Thks Xiaofan. I was talking to the ASUS technical support, he advised me to do it wirelessly
All my rooms have active lan point. Initially I thought I can just connect the MBR Room lan point to AX55 then it should work automatically as Aimesh but he said might have conflict of IP address hence he said just create Aimesh wirelessly
He said its easier to just power up ax55 in the room and then use the app to configure? No need to connect lan point to AX55 etc.
In your case, yes you need extra hardware to use Ethernet backhaul. You can try the suggestion to use wireless backhaul to see if that is good enough for you or not. And depending on the wall, you may have to shift the RT-AX55 to the Bedroom 2.
Ethernet backhaul will have better wireless performance.
1) If you have two LAN ports next to each other in the RT-AX88U location (recommended LAN port configuration for BTO renovation), then you can use the following method.
1a) ONT -- DB box port x -- Living room LAN port 1 -- RT-AX88U as main router -- Living room LAN port 2 -- DB box patch panel LAN Port y
1b) DB box patch panel LAN port y -- dumb switch like TP-Link SG-105 -- rest of the patch panel LAN ports
1c) MBR LAN port -- RT-AX55
2) If you only have one LAN port in the RT-AX88U location (many BTO seems to be like this as the other LAN port may be far away), then you have to put another router in the DB box, for example, an RT-AX56U which will act as the main router.
2a) ONT -- RT-AX56U -- DB box patch panel LAN Ports
2b) Living room LAN port -- RT-AX88U in AP mode (the CPU power will be kind of wasted)
2c) MBR LAN port -- RT-AX55