need more info here friend!
you have adsl? cable? other.....
modem is authenticating for you?
ethernet connection you talk about is to modem switch other.....
i think you are bordering on needing third party onsite assistance or read some guides to study a bit more on home networking and config.
it will help to break issue down into two parts (or more)
1. Home network (ips, connections etc.)
2. ISP connection (auth, ips, settings etc.)
GIve more info or go do some study ( i mean this in a polite way)