. Originally, I thought that it was because Ansible wasn't recognizing my SSH config file, but it was. The solution for me was to make sure that the user that was present in the SSH config file matched the user in the Ansible playbook. That resolved the issue for me.

You need to change the ansible_ssh_pass as well or ssh key, for example I am using this in my inventory file:

192.168.33.100 ansible_ssh_pass=vagrant ansible_ssh_user=vagrant

After that I can connect to the remote host:

ansible all -i tests -m ping

With the following result:

192.168.33.100 | SUCCESS => {
    "changed": false,
    "ping": "pong"
}

Hope that help you.

EDIT: ansible_ssh_pass & ansible_ssh_user don't work in the latest version of Ansible. It has changed to ansible_user & ansible_pass