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Unable to Boot From disk0:

Vijaya Lakshmi
Cisco Employee
Cisco Employee

                   Customer is using SUP720 with SP rommon image version 8.1(3), he is trying to boot the new ios image from disk0, but he gets invalid magic error. he fomat the disk0 but still he gets error when he boots from disk0. He suspect that it can't be flash problem but can be software of hardware as he has two flash with same issue on 2 switches.

Customer wanted to recreate, I tried in the lab, i was able to load from disk0, but sup in lab had 8.5(4).

Customer wanted me try with 8.1(3) version. But i was unable to downgrade the SP Rommon image. SP rommon is running in Gold region and I loaded the 8.1(3) from both disk0 and sup-bootdisk, even preferrence was given to region1 but still sup came up with gold region itself

kindly answer my below questions.

* Will i be able to downgrade from 8.5(4) to 8.1(3), if so help me out with steps.

* is there any limitation or bug where  8.1(3) will be unable to read disk0.

4 Replies 4

Leo Laohoo
VIP Community Legend VIP Community Legend
VIP Community Legend

Invalid Magic Number normally means the IOS is corrupted or "not complete".  Compare the MD5 hash value of the file from the Cisco Download website by using the command "verify /md5 disk0:.bin".

Ivan Shirshin
Cisco Employee
Cisco Employee


I could not find any bugs like that but there were a lot of bug fixes and enhancements between this 2 ROMMONs. See the release notes for the list of caveats fixed in 8.5(4):

So it is recommended that customer upgrade his ROMMON to newer version.

About the downgrade instructions - did you try the regular procedure for changing ROMMON version on sup720?

And the "Invalid Magic Number" could mean either corrupted image file (verify the checksum), problem with flash (you can try to format it) or PCMCIA slot itself (only replacement).

Kind Regards,

**Please grade this post if you find it useful.

Kind Regards,

Thanks for all your response.

I verified the MD5 value its correct, sup is able to identify the disk0 but unable to boot from it.

i followed the same procedure which is mentioned in the below link. but no change

Customer was been advice to change the Flash but it wants to check whether its Software/Firmware issue.

Kindly advice.

I verified the MD5 value its correct, sup is able to identify the disk0 but unable to boot from it.

Stupid question:  Did someone FORMAT the CF first before putting an IOS into it?

Can you console into the supervisor line card and reload?  Post the entire bootup process.  This I got to see! 

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