JN0-106 Operational Monitoring and Maintenance Practice Question
A network engineer notices that traffic to a critical server is being dropped intermittently. The server is reachable via a static route on the Juniper router. The engineer checks the routing table and sees the route is present. Which operational command should the engineer use next to isolate the issue?
⚠ Common exam trap
Many candidates assume a route present in the routing table guarantees it is being used for forwarding, but Junos separates control plane (RIB) from forwarding plane (FIB), so the FIB must be checked separately to identify programming failures.
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
✓
show route forwarding-table destination 10.0.0.1
The `show route forwarding-table destination 10.0.0.1` command displays the actual forwarding entry in the kernel's forwarding table (FIB). Even if the route is present in the routing table (RIB), a mismatch between the RIB and FIB can cause traffic drops. This command directly verifies whether the route has been installed into the forwarding table, isolating the issue to a possible hardware or kernel programming failure.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
show interfaces terse
Why it's wrong here
show interfaces terse displays a compact summary of physical and logical interface status, including administrative and operational states and IP addresses. It offers no visibility into the Packet Forwarding Engine's (PFE) forwarding decisions, next-hop resolution, or any packet drops for a specific destination. Since the problem is traffic not reaching a critical server, this command cannot reveal why forwarded packets are being dropped.
- ✗
show route 10.0.0.1
Why it's wrong here
show route 10.0.0.1 queries the Routing Engine's inet.0 routing table (RIB), confirming that the route is present in the control plane. However, the very issue is that traffic is not reaching the server despite the route existing, meaning the control plane has the route but the forwarding plane may not. This command does not inspect the kernel forwarding state or the PFE's forwarding table, so it cannot diagnose a missing or stale FIB entry or an incorrect next hop that causes drops.
- ✗
show arp
Why it's wrong here
show arp displays the Address Resolution Protocol cache, mapping IP addresses to MAC addresses for directly connected neighbors. It would be relevant only if the critical server were on a local subnet and you suspected an L2 adjacency problem. In this scenario, the traffic forwarding is failing despite the route present, so ARP is not the right diagnostic; it cannot reveal forwarding drops, next-hop issues, or FIB inconsistencies that occur in the PFE.
- ✓
show route forwarding-table destination 10.0.0.1
Why this is correct
show route forwarding-table destination 10.0.0.1 is the correct command because it queries the Packet Forwarding Engine's forwarding table (FIB) for the specific destination. While show route only shows the RIB in the Routing Engine, this command reveals the actual entry the PFE uses to forward packets, including the resolved next hop and output interface. If the route exists in the RIB but traffic is dropped, this command can expose a missing or stale forwarding entry, an incorrect next hop, or a drop caused by a firewall filter applied in the forwarding path.
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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.