The answer is that this switch is the root bridge for VLAN 10. This is confirmed because the output explicitly states “This bridge is the root,” and the Root ID and Bridge ID are identical—both share the same priority of 32778 and MAC address 0011.2233.4455. In Spanning Tree Protocol, a switch is the root bridge only when its own Bridge ID matches the Root ID, and all its interfaces will be in the Designated role with no Root Ports, as seen here with all three GigabitEthernet ports showing Desg FWD. On the ENCOR 350-401 exam, this question tests your ability to quickly interpret show spanning-tree output and distinguish between root and non-root switches. A common trap is assuming a switch with a low priority is automatically the root, but you must verify the “This bridge is the root” line and the ID match. Memory tip: “Same ID, root indeed—if Root ID and Bridge ID are twins, the switch wins.”
350-401 VLANs and Trunking Practice Question
This 350-401 practice question tests your understanding of vlans and trunking. 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.
A network engineer runs the following command on Switch SW1:
SW1# show spanning-tree vlan 10
VLAN0010
Spanning tree enabled protocol ieee
Root ID Priority 32778
Address 0011.2233.4455
This bridge is the root
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32778 (priority 32768 sys-id-ext 10)
Address 0011.2233.4455
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
The output explicitly states 'This bridge is the root'.
B
Gi0/2 is a root port.
Why wrong: Root ports appear on non-root bridges; here all ports are designated.
C
The spanning-tree mode is PVST+.
Why wrong: The output says 'protocol ieee' which is 802.1D (classic STP), not PVST+ (which would show 'protocol ieee' as well, but PVST+ is Cisco's implementation; however, the output does not distinguish. More importantly, the priority includes sys-id-ext, which is a PVST+ feature, but the protocol line does not say 'pvst'. The safest conclusion is that it's 802.1D with extended system ID. Option A is directly supported.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
This switch is the root bridge for VLAN 10.
The output explicitly states 'This bridge is the root' for VLAN 10, and the Root ID and Bridge ID are identical (same priority 32778 and address 0011.2233.4455), confirming SW1 is the root bridge for VLAN 10. All interfaces are in the Designated (Desg) role and Forwarding (FWD) state, which is expected for a root bridge because root bridges have no root ports.
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.
✓
This switch is the root bridge for VLAN 10.
Why this is correct
The output explicitly states 'This bridge is the root'.
Related concept
Read the scenario before looking for a memorised answer.
✗
Gi0/2 is a root port.
Why it's wrong here
Root ports appear on non-root bridges; here all ports are designated.
✗
The spanning-tree mode is PVST+.
Why it's wrong here
The output says 'protocol ieee' which is 802.1D (classic STP), not PVST+ (which would show 'protocol ieee' as well, but PVST+ is Cisco's implementation; however, the output does not distinguish. More importantly, the priority includes sys-id-ext, which is a PVST+ feature, but the protocol line does not say 'pvst'. The safest conclusion is that it's 802.1D with extended system ID. Option A is directly supported.
✗
VLAN 10 has a forwarding delay of 30 seconds.
Why it's wrong here
Forward delay is 15 seconds.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that a switch with all Designated ports must be the root bridge, but the trap here is that candidates may overlook the explicit 'This bridge is the root' statement and instead focus on port roles, or they may confuse the 'protocol ieee' output with PVST+ when it actually indicates standard 802.1D STP.
Trap categories for this question
Command / output trap
The output says 'protocol ieee' which is 802.1D (classic STP), not PVST+ (which would show 'protocol ieee' as well, but PVST+ is Cisco's implementation; however, the output does not distinguish. More importantly, the priority includes sys-id-ext, which is a PVST+ feature, but the protocol line does not say 'pvst'. The safest conclusion is that it's 802.1D with extended system ID. Option A is directly supported.
Detailed technical explanation
How to think about this question
In STP, the root bridge is elected based on the lowest bridge ID (priority + system ID extension for VLAN). Here, the priority is 32778 (32768 base priority + 10 for VLAN 10), and the root bridge has all ports as Designated ports because it is the reference point for the spanning tree. The 'Aging Time 300 sec' refers to the MAC address table aging timer, not STP timers, which is a common point of confusion.
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 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 350-401 question in full detail.
VLANs and Trunking — This question tests VLANs and Trunking — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: This switch is the root bridge for VLAN 10. — The output explicitly states 'This bridge is the root' for VLAN 10, and the Root ID and Bridge ID are identical (same priority 32778 and address 0011.2233.4455), confirming SW1 is the root bridge for VLAN 10. All interfaces are in the Designated (Desg) role and Forwarding (FWD) state, which is expected for a root bridge because root bridges have no root ports.
What should I do if I get this 350-401 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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