ch. 5 – managing cisco ios software ccna 2 version 3.0 rick graziani cabrillo college

Ch. 5 – Managing Cisco IOS Software

CCNA 2 version 3.0

Rick Graziani

Cabrillo College

Rick Graziani [email protected] 2

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Thanks! Rick


Overview

• Identify the stages of the router boot sequence • Determine how a Cisco device locates and loads the Cisco IOS • Use the boot system command • Identify the configuration register values • Briefly describe the files used by the Cisco IOS and their functions • List the locations on the router of the different file types • Briefly describe the parts of the IOS name • Save and restore configuration files using TFTP and copy-and-paste • Load an IOS image using TFTP • Load an IOS image using XModem • Verify the file system using show commands


Stages of the router power-on boot sequence

• Test the router hardware.

• Find and load the Cisco IOS software.

• Find and apply configuration statements, including protocol functions and interface addresses.


1. ROM 1. POST 2. Bootstrap code executed 3. Check Configuration Register value (NVRAM) 0 = ROM Monitor mode 1 = ROM IOS 2 - 15 = startup-config in NVRAM

2. Check for IOS boot system commands in startup-config file (NVRAM) If boot system commands in startup-config a. Run boot system commands in order they appear in startup-config to locate the IOS b If boot system commands fail, use default fallback sequence to locate the IOS (Flash, TFTP, ROM)

3. Locate and load IOS, Default fallback sequence: No IOS boot system commands in startup-config a. Flash (sequential) b. TFTP server (netboot) - The router uses the configuration register value to form a filename from

which to boot a default system image stored on a network server. c. ROM (partial IOS) or keep retrying TFTP depending upon router model - If no IOS located, get partial IOS version from ROM

4. Locate and load startup-config a. If startup-config found, copy to running-config b. If startup-config not found, prompt for setup-mode c. If setup-mode bypassed, create a “skeleton” default running-config (no startup-config)

Router Boot Process – At a Glance

1, 2

3

4


2. Check for IOS boot system commands in startup-config file (NVRAM)


Using the boot system command


Configuration register

Check Configuration Register value (NVRAM) 0 = ROM Monitor mode 1 = ROM IOS 2 - 15 = startup-config in NVRAM

• The order in which the router looks for system bootstrap information depends on the boot field setting in the configuration register.

• The configuration register is a 16-bit register in NVRAM.

• The lowest four bits of the configuration register form 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, changing only the value of the last hexadecimal digit.


show version – Showing the configuration registerGateway-Router>show versionCisco Internetwork Operating System SoftwareIOS (tm) C2600 Software (C2600-DO3S-M), Version 12.0(5)T1, RELEASE SOFTWARE (fc1)Copyright (c) 1986-1999 by cisco Systems, Inc.Compiled Tue 17-Aug-99 13:18 by cmongImage text-base: 0x80008088, data-base: 0x80CB67B0

ROM: System Bootstrap, Version 11.3(2)XA4, RELEASE SOFTWARE (fc1)

NoSmo-Gateway uptime is 5 weeks, 3 days, 20 hours, 33 minutesSystem returned to ROM by power-onSystem restarted at 13:30:22 PST Thu Mar 7 2002System image file is "flash:c2600-do3s-mz.120-5.T1"

cisco 2621 (MPC860) processor (revision 0x102) with 39936K/9216K bytes of memory.Processor board ID JAB03520113 (2485375272)M860 processor: part number 0, mask 49Bridging software.X.25 software, Version 3.0.0.2 FastEthernet/IEEE 802.3 interface(s)4 Serial(sync/async) network interface(s)32K bytes of non-volatile configuration memory. --More—Configuration register is 0x2102

Gateway-Router>

IOS source

configuration register


Modifying the configuration register

To change the boot field in the configuration register, follow these guidelines:

• To enter the ROM monitor mode, set the configuration register value to 0xnnn0, where nnn represents the previous value of the non-boot field digits. This value sets the boot field bits to 0000 binary. From ROM monitor, boot the operating system manually by using the b command at the ROM monitor prompt.

• To configure the system to boot automatically from ROM, set the configuration register to 0xnnn1, where nnn represents the previous value of the non-boot field digits. This value sets the boot field bits to 0001 binary.

• To configure the system to use the boot system commands in NVRAM, set the configuration register to any value from 0xnnn2 to 0xnnnF, where nnn represents the previous value of the non-boot field digits. These values set the boot field bits to a value between 0010 and 1111 binary. Using boot system commands in NVRAM is the default.

Router(config)#config-register value


Troubleshooting IOS boot failure

• What would you do?

• How would you begin?


Possible problems

• Configuration file has missing or incorrect boot system statement

• Incorrect configuration register value

• Corrupted flash image

• Hardware failure

How would you determine if any of these were the problem?


Troubleshooting

• An incorrect boot system command. Use the show running-config command and look for a boot system statement

• An incorrect configuration register setting will prevent the IOS from loading from flash. – The value in the configuration register tells the router where to get

the IOS. – This can be confirmed by using the show version command and

looking at the last line for the configuration register. • The router may have a corrupted flash image file. If this is the case,

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 none of the above appears to be the problem, the router could have a hardware failure. If this is the case, the Cisco Technical Assistance (TAC) center


IOS file system overview

RAMIOS (running)running-config startup-config IOS ios

• Routers and switches depend on software for their operation.

• The two types of software required are operating systems and configuration.

– The operating system used in almost all Cisco devices is the Cisco Internetwork Operating System (IOS).

– The software a router or switch uses is referred to as the configuration file or the config, running-config and startup-config.


Cisco IOS File System (IFS)

• Beginning with version 12.0 of the IOS, a single interface to all the file systems that a router uses is provided, Cisco IOS File System (IFS).

• The IFS provides a single method to perform all the file system management that a router uses, including

– the flash memory file systems,

– the network file systems (TFTP, rcp, and FTP)

– reading or writing data (such as NVRAM, the running configuration, ROM).

RAM

IOS (running)

running-config startup-config IOS ios



• The IFS uses a common set of prefixes to specify file system devices. • The IFS uses the URL convention to specify files on network devices

and the network. • The URL convention identifies the location of the configuration files

following the colon as [[[//location]/directory]/filename]. • The IFS also supports FTP file transfer.


Preparing for TFTP

Be sure you can communicate with the TFTP server.

Know the name of the IOS file you are going to copy from on the router.



RAMIOS (running)

running-config

startup-config IOS ios

copy tftp: system:running-config

copy tftp: nvram:startup-config

copy system:running-config tftp:

copy nvram:startup-config tftp:

copy from-file to-file

system: nvram: flash:

copy flash:<filename> tftp:

copy tftp: flash:<filename>


Cisco Traditional Copy Commands

RAMIOS (running)

running-config


copy tftp running-config

copy tftp startup-config

copy running-config tftp

copy startup-config tftp

copy from-file to-file

copy flash tftp

copy flash tftp


IOS naming conventions

Examples of feature-set categories are:

• Basic – A basic feature set for the hardware platform, for example IP and IP/FW

• Plus – A basic feature set plus additional features such as IP Plus, IP/FW Plus, and Enterprise Plus

• Encryption – The addition of the 56-bit data encryption feature sets, such as Plus 56, to either a basic or plus feature set. Examples include IP/ATM PLUS IPSEC 56 or Enterprise Plus 56. From Cisco IOS Release 12.2 onwards, the encryption designators are k8/k9:

• k8 – Less than or equal to 64-bit encryption in IOS version 12.2 and up

• k9 – Greater than 64-bit encryption (on 12.2 and up)

A relocatable image is copied from flash into RAM to run. A non-relocatable image is run directly from flash.


Example


Managing configuration files using TFTP


Managing configuration files using copy and paste

Perform the following to capture the configuration using the text displayed on the HyperTerminal screen to a text file:

1. Select Transfer 2. Select Capture Text 3. Specify the name for the text file to

capture the configuration 4. Select Start to start capturing text 5. Display the configuration to the

screen by entering show running-config

6. Press the space bar when each "-More -" prompt appears

7. When the complete configuration has been displayed, stop the capture by:

8. Select Transfer 9. Select Capture Text 10. Select Stop


Managing IOS images using TFTP


Restoring the IOS image from Flash

• If the IOS image in flash has been erased or corrupted, the IOS may need to be restored from the ROM monitor mode (ROMmon).

1. ROM

1. POST

2. Bootstrap code executed

3. Check Configuration Register value (NVRAM)

0 = ROM Monitor mode

1 = ROM IOS

2 - 15 = startup-config in NVRAM

• In many of the Cisco hardware architectures, the ROMmon mode is identified from the rommon 1 > prompt.

• The flash should be examined with the rommon 1 > dir flash: command.

• If an image is located that appears to be valid, an attempt should be made to boot from that image.

• This is done using boot flash: command.

rommon 1>boot flash:c2600-is-mz.121-5


Restoring the IOS image from Flash

RAMIOS (running)

running-config


• If the router properly boots, determine why the router booted to the ROMmon instead of using IOS from flash. – show version - to check the configuration register to ensure that it is

configured for the default boot sequence– show startup-config - to see if there is a boot system command

instructing the router to use the IOS for ROM monitor.• 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• Downloading the image using TFTP from the ROMmon mode.


Download using Xmodem from ROMmon

• Optional – Modifying the console baud rate to speed-up upload.• Requires rebooting of the router and the terminal session (at 9600)

should be terminated and a new session started at 115200 bps to match the console speed.

console



• The Xmodem command can be used from the ROMmon mode to restore the IOS software image from the PC.

• The format of the command is: xmodem -c image_file_name • The -c instructs the Xmodem process to use Cyclic Redundancy

Check (CRC) for error checking during the download.

console



• The router will prompt not to begin the transfer and present a warning message. • The warning message informs that the bootflash will be erased and asks to

confirm continuing.• Now the Xmodem transfer needs to be started from the terminal emulator. • In HyperTerminal, select Transfer > Send File. • Then in the Send File popup specify the image name/location, select Xmodem

as the protocol, and start the transfer. • During the transfer, the Sending File popup will display the status of the transfer.

console



• Once the transfer is complete a message appears that flash is being erased. • This is followed by the “Download Complete!” message. • Before restarting the router, the console speed needs to be set back to 9600

and the config register back to 0x2102.• Enter the command config-register 0x2102 at the privileged EXEC

prompt.• While the router is rebooting, the 115200 bps terminal session needs to be

ended and a 9600 bps session begun.

consoleRouter(config)#config-register 0x2102

Router(config)#line con 0

Router(config-line)#speed 9600


Download using TFTP from ROMmon

• The IOS can also be restored from a TFTP session using the tftpdnld command.

• The environmental variables provide a minimal configuration to allow for the TFTP of the IOS.

• To set a ROMmon environment variable: rommon>IP_ADDRESS=10.0.0.1


Download using TFTP from ROMmon

• Once the variables are set for the IOS download, the tftpdnld command is entered with no arguments.


File system verification


Getting the TFTP Software

• TFTP software is available for free for multiple OS’s.


Starting TFTP on Windows

• Be sure TFTP is running before copying to or from the TFTP server.

Cisco TFTP Server.lnk


Password Recovery

Step 1 config-register - At the router type the show version command. Record the configuration register setting, which is usually 0x2102. In a real world scenario, If for some reason you cannot log into the router, i.e. someone changed the password, then of course you will not be able to perform this step.

Step 2 – Entering rommonWithin 60 seconds press the Break key (control-break on a PC). You

may need to press this more than once. You will then see the following prompt:

System Bootstrap, Version 5.2(8a), RELEASE SOFTWARECopyright (c) 1986-1995 by cisco Systems2500 processor with 8192 Kbytes of main memory Abort at 0x10EA82C (PC)>


Password Recovery

Step 3 Breaking in - For the 2500 Series routers, after the “>” prompt type o/r 0x42 and press return. (Note, that this is the letter “o,” not the numeral zero.) Then type “i” and press return.

Abort at 0x10EA82C (PC)

> o/r 0x42

> i

• o/r 0x42 – This will change the configuration register on the router to ignore the startup-config file during boot-up.

• i – This will reboot (reload) the router.

The router will reboot and ask you if you want to go into setup mode. Type no


Password Recovery

Step 4 – Recovering the password Router> enableRouter# config t

To recover your previous startup-config file so you do not lose your previous configuration (if needed):

Router# copy startup-config running-config

Set your enable secret password. class is what we always use!.Router(config)# enable secret class

Change the configuration-register back to its proper value. Question: What happens the next time you reboot the router if you do not do this?Router(config)# config-register 0x2102 Router(config)# exit

Copy the running-config with the current privileged password to the startup-config.Router# copy running-config startup-config


Password Recovery

Step 5 – Verify

• At the router type the show version command.

• The configuration register setting should be 0x2102.


Downloading an IOS


Summary

Ch. 5 – Managing Cisco IOS Software

CCNA 2 version 3.0

Rick Graziani

Cabrillo College

ch. 5 – managing cisco ios software ccna 2 version 3.0 rick graziani cabrillo college

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