Access remote systems using ssh

Accessing to remote system as root:

example:
# ssh 192.168.122.230
or:
# ssh remotedomain.example.com
or
# ssh remotedomain

Accessing to remote system as a user::

example:
# ssh john@192.168.122.230
or:
# ssh remotedomain.example.com -l john
or
# ssh john@remotedomain.example.com