Learning Objectives
At the end of this lesson student should be able to:
• Analyze network troubleshooting methodologies, including the OSI model and
Top-Down/Bottom-Up approaches, to identify and resolve network issues
effectively.
• Appreciate the importance of proactive troubleshooting in maintaining network
stability, ensuring user productivity, and minimizing security risks.
• Demonstrate the ability to simulate network troubleshooting scenarios using
virtual tools and software to diagnose and resolve issues in a controlled
environment.
2

Definition of terms:
 Network Troubleshooting:
The systematic process of identifying, isolating, and resolving issues that prevent
a network from functioning properly.
 OSI Model (Open Systems Interconnection Model):
A conceptual framework used to understand and implement standardized
network communication by dividing it into seven layers: physical, data link,
network, transport, session, presentation, and application.
 Top-Down Approach:
A troubleshooting methodology that starts with examining high-level network
issues and progressively works downward to specific devices or configurations. 3

 Bottom-Up Approach:
A troubleshooting methodology that begins with analyzing individual hardware and
device configurations, gradually moving toward broader network components.
 LAN (Local Area Network):
A network that connects devices within a limited geographical area, such as a building
or campus, allowing resource sharing and communication.
 WAN (Wide Area Network):
A network that spans a large geographical area, connecting multiple smaller networks
(e.g., LANs) over long distances, often using public or private telecommunication links.
 Virtual Private Network (VPN): is a network that encrypts data and masks
IP addresses to protect the user’s privacy and security.
4

 DHCP (Dynamic Host Configuration Protocol):
A network protocol that automatically assigns IP addresses to devices on a network,
simplifying device configuration.
 VLAN (Virtual Local Area Network):
A logical grouping of devices in a network, segmented to improve performance, security, and
manageability, without requiring changes to the physical network.
 Ping:
A network diagnostic tool used to test connectivity between devices by sending data packets
and measuring response time.
 Maintaining Quality of Service (QoS) is the use of mechanisms or technologies
that work on a network to control traffic and ensure the performance of critical
applications with limited network capacity. 5

 Traceroute:
A diagnostic tool that maps the path data packets take from the source to the
destination, helping identify delays or interruptions in the network.
 Remote Access Tools:
Software or protocols, such as SSH (Secure Shell), that allow administrators to access
and manage network devices from a remote location securely.
 Spanning Tree Protocol (STP):
A network protocol used in switches to prevent loops in a network by creating a
spanning tree structure.
 Network Latency:
The delay in data transmission over a network, often caused by distance, hardware
issues, or congestion, which impacts network performance. 6

What is Network Troubleshooting?
x
y
7

What is Network Troubleshooting?
Network troubleshooting is the systematic process of finding problems
that prevent network operation. It entails isolating and fixing these issues.
This procedure includes a variety of approaches and technologies.
Network engineers employ troubleshooting techniques to identify
connectivity issues. They also employ similar methods to detect and
correct slowdowns, hardware failures, and software misconfigurations.
8

Importance of Network
Troubleshooting
x
y
9

- A stable and efficient network is critical to company continuity. Network troubleshooting
is critical for keeping the network running smoothly.
- Resolving issues rapidly reduces downtime and ensures that company activities are not
impacted.
- A well-functioning network increases user productivity by enabling smooth
communication and application access.
- Proactive troubleshooting identifies possible security flaws before they are exploited.
- Efficient troubleshooting reduces the need for reactive maintenance and expensive fixes.
10

 Unable to connect to network resources,
printers, or the internet.
 Slow loading times, lagging programs,
and delayed video conferencing.
12

• Faulty network hardware, such as routers,
switches, or cables, can cause disruptions.
 Incorrect settings on network devices or operating systems might
cause connectivity difficulties.
13

Network Troubleshooting Methodologies
Network troubleshooting follows structured methodologies for efficient
problem-solving. Here are two fundamental approaches:
 Network Troubleshooting Models
 The Open System Interconnection (OSI) Model
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14

Network Troubleshooting Models
Network troubleshooting models provide a framework for
systematic diagnosis.
1. The Top-Down Approach begins with investigating broader
network issues. It then narrows down to specific devices.
2. The Bottom-Up Approach starts with identifying problems in
individual devices. It then advances toward the network core.
1
15

The Open System Interconnection (OSI) Model
The OSI model provides a layered foundation for network
communication. Issues can be investigated inside each tier. The
layers involved include physical, data connection, network,
transport, session, presentation, and application. Analyzing
difficulties inside each layer might help determine the cause of
the problem.
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16

Wireless Network
Troubleshooting
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LAN and WAN Troubleshooting
Understanding the specific challenges of Local Area Networks (LANs) and Wide
Area Networks (WANs) is crucial for effective troubleshooting.
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18

LAN troubleshooting focuses on difficulties inside a specific network (e.g., building,
campus). Common culprits include:
• Inspect and secure the Ethernet cables.
Local Area Network (LAN) Troubleshooting
Wireless Network Troubleshooting
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• IP conflicts detect and resolve duplicate IP addresses.
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20

• Checks subnet mask settings on network devices.
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21

• For DHCP server issues, check the DHCP server logs and settings.
• Reviews the switch port settings for VLAN membership and speed.
1
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WAN troubleshooting focuses on networks that are geographically scattered. Common
places to examine are:
Wide Area Network (WAN) Troubleshooting
• Contact your Internet service provider to rule out potential service outages if you
have ISP issues.
• Use ping and traceroute to detect network latency and packet loss.
• Checks VPN setup on both ends to verify adequate encryption protocols.
1
23

Router and Switch Configuration
Routers and switches are the heart of any network, channeling data
traffic effectively. The correct setup is critical for
optimal network performance. Here’s a look into the router and switch
configuration:
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24

Routers
Routers are responsible for routing traffic over several networks
(LANs and WANs). Its configuration involves
• Designing network routes
• Implementing security measures
• Maintaining Quality of Service (QoS)
• Switches
25

Switches
Switches enable communication between devices on a
network segment. The configuration focuses on creating VLANs
(Virtual LANs) to segment traffic. It also regulates port speeds and
security settings. Furthermore, it implements the Spanning Tree
Protocol (STP) for loop prevention.
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Remote Network Troubleshooting
Diagnosing networks is critical for managing networks or offering
remote assistance. Here’s how IT experts approach remote troubleshooting.
 Remote Access Tools
SSH (Secure Shell) allows for secure setup. Remote desktop apps provide secure access
for debugging network equipment.
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Remote Network Troubleshooting
 Troubleshooting Techniques
Pinging and traceroute are two techniques that can help discover faults in network
segments. Remote logging is another tool for troubleshooting difficulties.
 Communication and Documentation
Clear communication with end users is critical to effective problem resolution. Detailed
documentation of troubleshooting procedures is also required.
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1. It focuses on networks that are geographically scattered
2. It focuses on difficulties inside a specific network
3. It is the systematic process of finding problems that prevent network
operation.
4. Network troubleshooting model that provides a layered foundation for
network communication.
5. These are the heart of any network, channeling data traffic effectively.
Direction: This is a 3-minute identification quiz. Write the correct
answer for each question.
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31

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