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: portFast immediately transitions an access port to the forwarding state, bypassing STP's listening and learning states to speed up device connectivity.. 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.
Why is BPDU Guard commonly enabled on PortFast-enabled access ports?
To make STP root election happen faster
Why wrong: BPDU Guard is a protection feature, not a speed optimization for root election.
To disable STP permanently on access ports
Why wrong: STP is not permanently disabled.
To err-disable a port if it receives unexpected BPDUs
That is the core purpose of BPDU Guard.
To allow only one MAC address on the access port
Why wrong: That would be port security.
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 err-disable a port if it receives unexpected BPDUs
PortFast ports are meant for end devices, not for switches. BPDU Guard protects the LAN by shutting down a PortFast port that unexpectedly starts receiving BPDUs, which usually means an unauthorized switch was connected.
Key principle: PortFast immediately transitions an access port to the forwarding state, bypassing STP's listening and learning states to speed up device connectivity.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
To make STP root election happen faster
Why it's wrong here
BPDU Guard is a protection feature, not a speed optimization for root election.
When this WOULD be correct
In a scenario where the exam question asks about methods to optimize STP performance and mentions features that can enhance the speed of root bridge election, this option could be correct if it was framed around a hypothetical technology that accelerates STP processes.
To disable STP permanently on access ports
Why it's wrong here
STP is not permanently disabled.
When this WOULD be correct
In a different exam scenario, if the question asked about a feature that disables STP on access ports to prevent any STP-related traffic, this option could be correct. For example, a question could specify a configuration where STP is not needed due to a specific network design.
To err-disable a port if it receives unexpected BPDUs
Why this is correct
That is the core purpose of BPDU Guard.
Related concept
PortFast immediately transitions an access port to the forwarding state, bypassing STP's listening and learning states to speed up device connectivity.
To allow only one MAC address on the access port
Why it's wrong here
That would be port security.
When this WOULD be correct
In a different exam scenario, if the question asked about the purpose of MAC address filtering on access ports, option D could be correct. For example, a question could state, 'What is the function of limiting MAC addresses on an access port?' where the correct answer would be to allow only one MAC address.
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
That is the core purpose of BPDU Guard.
Why this is wrong here
BPDU Guard is a security feature that err-disables a port upon receiving BPDUs; it does not accelerate root election. Root election speed is influenced by STP timers and bridge priorities, not BPDU Guard.
★ When this WOULD be the correct answer
In a scenario where the exam question asks about methods to optimize STP performance and mentions features that can enhance the speed of root bridge election, this option could be correct if it was framed around a hypothetical technology that accelerates STP processes.
Why candidates choose this
The name 'Guard' might suggest it protects or speeds up STP processes, but its purpose is purely protective, not performance-related.
Why this is wrong here
BPDU Guard does not disable STP permanently; it only reacts to BPDU reception by err-disabling the port. STP remains active on other ports, and the port can be re-enabled after the violation is resolved.
★ When this WOULD be the correct answer
In a different exam scenario, if the question asked about a feature that disables STP on access ports to prevent any STP-related traffic, this option could be correct. For example, a question could specify a configuration where STP is not needed due to a specific network design.
Why candidates choose this
Students may confuse BPDU Guard with disabling STP because it prevents BPDU processing on the port, but STP is still running globally and on other ports.
Why this is wrong here
Limiting MAC addresses on a port is the function of port security, not BPDU Guard. BPDU Guard specifically monitors for BPDU frames and takes action if any are received.
★ When this WOULD be the correct answer
In a different exam scenario, if the question asked about the purpose of MAC address filtering on access ports, option D could be correct. For example, a question could state, 'What is the function of limiting MAC addresses on an access port?' where the correct answer would be to allow only one MAC address.
Why candidates choose this
Both features are commonly applied to access ports for security, leading to confusion between BPDU Guard and port security's MAC address limiting.
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
Don't confuse BPDU Guard with PortFast or BPDU filtering; each has distinct roles.
Detailed technical explanation
Spanning Tree Protocol (STP) is designed to prevent Layer 2 loops in a switched network by selectively blocking redundant paths. 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 intended for access ports connected to end devices, such as workstations or servers, where no switching loops are expected. However, if a PortFast-enabled port receives Bridge Protocol Data Units (BPDUs), it indicates that another switch or bridging device is connected, which could cause loops. BPDU Guard is a security feature that protects the network by err-disabling a PortFast-enabled port if it receives unexpected BPDUs. This behavior prevents potential Layer 2 loops caused by unauthorized switches connecting to access ports. When BPDU Guard is enabled, the port shuts down immediately upon receiving a BPDU, effectively isolating the potential loop source and maintaining network stability. A common exam trap is misunderstanding BPDU Guard as a feature that speeds up STP convergence or disables STP permanently on access ports. In reality, BPDU Guard only acts as a protective mechanism to err-disable ports receiving BPDUs unexpectedly. Practically, enabling BPDU Guard on PortFast ports ensures that only end devices connect to these ports, preventing accidental or malicious introduction of switches that could disrupt the STP topology.
Key takeaway
PortFast immediately transitions an access port to the forwarding state, bypassing STP's listening and learning states to speed up device connectivity.
Real-world example
A practitioner preparing for the 200-301 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. PortFast immediately transitions an access port to the forwarding state, bypassing STP's listening and learning states to speed up device connectivity. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Review portFast immediately transitions an access port to the forwarding state, bypassing STP's listening and learning states to speed up device connectivity., 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 — PortFast immediately transitions an access port to the forwarding state, bypassing STP's listening and learning states to speed up device connectivity..
The correct answer is: To err-disable a port if it receives unexpected BPDUs — PortFast ports are meant for end devices, not for switches. BPDU Guard protects the LAN by shutting down a PortFast port that unexpectedly starts receiving BPDUs, which usually means an unauthorized switch was connected.
Review portFast immediately transitions an access port to the forwarding state, bypassing STP's listening and learning states to speed up device connectivity., then practise related 200-301 questions on the same topic to reinforce the concept.
PortFast immediately transitions an access port to the forwarding state, bypassing STP's listening and learning states to speed up device connectivity.
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Last reviewed: May 17, 2026
This 200-301 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 200-301 exam.
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