First off, I've used TomatoUSB for 5 years with my Asus RT-N16 and had excellent service and reliability out of it. Thanks to the authors.
I've recently upgraded my main router to a newer router and have set my RT-N16 up in the basement to act as a wired switch to the devices down there, replacing a truly ancient hub.
I turned off DHCP, disabled the WAN section, set my RT-N16 to a fixed IP address outside the DHCP pool of my new router and plugged a device and the upstream wire to LAN ports on the devices and all worked well. Yay!
However, I have noticed in this configuration while I can ping the router-turned-switch, I can no longer access its configuration webpage. Should I wish to turn it back into a router, how would I access that?