STP Advanced STP 2

Question 1

What is Per-VLAN Spanning Tree (PVST+)?

Accepted Answer

Cisco protocol running a separate STP instance for each VLAN, allowing per-VLAN load balancing

Answer

PVST+ creates a unique spanning tree for each VLAN, enabling different root bridges and traffic paths per VLAN.

Question 2

What is root guard in STP?

Accepted Answer

A feature preventing a port from becoming a root port, protecting the root bridge election

Answer

Root guard ensures that specific ports cannot be elected as root ports, preventing external switches from becoming the root bridge.

Question 3

What is loop guard in STP?

Accepted Answer

A feature that prevents alternate or root ports from transitioning to designated/forwarding if BPDUs stop arriving

Answer

Loop guard prevents a port from erroneously moving to forwarding state when it stops receiving BPDUs, which could create a loop.

Question 4

How does STP handle unidirectional link failures?

Accepted Answer

Through features like UDLD (Unidirectional Link Detection) and loop guard

Answer

Unidirectional link failures are particularly dangerous for STP because one switch may not receive BPDUs while the other sends them normally.

Question 5

What is the recommended practice for STP root bridge placement?

Accepted Answer

Place the root bridge on a high-performance core switch central to the network

Answer

The root bridge should be a centrally located, high-performance switch to optimize traffic paths and minimize spanning tree depth.

(STP) Spanning Tree Protocol Practice Test