Got it figured out, thanks for the hint @terziyski . One of the RJ-45 connectors somehow lost one blade. I crimped a new one and got 1000 Mb/s ;)

@terziyski that was my approach. I will take it home and try to connect directly to router using short cat 5e cable. Either way it will be replaced with c64 unit too

@terziyski cool. So it was a right choice to upgrade to C64s around my property. Still have one old C6 v2 which is refusing to connect with 1000 Mb/s speed. Might be due to the distance

@terziyski Perfect. Thanks for the reply. I was also using RE315 but when it was in extender mode while plugged to C80 via Ethernet - it was creating issues with the network. Changing it to AP mode...

Hi, I build a simple network based on multiple TP-Link devices. My main router is Archer C80 which receives internet signal from my ISP. Then I have three Archer C64 units in satellite mode that are...