CCNA Switching and Network Access Practice Question
This 200-301 practice question tests your understanding of switching and network access. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
Exhibit
MLS1# show running-config | include interface|spanning-tree|portfast|rootguard|loopguard|bpduguard
interface GigabitEthernet0/1
spanning-tree guard root
interface GigabitEthernet0/2
spanning-tree guard loop
interface GigabitEthernet0/3
spanning-tree portfast
spanning-tree bpduguard enable
! Current state:
MLS1# show spanning-tree interface gigabitEthernet 0/1 detail
Port 1 (GigabitEthernet0/1) of VLAN0001 is root inconsistent (Root Guard)
Designated bridge has priority 4096, address 0050.7966.6800
Configured guard type: root
Root guard active
MLS1# show spanning-tree interface gigabitEthernet 0/3 detail
Port 3 (GigabitEthernet0/3) of VLAN0001 is down (err-disabled)
BPDU guard enabled
BPDU received, moving to errdisable state
You are connected to a multilayer switch MLS1. Configure Root Guard on switchport GigabitEthernet 0/1 (connected to an unauthorized switch) so that if a superior BPDU is received, the port is blocked instead of causing a topology change. Also enable Loop Guard on uplink GigabitEthernet 0/2 (connected to the root bridge) to prevent unidirectional link issues. Finally, enable BPDU Guard on PortFast-enabled access port GigabitEthernet 0/3 (connected to a host) so that if a BPDU is received, the port goes err-disabled. After configuration, a superior BPDU is received on G0/1 and the port is blocked; a BPDU is received on G0/3 and the port goes err-disabled. Verify these protections are active.
MLS1# show running-config | include interface|spanning-tree|portfast|rootguard|loopguard|bpduguard
interface GigabitEthernet0/1
spanning-tree guard root
interface GigabitEthernet0/2
spanning-tree guard loop
interface GigabitEthernet0/3
spanning-tree portfast
spanning-tree bpduguard enable
! Current state:
MLS1# show spanning-tree interface gigabitEthernet 0/1 detail
Port 1 (GigabitEthernet0/1) of VLAN0001 is root inconsistent (Root Guard)
Designated bridge has priority 4096, address 0050.7966.6800
Configured guard type: root
Root guard active
MLS1# show spanning-tree interface gigabitEthernet 0/3 detail
Port 3 (GigabitEthernet0/3) of VLAN0001 is down (err-disabled)
BPDU guard enabled
BPDU received, moving to errdisable state
A
Root Guard on G0/1, Loop Guard on G0/2, BPDU Guard on G0/3
Root Guard on G0/1 blocks the port when a superior BPDU is received, placing it in root-inconsistent state. Loop Guard on G0/2 prevents an alternate port from becoming root if BPDUs stop due to unidirectional link. BPDU Guard on G0/3 err-disables the port upon receiving any BPDU, which is correct for a PortFast-enabled access port.
B
Root Guard on G0/1, UplinkFast on G0/2, BPDU Guard on G0/3
Why wrong: UplinkFast is a Cisco proprietary feature that speeds up convergence after a root port failure, but it does not prevent unidirectional link issues. Loop Guard is the correct feature for that purpose.
C
BPDU Guard on G0/1, Loop Guard on G0/2, Root Guard on G0/3
Why wrong: BPDU Guard on an uplink port (G0/1) would err-disable the port upon receiving a BPDU, which is not desired for a trunk port. Root Guard on an access port (G0/3) would not trigger err-disable; it would only block the port if a superior BPDU is received, but the requirement is to err-disable the port.
D
Root Guard on G0/1, Loop Guard on G0/2, PortFast on G0/3
Why wrong: PortFast alone does not provide protection; it only transitions the port to forwarding state quickly. BPDU Guard is required to err-disable the port if a BPDU is received on a PortFast-enabled port.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Root Guard on G0/1, Loop Guard on G0/2, BPDU Guard on G0/3
Root Guard was correctly configured on G0/1, so when a superior BPDU arrived, the port entered root-inconsistent state instead of becoming root port. Loop Guard on G0/2 prevents alternate port from becoming root if BPDUs stop. BPDU Guard on G0/3 correctly triggered err-disable upon receiving a BPDU on a PortFast port. To restore G0/3, use 'shutdown' then 'no shutdown' after removing the BPDU source. Verification commands confirm the protections are working.
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 on G0/1, Loop Guard on G0/2, BPDU Guard on G0/3
Why this is correct
Root Guard on G0/1 blocks the port when a superior BPDU is received, placing it in root-inconsistent state. Loop Guard on G0/2 prevents an alternate port from becoming root if BPDUs stop due to unidirectional link. BPDU Guard on G0/3 err-disables the port upon receiving any BPDU, which is correct for a PortFast-enabled access port.
Related concept
Access ports place end devices into a single VLAN.
✗
Root Guard on G0/1, UplinkFast on G0/2, BPDU Guard on G0/3
Why it's wrong here
UplinkFast is a Cisco proprietary feature that speeds up convergence after a root port failure, but it does not prevent unidirectional link issues. Loop Guard is the correct feature for that purpose.
✗
BPDU Guard on G0/1, Loop Guard on G0/2, Root Guard on G0/3
Why it's wrong here
BPDU Guard on an uplink port (G0/1) would err-disable the port upon receiving a BPDU, which is not desired for a trunk port. Root Guard on an access port (G0/3) would not trigger err-disable; it would only block the port if a superior BPDU is received, but the requirement is to err-disable the port.
✗
Root Guard on G0/1, Loop Guard on G0/2, PortFast on G0/3
Why it's wrong here
PortFast alone does not provide protection; it only transitions the port to forwarding state quickly. BPDU Guard is required to err-disable the port if a BPDU is received on a PortFast-enabled port.
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 on G0/1, Loop Guard on G0/2, BPDU Guard on G0/3Correct answer▾
Why this is correct
Root Guard on G0/1 blocks the port when a superior BPDU is received, placing it in root-inconsistent state. Loop Guard on G0/2 prevents an alternate port from becoming root if BPDUs stop due to unidirectional link. BPDU Guard on G0/3 err-disables the port upon receiving any BPDU, which is correct for a PortFast-enabled access port.
✗Root Guard on G0/1, UplinkFast on G0/2, BPDU Guard on G0/3Wrong answer — click to see why▾
Why this is wrong here
UplinkFast is not designed to detect or prevent unidirectional links; it only accelerates failover.
Why candidates choose this
Candidates may confuse UplinkFast with Loop Guard because both are STP enhancement features, but they serve different purposes.
✗BPDU Guard on G0/1, Loop Guard on G0/2, Root Guard on G0/3Wrong answer — click to see why▾
Why this is wrong here
The protections are applied to the wrong ports: BPDU Guard should be on access ports, Root Guard on ports facing potential rogue switches, and Loop Guard on uplinks.
Why candidates choose this
Candidates may know the features but misapply them to the wrong interfaces due to confusion about where each protection is appropriate.
✗Root Guard on G0/1, Loop Guard on G0/2, PortFast on G0/3Wrong answer — click to see why▾
Why this is wrong here
PortFast does not prevent BPDU reception; it only skips the listening and learning states. Without BPDU Guard, the port would still process BPDUs and could become a root port.
Why candidates choose this
Candidates may think PortFast is sufficient for access ports, but it must be paired with BPDU Guard to provide security against rogue switches.
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.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this 200-301 question in full detail.
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.
Switching and Network Access — This question tests Switching and Network Access — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: Root Guard on G0/1, Loop Guard on G0/2, BPDU Guard on G0/3 — Root Guard was correctly configured on G0/1, so when a superior BPDU arrived, the port entered root-inconsistent state instead of becoming root port. Loop Guard on G0/2 prevents alternate port from becoming root if BPDUs stop. BPDU Guard on G0/3 correctly triggered err-disable upon receiving a BPDU on a PortFast port. To restore G0/3, use 'shutdown' then 'no shutdown' after removing the BPDU source. Verification commands confirm the protections are working.
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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