What's the difference between a hub, a switch, and a router?

The definition

•          Hub

A hub is a general network component mostly used in a LAN, which connects multiple computers or other network devices together. A hub operates at the physical layer of the OSI model. It has no routing table or intelligence, and simply broadcasts all network data across each connection.

That means, every computer or device connected to the hub “sees” everything every other computer or device on the hub does. It’s up to the computers themselves to decide if a message is for them and whether or not it should be paid attention to. The hub is uncapable of distinguishing where a data frame should be sent to. Passing it along to every device ensures that it will reach its intended destination.

However, this raises security and privacy concerns, because traffic could not be safeguarded or controlled. Moreover, this places a lot of traffic on the network and can lead to poor network response times.

•          Switch

A switch does what a hub does, connecting computers or devices, but more efficiently. It uses the MAC address to identify the location of the connected devices and forwards data frame to and from destined devices. In other words, the network traffic only goes where it needs to, instead of to every device.

There are two different kinds of switches. Layer-2 switches move data within one LAN, while layer-3 switches perform traffic directing between WANs.

•          Router

A router connects at least two networks, commonly two LANs, or two WANs, or one LAN and its ISP’s network. It select optimal paths for data packets to cross networks and reach their destinations. Moreover, a router is like a computer that can be programmed to understand, manipulate, and act on the data it handles. A router is much more functional, intelligent and complicated than hub or switch.

A router operates at the network layer of the OSI model.

Most fundamental difference

Today most routers have become something of a Swiss Army knife, combining the features and functionality of a router and switch/hub into a single unit. So conversations regarding these devices can be a bit misleading, especially to someone new to computer networking. However, there are still quite some fundamental differences.

In short, a hub glues together an Ethernet network segment, a switch can connect multiple Ethernet segments more efficiently and a router can do those functions plus route TCP/IP packets between multiple LANs and/or WANs; and much more of course.