Share ethernet connected mac to xbox via airport

hey, I think my problem is opposite from everyone else. I'm trying to use the internet i have on my mac, that i am getting from an ethernet cable. To share it to my xbox wirelessly. i have the mac turned on to share to devices using airport. my iphone connects fine. but i can not get my xbox built in wireless adapter to connect to xbox live. if you have any info or know where i can look please help

Thanks
-will