That depends on the workload (e.g. how many are servers, how many are workstations). For example, arithmetically, fifteen sixteen-port switches are needed; one central into which fourteen others are attached, and then the two hundred workstations plug into those. This may not be the optimal arrangement for performance, however. If groups of systems share certain workloads, you'll want to isolate them to their own switch or switches, to keep their traffic from slowing down other systems.