Friday, June 14, 2013

Cisco Router: IOS 15 Upgrade Gone Bad

Well, this was a surprise to me.  I had a router with the IOS of 15.1.?? (I dont recall exactly which is was), but I needed to overcome a NAT problem in particular that I thought was an IOS bug.  So, I did an upgrade to version c2900-universalk9-mz.SPA.153-2.T.bin.  To my surprise, once I tftp'ed the .bin file, put in the boot sys flash:c2900-universalk9-mz.SPA.153-2.T.bin statement, and typed reload, the router booted up to the initial configuration prompt.  WOW.  I was not expecting that.  Im not sure what happened exactly, but I quickly tftp'ed the 'sh run' I had taken before and got them up quickly.  Very surprising.  I dont think that is normal, but I at least wanted to share the experience with you all.


  1. Check the config register and make sure it was not set to ignore the startup config . Register should normally be 0x2101 or x2102 . if its something other than that it may be ignoring the startup config. Possibly because it was changed at one time for password recovery.

    1. Yeah, I put this router in about a month ago or so. I think out should have come by default as 0x2102. I thinkI had also rebooted this router in the past. Good comments though.


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