public static byte[] getMCastMacAddress(byte[] targetIp) {
        checkArgument(targetIp.length == Ip6Address.BYTE_LENGTH);
        return new byte[] {
                0x33, 0x33,
                targetIp[targetIp.length - 4],
                targetIp[targetIp.length - 3],
                targetIp[targetIp.length - 2],
                targetIp[targetIp.length - 1],
        };
    }
@Test
    public void testMulticastAddress() {
        assertArrayEquals(MULTICAST_ADDRESS, getMCastMacAddress(DESTINATION_ADDRESS));
    }