I just got this working. The key for me was to first hook the GS from its LAN port directly to my laptop so I could get into the web interface at the 102. IP address and then turn on the setting to allow configuration over the WAN port (this is off by default). Then, when plugged in downstream of the router, I use the WAN port on the GS. Then, in the Airport Utility (v. 5, not the newest v. 6) I was able to find the device in the DHCP clients list, get its MAC address, and reserve a static IP address on my local network. I had to follow the complete restart procedure in the order modem->router->GS, then everything seems to be working fine. I have not had to do any port forwarding.