Hub
Hub
A hub is a basic networking device that connects multiple computers or network devices together.
Unlike a switch, a hub is not intelligent. It simply receives data on one port and sends it out to every other port.
A hub operates at:
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OSI Layer 1 (Physical Layer)
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How a Hub Works
Imagine three computers connected to a hub:
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PC-A
|
Hub
/ \
PC-B PC-C
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If PC-A sends data to PC-B:
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PC-A → Hub
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The hub does not know where PC-B is.
Instead, it sends the data to all devices:
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PC-A → Hub
↙ ↓ ↘
PC-B PC-C
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PC-B accepts the data.
PC-C receives it and discards it.
Characteristics of a Hub
Layer 1 Device
A hub works only with electrical signals.
It does not examine:
MAC addresses
IP addresses
Protocols
Broadcasts Everything
Every message is sent to every port.
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One sends = Everyone receives
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Half-Duplex Communication
Devices must take turns transmitting.
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Send OR Receive
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Not both simultaneously.
Shared Bandwidth
All devices share the same bandwidth.
Example:
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100 Mbps Hub
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Ten devices share that 100 Mbps.
Collision Domain
A hub creates one large collision domain.
A collision occurs when:
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PC-A sends
and
PC-B sends
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at the same time.
Result:
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Collision
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Network performance decreases.
Hub vs Switch
Feature Hub SwitchOSI Layer Layer 1 Layer 2
Intelligent No Yes
Uses MAC Addresses No Yes
Sends Data To All Ports Correct Port Only
Collision Domains One One Per Port
Duplex Half Full
Performance Slow Fast
Example
Hub
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PC1 ---> Hub ---> Everyone
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All devices see the traffic.
Switch
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PC1 ---> Switch ---> PC2 Only
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Only the intended device receives the traffic.
Why Hubs Are Obsolete
Modern networks use switches because they:
✅ Reduce collisions
✅ Increase speed
✅ Improve security
✅ Support full-duplex communication
✅ Make better use of bandwidth
Today, hubs are rarely found except in older networks or networking labs.
Network+ Exam Tip
Remember:
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Hub = Layer 1
Switch = Layer 2
Router = Layer 3
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And:
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Hub = Broadcasts Everything
Switch = Uses MAC Addresses
Router = Uses IP Addresses
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Quick Memory Trick
Hub = "Dumb Device"
A hub doesn't know who should receive the data, so it sends the signal to everyone.
Simple definition: A hub is a Layer 1 network device that connects multiple devices and repeats incoming signals out all other ports without examining MAC or IP addresses. It creates a single collision domain and has largely been replaced by switches.
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