NAT question

[Mason Loring Bliss]

Hi all.

With iptables, I can say something like:

-t nat -A POSTROUTING -o eth0 -s 4.5.6.7/32 -d 0/0 -j SNAT --to-source 1.2.3.4
-t nat -A POSTROUTING -o eth0 -s 4.5.6.0/24 -d 0/0 -j SNAT --to-source 1.2.3.5
-t nat -A POSTROUTING -o eth0 -s 8.9.0.0/24 -d 0/0 -j SNAT --to-source 1.2.3.6

So, traffic going out from 4.5.6.7 goes into the world sourced from 1.2.3.4,
whereas the rest of 4.5.6/24 goes as 1.2.3.5, and all of 8.9.0/24 comes out
from 1.2.3.6.

I don't see how to do this with IPFW. I assume there's some way to do it with
the GENERIC kernel, so I'm assuming natd is deprecated, as it requires a
custom kernel, as far as I can see.

How do I accomplish this with IPFW? Or do I need to use PF for this? Or are
those independent of the NAT after all and I want to use something else? If
that's the case, does it require natd and a custom kernel, or is there
something that works with a GENERIC kernel? (This will be 10.1, FWIW.)

Thanks.

-- 
Love is a snowmobile racing across the tundra and then suddenly it
flips over, pinning you underneath. At night, the ice weasels come.