Modem/router, then cabled to a switch, then cabled to ALL other computers on the network. As an example in our fairly large government office, we had a 96 port ethernet switch (I think) which was connected to the network/internet on one side and about 80 ethernet cables to computers on the other side. Some of the cable runs were about 75 feet. I also set up a fairly small office which had a Verizon internet connection. Much like a home network, Verizon hooked directly to their modem/router inside the room, and from there, a couple computers connected directly to the router with ethernet cables. Then to make the next stretch, we added another cable from the same router/modem to a 16 port switch. From the switch was connected another 6 or 7 computers by ethernet cables which reached about 20 feet each.
The problem with the two switches and a router is that they may all be trying to issue IP address which causes a problem.
Hope this helps.
Grif