- A
Root Guard is applied to a port that should never become a root port; if a superior BPDU is received, the port is placed into a root-inconsistent state.
Root Guard forces a port to be a designated port. When a superior BPDU is received, the port enters a root-inconsistent (blocked) state to prevent it from becoming a root port.
- B
Loop Guard is used on root ports to monitor BPDU reception; if BPDUs stop, the port is immediately placed into forwarding mode to maintain connectivity.
Why wrong: This is incorrect. Loop Guard is applied to alternate or backup ports (non-designated ports), not root ports. When BPDUs stop, the port is placed into a loop-inconsistent (blocked) state, not forwarding.
- C
BPDU Guard is typically configured on access ports and error-disables the port if a BPDU is received, protecting against unauthorized switch connections.
BPDU Guard is designed for access ports. If a BPDU is received (indicating a potential switch connection), the port is error-disabled, preventing bridging loops and unauthorized access.
- D
Root Guard and BPDU Guard can be enabled simultaneously on the same port to provide both root protection and BPDU filtering.
Why wrong: This is incorrect. Root Guard and BPDU Guard have conflicting effects on a port. Root Guard allows BPDU processing (to detect superior BPDUs), while BPDU Guard disables the port upon receiving any BPDU. They cannot be used together on the same port.
- E
Loop Guard is only effective when configured on ports that are in a blocking state; it prevents them from transitioning to forwarding if BPDUs are not received.
Why wrong: Loop Guard is applied to ports that are in a blocking state (alternate or backup ports). If BPDUs stop arriving, the port stays in a loop-inconsistent state (blocked) rather than transitioning to forwarding, thus preventing loops.
Quick Answer
The correct answer identifies Root Guard placing a port into a root-inconsistent state upon receiving a superior BPDU, and BPDU Guard error-disabling an access port if any BPDU is received. Root Guard is applied to designated ports that should never become root ports, and when a superior BPDU arrives, it blocks traffic by moving the port to a root-inconsistent state, preventing an unauthorized root bridge. BPDU Guard, typically enabled on access ports, immediately error-disables the port upon BPDU reception, protecting against rogue switch connections. On the CCNA 200-301 v2 exam, this topic tests your understanding of STP security mechanisms in Rapid PVST+, and a common trap is confusing Loop Guard’s behavior—it places a port into a loop-inconsistent state (blocked) when BPDUs stop, not into forwarding. Another key point is that Root Guard and BPDU Guard are mutually exclusive on the same port. For memory, think of Root Guard as “protecting the root role” and BPDU Guard as “shutting down unexpected BPDUs,” while Loop Guard “blocks when BPDUs go silent.”
CCNA Switching and Network Access Practice Question
This 200-301 practice question tests your understanding of switching and network access. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. 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.
Which TWO statements correctly describe the behavior of Root Guard, Loop Guard, and BPDU Guard in a Rapid PVST+ environment?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Root Guard is applied to a port that should never become a root port; if a superior BPDU is received, the port is placed into a root-inconsistent state.
Option A is correct because Root Guard, applied to a port that should never become a root port, places that port into a root-inconsistent state upon receiving a superior BPDU, blocking traffic to prevent an unauthorized root bridge. Option C is correct because BPDU Guard is typically configured on access ports and error-disables the port if any BPDU is received, protecting against rogue switch connections. Option B is incorrect: when BPDUs stop on a port with Loop Guard, the port is placed into a loop-inconsistent state (blocked), not immediately forwarded, to prevent loops. Option D is incorrect because Root Guard and BPDU Guard are mutually exclusive and cannot be enabled simultaneously on the same port due to conflicting protective behaviors. Option E is incorrect because Loop Guard is effective on any port that is expected to receive BPDUs, including root ports and alternate/backup ports; it is not limited to ports already in a blocking state, and the statement's use of 'only' makes it false.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Root Guard is applied to a port that should never become a root port; if a superior BPDU is received, the port is placed into a root-inconsistent state.
Why this is correct
Root Guard forces a port to be a designated port. When a superior BPDU is received, the port enters a root-inconsistent (blocked) state to prevent it from becoming a root port.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Loop Guard is used on root ports to monitor BPDU reception; if BPDUs stop, the port is immediately placed into forwarding mode to maintain connectivity.
Why it's wrong here
This is incorrect. Loop Guard is applied to alternate or backup ports (non-designated ports), not root ports. When BPDUs stop, the port is placed into a loop-inconsistent (blocked) state, not forwarding.
- ✓
BPDU Guard is typically configured on access ports and error-disables the port if a BPDU is received, protecting against unauthorized switch connections.
Why this is correct
BPDU Guard is designed for access ports. If a BPDU is received (indicating a potential switch connection), the port is error-disabled, preventing bridging loops and unauthorized access.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Root Guard and BPDU Guard can be enabled simultaneously on the same port to provide both root protection and BPDU filtering.
Why it's wrong here
This is incorrect. Root Guard and BPDU Guard have conflicting effects on a port. Root Guard allows BPDU processing (to detect superior BPDUs), while BPDU Guard disables the port upon receiving any BPDU. They cannot be used together on the same port.
- ✗
Loop Guard is only effective when configured on ports that are in a blocking state; it prevents them from transitioning to forwarding if BPDUs are not received.
Why it's wrong here
Loop Guard is applied to ports that are in a blocking state (alternate or backup ports). If BPDUs stop arriving, the port stays in a loop-inconsistent state (blocked) rather than transitioning to forwarding, thus preventing loops.
When this WOULD be correct
When you want to prevent temporary loops caused by unidirectional link failures on blocked ports.
Option-by-option analysis
Why each answer is right or wrong
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.
✓Root Guard is applied to a port that should never become a root port; if a superior BPDU is received, the port is placed into a root-inconsistent state.Correct answer▾
Why this is correct
Root Guard forces a port to be a designated port. When a superior BPDU is received, the port enters a root-inconsistent (blocked) state to prevent it from becoming a root port.
✗Loop Guard is used on root ports to monitor BPDU reception; if BPDUs stop, the port is immediately placed into forwarding mode to maintain connectivity.Wrong answer — click to see why▾
Why this is wrong here
Loop Guard is applied to non-designated ports (alternate or backup ports), not root ports. When BPDUs stop arriving, the port is placed into a loop-inconsistent state (blocked) to prevent loops, not into forwarding mode.
Why candidates choose this
Students may confuse Loop Guard with UplinkFast or other features that quickly transition ports to forwarding. They might think Loop Guard is used on root ports to maintain connectivity if BPDUs are lost, but its actual purpose is to prevent loops by keeping ports blocked.
✗Root Guard and BPDU Guard can be enabled simultaneously on the same port to provide both root protection and BPDU filtering.Wrong answer — click to see why▾
Why this is wrong here
Root Guard and BPDU Guard have conflicting behaviors: Root Guard allows BPDU processing to detect superior BPDUs, while BPDU Guard disables the port upon receiving any BPDU. They cannot be enabled simultaneously on the same port because their actions are mutually exclusive.
Why candidates choose this
Students might think that combining both features provides comprehensive protection, but they overlook the fact that BPDU Guard would error-disable the port before Root Guard can act, making Root Guard ineffective.
✗Loop Guard is only effective when configured on ports that are in a blocking state; it prevents them from transitioning to forwarding if BPDUs are not received.Wrong answer — click to see why▾
Why this is wrong here
Loop Guard is effective on ports that are in a blocking state (alternate or backup ports), but it does not prevent them from transitioning to forwarding; instead, if BPDUs stop, the port remains in a loop-inconsistent state (blocked) to prevent loops. The statement incorrectly implies that Loop Guard prevents transition, but it actually causes the port to stay blocked.
★ When this WOULD be the correct answer
When you want to prevent temporary loops caused by unidirectional link failures on blocked ports.
Why candidates choose this
Students may understand that Loop Guard is used on blocking ports but misinterpret its behavior. They might think it prevents the port from transitioning to forwarding, which is partially true, but the key is that it keeps the port blocked when BPDUs are lost, not that it prevents transition in general.
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
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that Loop Guard immediately forwards traffic when BPDUs stop, but in reality it blocks the port to prevent loops, and that Root Guard and BPDU Guard can coexist on the same port, which they cannot due to conflicting behaviors.
Detailed technical explanation
How to think about this question
Root Guard and BPDU Guard operate at different layers of STP protection: Root Guard is a per-port feature that reacts to superior BPDUs by transitioning the port to a root-inconsistent (blocking) state, while BPDU Guard is typically applied to PortFast-enabled access ports and error-disables the port upon BPDU reception to prevent switch loops. Loop Guard, in contrast, monitors for the cessation of BPDUs on non-designated ports and transitions them to a loop-inconsistent state to prevent forwarding loops caused by unidirectional link failures.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this 200-301 question test?
Switching and Network Access — This question tests Switching and Network Access — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Root Guard is applied to a port that should never become a root port; if a superior BPDU is received, the port is placed into a root-inconsistent state. — Option A is correct because Root Guard, applied to a port that should never become a root port, places that port into a root-inconsistent state upon receiving a superior BPDU, blocking traffic to prevent an unauthorized root bridge. Option C is correct because BPDU Guard is typically configured on access ports and error-disables the port if any BPDU is received, protecting against rogue switch connections. Option B is incorrect: when BPDUs stop on a port with Loop Guard, the port is placed into a loop-inconsistent state (blocked), not immediately forwarded, to prevent loops. Option D is incorrect because Root Guard and BPDU Guard are mutually exclusive and cannot be enabled simultaneously on the same port due to conflicting protective behaviors. Option E is incorrect because Loop Guard is effective on any port that is expected to receive BPDUs, including root ports and alternate/backup ports; it is not limited to ports already in a blocking state, and the statement's use of 'only' makes it false.
What should I do if I get this 200-301 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 2026
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