Part 6 – Test the Network

 

Part 6 – Test the Network

Objective

In this lesson, you'll test the network to confirm that all devices can communicate correctly.

By the end of this lesson, you will:

  • ✅ Test communication within the same LAN.

  • ✅ Test communication between different LANs.

  • ✅ Use the ping command.

  • ✅ Use the Simple PDU tool.

  • ✅ Understand how to interpret the results.

Step 1: Why Do We Test the Network?

Why is testing important?

After building and configuring a network, we need to confirm that everything works as expected.

Testing helps us identify mistakes before users start using the network.

🌍 Real-Life Example

Imagine an electrician installs all the wiring in a new house.

Before the family moves in, they switch on the lights to make sure everything works.

Network engineers do the same thing by testing the network before handing it over to users.

Step 2: Test Communication Within the Same Network

Where to do it

Click PC1.

Go to:

Desktop → Command Prompt

What is Command Prompt?

The Command Prompt allows you to type network commands to test and troubleshoot connectivity.

What to do

Type:

ping 192.168.1.11

Press Enter.

What does ping mean?

ping sends small test messages called ICMP Echo Requests to another device.

If the other device receives the message, it replies with an ICMP Echo Reply.

Why are we pinging PC2?

PC1 and PC2 are connected to the same switch.

This confirms that the local network (LAN) is working correctly.

🌍 Real-Life Example

Imagine calling your colleague sitting in the next office.

If they answer, you know your internal office phone system is working.

A ping works the same way—it checks whether another device can respond.

What should you see?

Reply from 192.168.1.11

or

Success rate is 100%

Step 3: Test Communication Between Different Networks

Where to do it

Stay on PC1.

Open the Command Prompt.

What to do

Type:

ping 192.168.2.12

Press Enter.

Why are we doing this?

This checks whether:

  • Router A

  • Router B

  • Static Routes

are all working correctly.

🌍 Real-Life Example

Imagine sending an email from the Abuja office to someone in the Lagos office.

If the email arrives, you know the two offices are connected.

The ping command performs the same test.

What should you see?

Reply from 192.168.2.12

or

Success rate is 100%

If you receive a reply, both LANs can communicate.

Step 4: Use the Simple PDU Tool

Where to do it

Look at the bottom-right corner of Packet Tracer.

Click the Simple PDU tool (the envelope icon).

What is a Simple PDU?

A Protocol Data Unit (PDU) represents the data sent across a network.

The Simple PDU tool sends a test packet from one device to another and visually shows the path it takes.

What to do

  1. Click the Simple PDU tool.

  2. Click PC1 (source).

  3. Click PC6 (destination).

Why do we use Simple PDU?

Unlike the ping command, the Simple PDU lets you see the packet traveling through the network graphically.

This helps you understand how data moves between devices.

🌍 Real-Life Example

Think of tracking a parcel online.

You can see it move from:

  • Local office

  • Regional warehouse

  • Delivery center

  • Your home

Simple PDU does the same thing for network packets.

What should you see?

The packet should travel:

PC1
   │
Switch A
   │
Router A
   │
Router B
   │
Switch B
   │
PC6

A green check mark indicates success.

Step 5: Test from Network B to Network A

Where to do it

Open PC6.

Go to:

Desktop → Command Prompt

What to do

Type:

ping 192.168.1.10

Press Enter.

Why do this test?

Communication should work in both directions.

Testing from Network B back to Network A confirms that both routers have the correct routes.

🌍 Real-Life Example

If a phone call works from Abuja to Lagos, you also want to confirm that someone in Lagos can call Abuja.

Networking works both ways.

Step 6: Understand the Results

If the Ping is Successful

You might see:

Reply from 192.168.2.12

or

Success rate is 100%

What does it mean?

  • The physical connections are correct.

  • The PCs have the correct IP settings.

  • The router interfaces are configured.

  • The static routes are working.

Your network is functioning properly.

If the Ping Fails

You might see:

Request timed out.

or

Destination host unreachable.

What does it mean?

Something is preventing the packet from reaching its destination.

This is normal during troubleshooting and simply means you need to check your configuration.

🌍 Real-Life Example

Imagine sending a parcel that gets returned because the address was wrong or the road was blocked.

The parcel didn't arrive—not because parcels don't work, but because something along the route needs to be corrected.

Network packets behave the same way.

Step 7: Celebrate Your Success

If:

  • ✅ PC1 can ping PC2,

  • ✅ PC1 can ping PC6,

  • ✅ PC6 can ping PC1,

  • ✅ The Simple PDU succeeds,

then you've successfully built and configured a working network.

Part 6 Summary

You have learned how to:

  • ✅ Test devices using the ping command.

  • ✅ Verify communication within the same LAN.

  • ✅ Verify communication between different LANs.

  • ✅ Use the Simple PDU tool to visualize packet movement.

  • ✅ Understand what successful and failed test results mean.

Next Lesson: Part 7 – Troubleshoot Common Network Problems

In the final part, you'll learn how to diagnose and fix common issues, such as:

  • Wrong IP address

  • Incorrect subnet mask

  • Wrong default gateway

  • Missing no shutdown

  • Incorrect static routes

  • Wrong cable type

  • Interface down/down or administratively down

  • Using show commands to quickly identify problems like a network engineer.

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