Day-19: Introduction To Cisco IOS.

By | June 6, 2022

Cisco IOS (Internetwork Operating System) is the software used on a majority of Cisco Systems routers and switches. IOS consists of routing, switching, internetworking, and telecommunications functions in a multitasking operating system.

Most Cisco devices (including routers and switches) use a CLI (Command Line Interface) to configure the network device. The CLI is an interface, based on text. You type in configuration commands and use show commands to get the output from the router or switch. There are also GUIs (Graphical User Interface) for the routers, switches, and firewalls but the majority of the work is done on the CLI.
CLI is much easier to work with than any of the graphical interfaces.

How We Can Access the CLI of Cisco Devices?

There are 3 ways to access the CLI of a cisco device.

1-Console.
2-Telnet.
3-SSH.

1. Console

By using the console cable we can access the cisco devices CLI. So to access the device through the console port we must have a console cable that must be connected between your computer and the devices (Switches, Routers, Firewalls, etc ).

Nowadays most laptops and desktops have no serial port so you cant connect the serial cable to your laptop and desktops. Instead of using the serial connector for your PC, you can use a cable that is a serial to USB converter cable .

2-Telnet.

Telnet is a protocol that provides a command-line interface for accessing and managing the remote device or server. To access a cisco device through Telenet you must have an IP address configured in that device and by default, Telenet is not configured so you have to access the devices through the console port for doing the initial configuration such, as IP address configuration, Gateway configuration etc.

Once you will complete the initial configuration you can access that device remotely by using the Telenet protocol.

Telenet is not secure but there is another protocol called STELNET which you can use in a secure manner.

3-SSH.

SSH(Secure Shell ) is a protocol that is also used for accessing and managing the remote device or server. To access a cisco device through SSH you must have an IP address configured in that device and by default, the SSH is not configured so you have to access the devices through the console port for doing the initial configuration such, as IP address configuration, Gateway Configurations etc.

Once you will complete the initial configuration you can access that device remotely by using the SSH protocol.

SSH is more secure and it is used in production networks for accessing and managing the devices remotely.

Applications for accessing & Managing through CLI.

When you are accessing the CLI of a Cisco device through Console cable or SSH or Telenet, You need an application where you can run the command and view the output etc .

I personally prefer putty, But here are the few well-known terminals accessing software given below.

1-Putty.
2-Hyper Terminal.
3-Secure CRT .

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