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
Star topology is one of the most commonly used network topologies in modern Local Area Networks (LANs).
In a star topology, network devices are connected individually to a central networking device. The central device is commonly a network switch, although hubs and wireless access points can also form the centre of a star-shaped network.
A typical star network can contain:
Computers
Network printers
Servers
IP phones
Wireless access points
CCTV cameras
Other network devices
Each device normally has its own connection to the central device.
For example:
Computer 1 →
Computer 2 →
Computer 3 → Switch
Computer 4 →
Printer →
The switch is at the centre of the physical arrangement.
Star topology is widely used because it is relatively easy to install, expand, manage and troubleshoot. Modern Ethernet LANs commonly use a physical star arrangement.
By the end of this lesson, the learner should be able to:
Define star topology.
Explain how star topology works.
Identify the main components of a star network.
Explain the role of the central switch.
Describe how data travels in a star network.
Identify different types of star topology.
Explain the advantages of star topology.
Explain the disadvantages of star topology.
Compare star topology with bus, ring and mesh topologies.
Explain the difference between a physical and logical topology.
Design a simple star network.
Identify common star-network faults.
Perform basic troubleshooting.
Build a simple star network using physical equipment or a network simulator.
Network topology refers to the arrangement or structure of devices and connections within a computer network.
It describes how devices such as computers, switches, routers and printers are connected.
Common network topologies include:
Bus
Star
Ring
Mesh
Tree
Hybrid
The choice of topology can affect network cost, reliability, expansion, performance and troubleshooting.
A star topology is a network arrangement in which individual network devices connect to a central networking device.
The central device may be:
Switch
Hub
Wireless access point
In modern Ethernet networks, switches are the most common central devices.
A simple structure is:
Computer 1
|
|
Computer 2 ---- Network Switch ---- Computer 3
|
|
Network Printer
Each device has an individual connection to the central device.
A star network may contain:
Central switch
Computers
Network cables
Network interface cards
Servers
Network printers
Routers
Wireless access points
IP phones
Network cameras
Patch panels
Network racks
The switch is normally the most important component in a modern wired star topology.
It provides multiple ports through which devices can connect.
For example, a 24-port switch can provide connections for multiple computers, printers, access points and other devices.
The switch receives Ethernet frames and uses MAC addresses to determine where frames should be forwarded.
Unlike a traditional hub, a switch can normally forward a frame toward the appropriate destination port rather than blindly repeating it to every port.
One important characteristic of star topology is that each end device normally has its own connection to the central device.
For example:
PC 1 → Cable 1 → Switch
PC 2 → Cable 2 → Switch
PC 3 → Cable 3 → Switch
PC 4 → Cable 4 → Switch
This makes it easier to identify which connection belongs to a particular device.
Suppose Computer A wants to send a file to Computer B.
The process can be simplified as follows:
Computer A creates the network data.
The data is placed into an Ethernet frame.
The frame travels through Computer A's network cable.
The frame reaches the central switch.
The switch examines the destination MAC address.
The switch determines the appropriate destination port.
The switch forwards the frame toward Computer B.
Computer B receives the frame.
The central switch therefore plays an important role in communication.
Consider a computer laboratory containing:
30 student computers
2 instructor computers
1 network printer
1 server
1 wireless access point
A central 48-port switch could connect the devices.
The arrangement would be:
Server
|
|
PC 1 -------- |
PC 2 -------- |
PC 3 -------- |
PC 4 -------- Switch -------- Printer
PC 5 -------- |
PC 6 -------- |
|
Access Point
This is a practical example of star topology.
An office may have:
Reception computer
Finance computers
Human resource computers
Manager's computer
Network printer
Server
Wireless access point
All of these devices can connect to a central switch.
The switch may then connect to a router for Internet and WAN connectivity.
A training centre could have:
Student computers
Trainer computers
Administrative computers
Printers
Servers
Access points
A central switch can provide the physical star structure.
VLANs can then be used to logically separate different groups.
For example:
VLAN 10 – Administration
VLAN 20 – Trainers
VLAN 30 – Students
Therefore, physical topology and logical network design can work together.
Modern Ethernet LANs commonly use a star physical topology.
For example, computers can use Ethernet cables to connect to a switch.
Common Ethernet cables include:
Cat5e
Cat6
Cat6A
Each cable generally runs from an end device to a switch or another appropriate network device.
A wireless access point can also act as the centre of a wireless star-like arrangement.
For example:
Laptop
|
|
Laptop ---- Wireless AP ---- Smartphone
|
|
Tablet
The wireless devices communicate through the access point.
This demonstrates that star-like arrangements are not limited to cables.
Physical topology refers to the actual physical arrangement of network devices and cables.
In a physical star:
A central device exists.
Individual connections extend from the centre.
Devices do not normally share one continuous backbone cable.
Modern switched Ethernet networks commonly have this physical arrangement.
Logical topology describes how data flows through a network.
The physical arrangement and logical behaviour are related but are not always identical.
For example, an old Ethernet network using a hub could physically look like a star because all cables connect to a central hub, but the hub repeats traffic across its ports.
A modern Ethernet switch provides more intelligent forwarding.
Therefore, learners should understand the difference between:
Physical topology = how devices are physically connected.
Logical topology = how data moves through the network.
Older star networks sometimes used hubs.
A hub receives a signal and repeats it to its other ports.
This means devices connected through the hub may see traffic that was transmitted by other devices.
Hubs are now largely obsolete in modern Ethernet networks.
Modern star networks normally use switches.
A switch can learn which MAC addresses are associated with which ports.
For example:
| MAC Address | Switch Port |
|---|---|
| MAC-A | Port 1 |
| MAC-B | Port 2 |
| MAC-C | Port 3 |
If a frame destined for MAC-B arrives on Port 1, the switch can forward it toward Port 2.
This improves network efficiency compared with a traditional hub.
An extended star topology is created when additional switches are connected to a central switch.
For example:
Core Switch
/ | \
/ | \
Switch 1 Switch 2 Switch 3
/ | \ / | \ / | \
PCs PCs PCs PCs PCs PCs PCs
This design is common in larger networks.
For example:
Core switch
Distribution switches
Access switches
End devices
Larger networks can use multiple levels of switches.
For example:
Core Layer
↓
Distribution Layer
↓
Access Layer
↓
End Devices
This creates a larger star-like or hierarchical structure.
Such designs are common in enterprise networks.
One major advantage of star topology is that new devices can generally be added without redesigning the entire network.
For example, if an office has an unused switch port, a new computer can be connected using an Ethernet cable.
The network administrator can then configure:
IP address
VLAN
Authentication
Network permissions
The existing devices can continue operating.
If the existing switch has no available ports, another switch can be added.
For example:
Main Switch → Additional Switch
The additional switch can provide more ports.
This creates an extended star topology.
Star networks are relatively straightforward to install because each device has a dedicated connection to the central device.
If one computer stops working, the technician can inspect:
Computer
Network interface
Cable
Switch port
The fault is often easier to isolate.
If the cable connecting PC 5 to the switch fails, PC 5 may lose network connectivity while the other computers continue operating.
This is a major advantage over some older shared-cable designs.
New devices can be connected to available switch ports.
The central switch provides a convenient location for network administration.
Switched Ethernet can provide efficient communication because the switch can forward frames toward appropriate ports.
Network administrators can often identify the affected switch port or cable when a single device loses connectivity.
The biggest disadvantage is dependence on the central device.
If the main switch fails, many or all devices connected to that switch may lose network connectivity.
Therefore, the central switch can represent a potential single point of failure.
A separate cable is normally required between each end device and the central switch.
This can require more cabling than a bus arrangement.
The network requires a central switch and sufficient ports.
Large networks may require multiple switches.
Switches require electrical power.
A power failure affecting the switch can interrupt network connectivity.
Because many devices depend on the switch, the switch must be properly protected, configured and maintained.
| Feature | Star | Bus |
|---|---|---|
| Central device | Yes | No |
| Main connection | Individual links | Shared backbone |
| Troubleshooting | Easier | More difficult |
| Expansion | Easier | More difficult |
| Cable failure | Usually affects one device | Can affect wider network |
| Central device failure | Major impact | No central switch |
| Modern use | Very common | Mostly historical |
| Feature | Star | Ring |
|---|---|---|
| Structure | Central device | Circular connection |
| Central device | Yes | Normally no central switch |
| Expansion | Relatively easy | Can be more complex |
| Fault isolation | Easier | Can be more difficult |
| Common modern LAN use | Very common | Less common |
| Main weakness | Central device | Ring/link failure depending on design |
| Feature | Star | Mesh |
|---|---|---|
| Connections | Device to central device | Multiple device-to-device links |
| Cost | Lower | Higher |
| Cabling | Moderate | High |
| Redundancy | Depends on design | High |
| Complexity | Lower | Higher |
| Scalability | Good | More difficult as nodes increase |
| Common use | LANs | High-redundancy networks |
A tree topology can be considered an extended hierarchical structure based on multiple star arrangements.
For example:
Core
/ \
Switch Switch
/ \ / \
PCs PCs PCs PCs
The structure resembles a tree because multiple branches extend from higher-level devices.
Star topology works well with VLANs.
For example, one switch can support:
VLAN 10 – Administration
VLAN 20 – Staff
VLAN 30 – Students
VLAN 40 – Guests
The physical network remains star-shaped while the logical network is divided into multiple VLANs.
A star network can connect to a router.
For example:
Internet
|
Router
|
Switch
/ | \
PC1 PC2 PC3
The switch provides local connectivity while the router provides connectivity to other networks.
Security measures can be applied to a star network through:
VLANs
Port security
Authentication
Firewalls
Access control
Network monitoring
Strong passwords
Secure switch management
Disabling unused ports
A central switch provides a useful point for implementing some network controls.
Port security can be used on supported switches to restrict which devices are allowed to use particular ports.
For example:
Port 1 → Assigned to PC 1
The administrator may configure the switch to allow only an authorised MAC address or a defined set of devices.
This can help prevent unauthorised devices from connecting.
Star networks can contain many cables.
Good cable management is therefore important.
A professional installation should use:
Patch panels
Cable labels
Cable trays
Cable ties or appropriate management systems
Network racks
Proper cable routing
Each cable should be labelled at both ends where appropriate.
A network rack can contain:
Switches
Patch panels
Routers
Firewalls
UPS
Cable management equipment
A well-organised rack makes maintenance easier.
A computer laboratory may use:
24-port or 48-port switch
Cat6 cables
Patch panel
Network rack
Router
Wireless access point
Computers
Printer
Each computer connects to the central switching infrastructure.
An office may have:
Desktop computers
Laptops
Network printers
IP phones
Access points
Servers
These devices can connect to one or more central switches.
A small business might have:
10 computers
1 server
2 printers
1 access point
1 router
A single 24-port switch may provide the central connection point.
This is a simple and practical star network.
Common problems include:
Failed network cable
Loose RJ45 connector
Failed switch port
Failed switch
Power failure
Incorrect VLAN assignment
Incorrect IP configuration
Faulty NIC
Damaged patch panel port
Network loop
Incorrect switch configuration
If one computer cannot access the network:
Check whether the computer is powered on.
Check the network cable.
Check the RJ45 connectors.
Check the switch port.
Check link/activity lights.
Check the NIC.
Check the IP configuration.
Check the VLAN assignment.
Test another cable.
Test another switch port.
If many devices lose connectivity:
Check the central switch.
Check switch power.
Check the UPS.
Check uplink cables.
Check router connectivity.
Check VLAN configuration.
Check network loops.
Check for switch failure.
Check upstream network connectivity.
If all devices fail at approximately the same time, the central equipment should be one of the first areas investigated.
Learners should inspect a computer laboratory or office network.
Identify:
Central switch
Computers
Cables
Printers
Access points
Router
Patch panel
Determine whether the physical arrangement represents a star topology.
Using a switch, connect:
Three computers
One printer
One router
Assign appropriate IP addresses.
Test communication between the computers.
Disconnect the cable connecting one computer to the switch.
Ask learners to:
Identify the affected computer.
Determine whether other computers remain connected.
Replace or reconnect the cable.
Test connectivity again.
This demonstrates one of the major advantages of star topology.
Disconnect the central switch from power.
Observe what happens to the connected devices.
Discuss why the central switch is considered a critical component and potential single point of failure.
Design a network for:
30 student computers
5 teacher computers
5 administrative computers
2 printers
2 access points
1 server
Your diagram should show:
Central switch
Individual device connections
Router
Internet connection
Server
Printers
Wireless access points
Using Cisco Packet Tracer or another network simulator:
Add one switch.
Add five PCs.
Connect each PC to the switch.
Configure IP addresses.
Test connectivity.
Disconnect one PC.
Test the remaining PCs.
Explain your observations.
What is network topology?
Define star topology.
What is normally used as the central device in a modern star network?
How does a switch forward data?
What happens when one cable connecting a computer to the switch fails?
What happens when the central switch fails?
State five advantages of star topology.
State four disadvantages of star topology.
What is an extended star topology?
What is the difference between physical and logical topology?
How does star topology support network expansion?
Why is cable management important in a star network?
How can VLANs be used in a star network?
Compare star topology with bus topology.
Compare star topology with mesh topology.
Why is a switch better suited to modern star networks than a hub?
What is port security?
Identify five common faults in a star network.
How would you troubleshoot a computer that cannot connect to the network?
Why is the central switch considered a critical component?
Design a star topology for a computer training centre containing:
40 student computers
5 instructor computers
5 administrative computers
3 network printers
3 wireless access points
2 servers
1 router
Your assignment should include:
A labelled network diagram.
Central switches.
Cable connections.
IP addressing.
VLANs.
Router connection.
Internet connection.
Server connections.
Printer connections.
Security measures.
Backup power.
Explanation of how the network can be expanded.
Star Topology – Network topology in which devices connect to a central device.
Central Device – Device at the centre of a star network, usually a switch.
Switch – Network device that forwards Ethernet frames between ports.
Hub – Older central networking device that repeats signals to multiple ports.
Node – A device connected to a network.
Link – A connection between two network devices.
Extended Star – A star network expanded by connecting additional switches.
Physical Topology – Physical arrangement of network devices and cables.
Logical Topology – The way data logically flows through a network.
Port – Connection point on a networking device.
Patch Panel – Device used to organise and terminate network cables.
Network Rack – Cabinet or frame used to house network equipment.
Star topology is a network arrangement in which devices connect to a central networking device.
Modern wired Ethernet networks commonly use switches as the central devices.
Major advantages include:
Easy installation
Easy troubleshooting
Easy expansion
Centralised management
Isolation of individual cable failures
Good performance with switched Ethernet
The major disadvantage is that the central switch can become a single point of failure for devices connected to it.
Star topology can be extended by connecting additional switches and can work together with:
VLANs
Routing
Wireless access points
Servers
Firewalls
Internet connections
Understanding star topology is important because it forms the foundation of many modern LAN installations.