rommon problem

Unanswered Question
Sep 23rd, 2009

Hi everyone

I got problem while uploading new IOs to my 2801 router

so after loading I had to make boot system unfortunately I wrote wrong ios name after reloading it automatically goes to rommon enviroment so in recovering procedure accidently wrote this command confreg 0x2142 instead 2102

and now router booting form nvram but there nothing just


these sybols

My question is how can I change confreg or how can I make it to work correctly

thank you

I have this problem too.
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Peter Paluch Wed, 09/23/2009 - 10:42


It is not clear from your description if the router ends in ROMMON but the output is readable, or if it displays only those garbled characters since it is started. However, it is possible that by changing the value of the configuration register, you have inadvertently entered a wrong value and changed your console speed as a result.

Try setting your terminal software to different speeds from 1200bps to 115200bps. Each time after you change your COM port speed in the terminal software, try hitting the Enter a few times to see if the router responds normally. If it does not, proceed to another speed.

When you found the speed, you may retain it or revert back to the 9600bps by issuing these commands:

conf t

line con 0

speed 9600

After you enter the last line, the router will stop responding again. Reconfigure your terminal software to use 9600bps and you should be fine and back to defaults.

If, however, your ROMMON is accessible and the garbled characters appear only after the actual IOS image is being loaded, then the FLASH contents may have become corrupt. In that case, I suggest removing the Compact Flash, starting the router and wait until it starts the ROMMON mode. Then, use the tftpdnld -r command to download and start the IOS directly to the RAM - do not reinsert the Compact Flash card yet. You will need to have the IOS image prepared on a TFTP server. Follow this document how to use the tftpdnld command:

After the IOS starts successfully, reinsert the Compact Flash card back to the router. Then issue the command format flash: in the privileged mode and allow the router to format the Compact Flash card completely. After this procedure completes successfully, configure the IP address of the router again in the configuration mode, and use the copy command to download the IOS back to the Compact Flash.

Best regards,


dreams_as_money Wed, 09/23/2009 - 20:32

Thanks for U help

My first mistake was that I wrote incorrect ios name in boot file system so after relodaing it goes to rommon but unfotunately I put 0x21042 instead 2102 I want to let router boot from flash thats why I had to change conf reg. after all I mean after reseting device not boot as ordinary only symbols however I change in my terminal all baud rate but get nothing only sybomls

so any idea thanks

is tehere any hardware reset or smth else

Giuseppe Larosa Wed, 09/23/2009 - 22:19

Hello Agha,

>> I put 0x21042 instead 2102

this is not possible config register is a 16 bits space and can store only 4 hexadecimal digits.

the router has taken a 4 hex value as its config register but I don't know what it can have on it.

2104 means:

Causes the following (listed in order of precedence):

Boot from Flash, if a valid IOS file exists.

Follow boot system commands found in the configuration.

Use the register value to form a filename from which to

netboot a system image from.

but this would mean you should be able to connect with standard console settings.

be more careful next time specially with config register.

value 1042 is another possibility

the following document can help:

Hope to help


Peter Paluch Wed, 09/23/2009 - 22:19


There is no hardware reset procedure that would automatically put the configuration register back to its default value of 0x2102 as far as I know. However, until your router is physically damaged, it absolutely must be possible to gain access to the ROMMON and/or to the IOS by finding out the correct COM port speed. Please try the procedure with the different COM port speeds once again. Make sure that the terminal you are using (Hyperterminal, PuTTY, ...) indeed accepts your port speed change - sometimes a disconnect/reconnect opereation is necessary, or the software doesn't allow you changing the port speed until you formally disconnect.

Also, please, are these garbled symbols displayed from the very start of the router, or are the starting messages printed out correctly (like initializing ECC memory, ROMMON initialized and so on) with the default speed settings of 9600 bps?

Best regards,



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