Transcript CCNA 1 Module 11 TCP/IP Transport and Application Layers

CCNA 2 Module 5
Managing Cisco IOS Software
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1
Objectives
• Router boot sequence and verification
• Managing the Cisco file system
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2
Router Startup Sequence
The startup routines must do the following:
• Test the router hardware
• Find and load the Cisco IOS software
• Find and apply configuration statements such as protocol
functions and interface addresses
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How a Cisco Device Locate and Load IOS
• The default source for Cisco IOS software depends
on the hardware platform.
• Most routers use the boot system commands
saved in NVRAM.
• Cisco IOS software allows several alternatives to be
used.
• Other sources can be specified for the software, or
the router can use its own fallback sequence to load
the software.
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4
Locating Cisco IOS Software
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5
Using the boot system Command
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Retrieve the Configuration Register
Values
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Configuration Register
• The configuration register is a 16-bit register in
NVRAM that is represented as 4 hexadecimal digits.
• The lowest four bits of the configuration register
form the boot field.
• Then use the config-register command and change
only the value of the last hexadecimal digit.
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Configuration Register Values
• The order in which the router looks for system bootstrap
information depends on the Boot Field setting in the configuration
register.
• You can change the default configuration register setting with
the global configuration mode command config-register.
Use a hexadecimal number as the argument for this command.
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9
Identifying Boot Image Source
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Troubleshooting IOS Boot Failure
There are several reasons that a router may not boot properly:
• Configuration file has missing or incorrect boot system statement
– the boot system statement may point to an incorrect IOS
image, use the no version of the command to delete the
statement.
• Incorrect configuration register value
– change the configuration register and save this as the start-up
configuration
• Corrupted flash image
– a new IOS should be uploaded into the router.
• Hardware failure
– contact the Cisco Technical Assistance Center
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11
Software Components in Memory
• Router and switch require IOS and
configuration file.
• The Cisco IOS is the software that
allows the hardware to function as
a router or switch.
• The configuration contains the
instructions that define how the
device is to route or switch.
• A network administrator creates a configuration that defines the
desired functionality of a Cisco device.
• The IOS is stored in a memory area called flash.
• A copy of the configuration file is stored in NVRAM to be used
during startup.
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Managing Configuration Files Using TFTP
• The startup configuration should be backed up in case
the configuration is lost.
• TFTP server can be used to back up the configuration
files for a Cisco device
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Managing Configuration Files Using TFTP
• The backup configuration file can be loaded from a TFTP
server to restore the router configuration.
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14
Managing Configuration Files Using
Copy and Paste
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Managing IOS Images Using TFTP
To store IOS images on a TFTP server
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The confreg Command
ROMmon and Xmodem can be used to restore IOS software images
The console speed can be changed from ROMmon mode using the
confreg command.
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Managing IOS Using XModem
The xmodem command can be used from the ROMmon mode to restore
an IOS software image from the PC
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Managing IOS Using Xmodem
Continued
Now the Xmodem transfer needs to be started from the terminal emulator.
In HyperTerminal, select Transfer > Send File. In the Send File popup
specify the image name and location, select Xmodem as the protocol, and
start the transfer. The Sending File popup will display the status of the
transfer.
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Managing IOS Using TFTP
• Since the ROMmon has very limited functions, no
configuration file is loaded during boot.
• The router therefore has no IP or interface configuration.
The environmental variables provide a minimal
configuration to allow for the TFTP of the IOS.
• To set a ROMmon environment variable, the variable
name is typed, then the equal sign (=), and the value for
the variable (VARIABLE_NAME=value).
• For example, to set the IP address to 10.0.0.1, type
IP_ADDRESS=10.0.0.1 at the ROMmon prompt.
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The set Command
• The IOS can also be restored from a TFTP session.
• The fastest way to restore an IOS image to the router is to
use TFTP from ROMmon to download the image.
• Set the environmental variables and then use the tftpdnld
command.
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The tftpdnld Command
• As each datagram of the IOS file is received, an exclamation point (!) will
be displayed.
• Router can be restarted by entering the reset command or typing i.
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22
File System Verification
• There are several commands that can be
used to verify the router file system.
show version
show flash
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The show flash Command
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