problems with PF

[RJ45]

hello,
I configured PF for natting machines on my LAN
using FreeBSD as ADSL gateway.

I just write a simple rule
nat on tun0 from 172.16.16.0/24 to any -> (tun0)

but NAT does not work, packets are blocked.

ip forwarding is enabled

using ipfilter works and packets are natted succesfully with a simple rule
the same as before:

map tun0 172.16.16.0/24 -> tun0/32


I am using PF on OpenBSD since the first time it was released
so I Am sure it is not a problem of my configuration (After all more
than very simple)
using PF on FreeBSD I noticed simply packets are not NATted.
I have to say I am using it on sparc64 FreeBSD 5.2.1 on ultra 60.

anyone has some hints ?

maybe on i386 works who knows ?

thanks

Rick