Modifying an interface configuration can be as tedious as picking white cat hair off a black cashmere sweater. Typically, in order to remove unwanted items you have to go through each individual line and put “no” in front. If you need to completely re-do the configuration or are faced with a laundry list of changes, it is simpler and faster to restore the default configuration. Furthermore, it will reduce potential oversight errors.
To reset the interface use the command “default interface.” For example: “rtr(config)#default interface serial 0/0/0”. Keep in mind this will remove all existing commands and shut down the interface.