@ttimaizumi 

Hi, can I have a picture of your current network topology?

And were you trying to say, after adding a new Deco, the Deco that used be on Ethernet backhaul now turned to WiFi backhaul?

If yes, can you also mark out which Deco has changed to WiFi backhaul?

Thank you very much.

Wait for your reply.

Best regards.

  @ttimaizumi

Hi, Thanks for the update.

May I know the model number of the main router?

Could you please also try to connect study Deco M5 directly behind main bedroom P9 to see whether the Ethernet backhaul worked or not?

And please also replace the current Ethernet cable and switch to different Ethernet ports on the main router to see whether it made any difference.

Wait for your reply.

Best regards.

  @ttimaizumi 

Hi, Thanks for the update.

It seemed like Huawei HG8145V5 failed to forward the standard IEEE 1905.1 protocol that is used for Ethernet backhaul.

Have you set up any LAN isolation on the HG8145V5?

• You could connect two wired laptops behind HG8145V5 and try to ping each other to check the communication.

And if you have an additional network switch, the following layout would work as well:

HG8145V5--unmanaged switch---P9

                                               \----Deco M5

In case not, I will also follow up on your case by email to see whether there would be any other suggestions from engineers. 

Thank you very much.

Best regards.