How to Configure Cisco Router in GNS3 Basically

Before you add Cisco routers to the network, you perform some basic settings when setting up for the first time. For example, assigning an IP address or creating a new user.

How to Configure Cisco Router in GNS3 Basically

How to Configure a Cisco Router Basically

If you are running the Cisco Router for the first time, you will be presented with an automatic setup screen. You can also configure your device as a base with this automatic installation.

However, instead of using an automatic setup wizard, it is more convenient to configure your device with the CLI command prompt.

In addition, you can use SDM to configure a Router for the first time.

Basic Cisco Commands

Follow the steps below to configure Cisco Router.

   Step 1: Changing the Cisco Router Name

You can change the name of your router for the first step. To do this, you can use the Hostname command in your device’s config mode.

R1# configure terminal
R1(config)#hostname ISTANBUL
ISTANBUL(config)#exit
ISTANBUL#

 

   Step 2: Assigning an IP Address to the Router’s Interface

It is simple and easy to assign an IP address to the Interfaces of your Cisco network devices and turn on the corresponding port. In short, you can use the ip address (address) (subnet mask) command in config mode of the interface you configure.

Then use the no shutdown command to make the port available.

No shutdown command opens the closed interface. If you want to close the interface, you should only use the shutdown command.

ISTANBUL#conf t
ISTANBUL(config)#interface fastethernet 0/0
ISTANBUL(config-if)#ip address 192.168.8.1 255.255.255.0
ISTANBUL(config-if)#no shutdown
ISTANBUL(config-if)#exit
ISTANBUL(config)#exit
ISTANBUL#

 
Assigning an IP Address to the Router

   Step 3: Configuring Enable Password

You must set the Enable password to restrict or prevent unauthorized access to your router.

Enable Password sets a password when you switch to the Privileged Execute Mode at the router’s CLI command prompt.

You can use the enable password “password” command to set a password for the Cisco Router.

ISTANBUL#conf t
ISTANBUL(config)#enable password cisco123
ISTANBUL(config)#exit
ISTANBUL#disable
ISTANBUL>enable
Password:
ISTANBUL#

 
Remember to share the password you have created with only those authorized to configure the network.

When you look at the image below, you may see that a password is requested when you switch from user execute mode to privileged mode.

Preventing Unauthorized Access to the Router

When you run the show running-config command on your router, you can see from the following image that the enable password you created is visible.

Because passwords created with Enable Password send as cleartext, you can see the password in the show running-config. To prevent this, you must encrypt the password.

Enable Password

   Step 4: Configuring Enable Secret

You must use the Enable Secret command in the router’s config mode to encrypt the enable password that appears in the running-config.

If you enable it on your router, your Enable Password will be disabled!

ISTANBUL#
ISTANBUL#conf t
ISTANBUL(config)#enable secret cisco123456
ISTANBUL(config)#end
ISTANBUL#disable
ISTANBUL>enable
Password: ⇒ Burada cisco123 parolası denendi ve başarılı olmadı.
Password: ⇒ Burada cisco123456 parolası denendi ve başarılı olarak giriş yapıldı.
ISTANBUL#

 
You can use the following command in the CLI to disable the enable password command.

ISTANBUL(config)#no enable password

 
Enable Secret

You will see that your password was encrypted as shown in the image below, where you review the configuration of your Cisco Router again.

An Encrypted Password

   Step 5: Viewing a Message for Unauthorized Contacts

When an unauthorized user attempts to access your router, you can show the user a message.

This message informs the user that it is in unauthorized access, and does not interfere with any settings on the router.

In the Cisco Router, an unauthorized access message generates with the banner motd # command. The # character you see in the command is used to indicate the beginning and end of the message.

ISTANBUL#conf t
ISTANBUL(config)#banner motd # ⇒ After you enter #, press Enter.
Enter TEXT message. End with the character '#'.
***********************************************************************
***** WARNING ! ***** Unauthorized Access Prohibited ! *********
***********************************************************************#
ISTANBUL(config)#exit
ISTANBUL#

 
Unauthorized Access Message

After creating the banner message, when you switch to the start screen with the exit command on the router interface, you will see a message like the one shown below.

Unauthorized Access Message on Router

   Step 6: Closing CLI Notifications on the Cisco Router

Notifications will occur at the CLI prompt for actions you perform when configuring your Cisco Router. Sometimes you may need to turn off CLI notifications, as this may cause confusion.

These notifications from the Cisco router cause confusion when making adjustments. These notifications have no effect on the commands. It only causes complexity.

For example, when you close and open the FastEthernet interface, you will see a notification as shown in the image below.

You can use the logging synchronous command in global configuration mode to turn off these notifications on the Cisco Router.

Turning CLI Notifications Off

   Step 7: Turn off Domain Lookup on the Cisco Router

When you implement an invalid command on your router that may cause DNS resolution, you may not be able to operate on your router for a while.

If you have a DNS server on your network, and you have set up your router, this will not be a problem.

However, if there is no DNS server in the network environment, you can disable it by using the no ip domain-lookup command in config mode.

ISTANBUL#conf t
ISTANBUL(config)#no ip domain-lookup
ISTANBUL(config)#end
ISTANBUL#

 
Disabling Domain Search

   Step 8: Configuring the Router’s Console Interface

Before you can add your Cisco Router to your network, you must access your device through the Console connection to make settings for the first time.

A Rollover Cable is used to connect to the Cisco Router. One end of the rollover cable has an RJ-45 connection, and the other end has a DB-9 connection.

Rollover cable;

Rollover Cable

With this cable, you can access the Cisco Router for the initial configuration.

The RJ45 plugs into the console’s Console output. The DB9 connects to the serial port on the back panel of desktop computers. There are 2 types of DB-9 cable called male and female.

Rollover cable converters are also available. For example, you can convert the DB-9 to a USB port, and connect your laptop to a console.

Use the following commands to setup a password when connecting to your router’s console port.

ISTANBUL#conf t
ISTANBUL(config)#line console 0
ISTANBUL(config-line)#password cisco123
ISTANBUL(config-line)#login
ISTANBUL(config-line)#exit
ISTANBUL(config)#exit
ISTANBUL#

 
Router Console Connection

When you connect to the Cisco Router again through the console, you will first need to enter a password.

User Access Verification

   Step 9: Configuring Telnet

After you connect your router using a console cable, you must enable Telnet or SSH to manage your device from a local or remote network.

You must use the line vty 0 4 command in global configuration mode to provide management with the Telnet protocol.

ISTANBUL#
ISTANBUL#conf t
ISTANBUL(config)#line vty 0 4
ISTANBUL(config-line)#password cisco321
ISTANBUL(config-line)#login
ISTANBUL(config-line)#exit
ISTANBUL(config)#exit
ISTANBUL#

 
Telnet Connection

To access the Cisco Router via Telnet from any computer on the network using the Putty program, type the IP address of the interface and check Telnet in the “Connection Type:” section. Then click Open to connect.

Connecting to a Router with PuTTY

When you access the router via Telnet, you may see a message for unauthorized access from the following image.

Entering the Enable Password

After connecting with Telnet, you will see a notification on the router as follows.

ISTANBUL#
*Mar 1 04:12:11.218: %SYS-5-CONFIG_I: Configured from console by vty0 (192.168.8.128)
ISTANBUL#

 

   Step 10: Encrypting Passwords

You can use the service password-encryption command in the Global Configuration Mode if you want to encrypt all the passwords that you have created on your router.

ISTANBUL#conf t
ISTANBUL(config)#service password-encryption
ISTANBUL(config)#end
ISTANBUL#

 
Before encrypting the passwords;

Router Passwords Encryption

After encrypting the passwords;

Encrypted Password in Running-Config

How to Setup Cisco Router ⇒ Video

Temel Cisco konfigürasyonu yapmak için aşağıdaki videoyu izleyebilir ve ayrıca bize destek olmak için YouTube kanalımıza abone olabilirsiniz!

You can watch the video below for the basic Cisco configuration and also subscribe to our YouTube channel to support us!

   Final Word


In this article, we have examined the basic settings of a Cisco Router using the Graphical Network simulator. Thanks for following us!

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Enable SSH
♦ Interface Settings
Enable DHCP
Backup Router Config

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