What will happen when I run this command on the router ?

this command used to copy the image from the router to a tftp server ( backup )

first of all question is incomplete....  you must define the tftp server address too. This command is for IOS, CISCO devices to backup IOS image from local flash drive to the desired tftp server.

#copy flash tftp command is used to copy IOS from Flash to TFTP server. It takes three parameters. Source filename :- Name of IOS file that need to be copied. Address or name of remote host :- IP address of TFTP Server. ( To use name we need to configure DNS service on router. ) Destination filename :- Name of file used at destination to store the source file.

This command use to copy file from flash to remote tftp

it will ask you the Destination IP/name, and the the name of the file you want to create in the desitnation

This command is used for Backup, to store image file to server.

 

used to copy files from flash directory to remote tftp server...

most of the times used to backup ios image but not limited to...

I think it's not completed command 

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To transfer an ios image from the flash memoey.

tftp server is usually used for backup files. after entering the above command the router will load ios backup from tftp server.