What command can be used to disable STP Portfast on a specific interface?

To disable Spanning Tree Protocol (STP) PortFast on a specific interface, the command "spanning-tree portfast disable" is used. This command specifically instructs the switch to disable PortFast on the interface, which, by default, allows connected devices to begin transmitting data immediately without going through the typical STP listening and learning states.

When PortFast is disabled, the interface resumes normal spanning tree operation, which includes participating in the STP process and waiting for the appropriate states to ensure a loop-free environment. This is important in various network setups, especially where there could be potential loops introduced by misconfigured devices.

Using this command helps maintain proper network behavior by controlling the usage of PortFast on interfaces that require traditional STP functions. Other options do not follow the correct syntax required by Cisco IOS, making them invalid for disabling PortFast.