What is a Network Hub?

Updated on July 22, 2025

Network hubs were once a key component of local area networks (LANs), but they’ve become obsolete in modern networking. Understanding what a hub is and how it works helps explain why today’s networks use switches instead. This guide covers the technical basics of hubs and their place in networking history.

A hub is a basic Layer 1 networking device that connects multiple Ethernet devices together within a single network segment. It functions as a multi-port repeater, receiving electrical signals from one connected device and broadcasting them to all other connected devices without any intelligence or filtering.

Definition and Core Concepts

What is a Network Hub?

A network hub (also called an Ethernet hub, network hub, or repeater hub) is a Layer 1 (Physical Layer) networking device that serves as a central connection point for multiple devices on a network. Unlike modern switches, hubs operate without intelligence—they simply repeat every signal they receive to all connected devices.

Layer 1 (Physical Layer) Operation

Hubs operate exclusively at Layer 1 of the OSI (Open Systems Interconnection) model. This means they work with raw electrical signals and bits rather than understanding data frames, MAC addresses, or IP addresses. They amplify and regenerate signals but cannot interpret the data they’re transmitting.

Multi-Port Repeater Functionality

At its core, a hub is essentially a repeater with multiple ports. Traditional repeaters connect two network segments, but hubs extend this concept to connect multiple devices simultaneously. Each port on a hub can connect to a single device, creating a star topology while maintaining the electrical characteristics of a single network segment.

Broadcasting Behavior

When a hub receives data on any port, it immediately broadcasts that data out of all other active ports. This broadcasting happens regardless of the intended recipient. If Device A wants to send data to Device B, every device connected to the hub receives that transmission.

Single Collision Domain

All devices connected to a hub share a single, large collision domain. This means that when multiple devices attempt to transmit simultaneously, their signals collide and become garbled. The collision affects every device on the network segment, requiring all devices to stop transmitting and retry after a random delay.

Half-Duplex Communication

Hubs only support half-duplex communication, meaning devices cannot send and receive data simultaneously. This limitation stems from the shared electrical medium—if a device tried to transmit while receiving, its own transmission would interfere with the incoming signal.

How It Works

Signal Reception and Processing

When a connected device transmits data, the hub receives the electrical signal on the corresponding input port. The hub’s circuitry detects the signal and prepares it for retransmission. This process happens at the electrical level without any understanding of the data’s content or intended destination.

Signal Regeneration

Like a traditional repeater, the hub regenerates the received signal by amplifying it and cleaning up any electrical noise that may have accumulated during transmission. This regeneration helps maintain signal quality across the network segment and extends the effective transmission distance.

Broadcast to All Ports

After regenerating the signal, the hub simultaneously transmits it out of all other active ports. This broadcasting ensures that every connected device receives the transmission, but it also means that all devices must process every frame on the network, even if they’re not the intended recipient.

Collision Detection and Handling

When two or more devices attempt to transmit simultaneously, their signals collide on the shared medium. The hub detects this collision as a garbled electrical signal and propagates it to all ports. Connected devices recognize the collision and invoke their CSMA/CD (Carrier Sense Multiple Access with Collision Detection) protocol to handle the situation.

Shared Medium Characteristics

All devices connected to a hub share the total available bandwidth of the network segment. If a hub operates at 10 Mbps, that bandwidth is divided among all active devices. As more devices communicate simultaneously, the effective bandwidth per device decreases significantly.

Key Features and Components

Layer 1 Device Limitations

Operating at Layer 1 means hubs cannot understand MAC addresses, IP addresses, or any higher-layer protocol information. They work purely with electrical signals and cannot make intelligent forwarding decisions based on network addresses.

Central Connection Point

Hubs provide a convenient way to physically connect multiple devices in a star topology. This centralized approach simplified network cabling compared to earlier bus topologies while maintaining the electrical characteristics of a single network segment.

No Filtering or Segmentation

Unlike switches, hubs cannot filter traffic or segment networks. Every frame transmitted by any device reaches every other device on the network segment. This lack of filtering creates both performance and security implications.

Shared Bandwidth Architecture

The hub’s shared bandwidth model means that network performance degrades as more devices are added or as network traffic increases. Peak performance is only achieved when a single device is transmitting at any given time.

Use Cases and Applications

Small, Simple LANs

Historically, hubs were used in very small networks where cost was the primary concern and traffic volume was minimal. These networks typically consisted of fewer than 10 devices with light communication requirements.

Early Home Networks

Before consumer switches became affordable, hubs were common in early home networking setups. They provided an inexpensive way to connect multiple computers to share resources like printers and internet connections.

Testing and Lab Environments

Some network testing scenarios benefit from the hub’s broadcasting behavior. When troubleshooting network issues or analyzing traffic patterns, having all devices receive every transmission can be useful for diagnostic purposes.

Legacy Network Infrastructure

Hubs may still be found in older network installations that haven’t been upgraded. However, these implementations are increasingly rare due to the hub’s significant limitations and the affordability of modern switches.

Advantages and Trade-offs

Historical Advantages

Hubs offered several advantages that made them attractive in early networking:

• Simplicity: Hubs required no configuration. They provided true plug-and-play functionality—simply connect devices and power on the hub.
• Low Cost: Manufacturing costs were minimal due to their simple design, making them an affordable option for budget-conscious network deployments.

Significant Limitations

The disadvantages of hubs far outweigh their benefits in modern networks:

• Large Collision Domain: All connected devices share a single collision domain, leading to frequent collisions and severely degraded performance as network size or traffic increases.
• No Traffic Isolation: Broadcasting all traffic to all devices creates security vulnerabilities and privacy concerns. Any device can potentially monitor all network communications.
• Shared Bandwidth: The total bandwidth is divided among all active devices, severely limiting throughput in multi-device scenarios.
• Half-Duplex Operation: Devices cannot send and receive data simultaneously, further limiting network performance.
• Limited Scalability: Performance degrades rapidly as devices are added, making hubs unsuitable for growing networks.
• Security Vulnerabilities: The broadcast nature of hubs makes it easy for malicious devices to intercept network traffic.

Modern Obsolescence

Switches have completely replaced hubs in modern LANs due to their ability to create separate collision domains, support full-duplex communication, and provide intelligent frame forwarding. The cost difference between hubs and switches has become negligible, eliminating the hub’s primary historical advantage.

Key Terms Reference

• Hub (Network Hub, Repeater Hub): A Layer 1 networking device that connects multiple Ethernet devices and broadcasts all received traffic to all connected devices.
• Layer 1 (Physical Layer): The lowest layer of the OSI model, responsible for transmitting raw bits over physical media.
• Broadcasting: The process of sending network traffic to all devices on a network segment simultaneously.
• Collision Domain: A network segment where data frame collisions can occur when multiple devices transmit simultaneously.
• Half-Duplex Communication: A communication mode where data can flow in only one direction at a time.
• CSMA/CD: Carrier Sense Multiple Access with Collision Detection, a protocol used to handle collisions in shared media networks.
• Switch: A Layer 2 network device that forwards frames to specific destinations based on MAC addresses, providing separate collision domains for each port.
• Bandwidth: The maximum rate of data transfer across a network connection, typically measured in bits per second.
• Throughput: The actual rate at which data is successfully transferred across a network connection.
• MAC Address: A unique hardware identifier assigned to network interface cards, which hubs cannot understand or use for forwarding decisions.