Managing Cisco IOS Software

1
Managing Cisco IOS Software

• CCNA 2 v3 Module 5

2
Stages of the Router Power-on Boot Sequence
POST
Cisco Internetwork Operating System
Configuration File
3
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 5.1.3e-Lab
Router(config)
exit
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 5.1.4e-Lab
4
Configuration Register Boot Field

• To view the current values of the configuration
  register

Router
show version
..ltoutput omittedgt.. 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.
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.
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) ..ltoutput
omittedgt.. 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 "flashc2600-d-mz.12
2-16a.bin"
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.
Do 5.1.5e-Lab
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
8
IOS Naming Convention
System image file is "flashc2600-d-mz.122-16a.bin
"

• 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.
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 ?
131.108.2.155 Name of configuration file to
writemy-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
host255.255.255.255? 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
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 gt 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.

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 ?
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.b
in 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
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 monitormode
rommon 1gt
dir flash

• If a valid image is present try to boot it

rommon 1gt
boot flashc2600-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

13
Download using Xmodem from rommon gt

• 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 115200
  bps speeds up the download. To change console
  speed from rommon

rommon 1gt
confreg
Configuration Summary ..ltoutput
omittedgt.. Console baud 9600 Boot the ROM
Monitor Do you wish to change the configuration?
y/n n
y
Enable diagnostic mode y/n n
..ltoutput omittedgt.. 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.
14
Download using Xmodem from rommon gt
The xmodem command can be used from the rommon
mode to restore the IOS software image from the
PC  
Rommon 1gt
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 gt 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.

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 1gt
ip_address10.0.0.1
rommon 2gt
ip_subnet_mask255.255.255.0
rommon 3gt
default_gateway10.0.0.254
rommon 4gt
tftp_server192.168.1.1
rommon 5gt
tftp_fileGAD/basic0204/c2600-I-mz.12-1.bin
rommon 6gt
set
IP_ADDRESS10.0.0.1 IP_SUBNET_MASK255.255.255.0 D
EFAULT_GATEWAY10.0.0.254 TFTP_SERVER192.168.1.1
TFTP_FILEGAD/basic0204/c2600-i-mz.12-1.bin
rommon 7gt
tftpdnld
..ltoutput omittedgt.. Receiving GAD/basic0204/c2600
-I-mz.12-1.bin from 192.168.1.1
!!!!!!!!!!!!!!!!!!
File reception completed