Need dd-wrt configuration to isolate wireless router from local LAN...

[Alex Hewitt]

This might not have an easy answer but I want to setup a wireless router 
inside an existing LAN. I want to be able to let users connect to the 
wireless router but not be able to access systems on the LAN that the 
wireless  router will be installed on. So the scenario is:

                      Internet Connection
                                  .
                                  .
                      Existing router (192.168.1.1)
                                  .
                                  .
                       Wireless router (192.168.2.1 or any private network)

A user connecting to the wireless router would get an address such as 
192.168.2.100 and they could ping or otherwise see machines on the 
192.168.1.* network. I've got dd-wrt v2.4 micro edition running on a 
WRT54G V5 wireless router. The main router is a LinkSys RV042 model.  Is 
there a simple way to stop users connected on the wireless router from 
accessing systems on the main LAN? One way to achieve this would be to 
add a switch between the ISP's equipment and the RV042 but I'd like to 
make sure that any wireless connections couldn't chew up too much bandwidth.

-Alex