JN0-106 Routing Fundamentals Practice Question
An administrator suspects that routing protocol updates are being sent to an incorrect next-hop. Which command can be used to capture and analyze the routing protocol packets on an interface?
⚠ Common exam trap
Many candidates confuse log-based troubleshooting (Option A) with live packet capture, or they mistakenly think that viewing the forwarding table (Option B) or neighbor details (Option C) reveals the actual packet contents being transmitted, when in fact only a packet capture tool like 'monitor traffic' can show the raw protocol updates.
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
✓
monitor traffic interface ge-0/0/0.0
The 'monitor traffic interface' command in Junos captures live packets on a specified interface, allowing the administrator to inspect routing protocol packets (e.g., OSPF, BGP) in real time. This is the only option that directly captures and displays packet-level data to verify the next-hop IP address in routing protocol updates.
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 log messages | match ospf
Why it's wrong here
This command only displays OSPF-related log messages that have already been written to the system log buffer, such as neighbor up/down events or LSA flooding occurrences. It does not show the actual OSPF hello, database descriptor, or link-state update packets traversing the interface in real time. To correlate routing protocol updates with packet contents, you need a live packet capture, not a historical log view.
- ✗
show route forwarding-table
Why it's wrong here
This command displays the contents of the Forwarding Information Base (FIB), which contains the routes and next-hop information that the kernel uses to actually forward packets. While it allows you to see the result of routing updates—for example, whether an OSPF-learned route was installed—it does not show the OSPF protocol packets themselves. Therefore, it cannot be used to inspect routing protocol updates on the wire, such as hello or database descriptor packets.
- ✗
show ospf neighbor detail
Why it's wrong here
This command provides a detailed view of OSPF neighbor adjacency state, timers, interface addresses, and the DR/BDR election process, but it only reports the current state as seen by the OSPF process. It does not capture or display the actual OSPF packets exchanged on the interface, so you cannot see the specific update or acknowledgment packets that may be causing the problem. For that level of detail, a packet sniffing command is required.
- ✓
monitor traffic interface ge-0/0/0.0
Why this is correct
This command triggers a live packet capture on the specified interface, displaying all traffic that enters or exits the interface in real time, much like tcpdump. It can be narrowed down with a 'matching' statement, but even without one, it will show OSPF packets (protocol 89) if present, revealing hello, DD, LSR, LSU, and LSAck packets. This makes it the correct tool for an administrator who suspects routing protocol updates are being misconfigured or lost, because it gives direct evidence of what is actually sent and received.
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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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.