Ccna2 M5 Managing Cisco Ios Software

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

Router Boot Sequence and Verification

Router Startup Sequence

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.

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.

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 . 16-bit register

0x

0 0 0 0

Bit: 16 • • • • • •

0 – 3: 6: 8: 11-12: 13: 15:

0 0 0 0

0 0 0 0 6

Boot field Ignore NVRAM contents Break disabled Console line speed Boot ROM if network boot fails Diagnostic and ignore NVRAM

0 0 0 0 3 2 1 0

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

The router boot process ROM monitor initializes

0

Stays in ROM monitor

Boots the image

1

What is Boot

in boot ROM

field?

or boot flash 2 to F

yes

no

Boot commands in NVRAM ?

Executes boot

Router’s

commands

Fallback sequence

Password Recovery Start

Cold Boot router

Ctrl + Break Within 60s In 25xx routers

In 26xx routers

o/r 0x2142

confreg 0x2142

i

Password Recovery Initial Config?

N enable

Copy start run

Conf term

Enable secret cisco

Password Recovery Config-register 0x2102

Ctrl-Z

Copy Run Start

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.

Incorrect configuration register value • An incorrect configuration register setting will prevent the IOS from loading from flash. • The value in the configuration register tells the router 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 displayed during 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:"ú

• If the flash image is corrupt, a new IOS should be uploaded into the router.

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 Technical Assistance (TAC) center should be contacted. • Although hardware failures are rare, they do occur.

Managing the Cisco File System

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 reading or writing data (such as NVRAM, the running configuration, ROM).

IOS Version 12.x commands •

•

IOS naming conventions

The IFS uses the URL convention to specify files on network devices and the network. The URL convention identifies the location of the configuration files following the colon as [[[//location]/directory] /filename]

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 eather Hyper Terminal-Send Text or Windows Buffer (Copy and Paste)

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.

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-andpaste • Managing system files with TFTP

CCNA2 – Module5