Introduces the fundamental concepts, purpose and applications of computer networks.
Explores different network classifications based on geographical coverage, purpose and architecture.
Introduces different physical and logical network structures and how network devices are organised.
Provides practical knowledge of the hardware used to build and connect computer networks.
Introduces the physical and wireless technologies used to transmit data across networks
Explains how network communication is structured using standard models and protocols.
Introduces Ethernet technology and the role of MAC addresses in local network communication
Develops practical understanding of IPv4 addressing and network identification
Teaches learners how to divide networks into smaller subnets and introduces IPv6 addressing.
Introduces network switching and provides practical skills for configuring and managing switches.
Teaches learners how to logically separate networks and carry traffic between network segments.
Introduces routing and explains how routers forward traffic between different networks.
Explores essential network services that support addressing, name resolution and internet connectivity.
Provides practical knowledge of wireless networks and access point configuration.
Introduces fundamental techniques for protecting networks, devices and network traffic.
Develops practical skills for managing, monitoring and troubleshooting computer networks.
Introduces modern networking technologies and the role of networking in cloud and virtualised environments.
Enables learners to apply their networking knowledge by designing, configuring, testing and documenting a complete network solution
A switch is one of the most important devices used in modern computer networks. It allows computers, printers, servers, wireless access points, IP phones and other network devices to communicate within a Local Area Network (LAN).
For example, in a computer laboratory with 30 computers, connecting every computer directly to every other computer would be impractical. A network switch provides a central point where the computers can connect and communicate efficiently.
Modern Ethernet switches use MAC addresses to determine where Ethernet frames should be forwarded. A switch learns which MAC addresses are associated with which ports and uses this information to forward traffic toward the correct destination.
By the end of this lesson, the learner should be able to:
Define a network switch.
Explain the purpose of a switch.
Identify the major parts of a switch.
Explain how a switch forwards data.
Explain MAC address learning.
Describe a MAC address table.
Differentiate between a hub, switch and router.
Identify different types of network switches.
Explain managed and unmanaged switches.
Describe basic switch features such as VLANs and PoE.
Connect computers to a switch.
Perform basic switch troubleshooting.
A network switch is a networking device that connects multiple devices within a network and forwards Ethernet frames to the appropriate destination.
A typical switch may have several Ethernet ports. Computers, printers, servers, access points and other devices can be connected to these ports.
For example:
Computer 1 → Switch ← Computer 2
** ↓**
** Printer**
** ↓**
** Router**
The switch provides communication between devices connected to the network.
Cisco describes Ethernet switches as foundational networking hardware used to connect devices such as computers, wireless access points, servers and IoT devices in an Ethernet LAN.
Switches are important because they:
Connect multiple network devices.
Allow devices to communicate with one another.
Forward Ethernet frames toward their destinations.
Reduce unnecessary traffic compared with traditional hubs.
Provide multiple physical network connections.
Support network segmentation through VLANs on managed models.
Can provide Power over Ethernet (PoE) on supported models.
Help organizations build scalable LANs.
Switches are commonly used in schools, offices, banks, hospitals, businesses, universities, computer laboratories and data centres.
A typical physical switch may contain the following components:
These are the ports used to connect network devices using Ethernet cables.
Common port speeds include:
10 Mbps
100 Mbps
1 Gbps
2.5 Gbps
10 Gbps
Higher speeds on enterprise switches
A switch may have 5, 8, 16, 24, 48 or more ports.
The switch requires electrical power to operate.
Some switches may also support redundant power supplies for higher availability.
LED indicators can show information such as:
Power status
Link status
Activity
Port speed
PoE status
System status
Managed switches may provide a console or management interface for configuration and troubleshooting.
Some switches include slots for optical or high-speed network connections.
These may be used for:
Fibre connections
Switch-to-switch connections
Uplink connections
Long-distance networking
Understanding how a switch works is one of the most important networking skills for beginners.
Suppose three computers are connected to a switch:
PC-A → Port 1
PC-B → Port 2
PC-C → Port 3
Each network interface has a MAC address.
When PC-A sends an Ethernet frame to PC-B, the switch examines the frame and determines where the destination device is located.
The basic process is:
A frame enters the switch.
The switch examines the source MAC address.
The switch learns the source MAC address and associated port.
The switch examines the destination MAC address.
The switch checks its MAC address table.
If the destination is known, the switch forwards the frame through the appropriate port.
If the destination is unknown, the switch may flood the frame within the relevant network segment.
When the destination responds, the switch can learn its MAC address.
This process allows the switch to forward traffic efficiently.
MAC stands for Media Access Control.
A MAC address is a hardware-level address associated with a network interface.
A MAC address is normally represented using hexadecimal notation, for example:
00:1A:2B:3C:4D:5E
Another representation may be:
00-1A-2B-3C-4D-5E
MAC addresses are used by Ethernet switches to identify devices at the data-link layer.
A useful distinction is:
MAC address: Used for local Ethernet frame delivery.
IP address: Used for network-layer addressing and communication between networks.
Cisco explains that Layer 2 switches identify end devices using MAC addresses, while routers use IP addresses to identify network connections.
A switch maintains a table containing information about learned MAC addresses.
A simplified table could look like this:
| MAC Address | Switch Port |
|---|---|
| 00:11:22:33:44:55 | Port 1 |
| 00:11:22:33:44:66 | Port 2 |
| 00:11:22:33:44:77 | Port 3 |
The switch uses this table to determine where frames should be forwarded.
For example:
If the switch receives a frame destined for:
00:11:22:33:44:66
and the table shows that this address is connected to Port 2, the switch forwards the frame toward Port 2.
MAC address learning is the process by which a switch automatically learns which MAC addresses are associated with its ports.
Suppose PC-A is connected to Port 1.
When PC-A sends a frame, the switch sees the source MAC address and records something similar to:
PC-A MAC → Port 1
If PC-B is connected to Port 2:
PC-B MAC → Port 2
The switch gradually builds its MAC address table as devices communicate.
Cisco documentation describes MAC address learning and provides commands for viewing and managing MAC address-table information.
Suppose PC-A sends a frame to a MAC address that the switch has not yet learned.
The switch may flood the frame out the appropriate ports, except the port on which the frame arrived.
This allows the intended device to receive the frame and respond.
After communication takes place, the switch can learn the destination device's location.
This is one reason why switches need MAC address tables.
A switch primarily deals with Ethernet frames when operating at Layer 2.
An Ethernet frame contains information such as:
Source MAC address
Destination MAC address
Payload/data
Error-checking information
The switch examines the MAC addresses to make forwarding decisions.
A hub is an older networking device that forwards incoming signals to multiple connected ports.
A switch is more intelligent because it can learn MAC addresses and forward traffic toward the appropriate destination.
| Feature | Hub | Switch |
|---|---|---|
| MAC learning | No | Yes |
| Intelligent forwarding | No | Yes |
| Traffic handling | Broadcasts to connected ports | Forwards based on MAC information |
| Efficiency | Lower | Higher |
| Security | Lower | Better |
| Modern usage | Rare | Very common |
Cisco notes that hubs send copies of traffic to connected devices, while switches maintain MAC address information and forward traffic toward its destination.
Switches and routers perform different jobs.
| Feature | Switch | Router |
|---|---|---|
| Main purpose | Connect devices in a LAN | Connect different networks |
| Common addressing | MAC address | IP address |
| Typical layer | Layer 2 | Layer 3 |
| Example | Connect PCs in an office | Connect office network to Internet |
| VLAN support | Common on managed switches | Used for routing between networks |
| Internet connection | Usually through a router | Directly provides network-to-network connectivity |
Modern switches can also include Layer 3 routing functionality, so the distinction is not always absolute.
An unmanaged switch normally works with little or no configuration.
You connect the devices and it begins forwarding traffic.
It is suitable for:
Small offices
Homes
Simple computer laboratories
Basic network expansion
Cisco describes unmanaged switches as devices that can generally be connected and used without configuration.
A managed switch provides configuration and monitoring capabilities.
An administrator may configure:
VLANs
Port settings
Security controls
Quality of Service
Trunk ports
Monitoring
Access controls
Link aggregation
Managed switches are common in organizations requiring greater control over their networks.
A Layer 2 switch primarily makes forwarding decisions using MAC addresses.
A Layer 3 switch can perform switching as well as routing functions.
It may be used to route traffic between VLANs or IP networks.
PoE means Power over Ethernet.
A PoE switch can provide both:
Network connectivity
Electrical power
through an Ethernet cable to supported devices.
Examples include:
IP cameras
Wireless access points
VoIP phones
In larger networks, switches may perform different roles.
Connects end devices such as:
Computers
Printers
IP phones
Access points
Aggregates connections from access switches and can provide routing, policy enforcement and other network functions.
Provides high-speed connectivity between major sections of an enterprise network.
Small organizations may not require separate access, distribution and core layers.
Each physical Ethernet connection on a switch is called a port.
For example:
Port 1 → Computer
Port 2 → Printer
Port 3 → Access Point
Port 4 → Server
Port 24 → Router/uplink
Ports can have different speeds and capabilities.
Managed switches commonly use different port configurations.
An access port normally connects an end device to a particular VLAN.
Examples:
Desktop computer
Printer
IP phone
Camera
A trunk port can carry traffic for multiple VLANs between network devices.
For example:
Switch A → Trunk Link → Switch B
The connection may carry:
VLAN 10
VLAN 20
VLAN 30
VLAN 40
This connects directly to the previous lesson on VLANs.
A VLAN allows a physical switch network to be logically divided into separate networks.
For example, an institution may have:
VLAN 10 – Administration
VLAN 20 – Students
VLAN 30 – ICT Department
VLAN 40 – Guests
A managed switch can assign ports to different VLANs.
This improves organization and can support security and traffic management.
Consider a computer laboratory with 24 computers.
A possible design is:
24 Computers → 24-Port Switch → Router → Internet
The switch provides local connectivity between the computers and connects the laboratory to the router.
If the laboratory expands to 48 computers, another switch can be added.
24 PCs → Switch 1 → Switch 2 → Router
The switches can therefore help networks grow without requiring every device to connect directly to the router.
A small office may have:
15 computers
2 printers
3 wireless access points
2 IP phones
1 server
1 router
A switch can provide connectivity for these devices.
Example:
Computers
↓
Switch
↓
Router/Firewall
↓
Internet
Wireless access points may also connect to the switch so that wireless users can access network resources.
Important switch specifications include:
Number of ports
Port speed
Switching capacity
Forwarding rate
MAC address table capacity
VLAN support
PoE support
Management capabilities
Fibre/SFP support
Security features
Power consumption
When purchasing a switch, the organization should consider both current requirements and expected future growth.
Modern switched Ethernet networks commonly support full-duplex communication.
This means a device can transmit and receive simultaneously over a network link.
This improves network performance compared with older shared-media environments.
A switch can provide important security features, especially when it is managed.
Examples include:
Port security
VLAN segmentation
MAC address controls
802.1X authentication
Disable unused ports
Management authentication
Secure management protocols
Monitoring and logging
However, a switch alone does not make a network secure.
A secure network normally requires several layers of protection.
Common switch-related problems include:
Possible causes:
Damaged cable
Incorrect cable connection
Disabled port
Faulty network card
Faulty switch port
Possible causes:
Speed/duplex problems
Network congestion
Damaged cable
Overloaded network device
Excessive broadcast traffic
Possible causes:
Wrong VLAN
Incorrect IP configuration
Faulty cable
Incorrect switch configuration
Port disabled
Possible causes:
Switch power failure
Main uplink failure
Faulty switch
Network loop
Major configuration problem
When troubleshooting a switch:
Check whether the switch has power.
Check the Ethernet cable.
Check port LEDs.
Try another switch port.
Test with another network cable.
Check the device's network adapter.
Check IP configuration.
Check VLAN configuration if applicable.
Check the switch's MAC address table.
Check the uplink to the router or another switch.
Review logs and configuration on managed switches.
Test connectivity using tools such as ping.
Find a network switch in a school, office, laboratory or home.
Record:
| Item | Observation |
|---|---|
| Manufacturer | |
| Model | |
| Number of ports | |
| Port speed | |
| Managed/Unmanaged | |
| PoE support | |
| Power source | |
| Uplink ports | |
| Status LEDs |
Using available equipment:
Obtain a switch.
Obtain two or more computers.
Obtain Ethernet cables.
Connect each computer to the switch.
Power on the switch.
Check the link LEDs.
Configure appropriate IP addresses if necessary.
Test connectivity between computers using ping.
Record your results.
If a managed switch is available:
Connect two computers.
Generate network traffic between them.
Access the switch management interface.
Locate the MAC address table.
Identify the MAC address of each computer.
Identify the corresponding switch port.
Disconnect one computer.
Observe what happens to the MAC table entry after some time.
The exact commands depend on the switch manufacturer and model.
On Cisco devices, administrators can use MAC address-table commands to view MAC information.
Research or inspect a hub, switch and router.
Prepare a table showing:
Purpose
Address used
Number of ports
Typical location
Main function
Example use
Explain why a modern office would normally use a switch instead of a hub.
Design a network for an office containing:
10 computers
2 printers
1 server
2 wireless access points
1 router
1 Internet connection
Determine:
Number of switches required.
Number of ports required.
Which devices connect to the switch.
Which device connects the LAN to the Internet.
Whether a managed or unmanaged switch would be appropriate.
Whether PoE would be useful.
What is a network switch?
What is the main purpose of a switch?
What is a MAC address?
What is a MAC address table?
Explain MAC address learning.
What happens when a switch receives a frame?
What happens when the destination MAC address is unknown?
What is the difference between a hub and a switch?
What is the difference between a switch and a router?
What is an unmanaged switch?
What is a managed switch?
What is a Layer 2 switch?
What is a Layer 3 switch?
What does PoE mean?
Give three devices that can use PoE.
What is an access port?
What is a trunk port?
What is a VLAN?
Give four factors to consider when purchasing a switch.
List five steps used when troubleshooting a switch.
A training institution wants to establish a new computer laboratory with 30 computers.
Prepare a basic network plan that includes:
Number of switches required
Number of switch ports
Router requirement
Ethernet cables
Wireless access points
Internet connection
Proposed IP addressing
Basic security considerations
Estimated future expansion
Explain why you selected the particular type of switch.
Switch: A networking device that connects devices and forwards Ethernet frames.
MAC Address: A hardware-level address associated with a network interface.
MAC Address Table: A table that maps learned MAC addresses to switch ports.
Port: A physical or logical connection on a network switch.
Managed Switch: A switch that can be configured and monitored by an administrator.
Unmanaged Switch: A switch designed primarily for simple connectivity without extensive configuration.
PoE: Power over Ethernet.
VLAN: Virtual Local Area Network.
Access Port: A switch port normally assigned to a single VLAN for an end device.
Trunk Port: A port capable of carrying traffic for multiple VLANs.
Layer 2 Switch: A switch that primarily forwards frames using MAC addresses.
Layer 3 Switch: A switch capable of performing routing functions in addition to switching.
A switch is a fundamental device in modern computer networks. It connects computers, printers, servers, access points and other devices and allows them to communicate efficiently.
The switch learns MAC addresses and associates them with ports. It then uses its MAC address table to determine where Ethernet frames should be forwarded.
Important types of switches include managed, unmanaged, Layer 2, Layer 3 and PoE switches.
Understanding switches is essential before progressing to advanced topics such as VLAN configuration, trunking, Spanning Tree Protocol, link aggregation, switch security and enterprise network design.
For additional study, learners should explore:
Ethernet switching
MAC address learning
VLANs
Trunking
Inter-VLAN routing
Port security
Spanning Tree Protocol
EtherChannel/link aggregation
Switch monitoring
Layer 3 switching
Network troubleshooting
Cisco's current introductory material explains Ethernet switches, MAC address learning, forwarding and the relationship between switches and routers.
More learning, practical demonstrations, instructor support and assessments for this topic will be delivered through Senior ICT Academy Campus, either by a physical instructor or an online instructor.
Campus:
https://campus.seniorictacademy.com/
Learners should use the Campus platform to access additional lessons, activities, assessments and instructor guidance.
Build or simulate a small switched network containing:
At least 3 computers
1 network switch
Ethernet cables
1 router or Internet gateway
Then:
Connect all computers to the switch.
Identify the MAC address of each computer.
Configure suitable IP addresses.
Test communication between the computers.
Identify the switch ports being used.
Examine the MAC address table if a managed switch is available.
Disconnect one device and observe the change.
Troubleshoot one deliberately introduced connectivity problem.
Document the final network.
Explain how the switch forwards traffic between the devices.
Expected outcome: The learner should be able to physically identify a switch, connect devices to it, explain how switching works, understand MAC address learning and troubleshoot basic switch connectivity problems.