def int_to_mask(mask_int):
    """ Convert int to mask
        Args:
            mask_int ('int'): prefix length is convert to mask      
        Returns:
            mask value
    """
    bin_arr = ["0" for i in range(32)]
    for i in range(int(mask_int)):
        bin_arr[i] = "1"
    tmpmask = ["".join(bin_arr[i * 8 : i * 8 + 8]) for i in range(4)]
    tmpmask = [str(int(tmpstr, 2)) for tmpstr in tmpmask]
    return ".".join(tmpmask)