Document ID: 15078 | |
Introduction
This document explains how to recover Cisco 2500, 3000, AS5100, and uBR900 Series Routers stuck in ROMmon (rommon#> or > prompt).
Prerequisites
Requirements
To recover a router from ROMmon mode, the router should be physically accessible and should have a terminal connected to the console port. Recovering a router from ROMmon is not possible by telneting to any of the interfaces. You must know how to copy the Cisco IOS® software image from a TFTP server to the router.
Components Used
The information in this document is based on the:
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Cisco 2500 Series Router
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Cisco 3000 Series Router
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Cisco AS5100 Series Universal Access Server
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Cisco uBR900 Series Router
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
For more information on document conventions, see the Cisco Technical Tips Conventions.
Verify the Configuration Register Value
The first thing that needs to be investigated is why the router is booting up in ROMmon mode (indicated by the "rommon # >" or ">" prompt). Determine whether the cause is due to the change of the configuration register value, or a corrupted Cisco IOS software image.
If the router has a valid Cisco IOS software image, then simply changing the configuration value register to 0x2102 will recover the router. The procedure for this is explained below.
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If the ROMmon prompt is ">", type the following at the ROMmon prompt:
>o/r 0x2102 >i System Bootstrap, Version 11.0(10c)XB2, RELEASE SOFTWARE Copyright (c) 1986-2003 by cisco Systems 2500 processor with 16384 Kbytes of main memory F3: 10021772+224116+562960 at 0x3000060 Restricted Rights Legend Use, duplication,............................
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If the ROMmon prompt is "rommon #>", type the following at the prompt:
rommon 1> confreg 0x2102
You must reset or power cycle the router for the new configuration to take effect:
rommon 2> reset System Bootstrap, Version 12.0(6r)T3, RELEASE SOFTWARE (fc1) Copyright (c) 1999 by cisco Systems, Inc. UBR924 platform with 16384 Kbytes of main memory.......................
If the router boots up successfully, then the cause was a configuration register value issue.
If the router boots up in ROMmon again, proceed to Download Cisco IOS Image Using the Boot Image from a Trivial File Transfer Protocol (TFTP) Server.
Download Cisco IOS Image Using the Boot Image from a Trivial File Transfer Protocol (TFTP) Server
There is only one way to install an image on the 2500, 3000, AS5100, or uBR900 Series Routers if the main Cisco IOS software has been deleted or corrupted. You must use its boot image.
Since you have already determined that the cause of the router booting up in ROMmon is not due to the configuration register value, the only option available for recovery is to re-install or upgrade the Cisco IOS software from a TFTP server using the built-in boot image (Rx-boot) in ROM.
To get into the Rx-boot mode or boot image, do the following:
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If the rommon prompt is "rommon # >", type:
rommon 1 > confreg 0x2101
You must reset or power cycle the router for the new configuration to take effect:
rommon 2>reset System Bootstrap, Version 12.0(6r)T3, RELEASE SOFTWARE (fc1) Copyright (c) 1999 by cisco Systems, Inc. UBR924 platform with 16384 Kbytes of main memory.......................
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If the rommon prompt is ">", type:
>o/r 0x2101 >i System Bootstrap, Version 11.0(10c)XB2, RELEASE SOFTWARE Copyright (c) 1986-1994 by cisco Systems 2500 processor with 16384 Kbytes of main memory Restricted Rights Legend Use, duplication, or ................ !--- Output suppressed .............16384K bytes of processor board System flash (Read/Write) Press RETURN to get started! hostname(boot)>
Notice that the prompt is now "router (boot)>", confirming that the router has booted up using the boot image.
Note: If the router boots up in ROMmon again, most likely the boot image is corrupt or missing and the only way to recover is by replacing the processor board System Flash or hardware.
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The next step is to upgrade the Cisco IOS software as follows:
hostname(boot)>enable hostname(boot)#copy tftp flash System flash directory: File Length Name/status 1 2416128 c2500-is-l.123-1a.bin [invalid checksum] [2416192 bytes used, 14361024 available, 16777216 total] Address or name of remote host [255.255.255.255]? 172.16.1.2 Source file name? c2500-is-l.123-1a.bin Destination file name [c2500-is-l.123-1a.bin]? Accessing file 'c2500-is-l.123-1a.bin' on 172.16.1.2... Loading c2500-is-l.123-1a.bin from 172.16.1.2 (via Ethernet0): ! [OK] Erase flash device before writing? [confirm] !--- Press Enter to confirm Flash contains files. Are you sure you want to erase? [confirm] !--- Press Enter to confirm Copy 'c2500-is-l.123-1a.bin' from server as 'c2500-is-l.123-1a.bin' into Flash WITH erase? [yes/no]yes Erasing device... eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee ee ...erased Loading c2500-is-l.123-1a.bin from 172.16.1.2 (via Ethernet0): !!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !--- Output suppressed !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! [OK - 16294764/16777216 bytes] Verifying checksum... OK (0x96AA) Flash copy took 0:08:23 [hh:mm:ss] hostname(boot)#
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Use the show flash command to verify the newly-loaded Cisco IOS image version.
hostname(boot)#show flash System flash directory: File Length Name/status 1 16294764 c2500-is-l.123-1a.bin [16294828 bytes used, 482388 available, 16777216 total] 16384K bytes of processor board System flash (Read/Write) hostname(boot)#
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After successfully copying the Cisco IOS image to the router, make sure that you change the configuration register back to 0x2102 and reload the router to boot from the Cisco IOS image.
hostname(boot)(config)#config-register 0x2102 hostname(boot)#reload System configuration has been modified. Save? [yes/no]: no Proceed with reload? [confirm] !--- Press Enter to confirm *Mar 1 00:12:58.463: %SYS-5-RELOAD: Reload requested System Bootstrap, Version 11.0(10c)XB2, PLATFORM SPECIFIC RELEASE SOFTWARE (fc1) Copyright (c) 1986-2003 by cisco Systems 2500 processor with 14336 Kbytes of main memory F3: 15405292+889440+952984 at 0x3000060 !--- Output suppressed Press RETURN to get started! hostname> -
Use the show version command to verify the configuration register value and the newly-loaded Cisco IOS image version.
hostname>show version Cisco Internetwork Operating System Software IOS (tm) 2500 Software (C2500-IS-L), Version 12.3(1a), RELEASE SOFTWARE (fc1) Copyright (c) 1986-2003 by cisco Systems, Inc. Compiled Fri 06-Jun-03 07:46 by dchih Image text-base: 0x0307F6E8, data-base: 0x00001000 ROM: System Bootstrap, Version 11.0(10c)XB2, PLATFORM SPECIFIC RELEASE SOFTWARE (fc1) BOOTLDR: 3000 Bootstrap Software (IGS-BOOT-R), Version 11.0(10c)XB2, PLATFORM SP ECIFIC RELEASE SOFTWARE (fc1) Router uptime is 2 minutes System returned to ROM by reload System image file is "flash:c2500-is-l.123-1a.bin" cisco 2500 (68030) processor (revision L) with 14336K/2048K bytes of memory. Processor board ID 13587050, with hardware revision 00000000 Bridging software. X.25 software, Version 3.0.0. 2 Ethernet/IEEE 802.3 interface(s) 2 Serial network interface(s) 32K bytes of non-volatile configuration memory. 16384K bytes of processor board System flash (Read ONLY) Configuration register is 0x2102
The show version command output above shows that the router has loaded the new Cisco IOS image and the configuration register value is 0x2102.
See Software Installation and Upgrade Procedure for the 1600, 2000, 2500, 3000, AS5100, and AS5200 for more information.
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Related Information
- Loading Cisco IOS Software using TFTP or RCP
- Configuration Register
- Technical Support - Cisco Systems
| Updated: Jan 30, 2006 | Document ID: 15078 |