Spanning Tree practice questions

A network engineer runs the following command on Switch SW1:

SW1# show interfaces trunk

Port Mode Encapsulation Status Native vlan Gi0/1 on 802.1q trunking 1 Gi0/2 on 802.1q trunking 1

Port Vlans allowed on trunk Gi0/1 1-1005 Gi0/2 1-1005

Port Vlans allowed and active in management domain Gi0/1 1,10,20 Gi0/2 1,10,20

Port Vlans in spanning tree forwarding state and not pruned Gi0/1 1,10,20 Gi0/2 1,10,20

Based on this output, what can be concluded?

Trap 1: The trunk is using ISL encapsulation.

The encapsulation is shown as 802.1q.

Trap 2: VLAN 1 is pruned from the trunk.

VLAN 1 is in the forwarding state, so it is not pruned.

Trap 3: Only VLANs 10 and 20 are forwarding traffic.

VLAN 1 is also forwarding.

A
VLANs 2-9 are allowed but not active on the trunk.
The 'allowed' list includes 1-1005, but only VLANs 1,10,20 are active; thus VLANs 2-9 are allowed but not active (not created in VLAN database).
B
The trunk is using ISL encapsulation.
Why wrong: The encapsulation is shown as 802.1q.
C
VLAN 1 is pruned from the trunk.
Why wrong: VLAN 1 is in the forwarding state, so it is not pruned.
D
Only VLANs 10 and 20 are forwarding traffic.
Why wrong: VLAN 1 is also forwarding.

Question 2hardmultiple choice

A global enterprise is transitioning from a traditional three-tier campus architecture to a software-defined access (SD-Access) fabric. Which architectural consideration is most critical for the underlay network?

Trap 1: Implement PIM-SM for multicast routing in the underlay.

Multicast is not required for the underlay; the overlay handles group communication.

Trap 2: Preserve existing VLANs across the fabric to minimize changes.

The underlay should be IP routed; VLANs are not used in the underlay.

Trap 3: Deploy VRF-lite on all edge nodes to isolate tenants.

VRF-lite is not a requirement; the overlay provides segmentation.

A
Configure a routed access layer with a link-state routing protocol (IS-IS or OSPF).
A routed underlay with IS-IS or OSPF is a key design requirement for SD-Access.
B
Implement PIM-SM for multicast routing in the underlay.
Why wrong: Multicast is not required for the underlay; the overlay handles group communication.
C
Preserve existing VLANs across the fabric to minimize changes.
Why wrong: The underlay should be IP routed; VLANs are not used in the underlay.
D
Deploy VRF-lite on all edge nodes to isolate tenants.
Why wrong: VRF-lite is not a requirement; the overlay provides segmentation.

Question 3easymulti select

Which THREE of the following are benefits of implementing a spine-leaf architecture in a data center?

Trap 1: Reduces the amount of cabling required.

Incorrect: Spine-leaf actually increases cabling due to full mesh connections between leaf and spine switches.

Trap 2: Eliminates the need for firewall appliances.

Incorrect: Firewall appliances are still necessary for enforcing security policies in the data center.

A
Provides predictable latency for east-west traffic.
Correct: Spine-leaf provides predictable latency because every leaf-to-spine hop is consistent.
B
Eliminates the need for spanning-tree protocol.
Correct: Spine-leaf eliminates the need for Spanning Tree Protocol by using Layer 3 routing to prevent loops.
C
Reduces the amount of cabling required.
Why wrong: Incorrect: Spine-leaf actually increases cabling due to full mesh connections between leaf and spine switches.
D
Simplifies scalability by adding leaf switches without redesign.
Correct: Adding a leaf switch is straightforward as it only requires connections to all spine switches.
E
Eliminates the need for firewall appliances.
Why wrong: Incorrect: Firewall appliances are still necessary for enforcing security policies in the data center.

Question 4mediummultiple choice

spanning-tree mode rapid-pvst

What is the effect of this global configuration command?

Trap 1: The switch will use MSTP for all VLANs.

MSTP is configured with 'spanning-tree mode mst'.

Trap 2: The switch will use classic STP for all VLANs.

Classic STP is 'spanning-tree mode pvst'.

Trap 3: The switch will disable STP on all ports.

STP remains enabled; only the mode changes.

A
The switch will use Rapid PVST+ for all VLANs, providing faster convergence than classic STP.
Rapid PVST+ is the Cisco implementation of RSTP per VLAN.
B
The switch will use MSTP for all VLANs.
Why wrong: MSTP is configured with 'spanning-tree mode mst'.
C
The switch will use classic STP for all VLANs.
Why wrong: Classic STP is 'spanning-tree mode pvst'.
D
The switch will disable STP on all ports.
Why wrong: STP remains enabled; only the mode changes.

Question 5mediummultiple choice

Examine the following partial Cisco IOS-XE configuration:

interface GigabitEthernet0/1
 switchport mode access
 switchport access vlan 10
 ip access-group ACL_IN in
 spanning-tree portfast

What is the effect of this configuration?

Trap 1: The port will become a trunk port and participate in VLAN trunking.

The port is configured as an access port, not a trunk.

Trap 2: The port will use Rapid PVST+ and immediately forward after a link…

PortFast does not change the STP mode; it only affects initial convergence.

Trap 3: The port will block all inbound traffic due to the ACL.

The ACL is applied inbound but does not block all traffic; it filters based on the ACL entries.

A
The port will immediately transition to forwarding state, reducing STP convergence time for end hosts.
spanning-tree portfast on an access port causes immediate forwarding, as intended for host ports.
B
The port will become a trunk port and participate in VLAN trunking.
Why wrong: The port is configured as an access port, not a trunk.
C
The port will use Rapid PVST+ and immediately forward after a link failure.
Why wrong: PortFast does not change the STP mode; it only affects initial convergence.
D
The port will block all inbound traffic due to the ACL.
Why wrong: The ACL is applied inbound but does not block all traffic; it filters based on the ACL entries.

Question 6mediumdrag order

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

A
Enter MST configuration mode
Enter MST configuration mode, which is the second step after enabling MST globally.
B
Assign region name
Assign the region name within MST configuration mode, the third step.
C
Set revision number
Set the revision number, typically the fourth step after naming the region.
D
Map VLANs to MST instance
Map VLANs to MST instances, the final configuration step before exiting MST configuration mode.
E
Set spanning-tree mode mst globally
Set spanning-tree mode mst globally – this must be done first to enable MSTP on the switch.

Question 7mediummultiple choice

Given the following configuration snippet on a Cisco IOS-XE switch:

interface GigabitEthernet1/0/1
 switchport mode access
 switchport access vlan 10
 spanning-tree portfast

monitor session 1 source interface GigabitEthernet1/0/1 both monitor session 1 destination interface GigabitEthernet1/0/2

What is the effect of this configuration?

Trap 1: Only traffic entering GigabitEthernet1/0/1 is copied to…

The 'both' keyword copies both directions, not just ingress.

Trap 2: Traffic on GigabitEthernet1/0/2 is replicated to…

The monitor session defines source and destination; traffic flows from source to destination, not the reverse.

Trap 3: The configuration is invalid because the destination port must be…

A SPAN destination port can be an access port; trunk mode is not required.

A
All traffic entering and leaving GigabitEthernet1/0/1 is copied to GigabitEthernet1/0/2.
The 'both' keyword copies both ingress and egress traffic from the source interface to the destination.
B
Only traffic entering GigabitEthernet1/0/1 is copied to GigabitEthernet1/0/2.
Why wrong: The 'both' keyword copies both directions, not just ingress.
C
Traffic on GigabitEthernet1/0/2 is replicated to GigabitEthernet1/0/1.
Why wrong: The monitor session defines source and destination; traffic flows from source to destination, not the reverse.
D
The configuration is invalid because the destination port must be in trunk mode.
Why wrong: A SPAN destination port can be an access port; trunk mode is not required.

Question 8mediumdrag order

Drag and drop the steps for configuring STP root guard and loop guard and the resulting port behavior 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

Question 9easymultiple choice

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?

Trap 1: GigabitEthernet0/2

Incorrect. Gi0/2 is a designated port (Desg).

Trap 2: GigabitEthernet0/3

Incorrect. Gi0/3 is a designated port (Desg).

Trap 3: There is no root port because SW4 is the root bridge.

Incorrect. SW4 is not the root bridge; the root bridge has a different MAC address.

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.