The correct configuration applies Root Guard on Gi0/2, Loop Guard on Gi0/1, and BPDU Guard on Gi0/0 because each protection mechanism targets a specific STP threat. Root Guard on the designated port prevents an unauthorized switch from becoming root by blocking any port that receives a superior BPDU, transitioning it to a root-inconsistent state. Loop Guard protects against unidirectional link failures by placing the uplink port into a loop-inconsistent state if BPDUs stop arriving, while BPDU Guard on a PortFast-enabled access port immediately err-disables the port upon receiving any BPDU, enforcing the access-edge boundary. On the CCNA 200-301 v2 exam, this tests your ability to match each guard to its correct interface role—designated, root, or access—and to recall that Root Guard and Loop Guard are mutually exclusive on the same port. A common trap is confusing Root Guard with BPDU Guard: remember that Root Guard blocks the port but keeps it administratively up, whereas BPDU Guard shuts it down. Memory tip: “Root blocks the root, Loop blocks the loop, BPDU kills the port.”
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 spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address aabb.cc00.0100
This bridge is the root
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address aabb.cc00.0100
Interface Role Sts Cost Prio.Nbr Type
------------------- --- --- --------- -------- --------------------------------
Gi0/0 Desg FWD 4 128.1 P2p
Gi0/1 Desg FWD 4 128.2 P2p
Gi0/2 Desg FWD 4 128.3 P2p
Gi0/2 is connected to SW2. Gi0/1 is uplink to core. Gi0/0 is access port with PortFast enabled.
MLS1# show running-config | section interface
interface GigabitEthernet0/0
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet0/1
switchport mode trunk
!
interface GigabitEthernet0/2
switchport mode trunk
!
You are connected to a multilayer switch MLS1. Configure Root Guard on the designated port facing another switch SW2 to prevent it from becoming root, configure Loop Guard on the uplink port to the core, and configure BPDU Guard on a PortFast-enabled access port. After configuration, a superior BPDU arrives on the designated port—confirm it is blocked by Root Guard. Then, simulate a BPDU on the access port to verify it goes err-disabled due to BPDU Guard.
MLS1# show spanning-tree
VLAN0001
Spanning tree enabled protocol ieee
Root ID Priority 32769
Address aabb.cc00.0100
This bridge is the root
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address aabb.cc00.0100
Interface Role Sts Cost Prio.Nbr Type
------------------- --- --- --------- -------- --------------------------------
Gi0/0 Desg FWD 4 128.1 P2p
Gi0/1 Desg FWD 4 128.2 P2p
Gi0/2 Desg FWD 4 128.3 P2p
Gi0/2 is connected to SW2. Gi0/1 is uplink to core. Gi0/0 is access port with PortFast enabled.
MLS1# show running-config | section interface
interface GigabitEthernet0/0
switchport mode access
spanning-tree portfast
!
interface GigabitEthernet0/1
switchport mode trunk
!
interface GigabitEthernet0/2
switchport mode trunk
!
A
Root Guard on Gi0/2, Loop Guard on Gi0/1, BPDU Guard on Gi0/0
This configuration correctly applies Root Guard on the designated port (Gi0/2) to block superior BPDUs, Loop Guard on the uplink (Gi0/1) to prevent loops from unidirectional links, and BPDU Guard on the PortFast-enabled access port (Gi0/0) to err-disable upon BPDU reception.
B
Root Guard on Gi0/1, Loop Guard on Gi0/2, BPDU Guard on Gi0/0
Why wrong: This is incorrect because Root Guard should be applied on the designated port facing SW2 (Gi0/2), not on the uplink to the core (Gi0/1). Loop Guard should be on the uplink, not on the designated port.
C
Root Guard on Gi0/0, Loop Guard on Gi0/1, BPDU Guard on Gi0/2
Why wrong: This is incorrect because Root Guard should not be on an access port (Gi0/0) as it is PortFast-enabled and not expected to receive BPDUs; BPDU Guard is more appropriate there. BPDU Guard on Gi0/2 would err-disable the designated port upon receiving a superior BPDU, which is not the intended behavior.
D
Root Guard on Gi0/2, Loop Guard on Gi0/0, BPDU Guard on Gi0/1
Why wrong: This is incorrect because Loop Guard should be on the uplink (Gi0/1), not on the access port (Gi0/0). BPDU Guard should be on the access port, not on the uplink.
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 Gi0/2, Loop Guard on Gi0/1, BPDU Guard on Gi0/0
First, Root Guard was applied on Gi0/2 (the designated port) with 'spanning-tree guard root' to prevent SW2 from becoming root. Second, Loop Guard was applied on the uplink Gi0/1 with 'spanning-tree guard loop' to protect against unidirectional links. Third, BPDU Guard was applied on the PortFast-enabled access port Gi0/0 with 'spanning-tree bpduguard enable'. When a superior BPDU arrives on Gi0/2, Root Guard transitions it to a root-inconsistent (blocked) state. If a BPDU is received on Gi0/0, BPDU Guard err-disables the port. Verification shows the blocked state on Gi0/2 and err-disabled on Gi0/0.
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 Gi0/2, Loop Guard on Gi0/1, BPDU Guard on Gi0/0
Why this is correct
This configuration correctly applies Root Guard on the designated port (Gi0/2) to block superior BPDUs, Loop Guard on the uplink (Gi0/1) to prevent loops from unidirectional links, and BPDU Guard on the PortFast-enabled access port (Gi0/0) to err-disable upon BPDU reception.
Related concept
Access ports place end devices into a single VLAN.
✗
Root Guard on Gi0/1, Loop Guard on Gi0/2, BPDU Guard on Gi0/0
Why it's wrong here
This is incorrect because Root Guard should be applied on the designated port facing SW2 (Gi0/2), not on the uplink to the core (Gi0/1). Loop Guard should be on the uplink, not on the designated port.
✗
Root Guard on Gi0/0, Loop Guard on Gi0/1, BPDU Guard on Gi0/2
Why it's wrong here
This is incorrect because Root Guard should not be on an access port (Gi0/0) as it is PortFast-enabled and not expected to receive BPDUs; BPDU Guard is more appropriate there. BPDU Guard on Gi0/2 would err-disable the designated port upon receiving a superior BPDU, which is not the intended behavior.
✗
Root Guard on Gi0/2, Loop Guard on Gi0/0, BPDU Guard on Gi0/1
Why it's wrong here
This is incorrect because Loop Guard should be on the uplink (Gi0/1), not on the access port (Gi0/0). BPDU Guard should be on the access port, not on the uplink.
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 Gi0/2, Loop Guard on Gi0/1, BPDU Guard on Gi0/0Correct answer▾
Why this is correct
This configuration correctly applies Root Guard on the designated port (Gi0/2) to block superior BPDUs, Loop Guard on the uplink (Gi0/1) to prevent loops from unidirectional links, and BPDU Guard on the PortFast-enabled access port (Gi0/0) to err-disable upon BPDU reception.
✗Root Guard on Gi0/1, Loop Guard on Gi0/2, BPDU Guard on Gi0/0Wrong answer — click to see why▾
Why this is wrong here
Root Guard is intended for ports that should not become root; applying it on the uplink would block legitimate superior BPDUs from the core. Loop Guard on the designated port would not protect against unidirectional links on the uplink.
Why candidates choose this
Candidates may confuse which port is designated versus uplink, or think Root Guard should be on all ports.
✗Root Guard on Gi0/0, Loop Guard on Gi0/1, BPDU Guard on Gi0/2Wrong answer — click to see why▾
Why this is wrong here
Root Guard on an access port is unnecessary and would not prevent the switch from becoming root via other ports. BPDU Guard on the designated port would disable it instead of blocking the BPDU.
Why candidates choose this
Candidates might think Root Guard is a general protection and apply it to all ports, or confuse the functions of Root Guard and BPDU Guard.
✗Root Guard on Gi0/2, Loop Guard on Gi0/0, BPDU Guard on Gi0/1Wrong answer — click to see why▾
Why this is wrong here
Loop Guard on an access port does not protect against unidirectional links on the uplink. BPDU Guard on the uplink would err-disable the core connection if a BPDU is received, which is undesirable.
Why candidates choose this
Candidates may misplace Loop Guard and BPDU Guard due to misunderstanding of where unidirectional links or BPDU threats occur.
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 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.
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 Gi0/2, Loop Guard on Gi0/1, BPDU Guard on Gi0/0 — First, Root Guard was applied on Gi0/2 (the designated port) with 'spanning-tree guard root' to prevent SW2 from becoming root. Second, Loop Guard was applied on the uplink Gi0/1 with 'spanning-tree guard loop' to protect against unidirectional links. Third, BPDU Guard was applied on the PortFast-enabled access port Gi0/0 with 'spanning-tree bpduguard enable'. When a superior BPDU arrives on Gi0/2, Root Guard transitions it to a root-inconsistent (blocked) state. If a BPDU is received on Gi0/0, BPDU Guard err-disables the port. Verification shows the blocked state on Gi0/2 and err-disabled on Gi0/0.
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.
About these practice questions
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These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. You are connected to the multilayer switch SW1. Configure Root Guard on the designated port towards the access switch SW2, Loop Guard on the uplink port towards the distribution switch SW3, and BPDU Guard on the PortFast-enabled port connected to a workstation. After configuration, a superior BPDU is received on the designated port, causing it to be blocked by Root Guard. Later, a BPDU is received on the PortFast port, triggering err-disable state. Identify and resolve these issues.
hard
✓ A.Remove Root Guard from interface Gi0/0 and re-enable interface Gi0/2 with a shutdown/no shutdown sequence.
B.Disable BPDU Guard on interface Gi0/2 and increase the root bridge priority on SW1 to prevent superior BPDUs.
C.Apply Root Guard to interface Gi0/2 instead of Gi0/0 and configure Loop Guard on Gi0/0.
D.Remove Loop Guard from interface Gi0/1 and configure it on Gi0/0 instead, then re-enable Gi0/2 using the 'errdisable recovery cause bpduguard' command.
Why A: The issue is that Root Guard was incorrectly applied to the designated port (Gi0/0) which should normally be the root port if a superior BPDU is received. Root Guard blocks the port when a superior BPDU arrives, but this is expected on a designated port; instead, Root Guard should be applied to ports that should never become root ports. In this scenario, the superior BPDU is legitimate (from a root bridge with lower priority), so Root Guard should be removed from Gi0/0. For the PortFast port (Gi0/2), BPDU Guard correctly err-disabled the port upon receiving a BPDU, indicating an unauthorized switch connection. To restore the port, you must shut/no shut the interface and then investigate why a BPDU was received. The solution involves removing Root Guard from Gi0/0 and re-enabling Gi0/2 after verifying the connecting device.
Variation 2. 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.
hard
✓ A.Root Guard on G0/1, Loop Guard on G0/2, BPDU Guard on G0/3
B.Root Guard on G0/1, UplinkFast on G0/2, BPDU Guard on G0/3
C.BPDU Guard on G0/1, Loop Guard on G0/2, Root Guard on G0/3
D.Root Guard on G0/1, Loop Guard on G0/2, PortFast on G0/3
Why A: 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.
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