What are two reasons lo configure PortFast on a switch port attached to an end host? (Choose two.)

The Spanning Tree Protocol (STP) PortFast feature is configured on switch ports connected to end devices, such as PCs or servers. Its primary purpose is to allow these ports to bypass the usual STP listening and learning states, which together cause a 30-second delay. By enabling PortFast, the port transitions directly to the forwarding state, ensuring immediate network connectivity for the host (Option C). A second key benefit is that link state changes (up/down) on a PortFast-enabled port do not trigger a Topology Change Notification (TCN). This prevents the switch from unnecessarily flushing its MAC address table and flooding frames, which protects the stability of the overall network topology from routine host reboots (Option B).

A. Limiting the number of learned MAC addresses is a function of the port security feature, not PortFast.

D. A PortFast-enabled port still participates in STP. It continues to listen for BPDUs to prevent loops if a switch is inadvertently connected.

E. Blocking communication is the opposite of PortFast's function; PortFast is designed to accelerate, not prevent, connectivity for end hosts.

1. Odom

W. (2019). CCNA 200-301 Official Cert Guide

Volume 1. Cisco Press.

Chapter 8

"Spanning Tree Protocol Concepts

" Section "PortFast and BPDU Guard": "PortFast causes the switch to put the port in a forwarding state immediately when the interface becomes physically active... When a PortFast-enabled interface fails or is brought back online

the switch does not perform a TCN." This directly supports options C and B.

2. Cisco Systems

Inc. (2023). Spanning Tree Protocol Configuration Guide

Cisco IOS XE Cupertino 17.9.x (Catalyst 9300 Switches).

Section: "Port Fast": "Port Fast immediately brings an interface to the forwarding state from a blocking state

bypassing the listening and learning states... If a link on a Port Fast-enabled interface goes down

the switch does not send a TCN message." This document confirms that PortFast provides immediate forwarding (supporting C) and suppresses TCNs (supporting B). It also states

"Although the interface is immediately brought to the forwarding state

the interface still participates in spanning tree

" which explicitly refutes option D.