Switches do not just use STP once and never again. The switches continually watch for changes. Those changes can be because a link or switch fails or it can be a new link that can now be used. The configuration can change in a way that changes the STP topology. This section briefly discusses the kinds of things that change the STP topology, either through configuration or through changes in the status of devices and links in the LAN.
The network engineers can choose to change the STP settings to then change the choices STP makes in a given LAN. Two main tools available to the engineer are to configure the BID and to change STP port costs.