Recovering IOS on a 2500 Series

Real World Application:

Although Cisco networking 2,500 series have a long life's grand plan, but they are usually used in a lab environment. However, there were a few times and still today 8+-year production run of luck. Drive maker could plead guilty to upgrade many tasks will be more conducive to networking business sees it as $$$. Why upgrade worked perfectly normal and 8+ years of equipment? All corrupt IOS or no image on 2500 series routers are usually used for this process. It is common to buy router Flash memory erasure, in which case you will need to perform an image restoration process.

Lab Prerequisites:

You need a corrupted image or not the Cisco IOS image in all 2,500 series routers. If you want to simulate the lab can wipe your device and restart Flash. Please note that you need to back up before the Cisco IOS image to remove it, unless you have another image you want on hand can be loaded into the device.
A console connection to the device is required.

You need to install on your PC to restore the image on the TFTP server.

Lab Objectives:

By breaking the keystrokes CTRL + pause break of the Cisco router boot sequence to boot to ROM mode
Change the configuration register boot ROM (BOOT) images. Configuration registers are used by 0x2141
I initialize a router commands issued through
For Ethernet interfaces assigned IP address and configure a default gateway (if required)
Copy the Cisco IOS image from the TFTP server to the Flash memory.

Change the configuration register back to its default value, and reloading the device to make sure the IOS image boots on the device and restore.

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 0x2141

Step 3. I initialize a router commands issued through

>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 reloading the device to make sure the IOS image boots on the device and restore.

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

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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.

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