From: "Nikos Giannoulis" <ngiann at aegina dot net>

> I've been assigned from my Internet provider the subnet 212.xx.yy.224 / 27
> so usable IP range is 212.xx.yy.225 ~ 212.xx.yy.255
{snip}
> I connected
> monowall WAN i/f to ADSL router i/f
> monowall LAN i/f to my LAN switch
>
> mono WAN IP       = 212.xx.yy.226
> mono WAN Gateway  = 212.xx.yy.225
>
> mono LAN IP = 212.xx.yy.227 / 28

This is a simple routing error.  Your DSL gateway goes to send to a PC of 
yours on .228 and says "this is in my local subnet" and sends it out, not to 
the m0n0wall.  Start out with the m0n0wall doing NAT.  Make sure it works. 
Then you can do 1 to 1 nat with the additional IP addresses.  The only way 
to do "real routing" as opposed to NAT is to change the subnet mask of the 
LAN ip of you DSL gateway, and add a static route to your m0n0wall.

                        Lee