This is just for curiosity reasons more than anything else.

We've just moved across Auckland (from one UFB address to another) and previously my IP was always in the 203.xxx range no matter how many times the router got rebooted.

Now every time the modem is rebooted it gives a new address. At the moment I'm 121.xxx but I've had 210, 203, 118, and maybe a 103 as well?

Why does it do that?