I have an AirPort Extreme (3rd generation) acting as the router in the house. Unlike the Actiontec router that it replaced, Windows 7 (but not XP) computers connected to the LAN in various ways, either by wired ethernet or wireless-N, cannot access the Internet through it. I can ping them from my Mac on the LAN, but they cannot ping anything on the Internet like 22.214.171.124 (Google DNS). It can't be a DNS issue. I've tried both DHCP and manual setup, mimicking the settings my Mac uses except with a different IP address. I'm no expert at networking, so I don't know what else could cause it. What's going on?
I've switched between this router and the Actiontec in the past. Whenever this router is in, Windows 7 can't connect. The moment I switch to the Actiontec, it works.