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Chapter 1: Explore The Network (1.2 Classify Network Protocol and…
Chapter 1:
Explore The Network
(1.2 Classify Network Protocol and Communication)
1.2.1 Explain the purpose of the Cisco
IOS.
The purpose of the Cisco IOS.
Cisco calls its operating system the Cisco Internetwork Operating
System or Cisco IOS.
The Cisco IOS provides the following network services:
◦ Basic routing and switching functions
◦ Reliable and secure access to networked resources
◦ Network scalability
It is the embedded software architecture in all of the Cisco
routers and is also the operating system of the Catalyst switches.
Operating System
All electronic devices require an operating system.
◦ Windows, Mac, and Linux for PCs and laptops
◦ Apple iOS and Android for smart phones and tablets
◦ Cisco IOS for network devices (e.g., switches, routers, wireless AP, firewall, …).
*for image, refer to page 5
Router user interface
This environment is accessible through several methods
A dialup connection using a modem or null modem connected
to the router AUX port.
Telnet to the router
◦ A console uses a low speed serial connection directly from a
computer or terminal to the console connection on the router.
The Cisco IOS software uses a command-line interface
(CLI) as the traditional console environment.
Purpose of OS
Using a GUI enables a user to:
◦ Use a mouse to make selections and run programs
◦ Enter text and text-based commands
Using a CLI on a Cisco IOS switch or router enables a network technician to:
◦ Use a keyboard to run CLI-based network programs
◦ Use a keyboard to enter text and text-based commands
There are many distinct variations of Cisco IOS:
◦ IOS for switches, routers, and other Cisco networking devices
◦ IOS numbered versions for a given Cisco networking devices
Purpose of OS (Cont.)
All devices come with a default IOS and feature set. It is possible to upgrade the IOS version or feature set
An IOS can be downloaded from cisco.com. However, a CISCO Connection Online (CCO) account is required.
*for image, refer to page 8
1.2.2 Explain how to access a Cisco IOS
device for configuration purposes.
Access Method
The three most common ways to access the IOS are:
Console port
– Out-of-band serial port used primarily for
management purposes such as the initial configuration of the router
Secure Shell (SSH) - Inband method for remotely and securely
establishing a CLI session over a network. User authentication,
passwords, and commands sent over the network are encrypted As
a best practice, use SSH instead of Telnet whenever possible..
Telnet – Inband interfaces remotely establishing a CLI session
through a virtual interface, over a network. User authentication,
passwords, and commands are sent over the network in plaintext.
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.
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Cisco IOS Modes of Operation
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The Cisco IOS modes use a hierarchical command
structure.
Each mode has a distinctive
prompt and is used to accomplish particular tasks
with a specific set of commands that are
available only to that mode.
IOS Modes
User EXEC mode
allows only a limited number of basic
monitoring commands.
referred to as a “view only” mode.
does not allow any commands that
might change the configuration of the router.
can be identified by the “>" prompt
Privileged EXEC mode
accesses all router commands.
can be configured to require a password
Configuration and management commands require that the
network administrator be at the privileged EXEC level.
can only be reached from the privileged
EXEC mode.
can be identified by the "#"
prompt.
*for image, refer to page 15
Global Configuration mode
This mode allows users to modify the running system
configuration.
To enter configuration mode, enter the command configure
terminal from privileged mode.
Configuration mode has various submodes, starting with
global configuration mode, which can be identified by the
(config)# prompt following the router name.
*for image, refer to page 19
Cisco CLI
The Cisco IOS command-line interface (CLI) is the primary user interface used for configuring, monitoring, and maintaining Cisco devices.
This user interface allows you to directly and simply execute Cisco IOS commands, whether using a router console or terminal, or using remote access methods.
*for image, refer to page 21 and 22.
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
Command Modes
The 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.
Specific sub configuration modes can be accessed from
global configuration mode. Each of these modes allows the configuration of a particular part or function of the IOS device.
◦ 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 commands are used to move in and out of command
prompts:
◦ To move from user EXEC mode to privileged EXEC mode, use the
enable command.
◦ Use return to user EXEC mode, use the disable command.
Various methods can be used to exit / quit configuration
modes:
◦ exit - Used to move from a specific mode to the previous more
general mode, such as from interface mode to global config.
◦ 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.
*refer to page 26
1.2.3 Describe the command structure
of the Cisco IOS software.
Basic IOS Command Structure
A Cisco IOS device supports many commands. Each IOS command has a specific format or syntax and can only be executed in the appropriate mode. The general syntax for a command is the command followed by any appropriate keywords and
arguments.
•Keyword
- a specific parameter defined in the operating system
•Argument
- not predefined; a value or variable defined by the user
After entering each complete command, including any keywords and arguments, press
the Enter key to submit the command to the command interpreter
*for image, refer to page 27
IOS Command Syntax
To determine the keywords and arguments required for a command,
refer to the command syntax
Examples
: ◦ description string - The command is used to add a description to an interface. The string argument is text entered by the administrator such as
description Connects to the main headquarter office switch.
◦ ping ip-address - The command is ping and the user-defined argument is the
ip-address of the destination device such as in ping 10.10.10.5
*for image, refer to page 28
IOS Help Features
IOS Context-Sensitive Help:
◦ Context-sensitive help provides a list of commands and the
arguments associated with those commands within the context of the current mode.
◦ To access context-sensitive help, enter a question mark ?, at any
prompt.
IOS Help Features (Cont.)
IOS Command Syntax Check:
• The command line interpreter 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
command”.
Hot Keys and Shortcuts
For example, the configure command can be shortened to conf because
configure is the only command that begins with conf.
◦ An even shorter version of con will not work because more than one
command begins with con.
◦ Keywords can also be shortened.
Commands and keywords can be shortened to the minimum number of
characters that identify a unique selection.
*refer to page 32
1.2.4 Explain how devices communicate
across network media
Overview of Network Components
*for image, refer to page 34, 35, 36
End Devices
*for image, refer to page 37
Intermediary Network Devices
*for image, refer to page 38
Network Media
*for image, refer to page 39,40
Network Representations
*for image, refer to page 41 and 42
Topology Diagrams
*for image, refer to page 43 and 44