Loading an IOS on a switch via Xmodem

[Aninda Chatterjee]

A very good evening to all!

There are times when the IOS on a switch may crash and (as a last resort) you need to use the painfully slow Xmodem transfer to save your life. I bought a 3550 a while back and that is precisely what happened with me. Without much else to try, I decided to give Xmodem a shot. I want to share how this can be used and I hope that this may be useful to others.

Since the device is in ROMMON, there’s not much that you can do.  There is, however, a method to transfer another IOS using a direct  console connection with a PC (the transfer is over your console cable itself). This wonderful little thing is called  Xmodem. Now the rate of transfer depends on the baud rate that you set  for your console connection. I tried this with baud set to 9600 and man,  it seemed like it would take over 3 hours for the transfer to complete.  With a little trial and error, I found that the maximum baud rate I  could set it up to work perfectly with was 57600. You can set the baud  rate in ROMMON using the set BAUD <value> command. See below:

switch: set BAUD 57600

This MUST also match on the terminal program setting as well. So (I’m  using TeraTerm) under Setup -> Serial Port, set the baud rate to  match whatever you set it as in ROMMON. Now we’re ready to transfer the  file. The command is very straight forward:

switch: copy xmodem: flash:c3550-ipservicesk9-mz.122-44.SE6.bin

Once you press enter, you see the following:

Begin the Xmodem or Xmodem-1K transfer now…
C

At this point, you need to choose the file location from the terminal  program. Go under File -> Transfer -> Xmodem -> Send and  choose the file that you wish the transfer. The transfer will start and  you will see a transfer window pop up like this:

Once completed, you should get a prompt back to your ROMMON:

Begin the Xmodem or Xmodem-1K transfer now…
C…………………………………………………………………….                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                 ……………………………………………………………………..                                                                                                ……………………………………………
File “xmodem:” successfully copied to “flash:c3550-ipservicesk9-mz.122-44.SE6.bin”

Now from ROMMON, boot from flash using the following command:

switch: boot flash:c3550-ipservicesk9-mz.122-44.SE6.bin

This will try to boot the IOS specified and if the transfer was good, then this should go smoothly.

Loading  “flash:c3550-ipservicesk9-mz.122-44.SE6.bin”…#########################                                                                                                 ################################################################################                                                                                                 ################################################################################                                                                                                 ################################################################################                                                                                                 ################################################################################                                                                                                 ################################################################################                                                                                                 ################################################################################                                                                                                 ################################################################################                                                                                                 ################################################################################                                                                                                 ################################################################################                                                                                                 ################################################################################                                                                                                 ################################################################################                                                                                                 ################################################################################                                                                                                 ################################################################################                                                                                                 ################################################################################                                                                                                ########

File “flash:c3550-ipservicesk9-mz.122-44.SE6.bin” uncompressed and installed, entry point: 0×3000
executing…

All’s good again!! The switch runs a POST, once everything checks out, you’re back into the familiar territory!

        — System Configuration Dialog —

Would you like to enter the initial configuration dialog? [yes/no]: no

I hope this was informative.

[bartuszzz1]

Thanks!

[grbaloch091]

Thank you so much it worked for me as well. 

[jordiconrald]

hey guys. i have a prob just as stated but I cant copy my image file. it always fails. What i noticed though was that there are no files when i run the "dir flash:" command. Could that be where my problem lies?! i am using a cisco switch 2960 series.

[carlosrifel]

Hello! One question: 

How can establish the new flash: like the default, because first it try to connect from old flash:, give me an error and then from the new one which works without problem. But i would like to skip the first error.

Thanks!

[bhalerao.sachin121]

i m trying to this process for ws - C2950 C but not working. on that can anyone help in the same

[LUKASZ KITA]

Good work!

Worked perfectly! 

Thanks for help

[cvestal11]

This saved the day on a couple of 2960x switches that refused to stack.  Thanks!

[#9]

My 3750 has a corrupt ios and I am trying to use the xmodem to install one. I follow the steps above but I keep getting:

switch: copy xmodem:flash:c3750e-universalk9-mz.150-2.SE5.bin
Begin the Xmodem or Xmodem-1K transfer now...
CCCCCCCCCCxmodem:: I/O error

It is like it doesn't know where to get the ios from my thumb drive.

[Mandlenkosi Nkiwane]

I see you said you have a thumb drive connected that you want to copy from. Looking at the command, you are directing the xmodem to copy from the flash: and not from usbflash: 

You need to point it to the correct directory to reach that file.

[#11]

I was able to get it. I am using secureCRT.

I entered the commands the same.

switch: copy xmodem:flash:c3750e-universalk9-mz.150-2.SE5.bin

Then I selected Transfer and Send Xmodem at the top of CRT and selected the file from my computer.

shif

[Abu Saleh]

Great work...

[abhaymb.89]

CCCCCCCCCCxmodem:: I/O error showing this error message so what to do 

am using tera term vt

[teejay58]

I work at a college. We teach Router classes with cisco equipment, currently 2960 series. One of the students apparently corrupted the IOS. Our 2960's do not have a flash drive on the switch. However, we do have the IOS on a lot of other switches. Can we copy what's on another switch to the PC via xmodem, then upload it to the broken switch with the corrupted IOS? What's the command to do that?

[teejay58]

A problem that I ran into was that the copy command on my Catalyst 2960 switch, has a limit of 45 characters. I resolved this by renaming the OS file on my PC to a shorter name. So the OS was stored in "c:\temp\c2960-150-2.SE9.bin" but the copy command looked like this: 

"copy xmodem: flash:c2960-lanbasek9-mz.150-2.SE9.bin". Hope this helps someone out.

[Gabor Torok]

I can't belive, cisco turned back to the dark age... here's a lot of switch/router which is not at EOL, and we've got IOS 12.xx and 15.xx and still have to use bloody Xmodem to recovery... I've got an very old 2621 that knows tftpdnld already... my ironic question is what happend?! (at this moment I still sitting on C3560G V2 revovery via xmodem)