I've been using m0n0wall for some time and I've just realized that it
cannot create inbound NAT rules for different internal IP's for the
same external port(s), dependent upon the source address.
This limitation was touched upon here, but not fully explained:
I wanted to see about implementing this functionality, but I've looked
at the man pages for ipnat and as far as I can tell there is no way to
do this because ipnat does not take source address as an
argument/option when using the rdr command. Can someone verify if this
is the case? My low-level fw/NAT/routing experience is rooted in Linux
and Cisco IOS so I am a little unsure when it comes to FreeBSD.