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TOPIC 1.2 Classify Network Protocols and Communication, JOYCELYN ANG QIU…
TOPIC 1.2 Classify Network Protocols and Communication
The purpose of the Cisco IOS.
Also know as Internetwork Operating
System or Cisco IOS for its operating system.
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
Operating System made up by:
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.
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.
Router user interface
The Cisco IOS software uses a command-line interface (CLI) as the traditional console environment.
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.
Access Methods
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.
Telnet
Inband interfaces remotely establishing a CLI session through a virtual interface, over a network.
Cisco IOS Modes of Operation:
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
2. 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.
Global configuration mode and all other more specific Global configuration mode and all other more specific EXEC mode.
The privileged EXEC mode can be identified by the "#" prompt.
3. 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. 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 level does not allow any commands that might change the configuration of the router.
The user EXEC mode can be identified by the “>" prompt.
Cisco CLI
Primary user interface used for configuring, monitoring, and maintaining Cisco devices.
This user interface allows you to directly and simply execute Cisco IOS 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
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.
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
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.
IOS Help Features
IOS Context-Sensitive Help:
Context-sensitive help provides a list of commands and thearguments associated with those commands within the context of the current mode.
To access context-sensitive help, enter a question mark ?, at any prompt.
IOS Command Syntax Check:
1) The command line interpreter checks an entered command from left to right to determine what action is being requested.
2)If the interpreter understands the command, the requested action is executed and the CLI returns to the appropriate prompt.
3)• If the interpreter discovers an error, the IOS generally provides feedback such as “Ambiguous command”, “Incomplete command”, or “Incorrect command”.
Hot Keys and Shortcuts
Commands and keywords can be shortened to the minimum number of characters that identify a unique selection.
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).
IOS Command Syntax
description string
- The command is used to add a description to an interface.
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.
Intermediary Network Devices
Regenerate and retransmit data signals.
Maintain information about what pathways exist through the network and internetwork.
Notify other devices of errors and communication failures.
Direct data along alternate pathways when there is a link failure.
Classify and direct messages according to priorities.
Permit or deny the flow of data,based on security settings.
Network Media:
Copper
Fiber Optic
Wireless
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