see here, the 'span' port support.
it's based on 1.2b9. i'll build a new image based on 1.2r when i have time.

http://m0n0.ch/wall/list/showmsg.php?id=191/47

note, the link for the image file should be
http://61.132.118.190/m0n0/1.2b9/generic-pc-1.2b9.0508262324.img

2005/10/13, Jonathan Marriott <jon at kiwiuk dot net>:
> Is it possible to turn an unused ethernet connection into a mirror of a used
> one using monowall? Much like some managed switches do. I have a WRAP 3-port
> board and have one spare that I'd like to use to see what is going on with my
> Internet connection and use things like ntop and ethereal on. Would simply
> bridging the ports do this?
>
> Thanks in advance,
> Jon
>
>
>