Internet Sharing?

I know the steps for internet sharing airport card's internet access to another computer via ethernet cable, but how do i set it up to share it with a router via ethernet cable?

 

Well happy to say, i can answer my own question. i stumbled onto the answer by playing around.

so for those doing a search and finding this post, here's the answer; instead of connecting the ethernet cable to the modem port on your router. connect it to one of the terminal ports like you would for normal operation.

and of course don't forget to setup your internet sharing under the sharing pref plane in system settings. you must choose the connections BEFORE you start internet sharing, or you won't be able to make the changes as the box will be greyed out. hope this will be helpful to someone in the future. !