Chapter 2 Configure a Network Operating System (12. Basic device…
Chapter 2 Configure a Network Operating System
1. Network Operating System
Computer-based network devices
use an operating system called a
network operating system.
enables device hardware to function and provides an interface for users to interact
The Cisco Internetwork Operating System (
) is a generic term for the collection of network operating systems used by Cisco networking devices.
The OS on home routers is usually called
. The most common method for configuring a home router is by using a web browser-based GUI
2. Operating Systems
: The physical part of a computer including underlying electronics
: The portion of the OS that communicates between HW and SW of a computer and manages how resources are used to meet SW requirements
: The user interface that allows users to request specific task,
(command line interface) or
(graphical user interface)
3. Access Methods
There are several ways to access the CLI environment and configure the device.
: Used for an initial configuration and maintenance purposes only (out-of-band access), by connecting a special cable (rollover or console cable) to the console port
: Used for remote management, this method provides password encrypted authentication and transport of session data, this keeps the user ID, pass, and details of the management session private
: Used for remote management without a securely encrypted connection, data is sent in plaintext
: a legacy auxiliary port that was used to establish a CLI session remotely using a modem (out-of-band).
4. Terminal Emulation Programs
Putty, Tera Term, SecureCRT, OS X Terminal
These programs allow you to enhance your productivity by adjusting window sizes, changing font sizes, and changing color schemes.
5. Cisco IOS Command Modes of Operation
As a security feature, the Cisco IOS software separates
Mode: Allows access to only a limited number of basic monitoring commands, it is a view-only mode. prompt: hostName
Mode: Allows access to all the commands and features. To access this mode you need to type the
command in the User exec Mode. prompt: hostName
6. Configuration Command Modes
To configure the device, the user must enter Global Configuration Mode (
Global Config Mode
). To access this mode you need to type the
command in the Privileged exec Mode. prompt: hostName
From this mode you can enter to different sub-configuration modes.
Line Configuration Mode
- Used to configure console, SSH, Telnet, or AUX access. default prompt: hostName(config-line)#
Interface Configuration Mode
- Used to configure a switch port or router network interface. default prompt: hostName(config-if)#.
7. Navigate Between IOS Modes
to return to the previous command mode.
to return to the privileged exec mode from any other mode.
from the user exec mode to enter to the privileged exec mode.
from the privileged exec mode to return to the user exec mode.
8. IOS command structure
Switch>show ip protocols
: a specific parameter defined in the operating system
: not predefined; a value or variable defined by the user
9. IOS command Syntax
: Commands and keywords
an optional element
a required element
z}] a required choice within an optional element
CLI Line Editing
: completes a partial command entry
: erases the character to the left of the cursor
: erases the character right to the cursor
: Moves the cursor to the end of the command line
: Moves the cursor to the beginning of line
At the "----More----" prompt
: Display the next line
: Display the next screen
: Ends the display string, returning to privileged exec
: Ends the configuration mode and returns to the privileged exec mode. When in setup mode, aborts back to the command prompt
: All-purpose break sequence. use to abort DNS lookups, traceroutes, pings, etc.
10. IOS help features
• Enables you to quickly find which commands are available in each command mode
• Which commands start with specific characters or group of characters
• Which arguments and keywords are available to particular commands
To access context-sensitive help, simply enter a question mark,
, at the CLI.
Command Syntax Check
It verifies that a valid command was entered by the user, and it will provide feedback describing what is wrong with the command.
12. Basic device configuration
It is useful to identify a device (e.g. for a remote session)
• Start with a letter
• Contain NO spaces
• End with a letter or a digit
• Uses only letter, digits and dashes
• Be less than 64 characters length
at global configuration mode to remove the configured hostname and return the switch to the default prompt,
Secure Device Access
When choosing a password
• Use more that 8 characters
• Use a combination of upper and lowercase letters, numbers, special characters, and/or numbers
• Avoid using the same password for all devices
• Don't use common words
: Switch(config)# enable secret
-----Switch(config)#line console 0
-----Switch(config)#line vty 0 15
Virtual terminal (
) lines enable remote access to the device.
Thi command applies weak encryption to all unencrypted passwords:
This encryption applies only to passwords in the configuration file.
command within the user exec, to verify that passwords are now encrypted.
It is a method for declaring that only authorized personnel should attempt to gain entry into the device.
Banner Message Of The Day
This message will be displayed on all subsequent attempts to access the device until the banner is removed.
Save the Running Configuration File
copy running-config startup-config
- The file stored in Non-volatile Random Access Memory (
) that contains all of the commands that will be used by the device upon startup or reboot.
- The file stored in Random Access Memory (
) that reflects the current configuration.
View the running configuration file.
View the startup configuration file.
show startup -config
command in the privileged EXEC mode to restore the startup-config.
command to erase the startup configuration file, and
They enable devices to locate one another and establish end-to-end communication on the Internet.
The structure of an IPv4 address is called
dotted decimal notation
and is represented by four decimal numbers between 0 and 255.
With the IPv4 address, a
is also necessary. An IPv4 subnet mask is a 32-bit value that separates the network portion of the address from the host portion.
address is the IP address of the router that the host will use to access remote networks, including the Internet.
command can be used to test connectivity to another device on the network or a website on the Internet. C:\ping x.x.x.x
S1(config)#no ip domain-lookup
command to prevent unwanted DNS lookup on a switch
Interfaces and ports
Cisco IOS Layer 2 switches
have physical ports for devices to connect.
These ports do not support Layer 3 IP addresses. Therefore, switches have one or more switch virtual interfaces (
These are virtual interfaces because there is no physical hardware on the device associated with it. An SVI is created in software.
An SVI provides a means to
remotely manage a switch
over a network using IPv4.
SVI is interface
interface vlan 1
//ip and mask
//this's 'cause the vlan1 is not activated by default
:warning: With this configuration, any device
to a port on the switch will have
(ping) with this Switch.
to the switch CLI, we need configure a line VTY to allow Telnet acces, and set the privileged exec password, after doing this we can use:
on the CMD of a windows PC
If we want to
access to the switch from another network
, we need to add a default gateway:
Switch(config)#ip default-gateway x.x.x.x
to see how the configuration has been added.
show ip interface brief
to see the condition of the switch interfaces.
When configuring a vlan different from the number 1, use:
With this, we add the vlan to the vlan data base
to configure it
show vlan brief
to see the vlan database
Dynamic Host Configuration Protocol (DHCP)
IP address information can be entered into end devices
, or using a protocol to do this (DHCP)
server addresses are the IPv4 addresses of the Domain Name System (DNS) servers, which are used to translate IP addresses to domain names
To manually configure an IPv4 address on a Windows host:
• Open the Control Panel >
• Network and Internet > Network Sharing Center >
• Change adapter settings and choose the adapter
• Right-click and select Properties
• Highlight Internet Protocol Version 4 (TCP/IPv4) and click Properties
It is possible to display the IP configuration settings on a Windows PC by using the
Jose Noe Vazquez Gutierrez