1760 Invalid confreg setting

Answered Question
May 22nd, 2008

The configuration register on a 1760 was accidentally set to 0x4142. (I think, I'm pretty sure it started with a 4 anyway). Now the only text that shows up on the console screen is 1 little theta like symbol. (small circle with horizontal line). The router has no configuration currently on it. Is there a way to recover from this condition?

I have this problem too.
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Correct Answer by Richard Burts about 8 years 6 months ago

Greg

Given the symptoms described by Billy, I believe that the console speed has been changed. If that is true when you boot into rommon there will still be the issue of a speed mismatch between the console port and the terminal emulator.

I believe that before the confreg command is used to change the config register that Billy needs to get the speed of his terminal emulator (Hyperterm or whatever he is using) to agree with the router console port speed. Since we do not know for sure what speed it is set to, I suggest starting at the lowest speed of 1200, and incrementing through 2400, 4800, up to the max of 115200. Be aware that some terminal emulators like Hyperterm require that you stop and restart the connection for the emulator to pick up the change in speed.

And assuming that he gets the console port speed matched with his terminal emulator speed, he should then get a prompt and can change the config register without having to go through rommon.

HTH

Rick

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gpulos Thu, 05/22/2008 - 05:38

You should enter rommon mode:

(reboot the router and press the BREAK key in the first 60 seconds of boot up)

Once in rommon mode: ie: rommon 1>; you should type:

'confreg 0x2102' (without apostrophes)

then type 'reset' to reboot the router.

Please see the following link for more info on these steps:

http://www.cisco.com/en/US/products/hw/routers/ps221/products_password_recovery09186a0080094773.shtml

(used for password recovery but should work for this as well)

This following link provides info on what specific configuration register settings do:

http://www.cisco.com/en/US/products/hw/routers/ps133/products_tech_note09186a008022493f.shtml

Correct Answer
Richard Burts Thu, 05/22/2008 - 08:51

Greg

Given the symptoms described by Billy, I believe that the console speed has been changed. If that is true when you boot into rommon there will still be the issue of a speed mismatch between the console port and the terminal emulator.

I believe that before the confreg command is used to change the config register that Billy needs to get the speed of his terminal emulator (Hyperterm or whatever he is using) to agree with the router console port speed. Since we do not know for sure what speed it is set to, I suggest starting at the lowest speed of 1200, and incrementing through 2400, 4800, up to the max of 115200. Be aware that some terminal emulators like Hyperterm require that you stop and restart the connection for the emulator to pick up the change in speed.

And assuming that he gets the console port speed matched with his terminal emulator speed, he should then get a prompt and can change the config register without having to go through rommon.

HTH

Rick

burleyman Thu, 05/22/2008 - 12:58

Here is what the confreg is set to...

Config in NVRAM will be ignored

Break key Disabled, after IOS load

Console Baud: 9600

Use filename: cisco2-4000 for tftpboot (on 4000 series)

Mike

burleyman Thu, 05/22/2008 - 13:01

Sorry for got to include some other info...

if it is set to 1142 then it will have a buad rate of 1200.

So that might be it.

Mike

billybenham Fri, 05/23/2008 - 04:38

1200 baud worked. Of course, obstinately I started at the higher speeds and worked down to 1200 like a fool. I was using PuTTY and it changed on the fly without restarting.

Thanks a lot.

Billy

Richard Burts Fri, 05/23/2008 - 10:42

Billy

I am glad that you got your problem worked out. Thank you for posting back and indicating that it was solved and what the solution was. It would help if you would mark the thread as solved so that others in looking at it would know that a solution had been found.

HTH

Rick

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