The answer is to configure MLS1 as the root bridge by entering the global configuration commands `spanning-tree vlan 10 root primary` and `spanning-tree vlan 20 root primary`. This works because the `root primary` macro automatically sets the switch’s bridge priority to 24576 for the specified VLANs, which is lower than the default priority of 32768, ensuring MLS1 wins the spanning-tree election for both VLAN 10 and VLAN 20. On the CCNA 200-301 v2 exam, this question tests your understanding of the `root primary` command as a shortcut versus manually setting priority, and it often appears alongside PortFast and BPDU Guard configurations to verify that a port does not enter an err-disabled state due to unexpected BPDUs. A common trap is forgetting that `root primary` only affects the specified VLANs—you must run it separately for each VLAN. Verify success with `show spanning-tree vlan 10` to confirm the priority is 24576 and `show interfaces gigabitEthernet0/1 status` to ensure the port is up, not err-disabled. Memory tip: think “primary = priority 24,576” (the first two digits of the priority are 24, matching the 24 in 24576).
CCNA Switching and Network Access Practice Question
This 200-301 practice question tests your understanding of switching and network access. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
Network Topology
You are connected to a multilayer switch MLS1. The network has two other switches: SW2 and SW3. The interface GigabitEthernet0/1 already has PortFast and BPDU Guard enabled. Configure MLS1 as the root bridge for VLAN 10 and VLAN 20 using the root primary command. After configuration, verify that the interface is not in err-disabled state and that the root bridge role is correctly assigned.
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
MLS1# show running-config | include hostname|spanning-tree|interface GigabitEthernet0/1
hostname MLS1
!
spanning-tree mode rapid-pvst
!
interface GigabitEthernet0/1
switchport mode access
switchport access vlan 10
spanning-tree portfast
spanning-tree bpduguard enable
!
MLS1# show spanning-tree vlan 10
VLAN0010
Spanning tree enabled protocol rstp
Root ID Priority 32769
Address aabb.cc00.0100
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Address aabb.cc00.0100
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Interface Role Sts Cost Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi0/1 Desg FWD 4 128.1 P2p Edge
MLS1# show interfaces gigabitEthernet 0/1 status
Port Name Status Vlan Duplex Speed Type
Gi0/1 connected 10 a-full a-100 10/100/1000BaseTX
A
Configure 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary' on MLS1. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.
Correct: This completes the required root bridge configuration and uses proper verification commands.
B
Configure 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root secondary' on MLS1. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.
Why wrong: This is incorrect because 'root secondary' sets the priority to 28672, which would make MLS1 the backup root, not the primary root. The question requires MLS1 to be the root bridge for both VLANs.
C
Configure 'spanning-tree vlan 10 priority 4096' and 'spanning-tree vlan 20 priority 4096' on MLS1. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.
Why wrong: This is incorrect because setting the priority to 4096 is not the standard method; the 'root primary' command automatically sets the priority to 24576 (or lower if needed). A priority of 4096 is lower than 24576 and would also make the switch root, but the question specifically asks to use the 'root primary' command.
D
Configure 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary' on MLS1. Then configure 'spanning-tree portfast default' and 'spanning-tree bpduguard default' globally. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.
Why wrong: This is incorrect because the question states that PortFast and BPDU Guard are already enabled on G0/1. Configuring them globally would apply to all access ports, which is unnecessary and could cause issues on trunk ports. The existing configuration on the interface is sufficient.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Configure 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary' on MLS1. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.
The interface Gi0/1 already has PortFast and BPDU Guard configured, so no additional configuration is needed for that step. Using 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary' sets the priority to 24576, ensuring MLS1 becomes root for both VLANs. Verify with 'show spanning-tree vlan 10' to see the priority changed and 'show interfaces gigabitEthernet0/1 status' to confirm the port is not err-disabled.
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.
✓
Configure 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary' on MLS1. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.
Why this is correct
Correct: This completes the required root bridge configuration and uses proper verification commands.
Clue confirmation
The clue word "primary" in the question point toward this answer.
Related concept
Access ports place end devices into a single VLAN.
✗
Configure 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root secondary' on MLS1. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.
Why it's wrong here
This is incorrect because 'root secondary' sets the priority to 28672, which would make MLS1 the backup root, not the primary root. The question requires MLS1 to be the root bridge for both VLANs.
✗
Configure 'spanning-tree vlan 10 priority 4096' and 'spanning-tree vlan 20 priority 4096' on MLS1. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.
Why it's wrong here
This is incorrect because setting the priority to 4096 is not the standard method; the 'root primary' command automatically sets the priority to 24576 (or lower if needed). A priority of 4096 is lower than 24576 and would also make the switch root, but the question specifically asks to use the 'root primary' command.
✗
Configure 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary' on MLS1. Then configure 'spanning-tree portfast default' and 'spanning-tree bpduguard default' globally. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.
Why it's wrong here
This is incorrect because the question states that PortFast and BPDU Guard are already enabled on G0/1. Configuring them globally would apply to all access ports, which is unnecessary and could cause issues on trunk ports. The existing configuration on the interface is sufficient.
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.
✓Configure 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary' on MLS1. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.Correct answer▾
Why this is correct
Correct: This completes the required root bridge configuration and uses proper verification commands.
✗Configure 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root secondary' on MLS1. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.Wrong answer — click to see why▾
Why this is wrong here
Using root secondary for VLAN 20 would not make MLS1 root for that VLAN; it would set a higher priority, leaving another switch as root.
Why candidates choose this
Candidates may confuse 'root primary' and 'root secondary', thinking both are needed for redundancy, but the requirement is for MLS1 to be the root, not a backup.
✗Configure 'spanning-tree vlan 10 priority 4096' and 'spanning-tree vlan 20 priority 4096' on MLS1. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.Wrong answer — click to see why▾
Why this is wrong here
While a priority of 4096 would make MLS1 root, the 'root primary' command is the recommended method and automatically sets the appropriate value (24576).
Why candidates choose this
Candidates might think manually setting a low priority is equivalent to 'root primary', but the command is a best practice and ensures proper operation with other switches.
✗Configure 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary' on MLS1. Then configure 'spanning-tree portfast default' and 'spanning-tree bpduguard default' globally. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'.Wrong answer — click to see why▾
Why this is wrong here
PortFast and BPDU Guard are already enabled on the interface; adding global defaults is unnecessary and does not complete the specific interface task, though it would not harm the root bridge goal.
Why candidates choose this
Candidates might think global configuration is a best practice, but the question specifies the interface already has these features enabled, so additional configuration is unnecessary and could be counterproductive.
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.
Trap categories for this question
Command / output trap
This is incorrect because setting the priority to 4096 is not the standard method; the 'root primary' command automatically sets the priority to 24576 (or lower if needed). A priority of 4096 is lower than 24576 and would also make the switch root, but the question specifically asks to use the 'root primary' command.
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: Configure 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary' on MLS1. Verify with 'show spanning-tree vlan 10' and 'show interfaces gigabitEthernet0/1 status'. — The interface Gi0/1 already has PortFast and BPDU Guard configured, so no additional configuration is needed for that step. Using 'spanning-tree vlan 10 root primary' and 'spanning-tree vlan 20 root primary' sets the priority to 24576, ensuring MLS1 becomes root for both VLANs. Verify with 'show spanning-tree vlan 10' to see the priority changed and 'show interfaces gigabitEthernet0/1 status' to confirm the port is not err-disabled.
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.
Are there clue words in this question I should notice?
Yes — watch for: "primary". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
What is the key concept behind this question?
Access ports place end devices into a single VLAN.
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