Cisco 2 - Routers Chapter 5
Page 1 Perrine & modified by Brierley 4/10/2020

Cisco 2 - Routers Chapter 5
4/10/2020 Perrine & modified by Brierley Page 2

Cisco 2 - Routers
Chapter 5
NVRAM
Non Volatile RAM
TFTP
Trivial File Transfer Protocol
Usually a hard disk
Random Access Memory
RAM
Flash
EPROM – Erasable
Programmable Memory
Rom Read Only Memory
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Cisco 2 - Routers
TFTP
NVRAM
Start
RAM
Run
Flash
Chapter 5
Rom
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Cisco 2 - Routers
TFTP
Back up server for configs and IOS
Configuration
NVRAM
Start
RAM
Run
Rom Loads boot instruction set
(bootstrap) to RAM on startup
4/10/2020 Perrine & modified by Brierley
Flash
IOS
Chapter 5
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Cisco 2 - Routers Router Startup Sequence Chapter 5
•
• Bootstrap locate & load IOS
• locate & load configuration file or enter ‘Setup’ mode
ROM loads bootstrap to RAM on start-up
Default sequence:
• flash
• TFTP Server
• ROM
• NVRAM
• TFTP Server
• console
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Cisco 2 - Routers Locating IOS Software (Operating System) Chapter 5
Use the configuration register that is saved in NVRAM to determine the sequence. ( show version ) provides the register address
If NVRAM does not contain boot system commands that the router can use, the system by default will then go to flash memory .
You can modify the sequence via the ‘ configurationregister’ 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
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Cisco 2 - Routers Configuration Register
The configuration register is a 16-bit register located in NVRAM.
The lowest four order bits of the register consists of the boot field .
Chapter 5
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Cisco 2 - Routers Configuration Register Chapter 5
There are 3 monitor modes:
• ROM monitor 0xnnn 0
• ROM 0xnnn 1
• from NVRAM 0 xnnn 2 TO 0x nnn F
NOTE: When one enters the ROM monitor mode, use the b command at the
ROM monitor prompt.
For example to enter the ROM mode enter:
Router(config)# config-register 0x2101
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Cisco 2 - Routers 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.
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Cisco 2 - Routers Trouble Shooting - IOS boot failures Chapter 5
:
• configuration file has missing
• incorrect boot system statement
• incorrect configuration register value
• corrupted flash image
• hardware failure
• do a s run , and look for a boot system statement. If incorrect, go to global configuration mode and put a no in front of the statement.
• do a s version , and see if the configuration register is incorrectly set
• if the flash is corrupted, an error message during boot will appear
• none of the above, then it is possibly a hardware error. Call TAC.
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Cisco 2 - Routers Trouble Shooting - IOS boot failures Chapter 5
Remember the configuration register is shown in show version (s ver) .
The configuration register is NOT displayed in show run or show start .
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Cisco 2 - Routers IOS File System Overview Chapter 5
There are two types of software required for switches & routers to operate:
1.
Operating system (IOS)
2.
Configuration
IOS image is in flash
Running config is in RAM .
Startup config is in NVRAM .
Some of the functions specified by the config file are:
• IP addresses of the interfaces
• Routing protocols
• Networks to be advertised
NOTE: To restore a previously good copy of the config file which is in
NVRAM type: copy start run
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Cisco 2 - Routers IOS File System Overview Chapter 5
Beginning with version 12 of the IOS, a single interface to all the file systems that a router uses is provided in the Cisco IOS File System (IFS).
Some prefixes used:
• Bootflash:
• flash:
• ftp:
• nvram:
• rcp:
• Slot0:
• Slot1:
• system:
• Tftp:
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Cisco 2 - Routers IOS Naming Convention Chapter 5
C2600-js-1_121-3.bin
Version number (12.13)
File format (relocatable; not compressed)
Feature Set (enterprise w/ extended features)
Hardware Platform (2600)
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Cisco 2 - Routers Backing up configuration files Chapter 5
From the router to TFTP: copy running-config tftp
• at the prompt, enter the IP address of the TFTP server
• enter the name assigned 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
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Cisco 2 - Routers Backing up configuration files Chapter 5
Another way to managing config files is to use the Transfer command of the HyperTerminal screen.
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Cisco 2 - Routers Upgrading/restore IOS files
If you restore or upgrade the IOS file, backup the original file first!!!!
Do: 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.
• a series of “ !
”s will be displayed while the file is downloading.
After the new flash successfully down loads it is then verified .
Chapter 5
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Cisco 2 - Routers Upgrading/restore IOS files Chapter 5
If the IOS image in flash has been erased or corrupted, you can restore the file while in ROM monitor mode. It is identified by: rommon 1 >
As an example: rommon 1 > boot flash :c2600-is-mz.121-5
You can also us Xmodem from ROMmon: rommon 1 > Xmodem -c c2600-is-mz.122-10a.bin
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Cisco 2 - Routers
Chapter 5
TFTP
Back up server for configs and IOS
Configuration
NVRAM
Start
RAM
Run
Flash
IOS
Rom Loads boot instruction set
(bootstrap) to RAM on startup
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