JN0-106 Junos OS Fundamentals Practice Question
A junior engineer is troubleshooting connectivity issues and wants to trace the path packets take to a remote destination. Which Junos command should be used?
⚠ Common exam trap
A common mix-up: candidates confuse 'ping' (which tests reachability) with 'traceroute' (which traces the path), leading them to select Option D when the question explicitly asks for path tracing rather than simple connectivity testing.
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
✓
traceroute
The 'traceroute' command in Junos is specifically designed to trace the path packets take to a remote destination by sending UDP probes with increasing TTL values and analyzing ICMP Time Exceeded messages from intermediate routers. This directly addresses the junior engineer's need to map the Layer 3 path and identify where connectivity failures occur.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
monitor traffic
Why it's wrong here
monitor traffic captures and decodes packets that traverse a specific interface on the local device, similar to tcpdump, using filters to narrow the capture. It is a passive troubleshooting tool that does not generate probe packets, nor does it follow a packet's journey beyond the local segment. Consequently, it cannot reveal the forward path across multiple routers, making it unsuitable for path tracing.
- ✗
show route
Why it's wrong here
show route displays the routing table on a single Junos device, including prefixes, active routes, next hops, and protocol preferences. While it tells you where the router would forward a packet based on its local forwarding table, it gives no information about how those packets are actually processed by downstream routers. It is a snapshot of local routing state, not a measurement of the end-to-end path.
- ✓
traceroute
Why this is correct
traceroute is the correct tool because it actively probes the network path by sending packets with incrementally increasing TTL values, then collects the ICMP TTL-exceeded messages sent back by each router in turn. This reveals the sequence of IP addresses of every hop along the route to the destination, along with round-trip times for each hop, thus mapping the actual forwarding path hop by hop.
- ✗
ping
Why it's wrong here
ping sends ICMP Echo Requests to a destination and waits for ICMP Echo Replies to verify reachability and measure round-trip time. It is a valuable connectivity check, but it only gives an end-to-end up/down result: the reply comes from the final destination, not from intermediate routers, so the path taken is completely hidden. No per-hop information appears, making it useless for path tracing.
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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.