JNCIP-ENT IP Multicast Practice Question
In an enterprise network running PIM sparse-mode, an engineer notices that multicast traffic is switched from the shared tree (*,G) to the source-specific tree (S,G) prematurely, causing micro-bursts on core links. Which command disables this automatic switchover behavior on a Junos router?
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, last-hop routers switch from (*,G) to (S,G) upon receiving the first packet from source S. To prevent this, the 'spt-threshold infinity' command is configured under [edit 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-mode disable
Why it's wrong here
This path does not exist in Junos.
- ✗
set protocols pim disable-spt-switchover
Why it's wrong here
This is not a valid Junos configuration statement.
- ✗
set protocols igmp spt-threshold 0
Why it's wrong here
SPT threshold configuration belongs to PIM, not IGMP.
- ✓
set protocols pim spt-threshold infinity
Why this is correct
Setting the SPT threshold to infinity prevents the last-hop router from switching to the source-specific tree, keeping it on the shared tree.
About these practice questions
This JNCIP-ENT question is part of Courseiva's 336-question bank — original exam-style content with full explanations and wrong-answer analysis, never real exam questions or exam dumps. 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.