JNCIS-ENT Spanning Tree Practice Question
Which TWO statements are correct regarding the operation of MSTP instance 0 (CIST)? (Choose two.)
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
✓
It handles any VLANs that are not explicitly mapped to another user-defined MST instance.
Instance 0 in MSTP is known as the Common and Internal Spanning Tree (CIST), and it manages unmapped VLANs while maintaining backward compatibility with legacy STP/RSTP regions.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
It handles any VLANs that are not explicitly mapped to another user-defined MST instance.
Why this is correct
Unmapped VLANs automatically default to Instance 0.
- ✗
It operates independently without any interaction with external RSTP switches.
Why it's wrong here
Instance 0 communicates directly with external RSTP and STP networks at region boundaries.
- ✗
It is limited strictly to a maximum hop count of 1.
Why it's wrong here
Hop counts follow regional configurations, not a fixed limit of 1.
- ✓
It acts as the Common and Internal Spanning Tree (CIST).
Why this is correct
Instance 0 is always the CIST, managing overall regional connectivity.
- ✗
It prohibits the use of root protection on instance 0 ports.
Why it's wrong here
Root protection can be applied across instance ports.
Visual reference
About these practice questions
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed August 2026 · checked against the official Juniper Networks exam blueprint
This JNCIS-ENT practice question is part of Courseiva's free Juniper Networks 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 JNCIS-ENT exam.