Chapter 5
CCNA2 Chapter 5
Managing Cisco IOS Software
3/16/2016
Page 1
Router Startup Sequence
• Bootstrap
Chapter 5
from ROM
Determined from config register;
0x2102 says to look in NVRAM for
boot system cmds; if none then
• locate & load IOS
Default sequence:
• flash
• TFTP Server
• ROM (subset of IOS)
• locate & load configuration file
or enter ‘Setup’ mode
•Default sequence:
• NVRAM
• TFTP Server
• console
3/16/2016
Page 2
Loading IOS Software
Chapter 5
Use the configuration registers (show version) that is saved in NVRAM to
determine the sequence ( either from flash, ROM monitor, or RAM ).
If NVRAM lacks boot system commands that the router can use, the system
by default uses the the IOS software in flash memory.
One can modify the sequence via the ‘configuration-register’ command:
Router# configure terminal
Router(config)# boot system flash IOS_filename
Router(config)# boot system tftp IOS_filename tftp_address
Router(config)# boot system rom
[Ctrl-Z]
Router# copy running-config startup-config
3/16/2016
Page 3
Boot Options
Chapter 5
Remember multiple
images can be stored, so
specify name
Specify name of image,
plus IP address of server
3/16/2016
Page 4
Boot System Command
Chapter 5
• To find out if there are boot system commands
configured on a router, enter any one of the following
commands:
– show running-config
– show startup-config
3/16/2016
Page 5
Chapter 5
Configuration Register
The configuration register is a 16-bit register located in NVRAM.
The lowest four (4) bits of the register forms the boot field.
To ensure that the upper 12 bits are not changed, first retrieve the current
values of the configuration register using the show version command.
Then use the config-register command at the global configuration mode.
Configuration Register
Binary
2
0010
3/16/2016
1
0
2
0001
0000
0010
Page 6
Configuration Register
Chapter 5
There are 3 monitor modes:
• ROM monitor
0xnnn0
• ROM
0xnnn1
• from NVRAM
0xnnn2 TO 0xnnnF
NOTE: When one enters the ROM monitor mode, use the b command at the
ROM monitor prompt.
For example to enter the ROM mode do:
Router(config)# config-register 0x2101
3/16/2016
Page 7
Configuration Register
Chapter 5
If the config-register is set to 0x2102
It tells the router to look in the startup configuration for boot system
commands.
To enter ROM monitor mode
Vargas(config)# config-register 0x2100
Vargas(config)# exit
Vargas# copy run start
Destination filename [startup-config]?
Building configuration...
[OK]
Vargas# reload
Proceed with reload? [confirm]
rommon 1 >
3/16/2016
Page 8
Chapter 5
Trouble Shooting IOS boot failures
If a router doesn’t boot, then the following could be the problem:
• configuration file has missing or incorrect boot system statement
• incorrect configuration register value
• corrupted flash image
• hardware failure
Possible solutions:
• show run, and look for a boot system statement.
If incorrect, go to global configuration mode and put a no in front of
the statement.
• show version, and see if the configuration register is incorrectly set
• if the flash is corrupted, one will get an error message during boot
• none of the above, then it is possibly a hardware error.
3/16/2016
Page 9
Chapter 5
Trouble Shooting IOS boot failures
Remember the configuration register is shown in show version.
The configuration register is NOT displayed by a show run nor show start.
3/16/2016
Page 10
IOS File System Overview
Chapter 5
There are two (2) types of software required for switches and routers to
operate:
1.
Operating system (IOS)
2.
Configuration (configuration of the router/switch)
Running config is in RAM.
Startup config is in NVRAM.
IOS image is in flash
Some of the functions specified by the config file are:
•
IP addresses of the interfaces
•
Routing protocols
•
Networks to be advertised
3/16/2016
Page 11
Chapter 5
Trouble Shooting IOS boot failures
Beginning with version 12 of the IOS, a single interface to all the file systems
that a router uses is provided in Cisco IOS File System (IFS).
Some prefixes used:
•
Bootflash:
•
flash:
•
ftp:
•
nvram:
•
rcp:
•
Slot0:
•
Slot1:
•
system:
•
Tftp:
3/16/2016
Page 12
IOS Naming Convention
Chapter 5
C2600-js-l_121-3.bin
Version number (12.13)
File format (relocatable; not compressed)
Feature Set (enterprise w/ extended features)
Hardware Platform (2600)
3/16/2016
Page 13
Chapter 5
Backing up Configuration Files
From the router to TFTP:
copy running-config
tftp
• at the prompt, enter the IP address of the TFTP server
• enter the name to assign to the config file or accept default name
• confirm each choice by typing yes each time
From TFTP server to the router:
copy tftp running-config
• at the prompt, select a host or network config file
• at the system prompt,enter the IP address of TFTP server where the
configuration file is located
• at the system prompt, enter the name of the config file or accept the
default name
• confirm the configuration filename & the server address that the
system supplies
3/16/2016
Page 14
Chapter 5
Using TFTP to Upload an IOS
Before using TFTP to upload an IOS:
•
•
•
Check memory first (show flash)
Ping the IP address of your TFTP server
Know the name of the file you are copying from, make sure it is in the
default directory
3/16/2016
Page 15
Chapter 5
Troubleshooting IOS boot failures
A TFTP service should run on this server. See
http://www.solarwinds.com/downloads/
3/16/2016
Page 16
Chapter 5
Backing up Configuration Files
Another way to managing config files is to use the Transfer command of
the HyperTerminal screen.
3/16/2016
Page 17
Chapter 5
Upgrading/Restore IOS Files
To restore or upgrade the IOS file, backup the original file!!!!
Do the copy flash tftp
• router will prompt for the IP address of the TFTP server.
• router will prompt to erase flash if there is not sufficient room
available
• a series of e’s will appear to show the erase process.
• ! Will be displayed while the file is downloaded.
After the new flash is down loaded it is verified.
3/16/2016
Page 18
Chapter 5
Backing up the IOS to a TFTP Server
It is a good idea to back up the current IOS before
copying a new one, in case the copy fails - flash is
erased BEFORE the actual copy begins.
3/16/2016
Page 19
Chapter 5
Upgrading/Restore IOS Files
If the IOS image in flash has been erased or corrupted, one can restore the
file from the ROM monitor mode. It is identified by:
rommon 1 >
As an example:
rommon 1 > boot flash:c2600-is-mz.121-5
One can also us Xmodem from ROMmon:
rommon 1 > Xmodem -c c2600-is-mz.122-10a.bin
3/16/2016
Page 20
X-Modem
3/16/2016
Chapter 5
Page 21