From Rick at work, but I thought it was generally useful. I might need it someday! Why not here?
“Had some trouble over this past weekend in setting up a wireless network at home. Perhaps the following tip can save you a few hours of frustration…
I have broadband access via Comcast (cable modem). I then picked up an AirPort Extreme base station (Apple) that provides 802.11n (with b/g compatiblity).
After several hours, I just could not get the thing to work. My Mac (wired directly to the base station’s ethernet port) would often be connected to the internet, but my iPhone wouldn’t be. Or, both devices would not connect at all. My Mac often grabbed an IP as if it was directly connected to the cable modem.
Much googling later, turned out that that I had to unplug my cable modem for several minutes for it to “forget” the original IP my computer grabbed. Once that occurred, the base station was able to pick up an appropriate IP and go into “shared IP mode”. Mac’s IP was then a proper 10.x.x.x address. Everything then worked to include both devices wired directly to the base station via Ethernet and devices connecting via the wireless network.”