@GiantHogweed 

It's great to hear that it is working now.

Have you changed the MAC address in the MyProximus account to B0-A7-B9-3D-17-79 or is it still B0-A7-B9-3D-17-7A ?

Did you configure this option "Use Custom MAC Address = B0-A7-B9-3D-17-79" just now or was it already set like this before?
 

  @woozle                                                                                                                                                                                                                                                                                           I begin with modifying the address in the My Proximus account; I, then, connect the cable to the LAN 1 Bridged port, and it starts between half a minute.

             This address was already in the AX-11000 interface, I've modified nothing.

              I now just connect to my Synology NAS to test the ports transmission, and the test were OK, but this famous message saying I've two routers is always there; before the                    tests  fail systematically. I suppose it's an iinformation message meaning that the NAS will always detect two routers, with or without a bridged port, whatever we do?                        

GiantHogweed wrote

 

             This address was already in the AX-11000 interface, I've modified nothing.

 

  @GiantHogweed 

Ok, thanks.

That explains why it initially didn't work after you activated the "Bridged LAN Host" in MyProximus.

The setting "Use Custom MAC Address = B0-A7-B9-3D-17-79" overrides the router's WAN MAC Address that is displayed on the main screen of your AX11000.

Basically, even though the AX11000 shows "WAN MAC Address: B0-A7-B9-3D-17-7A" on its "Internet Status" screen, its actual WAN MAC Address is now "B0-A7-B9-3D-17-79".

I guess that "Use Custom MAC Address = B0-A7-B9-3D-17-79" must have been a leftover from a few months ago, when you tried to make it work with that b-box 3V+, because the default setting on a brand-new TP-Link router is "Use Default MAC Address".