1. Hubs – These are used to connect devices in the same location into one collision domain. Hubs are not intelligent devices and cause unnecessary congestion on the network.
When a hub receives a frame, it replicates that frame and floods it out on all interfaces looking for the destination. It’s up to the hosts on the network to check the frame header and see who the packet is intended for!
This creates a lot of collisions and the end result is a slow network.
Hubs operate at Layer 1 of the OSI model.
2. Bridges/Switches – Bridges were used before switches and in fact you can’t find a bridge on the market today. However switches and bridges do the same thing, i.e. breakup collision domains.
Switches create separate collision domains but a single broadcast domain.
Switches are intelligent devices and forward frames based on the destination MAC addresses.
Switches build MAC tables to help them do this intelligent forwarding of frames to destination hosts.
Switches operate at Layer 2 of the OSI model.
Switches are the best option to use when connection devices in a LAN (Local Area Network).
3. Routers – These operate at Layer 3 of the OSI model and are used for packet switching.
Routers are used to segment broadcast domains.
Routers forward packets based on destination IP address as opposed to switches which use destination MAC addresses.
Routers are used to interconnect separate networks; e.g. Connect a LAN to the internet, Connect two LANs with different subnet ranges.