script question

Can you please help me write a shell script for the following

when I execute the following i should be getting this output as follows

I need to take this argument and split the 0xffffff00 as follow

ff ff ff 00 --> 255.255.255.0   (how do i convert this to this way)



 $ ./network.sh 172.16.200.123/0xffffff00 -hex
            0xac10c8ff