Part 3 – Configure the Routers


Part 3 – Configure the Routers

Objective

In this lesson, you'll configure both routers so they can communicate with their local networks.

By the end of this lesson, you will:

  • ✅ Access the router CLI

  • ✅ Change the router name

  • ✅ Configure Ethernet interfaces

  • ✅ Assign IP addresses

  • ✅ Enable the interfaces

  • ✅ Save the configuration

Note: We are not configuring routing yet. That will be covered in Part 4.

Step 1: Open Router A

Where to do it

In the Packet Tracer workspace:

  1. Click Router A.

  2. Click the CLI tab.

If prompted with:

Would you like to enter the initial configuration dialog? [yes/no]:

Type:

no

Press Enter.

If you see:

Press RETURN to get started!

Press Enter.

What is the CLI?

CLI stands for Command Line Interface.

It allows you to configure the router by typing commands.

Why do we use the CLI?

Professional network engineers configure Cisco routers through the CLI because it provides complete control over the device.

🌍 Real-Life Example

When a new Cisco router is installed in an office, the network engineer usually connects a laptop to the router and performs the initial setup through the CLI.

What should you see?

Router>

Step 2: Enter Privileged EXEC Mode

Where to do it

At the Router> prompt.

Type:

enable

Press Enter.

What does enable do?

It changes the prompt from:

Router>

to

Router#

This is called Privileged EXEC Mode.

Why do we use it?

Without entering Privileged EXEC Mode, you cannot configure the router.

Think of it as unlocking administrator privileges.

🌍 Real-Life Example

Imagine entering an office building.

Anyone can enter the reception area.

But only authorized staff can enter the server room.

The enable command gives you access to the "server room" of the router.

What should you see?

Router#

Step 3: Enter Global Configuration Mode

Where to do it

Type:

configure terminal

or

conf t

What does this command do?

It opens Global Configuration Mode.

The prompt changes to:

Router(config)#

Why do we use it?

This is where you make changes to the router, such as:

  • Hostname

  • Passwords

  • Interfaces

  • Routing

🌍 Real-Life Example

Imagine entering the control room of a company where you can change settings for the entire building.

Global Configuration Mode is the control room for the router.

What should you see?

Router(config)#

Step 4: Change the Hostname

Where to do it

At:

Router(config)#

Type:

hostname R1

What is a hostname?

A hostname is the name of the router.

Why do we change it?

If you have two routers named "Router," it becomes confusing.

Naming them R1 and R2 makes it easier to identify which router you're working on.

🌍 Real-Life Example

Think of two office buildings.

Instead of calling both "Office," one is named Head Office and the other Branch Office.

The names help everyone know which location they're referring to.

What should you see?

The prompt changes from:

Router(config)#

to

R1(config)#

Step 5: Configure the Interface Connected to the Switch

Where to do it

Type:

interface gigabitethernet0/0

(If your router uses a different interface name, use the correct one, such as gigabitethernet0/0/0. You can check with show ip interface brief later.)

What is an interface?

An interface is a physical network port on the router where a cable is connected.

Why are we selecting GigabitEthernet0/0?

Because this is the interface connected to Switch A.

We are about to configure the router's connection to Network A.

🌍 Real-Life Example

Think of a building with multiple doors.

Each door leads to a different area.

An interface is like one of those doors—it connects the router to a specific network.

What should you see?

R1(config-if)#

Step 6: Assign an IP Address

Where to do it

Inside the interface configuration mode.

Type:

ip address 192.168.1.1 255.255.255.0

What does this command do?

It assigns an IP address to the router's interface.

Why do we need it?

Every device on a network needs an IP address.

This IP address becomes the Default Gateway for all the computers in Network A.

🌍 Real-Life Example

Imagine the main gate of an estate.

Everyone leaving the estate goes through that gate.

The router's interface is that main gate for the computers on the network.

What should you see?

The command is accepted without an error message.

Step 7: Enable the Interface

Where to do it

Still inside the interface configuration mode.

Type:

no shutdown

What does no shutdown mean?

Cisco router interfaces are disabled by default.

This command turns the interface on.

Why do we use it?

Without it, the interface remains administratively down, even if the cable is connected.

🌍 Real-Life Example

Imagine building a brand-new road but keeping the entrance gate locked.

Cars cannot use the road until the gate is opened.

no shutdown unlocks the gate.

What should you see?

A message similar to:

%LINK-5-CHANGED: Interface GigabitEthernet0/0, changed state to up

Step 8: Save Your Work

Where to do it

Return to Privileged EXEC Mode:

end

Then type:

copy running-config startup-config

Press Enter to accept the default filename.

What is the Running Configuration?

The running configuration is the current configuration stored in the router's memory.

If the router loses power before you save it, those changes are lost.

What is the Startup Configuration?

The startup configuration is the saved configuration stored in non-volatile memory.

The router loads it automatically every time it starts.

🌍 Real-Life Example

Think of writing a report on your computer.

While you're typing, the report is open and unsaved.

If the computer shuts down unexpectedly, your work may disappear.

When you click Save, the file is stored on your drive and is available the next time you open your computer.

The router works the same way:

  • Running configuration = your unsaved work.

  • Startup configuration = your saved work.

Part 3 Summary

You have successfully:

  • ✅ Opened the CLI.

  • ✅ Entered Privileged EXEC Mode.

  • ✅ Entered Global Configuration Mode.

  • ✅ Changed the router's hostname.

  • ✅ Configured the LAN interface.

  • ✅ Assigned an IP address.

  • ✅ Enabled the interface with no shutdown.

  • ✅ Saved the configuration.

Before moving to Part 4

Repeat the same process on Router B, but use:

  • Hostname: R2

  • LAN Interface IP: 192.168.2.1/24

In Part 4, you'll configure the router-to-router Ethernet connection and then add static routing so devices in Network A can communicate with devices in Network B. This keeps the concepts separate and easier to understand.

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