Catalyst 2950 Magic number mismatch ?

Answered Question
Jun 19th, 2010


For my CCNA training I have ordered some good old CISCO products

But one of the switches that I have received do not want to boot

I have try to google and try many things this week-end , but without success.

When I take a look in the DIR FLASH:

I can see only c2950-i6Q4l2-mz.121-20.EA1a.bin

when I take a look in the SET

I have nothing , even the MAC address is not present.

Off course I have try :



but still the set stay empty.

Any help is welcome.

Thank you in advance.

Best Regards,


I have this problem too.
0 votes
Correct Answer by Leo Laohoo about 6 years 7 months ago

The IOS is corrupt.

Xmodem Console Download Procedure Using ROMmon

Hope this helps.  Please don't forget to rate useful post.  Thanks.

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Overall Rating: 5 (2 ratings)
Didier1966 Sun, 06/20/2010 - 01:13

Thank You for your prompt reply

I have deleted the IOS file and have copy one of my working switches to it , but still I have the same problem.

What I found strange is that on all my other switches , when I press SET , I can see the serial numbers and devices numbers, etc.

Can this not be the problem , that the IOS does not know if he has 12 , 24 or 48 ports ?

Do I have to key in is SET all the missing values ?

PS: Unfortunately ,I do not have the right "yet" to open your link , but I think it is the one where the explain how to recover a CATALYST 2950 with XMODEM , but this one I tried already

Thank you again for your help

Best Regards,


Didier1966 Sun, 06/20/2010 - 06:07


Just in case some other ones do the same mistake like I did :

When you have this kind of problem or error and you have to use XMODEM , please be aware that you have many options to send your file.

In my case I use ZTERM on my MAC and by default the setting was on : SMART MAC BINARY

I have change it to BINARY DATA , and it works great

The reason why I was looking in this XMODEM settings , where due to that I have two SWITCHES CATALYST 2950 with the same IOS.

When I compare both binary sizes the one that was working has 3117390 , and the one that has the MAGIC NUMBER MISMATCH has 3117568.

So we can conclude that the MAGIC NUMBER MISMATCH is a kind of wrong check sum.

I hope this will be useful for the ones that have the same problem

Best Regards,



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