Which firmware version your device has installed?
Did you try restarting your edgerouter after configuring RUT240 to operate in passthrough mode? device?
Is the port you connect to the edgerouter configured as DHCP client?
For monitoring, could you login to the router via SSH and execute the command:
Then restart your edgerouter, wait for it to boot up and connect ethernet cable from the router to edgerouter's port. The logs should show DHCP exchange along with MAC addresses of the interfaces. It would allow to confirm if configured MAC address of Edge router participating in the exchange is correct.
For a deeper inspection you may download TCP dump from Services -> Package manager page and enable monitoring for br-lan interface in System -> Administration -> Troubleshoot section. For a more tailored packet capture, I would suggest to enable packet capture on LAN interface specifically for DHCP protocol with the command:
- tcpdump -i br-lan port 67 or port 68 -w /tmp/capture.pcap
Then extract this file from the router using WinSCP and attach it by editing your question.
Could you also replicate your scenario and generate a troubleshoot file from RUT240? To do it, access router's WebUI, go to System -> Administration -> Troubleshoot page and download troubleshoot file from there.
The logs in the file might provide additional insight into the issue. Attach the file by editing your question.