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1.2 Classify Network Protocols and Communication, Shell, Kernel, Hardware,…
1.2 Classify Network Protocols and Communication
1.2.1 Explain the purpose of the Cisco IOS
The purpose
Cisco calls its operating system :
the Cisco Internetwork Operating System or Cisco IOS
the embedded software architecture in all of the Cisco routers
the operating system of the Catalyst switches.
Network services provided by the Cisco IOS:
Basic routing and switching functions
Reliable and secure access to networked resources
Network scalability
Operating System
All electronic devices require an operating system
example:
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)
OS shell:
a command line interface (CLI) or a graphical user interface (GUI)
enable a user to interface with applications
OS Kernel:
communicates directly with the hardware
manages how hardware resources used to meet software requirements.
Hardware:
The physical part of a computer including underlying electronics.
Router user interface
The Cisco IOS software:
uses a command-line interface (CLI) as the traditional console environment.
Methods
A console:
uses a low-speed serial link from a device or terminal to the router's console connection
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
Use a mouse:
make selections
run programs
Enter:
text
text based commands
Using a CLI on a Cisco
IOS switch or router enables a network technician to
Use a keyboard :
run CLI based network programs
enter text and text based commands
Many distinct variations of Cisco IOS
IOS for:
switches
routers
other Cisco networking devices
IOS numbered versions for a given Cisco networking devices
1.2.2 Explain how to access a Cisco IOS device for configuration purposes
The three most common ways to access the IOS
Console port
Out of band serial port used primarily for
management purposes
example: the initial configuration of the router.
Secure Shell (SSH)
Inband method:
remotely and securely establishing a CLI session over a network
encrypted:
User authentication
passwords
commands sent over the network
use SSH instead of Telnet whenever possible as a best practice
Telnet
Inband interfaces:
remotely establishing a CLI session
through a virtual interface, over a network
sent over the network in plaintext:
User authentication
Password
Commands
Terminal Emulation Program
will be required when regardless of access method
Popular:
PuTTY
Tera
Term
SecureCRT
OS X Terminal.
Navigate the IOS
Cisco IOS Modes of Operation
use a hierarchical command
structure
Each mode has its own prompt
used to complete specific tasks with a particular set of instructions that have been only that mode has access to it.
IOS Modes
User EXEC Mode
allows:
only a limited number of basic monitoring commands
do not allow:
any commands that
might change the configuration of the router.
referred to as a “view only” mode.
identified by the “>" prompt
Privileged EXEC mode
accesses all router commands.
configured to require a
password from user before accessing it
Configuration and management commands require that the
network administrator be at the privileged EXEC level.
identified by the "#"
prompt.
Global Configuration mode
allows users:
modify the running system configuration
to enter configuration mode:
enter the command configure
terminal from privileged mode
has various submodes
identified by the
(config)# prompt following the router name.
configuration mode submodes change:
the words inside the parentheses change, depending on what is being configured
Example
enter interface configuration
submode:
the prompt changes to (config if)# following the router name
exit :
user can enter end or
press Ctrl Z.
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Cisco IOS command line interface (CLI)
the primary user interface used for:
configuring
monitoring
maintaining Cisco devices.
user interface allows to directly and simply execute
Cisco IOS commands
using a router console or terminal
using remote access methods.
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Configuration Command Modes
The primary configuration mode is called
global configuration
simply global config
Use configure terminal command to access.
Changes made affect the operation of the device.
Specific sub configuration modes
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 commands
used to move in and out of command prompts
To move from user EXEC mode to privileged EXEC mode:
use the enable command
return to user EXEC mode
use the disable command
Various methods
exit
Used to move from a specific mode to
general mode
such as from interface mode to global config
end
used to exit out of global configuration mode regardless of which configuration mode
^z
Works the same as end
1.2.3 Describe the command structure of the Cisco IOS software.
Basic IOS Command Structure
has a specific format or syntax and can only be executed in the appropriate mode
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
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IOS Command Syntax
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Example
description string:
used to add a description to an interface
ping ip address:
ping and the user defined argument is the ip address of the destination device
IOS Help Features
IOS Context
Sensitive Help
help provides a list of commands
arguments associated with those commands within
the context of the current mode.
To access:
enter a question mark (?), at any prompt
IOS Command Syntax Check
interpreter checks:
an entered command from left to right
determine what action is being requested
If the interpreter understands the command
the requested action executed
the CLI returns to the appropriate prompt.
If there an error
the IOS generally provides feedback
Example ;
“Ambiguous command”
“Incomplete command”
“Incorrect command”
Hot Keys and Shortcuts
Commands and keywords
shortened to the minimum number of
characters
which identify a unique selection.
Example
configure command can be shortened to conf
configure is the only command that begins with conf
An even shorter version of con will not work
when 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
example: ping
1.2.4 Explain how devices communicate across network media
Overview of Network Components
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End Devices
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Intermediary Network Devices
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Functions
Regenerate and retransmit data signals
Maintain information about what pathways exist through the network and internetwork
Notify other devices of errors and communication failure
Classify and direct message according to priorities
Direct data along alternate pathways when there is a link failure
Permit or deny the flow of data, based on security settings
Network Media
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Network Representations
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Topology Diagrams
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Shell
Kernel
Hardware
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