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What’s a Network Hub?

An Ethernet hub is a Layer 1 network device that connects multiple computers by broadcasting all incoming traffic out every port, creating security vulnerabilities and collision risks that led to its replacement by more advanced technology.

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About this video

An Ethernet hub is a multiport repeater that operates at Layer 1 of the OSI model, meaning it works purely at the physical signal level without any awareness of addressing or traffic management. Its function is straightforward: any signal arriving on one port is immediately retransmitted out every other port, allowing all connected devices to participate on the same network segment. This behavior is what defines a hub as a multiport repeater rather than a more intelligent networking device. Despite its simplicity, the hub's broadcast behavior creates two critical problems. First, because every transmission reaches every connected device, there is an inherent security risk — data intended for one machine is visible to all others on the segment. Second, if two devices transmit at the same time, their signals collide on the shared medium, corrupting both transmissions in what is known as a collision. The more devices connected to a hub, the more frequently collisions occur, degrading overall network performance. These limitations — poor security and collision-prone traffic handling — are the primary reasons Ethernet hubs have been replaced by switches in virtually all modern network deployments. Understanding how hubs operate, however, remains valuable as a foundation for comparing them to smarter devices and grasping core concepts like collision domains and network segmentation.

What you'll learn

What's covered

Ethernet Hubs

Aligned to

CompTIA Network+
1.2 Compare and contrast networking appliances, applications, and functions.
Cisco CCNA
1.1 Explain the role and function of network components
1.13 Describe switching concepts
CompTIA A+ Core 1
2.2 Compare and contrast common networking hardware.

Key terms

Ethernet Hub
A multi-port network device that repeats any incoming signal out to all other ports, allowing computers to communicate on a network without any traffic filtering or direction.
Collision Domain
A network segment where data packets can collide with each other when transmitted simultaneously.
Half Duplex
A communication mode that allows data to be transmitted in both directions but only one direction at a time.
Physical Layer
Layer 1 of the OSI model, responsible for the transmission of raw bits over a physical medium.

Transcript

We don't really use hubs much anymore, at least not Ethernet hubs, because of some problems with them. But it's still helpful to understand what a hub is so we can relate to it in future lessons.

What a Hub Does

An Ethernet hub is what we use to interconnect computers on an Ethernet network. So what we had is we had a bunch of computers that wanted to speak on a network. We plug them into this hub, and the hub would redistribute any communication. So if this computer talked on this network, what would happen is that would get sent out all other ports, so all devices could then communicate on this network. So that's what a hub is.

What I like to think about it as is it's a multi-port repeater. A repeater, what is it? It's a couple of ports, and whatever comes in on one port gets repeated out the other side. So I like to think of this as, whatever comes in on one port gets sent out all of the ports. So it's just much more ports than just a regular repeater.

Problems With Hubs

When it comes to hubs, there's a couple of problems with them. Number one, whatever gets sent out from a computer, even if it's destined to another computer, it gets sent out to all computers on the network. So there's security issues.

Another problem is if this device is talking, since it gets sent out all other ports, if another computer tries to talk as well and it gets sent out those same ports, now what's happened essentially is a collision. We call it a collision when two computers try to talk on a hub at the same time. And so this is problematic. So that's why we really don't use hubs much nowadays.

Just like a repeater, it's operating at layer 1, just taking whatever signal is coming into a port and sending it out all other ports.

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