@Amiguel Let me update my problem. Connection continued unstable. I've made several tests in the switchs, and finally turning OFF both IGMP and loopback prevention it is working for some days without...

@TP-Link Deco Hi, I have an unstable Ethernet connection between Decos P9. System was working fine with the configuration below: ISP Router(Bridge)->cable->DECO Main unit -> wifi -> DECO 2->cable->...

Yes, I can confirm it worked for me. (Deco P9)