CCNA ITN: Module 2

operating system

required for all end and network devices to function

kernel

directly interacts with hardware in an OS

shell

interacts with user and applications, via CLI or GUI

CLI

text-based interface needing knowledge of command structure

GUI

graphical interface, more user-friendly but less powerful than CLI

Cisco IOS

CLI-based OS used on Cisco networking devices

default switch behavior

forwards traffic even without configuration

console connection

out-of-band method requiring no prior config

SSH

secure remote CLI access requiring network services

Telnet

unsecured CLI access sending data in plaintext

terminal emulation programs

tools like PuTTY, Tera Term, SecureCRT used to connect to network devices

User EXEC mode

[Switch>] provides limited view-only access

Privileged EXEC mode

[Switch#] gives full access to commands and features

global configuration mode

accessed via configure terminal from privileged mode [Switch(config)#]

line configuration mode

used to configure console, SSH/Telnet, or AUX access [Switch(config-line)#]

interface configuration mode

used to configure switch or router interfaces [Switch(config-if)#]

enable

enters privileged EXEC mode

disable

exits privileged EXEC and returns to user EXEC

exit

moves up one mode level or returns to global config mode

end/Ctrl+Z

quickly returns to privileged EXEC from any mode

IOS command structure

format includes prompt, command, space, then keywords or arguments

?

provides help with available commands, syntax, and options

syntax error feedback

provided by IOS if command is incorrect

command abbreviation

possible with shortened versions like conf t or en

Tab

autocompletes partial commands

up arrow

recalls previous command

Ctrl+C

aborts command or exits setup mode

Ctrl+Shift+6

interrupts and aborts current command immediately

hostname command

sets a unique name for the device in global config mode

hostname rules

must start with letter, no spaces, <64 characters, use only letters/digits/dashes

password best practices

8+ characters with uppercase, lowercase, numbers, and special symbols

line config password

set with password command and login command in line config mode

enable secret command

secures privileged EXEC access with encrypted password

service password-encryption

encrypts all plaintext passwords

show running-config

displays current config in RAM

banner motd

sets legal warning message for unauthorized access

startup-config

stored in NVRAM, used on startup/reboot, survives power loss

running-config

stored in RAM, reflects current config, erased on shutdown

show startup-config

displays startup config in NVRAM

copy running-config startup-config

saves current config to NVRAM for persistence

reload

discards running config and reloads from startup config

erase startup-config

deletes all saved configurations from NVRAM

save config to text file

enable terminal logging and use show command in terminal software

restore config file

copy-paste config in global mode via terminal emulator

IPv4 address

format of four decimal numbers 0–255 using dotted decimal notation

subnet mask

32-bit value defining network vs. host portion of an IP address

IPv6 address

128-bit hexadecimal string with colons between each group

network communication

depends on interfaces and properly matched cables

Layer 2 switch

doesn’t require an IP address but uses a switch virtual interface (SVI)

manual IP configuration

requires entering IP address, subnet mask, gateway, and DNS each time

manual config risk

increased chance of user misconfiguration

Windows IP setup

use control panel or enable DHCP for auto configuration

ipconfig

displays IP settings on a Windows host

SVI config

steps include interface vlan 1, ip address, and no shutdown

ip default-gateway

sets default gateway for remote switch access

show ip interface brief

displays status and IPs of all device interfaces

ping command

sends echo request packets to test network connectivity