Have you ever seen such a error which is "Failed to connect to the host via ssh." on your terminal when connecting a host via ssh. It should be happened if known_hosts file is taken a wrong identified keys belonging to the host.
$ ssh firstname.lastname@example.org Failed to connect to the host via ssh.
To clear the problem you may take away the identified keys with ssh-keygen command.
$ man ssh-keygen ... -R hostname Removes all keys belonging to hostname from a known_hosts file. This option is useful to delete hashed hosts (see the -H option above). ...
Use f option to specify a known_hosts files.
$ ssh-keygen -f ~/.ssh/known_hosts -R foobar.com # No more # rm -f ~/.ssh/known_hosts
That's it! :)