Transcript Introduction

Managing Cisco IOS Software
CCNA 2 v3 – Module 5
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Stages of the Router Power-on Boot Sequence
POST
Test the router hardware
Bootstrap
Flash
TFTP
ROM
Cisco
Internetwork
Operating
System
NVRAM
TFTP
Find and load the Cisco IOS
software into RAM
Console
Configuration
File
Find and apply configuration
statements, including protocol
functions and interface
addresses
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How a Cisco Device Locates and Loads IOS
The router uses boot system commands saved in NVRAM to locate the IOS.
Different settings in the configuration register enable the several alternatives:
Router#configure terminal
Router(config)# Boot system flash c4500-p-mz_111-18.bin
Router(config)# Boot system tftp c4500-1.bin 192.168.1.7
Router(config)# Boot system rom
Do 5.1.3
Router(config)# exit
e-Lab
Router#copy running-config startup-config
After it is reloaded, the router will try these commands in the order they were
entered.
The order in which the router looks for system bootstrap information
depends on the boot field setting in the configuration register. The
default configuration register setting can be changed with the following
command:
Router(config)#config-register 0x2142
Do 5.1.4
Hexadecimal number
e-Lab
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Configuration Register – Boot Field
To view the current values of the configuration register:
Router# show version
..<output omitted>..
Configuration register is 0x2102
The configuration register is a 16-bit register in NVRAM.
Note: the notation 0x informs us that the following number is a hexadecimal number.
From the example, Hex 2142 is 0010.0001.0000.0010 in binary.
The lowest four bits of the configuration register form the boot field.
Configuration register is 0x2102
Setting
0xnnn0
0xnnn1
0xnnn2
Description
Enter ROM monitor mode on reload.
Boot automatically from ROM.
Use boot system commands in NVRAM, this is the default.
CATC
0x2142: the system will not loadNESCOT
the configuration
file.
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Troubleshooting IOS Boot Failure
On boot the router checks the configuration file for a boot system statement.
Boot problems are typically caused by any of the following:

Configuration file has missing or incorrect boot system statement

Incorrect configuration register value
Corrupted flash image
Hardware failure


To identify the boot image source:
Router# show version
Cisco Internetwork Operating System Software
IOS (tm) C2600 Software (C2600-D-M), Version 12.2(16a),
RELEASE SOFTWARE (fc2) ..<output omitted>..
ROM: System Bootstrap, Version 12.1(3r)T2, RELEASE SOFTWARE
(fc1) Router uptime is 1 minute
System returned to ROM by power-on
System image file is "flash:c2600-d-mz.122-16a.bin"
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Troubleshooting IOS Boot Failure
If the router has a corrupted flash image file an error message
should be displayed during boot.
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.
The router could have a hardware failure.
If so, the Cisco TAC should be contacted.
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Do 5.1.5
e-Lab
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IOS File System Overview
1. The two types of software required are _________________
operating system and
_____________.
configuration
2. The ___________
Cisco IOS® is software that allows the hardware to function as a
router or switch.
3. The configuration contains the “instructions” that define how the device is
to _________________.
route or switch
4. A ____________________
network administrator creates the configuration that defines the
desired functionality of the Cisco device.
5. The IOS is stored in a memory area called _______.
flash
6. The flash allows the IOS to be _________
upgraded or stores _____________
multiple IOS files.
7. The IOS is copied into and run from ______.
RAM
8. A copy of the configuration file is stored in ________.
NVRAM
9. This is referred to as the “______________”.
startup-config
10. The startup configuration is copied into RAM at _________.
boot time
11. This configuration in RAM is the configuration used to _______
operate the router.
12. It is referred to as the “_____________”.
running-config
13. Beginning with version 12, the ______________________
Cisco IOS File System provides a
single method to perform all file system management.
14. The IFS uses ______
URLs to specify files on network devices and the network.
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IOS Naming Convention
Platform Feature Set
Binary file
System image file is "flash:c2600-d-mz.122-16a.bin"
Located in Flash
File Format
IOS Version number
Examples of feature-set categories are:
• Basic
• Plus
• Encryption (designated by ‘k8’ or ‘k9’ in IOS 12.2 and later)
The file format specifies if the IOS is compressed in flash
and if the IOS is relocatable.
A relocatable image is copied from flash into RAM to run.
A non-relocatable image is run directly from flash.
As Cisco develops newer versions of the IOS, the numerical
version number increases.
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Managing configuration files using TFTP
5.2.3 Lab
To store the current configuration on a network TFTP server
enter the following command:
My# copy running-config tftp
Remote host []? 131.108.2.155
Name of configuration file to write[my-config]? My2
Write file My2 to 131.108.2.155 ? [confirm] y
Writing My2 !!!!!!!!!!!!!!!!!!!! [OK]
A configuration file stored on one of the network servers can
be used to configure a router:
Router# copy tftp running-config
Host or network configuration file [host]?
IP address of remote host[255.255.255.255]? 10.0.0.13
Name of configuration file [Router-config] ? My2
Configure using My2 from 10.0.0.13? [confirm] y
Booting My2 from 10.0.0.13: !!!!!! [OK-180/16000 bytes]
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Managing Configuration Files using Capture and Send
To capture the configuration from HyperTerminal to a text file:
1.
Select Transfer  Capture Text
2.
Specify a name for the text file to capture the output to
3.
Select Start to start capturing text
Now all that appears on the screen will be written to the text file.
4.
Display the configuration with a show running-config
5.
To stop the capture select Transfer  Capture Text  Stop
After the capture is complete, the configuration file needs to be edited to
remove extra text, to add commands or to add comments with a !.
HyperTerminal can be used to restore a configuration. The edited backup of
the configuration can be copied into the router:
1.
Enter router global configuration mode.
2.
From HyperTerminal, click on Transfer > Send Text File.
3.
Select the name of the saved configuration file.
4.
The lines of the file will be entered into the router as if they were being
typed at the CLI. Observe any errors.
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Managing IOS Images using TFTP
5.2.5 Lab
Occasionally the router will need to have the IOS upgraded or
restored. On a new router the IOS should be backed up.
Nescot01# copy tftp flash
Address or name of remote host []? 192.168.1.17
Source filename []? c2600-d-mz.122-16a.bin
Destination filename [c2600-d-mz.122-16a.bin]?
Accessing tftp://192.168.1.17/c2600-d-mz.122-16a.bin
Erase Flash: before copying? [confirm]
Erasing the flash file system will remove all files
Continue? [confirm]
Erasing device eeeeeeeeeeeeeeeeeeee.. Erased
Loading c2600-d-mz.122-16a.bin from 192.168.1.17 (via
FastEthernet 0/0): !!!!!!!!!!!!!!!!!!!!!!
Verifying checksum .. .. .. ..OK
[OK 8906598 bytes]
8906598 bytes copied in 270.12 secs
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Recovering IOS Images
To identify why the IOS image did not load from flash:
1. Check to see if an image is available in flash:
ROM monitor
mode
rommon 1> dir flash:
2. If a valid image is present try to boot it:
rommon 1> boot flash:c2600-is-mz.121-5
3. If router now boots properly check the configuration register:
Router# show version
4. If the configuration register value is correct check for boot system
commands:
Router# show startup-config
If the router will not properly boot from the image or there is no IOS image, a
new IOS will need to be downloaded.
The IOS file may be recovered using either:

Xmodem to restore the image through the console

TFTP from the rommon mode
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Download using Xmodem from rommon >
To restore the IOS through the console you need:
1.
Copy of the IOS file on a PC.
2.
Terminal emulation program such as HyperTerminal.
Changing the baud rate from 9600 bps to 115200 bps speeds up the download.
To change console speed from rommon:
rommon 1> confreg
Configuration Summary
..<output omitted>..
Console baud: 9600
Boot: the ROM Monitor
Do you wish to change the configuration? y/n [n]: y
Enable diagnostic mode y/n [n]:
..<output omitted>..
Change console baud rate? y/n [n]: y
Enter rate: 0 = 9600, 1 = 4800, 2 = 1200, 3 = 2400 4
= 19200, 5 = 38400, 6 = 57600, 7 = 115200 [0]: 7
Note:
After changing the console speed and restarting the router in rommon
mode, the original terminal session at 9600 bps should be terminated
and a new session started to match the 115200 bps console speed.
Download using Xmodem from rommon >
The xmodem command can be used from the rommon mode to restore the IOS
software image from the PC:
Use CRC for error checking during the download
Rommon 1> xmodem -c c2600-is-mz.122-10a.bin
Do not start sending program yet…
Warning: All existing data in bootflash will be lost!
Invoke this application only for disaster recovery.
Do you wish to continue? y/n [n]: y
Ready to receive file c2600-is-mz.122-10a.bin . . .
Next, In HyperTerminal select Transfer > Send File.
1.
Specify the image name/location
2.
select Xmodem as the protocol
3.
start the transfer.
During the transfer the Sending File popup will display the status of the
transfer.
On completion, return config-register and HyperTerminal settings to normal.
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TFTP and Environment Variables
Downloading the image using TFTP from rommon is the fastest way to
restore an IOS image to the router. This is done by setting environmental
variables and then using the tftpdnld command:
rommon 1> ip_address=10.0.0.1
rommon 2> ip_subnet_mask=255.255.255.0
rommon 3> default_gateway=10.0.0.254
rommon 4> tftp_server=192.168.1.1
rommon 5> tftp_file=GAD/basic0204/c2600-I-mz.12-1.bin
rommon 6> set
IP_ADDRESS=10.0.0.1
IP_SUBNET_MASK=255.255.255.0
DEFAULT_GATEWAY=10.0.0.254
TFTP_SERVER=192.168.1.1
TFTP_FILE=GAD/basic0204/c2600-i-mz.12-1.bin
rommon 7> tftpdnld
..<output omitted>..
Receiving GAD/basic0204/c2600-I-mz.12-1.bin from
192.168.1.1 !!!!!!!!!!!!!!!!!! File reception completed
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