Ethctl for lan port? Can't find interface name

[kakashisensei]

I have an ax3000 v2 that isn't supported by asusmerlin. I have an issue where one of the lan ports keeps dropping from 1gbps to 100mbps randomly. I have to either reboot the router or replug the cable. Its good for a while before it drops again. Not sure if its cable, switch, or passive poe injectors I use through this cable. The cable is in the wall so its too hard to replace. I have to use the passive poe injectors to power the switch in a remote location.

I want to try out this script a user posted to automatically renegotiate the port when it detects it at 100mbps. However I can't find the port / interface name for this lan port for use with ethctl. Eth0 is wan, eth1 looks like one or both of the wifi radios. Doesnt look like its eth2 or eth3. When I try to specify a port, I get ioctl SIOCGQUERYNUMPORTS error back or in the case of eth0 and eth1 it says there are no sub ports.

This is what I get with brctl. Ipconfig command not found. Even when I unplug and replug the cable, nothing shows in the system log.

AX3000_MAIN:/# brctl show
bridge name     bridge id               STP enabled     interfaces
br0             8000.08bfb852c258       no              eth0
                                                        eth1
                                                        eth2
                                                        eth3
                                                        wl0.4

Does anyone know how I can find out the lan port and change it with ethctl? Or is it even possible on official firmware? Thanks!