This 200-301 practice question tests your understanding of switching and network access. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. A key principle to apply: bPDU Guard immediately disables a PortFast-enabled access port upon receiving a BPDU to prevent Layer 2 loops caused by unexpected switch connections.. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
What is the main purpose of BPDU Guard on a PortFast-enabled access port?
To elect the root bridge faster
Why wrong: BPDU Guard does not speed root election.
To shut down an access port if a BPDU is received
Correct. That protects against unexpected switch connections on edge ports.
To convert all trunks to routed ports
Why wrong: BPDU Guard has nothing to do with routed ports.
To allow BPDUs only from trusted access points
Why wrong: That is not the function of BPDU Guard.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
To shut down an access port if a BPDU is received
BPDU Guard helps prevent accidental loops by shutting down a PortFast port if it receives a BPDU.
Key principle: BPDU Guard immediately disables a PortFast-enabled access port upon receiving a BPDU to prevent Layer 2 loops caused by unexpected switch connections.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
To elect the root bridge faster
Why it's wrong here
BPDU Guard does not speed root election.
When this WOULD be correct
If the question were about features that help in the Spanning Tree Protocol (STP) process, such as mechanisms to optimize root bridge election, then this option could be correct. For example, a question asking how to speed up STP convergence might consider mechanisms that influence root bridge election times.
To shut down an access port if a BPDU is received
Why this is correct
Correct. That protects against unexpected switch connections on edge ports.
Related concept
BPDU Guard immediately disables a PortFast-enabled access port upon receiving a BPDU to prevent Layer 2 loops caused by unexpected switch connections.
To convert all trunks to routed ports
Why it's wrong here
BPDU Guard has nothing to do with routed ports.
When this WOULD be correct
If the question were about the functionality of a feature that converts trunk ports to routed ports, such as when discussing Layer 3 switching capabilities or specific configurations in a routing context, option C could be correct.
To allow BPDUs only from trusted access points
Why it's wrong here
That is not the function of BPDU Guard.
When this WOULD be correct
In a different exam scenario, a question could ask about a feature that allows BPDUs only from specific trusted devices, such as a network with designated root bridges and specific access points, making this option correct.
Option-by-option analysis
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.
Why this is correct
Correct. That protects against unexpected switch connections on edge ports.
Why this is wrong here
This option is wrong because BPDU Guard does not participate in the election of the root bridge; its primary function is to protect the network from loops by disabling ports that receive BPDUs.
★ When this WOULD be the correct answer
If the question were about features that help in the Spanning Tree Protocol (STP) process, such as mechanisms to optimize root bridge election, then this option could be correct. For example, a question asking how to speed up STP convergence might consider mechanisms that influence root bridge election times.
Why candidates choose this
Candidates may find this option tempting because they might confuse BPDU Guard's role with other STP features that involve root bridge election, leading them to incorrectly associate it with improving election speed.
Why this is wrong here
Option C is incorrect because BPDU Guard does not convert trunks to routed ports; it is designed to protect against loops by disabling ports that receive BPDUs on access ports configured with PortFast.
★ When this WOULD be the correct answer
If the question were about the functionality of a feature that converts trunk ports to routed ports, such as when discussing Layer 3 switching capabilities or specific configurations in a routing context, option C could be correct.
Why candidates choose this
Candidates may be tempted by this option due to a misunderstanding of port roles and features, confusing BPDU Guard's purpose with other port configurations related to trunking and routing.
Why this is wrong here
This option is incorrect because BPDU Guard does not selectively allow BPDUs from trusted access points; instead, it is designed to disable the port if any BPDU is received, regardless of the source.
★ When this WOULD be the correct answer
In a different exam scenario, a question could ask about a feature that allows BPDUs only from specific trusted devices, such as a network with designated root bridges and specific access points, making this option correct.
Why candidates choose this
Candidates may find this option tempting because it suggests a mechanism for controlling BPDU traffic, which aligns with the concepts of network security and trust, leading them to mistakenly associate it with BPDU Guard's functionality.
Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Common exam traps
A common exam trap is selecting an answer that suggests BPDU Guard speeds up root bridge election or converts trunks to routed ports. Candidates may confuse BPDU Guard with other STP features or port configurations. BPDU Guard’s sole function is to shut down a PortFast-enabled access port if it receives a BPDU, signaling an unexpected switch connection. Misunderstanding this can lead to choosing incorrect options that describe unrelated behaviors, such as root bridge election acceleration or trusted BPDU filtering, which are not functions of BPDU Guard.
Detailed technical explanation
Bridge Protocol Data Units (BPDUs) are special frames exchanged by switches to maintain Spanning Tree Protocol (STP), which prevents Layer 2 loops in a network. PortFast is a Cisco feature that immediately transitions a switch port into the forwarding state, bypassing the usual STP listening and learning states. This is typically enabled on access ports connected to end devices to speed up connectivity. However, if a BPDU is received on a PortFast-enabled port, it indicates that another switch might be connected, which could cause loops if not handled properly. BPDU Guard is a security feature designed to protect the network by shutting down a PortFast-enabled access port immediately upon receipt of a BPDU. This prevents accidental or malicious introduction of switches into the network topology on edge ports, which are expected to connect only to end devices. By disabling the port, BPDU Guard helps maintain STP stability and prevents potential Layer 2 loops that could disrupt network operations. A common exam trap is misunderstanding BPDU Guard’s role as a mechanism to speed up root bridge election or to manage trunk ports. BPDU Guard does not influence root bridge election timing nor does it convert ports to routed interfaces. Instead, it strictly protects PortFast ports by shutting them down if unexpected BPDUs arrive. In practical networks, enabling BPDU Guard on access ports ensures that any misconfiguration or unauthorized switch connection is quickly isolated, maintaining network integrity and avoiding broadcast storms caused by loops.
Key takeaway
BPDU Guard immediately disables a PortFast-enabled access port upon receiving a BPDU to prevent Layer 2 loops caused by unexpected switch connections.
Real-world example
A help-desk technician troubleshoots why a newly connected PC cannot reach shared printers on the same floor. The cable is good, the switch port is active, but the PC is in VLAN 20 and the printers are in VLAN 10. The uplink trunk only allows VLAN 10. A trunk being up does not mean every VLAN crosses it.
What to study next
Review bPDU Guard immediately disables a PortFast-enabled access port upon receiving a BPDU to prevent Layer 2 loops caused by unexpected switch connections., then practise related 200-301 questions on the same topic to reinforce the concept.
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FAQ
Switching and Network Access — This question tests Switching and Network Access — BPDU Guard immediately disables a PortFast-enabled access port upon receiving a BPDU to prevent Layer 2 loops caused by unexpected switch connections..
The correct answer is: To shut down an access port if a BPDU is received — BPDU Guard helps prevent accidental loops by shutting down a PortFast port if it receives a BPDU.
Review bPDU Guard immediately disables a PortFast-enabled access port upon receiving a BPDU to prevent Layer 2 loops caused by unexpected switch connections., then practise related 200-301 questions on the same topic to reinforce the concept.
BPDU Guard immediately disables a PortFast-enabled access port upon receiving a BPDU to prevent Layer 2 loops caused by unexpected switch connections.
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Last reviewed: May 17, 2026
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