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This page has 15 Spanning Tree Protocol Scenarios scenario questions for the 350-401 exam, each with detailed explanations and wrong-answer analysis.

How should I approach 350-401 scenario questions?

Read the full scenario before looking at the answer options. Identify the constraint or requirement in the scenario, then eliminate options that are generally true but wrong for this specific case. Scenario questions reward careful reading over pattern matching.

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Scenario-based practice

Spanning Tree Protocol Scenarios

Practise 350-401 STP questions covering root bridge election, bridge IDs, port roles (root, designated, blocking), path cost, PortFast, BPDU Guard, and how spanning tree prevents Layer 2 loops.

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scenario questions

350-401

exam code

Cisco

vendor

Scenario guide

How to approach spanning tree protocol scenarios

STP and Rapid PVST+ questions test your understanding of root bridge election, port roles, port states, and protection features. These appear in MCQ, multi-select, and drag-and-drop formats on the CCNA because STP behaviour is non-intuitive and frequently misunderstood.

Quick answer

STP questions usually test root bridge election, port roles, path cost and how spanning tree prevents Layer 2 loops.

Root bridge election and bridge ID comparison.

Root ports, designated ports and blocked/alternate ports.

Path cost and how switches choose the best path to the root bridge.

PortFast, BPDU Guard and common Layer 2 loop-prevention behaviour.

Practice scenarios

Question 1mediumdrag order

Open the full STP breakdown →

Drag and drop the steps for the Spanning Tree Protocol (STP) convergence process in the correct order.

Drag steps to the numbered slots on the right, or tap a step then tap a slot.

Steps

Order

1Step 1

2Step 2

3Step 3

4Step 4

5Step 5

Question 2easymulti select

Full question →

Which TWO characteristics are true about the operation of Rapid PVST+? (Choose two.)

A
It runs a single spanning-tree instance for all VLANs.
Why wrong: Incorrect: That's MST; Rapid PVST+ runs per VLAN.
B
It eliminates the need for BPDUs.
Why wrong: Incorrect: BPDUs are still used for topology discovery.
C
It supports PortFast to enable immediate transition to forwarding.
Correct: PortFast allows edge ports to skip listening/learning.
D
It uses a separate root bridge per VLAN.
Why wrong: Incorrect: That's PVST+; Rapid PVST+ uses a single root per VLAN but not separate.
E
It provides faster convergence than PVST+.
Correct: Rapid PVST+ reduces convergence time via RSTP enhancements.

Full breakdown with real-world context →

Question 3easymultiple choice

Open the full VLAN trunking answer →

A network administrator is troubleshooting a performance issue in a large enterprise campus network. The network consists of Cisco Catalyst 9300 switches acting as access switches and Cisco Catalyst 9500 switches as distribution. Users on VLAN 10 report intermittent slow file transfers to a server on VLAN 20. The administrator has verified that there are no errors on the links, CPU utilization is normal, and STP topology is stable. The administrator suspects a possible QoS issue. Upon checking the QoS configuration on the access switch, the administrator finds that the default QoS configuration is in place, which trusts the CoS value at the port level. The connected devices are IP phones and PCs; the IP phones mark voice traffic with CoS 5. The server on VLAN 20 is connected to a distribution switch. Which action should the administrator take to most likely resolve the issue?

A
Apply a policy map that polices voice traffic to 128 kbps to free bandwidth for data.
Why wrong: Incorrect; policing voice may cause call quality degradation.
B
Disable QoS entirely on all switches to eliminate any potential QoS-related drops.
Why wrong: Incorrect; disabling QoS may cause voice quality issues.
C
Configure auto QoS for VoIP on the access ports to ensure proper classification and queuing.
Correct.
D
Configure trust DSCP on the access ports to prioritize all traffic based on DSCP values.
Why wrong: Incorrect; endpoints may not set DSCP appropriately.

Full breakdown with real-world context →

Question 4mediummulti select

Open the full STP breakdown →

Which TWO STP features are used to improve convergence time after a topology change?

A
UplinkFast
UplinkFast accelerates convergence after a direct link failure.
B
BackboneFast
BackboneFast reduces convergence time after an indirect link failure.
C
Root Guard
Why wrong: Root Guard prevents a switch from becoming root, but does not improve convergence.
D
BPDU Guard
Why wrong: BPDU Guard is a security feature to prevent rogue switches.
E
PortFast
Why wrong: PortFast is for immediate transition to forwarding on access ports, not for convergence after topology change.

Full breakdown with real-world context →

Question 5mediummultiple choice

Open the full VLAN trunking answer →

Examine the following configuration snippet:

interface GigabitEthernet1/0/1
 switchport mode access
 switchport access vlan 100
 spanning-tree portfast
 spanning-tree bpduguard enable

What is the effect of this configuration?

A
The port will immediately transition to forwarding state and will be error-disabled if a BPDU is received.
PortFast skips listening/learning; BPDU Guard error-disables the port on BPDU reception.
B
The port will remain in blocking state until a BPDU is received from the root bridge.
Why wrong: PortFast overrides the normal STP state machine; the port goes directly to forwarding.
C
The port will only forward BPDUs and will not forward data traffic.
Why wrong: PortFast allows data traffic; BPDU Guard disables the port on BPDU reception, not just forward them.
D
The port will participate in RSTP and will not be affected by BPDU reception.
Why wrong: BPDU Guard is active and will error-disable the port upon BPDU reception, regardless of STP variant.

Full breakdown with real-world context →

Question 6hardmultiple choice

Open the full VLAN trunking answer →

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

Interface        Role Sts Cost      Prio.Nbr Type

---------------- ---- --- --------- -------- -------------------------------- Gi0/1 Desg FWD 4 128.1 P2p Gi0/2 Desg FWD 4 128.2 P2p Gi0/3 Desg FWD 4 128.3 P2p

Based on this output, what can be concluded?

A
This switch is the root bridge for VLAN 10.
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.
D
VLAN 10 has a forwarding delay of 30 seconds.
Why wrong: Forward delay is 15 seconds.

Full breakdown with real-world context →

Question 7mediummultiple choice

Open the full VLAN trunking answer →

A network engineer runs the following command on Switch SW2:

SW2# show spanning-tree vlan 20

VLAN0020 Spanning tree enabled protocol ieee Root ID Priority 24596 Address aabb.cc00.0200 Cost 4 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 20) Address aabb.cc00.0300 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 Root FWD 4 128.1 P2p Gi0/2 Desg FWD 4 128.2 P2p Gi0/3 Altn BLK 4 128.3 P2p

Based on this output, what can be concluded?

A
SW2 is the root bridge for VLAN 20.
Why wrong: Incorrect. The root ID shows a different bridge (aabb.cc00.0200) with lower priority.
B
GigabitEthernet0/3 is in the Blocking state to prevent a loop.
Correct. Gi0/3 is shown as Altn BLK (Alternate, Blocking), which prevents a loop.
C
The root port cost is 8.
Why wrong: Incorrect. The root cost is 4, as shown in the Root ID section.
D
SW2's bridge priority is 32768.
Why wrong: Incorrect. The bridge priority is 32778 (32768 + 20 for VLAN 20).

Full breakdown with real-world context →

Question 8easymultiple choice

Open the full VLAN trunking answer →

A network engineer runs the following command on Switch SW5:

SW5# show spanning-tree vlan 50

VLAN0050 Spanning tree enabled protocol ieee Root ID Priority 24626 Address aabb.cc00.0800 Cost 4 Port 1 (GigabitEthernet0/1) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32768 (priority 32768 sys-id-ext 50) Address aabb.cc00.0900 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 Root FWD 4 128.1 P2p Gi0/2 Desg FWD 4 128.2 P2p Gi0/3 Desg FWD 4 128.3 P2p Gi0/4 Altn BLK 4 128.4 P2p

Based on this output, how many ports are in the Forwarding state?

A
1
Why wrong: Incorrect. There are three forwarding ports.
B
2
Why wrong: Incorrect. There are three forwarding ports.
C
3
Correct. Gi0/1, Gi0/2, and Gi0/3 are all in FWD state.
D
4
Why wrong: Incorrect. Gi0/4 is in BLK state.

Full breakdown with real-world context →

Question 9hardmultiple choice

Open the full VLAN trunking answer →

A network engineer runs the following command on Switch SW3:

SW3# show spanning-tree vlan 30

VLAN0030 Spanning tree enabled protocol ieee Root ID Priority 24606 Address aabb.cc00.0400 Cost 12 Port 2 (GigabitEthernet0/2) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32798 (priority 32768 sys-id-ext 30) Address aabb.cc00.0500 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 Gi0/2 Root FWD 12 128.2 P2p Gi0/3 Desg FWD 4 128.3 P2p

Based on this output, what is the root path cost from SW3 to the root bridge for VLAN 30?

A
4
Why wrong: Incorrect. 4 is the cost of Gi0/1 and Gi0/3, not the root path cost.
B
12
Correct. The root path cost is 12, as shown in the Root ID section.
C
16
Why wrong: Incorrect. There is no indication of 16.
D
20
Why wrong: Incorrect. 20 is the Max Age, not a cost.

Full breakdown with real-world context →

Question 10mediummultiple choice

Open the full VLAN trunking answer →

A network engineer runs the following command on Switch SW6:

SW6# show spanning-tree vlan 60

VLAN0060 Spanning tree enabled protocol ieee Root ID Priority 24636 Address aabb.cc00.0a00 Cost 8 Port 1 (GigabitEthernet0/1) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32768 (priority 32768 sys-id-ext 60) Address aabb.cc00.0b00 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 Root FWD 8 128.1 P2p Gi0/2 Desg FWD 4 128.2 P2p Gi0/3 Altn BLK 4 128.3 P2p Gi0/4 Desg FWD 4 128.4 P2p

Based on this output, what is the bridge priority of the root bridge for VLAN 60?

A
24576
Why wrong: Incorrect. 24576 is the base priority, but the root ID priority shown is 24636.
B
24636
Correct. The Root ID priority is 24636.
C
32768
Why wrong: Incorrect. 32768 is the base priority of SW6, not the root bridge.
D
32828
Why wrong: Incorrect. There is no such value in the output.

Full breakdown with real-world context →

Question 11easymultiple choice

Open the full VLAN trunking answer →

A network engineer runs the following command on Switch SW4:

SW4# show spanning-tree vlan 40

VLAN0040 Spanning tree enabled protocol ieee Root ID Priority 24616 Address aabb.cc00.0600 Cost 8 Port 1 (GigabitEthernet0/1) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32768 (priority 32768 sys-id-ext 40) Address aabb.cc00.0700 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 Root FWD 8 128.1 P2p Gi0/2 Desg FWD 4 128.2 P2p Gi0/3 Desg FWD 4 128.3 P2p

Based on this output, which port is the root port?

A
GigabitEthernet0/1
Correct. Gi0/1 is shown with role 'Root'.
B
GigabitEthernet0/2
Why wrong: Incorrect. Gi0/2 is a designated port (Desg).
C
GigabitEthernet0/3
Why wrong: Incorrect. Gi0/3 is a designated port (Desg).
D
There is no root port because SW4 is the root bridge.
Why wrong: Incorrect. SW4 is not the root bridge; the root bridge has a different MAC address.

Full breakdown with real-world context →

Question 12easymultiple choice

Open the full VLAN trunking answer →

A network engineer runs the following command on Switch SW7:

SW7# show spanning-tree vlan 70

VLAN0070 Spanning tree enabled protocol ieee Root ID Priority 24646 Address aabb.cc00.0c00 Cost 4 Port 1 (GigabitEthernet0/1) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32768 (priority 32768 sys-id-ext 70) Address aabb.cc00.0d00 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 Root FWD 4 128.1 P2p Gi0/2 Desg FWD 4 128.2 P2p Gi0/3 Altn BLK 4 128.3 P2p

Based on this output, which port is the alternate port?

A
GigabitEthernet0/1
Why wrong: Incorrect. Gi0/1 is the root port.
B
GigabitEthernet0/2
Why wrong: Incorrect. Gi0/2 is a designated port.
C
GigabitEthernet0/3
Correct. Gi0/3 is the alternate port (Altn BLK).
D
There is no alternate port.
Why wrong: Incorrect. Gi0/3 is an alternate port.

Full breakdown with real-world context →

Question 13mediummultiple choice

Full question →

interface GigabitEthernet0/1
 spanning-tree portfast
 spanning-tree bpduguard enable

end

What is the effect of this configuration?

A
The port will immediately transition to forwarding state and will be error-disabled if a BPDU is received.
PortFast causes immediate forwarding; BPDU Guard error-disables the port upon BPDU reception.
B
The port will go through normal STP states and will be error-disabled if a BPDU is received.
Why wrong: PortFast skips listening/learning; BPDU Guard still triggers error-disable.
C
The port will immediately transition to forwarding and ignore any BPDUs received.
Why wrong: BPDU Guard does not ignore BPDUs; it error-disables the port.
D
The port will remain in blocking state until a BPDU is received.
Why wrong: PortFast forces immediate forwarding; blocking is not used.

Full breakdown with real-world context →

Question 14easymultiple choice

Open the full STP breakdown →

What is the default STP hello timer value in seconds?

A
1 second
Why wrong: Hello timer is 2 seconds by default.
B
2 seconds
Default hello timer is 2 seconds.
C
5 seconds
Why wrong: 5 seconds is not a default STP timer.
D
10 seconds
Why wrong: 10 seconds is the default forward delay timer, not hello.

Full breakdown with real-world context →

Question 15easymultiple choice

Open the full VLAN trunking answer →

A network engineer runs the following command on Switch SW8:

SW8# show spanning-tree vlan 80

VLAN0080 Spanning tree enabled protocol ieee Root ID Priority 24656 Address aabb.cc00.0e00 Cost 12 Port 1 (GigabitEthernet0/1) Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32768 (priority 32768 sys-id-ext 80) Address aabb.cc00.0f00 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 Root FWD 12 128.1 P2p Gi0/2 Desg FWD 4 128.2 P2p Gi0/3 Desg FWD 4 128.3 P2p Gi0/4 Altn BLK 4 128.4 P2p

Based on this output, what is the cost of the root port?

A
4
Why wrong: Incorrect. 4 is the cost of other ports, not the root port.
B
8
Why wrong: Incorrect. There is no cost of 8 in the output.
C
12
Correct. The root port Gi0/1 has a cost of 12.
D
16
Why wrong: Incorrect. There is no cost of 16.

Full breakdown with real-world context →

These 350-401 practice questions are part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style 350-401 questions with detailed explanations, topic-based practice, mock exams, readiness tracking, and study analytics.

Spanning Tree Protocol Scenarios

How to approach spanning tree protocol scenarios

Quick answer

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Practice scenarios

Drag and drop the steps for the Spanning Tree Protocol (STP) convergence process in the correct order.

Which TWO characteristics are true about the operation of Rapid PVST+? (Choose two.)

Which TWO STP features are used to improve convergence time after a topology change?

What is the default STP hello timer value in seconds?