Loading IOS on a switch or router via the console

If the flash has been deleted / formated and there is no IOS on the switch or router, you have to copy the new IOS via the console port.

the following article explains the procedure loading the IOS immage c2600-is-mz.122-15.ZJ2.bin on a cisco26xx router using teraterm

rommon 1 > xmodem -c c2600-is-mz.122-15.ZJ2.bin
Do not start the sending program yet...
File size Checksum File name
18699016 bytes (0x11d5308) 0x7234 c2600-is-mz.122-15.ZJ2.bin (bad checksum: 0x6683)

WARNING: All existing data in bootflash will be lost! Invoke this application only for disaster recovery. Do you wish to continue? y/n [n]: y
Ready to receive file c2600-is-mz.122-15.ZJ2.bin ...

now send file by clicking on the top menu: file-> transfer-> send-> xmodem - and chose the file from your local directory
the transfer should start now.

once the transfer has finished the flash will be erased and you will get a message like:
Erasing flash at 0x61780000.
this might take a while before it says something like:
program flash location 0x600d0000
which might also take a bit.....before it finally says:
'Download Complete!
and the router/switch should boot

the following article explains the procedure loading the IOS immage c3550-ipbasek9-mz.122-40.SE.bin on a WS-C3550 series switch using teraterm

switch: copy xmodem: flash:c2955-i6q4l2-mz.121-13.EA1.bin Begin the Xmodem or Xmodem-1K transfer now... CCC

now send file by clicking on the top menu: file-> transfer-> send-> xmodem - and chose the file from your local directory
the transfer should start now.