The correct conclusion is that the root bridge for VLAN 10 has MAC address aabb.cc00.0100. This is determined by interpreting the `show spanning-tree vlan 10` output, where the Root ID section explicitly lists the root bridge’s MAC address and priority (32778, which is the default 32768 plus the VLAN 10 sys-id-ext). The local switch (aabb.cc00.0200) has a root port (Gi0/1) with a cost of 19, proving it is not the root; the root is the device with the lower MAC address when priorities are equal. On the ENCOR 350-401 exam, this command tests your ability to read STP output and identify root bridge election, a common trap being that students confuse the local Bridge ID with the Root ID. Remember the memory tip: “Root ID is who you follow, Bridge ID is who you are”—if the local switch has a root port, it is not the root.
350-401 SNMP and Syslog Practice Question
This 350-401 practice question tests your understanding of snmp and syslog. 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 SW2:
SW2# show spanning-tree vlan 10
VLAN0010
Spanning tree enabled protocol ieee
Root ID Priority 32778
Address aabb.cc00.0100
Cost 19
Port 1 (GigabitEthernet0/1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Bridge ID Priority 32778 (priority 32768 sys-id-ext 10)
Address aabb.cc00.0200
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec
Aging Time 300 sec
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The root bridge for VLAN 10 has MAC address aabb.cc00.0100.
The output shows STP details for VLAN 10. The Root ID is aabb.cc00.0100 (priority 32778 = 32768 + 10 for VLAN 10). The local switch (aabb.cc00.0200) has the same priority. The root port is Gi0/1 (cost 19 to root). Gi0/2 is an alternate port (blocking). Gi0/3 is a designated port (forwarding). The key conclusion is that the local switch is not the root because it has a root port. Also, the root bridge has the same priority, so the root is determined by lower MAC address (aabb.cc00.0100 < aabb.cc00.0200).
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.
✗
SW2 is the root bridge for VLAN 10.
Why it's wrong here
SW2 has a root port (Gi0/1), so it is not the root bridge. The root bridge has a lower MAC address (aabb.cc00.0100).
✓
The root bridge for VLAN 10 has MAC address aabb.cc00.0100.
Why this is correct
The Root ID shows the root bridge's MAC address as aabb.cc00.0100.
Related concept
Access ports place end devices into a single VLAN.
✗
Port Gi0/2 is in forwarding state.
Why it's wrong here
Gi0/2 is shown as 'Altn BLK', meaning alternate (blocking) state.
✗
The STP priority for VLAN 10 is 32768.
Why it's wrong here
The priority shown is 32778, which is 32768 + 10 (VLAN ID). The base priority is 32768, but the effective priority includes the VLAN ID.
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
Gi0/2 is shown as 'Altn BLK', meaning alternate (blocking) state.
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 350-401 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 350-401 questions on switching, trunking, and access-port configuration.
SNMP and Syslog — This question tests SNMP and Syslog — Access ports place end devices into a single VLAN..
What is the correct answer to this question?
The correct answer is: The root bridge for VLAN 10 has MAC address aabb.cc00.0100. — The output shows STP details for VLAN 10. The Root ID is aabb.cc00.0100 (priority 32778 = 32768 + 10 for VLAN 10). The local switch (aabb.cc00.0200) has the same priority. The root port is Gi0/1 (cost 19 to root). Gi0/2 is an alternate port (blocking). Gi0/3 is a designated port (forwarding). The key conclusion is that the local switch is not the root because it has a root port. Also, the root bridge has the same priority, so the root is determined by lower MAC address (aabb.cc00.0100 < aabb.cc00.0200).
What should I do if I get this 350-401 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 350-401 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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