I have been trying to get my Xbox 360 connected for the past two hours, and I finally got it working. Here is how I did it, and I will also explain the issue that gave me the most problems. I followed a bunch of different instructions from multiple websites, but none of them seemed to work. Some people have been able to get it working easily while others can't, and I think that has to do with particular setups. My setup consists of a cable modem, AirPort Express, mac pro, and Xbox 360. My cable modem is connected to my AirPort Express. My Mac Pro is connected wirelessly to my AirPort Express. My Xbox 360 is connected by ethernet cord to my Mac Pro. I will list what I did in steps. 1. I opened System Preferences. 2. In Sharing, I checked the Internet Sharing Box. 3. I selected Share your connection from AirPort to computers using ethernet. - At this point the Xbox 360 did not connect, so I went back and read more instructions. I discovered the next steps in the process. 4. I opened System Preferences. 5. In Network, I selected one of my ethernet ports. 6. I selected configure manually. 7. I entered 10.0.1.63 for IP Address (Just picked a random open IP address) 8. I entered 255.255.255.0 for Subnet Mask. - Now I returned to my Xbox 360. 9. I selected Configure Network. 10. I selected Basic Settings. 11. I entered 10.0.1.36 for IP Address in IP Settings (Just another random open IP address) 12. I entered 255.255.255.0 for Subnet Mask. 13. I entered 10.0.1.63 for Gateway (This IP address must match the IP address set in Network Preferences for the ethernet port on the Mac) 14. I entered 10.0.1.1 for Primary DNS Server in DNS Settings (The IP address of my AirPort Express) 15. I entered my ISP's DNS for Secondary DNS Server in DNS Settings (I use OpenDNS so it was 22.214.171.124) - This time the Xbox 360 only failed the DNS test. I wasn't sure what the problem was so I messed around with every configuration until I found one that worked. 16. I opened AirPort Utility (The application that administers the AirPort Express) 17. I selected the Internet preferences. 18. I selected the DHCP tab. 19. I changed the DHCP Beginning Address from 10.0 to 192.168. 20. I restarted my AirPort Express, and the router gave my computer a 192.168 address. 21. I left the 10.0.1.63 IP address for the ethernet port alone in Network Preferences. 22. I changed the Primary DNS Server Address on the Xbox 360 from 10.0.1.1 to 192.168.1.1 (The new IP Address of the AirPort Express after changing the DHCP preferences). 23. I left the Secondary DNS Server Address, and the IP Settings on the Xbox 360 alone also. - I ran the test again, and it passed. I am not sure why the Xbox 360 doesn't like 10.0 IP addresses. They seem to do fine in the IP Settings, but not for the DNS Settings. Hopefully this works for other people that are failing the DNS test. If you have any questions feel free to ask.