JNCIP-ENT Ethernet Switching And Spanning Tree Practice Question
An enterprise network engineer is designing a redundant Layer 2 topology with MSTP across Juniper EX switches. Two switches have identical bridge priorities and MAC addresses that result in a tie for regional root. How does MSTP deterministically break the tie to select the regional root bridge?
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
✓
The switch with the numerically lowest MAC address is selected as the root bridge.
Spanning tree tie-breaking checks the bridge priority first, and if tied, compares the lowest MAC address of the switches.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The switch with the highest interface count operational status wins.
Why it's wrong here
Interface count does not influence root bridge selection.
- ✓
The switch with the numerically lowest MAC address is selected as the root bridge.
Why this is correct
When bridge priorities are tied, the switch with the lowest base MAC address wins the election.
- ✗
The switch with the higher serial number stored in EEPROM is chosen.
Why it's wrong here
Serial numbers are not part of the IEEE 802.1Q/802.1D bridge election algorithm.
- ✗
MSTP triggers a randomized tie-breaker algorithm using the system uptime.
Why it's wrong here
Root election is deterministic based on MAC address, never randomized.
Visual reference
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
About these practice questions
One of 332 original JNCIP-ENT practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not exam dumps or protected exam content. Learn why practice questions differ from exam dumps →
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 JNCIP-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 JNCIP-ENT exam.