To configure a switchport as an RSTP edge port, which command is used?

To configure a switchport as an RSTP edge port, the command used is "spanning-tree portfast." This command enables the port to immediately transition into the forwarding state when it comes up, bypassing the usual listening and learning states of the Spanning Tree Protocol (STP).

Using "spanning-tree portfast" is particularly useful for ports connected to end devices like workstations, printers, or servers, where rapid transition to the forwarding state is beneficial to minimize delays in data communication. It ensures that these devices can start sending and receiving traffic without the potential delays introduced by STP's default port state transitions.

The other options do not correctly configure the port for RSTP edge behavior. "Spanning-tree edge" is not a valid command, "spanning-tree bpduenable" relates to the handling of Bridge Protocol Data Units (BPDUs) but does not set a port as an edge port, and "spanning-tree mode edge" is also not a recognized configuration command in Cisco IOS. Therefore, "spanning-tree portfast" is the correct command for this operation.