I took delivery of an ER8411 yesterday and started to set it up last night.

I managed to upgrade it to firmware 20231214 — apparently just moments before the release of 20240308.

I will likely upgrade to 20240308 tonight, but I don't have reason to believe that will make a difference for this issue.

I have not changed anything on the router (other than the admin password of course).

The two default WAN ports remain configured as Dynamic (which I take to mean DHCP).

I cannot get either port on the ER8411 to accept a DHCP response from a known-good TP-Link AC4000.

(I am connecting ER8411 to AC4000 merely to perform testing before deployment onto my ISP connection, which is 10G.)

A laptop will happily accept a DHCP response from the same AC4000. (It will also accept a DHCP response from ER8411.)

This router cannot be this badly broken. There must be something very dumb I am doing or have failed to do.

Any ideas welcome.