Explain the difference between a hub, a switch, and a router.

A hub, a switch, and a router are all networking devices used to connect multiple devices in a computer network, but they differ in their functionality and capabilities.

1. Hub:
A hub is the simplest and least intelligent device among the three. It operates at the physical layer (Layer 1) of the OSI model and is responsible for connecting multiple devices together in a network. When a data packet arrives at a hub, it broadcasts the packet to all connected devices, regardless of the destination. This means that all devices connected to a hub share the available bandwidth, resulting in collisions and reduced network performance. Hubs are mostly obsolete and rarely used in modern networks.

2. Switch:
A switch is a more advanced networking device that operates at the data link layer (Layer 2) of the OSI model. It provides a more efficient and intelligent way of connecting devices in a network. Unlike a hub, a switch can identify the destination MAC address of each device connected to it and forward data packets only to the intended recipient. This eliminates collisions and improves network performance. Switches also have multiple ports, allowing for simultaneous communication between different devices. They are commonly used in local area networks (LANs) to create dedicated connections between devices.

3. Router:
A router is a networking device that operates at the network layer (Layer 3) of the OSI model. It is responsible for connecting multiple networks together and directing data packets between them. Routers use routing tables and protocols to determine the best path for data transmission based on the destination IP address. They can also perform network address translation (NAT) to allow multiple devices to share a single public IP address. Routers provide security by acting as a firewall, filtering incoming and outgoing traffic. They are commonly used in wide area networks (WANs) and the internet to connect different networks and enable communication between them.

In summary, a hub simply connects devices together and broadcasts data to all connected devices, a switch intelligently forwards data packets only to the intended recipient, and a router connects multiple networks together and directs data packets between them based on IP addresses.