8/6/2019 Cisco Router Basics

1/18

BasicBasic

Cisco routerCisco routerconfigurationconfiguration

Donald W. SmithDonald W. SmithNovember 2001November 2001

8/6/2019 Cisco Router Basics

2/18

Cisco Router Basics 2

Cisco IOS

n Cisco routers run IOS

IOS = Internetwork Operating System

n Current version of IOS is 12.x

n Command line interface

complete on-line help

full line editing, history

n

IOS supports everything anyone would everwant to do with router

8/6/2019 Cisco Router Basics

3/18

Cisco Router Basics 3

CLI Sessions

n CLI sessions can be initiated from:

Console port

Aux port (modem)

Telnet (virtual line = vty)l Multiple sessions are allows (0-4 for IOS 12.0)

l Cannot telnet into router if no password set

n Each port can be password protected (with

separate passwords)n It is possible to use user based authentication

8/6/2019 Cisco Router Basics

4/18

8/6/2019 Cisco Router Basics

5/18

Cisco Router Basics 5

Router modes (cont.)

User mode router> Show router status and operation

Configuration cannot be viewed or altered

Privileged mode router#

Complete control over the router (anything can be setor reset)

Configuration cannot be altered

Configuration mode router(config)#

Used only for change of configuration Privileged mode commands are not available

Not password protected

8/6/2019 Cisco Router Basics

6/18

Cisco Router Basics 6

Router Mode commands

User

Privileged

Config

enable

config t

Ctrl Z

disable

8/6/2019 Cisco Router Basics

7/18

Cisco Router Basics 7

ROM

- Bootstrap- IOS- Rxboot

RAM

- Running IOS

- Running config

- Tables- Buffers

NVRAM

- startup-config

Flash

- IOS

- Other files

Router memory

1

2

8/6/2019 Cisco Router Basics

8/18

Cisco Router Basics 8

Router configurations

Two configurations: the active configuration (show running-config)

the startup configuration (show startup-config)

RAM

Active

config

Terminal

NVRAMStartup-config

NetworkTFTP config

8/6/2019 Cisco Router Basics

9/18

Cisco Router Basics 9

IOS Help System

n IOS has built-in help

n At the beginning of command line ?? will give a list ofall commands available in the current mode

If more than one screen,

l Space bar shows next screen

l Enter shows one more line

n Command (space) ?? showsshows a list of options

No Enter key is required

Retypes line ready for additional input

n If used after a character, help displays all

commands with the same prefix

8/6/2019 Cisco Router Basics

10/18

Cisco Router Basics 10

Command Line Editing

n All commands and strings can be abbreviated totheir shortest unique prefix (ex. sh run)

n Arrow keys will move the cursor to the left and

right on the command line

n Command history is accessed via up and downarrows

n Previous commands can be edited and re-

entered

8/6/2019 Cisco Router Basics

11/18

Cisco Router Basics 11

Command Line Editing

Advanced features:

^A To left end of line

^E To right end of line

^D Delete character under cursor ^K Delete to end of line

^F One character forward (or right ->)

^B One character backward (or left

8/6/2019 Cisco Router Basics

12/18

Cisco Router Basics 12

Network interfaces

n Each network interface has a type and number

n Types can be abbreviated, numbers start at 0

ethernet0 e0

Fastethernet0 f0 serial2 s2

tokenring1 to1

n Virtual interfaces are for various purposes

loopback tunnel

vlan

8/6/2019 Cisco Router Basics

13/18

Cisco Router Basics 13

Example Sequence

router> enable

router# conf t

router(config)# int e0

router(config-if)# ip addr192.168.1.10 255.255.255.0

router(config-if)# no shut

router(config-if)# ^z

router# sho ip int e0

8/6/2019 Cisco Router Basics

14/18

Cisco Router Basics 14

Passwords

n There are five (5) passwords Enable

l Password Legacy support only

l Secret Newer, encrypted password Console port

Aux port

Vty (telnet) port

n You can also use a tacacs server tomanage all passwords in your network

8/6/2019 Cisco Router Basics

15/18

Cisco Router Basics 15

Setting Passwords

n set the enable secret password router(config)# enable secret

router(config)# service password-encryption

router(config)# ^Z

n Set the console password router(config)# line con 0

router(config-line)# password

router(config-line)# login

n Set the telnet password (for all sessions) router(config-line)# line vty 0 4

router(config-line)# password

router(config-line)# login

router(config-line)# exit

8/6/2019 Cisco Router Basics

16/18

Cisco Router Basics 16

Useful Commands

n List all interfaces in a router router# show interface

n Display running configuration router# show running-configuration

n

Save the configuration (ram to NV-RAM) router# copy running-config startup-config

Router# copy run start

n Show IOS version, interfaces and memory router# show version

n Show contents of flash (IOS image) router# show flash

n Show running network protocols router# show protocols

8/6/2019 Cisco Router Basics

17/18

Cisco Router Basics 17

n Non-console session can receive messages

terminal monitor

n Disable console logging

no logging console (config)

n Configure router to use syslog

logging on (config)

logging

n Store in buffer

logging buffered (config)

n Display current configuration of message logging

show logging

Logging commands

8/6/2019 Cisco Router Basics

18/18