BGP Hidden Route: Why Next-Hop Unreachable Causes Hiding | JNCIA-Junos
Exhibit
user@router> show route protocol bgp 10.1.1.0/24
inet.0: 10 destinations, 12 routes (8 active, 2 holddown, 2 hidden)
+ = Active Route, - = Last Active, * = Both
10.1.1.0/24 [BGP/170] 00:01:23, localpref 100, from 10.0.0.2
Next hop: 192.168.100.1 via ge-0/0/0.0
(hidden: next hop unreachable)Refer to the exhibit. What is the most likely cause of this BGP route being hidden?
Quick Answer
The answer is that the BGP route is hidden because the next-hop 192.168.100.1 is not reachable via any active route. This occurs because Junos performs a recursive route lookup for the BGP next-hop address in the inet.0 routing table; if no valid, active route exists to that IP, the BGP route is suppressed and marked as hidden with the reason "next hop unreachable." On the JNCIA-Junos exam, this concept tests your understanding of BGP route selection and the importance of an IGP or static route covering the next-hop, often appearing in troubleshooting exhibits where a route is present in the BGP table but absent from the forwarding table. A common trap is assuming the route is hidden due to a prefix-list or AS-path issue, but the exhibit’s explicit "next hop unreachable" reason points directly to a missing route for 192.168.100.1. Memory tip: think of BGP as a passenger that needs a working road (the IGP route) to reach its destination—no road, no ride.
⚠ Common exam trap
Watch out — candidates often confuse a hidden route with a route that is filtered by policy or has a higher preference, but JUNOS specifically uses the 'hidden' flag to indicate next-hop unreachability, not policy rejection or preference comparison.
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 next-hop 192.168.100.1 is not reachable via any active route.
In JUNOS, a BGP route is hidden when the next-hop address is not reachable via any active route in the routing table. The show route protocol bgp command displays the route as hidden if the next-hop 192.168.100.1 is not resolvable, because BGP requires a valid IGP or static route to the next-hop for the route to be considered active and installed in the forwarding table.
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 route has a higher preference than another route.
Why it's wrong here
The hidden reason explicitly states next-hop unreachable, not preference conflict.
- ✗
The BGP session to 10.0.0.2 is down.
Why it's wrong here
If the session were down, the route would not appear at all.
- ✗
The prefix 10.1.1.0/24 is filtered by an import policy.
Why it's wrong here
If filtered, the route would not appear in the routing table at all, not as hidden.
- ✓
The next-hop 192.168.100.1 is not reachable via any active route.
Why this is correct
The reason given is 'next hop unreachable', so the next-hop is not reachable.
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Same concept, more angles
1 more way this is tested on JN0-106
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A route learned via BGP appears as 'hidden' in the routing table. Which condition is most likely the cause?
hard- A.The BGP route has a higher AS path length than another route
- B.The BGP route has been rejected by a policy
- ✓ C.The BGP next-hop is unreachable
- D.The BGP local preference is too high
Why C: 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.
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.