I have 2 types of clients. All "log in" over pppoe, but...

Some of them have public IP addresses.... some are over NAT and have private IP addresses.

I want this scenario:

1. Client connecting over pppoe, get public IP. That's all. He have internet
2. Client connecting over pppoe, get private IP. He try to "surf" and he is redirected to another "site" and get message (for example: you have to pay).