Start up a Cisco IOS quickly without TFTP
While upgrading my IOS to 12.4T on my 3750, the IOS must have gotten corrupted,because on my reload I got this:
Readonly ROMMON initialized program load complete, entry point: 0x80008000, size: 0xcac0 loadprog: bad file magic number: 0x0 boot: cannot load "flash:c3725-adventerprisek9-mz.124-15.T9.bin
So I tried to load an IOS via TFTP server in ROMmon mode, but my ROMmon was 12.2, so that was out of the question.
I could xmodem it... but that takes a really long time, which I didn't have at the time.
I upgraded 3 3750s and I took one of them off the rack, took the flash out, and put it into slot0 and then rebooted the router and the IOS from slot0 came up.
After, I tried to verify the hash of the IOS
router#verify flash:c3725-adventerprisek9-mz.124-15.T9.bin router#
nothing... came up.
When I verify the same file from slot0, it works.
router#verify slot0:c3725-adventerprisek9-mz.124-15.T9.bin Verifying file integrity of slot0:c3725-adventerprisek9-mz.124-15.T9.bin.. ........... lots of dots later..............................Done! Embedded Hash MD5 : AE963FE294C20FAAA7B65C1F02E0E3FF Computed Hash MD5 : AE963FE294C20FAAA7B65C1F02E0E3FF CCO Hash MD5 : 3FA5B289DC2E9C1D760778200BA6465D
So I deleted the corrupted IOS and copied the one from slot0 over.
router#delete flash:c3725-adventerprisek9-mz.124-15.T9.bin Delete filename [c3725-adventerprisek9-mz.124-15.T9.bin]? Delete flash:c3725-adventerprisek9-mz.124-15.T9.bin? [confirm] router#copy slot0:c3725-adventerprisek9-mz.124-15.T9.bin flash: Destination filename [c3725-adventerprisek9-mz.124-15.T9.bin]? Copy in progress...CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
Verify the new file is good
router#verify flash:c3725-adventerprisek9-mz.124-15.T9.bin Embedded Hash MD5 : AE963FE294C20FAAA7B65C1F02E0E3FF Computed Hash MD5 : AE963FE294C20FAAA7B65C1F02E0E3FF CCO Hash MD5 : 3FA5B289DC2E9C1D760778200BA6465D
Then take the memory card out of slot0 (you can do this while its running) and reboot.
I have never had a corrupted IOS, but I will verify from now on before rebooting.
Reading around, I didn't find this solution anywhere, and its by far the fastest one (if tftp isn't working). I think it might even be faster than tftp for some people, depending on if you have to set a tftp server up or not. Total time spent: about 15min.