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Chapter 1:Explore The Network, 1.2 Classify Network Protocols And…
Chapter 1:Explore The Network
1.2.2 Explain how to access a Cisco IOS
device for configuration purposes.
Access Methods
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.
Cisco IOS Modes of Operation
User EXEC Mode
The user EXEC mode allows only a limited number of basic monitoring commands.
This is often referred to as a “view only” mode.
The user EXEC mode can be identified by the “>" prompt
Privileged EXEC mode
The privileged EXEC mode accesses all router commands.
This mode can be configured to require a password from the user before accessing it.
The privileged EXEC mode can be identified by the "#" prompt.
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.
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.
It is 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:
◦ Basic routing and switching functions
◦ Reliable and secure access to networked resources
◦ Network scalability
Cisco IOS
Operating System
OS Shell
• The OS shell is either a command-line interface (CLI) or a graphical user interface (GUI) and enables a user to interface with applications.
OS Kernel
• The 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.
Router user interface
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:
◦ Use a mouse to make selections and run programs
Using a CLI on a Cisco IOS switch or router enables a network technician to:
◦ Use a keyboard to run CLI-based network programs
There are many distinct variations of Cisco IOS:
◦ IOS for switches, routers, and other Cisco networking devices
1.2.4 Explain how devices communicate
across network media
Criteria to consider when choosing network media includes the following:
what is the maximum distance that the media can successfully carry a signal
Into what type of environment will the media be installed?
What is the amount of data and the speed at which it must be transmitted?
What is the cost of the media and installation?
1.2.3 Describe the command structure
of the Cisco IOS software.
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.
Configuration Example:
Router # show running-config
Router (config)# hostname ‘name’
Configuration 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.
◦ 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.
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 (in the figure, ip
protocols)
•Argument - not predefined; a value or variable defined by the user (in the
figure, 192.168.10.5)
IOS Command Syntax
◦ 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
Hot Keys and Shortcuts
Commands and keywords can be shortened to the minimum number of characters that identify a unique selection.
◦ An even 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).
1.2 Classify Network Protocols And Communication
