Quick Answer
The answer is the monitor traffic interface ge-0/0/0.0 command. This command is correct because it performs a real-time packet capture directly on the specified interface, allowing you to inspect the actual contents of routing protocol packets such as OSPF or BGP updates to verify the next-hop address. On the JNCIA-Junos exam, this question tests your ability to distinguish between operational commands used for troubleshooting routing issues versus commands that display static tables or logs. A common trap is confusing monitor traffic with show route (which displays the forwarding table) or show log (which shows historical events but not live packet data). Remember that monitor traffic is Junos’s equivalent of tcpdump, giving you a live packet-level view. A helpful memory tip: “Monitor moves packets, show just shows static data”—if you need to see the actual packets flying by, think of the word “monitor” as your packet-capture trigger.
This JNCIA-JUNOS practice question tests your understanding of routing fundamentals. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "which command"
Why it matters: Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
show log messages | match ospf
Why wrong: This displays log entries, not live packet capture.
show route forwarding-table
Why wrong: This shows the forwarding entries, not packet captures.
show ospf neighbor detail
Why wrong: This shows OSPF neighbor status, not packet contents.
monitor traffic interface ge-0/0/0.0
This command captures all packets on the interface for analysis.
Answer choices
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' command captures packets on an interface and allows analysis of routing updates. Option D is correct. Option A shows the forwarding table, not captures. Option B shows log files but not real-time capture. Option C shows OSPF neighbor state, not packet contents.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
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 displays log entries, not live packet capture.
show route forwarding-table
Why it's wrong here
This shows the forwarding entries, not packet captures.
show ospf neighbor detail
Why it's wrong here
This shows OSPF neighbor status, not packet contents.
monitor traffic interface ge-0/0/0.0
Why this is correct
This command captures all packets on the interface for analysis.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
OSPF neighbours must agree on key parameters.
Common exam traps
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Trap categories for this question
Command / output trap
This shows the forwarding entries, not packet captures.
Detailed technical explanation
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related JNCIA-JUNOS OSPF questions on adjacency and route selection.
Routing Fundamentals — study guide chapter
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FAQ
Routing Fundamentals — This question tests Routing Fundamentals — OSPF neighbours must agree on key parameters..
The correct answer is: monitor traffic interface ge-0/0/0.0 — The 'monitor traffic' command captures packets on an interface and allows analysis of routing updates. Option D is correct. Option A shows the forwarding table, not captures. Option B shows log files but not real-time capture. Option C shows OSPF neighbor state, not packet contents.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related JNCIA-JUNOS OSPF questions on adjacency and route selection.
Yes — watch for: "which command". Tests specific CLI syntax. Recall the exact command and its required context — near-synonyms and partial matches are common distractors.
OSPF neighbours must agree on key parameters.
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Last reviewed: Jun 24, 2026
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