HOWTO: Hookup two wireless routers
I have an Apple Airport Extreme wireless router. Because I have an iPhone (it can't connect via 802.11n), I had to have my Airport Radio Mode set to "802.11n (802.11b/g compatible)", which means when the iPhone was connected (and maybe at other times) the Airport was broadcasting at the slower b/g protocol speeds. Well, I also have a spare Linksys WRT54G v2.0 wireless router. So, I flashed it with dd-wrt firmware, and following these instructions I've configured the Linksys as a Wireless Access Point (WAP) and connected an ethernet cable from one of its LAN ports to a LAN port on the Airport (serving as the "main router"). I now have a 802.11g router (Linksys) for my iPhone to connect to, and my Airport's Radio Mode is now set to "802.11n (5 GHz)" for my Macbook Pro and Macbook to connect to at their fastest speeds. Goodness.