Hi -
I have the WBMR-300 set up like so:
Internet <----> WBMR <-------> 192.168.1.X network
<--------> 192.168.1.2 [router] 192.168.2.1 <---> 192.168.2.X network
So two networks with an additional router separating the two. Anyone on either network can access the internet - but though all filtering is off hosts on the 192.168.1.X network cannot access hosts on the 192.168.2.X network and vice versa.
The [router]'s route table is set with itself as the default route for the 192.168.2.X network. The WBMR has a route for the 192.168.2.X network that points to the 192.168.1.2 address of the router. Evidently packets are routing properly in general as hosts can access external addresses. It looks like the WBMR is filtering out packets between the two networks though.