I have used all of the 4 ports on my AT&T Uverse router. I added a TP-Link Mesh network. The base unIt had 2 Ethernet ports so I assumed I could move one of the devices to that and it would work. But my HP all-in-one printer had a fit apparently account DHCP IP addresses. So I bought a TP-Link 5 port gigabit switch. My WD NAS is not reading. My Mac mini is happy as a clam on the switch. How can you tell what can go through a switch and what insists on being on the router? Or am asking the wrong question?