1. Managing Cisco IOS Software
CCNA 2 v3 – Module 5
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2. Stages of the Router Power-on Boot Sequence
Test the router hardware
POST
Bootstrap
Find and load the Cisco IOS software into RAM
Flash
TFTP
ROM
Cisco Internetwork Operating System
NVRAM
TFTP
Console
Find and apply configuration statements, including protocol functions and interface addresses
Configuration File
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3. How a Cisco Device Locates and Loads IOS
Managing Cisco IOS Software
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_ bin
Router(config)#
Boot system tftp c bin
Router(config)#
Boot system rom
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Router(config)#
exit
Router#
copy running-config startup-config
Router#
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:
Hexadecimal number
Router(config)#config-register 0x2142
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4. 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 in binary.
Configuration register is 0x2102
The lowest four bits of the configuration register form the boot field.
Setting
Description
0xnnn0
0xnnn1
0xnnn2
Enter ROM monitor mode on reload.
Boot automatically from ROM.
Use boot system commands in NVRAM, this is the default.
0x2142: the system will not load the configuration file.
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5. 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 a.bin"
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6. 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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7. IOS File System Overview
The two types of software required are _________________ and _____________.
The ___________ is software that allows the hardware to function as a router or switch.
The configuration contains the “instructions” that define how the device is to _________________.
A ____________________ creates the configuration that defines the desired functionality of the Cisco device.    
The IOS is stored in a memory area called _______.
The flash allows the IOS to be _________ or stores _____________ files.
The IOS is copied into and run from ______.
A copy of the configuration file is stored in ________.
This is referred to as the “______________”.
The startup configuration is copied into RAM at _________.
This configuration in RAM is the configuration used to _______ the router.
It is referred to as the “_____________”.
Beginning with version 12, the ______________________ provides a single method to perform all file system management.
The IFS uses ______ to specify files on network devices and the network.
operating system
configuration
Cisco IOS®
route or switch
network administrator
flash
upgraded
multiple IOS
RAM
NVRAM
startup-config
boot time
operate
running-config
Cisco IOS File System
URLs
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8. IOS Naming Convention Examples of feature-set categories are: Basic
Platform
Feature Set
Binary file
System image file is "flash:c2600-d-mz a.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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9. 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 []?
Name of configuration file to write[my-config]? My2
Write file My2 to ? [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[ ]?
Name of configuration file [Router-config] ? My2
Configure using My2 from ? [confirm] y
Booting My2 from :
!!!!!! [OK-180/16000 bytes]
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10. Managing Configuration Files using Capture and Send
To capture the configuration from HyperTerminal to a text file:
Select Transfer  Capture Text
Specify a name for the text file to capture the output to
Select Start to start capturing text
Now all that appears on the screen will be written to the text file.
Display the configuration with a show running-config
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:
Enter router global configuration mode.
From HyperTerminal, click on Transfer > Send Text File.
Select the name of the saved configuration file.
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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11. 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 []?
Source filename []?
c2600-d-mz a.bin
Destination filename [c2600-d-mz a.bin]?
Accessing tftp:// /c2600-d-mz a.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 a.bin from (via FastEthernet 0/0):
!!!!!!!!!!!!!!!!!!!!!!
Verifying checksum OK
[OK bytes]
bytes copied in secs
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12. Recovering IOS Images
To identify why the IOS image did not load from flash:
Check to see if an image is available in flash:
ROM monitor mode
rommon 1>
dir flash:
If a valid image is present try to boot it:
rommon 1>
boot flash:c2600-is-mz.121-5
If router now boots properly check the configuration register:
Router#
show version
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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13. Download using Xmodem from rommon >
Managing Cisco IOS Software
Download using Xmodem from rommon >
To restore the IOS through the console you need:
Copy of the IOS file on a PC.
Terminal emulation program such as HyperTerminal.
Changing the baud rate from 9600 bps to 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 = = 19200, 5 = 38400, 6 = 57600, 7 = [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 bps console speed.
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14. 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 a.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 a.bin . . .
Next, In HyperTerminal select Transfer > Send File.
Specify the image name/location
select Xmodem as the protocol
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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15. 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=
rommon 2>
ip_subnet_mask=
rommon 3>
default_gateway=
rommon 4>
tftp_server=
rommon 5>
tftp_file=GAD/basic0204/c2600-I-mz.12-1.bin
rommon 6>
set
IP_ADDRESS=
IP_SUBNET_MASK=
DEFAULT_GATEWAY=
TFTP_SERVER=
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
!!!!!!!!!!!!!!!!!!
File reception completed
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