CHAPTER 1
1.2 Classify Network Protocols and Communication

The purpose of the Cisco IOS.

✅Operating system the Cisco Internetwork Operating
System
or Cisco IOS.


✅The embedded software architecture in all of the Cisco routers and is also the operating system of the Catalyst Switches.

The Cisco IOS provides the following network services:

Reliable and secure access to networked resources

Basic routing and switching functions

Network Scability

OPERATING SYSTEM
⭐ALL electronic devices require an Operating System


  1. Windows, Mac, and Linux for PCs and laptops


  2. Apple iOS and Android for smart phones and tablets


  3. Apple iOS and Android for smart phones and tablets

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OS SHELL
• The OS shell is either a command-line interface (CLI) or a graphical user interface(GUI) and enables auser to interface with applications.

OS KERNEL
communicates directly with the hardware and manages how hardware resources are used to meet software requirements.

HARDWARE
The physical part of a computer including underlying electronics.

The physical part of a computer including underlying electronics.

This environment is accessible through several methods

✅◦ A console uses a low speed serial connection directly from a
computer or terminal to the console connection on the router.

✅◦ A dialup connection using a modem or null modem connected
to the router AUX port.

✅◦ Telnet to the router.

Purpose of OS

🔥Using a GUI enables a user to:

🔥Using a CLI on a Cisco IOS switch or router enables a network technician to:

🔥There are many distinct variations of Cisco IOS

Use a mouse to make selections and run programs.

Enter text and text-based commands.

Use a keyboard to run CLI-based network programs.

Use a keyboard to run CLI-based network programs.

IOS for switches, routers, and other Cisco networking devices.

OS numbered versions for a given Cisco networking devices.

Purpose of OS

All devices come with a default IOS and feature set. It is possible to upgrade the IOS version or feature set.
✅ Can be downloaded
from cisco.com.


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Access Methods

Most common ways to access the IOS are:

Secure Shell (SSH)
Cryptographic network protocol for operating network services.
Typical applications include remote command-line, login, and remote command execution

Telnet
A network protocol that allows a user on one computer to log into another computer that is part of the same network.

Console port
Combination of a display monitor and an input device.

Terminal Emulation Program

⚠Regardless of access method, a terminal emulation program will be required. Popular terminal emulation programs include PuTTY, Tera Term, SecureCRT, and OS X Terminal.

puTTY


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Tera Term


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Cisco IOS Modes of Operation


✅Hierarchical command
structure.

Each mode has a distinctive prompt and used to accomplish particular task.

IOS Modes

  1. User EXEC Mode

2.Privileged EXEC Mode


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  1. Global Configuration Mode

✅ Allows only a limited number of basic
monitoring commands.

✅“view only” mode.

❎ Not allow any commands that
might change the configuration of the router.

✅ Identified by the “>" prompt

✅ accesses all router commands.

✅Require a password from the
user before accessing it.

✅s require network administrator be at the privileged EXEC level.

✅Global configuration mode and all other more specific
configuration modes can be reached

✅ identified by the "#"
prompt.

✅allows users to modify the running system
configuration.

✅To enter configuration mode, enter the command configure
terminal from privileged mode.

✅e identified by the
(config)# prompt following the router name.

GLOBAL CONFIGURATION MODE


⭐Configuration mode submodes change
depending on what is being configured

📁 For example
when you enter interface configuration submode, the prompt changes to (config-if)# following the router name.

📁To exit configuration mode the user can enter end or
press Ctrl-Z.

This mode allows users to modify the running system
configuration.

✅To enter configuration mode, enter the
command configure terminal from privileged mode.

✅ Identified by the
(config)# prompt following the router name.

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Cisco CLI


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✅ Primary user interface used for configuring, monitoring, and maintaining Cisco devices.


✅ Interface allows you to directly and simply execute
Cisco IOS commands,

Primary Command Modes
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USER EXEC MODE

PRIVILEDGED EXEC MODE

Mode allows access to onlu limited number of basic monitoring commands.

Mode allows access to all commands and features.

It is often reffered to as"view-only" mode.

User can use any monitoring commands and executed configuration and management commands.

Configuration Example:


Router # show running-config

Router (config)# hostname ‘name’

Router (config)# banner motd # ‘banner’ #

Router # copy running-config startup-config

Router (config-if)# ip address 192.168.1.1

Router (config) # enable secret class

Router (config)# interface vlan 20

Router (Config)# interface fa0/1

Configuration Command Modes


⭐ Primary configuration mode is called global
configuration or simply, global config.

◦ Use the configure terminal command to access.
◦ Changes made affect the operation of the device.

Configuration modes can be accessed from
global configuration mode.

◦ Interface mode - to configure one of the network interfaces.

◦ Line mode - to configure the console, AUX, Telnet, or SSH access.

Navigate Between IOS Modes

Various methods can be used to exit / quit configuration
modes:

✅ exit - Used to move from a specific mode to the previous more general mode.

✅end - Can be used to exit out of global configuration mode regardless of which configuration mode you are in.

✅ ^z - Works the same as end.

Example of navigating between
IOS modes:

Various commands are used to move in and out of command
prompts:

  • To move from user EXEC mode to privileged EXEC mode, use the
  • Use return to user EXEC mode, use the disable command.

◦ Enter privileged EXEC mode using the enable command.

◦ Enter global config mode using the configure terminal command.

◦ Enter interface sub-config mode using the interface fa0/1 command.

◦ Exit out of each mode using the exit command.

◦ How you can exit the end or ^Z key combination.

Basic IOS Command Structure


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•Argument - not predefined; a value or variable defined by the user (in the figure, 192.168.10.5)

•Keyword - a specific parameter defined in the operating system (in the figure, ip
protocols)

IOS Command Syntax


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◦ description string - add a description to an interface.

◦ ping ip-address - The command is ping and the user-defined argument is the ip-address of the destinationdevice such as 10.10.10.5

IOS Context-Sensitive Help:


◦ Context-sensitive help provides a list of commands and the arguments associated with those commands.

◦ To access context-sensitive help, enter a question mark ?, at any promp.

IOS Command Syntax Check:

✅Checks an entered command from left to right
to determine what action is being requested.

✅If the interpreter understands the command, the requested action is
executed and the CLI returns to the appropriate prompt.

✅If the interpreter discovers an error, the IOS generally provides feedback such as “Ambiguous command”, “Incomplete command”, or “Incorrect commands".

Hot Keys and Shortcuts


EXAMPLE: configure = conf because
configure is the only command that begins with conf.

  • Shorter version of con will not work because more than one
    command begins with con.
  • Keywords can also be shortened.

The IOS CLI support the following hotkeys:

Down Arrow – Allows the user to scroll through command history.

Up Arrow - Allows the user to scroll backward through commands.

Tab - Completes the remainder of a partially entered command.

Ctrl-A - Moves to the beginning of the line.

Ctrl-E – Moves to the end of the line.

Ctrl-R – Redisplays a line.

Ctrl-Z – Exits the configuration mode and returns to user EXEC.

Ctrl-C – Exits the configuration mode or aborts the current command.

Ctrl-Shift-6 – Allows the user to interrupt an IOS process (e.g., ping)

Devices Communicate across network media


Overview of Network Components


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END DEVICES

  • Dekstop Computer
  • Laptop
  • Printer
  • IP Phone
  • Wiresless Tablet
  • TelePresence Endpoint

INTERMEDIARY DEVICES

  • Wiresless Router
  • LAN Switch
  • Router
  • Multilayer Switch
  • Firewall Appliance



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Network Media


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Network Representations


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Network Interface Card


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Physical Topology


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Logical Topology


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