I bought an AirPort Extreme Wireless router this weekend and hooked it up to my cable modem at home. I used the Airport Utility to set up the base station and create a wireless network. At first, I used DHCP to set up but got a yellow light and a message saying that the internet connection was not working. So I hook my MacBookPro directly to the cable modem ethernet port and got all the IP Address, Subnet Mask, Router and DNS information from my ISP, Cox Cables. After this, I connect the AE to the cable modem ethernet port and used the Airport Utility to set up the base station again. I chose manually set up this time with the IP address I got from ISP. I got it working without any problem and my MacBook Pro was able to detect to the AE. However, I still can't access the internet. The light on the AE itself is solid green, but there is no connectivity to the internet. Any help will be appreciated. I'm using Mac OSX v10.6.6.
Reset the Airport Extreme back to default settings and start over. You will also have to release the WAN IP on the modem by power cycling it. If the router doesn't grab an IP from the modem after the power cycle and reset, the chip that controls WAN functionality in the router is most likely bad.
There is a separate chip that controls the 3 LAN ports, and that's why they work okay when you plug into them. If this is not working then go to Apple menu and select System Preferences.
Choose Built-in Ethernet from the Show pop-up menu and go to PPPoE tab. Click the PPPoE Options button. Deselect the "Connect automatically when needed" option. Finally, click OK and apply the changes.