Wednesday, August 5, 2009

Speedy Catalyst Switch IOS Crash Recovery

If your Cisco Catalyst Switch have boot errors, i.e., the switch is continuously booting or if it shows an error while booting and goes to the switch: prompt then its pretty obvious that you have an IOS crash. Catalyst Switches do not go to a rommon mode and hence TFTP upload in rommon is not possible on a switch. Therefore we have to resort to transferring the IOS image from your PC to the Switch through the console cable using Xmodem.

You can avail the Xmodem feature of Windows Hyperterminal. Open your Hyperterminal Application and set the baud rate to 9600 to access the switch console via your COM port. If your switch is already not at the switch: prompt, unplug the cord of the switch and power it back on as you press on the MODE button. Release the MODE button after the STAT LED goes out. Now you will be at the switch: prompt. Since downloading at a baud rate of 9600 is very very slow (can take more than 3 1/2 hours), therefore the best solution is to set the baud rate to 115200.

switch: set BAUD 115200

Now close your Hyperterminal Application and reopen it with a baud rate of 115200 for your COM port. Enter the command flash_init and load_helper. Issue the command to transfer the image at the prompt.

switch: copy xmodem: flash:c3750-ipbasek9-mz.122-50.SE3.bin

From the top of the Hyperterminal window, choose Transfer > Send File and from the Send File pop-up window browse the location of the correct IOS image and from the Protocol drop down list select Xmodem and click Send. Now the IOS image will start downloading to your switch which can take nearly half an hour, which is not that bad. Once the download in complete revert back to the baud rate of 9600.

switch: set BAUD 9600

Close your Hyperterminal Application again and reopen it with a baud rate of 9600. Issue the command to boot the image from flash.

switch: boot flash:c3750-ipbasek9-mz.122-50.SE3.bin

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