Quick Answer
The answer is the Junos `traceroute` command, which is the correct tool for path discovery when you need to see the exact route packets take to a remote host. This command works by sending UDP probes with incrementing Time-To-Live (TTL) values; each router along the path decrements the TTL, and when it reaches zero, the router sends back an ICMP Time Exceeded message, revealing that hop’s IP address. On the JNCIA-Junos exam, this question tests your understanding of operational monitoring commands, often contrasting `traceroute` with `ping` (which only tests reachability, not the path). A common trap is confusing `traceroute` with `traceroute monitor` or assuming `ping` provides hop-by-hop details—it does not. Remember the memory tip: “Trace the TTL, map the hops” to recall that `traceroute` uses TTL expiration to discover each router along the path.
This JNCIA-JUNOS practice question tests your understanding of operational monitoring and maintenance. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
A technician is troubleshooting a connectivity issue and needs to see the path packets take to a remote host. Which Junos command is appropriate?
traceroute
Traces the path to the remote host.
monitor interface
Why wrong: Monitors interface traffic, not path.
ping
Why wrong: Tests reachability, does not show path.
show route
Why wrong: Shows routing table, not actual path.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
traceroute
The `traceroute` command in Junos is the correct tool for tracing the path packets take to a remote host. It sends UDP probes with increasing TTL values and listens for ICMP Time Exceeded messages from intermediate routers, revealing each hop along the route. This directly matches the technician's need to see the path packets take.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
traceroute
Why this is correct
Traces the path to the remote host.
Related concept
Read the scenario before looking for a memorised answer.
monitor interface
Why it's wrong here
Monitors interface traffic, not path.
ping
Why it's wrong here
Tests reachability, does not show path.
show route
Why it's wrong here
Shows routing table, not actual path.
Common exam traps
The trap here is that candidates often confuse `ping` (which tests reachability) with `traceroute` (which shows the path), leading them to select ping when the question explicitly asks for the path packets take.
Trap categories for this question
Command / output trap
Tests reachability, does not show path.
Detailed technical explanation
Junos `traceroute` uses UDP packets to high-numbered ports (default 33434-33534) by default, differing from the ICMP Echo probes used by some other implementations. It increments the TTL from 1 upwards, and each router that decrements the TTL to 0 sends an ICMP Time Exceeded (Type 11, Code 0) message back to the source. The command can also be modified with options like `-I` to use ICMP Echo probes or `-T` for TCP SYN probes, which may bypass firewalls that block UDP.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
What to study next
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Operational Monitoring and Maintenance — study guide chapter
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FAQ
Operational Monitoring and Maintenance — This question tests Operational Monitoring and Maintenance — Read the scenario before looking for a memorised answer..
The correct answer is: traceroute — The `traceroute` command in Junos is the correct tool for tracing the path packets take to a remote host. It sends UDP probes with increasing TTL values and listens for ICMP Time Exceeded messages from intermediate routers, revealing each hop along the route. This directly matches the technician's need to see the path packets take.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This JNCIA-JUNOS 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 JNCIA-JUNOS exam.
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