In an access layer switch design you have an interface that connects only to a single server and you want spanning tree to move that port to the forwarding state immediately without the usual listening and learning delays. Which Cisco IOS command should be applied to the interface to achieve this behavior?

Introduction / Context:
This question deals with Spanning Tree Protocol configuration on Cisco switches, specifically in the context of access ports that connect only to end devices such as servers or workstations. While spanning tree is important for preventing loops, waiting through the full listening and learning states can delay link availability. Cisco provides a feature called PortFast to accelerate port transition for edge connections that are not expected to form loops.

Given Data / Assumptions:
- The port in question connects directly to a single server and is not part of any physical switching loop.
- The goal is to bypass the normal spanning tree listening and learning delays on that interface so that it rapidly enters the forwarding state.
- The underlying spanning tree topology should still run in the rest of the network.
- We are looking for the Cisco IOS interface command that enables this behavior.

Concept / Approach:
On Cisco switches, the spanning-tree portfast command is used on access ports to allow them to transition quickly to the forwarding state. PortFast is intended only for ports connected to end hosts, not for trunk links between switches, because enabling it on links that can form loops can cause network instability. PortFast does not completely disable spanning tree; rather, it changes how the port behaves during startup, making it ideal for server or workstation connections.

Step-by-Step Solution:
Step 1: Identify that an access port connected to a single server is a typical candidate for PortFast.Step 2: Recall that the Cisco IOS command to enable this feature on an interface is spanning-tree portfast.Step 3: Understand that this command is applied in interface configuration mode, not in global configuration mode.Step 4: Recognize that the other listed commands either do not exist, are incomplete, or would disable spanning tree inappropriately.Step 5: Choose spanning-tree portfast as the correct answer.

Verification / Alternative check:
In practice, administrators often see messages on the console when enabling PortFast, warning that it should be used only on ports connected to a single host. When a device is plugged in, the port quickly transitions to forwarding, reducing issues such as delayed Dynamic Host Configuration Protocol assignment. This real world behavior aligns exactly with the description in the question.

Why Other Options Are Wrong:
The options disable spanning tree and spanning tree off are not valid Cisco IOS commands and, even if they existed, would be dangerous if they globally disabled spanning tree. The command spanning tree security does not represent a real feature in this syntax. The configuration no spanning tree vlan 1 would attempt to disable spanning tree for a particular VLAN rather than speeding up port activation, which is not the requirement here.

Common Pitfalls:
One common pitfall is to misunderstand PortFast as disabling spanning tree entirely on the port. In reality, spanning tree still runs and can block the port if a loop is detected. Another mistake is to enable PortFast on trunk ports between switches, which can lead to serious loop problems. Always reserve PortFast for access ports that are expected to connect only to end hosts.

Final Answer:
The correct interface command is spanning-tree portfast, which causes the server facing port to transition immediately to the forwarding state.