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3750 recovery BAUD setting

So I had to format flash and recover. I did the quicker way by using set BAUD 115200...once the .bin was across I forgot to set the baud back to 9600. I have followed instructions: go back to switch: set BAUD 9600 then reset. also tried the unset command. problem is it always comes back up with a BAUD of 115200. Can someone tell me wahat I am doing wrong? Will I have to label 1 switch as 115200?

TIA!

Everyone's tags (4)
1 ACCEPTED SOLUTION

Accepted Solutions
Cisco Employee

3750 recovery BAUD setting

Riccardo and cweatherford,

The only thing that comes to my mind, then, is to try to execute this rather intrusive set of commands in the bootloader:

flash_init

delete flash:config.text

delete flash:private-config.text

set BAUD 9600

set (just verify if the BAUD variable currently holds the value of 9600)

set_bs bs: rw

set_param

reset

Please note that this sequence of commands will completely erase the configuration including RSA keys, possibly SDM templates etc.

If this does not help then I don't know what will.

Best regards,

Peter

45 REPLIES
Cisco Employee

3750 recovery BAUD setting

Hello,

unfortunately there is nothing you can do now

The only supported speed on this platform for xmodem transfer is 9600. The ROMMON CLI allows you to change speed to another value but then the change you would do in IOS back to 9600 is not synchronized with the ROM as this was never supposed to happen.

At the same time even if you break again into ROMMON you cannot set another speed or unset it. I guess you tried it already. You might have it another go but from past experience is not working.

So the solution is just as you wrote to label this switch as 115200 or RMA it.

The bug which (partially) documents this is

CSCsd98949    Console speed changes to value of boot loader BAUD env var after reload

The notes that you cannot read are basically telling what I wrote above.

Please rate and close the thread accordingly.

Regards,

Riccardo

New Member

3750 recovery BAUD setting

Wow...I even pulled those instructions from the Cisco site http://www.cisco.com/en/US/products/hw/switches/ps628/products_tech_note09186a0080169696.shtml

Thanks Riccardo! I can stop trying to figure this out now

Cisco Employee

3750 recovery BAUD setting

indeed this is a bad doc as it suggests to set speed to an unsupported value!!!

in theoretical terms the issue could be solved from a sw point of view (allowing a line speed synch from IOS to ROM) but the BU decided not to do so as the only supported speed is 9600...

Feel free to close the question when you are done

thanks

Riccardo

Cisco Employee

3750 recovery BAUD setting

Riccardo,

No offense intended, but this behavior is worse than silly - it is utterly brain-damaged. So the bootloader allows me to set the BAUD boot environment variable and store it somewhere but does not allow me to rewrite or unset it, neither from bootloader prompt nor from IOS? Once a code exists to set, rewrite and unset boot environment variables, where's the point in disallowing selected operations for selected variables? To me, this is nothing less than a gross software regression, especially considering that this WORKED correctly before!

Moreover, how can a particular speed be "unsupported" for xmodem? The xmodem is purely a software protocol that runs over any unframed character-based device or interface. Once the UART in 3750 supports the usual speeds typical for COM ports, the xmodem will happily run over it. Saying that "the 9600 bps is the only speed supported by xmodem" is like saying "the 10Mbps is the only supported speed by Ethernet DIX frame format" - slapping two totally independent things together.

Seriously, is there not a (possibly hidden) bootloader command that erases and reinitializes the area where boot variables are stored?

Best regards,

Peter

Cisco Employee

3750 recovery BAUD setting

Hi Peter,

unfortunately this is what the BU decided... I cannot comment further on it.

This is what they wrote when they closed the internal bug opened to track this behaviour

"It had been previously decided by the 3750 team that this behavior was

acceptable and would not be changed."

and "we officially only support 9600 baud even though the speed command is accepted."

you could try to change it again while in ROMMON but the value you enter is reset after reload.

--> reload

--> break booot

--> set BAUD 9600

--> boot

So, only chance is to RMA the switch if you don't want to connect at 115200 all the times.

Riccardo

Cisco Employee

3750 recovery BAUD setting

Riccardo,

I gave you a hard time answering my slightly annoyed post - but I assure you I did not intend to do any harm.

Is this problem also reproducible on 3560V2?

Best regards,

Peter

Cisco Employee

3750 recovery BAUD setting

eheheh no problem 

Is this problem also reproducible on 3560V2?

I don't really know...

R

Cisco Employee

3750 recovery BAUD setting

Riccardo and cweatherford,

The only thing that comes to my mind, then, is to try to execute this rather intrusive set of commands in the bootloader:

flash_init

delete flash:config.text

delete flash:private-config.text

set BAUD 9600

set (just verify if the BAUD variable currently holds the value of 9600)

set_bs bs: rw

set_param

reset

Please note that this sequence of commands will completely erase the configuration including RSA keys, possibly SDM templates etc.

If this does not help then I don't know what will.

Best regards,

Peter

Purple

3750 recovery BAUD setting

So what happens say if you watch it boot up at 115200  and then once its booted up make sure the config register is 0x2102 and reboot . This does not set the console speed to 9600 ????  

Cisco Employee

3750 recovery BAUD setting

Glen,

This won't work. This is a 3750 Catalyst switch - it does not have a configuration register, rather an environment variable that controls the console port speed. Obviously it can be set but once defined, the bootloader does not allow it to be unset or redefined.

Best regards,

Peter

Purple

3750 recovery BAUD setting

Nice feature !!!

Super Bronze

3750 recovery BAUD setting

Disclaimer

The     Author of this posting offers the information contained within this     posting without consideration and with the reader's understanding  that    there's no implied or expressed suitability or fitness for any   purpose.   Information provided is for informational purposes only and   should not   be construed as rendering professional advice of any kind.   Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In     no event shall Author be liable for any damages whatsoever   (including,   without limitation, damages for loss of use, data or   profit) arising  out  of the use or inability to use the posting's   information even if  Author  has been advised of the possibility of  such  damage.

Posting


Long time ago (about 6 months after their initial release), I bumped into the same issue with an original series 3750 (might have been a 3750G).  I.e. increased console speed to max for IOS upload and then got stuck with higher speed.  I remember I went crazy trying to get it back to 9600; also remember I eventually did.  Problem is, this was so long ago and only one time, don't recall what I exactly did to get it to work although I don't think it was quite as complex as what Peter has listed.  I very vaguely recall something with unsets in ROMMON and something I did in the IOS.  Again, unfortunately, don't recall the specifics of how I got it to work, but to recall I did get it to work.  (Also recall, I wasn't worried about preserving anything but the newly loaded IOS.)

New Member

Peter,Thank you so much for

Peter,

Thank you so much for the help. It solved the issue that I had with my 2970.

Regards

 

New Member

Thank you! it solved my

Thank you! it solved my problem on an 2960 too :)

Best regards Kevin
New Member

Thanks Peter, that worked for

Thanks Peter, that worked for me :)

New Member

Five years old advise and

Five years old advice and still a lot helpful :) . Thanks Peter :)

3750 recovery BAUD setting

Peter,

Thanks for ur commands and it helped to recover 3750-24TS-E model from 115200 to 9600

Thanga

Cisco Employee

3750 recovery BAUD setting

Hello Thangaraj,

Did it really help??? Man, I would be so glad if it did!

Best regards,

Peter

New Member

3750 recovery BAUD setting

Thanga,

Please let us know if you tried Peters instructions and if they worked.

Thanks,

Chad

Hall of Fame Super Gold

Re: 3750 recovery BAUD setting

Have you tried "unset BAUD"?

I've ROMmon a 3750G a month ago and set the baud to 115200.  I use "unset BAUD" and the baud rate went back to default 9600.

NOTE:  The command has to be in the correct syntax:  "unset" in lower case and "BAUD" in upper case.

Cisco Employee

Re: 3750 recovery BAUD setting

Hi Leo,

That was my original thought as well, but if you check the very first post in this thread, the original poster writes:

I have followed instructions: go back to switch: set BAUD 9600 then  reset. also tried the unset command. problem is it always comes back up  with a BAUD of 115200.

So I thought I won't be asking about the unset command anymore - but anyway, a good point.

Best regards,

Peter

Super Bronze

Re: 3750 recovery BAUD setting

Disclaimer

The      Author of this posting offers the information contained within this      posting without consideration and with the reader's understanding   that    there's no implied or expressed suitability or fitness for any    purpose.   Information provided is for informational purposes only  and   should not   be construed as rendering professional advice of any  kind.   Usage of  this  posting's information is solely at reader's own  risk.

Liability Disclaimer

In      no event shall Author be liable for any damages whatsoever    (including,   without limitation, damages for loss of use, data or    profit) arising  out  of the use or inability to use the posting's    information even if  Author  has been advised of the possibility of   such  damage.

Posting


I noticed that in the original post too, but as I wrote earlier, don't recall it taking a lot of commands, as Peter described, to get it back to 9600, but recall the documented procedure didn't work.  The key difference might be whether IOS is booted before or after rommon is reverted to 9600.  Leo, do you recall which was the case for you?

I've been trying to remember more about that incident, and I think I remember, what I encountered was after booting into the loaded IOS, without first resetting the baud, was I could reset (or unset?) the baud back to 9600, so switch would boot back into rommon at 9600 but when the IOS loaded the console port would reset to 115200.  (If this memory is correct, it was extremely annoying since baud rate would change during the boot process.)  Is there a way to change console baud rate in 3750 IOS?

Hall of Fame Super Gold

Re: 3750 recovery BAUD setting

The key difference might be whether IOS is booted before or after rommon is reverted to 9600.  Leo, do you recall which was the case for you?

Nope.  I've never seen an "unset BAUD" never worked before.  And to tell you frankly, I've broken alot of IOS (loaded the wrong one, erased the right one and/or formated the flash) and I've yet to see the "unset BAUD" fail me.

Is there a way to change console baud rate in 3750 IOS?

I did a ROMmon upgrade of a 3750 4 months back.  I made sure my baud rate was 115200 because I loaded the 12.2(25)SEE IOS in about 45-50 minutes.  After that, I just did an "unset BAUD" and it reverted to default 6900.

Cisco Employee

Re: 3750 recovery BAUD setting

cool!!!

it is weird that i found 6-7 TAC cases describing the issue and in at least 2 customers tried the reset procedure suggested by Peter with no success. I wonder if they did not follow it the right way or some other underlying hw issue popped up.

Cisco Employee

Re: 3750 recovery BAUD setting

Riccardo,

My suggested procedure involves rewrite of the boot sector contents - something generally not described in "popular literature". Did the TAC cases use the set_bs and set_param commands?

Best regards,

Peter

Cisco Employee

Re: 3750 recovery BAUD setting

yes, i found a case where the bu suggested that... not completely sure about the way the customer tried that.

maybe he just said he did it while he did not as he wanted the switch replaced

New Member

3750 recovery BAUD setting

I know that I forgot to do the unset before I rebooted. Leo, did you say you had used the unset either way?

Hall of Fame Super Gold

3750 recovery BAUD setting

did you say you had used the unset either way?

That is correct.  I have used the "unset BAUD" before a reboot (enter the command, hit enter, change the baud settings of my console client and enter "boot") and I've done this AFTER a reboot (enter "boot", go "Oooops!  ", enter the "unset BOOT" when the appliance finally boots up, change the baud settings).  Either way, doesn't make any difference.

New Member

3750 recovery BAUD setting

I tried that without success. I guess I will try again!

thanks!

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