JNCIP-ENT IP Multicast Practice Question
An engineer is troubleshooting PIM Sparse-Mode on a Junos device and notices that source traffic is not switching from the shared tree (*,G) to the shortest path tree (S,G) at the Last-Hop Router. Which configuration statement on the Junos routing instance allows adjusting the threshold for this switchover behavior?
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
✓
set protocols pim spt-threshold infinity
By default, Junos switches from the (*,G) shared tree to the (S,G) shortest path tree immediately upon receiving the first data packet from a source. To prevent this or adjust the behavior, operators use the 'spt-threshold' statement under protocols pim.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
set routing-options multicast spt-lifetime 0
Why it's wrong here
SPT lifetime is not a valid Junos routing-options hierarchy statement for multicast.
- ✗
set protocols pim switchover-delay 0
Why it's wrong here
There is no switchover-delay statement in Junos PIM configuration.
- ✗
set protocols igmp ssm-mapping
Why it's wrong here
SSM mapping is used for translating (*,G) joins into Source-Specific Multicast joins for receivers running IGMPv2, not for SPT switchover thresholds.
- ✓
set protocols pim spt-threshold infinity
Why this is correct
Setting the spt-threshold to infinity forces the router to remain on the rendezvous point shared tree (*,G) indefinitely.
About these practice questions
Courseiva writes every JNCIP-ENT question from scratch — 336 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
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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.