CCNA2 M5 Managing Cisco IOS Software
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Transcript of 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