I have a cable internet Box in use, which is configurated in Bridge Mode.
So if I connect my PC direkt to the Cable box I get an IP and internet.
If I connect my FritzBox to the Cable box I get an IP and internet in the FritzBox.
-> I configure that the FritzBox has to geht Inet from LAN1.
If I conncet my Openwrt- Router (ubiquiti-er-x) I didn't geht an IP or Internet.
-> I configure DHCP and DHCPv6 which should be right,I think?
The cabeling is right, as I see it in Luci.
Do you have any which mistake I did. how can I diag the Problem?
Have you tried rebooting both the modem and the openwrt-router at the same time. DOCSIS, as far as I remember, requires modems to keep a list of MACs it allows DHCP for that often is willing to accept new MACs only shortly after booting up the modem, so the new device should request DHCP addresses inside this small time window to be provisioned (I belief that this still is the case for "bridge"-mode). You could also try to clone the FritzBox's wan MAC address into the er-x's wan address (make sure that the FB actually works with the modem and can reach the internet, disconnect it, and attach the er-x with the already cloned MAC).
I have solved my problem...
The Solution was so crazy and easy...
My Internetprovider send a IP just one time after Power up the Cable Box. That means if the FB was first at the cable Box it get an IP. If I Connect the U-ER-X without reboot it didn't get an IP. Reboot the CableBox and connecting the ER-X first is the Solution...