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New Member

flash failure during boot

If the flash fails during the boot process (not a bad image, but bad flash), what will happen during boot. Will POST fail, will it try to get an image from TFTP, do you get an rommon prompt?

Thank you


Re: flash failure during boot


It depends on the confguration of boot commands in your startup file

If everything is left at its default the router will boot to rommon as the boot router seeks to find the file in the following order.

flash --> TFTP --> Rommon

you can change the boot order by issuing the boot system command.

see the link for details



Re: flash failure during boot

It cannot look at the configuration file when it cannot even load the IOS. It will go to rommon and I do not think it will tell you that flash is bad, but you might get a "magic" number fail or something that might indicate a flash format error of some kind. It will go to rommon.

Please rate this posts if it helps.

New Member

Re: flash failure during boot

thank you

New Member

Re: flash failure during boot

does getting a rommon prompt mean it failed the POST test?

Re: flash failure during boot

NO, not necessarily. If the device goes directly to rommon, it just means it had no IOS to boot thus falling into rommon. The hardware could be perfectly fine but with no IOS to boot it will go to rommon.

New Member

Re: flash failure during boot

I'm still trying to understand what happens if flash is bad. Does Post fail, does it try and get an IOS from a TFTP server?

Re: flash failure during boot


Technically yes.




Re: flash failure during boot

I agreed w/ Roberto that if the flash failure, the POST still passed. But cannot load the image from flash. You can imagine that the image is crashed, when it is being load from the flash to the DRAM, it can't complete. So the image cannot be used and the router will try to look for another image in the network via TFTP. First of all, if you have basic configuration (e.g. IP address)& TFTP server w/ IOS image, then the TFTP will work, otherwise, if it is a clean config., you cannot download the image from TFTP.

Hope this helps.

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