What Is a Network Hub?

A network hub is a room where everyone must shout and everyone must listen—even when the conversation has nothing to do with them.

When Device A sends data to Device B through a hub, Devices C, D, and E hear it too. They have to examine every message, realize it's not for them, and discard it. The hub doesn't know any better. It receives an electrical signal and repeats it out every other port. That's all it knows how to do.

This simplicity made hubs cheap. It also made them terrible.

The Collision Problem

Imagine a conference room where only one person can speak at a time, but there's no moderator. If two people start talking simultaneously, both messages become garbled. Everyone has to stop, wait a random interval, and try again.

That's a hub. Every device shares a single collision domain. Two simultaneous transmissions corrupt each other. As you add more devices or increase traffic, collisions multiply. Performance degrades not linearly but catastrophically—a hub with heavy traffic can spend more time recovering from collisions than actually moving data.

This is why hubs operate in half-duplex: devices can send or receive, never both at once. The medium is shared, so you must wait your turn.

Shared Bandwidth, Shared Pain

A 10 Mbps hub doesn't give each port 10 Mbps. It provides 10 Mbps total, divided among everyone. Connect eight devices that all want to transmit, and they're fighting over scraps.

The math gets worse under load. A 24-port 100 Mbps hub provides less than 5 Mbps per device if everyone's active—and that's before accounting for collision overhead.

A 24-port 100 Mbps switch? Each port gets 100 Mbps simultaneously. That's 2.4 Gbps of total switching capacity versus 100 Mbps shared.

The Security Problem Nobody Talks About

Here's the part that should make you uncomfortable: on a hub, every device sees everyone else's traffic.

In a college dorm with a hub, one curious student could capture roommates' passwords, emails, browsing history—anything transmitted in cleartext. Just put a network card in promiscuous mode and watch everything flow by.

Hubs couldn't keep secrets because they didn't understand secrets existed. They were democracy taken too far—radical transparency enforced at the physical layer.

Why Hubs Died

Switch prices fell. By the mid-2000s, the cost argument for hubs evaporated. Why accept terrible performance to save a few dollars per port?

But the real death blow was Gigabit Ethernet. You cannot build a Gigabit hub. The technology fundamentally requires switching—the timing constraints of collision detection at gigabit speeds are physically impossible to meet.

Speed itself demanded intelligence. The dumb broadcast approach couldn't scale.

Today, hubs are difficult to even purchase. Their extinction was thorough.

The Few Things Hubs Did Well

Hubs had one genuine virtue: visibility. Because all traffic went everywhere, a protocol analyzer connected to any port could see everything. This made hubs useful for teaching and troubleshooting.

Modern networks accomplish this through switch port mirroring (SPAN ports), which copies selected traffic to a monitoring port without the performance penalty of broadcasting everything.

Some organizations kept a hub in a drawer specifically for troubleshooting. That's about the only legitimate use case that remained—and even that's now obsolete.

How Switches Fixed Everything

A switch learns. It watches traffic and builds a table mapping MAC addresses to ports. When a frame arrives for Device B, the switch sends it only to Device B's port. Devices C, D, and E never see it.

This creates separate collision domains per port. Device A can talk to Device B while Device C talks to Device D—simultaneously, at full speed, with no interference. Full-duplex becomes possible: send and receive at the same time.

The switch turned networking from a shouting match into private conversations.

Recognizing a Hub

If you encounter ancient networking equipment:

Check the label. It might explicitly say "hub." Some old switches were called "switching hubs" to distinguish themselves.

Test performance. High collision rates and miserable throughput with multiple active devices indicate a hub.

Watch the lights. Hub activity lights often blink for any traffic, not just traffic on that port. Switches show per-port activity.

Consider the age. Anything from the mid-2000s onward is almost certainly a switch. Hubs were already dying by then.

The Larger Story

The hub-to-switch transition mirrors a broader pattern in networking: the replacement of dumb, shared infrastructure with intelligent, switched fabrics.

Early Ethernet used coaxial cable in a bus topology—literally one wire shared by everyone, a distributed hub with even worse characteristics. Hubs with twisted-pair cabling improved manageability but kept the shared collision domain. Switches added intelligence while keeping the convenient star topology.

Modern switches now include VLANs, Quality of Service, Power over Ethernet, and Layer 3 routing. The distance from a hub to a modern data center switch is the distance from a megaphone to a telephone network.

The hub is a fossil. But understanding it explains why switches matter—and why the ability to have parallel, private, full-speed conversations on a network isn't a luxury. It's the foundation everything else is built on.