JN0-106 Routing Fundamentals Practice Question
A route learned via BGP appears as 'hidden' in the routing table. Which condition is most likely the cause?
⚠ Common exam trap
Many exam-takers confuse 'hidden' with 'rejected by policy' or 'less preferred by AS path', but JUNOS specifically uses 'hidden' to indicate a next-hop unreachability issue, not a policy or selection problem.
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 BGP next-hop is unreachable
In JUNOS, a BGP route is marked as 'hidden' in the routing table when the next-hop address is not reachable via any active route in the inet.0 table. This is a fundamental BGP path selection prerequisite: the next-hop must be resolvable (typically via an IGP or static route) for the route to be considered active and installed.
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 BGP route has a higher AS path length than another route
Why it's wrong here
Having a higher AS path length than another route does not make a BGP route hidden; the route is still valid and will be installed if it is the best path. AS path length is a tie-breaker in the BGP path selection algorithm, and a longer path only reduces the route's preference relative to other routes. A hidden route is one that fails a validity check, such as an unreachable next-hop, not one that is less preferred. Therefore, this option is incorrect because it conflates path selection preference with route validity.
- ✗
The BGP route has been rejected by a policy
Why it's wrong here
A BGP route rejected by an import policy is not placed in the routing table at all, so it would never appear as hidden. The rejection occurs during policy evaluation, before the route is considered for installation, and the route is simply discarded from the RIB. Hidden routes are those that pass policy but fail other criteria, such as having an unresolved next-hop. Thus, this option is wrong because a policy-rejected route is absent, not hidden.
- ✓
The BGP next-hop is unreachable
Why this is correct
For a BGP route to be active, its next-hop must be reachable via an existing route in the inet.0 routing table; if not, the BGP route is considered invalid and is placed in a hidden state. This is a fundamental BGP rule: the protocol relies on resolving next-hop addresses through IGP or static routes before installing the route. If the next-hop is unreachable, the route remains hidden in the BGP RIB and is not used for forwarding. This is the correct answer because it directly explains the hidden state.
- ✗
The BGP local preference is too high
Why it's wrong here
Local preference is a BGP attribute used to select the best route for outbound traffic; a higher value makes a route more preferred, never less favored or invalid. An excessively high local preference simply means that route will be chosen over others with lower values, but it does not affect the route's ability to be installed. Hidden routes are unrelated to preference, as they are caused by validity failures like an unresolvable next-hop. Therefore, this option is incorrect because high local preference cannot cause a route to become hidden.
Visual reference
Go deeper
Related to this question
About these practice questions
One of 326 original JN0-106 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 by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This JN0-106 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 JN0-106 exam.