Internet Sharing on Mac via LAN [duplicate]

My system is Lion 10.7.x

My Internet Sharing is greyed out with:

Internet Sharing: Off

You cannot start Internet Sharing because you have not selected a port to share your connection.

How can I enable internet sharing?

The internet sharing panel is totally disabled, I can see the drop down but unable to select, I'm using a customized version from corp, they may disabled this function, since I have root permission, I might be able to restore it, do you know where to enable the panel?

I just find my screen shot is exactly the same as this question, not sure if its exactly the same case. Internet Sharing on Mac via LAN

I tried to add a com.apple.nat.plist to /Library/Preferences/SystemConfiguration and tried sudo /usr/libexec/InternetSharing -dDV, I got below in my /var/log/system.log There seems to be no error, but still unable to get it work.

Dec 10 04:24:37  com.apple.InternetSharing[3406]: port forwarding is allowed
Dec 10 04:24:37  com.apple.InternetSharing[3406]: published changes: success
Dec 10 04:24:38  com.apple.InternetSharing[3406]: store_changedDec 10 04:24:38  com.apple.InternetSharing[3406]: set state: silent, state RESET(1020)->ON(1023), reason NO_ERROR(0), errnum 45
Dec 10 04:24:38  com.apple.InternetSharing[3406]: prefs_changed
Dec 10 04:24:38  com.apple.InternetSharing[3406]: published changes: success

Solution 1:

You need to select which networking the connection is to e share on. This is selecting at least one from the list in the bottom right hand of the preference pane.

e.g. to share your ethernet connection over wifi and firewore example share