Chapter 7 & 8
IOS Images and Router Configuration
Where’s the IOS?




A method for specifying how the
router loads the IOS, is by
designating fallback sources for the
router to use in sequence from
NVRAM.
By default, the router will first look
in NVRAM
Then it will look in Flash
Then it will look towards the TFTP
Server
Configuration Register Values

Use the this command to change the default
configuration register setting:
Router(config)# config-register

Set the configuration register value to 0x--0 (0x100)
if you need to enter the ROM monitor.

Set the configuration register value to 0x--1 (0x101)
if you need to tell the router to boot from ROM.

Set the configuration register value to 0x--2 (0x102)
if you need to tell the router to boot from NVRAM.
Show Version Command



The show version command displays
information about the Cisco IOS software
version that is currently running on the
router. This includes the configuration
register and the boot field setting .
Show version displays information about
the system file image.
Show version is used to discover the
configuration register setting.
TFTP



Before copying software between the
TFTP server or host and Flash memory,
verify that there is sufficient room in
Flash to accommodate the IOS.
To copy a system image to a network
server, use the Router# copy flash
tftp command.
If upgrading the IOS on a router, use
the Router# copy tftp flash
command to copy the new IOS image
from a network server.
Show Flash Command

Use the show flash command to verify
that you have sufficient memory on your
system for the Cisco IOS software that
you want to load.

Show flash is also used to view the
name of the system image file.
Cisco’s IOS Naming Conventions

The naming convention for Cisco IOS
Release 11.2 contains three parts:
 the
platform on which the image runs
a
letter or series of letters identifies the
special capabilities and feature sets
supported in the image
 specifics
as to where the image runs
and whether it has been zipped or
compressed
Cisco’s IOS Naming Conventions


In the Cisco IOS name cpa25-cg-1,
the cpa25 represents the platform
on which the image runs.
In the Cisco IOS name cpa25-cg-1,
the cg represents the special
capabilities and feature sets.
Router Configuration Commands



Router(config)# boot system flash
IOS filename command is used to tell the
router to boot from flash.
Router(config)# boot system tftp
IOS filename ip address command is
used to tell the router to boot from a network
server.
Router(config)# boot system rom
command is used to tell the router to boot from
ROM.
Configuring an Interface


Router(config-int)# int E0 ip
address subnet mask command is
used to configure a router’s Ethernet 0
port.
Router(config-int)# int S0 ip
address subnet mask command is
used to configure a router’s Serial 0 port.
Password Recovery

A common procedure that technicians
perform on routers is the password
recovery procedure.

The configuration register 0x2142 is used
on a Cisco 2500 series router during
password recovery. (Why? And what
does it mean??)
Summary

Chapter 7 has great practical
importance - students must know
how to handle various IOS images.
And several CCNA Certification
Exam Objectives explicitly refer to
the sources for loading an IOS
image (flash, tftp server, ROM) and
methods for backing-up, upgrading,
and loading a backup Cisco IOS
software image.
Summary

Upon completing chapter 8, you
should be able to configure a router
with minimal information in a short
amount of time. Make sure that you
have entered the new IOS
commands from chapters 7 & 8 into
your Lab Companion!