I have been evaluating CD-ROM release 1.1 of M0n0wall and have 
discovered by direct experience and by trolling the mailing list that 
while m0n0 correctly reflects Server NAT entries in the GUI, they don't 
seem to have any effect on the underlying operating system.  For example:
*** <http://m0n0.ch/wall/download.php?file=cdrom-1.1.iso>*
config.xml
-----------

<interfaces>
    <lan>
        <if>fxp0</if>
            <ipaddr>10.0.0.1</ipaddr>
            <subnet>24</subnet>
    </lan>
    <wan>
        <if>fxp1</if>
        <mtu/>
        <spoofmac/>
        <blockpriv/>
        <ipaddr>216.13.yyy.aaa</ipaddr>
        <subnet>29</subnet>
        <gateway>216.13.yyy.def</gateway>
    </wan>
</interfaces>

...
<servernat>
    <ipaddr>216.13.yyy.xxx</ipaddr>
    <descr>My Additional External Address</descr>
</servernat>


NOTE: the above <servernat> section looks reasonable and reflects what 
is seen in the GUI.
-----

ifconfig:
---------
fxp0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
    inet 10.0.0.1 netmask 0xffffff00 broadcast 10.0.0.255
    ether 00:02:b3:23:46:92
    media: Ethernet autoselect (100baseTX <full-duplex>)
    status: active
fxp1: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
    inet 216.13.yyy.aaa netmask 0xfffffff8 broadcast 216.13.yyy.abc
    ether 00:02:b3:23:46:93
    media: Ethernet autoselect (100baseTX <full-duplex>)
    status: active
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
    inet 127.0.0.1 netmask 0xff000000
ppp0: flags=8010<POINTOPOINT,MULTICAST> mtu 1500
sl0: flags=c010<POINTOPOINT,LINK2,MULTICAST> mtu 552
faith0: flags=8002<BROADCAST,MULTICAST> mtu 1500

NOTE: the server NAT is not reflected in the ifconfig listing from 
status.php
-----

Please let me know if I'm totally off base here.

Cheers,

Gordon.