Recovering IOS on a 2500 Series

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Lab Prerequisites:

  • You’ll need a Cisco 2500 Series router that has a corrupt image or NO IOS image at all. If you wish to simulate this lab you can erase the flash on your device and reboot. Please note that you’ll need to backup the Cisco IOS image prior to erasing it unless you have another image on hand that you wish to load onto the device.
  • A console connection to the device is REQUIRED.
  • You’ll need a TFTP server installed on your PC to restore the image.

Lab Objectives:

  • Boot the Cisco router into ROM mode by breaking the boot sequence using the keystroke CTRL+Pause Break
  • Change the configuration register to boot the ROM(BOOT) image. Configuration register to be used is 0x2141
  • Initialize the router by issuing the  i  command
  • Assign an IP address to the ethernet interface and configure a default gateway (if required)
  • Copy the Cisco IOS image from the TFTP server into flash memory.
  • Change the configuration register back to its default value and reload the device to ensure that the device boots up properly with the restored IOS image.

Lab Instruction:

Step 1. Boot the router into ROM mode by breaking the boot sequence using the keystroke CTRL+PAUSE BREAK

 

Copyright (c) 1986-1996 by cisco Systems
2500 processor with 14336 Kbytes of main memoryAbort at 0x10CFA0A (PC)
>

 

Step 2. Change the configuration register to boot the ROM(BOOT) image. Configuration register to be used is 0x2141

 

> o/r 0x2141

 

Step 3. Initialize the router by issuing the  i  command

 

> i
System Bootstrap, Version 11.0(10c), SOFTWARE
Copyright (c) 1986-1996 by cisco Systems
2500 processor with 14336 Kbytes of main memory[OUTPUT TRUNCATED]

Press RETURN to get started!

 

Step 4. Assign an IP address to the Ethernet interface and configure a default gateway (if required).

 

Press RETURN to get started!Router(boot)> enable
Router(boot)# config t
Router(boot)(config)# interface e0
Router(boot)(config-if)# ip add 10.1.1.20 255.255.255.0
Router(boot)(config-if)# no shut
Router(boot)(config-if)# exit
****NOTE: The line below is optional if your TFTP server is not on the same network****
Router(boot)(config)# ip default-gateway 10.1.1.254
Router(boot)(config)# end

 

Step 5. Copy the Cisco IOS image from the TFTP server into flash memory.

 

Router(boot)#copy tftp flashSystem flash directory:
No files in System flash
[0 bytes used, 8388608 available, 8388608 total]
Address or name of remote host [255.255.255.255]? 172.16.20.17
Source file name? c2500-i-l.121-27b.bin
Destination file name [c2500-i-l.121-27b.bin]?
Accessing file ‘c2500-i-l.121-27b.bin’ on 10.1.1.1…
Loading c2500-i-l.121-27b.bin from 172.16.20.17 (via Ethernet0): ! [OK]

Erase flash device before writing? [confirm]

Copy ‘c2500-i-l.121-27b.bin’ from server
  as ‘c2500-i-l.121-27b.bin’ into Flash WITH erase? [yes/no]y
Erasing device… eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee …erased
Loading c2500-i-l.121-27b.bin from 172.16.20.17 (via Ethernet0): !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!![OUTPUT TRUNCATED] !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
[OK – 8040260/8388608 bytes]

Verifying checksum…  OK (0xCB96)
Flash copy took 0:03:58 [hh:mm:ss]
Router(boot)#

 

Step 6. Change the configuration register back to its default value and reload the device to ensure that the device boots up properly with the restored IOS image.

 

Router(boot)# configure terminal
Router(boot)(config)# configuration-register 0x2102
Router(boot)(config)# end
Router(boot)# reloadSystem configuration has been modified. Save? [yes/no]: no
Proceed with reload? [confirm]

00:06:51: %SYS-5-RELOAD: Reload requested

System Bootstrap, Version 11.0(10c), SOFTWARE
Copyright (c) 1986-1996 by cisco Systems
2500 processor with 14336 Kbytes of main memory

Notice: NVRAM invalid, possibly due to write erase.

F3: 7916604+123624+619980 at 0x3000060

              Restricted Rights Legend

Use, duplication, or disclosure by the Government is
subject to restrictions as set forth in subparagraph
(c) of the Commercial Computer Software – Restricted
Rights clause at FAR sec. 52.227-19 and subparagraph
(c) (1) (ii) of the Rights in Technical Data and Computer
Software clause at DFARS sec. 252.227-7013.

           cisco Systems, Inc.
           170 West Tasman Drive
           San Jose, California 95134-1706

Cisco Internetwork Operating System Software
IOS ™ 2500 Software (C2500-I-L), Version 12.1(27b), RELEASE SOFTWARE (fc1)
Copyright (c) 1986-2005 by cisco Systems, Inc.
Compiled Tue 16-Aug-05 22:38 by pwade
Image text-base: 0x03041FDC, data-base: 0x00001000

cisco 2500 (68030) processor (revision N) with 14336K/2048K bytes of memory.
Processor board ID 11848462, with hardware revision 00000000
Bridging software.
X.25 software, Version 3.0.0.
1 Ethernet/IEEE 802.3 interface(s)
2 Serial network interface(s)
32K bytes of non-volatile configuration memory.
8192K bytes of processor board System flash (Read ONLY)

         — System Configuration Dialog —

Would you like to enter the initial configuration dialog? [yes/no]:

 

 

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