hardMultiple Select
350-401 Practice Question: Which three statements about Multiple Spanning…
Which three statements about Multiple Spanning Tree Protocol (MSTP) are true? (Choose three.)
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
MSTP allows multiple VLANs to be grouped into a single spanning-tree instance, reducing CPU and memory usage.
MSTP (IEEE 802.1s) allows multiple VLANs to be mapped to a single spanning-tree instance (MST instance), reducing the number of STP instances needed. It uses an Internal Spanning Tree (IST) instance (instance 0) that always runs and carries BPDUs for the region. Switches in the same MST region must have identical VLAN-to-instance mappings, revision number, and region name. MSTP interoperates with Rapid PVST+ at region boundaries by using PVST simulation mode. MSTP does not require a separate root bridge for each VLAN; instead, each MST instance has its own root bridge.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
MSTP allows multiple VLANs to be grouped into a single spanning-tree instance, reducing CPU and memory usage.
Why this is correct
MSTP maps many VLANs onto a shared instance, so a single spanning-tree computation serves them all. That collapses per-VLAN STP processing into fewer instances, directly cutting CPU and memory load compared with PVST+ running one tree per VLAN.
- ✓
In MSTP, the Internal Spanning Tree (IST) instance is instance 0 and is always present in every MST region.
Why this is correct
Instance 0 is the IST, the common internal spanning tree that every MSTP switch runs regardless of region. It carries the CIST and provides backward compatibility, so it always exists and cannot be disabled or remapped to another instance.
- ✓
MSTP requires that all switches in the same MST region have the same VLAN-to-instance mapping, revision number, and region name.
Why this is correct
Region membership is defined by three matching attributes: region name, revision number and identical VLAN-to-instance mapping. Any mismatch places a switch in a different region, so consistent configuration across all member switches is mandatory for the region to form correctly.
- ✗
MSTP automatically load-balances traffic across all available uplinks without any configuration.
Why it's wrong here
MSTP load-balances only when the engineer manually maps VLANs to instances and assigns different roots per instance; with default mapping all VLANs share one topology. It is tempting because that manual VLAN-to-instance mapping is precisely the mechanism MSTP provides for load balancing.
- ✗
MSTP requires a separate root bridge to be elected for each VLAN in the network.
Why it's wrong here
MSTP maps multiple VLANs onto a single spanning-tree instance, so one root bridge serves all VLANs in that instance rather than one per VLAN. It is tempting because per-VLAN root election is exactly what PVST+ and Rapid PVST+ require, making this the correct statement for those protocols.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.