The subject of load balancing inbound nat connections to several boxes..
eg. 1 external IP that round robins traffic to 2 internal hosts...
Has been brought up quite a few times.. Now, I am a openbsd and linux
person, and my monowall development box is current;y down so I had no
way to look into this, However it seems to me that freebsd (ipf) allows
for the round-robin flag which allows you to setup 2 or more rules to
round robin inbound connections to various machines.. See Below from my
rdr ng0 0.0.0.0/0 port 110 -> 192.168.2.29 port 110 tcp round-robin
rdr ng0 0.0.0.0/0 port 110 -> 192.168.2.30 port 110 tcp round-robin
rdr ng0 0.0.0.0/0 port 110 -> 192.168.2.31 port 110 tcp round-robin
This seems to balance things out fairly well. In may case if you look at
my mrtg stats on the site below for pop3 it does a decient job of
balancing traffic between the servers.
Of course this does not take into consideration individual server load
of if the server is even up, But it should be an easy thing to implement
Just my .02