Cisco IOS Recovery

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Contents

c3750

Example Issue

  • Issue: cannot boot, prompt is at switch:
# Example fail
switch: boot
Loading "flash:/c3750-ipbasek9-mz.122-46.SE.bin"...flash:/c3750-ipbasek9-mz.122-46.SE.bin: no such file or directory
 
Error loading "flash:/c3750-ipbasek9-mz.122-46.SE.bin"
 
Interrupt within 5 seconds to abort boot process.
Loading "flash:/c3750-ipbasek9-mz.122-55.SE6.bin"...@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
Error loading "flash:/c3750-ipbasek9-mz.122-55.SE6.bin"
 
Interrupt within 5 seconds to abort boot process.
Boot process failed...
 
switch: dir flash
  • Switch: c3750
  • IOS: c3750-ipbasek9-mz.122-55.SE1.bin


Requirements

  1. Have your .bin file stored locally (laptop)
  2. linux + minicom with working serial connection

Steps

  • Connect to switch - minicom 9600 8N1
  • CHANGE baud rate of switch (otherwise it will be hours to load a file)
 set BAUD 115200


  • change minicom to 115200 8N1
  • ready switch to recieve file over xmodem
 copy xmodem: flash:/<your IOS version filename>.bin
# example
switch: copy xmodem: flash:/c3750-ipbasek9-mz.122-55.SE1.bin                                                                                    
Begin the Xmodem or Xmodem-1K transfer now...                                                                                                   
C


  • send the local .bin file with minicom through xmodem
ctrl-a z
s
xmodem
select file (hit space)
enter to send file


  • watch your .bin file load! It will still be slow, but not hours @ 9600
         +-----------[xmodem upload - Press CTRL-C to quit]------------+                                                                        
Press CTR|Sending c3750-ipbasek9-mz.122-55.SE1.bin, 94373 blocks: Give |                                                                        
         |your local XMODEM receive command now.                       |                                                                        
.........|Xmodem sectors/kbytes sent: 54509/6813k                      |                                                                       |
         |                                                             |                                                                        
         |                                                             |                                                                        
switch:  |                                                             |                                                                        
         |                                                             |                                                                        
switch:  +-------------------------------------------------------------+


  • set baud rate back to 9600
otherwise you or someone else will be really confused when they next try to use it. Go back into the bootloader by power-cycling the switch and holding down the “Mode” button.
 set BAUD 9600


  • type boot (may have to type boot flash:/<your cisco file>.bin
switch: boot
Loading "flash:/c3750-ipbasek9-mz.122-46.SE.bin"...flash:/c3750-ipbasek9-mz.122-46.SE.bin: no such file or directory
 
Error loading "flash:/c3750-ipbasek9-mz.122-46.SE.bin"
 
Interrupt within 5 seconds to abort boot process.
Loading "flash:/c3750-ipbasek9-mz.122-55.SE1.bin"...@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
File "flash:/c3750-ipbasek9-mz.122-55.SE1.bin" uncompressed and installed, entry point: 0x1000000
executing...
 
              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
..... truncated


  • Check that you can reboot OK without ending up in the bootloader again.


Other Tricks

  • If the switch is not going into the bootloader, you may be able to force it
Try power-cycling the Catalyst while holding the “Mode” button on the front in to get the bootloader.
  • file system needs to be initialzied
Type “flash_init” to initialise the filesystem. (In our case, this wasn’t necessary)
Type “load_helper” to load any helper files (in our case there weren’t any since we’d just wiped the flash).
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