Configuring OpenWrt modem

Installing and Using OpenWrt Network and Wireless Configuration
1

I have a Neatgear DM200 configured with Open Wrt and intend to use this as a basic ADSL modem. I plant to use a R7000P as the router.

the DM200 is running fine when I connect directly to my PC, but not when connected to the router.

I have the dm200 configured like this;

Capture
Capture921×409 19 KB

what else do I need to do?
the DM200 page says this;

The DM200 has a single Ethernet interface (eth0). You will need to bridge traffic to a VLAN-tagged interface (eg: eth0.2) to prevent your LAN from leaking out the DSL interface.
2

Check https://openwrt.ebilan.co.uk/viewtopic.php?f=7&t=266, while this guide talks about the BT Home Hub 5 Type, you can derive the same procedure for your device as well (same SOC).

Regarding your problem, I guess you'll have to adapt the VLAN tagging as needed by your ISP.