Recovering a Corrupt Cisco IOS Image on a 2500 Series Router

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 0×2141
•   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 memory   Abort at 0x10CFA0A (PC) >

Step 2. Change the configuration register to boot the ROM(BOOT) image. Configuration register to be used is 0×2141

>o/r 0×2141

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 flash   System 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 0×2102 Router(boot)(config)#end Router(boot)#reload   System configuration has been modified. Save? [yes/no]: n 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 0×3000060   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: 0×00001000   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]: