Why Hubs Belong to the Past

To connect several devices into a LAN (Local Area Network), you need a central device that joins them. Early on, that device was the hub. Today it is the switch. Understanding why hubs were replaced reveals how local networks really work and why switches are so much better. This lesson focuses on the humble hub and the problems that made it obsolete.

A hub is a simple device with several ports that connects devices in a star shape. But a hub is not smart: when a frame (a unit of data on a LAN) arrives on one port, the hub simply repeats it out every other port. It does not look at addresses or decide where the data should go. Every connected device receives every transmission, whether it is the intended recipient or not.

A hub works at the physical layer (Layer 1 of the OSI model). It only repeats and amplifies electrical signals; it has no awareness of MAC addresses or frames as meaningful data. That is why a hub is sometimes called a multiport repeater. Because it has no intelligence about destinations, it cannot make forwarding decisions the way a switch can.

Because a hub repeats everything to everyone, all connected devices share one collision domain — a region where two transmissions can collide if devices send at the same time. With everyone sharing the medium, collisions are frequent, and the more devices you add, the worse it gets. A hub effectively recreates the shared-bus problem in a star shape.

Hubs force half-duplex operation, meaning a device can send or receive but not both at once. To cope with collisions, devices used CSMA/CD (Carrier Sense Multiple Access with Collision Detection): listen first, send if quiet, and if a collision happens, back off and retry. This works but wastes time and bandwidth, especially as traffic grows on a busy hub.

On a hub, all devices share the total bandwidth. If a hub is rated at 100 Mbps and ten devices are busy, they effectively split that 100 Mbps among them. A switch, by contrast, gives each port its own full bandwidth. This shared-pipe limitation made hubs slow under load and was a major reason they could not keep up as networks grew.

Hubs also have a security problem. Since every frame goes to every port, any device on the hub can capture all the traffic just by listening — a technique called sniffing. Sensitive data is exposed to everyone connected. Switches reduce this risk by sending frames only to the intended port, making casual eavesdropping much harder on a normal switched network.

The contrast is stark:

• Hub — repeats to all ports, one collision domain, shared bandwidth, half-duplex, insecure.
• Switch — forwards to the right port, separate collision domains, full bandwidth per port, full-duplex, more secure.

Every advantage belongs to the switch, which is why hubs disappeared from real networks.

True hubs are essentially extinct in modern networks; inexpensive switches replaced them entirely. You might still hear the word "hub" used loosely for any central connecting device, and hubs occasionally appear in labs or for deliberately sniffing traffic during analysis. For the exam, treat the hub as obsolete technology you must understand historically and contrast with the switch.

Between hubs and switches came the bridge. A bridge connects two network segments and, unlike a hub, reads MAC addresses to decide whether traffic should cross between them, filtering local traffic from passing through. A bridge is essentially a switch with very few ports — a switch is sometimes called a multiport bridge. Bridges introduced the smart, address-aware forwarding that switches later perfected.

Even though hubs are gone, the concepts they teach are central. Collision domains, half-duplex, CSMA/CD, and shared bandwidth all come from the hub era, and the exam tests them. Understanding the hub's flaws is the clearest way to appreciate what switches fixed — and prepares you for the next lessons on switch forwarding, MAC tables, and collision versus broadcast domains.

Test your understanding of hubs.

You learned that a hub is a Layer 1 multiport repeater that blindly sends every frame to all ports. This creates one shared collision domain, forces half-duplex operation with CSMA/CD, splits bandwidth among all devices, and lets any device sniff all traffic. These flaws made hubs obsolete. Switches fixed each problem by forwarding frames only to the right port. The hub's concepts still matter because they underpin collision domains and the topics ahead.