STP Advanced Features and Variants 2

Question 1

What does MSTP (802.1s) allow that RSTP alone does not?

Accepted Answer

Multiple VLANs mapped to different spanning tree instances

Answer

MSTP allows multiple VLANs to be mapped to separate spanning tree instances, enabling load balancing across redundant links.

Question 2

In MSTP, what is the Common and Internal Spanning Tree (CIST)?

Accepted Answer

A spanning tree that interconnects all MST regions and the CST

Answer

The CIST is the single spanning tree that connects all MST regions together and interoperates with 802.1D/RSTP bridges.

Question 3

Which STP variant was specifically designed to reduce convergence time to under one second by using a proposal/agreement handshake?

Accepted Answer

RSTP (802.1w)

Answer

RSTP uses a proposal/agreement mechanism between adjacent switches to achieve near-instant convergence without relying on timers.

Question 4

What is the function of the MST region in MSTP?

Accepted Answer

A group of switches sharing the same MST configuration name, revision, and VLAN-to-instance mapping

Answer

Switches belong to the same MST region when they share identical configuration name, revision number, and VLAN-to-instance table.

Question 5

Which STP feature prevents a port from becoming a root port by ignoring received superior BPDUs?

Accepted Answer

Root Guard

Answer

Root Guard enforces the root bridge placement by placing a port into root-inconsistent state if a superior BPDU is received.

(STP) Spanning Tree Protocol Practice Test