Start a Port Configuration In a Clean State

If you are reconfiguring or changing the port settings on a router you can remove or change the old commands one by one until the job is done. However, there's a "default interface" command that you can use to quickly reset the port's configuration to its default values:

Router(config#): default interface fa0/1

Once the "default interface"command issued, you can be certain that all previous commands set on the specified ports are gone.