Recovering IOS on a 2500 Series
The Cisco 2500 Series routers are a very common lab router however due to their age you may be required to recover the device from a corrupt IOS image. This lab will discuss and demonstrate the IOS recovery procedure for the 2500 Series Routers.
Real World Application
While the Cisco 2500 Series has long past lived its life in the grand scheme of networking, they are however commonly used in LAB environments. However, there are a lucky few that still run in production today with up times of 8+ years. Many engineers can plea that upgrading would be more beneficial to the network but the business see’s it as $$$. Why upgrade a device that works perfectly fine and has been for 8+ years? This procedure is commonly used on 2500 series routers that have a corrupt IOS image or NO image at all. It is common to purchase used routers with the flash memory erased; in which case you would be required to perform an image restoration process.
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 memory Abort 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 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 0x2102 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 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 (tm) 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]:
