I understand that a switch is a layer 2 device, but don't understand why a Hub is stated as layer 2 device in the Networking class console.
They are a layer 2 device - they also transmit based on MAC-adresses - like switches. The difference is, that they send out the packets to all connections not just the one with the right MAC-adress.
http://en.wikipedia.org/wiki/Ethernet_hub#Physical_layer_function
Hubs are layer 1 devices,Hubs are just splitters. It simply receives frames in the ingress port and sends it out to all other ports. It knows nothing about MAC address. You probably know those 2/more way cable splitter that you transmit on the in-port and sends out the same signals transmitted to all the out-ports. That's basically the same logic with the Hub just that its nicer networking box.
edit* Unless they were referring to a Managed Hub in that case it will have MAC address associated with it.
Hubs unlike switches do not have any intelligence and do not process packets in any way. They just send all the data received on the hub out to all the other active ports on the hub with the exception of the incoming port. They are basically bit spitters which send out the received packets to all connected devices on the hub without using any layer 2 logic (MAC addresses). The best analogy I've heard compared a hub to a bucket with holes in it. You pour the information in like water and it flows out all the holes (active hub ports) without any regard to where it goes. The information is broadcasted out all active ports by the hub and any workstations connected to that hub that does not need that packet will discard it. Hubs are basically layer 1 devices without any intelligence and do not separate collision or broadcast domains. Switches are basically layer 2 (MAC addresses) with some intelligence and separate collision domains. Some switches can function at layer 3 with additional functionality. Routers function at layer 3 and use IP addresses to separate broadcast domains.
ADKM and dj said it very well. I would just like to second their answer for some added closure for you. Hubs are layer 1 devices unless they are managed hubs.
I understand that a switch is a layer 2 device, but don't understand why a Hub is stated as layer 2 device in the Networking class console.
