JNCIS-ENT IS IS Practice Question
During the examination of IS-IS packet captures on a multi-access LAN interface, an engineer notices a specific PDU type being transmitted periodically by the Designated Intermediate System (DIS) to maintain synchronized link-state databases. Which PDU type performs this function?
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
✓
Complete Sequence Numbers PDU (CSNP)
The Complete Sequence Numbers PDU (CSNP) is sent periodically by the DIS on a multi-access network to list all the link-state database entries present on the router, ensuring all routers maintain database synchronization.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Partial Sequence Numbers PDU (PSNP)
Why it's wrong here
PSNPs are used to acknowledge receipt of specific LSPs or to request missing LSPs, rather than periodic broadcast synchronization by the DIS.
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Complete Sequence Numbers PDU (CSNP)
Why this is correct
CSNPs contain the complete list of all LSPs in the router's database and are sent periodically by the DIS on broadcast networks.
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Intermediate System Hello (IIH)
Why it's wrong here
IIH packets are used for discovering neighbors and establishing/maintaining adjacencies, not database synchronization.
- ✗
Level 1 Link State PDU (LSP)
Why it's wrong here
LSPs contain link-state information and routing updates, not database summary listings sent periodically by the DIS.
Visual reference
About these practice questions
Courseiva writes every JNCIS-ENT question from scratch — 506 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 →
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.