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Question 697 of 1,052
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CCNA Practice Question: Which TWO statements correctly describe the…
This 200-301 practice question tests your understanding of 200-301 exam topics. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. 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 configuration and effect of Root Guard and BPDU Guard on a Cisco switch?
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 configured on a per-port basis and causes the port to become root-inconsistent if a superior BPDU is received.
Root Guard prevents a designated port from becoming a root port by placing it in a root-inconsistent state if superior BPDUs are received, which blocks traffic on that port. BPDU Guard places an access port in errdisable state if a BPDU is received, protecting against unauthorized switches. Option A is correct because Root Guard works on designated ports. Option D is correct because BPDU Guard is typically applied to PortFast-enabled access ports. Options B, C, and E are incorrect: BPDU Guard does not prevent loops on trunk ports (that's Loop Guard), Root Guard does not use errdisable (it uses root-inconsistent), and BPDU Guard does not filter BPDUs (it reacts to them).
Key principle: A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
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 configured on a per-port basis and causes the port to become root-inconsistent if a superior BPDU is received.
Why this is correct
Root Guard is applied to a port (usually a designated port) and if a better BPDU arrives, the port enters a root-inconsistent state, blocking traffic and preventing the switch from becoming root.
Related concept
Access ports place end devices into a single VLAN.
- ✗
BPDU Guard prevents loops by disabling a trunk port that receives a BPDU from an unauthorized switch.
Why it's wrong here
BPDU Guard is applied to access ports (often with PortFast) and places the port in errdisable state if any BPDU is received; it does not target trunk ports or specifically prevent loops—that is the role of Loop Guard.
- ✗
Root Guard places a port in errdisable state when a superior BPDU is received.
Why it's wrong here
Root Guard uses a root-inconsistent state (not errdisable) to block traffic while still allowing the port to recover automatically when the superior BPDUs stop.
- ✓
BPDU Guard is commonly enabled on ports where PortFast is configured to prevent unexpected BPDUs from causing a bridging loop.
Why this is correct
BPDU Guard is often used with PortFast on access ports to immediately error-disable the port if a BPDU is received, preventing potential loops from unauthorized devices.
Related concept
Access ports place end devices into a single VLAN.
- ✗
Both Root Guard and BPDU Guard filter BPDUs to prevent them from being processed by the switch CPU.
Why it's wrong here
Neither Root Guard nor BPDU Guard filters BPDUs. Root Guard reacts to superior BPDUs by changing port state, and BPDU Guard reacts by error-disabling the port. They do not prevent BPDUs from reaching the CPU.
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 configured on a per-port basis and causes the port to become root-inconsistent if a superior BPDU is received.Correct answer▾
Why this is correct
Root Guard is applied to a port (usually a designated port) and if a better BPDU arrives, the port enters a root-inconsistent state, blocking traffic and preventing the switch from becoming root.
✗BPDU Guard prevents loops by disabling a trunk port that receives a BPDU from an unauthorized switch.Wrong answer — click to see why▾
Why this is wrong here
BPDU Guard is not used on trunk ports and its primary purpose is to protect against unauthorized switches, not to prevent loops. Loop Guard prevents loops by detecting unidirectional links.
✗Root Guard places a port in errdisable state when a superior BPDU is received.Wrong answer — click to see why▾
Why this is wrong here
Errdisable is used by BPDU Guard, not Root Guard. Root Guard's state is root-inconsistent, which is a blocking state that can be automatically cleared.
✗Both Root Guard and BPDU Guard filter BPDUs to prevent them from being processed by the switch CPU.Wrong answer — click to see why▾
Why this is wrong here
Filtering BPDUs is not a function of these features; they are reactive mechanisms that change port behavior when BPDUs are received.
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: an active trunk can still block the VLAN you need
A trunk being up does not prove every VLAN is crossing it. Check allowed VLAN lists, native VLAN mismatch, VLAN existence and access-port assignment.
Detailed technical explanation
How to think about this question
VLAN questions usually combine access-port and trunking clues. The key is to identify whether the issue is local to one switchport, caused by the trunk, or caused by the VLAN not existing where it needs to exist.
KKey Concepts to Remember
- Access ports place end devices into a single VLAN.
- Trunk ports carry multiple VLANs between switches.
- Allowed VLAN lists decide which VLANs can cross a trunk.
- Native VLAN mismatch can create confusing symptoms.
TExam Day Tips
- Use show vlan brief to verify access VLANs.
- Use show interfaces trunk to verify trunk state and allowed VLANs.
- Do not treat every same-VLAN issue as a routing problem.
Key takeaway
A trunk being up does not mean the VLAN is allowed across it. Always verify the allowed VLAN list and whether the VLAN exists on both switches.
Real-world example
How this comes up in practice
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
Got this wrong? Here's your next step.
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-301 questions on switching, trunking, and access-port configuration.
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FAQ
Questions learners often ask
What does this 200-301 question test?
Access ports place end devices into a single VLAN.
What is the correct answer to this question?
The correct answer is: Root Guard is configured on a per-port basis and causes the port to become root-inconsistent if a superior BPDU is received. — Root Guard prevents a designated port from becoming a root port by placing it in a root-inconsistent state if superior BPDUs are received, which blocks traffic on that port. BPDU Guard places an access port in errdisable state if a BPDU is received, protecting against unauthorized switches. Option A is correct because Root Guard works on designated ports. Option D is correct because BPDU Guard is typically applied to PortFast-enabled access ports. Options B, C, and E are incorrect: BPDU Guard does not prevent loops on trunk ports (that's Loop Guard), Root Guard does not use errdisable (it uses root-inconsistent), and BPDU Guard does not filter BPDUs (it reacts to them).
What should I do if I get this 200-301 question wrong?
Review VLAN allowed lists, native VLAN mismatch detection, and how to verify VLAN membership with show vlan brief and show interfaces trunk. Then practise related 200-301 questions on switching, trunking, and access-port configuration.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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