16637_Chapter 4 Introduction to the Cisco IOS

7/29/2019 16637_Chapter 4 Introduction to the Cisco IOS

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111 2006 Glcat,Zyuanli,. All rights reserved.

Introduction to the Cisco IOS

In this chapter, youll learn how to

configure a Cisco IOS router using both

the initial setup mode and the Cisco IOS

command-line interface (CLI). Through the

IOS interface, you can configure

passwords, banners, and more. Youll also

learn the basics of router configurations inthis chapter


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Cisco Router IOS

Carrying network protocols and functions

Connecting high-speed traffic betweendevices

Adding security to control access and stopunauthorized network use

Providing scalability for ease of network

growth and redundancy Supplying network reliability for connecting

to network resources


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Connecting to a Cisco Router


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Bringing Up a Routers

power-on

self-test (POST) load the Cisco IOS from flash memory

IOS loads and looks for a valid

configuration(stored by default innonvolatile RAM, or NVRAM)


7/41777 2006 Glcat,Zyuanli,. All rights reserved.

Setup Mode

You have two options when using setup mode:

Basic Managementand Extended Setup.

Basic Management only gives you enoughconfigurations to allow connectivity to the router,

but Extended Setup gives you the power to

configure some global parameters as well as

interface configuration parameters. To entersetup mode, just say yes or y to the following

question:



--- System Configuration Dialog ---

Would you like to enter the initial

configuration dialog? [yes/no]:y

At any point you may enter a question

mark '?' for help.Use ctrl-c to abortconfiguration dialog at any prompt.

Default settings are in square brackets '[]'.



Command-Line Interface

the command-line interface (CLI) truly is

the best way to configure a router. I

sometimes refer to the CLI as Cash Line

Interface because if you can create

advanced configurations on Cisco routers

and switches using the CLI, then youll getthe cash!



Logging into the Router

After the interface status messagesappear and you press Enter, the Router>prompt will appear. This is called user

exec mode (user mode) and its mostlyused to view statistics, but its also astepping-stone to logging into privilegedmode. You can only view and change theconfiguration of a Cisco router inprivilegedexec mode (privileged mode), which youget into with the enable command.



Router>

Router>enable

Router#



CLI Prompts

User mode Privileged mode

Global configuration mode

Interface configuration mode

RAM

NVRAM

Flash(IOS)

copy decompressed

decompressed

enable

disenable

config t exit

exitInterfice

end or ctrl+z

Router> Router#

Router(config)#

Router(config-if)#

Router(config-subif)#

R t d S it h Ad i i t ti



Router and Switch Administrative

Functions

Hostnames Banners

Password

Interface descriptions


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2006 Glcat,Zyuanli,. All rights reserved.

Hostnames

Router#config t

Enter configuration commands, one per

line. End with CNTL/Z.

Router(config)#hostname Todd

Todd(config)#hostname Atlanta Atlanta(config)#

See here:
http://localhost/var/www/apps/conversion/tmp/scratch_5/CCNA/Hostname%E8%AE%BE%E7%BD%AE/hostname.swfhttp://localhost/var/www/apps/conversion/tmp/scratch_5/CCNA/Hostname%E8%AE%BE%E7%BD%AE/hostname.swf


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Banners

A banneris more than just a little cool

one very good reason for having a banneris to give any and all who dare attempt to

telnet or dial into your internetwork a little

security notice.


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four available banner types

exec process creation banner incoming terminal line banner

login banner

message of the day banner


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Message of the day (MOTD) is the most

extensively used banner. It gives a

message to every person dialing into or

connecting to the router via Telnet or

auxiliary port, or even through a console

port See here:
http://localhost/var/www/apps/conversion/tmp/scratch_5/CCNA/MOTD%E8%AE%BE%E7%BD%AE/MOTD.swfhttp://localhost/var/www/apps/conversion/tmp/scratch_5/CCNA/MOTD%E8%AE%BE%E7%BD%AE/MOTD.swf


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Setting Passwords

There are five passwords used to secure

your Cisco routers:

console

Auxiliary

telnet (VTY)

enable password

enable secret.


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Enable Passwords

Console and Auxiliary used to set your

enable password thats used to secure

privileged mode. This will prompt a user

for a password when the enable command

is used.

examp e o sett ng t e ena e


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examp e o sett ng t e ena epasswords:

Router(config)#enable secret todd

Router(config)#enable password todd

The enable password you have chosen is

the same as your enable secret. This is

not recommended. Re-enter the enable

password.

See here:
http://localhost/var/www/apps/conversion/tmp/scratch_5/CCNA/%E5%AF%86%E7%A0%81%E8%AE%BE%E7%BD%AE/%E5%AF%86%E7%A0%81%E8%AE%BE%E7%BD%AE.swfhttp://localhost/var/www/apps/conversion/tmp/scratch_5/CCNA/%E5%AF%86%E7%A0%81%E8%AE%BE%E7%BD%AE/%E5%AF%86%E7%A0%81%E8%AE%BE%E7%BD%AE.swf


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User-mode passwords

Router(config)#line ?

First Line number

aux Auxiliary line

console Primary terminal line

tty Terminal controller

vty Virtual terminal

x/y Slot/Port for Modems


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aux Sets the user-mode password for the

auxiliary port.

console Sets a console user-mode

password.

vty Sets a Telnet password on the router.


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Telnet Password

Router(config-line)#line vty 0 ?

Last Line Number

Router(config-line)#line vty 0 4

Router(config-line)# password todd2

Router(config-line)# login See here:
http://localhost/var/www/apps/conversion/tmp/scratch_5/CCNA/Vty%E5%AF%86%E7%A0%81%E8%AE%BE%E7%BD%AE/Vty%E5%AF%86%E7%A0%81%E8%AE%BE%E7%BD%AE.swfhttp://localhost/var/www/apps/conversion/tmp/scratch_5/CCNA/Vty%E5%AF%86%E7%A0%81%E8%AE%BE%E7%BD%AE/Vty%E5%AF%86%E7%A0%81%E8%AE%BE%E7%BD%AE.swf


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Encrypting Your Passwords

Because only the enable secret password

is encrypted by default, youll need tomanually configure the user-mode and

enable passwords for encryption.


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To manually encrypt your passwords, use

the service password-encryption command.

Router#config t


line. End with CNTL/Z.

Router(config)#service password-

encryption


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Descriptions

Setting descriptions on an interface is

helpful to the administrator and, like the

hostname, only locally significant.


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Atlanta(config)#int e0

Atlanta(config-if)#description Sales Lan Atlanta(config-if)#int s0

Atlanta(config-if)#desc Wan to Miami

circuit:6fdda4321 See here:
http://localhost/var/www/apps/conversion/tmp/scratch_5/CCNA/Description/Description.swfhttp://localhost/var/www/apps/conversion/tmp/scratch_5/CCNA/Description/Description.swf


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Router Interfaces

The 2500 router is a fixed configuration

router, which means that when you buy

that model, youre stuck with that physicalconfiguration.

2600 router, interface type slot/port

See here:
http://localhost/var/www/apps/conversion/tmp/scratch_5/CCNA/%E6%8E%A5%E5%8F%A3%E9%80%89%E6%8B%A9/%E6%8E%A5%E5%8F%A3%E9%80%89%E6%8B%A9.swfhttp://localhost/var/www/apps/conversion/tmp/scratch_5/CCNA/%E6%8E%A5%E5%8F%A3%E9%80%89%E6%8B%A9/%E6%8E%A5%E5%8F%A3%E9%80%89%E6%8B%A9.swf


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Bringing Up an Interface

You can turn an interface off with the

interface command shutdown, and turn it

on with the no shutdown command.


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Router#config t

Enter configuration commands, one per line. End with

CNTL/Z.

Router(config)#int ethernet0 Router(config-if)#no shutdown

Router(config-if)#^Z

00:57:08: %LINK-3-UPDOWN: Interface Ethernet0, changed

state to up

00:57:09: %LINEPROTO-5-UPDOWN: Line protocol on Interface

Ethernet0, changed state to up

Router#sh int ethernet0

Ethernet0 is up, line protocol is up


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See here:

Configuring an IP Address on an
http://localhost/var/www/apps/conversion/tmp/scratch_5/CCNA/%E6%BF%80%E6%B4%BB%E6%8E%A5%E5%8F%A3/%E6%BF%80%E6%B4%BB%E6%8E%A5%E5%8F%A3.swfhttp://localhost/var/www/apps/conversion/tmp/scratch_5/CCNA/%E6%BF%80%E6%B4%BB%E6%8E%A5%E5%8F%A3/%E6%BF%80%E6%B4%BB%E6%8E%A5%E5%8F%A3.swf


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Configuring an IP Address on an

Interface

Router(config)#int e0 Router(config-if)#ip address 172.16.10.2

255.255.255.0

Router(config-if)#no shut


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If you want to add a second subnet

address to an interface, you have to use

the secondary parameter


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Router(config-if)#ip address 172.16.20.2255.255.255.0 secondary

Router(config-if)#^Z


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Serial Interface Commands

there are a couple of things you need toknow.First, the interface will usually be attachedto a CSU/DSU type of device that providesclocking for the line to the router. But if you have

a back-to-back configuration (for example, onethats used in a lab environment), one endthedata communication equipment (DCE) end ofthe cablemust provide clocking. By default,Cisco routers are all data terminal equipment

(DTE) devices,so you must tell an interface toprovide clocking if you need it to act like a DCEdevice.


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Router#config t


line. End with CNTL/Z. Router(config)#int s0

Router(config-if)#clock rate ?

Speed (bits per second) 1200

2400


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Router(config-if)#clock rate 64000

%Error: This command applies only toDCE interfaces

Router(config-if)#int s1

Router(config-if)#clock rate 64000 See here:

Viewing Saving and
http://localhost/var/www/apps/conversion/tmp/scratch_5/CCNA/%E4%B8%B2%E8%A1%8C%E6%8E%A5%E5%8F%A3%E5%91%BD%E4%BB%A4/%E4%B8%B2%E8%A1%8C%E6%8E%A5%E5%8F%A3%E5%91%BD%E4%BB%A4.swfhttp://localhost/var/www/apps/conversion/tmp/scratch_5/CCNA/%E4%B8%B2%E8%A1%8C%E6%8E%A5%E5%8F%A3%E5%91%BD%E4%BB%A4/%E4%B8%B2%E8%A1%8C%E6%8E%A5%E5%8F%A3%E5%91%BD%E4%BB%A4.swf


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Viewing, Saving, and

Erasing Configurations


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show running-config

show startup-config


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NVRAM

(startup-config)

RAM

(running-config)

copy running-config startup-config Bringing Up and decompressed

show startup-config

erase startup-config

show running-config


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Verifying Your Configuration

P166~172

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16637_Chapter 4 Introduction to the Cisco IOS