3750 failed IOS upgrade

[benwilliams322]

I have two 3750 switches setup in a stack configuration. The internal flash can only handle one IOS due to size limitations. The new IOS was pushed to one switch then copied to the other. I performed a "verify" on both switch flash devices and it completed sucessfully. I also did the verify command with the "/md5" flag and got the same output for both images. To me this says the image was readable in flash.

Upon reload, one switch started to loadthe IOS then quit halfway through and was unable to boot. That switch is now without an IOS. The other switch worked just fine. The failed switch did say there was an inconsistent sector list when trying to initialize flash on reboot.

My question is: does the verify command actually go and read the image on flash? If so, why would that complete successfully but not be able to boot the image?

[Leo Laohoo]

I also did the verify command with the "/md5" flag and got the same output for both images. To me this says the image was readable in flash.

When you download the IOS, you will find the MD5 hash value.  You use the command "verify /md5" and compare the value of this command to the value found at the Cisco website.  If it's not the same, then you know there's an issue.

For 3750 with up to 16mb of flash, the highest IOS you can go is the 12.2(55)SEn.  Otherwise you'll need to download the "lite" version.  This IOS has the "lmk" found in the filename.