Hidden Static Route: Troubleshooting Next-Hop Issues
You are a network engineer for a company that uses two Juniper routers, R1 and R2, connected via an Ethernet link. R1 and R2 are running OSPF in the same area, and R2 also has an eBGP session with a service provider to reach the internet. On R1, you have configured a static route to the subnet 172.16.10.0/24 with a next-hop of 192.168.1.2, which is the IP address of R2's interface facing R1. You have verified that the static route is configured correctly in the configuration, but traffic from R1 to 172.16.10.0/24 is not being forwarded. You check the routing table on R1 and see that the static route is present but marked as 'hidden'. You also notice that R1 has an OSPF-learned route to 192.168.1.0/30 (the link between R1 and R2) with a cost of 1. What is the most appropriate next troubleshooting step?
Quick Answer
The answer is to check if the next-hop IP 192.168.1.2 is reachable via the directly connected interface. A static route becomes hidden in Junos when the next-hop is not considered reachable at the IP level, even if a routing protocol like OSPF knows about the subnet containing that next-hop. The router performs a reachability check on the specific next-hop address, not just the prefix, so if the directly connected interface is down, an ARP entry is missing, or a firewall filter blocks traffic, the route will be hidden. On the JNCIA-Junos exam, this concept tests your understanding of how Junos validates static route next-hops before installing them in the forwarding table, a common trap where students assume OSPF knowledge of the subnet guarantees reachability. Remember the hidden route rule: the next-hop must be directly reachable via a connected interface, not just reachable through another route. A useful memory tip is “hidden means hop is homeless”—if the next-hop can’t ARP out its own interface, the route stays hidden.
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
✓
Check if the next-hop IP 192.168.1.2 is reachable via the directly connected interface.
A static route becomes hidden in Juniper's routing table when the next-hop is considered unreachable. Although R1 has an OSPF-learned route to the subnet 192.168.1.0/30, the router performs a recursive lookup to ensure the next-hop IP 192.168.1.2 is reachable via a directly connected interface or a valid route. In this case, the next-hop is directly connected, so the most likely cause is that the interface is down, or there is an ARP resolution issue, or a firewall filter blocking ARP. Option D directs you to check if the next-hop is reachable via the directly connected interface, which is the appropriate first troubleshooting step. Option A is incorrect because disabling eBGP on R2 does not affect R1's static route next-hop reachability. Option B is incorrect because lowering preference would not resolve a hidden route; hidden routes are not considered for forwarding regardless of preference. Option C is incorrect because making the route more specific does not address the reachability issue.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Disable the eBGP session on R2 to remove the BGP routes from the routing table.
Why it's wrong here
Incorrect: BGP routes on R2 do not affect R1's static route next-hop reachability; the issue is on R1.
- ✗
Increase the static route's preference to a lower value (e.g., 4).
Why it's wrong here
Incorrect: the default preference of 5 is already very low; a lower preference would not help because the route is hidden, not competing with another route.
- ✗
Configure a more specific static route to 172.16.10.0/24 with a mask of /25.
Why it's wrong here
Incorrect: a more specific route would still have the same next-hop and would also be hidden if the next-hop is unreachable.
- ✓
Check if the next-hop IP 192.168.1.2 is reachable via the directly connected interface.
Why this is correct
Correct: the next-hop unreachability is the most common cause of a hidden static route; verifying reachability (e.g., ping, ARP) will identify the issue.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
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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. An engineer configures a static route to 192.168.0.0/16 with next-hop 172.16.1.1. The static route appears as 'hidden' in the routing table. What is the most likely cause?
medium- A.The static route preference is set too high
- ✓ B.The next-hop address 172.16.1.1 is unreachable
- C.The static route has not been committed
- D.The static route is a discard route
Why B: In JUNOS, a static route with a next-hop that is not reachable (i.e., there is no active route to the next-hop) is automatically placed in a 'hidden' state. The most likely cause is that the next-hop 172.16.1.1 is unreachable.
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.