If your terminal program supports kermit, you can proceed from here. When U-Boot is loaded you will see LF1000# Loading Kernel General. (This will queue up the file for transmission.) Trigger the transmission of this file by pressing any button on the device. NOTE: Windows Terminal Users must select S to use Xmodem. For example, users who have set their transfer protocol to Zmodem would type Z. Enter the letter associated with the correct transfer protocol on the menu. Optional: you may want to 'format flash:' to make sure you have enough free space. Connect to the console port of the switch using the Cisco console cable and set your baud rate to 9600.
Download something like HyperTerminal that support sending files via XModem.
