IOS : internetwork Operating System
CLI-based network operating system enables a network technician to do the following:
•Use a keyboard to run CLI-based network programs
•Use a keyboard to enter text and text-based commands
•View output on a monitor
Access Methods :
•Console – A physical management port used to access a device in order to provide maintenance, such as performing the initial configurations.
•Secure Shell (SSH) – Establishes a secure remote CLI connection to a device, through
a virtual interface, over a network. (Note: This is the recommended method for remotely connecting to a device.)
•Telnet – Establishes an insecure remote CLI connection to a device over the network. (Note: User authentication, passwords and commands are sent over the network in plaintext.)
Router And Switch Modes
User mode : Router > enable
Privileged Exec mode :
Router # configure terminal or disable to return to previous mode
Global Configuration Mode :
Router(config)# router eigrp 100
Router Configuration Mode :
Router(Config-router)# exit to return to previous mode
line Configuration Mode :
Router(config)# line con 0
Router(config-line)# login
Router(config-line)# password cisco123
Router(config-line)# exit
interface Configuration mode :
Router(config)# interface g0/0
Router(config-if)#no shutdown
Router(config-if)#ip address 192.168.1.1 255.255.255.0
Router(config-if)#exit ( return on step to back )
Router(config)#interface g0/0
Router(config-if)# end ( return directly to privileged exec mode )
configure device hostname : Router > enable
Router # configure terminal
Router(config)#hostname R1
configure password on privileged exec mode
Router(config)#enable password cisco123 ( clear text password)
Router(config)#enable secret cisco1234 ( encrypted Password)
removing secret password
Router(config)#no enable secret cisco1234
Router(config)#service password-encryption ( encrypt all clear text password)
Configure MOTD Banner
Router(config)# banner motd # unauthorized access is prohibited #
configure access console via username and password :
Router(config)#username admin password cisco123
Router(config)# line con 0
Router(config-line)# login local
Error Messages:
If the interpreter cannot understand the command being entered, it will provide feedback describing what is wrong with the command.
The error message “% Invalid input detected at “^” marker.” is mainly shown when the command is misspelled. Make sure the command is spelled correctly
The error message “% Incomplete command.” appears if you do not specify the required parameters for the command you entered. Make sure you know which parameters to provide.
The error message “% Ambiguous command.” is displayed if the command cannot be uniquely identified.
IOS Help Features
For help, type [?] from the command line.
The help tells you what commands start with a letter and what commands you can enter next. For example, if you want to know what commands begin with the letter “e” in user EXEC mode, type “?” after the letter “e” like this. after the “e” as shown below.
Router#e?
enable exit
abbreviated
Router#conf t
Router(config)#
use TAB To auto complete the command
Use IOS help to configure the clock on the router or the switch
