Cfrtjryk

I have a question which is puzzling me.

I have a couple of custom electronic devices (are identical, one is a master and the other is a slave) which implement only up to level 2 of the ISO/OSI layer, so they have only a (different) MAC address

If I connect one of them to my PC with a straight connection (e.g. the ethernet cable from the PC's ethernet card to the ethernet port of the device) , then I can connect and exchange data.

Now I have a more complex situation to handle.

The two devices are installed on a pole along with an IP camera. These 3 elements are named “sensor group”. I can have up to 7 sensor groups installed in a given area, for a specific task.

I need to connect those 7 sensor groups to a single local PC, in a room, with a specific SW (developed by myself) running.

I was thinking to use a network switch for each sensor group with a cabling (maybe fiber) to a network switch to which the PC is connected to. So, each sensor group, thanks to its local switch can communicate to the PC.

Now my point is: which kind of equipment I need to use (layer 2 switch, layer 3 switch, hub, router ...) in order to allow both a connection between the SW on the PC and each specific custom device in a sensor group, and to receive the RTSP stream from the camera, too?
I am really struggling because it is the first time for me to face this kind of need with these “only-MAC” devices.

Thanks!
LuKa

If your sensors are layer-2 ethernet only, you must have just switches (and no routers) between two communicating devices. So if your devices communicate with the PC, that means they must all plug into the same switch, or a network of switches. One obvious setup is exactly what you describe: have a small switch per sensor group, and link the seven sensor-group switches to a main switch next to the PC, by fibre or cable depending on distance and speed. But it all depends on the physical layout.

If you additionally have layer-3 cameras, they will work fine because internet protocol will sit perfectly well on top of ethernet.

You only need routers if you have different layer-3 networks which need to communicate. A so-called "layer 3 switch" is actually a switch with a router built in to the same box: you don't need one.

Additionally, if you have VLANs, communicating layer-2 devices must be on the same VLAN. (Thanks @Criggie)

Other relatively exotic setups are also possible: bridges and wireless access points count as switches here, as do hubs and coax ethernet. If the PC behaves as a trunk you could conceivably use different VLANs. However, simplest will almost certainly be best.

If the devices only communicate at layer-2, then you use a layer-2 switch. A hub (layer-1 device) should work, too, but they are practically extinct, and they have the problem of collisions. Routers work at layer-3, and they strip off the layer-2 frame, so that will not work for layer-2 communications.