LAN and WAN

Introduction to LAN and WAN

Computer networks can be classified in different ways. One common
classification is based on the geographical area covered by the network.
Two important network types are the Local Area Network (LAN)
and the Wide Area Network (WAN).

Understanding LAN and WAN is important for cyber security because security
controls, network architecture, monitoring, access policies, and potential
attack surfaces can differ depending on how a network is designed.

What Is a LAN?

A Local Area Network (LAN) is a network that connects devices
within a relatively limited geographical area.

Examples include:

• A home network
• A school computer laboratory
• A university department
• A company office
• A computer training centre
• A single building

A LAN normally allows connected devices to communicate with one another and
share resources such as printers, files, applications, and internet access.

Example of a LAN

Imagine a Dwallnet training centre containing:

• 20 student computers
• 2 instructor computers
• 1 network printer
• 1 local server
• 1 network switch
• 1 wireless access point
• 1 router

The computers can connect to the switch using Ethernet cables or to the
wireless access point through Wi-Fi. Together, these devices form a local
network.

Student PC 1 ----\
Student PC 2 -----\
Student PC 3 ------> Switch ---- Server
Student PC 4 -----/     |
                       |
                       +---- Printer
                       |
                       +---- Wireless Access Point

Characteristics of a LAN

• Usually covers a relatively small geographical area.
• Often provides high-speed communication between local devices.
• Can be privately managed by an individual or organization.
• Commonly uses Ethernet and Wi-Fi technologies.
• Allows local resource sharing.
• Can be protected using authentication, segmentation, firewalls, and access controls.

What Is a WAN?

A Wide Area Network (WAN) connects networks across large
geographical areas.

A WAN may connect:

• Different offices in the same city
• Branches in different states
• Organizations in different countries
• Data centres in different regions
• Cloud infrastructure across geographical locations

WAN connectivity can use technologies and services provided by
telecommunications companies, internet service providers, private network
providers, and cloud networking platforms.

Example of a WAN

Consider an organization with offices in:

• Agbor
• Asaba
• Benin City
• Lagos

Each office may have its own LAN. A WAN can connect these separate LANs so
authorized users and systems can communicate between locations.

        OFFICE A
          LAN
           |
           |
        Router
           |
           |
       WAN LINK
           |
           |
        Router
           |
          LAN
        OFFICE B

LAN vs WAN

LAN Devices

Switch

A switch connects devices within a LAN and forwards traffic toward the
appropriate destination.

Wireless Access Point

A wireless access point provides wireless access to the LAN.

Router

A router can connect the LAN to other networks, including a WAN or the
internet.

Network Interface Card

A network interface provides a device with the ability to communicate over
the network.

WAN Devices

WAN infrastructure commonly involves routers and other network equipment
designed to connect separate networks.

Depending on the architecture, WAN connections can use:

• Internet connections
• Leased connections
• Virtual Private Networks (VPNs)
• Cloud networking services
• Mobile network services
• Dedicated private network services

LAN Security

A LAN should not automatically be considered safe simply because it is
internal.

An attacker who gains access to a local network may attempt to:

• Discover other devices
• Capture network traffic
• Attack vulnerable systems
• Steal credentials
• Spread malware
• Move laterally between systems

Security controls for LANs may include:

• Strong authentication
• Network segmentation
• Access control
• Secure Wi-Fi configuration
• Endpoint protection
• Firewalls
• Network monitoring
• Regular software updates

WAN Security

WAN connections can expose organizations to communication risks across
multiple locations and service providers.

Security measures may include:

• Site-to-site VPNs
• Encryption
• Firewalls
• Authentication
• Access control policies
• Network segmentation
• Monitoring and logging

LAN Segmentation

Network segmentation divides a larger network into smaller logical or
physical sections.

For example, a company could separate:

• Staff computers
• Guest Wi-Fi
• Servers
• Security systems
• Printers
• Management devices

Segmentation can limit unnecessary communication between systems and can help
reduce the impact of a compromised device.

Guest Network Example

Suppose a company provides Wi-Fi to visitors.

Instead of allowing visitors to connect directly to the internal staff
network, the organization can create a separate guest network.

                    Internet
                       |
                     Router
                       |
                    Firewall
                   /        \
                  /          \
           Staff Network    Guest Network
                |                 |
             Servers           Visitors
             PCs               Phones

This design helps separate visitors from sensitive internal resources.

LAN, WAN and the Internet

The internet is not simply one LAN. It is a global system of interconnected
networks.

An organization may have several LANs that connect through WAN infrastructure
and eventually communicate with systems on the internet.

Office LAN
     |
   Router
     |
   WAN / ISP
     |
 Internet
     |
 Web Server

Performance Concepts

Bandwidth

Bandwidth represents the capacity available for transferring data.

For example, a connection described as 100 Mbps has a nominal capacity of
100 megabits per second under the relevant conditions.

Latency

Latency describes the time required for data to travel between endpoints.
Long-distance WAN connections can have greater latency than communication
between devices on the same local network.

Packet Loss

Packet loss occurs when transmitted packets fail to reach their destination.
Excessive packet loss can result in poor application performance and
communication failures.

LAN and WAN in Cyber Security

Security analysts need to understand whether suspicious activity occurs inside
a LAN, between organizational locations, or across an internet connection.

For example, unusual traffic between two internal computers may require a
different investigation from suspicious traffic leaving an organization’s
network for an external destination.

Practical Scenario

A company has three offices. Each office contains its own LAN. The offices
must communicate with one another securely.

Consider the following architecture:

Office A LAN
     |
   Router
     |
     +-------------------+
                         |
                      WAN/VPN
                         |
     +-------------------+
     |
   Router
     |
Office B LAN

Questions for the security analyst:

1. Which networks are local?
2. Which connection links the offices?
3. Where should traffic filtering occur?
4. How can communication between the offices be protected?
5. Which logs should be monitored?

Basic Troubleshooting Thought Process

When a user cannot access a network resource, identify where the communication
path fails.

A basic sequence might be:

1. Check whether the device has network connectivity.
2. Check the network interface.
3. Check the device’s IP configuration.
4. Test communication with the local gateway.
5. Test communication with another known device.
6. Check whether the destination service is available.
7. Check routing and firewall rules.
8. Check relevant network logs.

Troubleshooting should be performed systematically rather than changing many
network settings at the same time.

Cyber Security Practice

Only perform network scanning, traffic analysis, configuration changes, or
security testing on systems that you own or have explicit authorization to
test.

For this course, students should use a controlled laboratory environment when
practicing network security techniques.

Practical Exercise

Create a simple network diagram for a small cyber security training centre.
Include:

• Five computers
• One server
• One switch
• One router
• One firewall
• One wireless access point
• Internet connection

Label which portion represents the LAN and which connection represents the
WAN or internet-facing path.

Lesson Summary

A LAN connects devices across a relatively limited geographical area, while a
WAN connects networks across larger geographical distances.

LANs commonly use switches, Ethernet, and Wi-Fi. WAN communication commonly
uses routers and connectivity services that link separate networks.

For cyber security professionals, understanding the difference between local
and wide-area communication is important when analyzing network traffic,
designing security controls, investigating incidents, and troubleshooting
connectivity problems.