STP Advanced Features and Variants

Question 1

What is the primary benefit of using Rapid Spanning Tree Protocol (RSTP) over the traditional Spanning Tree Protocol (STP)?

Accepted Answer

It provides faster convergence

Answer

RSTP (Rapid Spanning Tree Protocol) was developed to overcome the slow convergence issues of traditional STP. It achieves faster convergence by introducing new port roles (Alternate, Backup) and states, and by using a more efficient negotiation process between switches. This allows for quicker recovery from link failures and topology changes, minimizing network downtime and improving network stability.

Question 2

What is the function of BPDU Guard in STP?

Accepted Answer

To prevent BPDUs from being sent on edge ports

Answer

BPDU Guard is an STP enhancement designed to protect the STP topology from unauthorized or malicious devices. When enabled on an access port (an edge port connected to an end device), BPDU Guard immediately puts the port into an error-disabled state if it receives a BPDU. This prevents rogue switches from interfering with the STP topology and causing network instability.

Question 3

What does the concept of "Bridge Assurance" in STP aim to accomplish?

Accepted Answer

To ensure that BPDUs are periodically sent on all ports to detect network changes

Answer

Bridge Assurance is an STP feature that enhances network reliability by ensuring bidirectional BPDU exchange on point-to-point links. It ensures that a switch port continuously receives BPDUs from its neighbor. If BPDUs stop arriving on a Bridge Assurance-enabled port, the port is transitioned to a blocking state, preventing potential loops caused by unidirectional link failures or misconfigurations.

Question 4

In Multiple Spanning Tree Protocol (MSTP), what is the primary advantage of mapping VLANs to MST instances?

Accepted Answer

It reduces the number of STP instances needed, improving scalability

Answer

MSTP (Multiple Spanning Tree Protocol) allows multiple VLANs to be mapped to a single Spanning Tree Instance (MST Instance). This significantly reduces the number of STP instances that need to run on a switch compared to PVST+, which runs a separate STP instance for every VLAN. By grouping VLANs, MSTP improves scalability and reduces resource consumption on switches, especially in large networks.

Question 5

What is the purpose of "Loop Guard" in STP?

Accepted Answer

To prevent alternate and backup ports from becoming designated ports due to network topology changes

Answer

Loop Guard is an STP feature that protects against potential loops caused by unidirectional link failures or misconfigurations. It monitors non-designated ports (Root, Alternate, Backup) that are supposed to be blocking. If a port in a blocking state stops receiving BPDUs, Loop Guard prevents it from transitioning to a forwarding state, thereby avoiding a potential loop in the network.

(STP) Spanning Tree Protocol Practice Test

(STP) Spanning Tree Protocol Practice Test

STP Advanced Features and Variants