Leopard: Activating ipfw at boot time

[Vittorio]

Perhaps I'm a bit OT, anyway .....
Having a long experience with freebsd and with its ipfw firewall, very  
flexible indeed, I would like to use the same ipfw.rules under mac os  
x 10.5.2 Leopard as I keep on using under freebsd deactivating the mac  
os x "automatic" firewall (I mean telling it to let all traffic in and  
out).
Now my set of rules work great if I launche them manually.

How can I tell leopard to execute the ipfw.rules script automagically  
at each boot?

Ciao
Vittorio