CCNA2 M5 Managing Cisco IOS Software

8/14/2019 CCNA2 M5 Managing Cisco IOS Software

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CCNA Semester2

Module 5

Managing Cisco IOS Software

Objectives

Router boot sequence and verification

Identify the configuration register values Save and restore configuration files

Save and restore IOS images


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Router Boot Sequence and

Verification

Router Startup Sequence


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Locating the Cisco IOS Software

Boot IOS from Flash Memory

A system image from flash memory can be loaded. The

advantage is that information stored in flash memory is not

vulnerable to network failures.


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Boot IOS from TFTP

In case flash memory becomes corrupted, a system

image can be loaded from a TFTP server.

Boot IOS from ROM

If flash memory is corrupted and the network server

fails to load the image, booting from ROM (if

available) is the final bootstrap option in software.


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Configuration register

The order in which the router looks for system

bootstrap information depends on the boot field

setting in the configuration register. The configuration register is a 16-bit register in

NVRAM.

Configuration register

Use a hexadecimal number to express

configuration register value .

Bit:

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 00x

016

16-bit register

1236

0 3: Boot field

6: Ignore NVRAM contents

8: Break disabled

11-12: Console line speed

13: Boot ROM if network boot fails

15: Diagnostic and ignore NVRAM


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Configuration register: Boot field (2)

Router(config)# config-register 0x2102

Router(config)# exit

Router# show version

show version

Cisco Internetwork Operating System Software

IOS (tm) 2500 Software (C2500-D-L), Version 12.0(10), RELEASE SOFTWARE (fc1)

Copyright (c) 1986-2000 by cisco Systems, Inc.

Compiled Mon 20-Mar-00 22:33 by phanguye

Image text-base: 0x0303882C, data-base: 0x00001000

ROM: System Bootstrap, Version 11.0(10c), SOFTWARE

BOOTFLASH: 3000 Bootstrap Software (IGS-BOOT-R), Version 11.0(10c), RELEASE

SOFTWARE (fc1)

SGCTT-HCM uptime is 1 week, 1 day, 1 hour, 9 minutes

System restarted by power-on

System image file is "flash:c2500-d-l.120-10"

cisco 2500 (68030) processor (revision N) with 2048K/2048K bytes of memory.

Processor board ID 23101339, with hardware revision 00000000

Bridging software.

X.25 software, Version 3.0.0.

1 Ethernet/IEEE 802.3 interface(s)

2 Serial network interface(s)

32K bytes of non-volatile configuration memory.

8192K bytes of processor board System flash (Read ONLY)

Configuration register is 0x2102


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The router boot process

ROM monitor

initializes

Stays in ROM

monitor

Boots the image

in boot ROM

or boot flash

What is

Boot

field?

Boot

commands

in NVRAM ?

Executes boot

commands

Routers

Fallback sequence

0 1

2 to F

yes no

Password Recovery

Cold Boot router

Ctrl + Break

Within 60s

In 25xx routers

o/r 0x2142

In 26xx routers

confreg 0x2142

i

Start


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Password Recovery

enable

Copy start run

Conf term

Enable secret cisco

Initial

Config?

N

Password Recovery

Config-register0x2102

Ctrl-Z

Copy Run Start


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Troubleshooting IOS boot failure

In the event that the router does not boot properly,

there are several things that could be wrong:

Configuration file has missing or incorrect boot system statement Incorrect configuration register value

Corrupted flash image

Hardware failure

Incorrect Boot System Statement

Use the show running-config command and look

for a boot system statement near the top of the

configuration.

If the boot system statement points to an

incorrect IOS image, delete the statement using

the no version of the command.


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Incorrect configuration register value

An incorrect configuration register setting will

prevent the IOS from loading from flash.

The value in the configuration register tells therouter where to get the IOS.

This can be confirmed by using the show version

command

Corrupted flash image

If this is the case, an error message should be displayedduring boot. That message may take one of several forms.Some examples are: open: read error...requested 0x4 bytes, got 0x0

trouble reading device magic number

boot: cannot open "flash:"

boot: cannot determine first file name on device "flash:"

If the flash image is corrupt, a new IOS should be uploadedinto the router.


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Hardware failure

If none of the above appears to be the problem,

the router could have a hardware failure.

If this is the case, the Cisco TechnicalAssistance (TAC) center should be contacted.

Although hardware failures are rare, they do

occur.

Managing the Cisco File System


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Software Components in Memory

Routers and switches

depend on software for

their operation. The two

types of software

required are operating

systems and

configuration files.

Cisco IOS File System

Beginning with version 12 of the IOS, a single interface

to all the file systems that a router uses is provided. This

is referred to as the Cisco IOS File System (IFS).

The IFS provides a single method to perform all the file

system management that a router uses.

This would include the flash memory file systems, the

network file systems (TFTP, rcp, and FTP), and readingor writing data (such as NVRAM, the running

configuration, ROM).


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IOS Version 12.x commands

The IFS uses the URLconvention to specifyfiles on networkdevices and thenetwork.

The URL conventionidentifies the locationof the configurationfiles following thecolon as[[[//location]/directory]/filename]

IOS naming conventions


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Managing configuration files using TFTP

Managing configuration files using copy and

paste

Another way to create a backup copy of the

configuration is to capture the output of the

show running-config command

Input configuration file using eatherHyper

Terminal-Send Text or Windows Buffer (Copy

and Paste)


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Managing IOS images using TFTP

Environment variables

The environmental variables provide a minimal

configuration to allow for the TFTP of the IOS.

The ROMmon TFTP transfer works only on the

first LAN port so a simple set of IP parameters

are set for this interface.


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Setting environment variables

Start router and press Ctrl+Break

Configure the environment variables

IP_ADDRESS= {ip_address}

IP_SUBNET_MASK={ip_subnet_mask}

DEFAULT_GATEWAY={default_gateway}

TFTP_SERVER={tftpserver_ip_address}

TFTP_FILE={IOS_filename}

set

sync (save environment variables in NVRAM)

tftpdnld

reset (after download completed)

Summary

Identifying stages of the router boot sequence

Using the boot system command

Identifying the configuration register settings

Managing configuration files using copy-and-paste

Managing system files with TFTP


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CCNA2 Module5

Documents

CCNA2 M5 Managing Cisco IOS Software