What command is used to enable Portfast on a specific switch port?

The command to enable PortFast on a specific switch port is "spanning-tree portfast." This command is used in interface configuration mode on Cisco switches to activate PortFast directly on that interface.

PortFast is a feature that allows a switch port to transition directly into the forwarding state when a device connects to it, thus reducing the time it takes for the switch to start forwarding traffic on that port. Normally, switch ports participate in the Spanning Tree Protocol (STP) and undergo a series of state transitions (listening, learning, and then forwarding) to prevent loops in the network. Enabling PortFast bypasses these states, which is particularly useful for port connections to end devices like computers or printers, where there is no risk of loops.

While some of the other options listed may seem plausible, they do not accurately represent the command used for enabling PortFast. There is no command such as "spanning-tree portfast enable," "spanning-tree portfast config," or "spanning-tree portfast start" in Cisco IOS for this specific functionality. Understanding the proper syntax is essential for correct command implementation in a network configuration context.