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CCNA Spanning Tree Questions

58 questions · Spanning Tree topic · All types, answers revealed

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1
Drag & Dropmedium

Drag and drop the steps of Rapid PVST+ topology change notification process into the correct order, from first to last.

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

Why this order

In Rapid PVST+, when a port transitions to forwarding, the switch sends a proposal message. The neighbor receives it, synchronizes, and sends an agreement. The switch then sets the port to forwarding and propagates the topology change via TC messages.

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2
Multi-Selectmedium

Which two statements about Rapid PVST+ are true? (Choose two.)

Select 2 answers
A.Rapid PVST+ converges faster than classic STP because it uses synchronized handshakes between switches.
B.Rapid PVST+ uses a separate BPDU version for each VLAN to maintain per-VLAN spanning-tree instances.
C.In Rapid PVST+, an alternate port provides a backup path to the root bridge and is in a discarding state when the root port is operational.
D.Rapid PVST+ requires the use of UplinkFast and BackboneFast features to achieve sub-second convergence.
E.Rapid PVST+ supports only one spanning-tree instance per VLAN, but it can load-balance traffic across multiple VLANs.
AnswersA, C

Correct. RSTP uses a proposal-agreement handshake mechanism to achieve rapid transition to forwarding state, unlike classic STP which relies on timers.

Why this answer

Rapid PVST+ is the Cisco implementation of RSTP per VLAN. It provides faster convergence than classic STP and uses port roles (root, designated, alternate, backup) and port states (discarding, learning, forwarding). The alternate port provides a backup to the root port, and the backup port provides a backup to the designated port.

Rapid PVST+ does not use a separate BPDU version for each VLAN; it uses the same RSTP BPDU format. It does not require UplinkFast or BackboneFast since those features are integrated into RSTP.

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3
MCQeasy

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
B.2
C.3
D.4
AnswerC

Correct. Gi0/1, Gi0/2, and Gi0/3 are all in FWD state.

Why this answer

The output shows three ports in Forwarding state: Gi0/1 (Root FWD), Gi0/2 (Desg FWD), and Gi0/3 (Desg FWD). Gi0/4 is in Blocking state (Altn BLK).

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4
MCQmedium

Which of the following is true about the STP max age timer?

A.It is the time a port spends in the listening state.
B.It is the interval between BPDU transmissions.
C.It is the maximum time a switch stores BPDU information before discarding it.
D.It is the time a port waits before transitioning from blocking to listening.
AnswerC

Max age is 20 seconds by default; after that, BPDU info is considered stale.

Why this answer

The max age timer determines how long a switch waits before re-evaluating BPDU information if it stops receiving BPDUs from the root bridge.

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5
MCQhard

An engineer is designing a redundant Layer 2 network with multiple VLANs. The network uses Rapid PVST+ for STP. The engineer wants to ensure that different VLANs have different root bridges to optimize traffic flow. The distribution switches are Cisco Catalyst 9300s. The engineer has configured one distribution switch as the root for VLANs 10 and 20, and the other as the root for VLANs 30 and 40. However, after implementation, the engineer notices that all VLANs have the same root bridge. What is the most likely cause?

A.The engineer used the 'spanning-tree root primary' command without specifying the VLAN, which sets the priority for all VLANs.
B.The engineer enabled BPDU guard on all access ports, which prevents the switch from receiving superior BPDUs.
C.The engineer enabled PortFast on all trunk ports, which causes the switch to ignore BPDUs and become root.
D.The engineer enabled UplinkFast, which forces the switch to become the root bridge for all VLANs.
AnswerA

Correct because the command without the VLAN keyword applies to all VLANs, causing the same switch to be root for all VLANs.

Why this answer

The 'spanning-tree root primary' command without specifying a VLAN sets the bridge priority to 24576 for all VLANs on the switch, making it the root for every VLAN. Since the engineer intended different root bridges per VLAN, this command overrides any per-VLAN priority settings and causes all VLANs to elect the same root bridge.

Exam trap

Cisco often tests the nuance that the 'spanning-tree root primary' command without a VLAN parameter applies to all VLANs, leading candidates to overlook the need for per-VLAN configuration when designing asymmetric root bridges.

How to eliminate wrong answers

Option B is wrong because BPDU guard on access ports disables the port upon receiving a BPDU, but it does not prevent the switch from receiving superior BPDUs on trunk ports or affect root bridge election globally. Option C is wrong because PortFast on trunk ports is not a valid configuration (PortFast is intended for access ports) and even if enabled, it does not cause a switch to ignore BPDUs or become root; PortFast simply transitions the port to forwarding state quickly. Option D is wrong because UplinkFast is a Cisco proprietary feature that improves convergence after a root port failure, but it does not force a switch to become the root bridge for any VLAN.

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6
Matchingmedium

Drag and drop each STP variant on the left to its matching standard on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

IEEE 802.1D

IEEE 802.1w

IEEE 802.1s

Cisco proprietary

Cisco proprietary (based on 802.1w)

Why these pairings

STP is IEEE 802.1D; RSTP is IEEE 802.1w; MSTP is IEEE 802.1s; PVST+ is Cisco proprietary.

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7
MCQhard

A network engineer runs the following command on Switch SW9: SW9# show spanning-tree vlan 90 VLAN0090 Spanning tree enabled protocol ieee Root ID Priority 24666 Address aabb.cc00.1000 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 24666 (priority 24576 sys-id-ext 90) Address aabb.cc00.1000 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 Gi0/4 Desg FWD 4 128.4 P2p Based on this output, what is the base priority of the root bridge?

A.24576
B.24666
C.32768
D.32858
AnswerA

Correct. 24576 is the base priority (24666 - 90 = 24576).

Why this answer

The root bridge priority is 24666, which includes the system ID extension of 90. The base priority is 24666 - 90 = 24576.

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8
Drag & Dropmedium

Drag and drop the steps of MSTP region and instance configuration steps into the correct order, from first to last.

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

Why this order

MSTP configuration begins with entering MST configuration mode, then assigning the region name, revision number, and mapping VLANs to instances. After exiting configuration mode, the MST region is active. Finally, the spanning-tree mode must be set to mst globally to enable MSTP.

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9
MCQmedium

A network engineer is troubleshooting an STP issue in a switched network. The network has two distribution switches connected via a trunk, and each distribution switch connects to the same access switch. The engineer notices that the root bridge is not the intended distribution switch. Upon checking, the engineer sees that the access switch has a higher priority than the distribution switches. The engineer needs to ensure that the intended distribution switch becomes the root bridge without causing a temporary loop. What should the engineer do?

A.Configure the 'spanning-tree vlan vlan-id root primary' command on the intended distribution switch.
B.Set the priority of the access switch to 0 using the 'spanning-tree vlan vlan-id priority 0' command.
C.Increase the priority of the distribution switch to 61440 using the 'spanning-tree vlan vlan-id priority 61440' command.
D.Disable STP on the distribution switch and manually configure it as the root bridge.
AnswerA

Correct because this command sets the switch priority to 24576 (or lower if needed) to ensure it becomes the root bridge without manual configuration.

Why this answer

Option A is correct because the 'spanning-tree vlan vlan-id root primary' command dynamically sets the switch's bridge priority to 24576 (or 4096 if the current root has a priority lower than 24576) and ensures the switch becomes the root bridge without manual priority miscalculation. This command also adjusts the priority of neighboring switches if needed, preventing temporary loops by avoiding the need to disable or reset STP. It is the safest and most efficient method to force a specific switch to become the root bridge in a live network.

Exam trap

Cisco often tests the misconception that increasing a switch's priority (making it numerically higher) helps it become root, when in fact the root bridge is elected based on the lowest bridge priority value.

How to eliminate wrong answers

Option B is wrong because setting the access switch's priority to 0 would make it the root bridge, which is the opposite of the intended goal (the distribution switch should be root). Option C is wrong because increasing the distribution switch's priority to 61440 (a high value) would make it less likely to become the root bridge, not more; the root bridge is elected with the lowest priority value. Option D is wrong because disabling STP on the distribution switch would break loop prevention entirely, potentially causing a Layer 2 loop and network outage, and manually configuring it as root without STP is not a valid or safe method.

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10
Multi-Selecteasy

Which two statements about PortFast are true? (Choose two.)

Select 2 answers
A.PortFast allows a port to transition directly from blocking to forwarding state.
B.PortFast should be enabled on ports that connect to end-user devices.
C.PortFast disables BPDU processing on the port.
D.PortFast is automatically enabled on all trunk ports.
E.PortFast changes the root bridge election process.
AnswersA, B

Correct because PortFast bypasses the listening and learning states, enabling immediate forwarding.

Why this answer

PortFast is a Cisco enhancement that allows a port to transition immediately from blocking to forwarding, bypassing the listening and learning states. It is intended for ports connected to end hosts, not to other switches. When PortFast is enabled, the port still participates in STP BPDU processing, but the BPDU guard feature can be used to protect against accidental loops.

PortFast does not affect the root bridge election or the designated port selection process.

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11
Multi-Selecthard

Which three statements about the Multiple Spanning Tree Protocol (MSTP) are true? (Choose three.)

Select 3 answers
A.MSTP allows multiple VLANs to be mapped to a single spanning-tree instance.
B.MSTP uses an Internal Spanning Tree (IST) to interconnect MST regions.
C.MSTP is backward compatible with 802.1D and RSTP.
D.MSTP requires a separate spanning-tree instance for every VLAN.
E.MSTP uses a different BPDU format than RSTP.
AnswersA, B, C

Correct because MSTP reduces the number of STP instances by grouping VLANs, improving scalability.

Why this answer

MSTP (802.1s) allows mapping multiple VLANs to a single spanning-tree instance, reducing the number of STP instances needed. It uses an internal spanning tree (IST) to interconnect MST regions. MSTP is backward compatible with 802.1D and RSTP through the use of common spanning tree (CST) at the region boundary.

MSTP does not require a separate instance for every VLAN like PVST+; it groups VLANs into instances. MSTP uses the same BPDU format as RSTP with additional MST-specific information.

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12
Matchingmedium

Drag and drop each STP port role on the left to its matching definition on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Best path to the root bridge

Best path for a given segment

Alternate path to the root bridge

Redundant path to the same segment

Why these pairings

Root port is the best path to the root bridge; Designated port is the best path for a segment; Alternate port provides an alternative path to the root; Backup port provides a redundant path to the same segment.

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13
Drag & Dropmedium

Drag and drop the steps of STP root guard and loop guard activation into the correct order, from first to last.

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

Why this order

Root guard is configured on a port to prevent it from becoming a root port. Loop guard is used to prevent alternate ports from transitioning to forwarding when BPDUs are lost. Both are applied at the interface level.

Root guard is configured first, then loop guard. Verification confirms the port state and protection status.

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14
MCQeasy

What is the default STP hello timer value in seconds?

A.1 second
B.2 seconds
C.5 seconds
D.10 seconds
AnswerB

Default hello timer is 2 seconds.

Why this answer

The default hello timer in STP is 2 seconds, used to send BPDUs on the root bridge.

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15
Matchingmedium

Drag and drop each STP port role on the left to its matching definition on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Best path from a non-root bridge to the root bridge

Best path for a LAN segment, forwards traffic

Alternate path to the root bridge (discarding in RSTP)

Backup path to a shared segment (discarding in RSTP)

Administratively shut down or not running STP

Why these pairings

Root port is the best path to the root bridge; Designated port is the best path for a segment; Alternate port provides an alternative path to the root bridge; Backup port provides a backup path to a shared segment.

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16
MCQmedium

interface GigabitEthernet0/2 spanning-tree link-type point-to-point end What is the effect of this configuration?

A.The port will use RSTP fast transition mechanisms assuming a point-to-point link.
B.The port will become a designated port immediately.
C.The port will disable STP on that link.
D.The port will use shared medium behavior.
AnswerA

RSTP uses point-to-point links for rapid convergence.

Why this answer

This manually sets the link type to point-to-point, which enables Rapid Spanning Tree (RSTP) fast transitions on that port.

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17
Matchingmedium

Drag and drop each STP variant on the left to its matching IEEE standard on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

IEEE 802.1D

IEEE 802.1w

IEEE 802.1s

Cisco proprietary per-VLAN spanning tree

Why these pairings

STP is 802.1D; RSTP is 802.1w; MSTP is 802.1s; PVST+ is a Cisco proprietary extension of 802.1D.

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18
MCQmedium

A network engineer is troubleshooting a Layer 2 loop issue. The network consists of three switches: SW1, SW2, and SW3, all connected in a triangle. The engineer notices that SW1 is the root bridge. After a link failure between SW1 and SW2, the network experiences a temporary loop. The engineer wants to prevent such loops in the future by enabling a feature that provides faster convergence and prevents temporary loops during topology changes. The engineer is using Rapid PVST+. Which feature should the engineer enable?

A.Enable Loop Guard on all switch ports.
B.Enable BPDU Guard on all switch ports.
C.Enable Root Guard on all switch ports.
D.Enable UDLD on all fiber links.
AnswerA

Correct because Loop Guard prevents loops by keeping a port in blocking state if BPDUs are not received, ensuring that a port does not transition to forwarding incorrectly.

Why this answer

When a link fails in a triangle topology with Rapid PVST+, the switch that lost its root port may temporarily transition a blocked alternate port to forwarding before the new root port is fully synchronized, causing a loop. Enabling Loop Guard on all switch ports prevents this by keeping a port in a blocking state if BPDUs are not received, ensuring that a port does not erroneously transition to forwarding during a topology change. This provides faster convergence without temporary loops by enforcing BPDU-based loop prevention.

Exam trap

The trap here is that candidates often confuse Loop Guard with UDLD or BPDU Guard, thinking that any loop-prevention feature will solve temporary loops, but only Loop Guard directly addresses the scenario where a port transitions to forwarding due to loss of BPDUs during a topology change.

How to eliminate wrong answers

Option B is wrong because BPDU Guard is designed to protect against unauthorized devices by shutting down a port if a BPDU is received on a PortFast-enabled port, but it does not prevent temporary loops during topology changes in a triangle topology. Option C is wrong because Root Guard prevents a port from becoming a root port if it receives superior BPDUs, which is irrelevant to the loop caused by a link failure when SW1 is already the root bridge. Option D is wrong because UDLD (Unidirectional Link Detection) detects unidirectional links on fiber ports but does not prevent loops caused by the rapid transition of ports during a topology change in a triangle topology.

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19
Multi-Selectmedium

Which three statements about STP topology changes and convergence are true? (Choose three.)

Select 3 answers
A.A switch that detects a topology change sends a TCN BPDU toward the root bridge.
B.The root bridge sets the Topology Change (TC) flag in its BPDUs after receiving a TCN.
C.When the TC flag is set, switches reduce the MAC address aging timer to the forward delay time.
D.The Max Age timer is used to flush MAC address entries during a topology change.
E.The forward delay timer determines how long a switch waits before transitioning from listening to learning state.
AnswersA, B, C

Correct because the TCN (Topology Change Notification) is sent to inform the root bridge of a change.

Why this answer

When a topology change occurs in 802.1D STP, the switch that detects the change sends a TCN BPDU toward the root bridge. The root bridge then sets the TC flag in its BPDUs, causing all switches to shorten their MAC address aging timers to flush stale entries. This process ensures rapid convergence of the forwarding database.

The Max Age timer is used to age out BPDU information, not to flush MAC addresses. The forward delay timer is used during listening and learning states, not directly for MAC aging.

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20
MCQhard

An engineer is designing a Layer 2 network with redundancy. The network uses MST (Multiple Spanning Tree) to reduce the number of STP instances. The engineer has configured two regions: Region 1 and Region 2. The engineer notices that switches in Region 1 are not forming a single MST region, and instead, they are treating each other as if they are in different regions. The engineer checks the configuration and finds that the region name and revision number are the same on all switches in Region 1, but the VLAN-to-instance mapping is different on one switch. What is the most likely cause of the issue?

A.The VLAN-to-instance mapping is not consistent across all switches in Region 1.
B.The root bridge for each MST instance is not configured correctly.
C.BPDU Guard is enabled on the inter-switch links, preventing BPDU exchange.
D.PortFast is enabled on the inter-switch links, causing the switches to ignore BPDUs.
AnswerA

Correct because MST requires identical VLAN-to-instance mapping, region name, and revision number for switches to be in the same region.

Why this answer

In MST, all switches within a region must agree on three parameters: the region name, the revision number, and the VLAN-to-instance mapping. Even if the region name and revision number match, a single mismatch in the VLAN-to-instance mapping causes the switches to treat each other as if they belong to different regions, preventing them from forming a single MST region.

Exam trap

Cisco often tests the fact that all three components of the MST configuration (name, revision, and VLAN-to-instance mapping) must match exactly for switches to be in the same region, and candidates mistakenly think only the name and revision matter.

How to eliminate wrong answers

Option B is wrong because the root bridge configuration for each MST instance affects the spanning-tree topology within the region but does not determine whether switches belong to the same region; region membership is based solely on the MST configuration identifier (name, revision, mapping). Option C is wrong because BPDU Guard is a port security feature that shuts down a port upon receiving a BPDU, but it does not prevent BPDU exchange before the port is err-disabled; moreover, the issue described is about region formation, not BPDU filtering. Option D is wrong because PortFast immediately transitions a port to the forwarding state but does not cause switches to ignore BPDUs; BPDUs are still processed, and PortFast does not affect MST region formation.

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21
Drag & Dropmedium

Drag and drop the steps of MST region configuration and operation into the correct order, from first to last.

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

Why this order

MST configuration begins with entering MST mode and defining the region name, revision number, and VLAN-to-instance mapping. After configuration, the switch computes an MD5 digest of the MST configuration to identify region membership. Switches in the same region then run IST (Internal Spanning Tree) and CIST (Common and Internal Spanning Tree) to elect a root bridge for the region.

Finally, per-instance spanning trees are calculated within the region.

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22
MCQmedium

A network engineer is troubleshooting a Layer 2 loop that occurred in a network using Rapid PVST+. The network has three switches: SW1 (root), SW2, and SW3. The engineer examines the topology and finds that SW2 and SW3 are connected via a link that is not supposed to be there. The engineer suspects that an unauthorized switch was connected to the network, causing the loop. The engineer wants to prevent such loops in the future by configuring a feature that will disable any port that receives a BPDU from an unauthorized switch. Which feature should the engineer configure on the access ports?

A.Enable BPDU Guard on all access ports.
B.Enable Loop Guard on all access ports.
C.Enable Root Guard on all access ports.
D.Enable UDLD on all access ports.
AnswerA

Correct because BPDU Guard disables a port if a BPDU is received, preventing unauthorized switches from causing loops.

Why this answer

BPDU Guard is the correct feature because it immediately error-disables a port when a BPDU is received, preventing loops from unauthorized switches. Since the engineer wants to protect access ports from receiving BPDUs (which should never occur on a properly configured access port), BPDU Guard directly addresses the scenario of an unauthorized switch being connected and sending BPDUs.

Exam trap

Cisco often tests the distinction between BPDU Guard and Root Guard, where candidates mistakenly choose Root Guard because they think it protects against unauthorized switches, but Root Guard only prevents a port from becoming root, not from receiving BPDUs and causing loops.

How to eliminate wrong answers

Option B is wrong because Loop Guard prevents alternate or root ports from becoming designated in the absence of BPDUs, but it does not disable a port upon receiving an unexpected BPDU; it only prevents loops caused by unidirectional link failures. Option C is wrong because Root Guard prevents a port from becoming a root port by placing it into a root-inconsistent state if a superior BPDU is received, but it does not disable the port; it still allows BPDU reception and does not block all BPDUs from unauthorized switches. Option D is wrong because UDLD detects and disables ports experiencing unidirectional links, but it does not react to BPDU reception; it uses its own keepalive mechanism and is unrelated to preventing loops from unauthorized switches sending BPDUs.

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23
MCQmedium

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 24586 Address aabb.cc00.0100 This bridge is the root Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 24586 (priority 24576 sys-id-ext 10) 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 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.SW1 is the root bridge for VLAN 10, and all its interfaces are in the Designated role.
B.SW1 is not the root bridge; the root bridge has MAC address aabb.cc00.0100 but is a different switch.
C.SW1 has a port in the Blocking state, preventing loops.
D.The root bridge priority for VLAN 10 is 24576 without the system ID extension.
AnswerA

Correct. The output explicitly states 'This bridge is the root' and all interfaces are Desg FWD.

Why this answer

The output explicitly states 'This bridge is the root' and shows all three interfaces (Gi0/1, Gi0/2, Gi0/3) in the Designated (Desg) role with a Forwarding (FWD) state. In a stable STP topology, only the root bridge has all its active ports as Designated; non-root bridges will have at least one Root port. Therefore, SW1 is the root bridge for VLAN 10, and all its interfaces are in the Designated role.

Exam trap

Cisco often tests the distinction between the configured bridge priority (without the system ID extension) and the effective priority displayed in the 'show spanning-tree' output, leading candidates to mistakenly think the root priority is 24576 when it is actually 24586.

How to eliminate wrong answers

Option B is wrong because the output clearly states 'This bridge is the root' and the Bridge ID address matches the Root ID address (aabb.cc00.0100), confirming SW1 itself is the root bridge, not a different switch. Option C is wrong because all three interfaces show a state of FWD (Forwarding), and no Blocking state is listed; the output shows no blocked ports, so a loop is prevented by the root bridge having all Designated ports. Option D is wrong because the Bridge ID Priority is shown as 24586, which is the sum of the configured priority 24576 and the system ID extension 10 (VLAN 10); the effective root bridge priority is 24586, not 24576 without the extension.

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24
MCQeasy

A network engineer is configuring a new switch that will be used as an access layer switch. The switch connects to two distribution switches via trunk links. The engineer wants to ensure that the access switch does not become the root bridge for any VLAN. The engineer also wants to provide redundancy so that if one uplink fails, the other uplink takes over quickly. The engineer is using Rapid PVST+. What configuration should the engineer apply on the access switch?

A.Configure 'spanning-tree vlan vlan-list priority 61440' on the access switch.
B.Configure 'spanning-tree vlan vlan-list priority 0' on the access switch.
C.Enable UplinkFast on the access switch to provide fast failover.
D.Enable PortFast on the trunk ports to speed up convergence.
AnswerA

Correct because setting the priority to 61440 ensures the access switch will not become root, and Rapid PVST+ provides fast convergence automatically.

Why this answer

Option A is correct because setting the spanning-tree priority to 61440 (which is 0xF000 in hex) makes the switch a very unlikely root bridge candidate. In Rapid PVST+, the bridge priority is a 4-bit value (0-15) multiplied by 4096, so 61440 corresponds to priority 15 — the highest possible value. This ensures the access switch will never become the root bridge for any VLAN, while Rapid PVST+ provides fast failover (sub-second convergence) via its alternate/backup port mechanism without needing UplinkFast.

Exam trap

Cisco often tests the misconception that UplinkFast is needed with Rapid PVST+ for fast failover, but Rapid PVST+ already includes its own fast convergence (based on the 802.1w standard), making UplinkFast obsolete.

How to eliminate wrong answers

Option B is wrong because setting priority 0 makes the switch the most likely root bridge candidate, which directly contradicts the requirement to never become root. Option C is wrong because UplinkFast is a legacy Cisco proprietary feature for 802.1D STP; Rapid PVST+ already provides fast failover (typically 1-2 seconds) via its own convergence mechanism, making UplinkFast unnecessary and redundant. Option D is wrong because PortFast is designed for access ports connected to end hosts to bypass listening/learning states; applying it to trunk ports would disable STP on those links, risking loops and violating the requirement for redundancy with STP protection.

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25
MCQmedium

interface GigabitEthernet0/3 spanning-tree guard root end What is the effect of this configuration?

A.The port will error-disable if it receives a BPDU that would cause the switch to become a non-root bridge.
B.The port will block all BPDUs received from other switches.
C.The port will become the root port for the VLAN.
D.The port will ignore BPDUs from switches with lower bridge ID.
AnswerA

Root Guard protects the root bridge position by disabling ports that receive superior BPDUs.

Why this answer

Root Guard is enabled on the port, which will error-disable the port if a superior BPDU (indicating a potential root bridge) is received.

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26
Drag & Dropmedium

Drag and drop the steps of MSTP region and instance configuration steps into the correct order, from first to last.

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

Why this order

MSTP configuration begins with entering MST configuration mode, assigning a region name and revision number, mapping VLANs to instances, and then activating the configuration. Finally, the MST instance priority is set to influence root bridge selection.

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27
Drag & Dropmedium

Drag and drop the steps of Rapid PVST+ convergence process into the correct order, from first to last.

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

Why this order

Rapid PVST+ first elects the root bridge and determines port roles. It then uses synchronization handshakes between bridges to quickly transition ports to forwarding without relying on timers. Edge ports (connected to hosts) immediately transition to forwarding.

Finally, the topology change notification propagates to update MAC address tables.

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28
Matchingmedium

Drag and drop each STP protection feature on the left to its matching purpose on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Immediately transitions a port to forwarding state

Err-disables a port if a BPDU is received

Prevents a port from becoming the root port

Prevents a port from transitioning to forwarding when BPDUs stop

Why these pairings

PortFast moves a port to forwarding immediately; BPDU Guard err-disables a port upon BPDU reception; Root Guard prevents a port from becoming root; Loop Guard prevents alternate/backup ports from transitioning to forwarding.

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29
MCQmedium

spanning-tree vlan 10 priority 4096 What is the effect of this global configuration command?

A.The switch will have a bridge priority of 4096 for VLAN 10, increasing its chance to become root bridge.
B.The switch will have a bridge priority of 4096 for all VLANs.
C.The switch will become the root bridge for VLAN 10 immediately.
D.The switch will have a bridge priority of 4096 for VLAN 10 and all other VLANs will use 32768.
AnswerA

Lower priority value is preferred; 4096 is lower than default 32768.

Why this answer

This sets the bridge priority for VLAN 10 to 4096, making the switch more likely to become the root bridge for that VLAN.

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30
Multi-Selecteasy

Which two statements about STP port roles and states are true? (Choose two.)

Select 2 answers
A.A root port is the port on a non-root bridge that provides the best path to the root bridge.
B.A designated port is the port on a segment that has the lowest path cost to the root bridge, and there can be multiple designated ports on the same segment.
C.In classic STP, a port in the blocking state can still send and receive BPDUs.
D.An alternate port is a port that provides a backup path to the root bridge and is in the forwarding state when the root port is active.
E.A backup port is a port that provides a redundant connection to the same segment and is in the learning state when the designated port is active.
AnswersA, C

Correct. The root port is selected based on the lowest root path cost to the root bridge.

Why this answer

In classic STP (802.1D), a port can be in blocking, listening, learning, forwarding, or disabled state. The root port is the port on a non-root bridge that has the best path to the root bridge. A designated port is the port on a segment that has the best path to the root bridge; there is exactly one designated port per segment.

Alternate and backup ports are roles defined in RSTP, not classic STP. A port in blocking state does not send or receive user data but can still receive BPDUs.

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31
MCQhard

An engineer is configuring a new access switch that connects to two distribution switches via trunk links. The distribution switches are configured with Rapid PVST+ and are both running as root bridges for different VLANs. The engineer wants to ensure that the access switch does not become the root bridge for any VLAN, even if the distribution switches fail. The engineer also wants to prevent any unauthorized switch from becoming root. What configuration should the engineer apply on the access switch?

A.Configure 'spanning-tree vlan 1-4094 priority 61440' and enable Root Guard on the uplink ports.
B.Configure 'spanning-tree vlan 1-4094 priority 0' and enable BPDU Guard on the uplink ports.
C.Configure 'spanning-tree vlan 1-4094 priority 4096' and enable Loop Guard on the uplink ports.
D.Configure 'spanning-tree vlan 1-4094 priority 61440' and enable BPDU Guard on the uplink ports.
AnswerA

Correct because setting the priority to 61440 ensures the switch will not become root, and Root Guard on uplinks prevents any superior BPDUs from making the switch root.

Why this answer

Option A is correct because setting the spanning-tree priority to 61440 (the highest possible value) ensures the access switch will never become the root bridge, even if the current root bridges fail. Enabling Root Guard on the uplink ports prevents any unauthorized switch from becoming root by placing the port into a root-inconsistent state if a superior BPDU is received, thus protecting the root bridge election.

Exam trap

Cisco often tests the distinction between Root Guard and BPDU Guard, where candidates mistakenly apply BPDU Guard (which shuts down ports receiving any BPDU) instead of Root Guard (which specifically protects the root bridge election) on trunk links.

How to eliminate wrong answers

Option B is wrong because setting the priority to 0 makes the access switch the most likely candidate to become root, which directly contradicts the requirement to prevent it from becoming root. Option C is wrong because priority 4096 is a low value that could allow the access switch to become root if the distribution switches fail, and Loop Guard prevents alternate/root port loops but does not protect against unauthorized root bridges. Option D is wrong because while the priority 61440 is correct, BPDU Guard is used to shut down ports that receive BPDUs (typically on access ports), not to prevent unauthorized root bridges on trunk links; Root Guard is the appropriate feature for this purpose.

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32
Matchingmedium

Drag and drop each STP timer on the left to its matching default value on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

2 seconds

15 seconds

20 seconds

Why these pairings

Hello timer defaults to 2 seconds; Forward delay defaults to 15 seconds; Max age defaults to 20 seconds.

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33
Drag & Dropmedium

Drag and drop the steps of STP root guard and loop guard activation into the correct order, from first to last.

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

Why this order

Root guard is enabled on an interface to prevent it from becoming a root port. Loop guard is enabled to prevent alternate/backup ports from transitioning to forwarding. Both features are configured per interface, then verified.

Root guard places the port in root-inconsistent state if a superior BPDU is received, while loop guard places it in loop-inconsistent state.

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34
Matchingmedium

Drag and drop each STP port state on the left to its matching function on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Discards frames, does not learn MAC addresses

Discards frames, does not learn MAC addresses (receives BPDUs)

Discards frames, learns MAC addresses

Forwards frames, learns MAC addresses

Administratively down, discards frames

Why these pairings

Blocking discards frames and does not learn MACs; Listening discards frames but does not learn MACs (receives BPDUs); Learning discards frames but learns MACs; Forwarding forwards frames and learns MACs; Disabled administratively down and discards frames.

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35
Multi-Selectmedium

Which two statements about Rapid PVST+ are true? (Choose two.)

Select 2 answers
A.Rapid PVST+ uses a proposal/agreement handshake to achieve rapid convergence.
B.Rapid PVST+ runs a separate instance of STP for each VLAN.
C.Rapid PVST+ requires the UplinkFast feature to be enabled for fast uplink convergence.
D.In Rapid PVST+, the root bridge is elected based on the lowest MAC address only.
E.Rapid PVST+ supports only two port roles: designated and root.
AnswersA, B

Correct because the proposal/agreement mechanism allows ports to transition to forwarding quickly without relying on timers.

Why this answer

Rapid PVST+ is an enhancement of the original 802.1D STP that provides faster convergence by using a proposal/agreement handshake. It runs a separate instance of RSTP for each VLAN, enabling per-VLAN load balancing. The UplinkFast feature is not needed because RSTP already handles uplink convergence quickly.

The root bridge is elected based on bridge priority, not MAC address alone. Port roles include alternate and backup, not just designated and root.

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36
Drag & Dropmedium

Drag and drop the steps of STP path cost manipulation for load balancing into the correct order, from first to last.

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

Why this order

To load balance with STP, first identify redundant links. Then change the path cost on one switch's port to make it less preferred. This alters the root port selection.

The switch recalculates the spanning tree, and traffic is redirected to the lower-cost path. Finally, verify the new root port and forwarding state.

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37
Multi-Selectmedium

Which three statements about STP convergence and timers are true? (Choose three.)

Select 3 answers
A.The default Max Age timer in classic STP is 20 seconds.
B.The Forward Delay timer determines how long a port stays in the listening and learning states, with a default of 15 seconds each.
C.RSTP eliminates the need for the Forward Delay timer by using a proposal-agreement handshake mechanism.
D.The Hello timer in STP is used to determine how often a switch sends BPDUs, with a default value of 5 seconds.
E.UplinkFast is a standard IEEE 802.1D feature that reduces convergence time after a root port failure.
AnswersA, B, C

Correct. Max Age defaults to 20 seconds, which is the time a switch waits to hear a BPDU from the root bridge before declaring it dead.

Why this answer

Classic STP convergence relies on timers: Hello (2 sec), Max Age (20 sec), Forward Delay (15 sec). Max Age defines how long a switch waits without receiving a BPDU before re-evaluating the root. Forward Delay is the time spent in listening and learning states (each 15 sec).

The total convergence time can be up to 50 seconds (20 sec Max Age + 15 sec listening + 15 sec learning). RSTP improves convergence by using handshakes instead of timers. UplinkFast is a Cisco proprietary feature that reduces convergence time after a root port failure, not a standard STP timer.

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38
Matchingmedium

Drag and drop each STP protection feature on the left to its matching purpose on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Immediately transitions a port to forwarding state (access ports)

Disables a port if a BPDU is received (protects against rogue switches)

Prevents a port from becoming a root port (enforces root bridge location)

Prevents a port from becoming designated if BPDUs stop (prevents loops)

Detects and disables unidirectional links

Why these pairings

PortFast moves a port to forwarding immediately; BPDU Guard disables a port if a BPDU is received; Root Guard prevents a port from becoming a root port; Loop Guard prevents alternate/backup ports from becoming designated if BPDUs stop.

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39
MCQhard

A network engineer is troubleshooting an STP issue in a network that uses Rapid PVST+. The network has a root bridge (SW1) and a secondary root bridge (SW2). The engineer notices that after a link failure between SW1 and SW2, the network takes longer than expected to converge. The engineer checks the configuration and finds that SW2 has the 'spanning-tree uplinkfast' command enabled. The engineer also notices that SW2 has a lower priority than SW1. What is the most likely cause of the slow convergence?

A.UplinkFast is enabled, which is incompatible with Rapid PVST+ and causes the switch to use legacy STP convergence.
B.SW2 has a lower priority than SW1, so it takes longer to become the root bridge after failure.
C.BPDU Guard is enabled on the uplink ports, which prevents BPDU exchange.
D.Loop Guard is enabled on the uplink ports, which delays port transition.
AnswerA

Correct because UplinkFast is not needed with Rapid PVST+ and can actually degrade performance by forcing the switch to use slower convergence mechanisms.

Why this answer

UplinkFast is a legacy STP feature that is incompatible with Rapid PVST+. When enabled on a switch running Rapid PVST+, it forces the switch to revert to 802.1D STP convergence behavior on the affected ports, disabling the rapid transition mechanisms (such as proposal/agreement and sync). This causes the network to take longer to converge after a link failure, as the switch falls back to the slower listening and learning states.

Exam trap

Cisco often tests the misconception that UplinkFast is a harmless optimization that can be combined with Rapid PVST+, when in fact it forces a fallback to legacy STP behavior, causing slow convergence.

How to eliminate wrong answers

Option B is wrong because SW2 having a lower priority than SW1 means SW2 is less likely to become the root bridge; after a failure, the switch with the lowest priority becomes root, so a lower priority (higher numerical value) does not cause slower convergence. Option C is wrong because BPDU Guard would disable a port upon receiving a BPDU, preventing BPDU exchange entirely, which would cause a different failure mode (port errdisable) rather than slow convergence. Option D is wrong because Loop Guard prevents alternate/backup ports from transitioning to forwarding when BPDUs stop, which can cause a blocking state but does not inherently delay port transition in a way that explains longer-than-expected convergence after a link failure.

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40
MCQeasy

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
B.GigabitEthernet0/2
C.GigabitEthernet0/3
D.There is no alternate port.
AnswerC

Correct. Gi0/3 is the alternate port (Altn BLK).

Why this answer

The alternate port is the port that provides an alternative path to the root bridge and is placed in blocking state. In the output, Gi0/3 is shown as 'Altn BLK'.

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41
Drag & Dropmedium

Drag and drop the steps of STP path cost manipulation for load balancing into the correct order, from first to last.

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

Why this order

Path cost manipulation adjusts the cost of a port to influence root port selection and load balance traffic. The process starts by identifying the VLANs to load balance, then entering interface configuration, setting the port priority or cost, and verifying the new root port. Finally, traffic is distributed across multiple links.

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42
Drag & Dropmedium

Drag and drop the steps of STP portfast and BPDU guard configuration into the correct order, from first to last.

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

Why this order

PortFast is configured on an access port to immediately transition to forwarding. BPDU guard is then enabled to protect against rogue BPDUs. The configuration is applied at the interface level, and verification ensures the port is in forwarding state.

If a BPDU is received, BPDU guard errdisables the port.

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43
Matchingmedium

Drag and drop each STP port state on the left to its matching function on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

Discards frames and listens for BPDUs

Listens for BPDUs only, no MAC learning

Learns MAC addresses but does not forward frames

Forwards frames and learns MAC addresses

Administratively shut down, no participation

Why these pairings

Blocking discards frames and listens for BPDUs; Listening listens for BPDUs only; Learning learns MAC addresses but does not forward; Forwarding sends and receives frames; Disabled is administratively down.

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44
MCQmedium

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.
B.GigabitEthernet0/3 is in the Blocking state to prevent a loop.
C.The root port cost is 8.
D.SW2's bridge priority is 32768.
AnswerB

Correct. Gi0/3 is shown as Altn BLK (Alternate, Blocking), which prevents a loop.

Why this answer

SW2 is not the root bridge (its bridge priority 32778 is higher than root priority 24596). Gi0/1 is the root port (cost 4 to root), Gi0/2 is a designated port, and Gi0/3 is an alternate port in blocking state. The root bridge is at MAC aabb.cc00.0200.

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45
MCQeasy

A network engineer is troubleshooting a connectivity issue in a switched network. The network uses Rapid PVST+ with multiple VLANs. The engineer notices that a host connected to an access port on SW1 cannot communicate with the default gateway, which is on a distribution switch. The access port is configured with PortFast and BPDU Guard. The engineer checks the switch logs and sees that the port went into errdisable state. What is the most likely cause of the errdisable state?

A.Another switch was connected to the access port, causing BPDU Guard to disable the port.
B.A broadcast storm occurred due to a loop in the network.
C.The host connected to the port caused a duplex mismatch.
D.The cable connecting the host is faulty, causing link flaps.
AnswerA

Correct because BPDU Guard disables a PortFast-enabled port if a BPDU is received, which happens when another switch is connected.

Why this answer

The access port is configured with PortFast and BPDU Guard. PortFast immediately transitions the port to forwarding, but BPDU Guard monitors for incoming BPDUs. When another switch is connected to this access port, it sends BPDUs, triggering BPDU Guard to error-disable the port to prevent a potential bridging loop.

This matches the log entry showing the port went into errdisable state.

Exam trap

Cisco often tests the distinction between BPDU Guard (which reacts to BPDUs) and other errdisable causes like loop guard, UDLD, or link-flap; the trap here is assuming that any errdisable on an access port must be due to a physical issue (duplex, cable) rather than a deliberate STP protection mechanism.

How to eliminate wrong answers

Option B is wrong because a broadcast storm due to a loop would typically cause high CPU utilization and potential port flapping, but it would not directly trigger BPDU Guard to error-disable a port; BPDU Guard specifically reacts to BPDU reception, not broadcast storms. Option C is wrong because a duplex mismatch causes CRC errors, late collisions, and performance degradation, but it does not cause BPDU Guard to disable the port; duplex mismatch is detected by interface counters, not by BPDU Guard. Option D is wrong because a faulty cable causing link flaps would result in the port repeatedly going up/down, which could trigger errdisable due to link-flap protection (if configured), but not BPDU Guard; the logs specifically mention errdisable from BPDU Guard, not from link flaps.

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46
MCQmedium

spanning-tree mode rapid-pvst What is the effect of this global configuration command?

A.The switch will use Rapid PVST+ for all VLANs, providing faster convergence than classic STP.
B.The switch will use MSTP for all VLANs.
C.The switch will use classic STP for all VLANs.
D.The switch will disable STP on all ports.
AnswerA

Rapid PVST+ is the Cisco implementation of RSTP per VLAN.

Why this answer

This enables Rapid PVST+ mode, which runs RSTP per VLAN for faster convergence.

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47
MCQmedium

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.
B.The port will go through normal STP states and will be error-disabled if a BPDU is received.
C.The port will immediately transition to forwarding and ignore any BPDUs received.
D.The port will remain in blocking state until a BPDU is received.
AnswerA

PortFast causes immediate forwarding; BPDU Guard error-disables the port upon BPDU reception.

Why this answer

PortFast and BPDU Guard are enabled on the interface, which immediately transitions the port to forwarding and disables it if a BPDU is received.

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48
MCQmedium

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
B.24636
C.32768
D.32828
AnswerB

Correct. The Root ID priority is 24636.

Why this answer

The root bridge priority is shown in the Root ID section as 24636. This includes the system ID extension of 60, so the base priority is 24576 (24636 - 60 = 24576).

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49
Matchingmedium

Drag and drop each STP timer on the left to its matching default value on the right.

Drag a concept onto its matching description — or click a concept then click the description.

Concepts
Matches

2 seconds

15 seconds

20 seconds

32768

4

Why these pairings

Hello time default is 2 seconds; Forward delay default is 15 seconds; Max age default is 20 seconds.

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50
MCQeasy

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
B.8
C.12
D.16
AnswerC

Correct. The root port Gi0/1 has a cost of 12.

Why this answer

The root port is Gi0/1, and its cost is shown as 12 in the interface table.

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51
MCQmedium

interface GigabitEthernet0/4 spanning-tree vlan 20 cost 100 end What is the effect of this configuration?

A.The port cost for VLAN 20 is set to 100, making it more likely to be selected as root port if lower than other paths.
B.The port cost for all VLANs is set to 100.
C.The port will become a designated port for VLAN 20.
D.The port will have a higher priority in the spanning-tree algorithm.
AnswerA

Lower cost is preferred; 100 is lower than default for GigabitEthernet (4).

Why this answer

This sets the STP path cost for VLAN 20 on this interface to 100, influencing the root port selection.

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52
Multi-Selecthard

Which three statements about Multiple Spanning Tree Protocol (MSTP) are true? (Choose three.)

Select 3 answers
A.MSTP allows multiple VLANs to be grouped into a single spanning-tree instance, reducing CPU and memory usage.
B.In MSTP, the Internal Spanning Tree (IST) instance is instance 0 and is always present in every MST region.
C.MSTP requires that all switches in the same MST region have the same VLAN-to-instance mapping, revision number, and region name.
D.MSTP automatically load-balances traffic across all available uplinks without any configuration.
E.MSTP requires a separate root bridge to be elected for each VLAN in the network.
AnswersA, B, C

Correct. This is the primary benefit of MSTP: mapping many VLANs to fewer STP instances.

Why this answer

MSTP (IEEE 802.1s) allows multiple VLANs to be mapped to a single spanning-tree instance (MST instance), reducing the number of STP instances needed. It uses an Internal Spanning Tree (IST) instance (instance 0) that always runs and carries BPDUs for the region. Switches in the same MST region must have identical VLAN-to-instance mappings, revision number, and region name.

MSTP interoperates with Rapid PVST+ at region boundaries by using PVST simulation mode. MSTP does not require a separate root bridge for each VLAN; instead, each MST instance has its own root bridge.

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53
MCQeasy

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
B.GigabitEthernet0/2
C.GigabitEthernet0/3
D.There is no root port because SW4 is the root bridge.
AnswerA

Correct. Gi0/1 is shown with role 'Root'.

Why this answer

The root port is the port that provides the best path to the root bridge. In the output, Gi0/1 is listed as 'Root FWD', indicating it is the root port.

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54
MCQeasy

What is the default STP port cost for a 10 Gigabit Ethernet interface?

A.1
B.2
C.4
D.19
AnswerB

10 Gbps has a cost of 2 in the short method.

Why this answer

Using the short path cost method (default), the cost for 10 Gbps is 2.

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55
MCQhard

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
B.12
C.16
D.20
AnswerB

Correct. The root path cost is 12, as shown in the Root ID section.

Why this answer

The root path cost is the cost of the path from this switch to the root bridge. It is shown in the Root ID section as 'Cost 12'. This is the cumulative cost via the root port (Gi0/2, which has a cost of 12).

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56
Drag & Dropmedium

Drag and drop the steps of Rapid PVST+ topology change notification process into the correct order, from first to last.

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

Why this order

In Rapid PVST+, a topology change is triggered when a non-edge port transitions to forwarding. The switch then sets the proposal bit on its designated ports, sends a proposal message, and expects an agreement from the downstream switch. After receiving the agreement, the port moves to forwarding and the switch propagates the change by setting the TC flag in BPDUs sent on all designated ports.

This ensures rapid convergence.

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57
Drag & Dropmedium

Drag and drop the steps of STP root bridge election and port state transitions into the correct order, from first to last.

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

Why this order

STP first elects a root bridge based on lowest bridge ID. Then each non-root bridge selects one root port (lowest path cost to root). Next, each segment elects a designated port (lowest root path cost, then lowest bridge ID).

All other ports become alternate (blocking). Finally, ports transition through blocking, listening, learning, and forwarding states.

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58
Drag & Dropmedium

Drag and drop the steps of STP portfast and BPDU guard configuration into the correct order, from first to last.

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

Why this order

PortFast is enabled globally or per interface to bypass listening/learning. BPDU guard is then configured to disable the port if a BPDU is received. The configuration is applied to the interface, and the port transitions to forwarding immediately.

Finally, errdisable recovery can be set.

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