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
Higher preference does not hide a route; it makes that route preferred and installed, while the less-preferred one becomes hidden. The exhibit shows the route itself hidden, so preference is not the cause. Preference is used to select between competing routes, not to suppress a single one.
- ✗
The BGP session to 10.0.0.2 is down.
Why it's wrong here
A down BGP session would remove all routes learned from that peer, not leave a single prefix hidden. Session state is verified separately in the exhibit. This would be the cause if the neighbour showed Idle or Active and all its prefixes vanished, which is not the scenario here.
- ✗
The prefix 10.1.1.0/24 is filtered by an import policy.
Why it's wrong here
An import policy filtering the prefix would prevent the route entering the RIB at all, so it would not appear as hidden; hidden routes are those rejected during best-path selection. Import policies are used to control which received routes are accepted, which is a different mechanism from the hidden state shown.
- ✓
The next-hop 192.168.100.1 is not reachable via any active route.
Why this is correct
An unreachable next-hop prevents BGP from validating the path, so the route stays hidden rather than becoming active. Junos requires the next-hop to resolve through an active route in the routing table; with no such route, the prefix fails next-hop resolution and is withheld from the forwarding table.
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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.