When router is fully configured but you want to delete any interface configuration alone, use the default interface command:

router(config)#default interface serial0

This deletes all the configurations under that interface and saves you from using the no form of the reverse command to disable the functionality.

Upgrading IOS

You can upgrade your IOS image by configuring a router as Trivial File Transfer Protocol (TFTP) server, and download the IOS image directory from that router. You can configure a router as a TFTP server with the following command:

router(config)# tftp-server flash:

If you have cisco router tips that you want to share just send them to admin at seoroot dot com.