public static int getMaskBitByMask(String mask) {
		Integer maskBit = MaskBit.getMaskBit(mask);
		if (maskBit == null) {
			throw new IllegalArgumentException("Invalid netmask " + mask);
		}
		return maskBit;
	}
@Test
	public void getMaskBitByIllegalMaskTest() {
		assertThrows(IllegalArgumentException.class, () -> Ipv4Util.getMaskBitByMask("255.255.0.255"));
	}