Connecting a Linksys Wireless Router to a Comcast Modem

I upgraded my wireless home network this weekend from an old Netgear 802.11b router to a shiny new Linksys WRT120N router sporting the latest 802.11n technology, and a much sleeker design.

The network speed difference is very noticeable and significantly faster on the newer router, and the units were on sale for only $39 at Fry's so it seemed like a steal of a deal... until I tried to install it.

I have Comcast internet at home with a standard-issue Motorola cable modem, and it turns out that Linksys routers don't naturally connect directly with these modems.

The Network Magic software that comes with Linksys routers failed on the first setup screen with an "Error 321", claiming it could not detect my ethernet network adapter. Apparently the Linksys routers require you to connect through a separate router that sits between the Comcast modem and the Linksys router (or at least that's what I found hidden somewhere in the documentation) - and in fact, it worked fine if I connected through my old Netgear router to the Comcast modem.