This JNCIA-JUNOS practice question tests your understanding of junos os fundamentals. 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.
You are a network administrator for a large enterprise. You have a Juniper SRX firewall that is used as the primary internet gateway. Users are reporting that they are unable to access certain external websites. You check the device and find that the security policies appear correct, and the routing is in place. You suspect that the issue might be related to the DNS resolution. You want to verify that the device can resolve DNS names and that the DNS server configuration is correct. Which command should you use to test DNS resolution from the Juniper device?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
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 system connections
Why wrong: Shows active connections, not DNS resolution.
ping <external website FQDN>
Pinging a hostname will trigger DNS resolution; if it fails, DNS may be misconfigured.
traceroute <external website FQDN>
Why wrong: Also uses DNS, but ping is simpler for testing resolution.
show dns name-server
Why wrong: Shows configured DNS servers but does not test resolution.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
ping <external website FQDN>
Option B is correct because the `ping` command with a fully qualified domain name (FQDN) forces the Juniper device to perform a DNS resolution before sending ICMP echo requests. If the device cannot resolve the FQDN, the ping will fail with a 'hostname not found' error, directly indicating a DNS configuration or reachability issue. This tests both the DNS server configuration and the device's ability to resolve names, which is essential for verifying DNS functionality.
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.
show system connections
Why it's wrong here
Shows active connections, not DNS resolution.
ping <external website FQDN>
Why this is correct
Pinging a hostname will trigger DNS resolution; if it fails, DNS may be misconfigured.
Clue confirmation
The clue words "primary", "which command" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
traceroute <external website FQDN>
Why it's wrong here
Also uses DNS, but ping is simpler for testing resolution.
show dns name-server
Why it's wrong here
Shows configured DNS servers but does not test resolution.
Common exam traps
The trap here is that candidates often confuse `show dns name-server` with a valid operational command, but Junos uses `show configuration system name-server` to view DNS server settings, and the `ping` command with an FQDN is the standard method to test live DNS resolution from the device.
Trap categories for this question
Command / output trap
Shows active connections, not DNS resolution.
Detailed technical explanation
When you use `ping <FQDN>` on a Juniper device, the Junos kernel invokes the resolver library (typically based on the BIND resolver) to perform a DNS A or AAAA record lookup via UDP port 53 to the configured name-servers. The resolver uses the system's DNS cache and follows the order of name-servers in the configuration; if all servers are unreachable or return NXDOMAIN, the ping fails with a resolution error. In real-world scenarios, this command is invaluable for isolating split-DNS issues or verifying that the device's DNS servers are reachable through the correct security policy.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the JNCIA-JUNOS exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Junos OS Fundamentals — This question tests Junos OS Fundamentals — Read the scenario before looking for a memorised answer..
The correct answer is: ping <external website FQDN> — Option B is correct because the `ping` command with a fully qualified domain name (FQDN) forces the Juniper device to perform a DNS resolution before sending ICMP echo requests. If the device cannot resolve the FQDN, the ping will fail with a 'hostname not found' error, directly indicating a DNS configuration or reachability issue. This tests both the DNS server configuration and the device's ability to resolve names, which is essential for verifying DNS functionality.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "primary", "which command". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 11, 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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