page 110/19/2015 chapter 5 ccna2 chapter 5 managing cisco ios software
TRANSCRIPT
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CCNA2 Chapter 5
Managing Cisco IOS Software
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• Bootstrap from ROM
• locate & load IOS Determined from config register; 0x2102 says to look in NVRAM for boot system cmds; if none then
Default sequence:
• flash• TFTP Server• ROM (subset of IOS)
• locate & load configuration file
or enter ‘Setup’ mode
• NVRAM• TFTP Server• console
•Default sequence:
Router Startup Sequence
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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 terminalRouter(config)# boot system flash IOS_filenameRouter(config)# boot system tftp IOS_filename tftp_address
Router(config)# boot system rom
[Ctrl-Z]
Router# copy running-config startup-config
Loading IOS Software
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Remember multiple images can be stored, so specify name
Specify name of image, plus IP address of server
Boot Options
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• 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
Boot System Command
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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
2 1 0 2
0010 0001 0000 0010
Configuration Register
Binary
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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
Configuration Register
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If the config-register is set to 0x2102
It tells the router to look in the startup configuration for boot system commands.
Configuration Register
To enter ROM monitor modeVargas(config)# config-register 0x2100Vargas(config)# exitVargas# copy run start
Destination filename [startup-config]? Building configuration...[OK]
Vargas# reloadProceed with reload? [confirm]rommon 1 >
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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.
Trouble Shooting IOS boot failures
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Remember the configuration register is shown in show version.
The configuration register is NOT displayed by a show run nor show start.
Trouble Shooting IOS boot failures
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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
IOS File System Overview
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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:
Trouble Shooting IOS boot failures
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C2600-js-l_121-3.bin
Hardware Platform (2600)
Feature Set (enterprise w/ extended features)
File format (relocatable; not compressed)
Version number (12.13)
IOS Naming Convention
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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
Backing up Configuration Files
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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
Using TFTP to Upload an IOS
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A TFTP service should run on this server. See http://www.solarwinds.com/downloads/
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Another way to managing config files is to use the Transfer command of the HyperTerminal screen.
Backing up Configuration Files
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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.
Upgrading/Restore IOS Files
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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.
Backing up the IOS to a TFTP Server
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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
Upgrading/Restore IOS Files
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Chapter 5X-Modem