unable to run playbook

Hi guys,
I am trying to run a playbook but that is not working for me. I am encountering by the same error again and again.
my ansible.cfg looks like:

[defaults]

some basic default values…

inventory = /etc/ansible/hosts
#library = /usr/share/my_modules/
remote_tmp = $HOME/.ansible/tmp
pattern = *
forks = 5
poll_interval = 15
sudo_user = root
ask_sudo_pass = True
#ask_pass = True
transport = ssh
#remote_port = 22
module_lang = C

and the error is :

SSH Error: ssh: Could not resolve hostname ControlMaster=auto: Name or service not known

That’s very strange to me. As when I am running another playbook it connects with all servers but when I only try to ping via ansible it gives me an error like this one.
Any one have any idea about it?