'Test if the IP string is a hostmask (rather than a netmask).
Args:
ip_str: A string, the potential hostmask.
Returns:
A boolean, True if the IP string is a hostmask.'

def _is_hostmask(self, ip_str):

    bits = ip_str.split('.')
    try:
        parts = [int(x) for x in bits if (int(x) in self._valid_mask_octets)]
    except ValueError:
        return False
    if (len(parts) != len(bits)):
        return False
    if (parts[0] < parts[(-1)]):
        return True
    return False
