I've found a way to sort of do what you're wanting it to do. I want the Westell to act as a pass-through too.
Login to »
192.168.200.1 with your username and password.
Click "My Network" at the top then "Network Connections", on the sidebar.
Click "New Connection"
Choose "Advanced Connection"
Click Next
Choose "Network Bridging"
Click Next
Choose "Configure Existing Bridge (Recommended)"
Click Next
Uncheck "Wireless 802.11g Access Point"
Check "WAN VDSL" and "Ethernet Switch"
Click Next
Check "Edit the Connection"
Click Finish
This is a *huge* security risk, however, and it exposes your web interface on whatever IP is assigned to your WAN VDSL connection. It does give an external IP to whatever is connected via the 4 port switch on the back though, which is what you and I are both going for.
Ideally, you don't want an IP assigned to the WAN VDSL, and only to whatever is connected to the Ethernet. Any insight on how to do that? There's access to the raw config file of this modem/router, but the tech that did the installation only left me the hardware. He didn't leave any ethernet cables, and took both the box the Westell came in, and the manual. If I had the manual I could probably figure it out.
Also, I've emailed Westell and requested that the manual be emailed to me. So if/when they do, I'll be sure to post it here.