Router(config)#boot system tftpimage-name172.16.10.3
Loads IOS with image-name from a TFTP server
Router(config)#boot system rom
Loads IOS from ROM
Router#copy run start
Saves running-configuration to NVRAM. Router will execute commands in order they were entered on next reload
If you enter boot system flash first, that is the first place the router will go to look for the IOS. If you want to go to a TFTP server first, make sure that the boot system tftp command is the first one you enter.