Hello Sommus, Thank you for your answer. Yes, it is right. Finally I gave back the switch and took a router. All works well now

My first post here, so hello to everybody, and TIA for any help! I just bought a TP-link TL-SG105 switch So, I plugged it to my Arris CM820 (I tried port 1, 4 and WAN) Then I have connected my two...