Does network monitoring work if our computers run different operating systems?
Yes. A sensor on a mirror port sees the traffic of every device on the segment, whatever operating system it runs, because it watches the network rather than the computer. That covers office PCs, Macs, Linux servers, phones, printers and machines in one place. The operating system matters only for the device where the sensor itself is installed. For NetSenX, the agent runs on Linux and macOS, so the sensor host should be one of those; the devices it watches can be anything. If you want to watch specific machines directly instead of through a mirror port, those machines need to run Linux or macOS. Endpoint protection on each computer remains a separate need, specific to each operating system.