JNCIS-ENT IS IS Practice Question
During an audit of an IS-IS routing network, an engineer examines the Type-Length-Value (TLV) structures used in IS-IS PDUs. Which TLV is specifically responsible for carrying IPv4 internal and external reachability information when using wide metrics?
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
✓
TLV 135
In IS-IS, TLV 135 (Extended IP Reachability) is used to carry IPv4 prefixes when wide metrics are enabled, replacing the older narrow metric TLV 128.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
TLV 135
Why this is correct
TLV 135 carries extended IP reachability information, supporting wide metrics and sub-TLV attributes.
- ✗
TLV 128
Why it's wrong here
TLV 128 carries IP information using narrow metrics (IP Internal Reachability Information).
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TLV 1
Why it's wrong here
TLV 1 specifies the Area Addresses supported by the router.
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TLV 2
Why it's wrong here
TLV 2 carries Intermediate System neighbors (IS Neighbors) for narrow metrics.
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.