My actual modem is Scientific Atlanta DCP2100r2.
Problem : Since public IP depends on the MAC address (like any usual dhcp I think), the modem is not giving an IP to a network card behind a bridge.
This is my configuration DCP2100 -> linux bridge with openvz containers -> other linux server running in a container.
IMPORTANT : I only get 1 ip addres, so the linux brigde doesnt have any IP assined. When the router dont have the cable link, it gives 192.168.100.* range IPS, the container gets IPs like 192.168.100.23 but when its connected to internet it doesnt get any public IP to the containter. However the bridge will get the public IP.
So I think, that the modem knows which network card has the physical link and want to get public IP via that MAC address and no the containter network card. If its like this, I have no possible way to solve this problem?