@staticmethod
def calc_full_mask(cidr_mask):
    """
        Calculate the full subnet mask from the given CIDR mask.
        :param cidr_mask: CIDR mask bits
        :return: full notation subnet mask
        """
    cidr_bits = '1' * cidr_mask + '0' * (32 - cidr_mask)
    cidr_bits_arr = [str(int(cidr_bits[:8], 2)), str(int(cidr_bits[8:16], 2
        )), str(int(cidr_bits[16:24], 2)), str(int(cidr_bits[24:], 2))]
    return '.'.join(cidr_bits_arr)
