redirect_port udp  192 . 168 . 1 . 6 : 50000   50000 
redirect_port tcp  192 . 168 . 1 . 6 : 50101   50101 

rl0: flags= 8843 <UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu  1500 
        options= 8 <VLAN_MTU>
        inet  192 . 168 . 1 . 99  netmask 0xffffff00 broadcast  192 . 168 . 1 . 255 
        ether  00 :e0:4c:5d:d0:ee
        media: Ethernet autoselect (100baseTX <full-duplex>)
        status: active
ed0: flags= 108843 <UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu  1500 
        inet  188 . 128 . 10 . 122  netmask 0xfffffffc broadcast  188 . 128 . 10 . 123 
        ether  00 : 00 :e8:5c: 94 :ed
plip0: flags= 108810 <POINTOPOINT,SIMPLEX,MULTICAST> mtu  1500 
lo0: flags= 8049 <UP,LOOPBACK,RUNNING,MULTICAST> mtu  16384 
        inet  127 . 0 . 0 . 1  netmask 0xff000000

fw="/sbin/ipfw"
inet="ed0"
local="rl0"
ipinet="188.128.10.122"
iploc="192.168.1.99"

${fw} -f flush
${fw} add pass all from any to any via lo0
${fw} add divert natd all from any to any via ${inet}
${fw} add pass ip from any to any via ${local}
#${fw} add pass all from any to any via ${inet}
${fw} add pass tcp from any to ${ipinet}  50101  in
${fw} add pass udp from any to ${ipinet}  50000  in
${fw} add pass all from any to any via ${inet} out

interface ed0
#use_sockets yes
#same_ports yes
redirect_port udp  192 . 168 . 1 . 6 : 50000   50000 
redirect_port tcp  192 . 168 . 1 . 6 : 50101   50101 
log yes

 6318   p0  R+      0 : 00 . 00  grep natd

natd_enable="NO"
natd_flags="-f /etc/natd.conf"

   Так было
   +---------------------------+
   |WinXP+Kerio                |
   |         Обработчик        |
   |                           |         +-----------+
<->| 78 . 108 . 69 . 250               |  +---+  | Database  |
<->| 188 . 128 . 10 . 122    192 . 168 . 1 . 6 |->|HUB|->| 192 . 168 . 1 . 7 |
   +---------------------------+  +---+  +-----------+

   Так теперь
   +---------------------------+
   |WinXP+Kerio                |
   |Обработчик                 |
   |                           |         +-----------+
<->| 78 . 108 . 69 . 250               |  +---+  | Database  |
   |                 192 . 168 . 1 . 6 |->|HUB|->| 192 . 168 . 1 . 7 |
   +---------------------------+  +---+  +-----------+
                                   ^ запрос на соединение
   +---------------------------+   | передается на 1.6
   |FreeBSD                    |   |  1 . 6  его обрабатывает
<->| 188 . 128 . 10 . 122   192 . 168 . 1 . 99 |->-+ данные пишет на  1 . 7 
   +---------------------------+     а ответ дает на 1.99
                                     который его передает в инет

rinetd redirects TCP connections from one IP address and port to another.
rinetd is a single-process server which handles any number of connections to
the address/port pairs specified in the file /etc/rinetd.conf. Since rinetd
runs as a single process using nonblocking I/O, it is able to redirect a
large number of connections without a severe impact on the machine. This
makes it practical to run TCP services on machines inside an IP masquerading
firewall.
LIMITATIONS
     rinetd redirects TCP connections only. There is no support for UDP.
     rinetd only redirects protocols which use a single TCP socket.