ROMmon Recovery for the Cisco 3600/3700/3800 Series Routers

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Updated:September 13, 2006
Document ID:15080

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Introduction

This page explains how to recover a Cisco 3600/3700/3800 Series Router stuck in ROMmon, rommon# > prompt.

Prerequisites

Requirements

There are no specific prerequisites for this document.

Components Used

This document is not restricted to specific software and hardware versions.

The information presented in this document was created from devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If you are working in a live network, ensure that you understand the potential impact of any command before using it.

Conventions

Refer to Cisco Technical Tips Conventions for more information on document conventions.

Look for a Valid Image in Flash

First issue the dev command in order to see which devices are available on your router: 

rommon 1 >dev 
Devices in device table: 
idname 
flash:flash 
slot0:PCMCIA slot 0 
slot1:PCMCIA slot 1 
eprom:EPROM 
rommon 2 >

Next, issue the dir [device ID] command for each Flash or PCMCIA device available, and then look for a valid Cisco IOS® software image: 

rommon 3 >dir flash: 
         File size           Checksum   File name 
   35823432 bytes (0x804b4c)   0x6ba0    c3845-adventerprisek9-mz.124-10.bin  
rommon 4 >

Try to boot from that image. If the file is valid, this brings you back to normal operation mode: 

rommon 5 >boot flash:c3845-adventerprisek9-mz.124-10.bin  
program load complete, entry point: 0x80008000, size: 0x804a30 
Self decompressing the image : ################################### 
########...

If none of the files are valid, you have to download a new one that uses one of these procedures:

Use Another Router to Get a Valid Cisco IOS Software Image into the PCMCIA Card

In the event that you have a similar router, or at least one other router which has a compatible PCMCIA Flash card filesystem, you can also use that Flash card in order to recover the router. Refer to PCMCIA Filesystem Compatibility Matrix and Filesystem Information for more information.

  • If both routers are identical, or same series, you can use the Flash card from the other router in order to boot the one you want to recover.

    3600/3700/3800 series routers run their Cisco IOS software from dynamic RAM (DRAM), so you can remove a PCMCIA card while the router runs.

  • If both routers are different but have a compatible PCMCIA Flash card filesystem, you can use the other router to load a Cisco IOS Software image into a Flash card, which you can then move to the router you try to recover.

From the router that works, copy the image into the PCMCIA card.

Router#copy flash:c3845-adventerprisek9-mz.124-10.bin disk0:

Insert the PCMCIA card into the router in ROMmon mode and issue the boot command:

rommon 5 >boot disk0:c3845-adventerprisek9-mz.124-10.bin  
program load complete, entry point: 0x80008000, size: 0x804a30 
Self decompressing the image : ################################### 
########...

Once the router is up and runs you can copy the image to Flash and set the boot variable so that the router boots through this new image everytime it is rebooted.

3845#copy disk0:c3845-adventerprisek9-mz.124-10.bin flash:c3845-adventerprisek9-mz.124-10.bin
3845#configure terminal
Enter configuration commands, one per line.  End with CNTL/Z. 
3845(config)#no boot system
3845(config)#boot system flash c3845-adventerprisek9-mz.124-10.bin
3845(config)#^Z

Note: Refer to Software Upgrade Procedure for more information.

Download Using Xmodem from ROMmon

You can also download a new Cisco IOS Software through the console port through the use of Xmodem. Refer to Xmodem Console Download Procedure Using ROMmon for more information.

In addition, you can do a ROMmon Image Download Via Console Port Using Xmodem with Increased Console Speed.

Download Using tftpdnld ROMmon command (Cisco 3800 only)

You can also download the Cisco IOS software when you use the tftpdnld command from TFTP server when the router is in ROMmon mode. This procedure is explained in detail in How to Download a Software Image via TFTP Using the tftpdnld ROMMON Command.

Related Information

Revision History

Revision Publish Date Comments
1.0
13-Sep-2006
Initial Release

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