STP Network Design and Implementation 3

Question 1

A network designer wants per-VLAN load balancing across redundant uplinks between access and distribution switches. Which STP variant best supports this design?

Accepted Answer

PVST+

Answer

PVST+ (Per-VLAN Spanning Tree Plus) runs a separate STP instance per VLAN, enabling different VLANs to use different root bridges and achieve uplink load balancing.

Question 2

In an MSTP design, what is the purpose of a Common and Internal Spanning Tree (CIST)?

Accepted Answer

It interconnects multiple MST regions and interoperates with 802.1D bridges

Answer

The CIST spans all switches in all MST regions and interoperates with 802.1D/PVST+ bridges, forming the backbone of MSTP topology.

Question 3

A network engineer notices that STP reconverges frequently due to topology changes triggered by end-device ports. Which feature directly reduces unnecessary TCN propagation?

Accepted Answer

PortFast on access ports

Answer

PortFast suppresses TCN BPDUs when ports transition, because end-device ports should not cause topology changes that flush MAC tables network-wide.

Question 4

In a network with dual-homed access switches, which STP port role describes the non-root, non-forwarding port that provides a redundant path to the root bridge?

Accepted Answer

Alternate port (RSTP)

Answer

In RSTP, the Alternate port is a non-forwarding port on a switch that has a better path to the root through a different bridge than its current root port.

Question 5

A data center design uses a collapsed core/distribution model with two core switches. To optimize STP, the engineer sets one core switch as the primary root and the other as the secondary root. What command sets the secondary root on Cisco IOS?

Accepted Answer

spanning-tree vlan X root secondary

Answer

The 'spanning-tree vlan X root secondary' command sets the bridge priority to 28672, making it the backup root if the primary root fails.

(STP) Spanning Tree Protocol Practice Test

(STP) Spanning Tree Protocol Practice Test

STP Network Design and Implementation 3