Hi,
perhaps this questions also solves another forum qestion (
http://forum.m0n0.ch/index.php/topic,1261.0.html).
See the attached network diagram. The problem is that even m0n0wall cant ping (via webGui) the attached LAN devices. But the LAN devices can connect to websites via WAN IF without problems via M0n0wall. Crazy.
All devices are attached with default CAT5 cables. See below the diagram.