- A
show interfaces extensive
Correct. 'show interfaces extensive' displays the encapsulation type, which is necessary to verify that both routers use the same encapsulation for proper communication.
- B
show interfaces terse
Why wrong: Incorrect. 'show interfaces terse' does not show encapsulation type; it only shows a brief status summary.
- C
show configuration interfaces
Why wrong: Incorrect. 'show configuration interfaces' shows the configuration, not operational state or current encapsulation negotiation.
- D
monitor traffic interface
Why wrong: Incorrect. 'monitor traffic interface' captures packets in real-time but does not display the configured encapsulation type.
Question 237 of 514
JNCIA-JUNOS encapsulation type Practice Question
This JNCIA-JUNOS practice question tests your understanding of networking fundamentals. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. A key principle to apply: encapsulation type. 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 network engineer is troubleshooting connectivity between two directly connected Juniper routers. The interface on Router A shows 'up' but no packets are being received from Router B. Which command should the engineer use on Router A to check if the interface is expecting to receive a specific encapsulation type?
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.
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
✓
show interfaces extensive
Option A is correct because the 'show interfaces extensive' command displays detailed interface information, including the encapsulation type configured on the interface. If Router A expects a specific encapsulation (e.g., PPP, HDLC, or Ethernet) that does not match what Router B is sending, the interface will show 'up' but will not receive packets. This command allows the engineer to verify the configured encapsulation type. Option B is incorrect because 'show interfaces terse' provides a concise summary (name, status, protocol, and address) but does not include encapsulation details.
Key principle: encapsulation type
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 interfaces extensive
Why this is correct
Correct. 'show interfaces extensive' displays the encapsulation type, which is necessary to verify that both routers use the same encapsulation for proper communication.
Clue confirmation
The clue word "which command" in the question point toward this answer.
Related concept
encapsulation type
- ✗
show interfaces terse
Why it's wrong here
Incorrect. 'show interfaces terse' does not show encapsulation type; it only shows a brief status summary.
- ✗
show configuration interfaces
Why it's wrong here
Incorrect. 'show configuration interfaces' shows the configuration, not operational state or current encapsulation negotiation.
- ✗
monitor traffic interface
Why it's wrong here
Incorrect. 'monitor traffic interface' captures packets in real-time but does not display the configured encapsulation type.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates often assume 'show interfaces terse' includes encapsulation details, but it only provides a quick summary. The 'extensive' option is needed for encapsulation type.
Trap categories for this question
Command / output trap
Incorrect. 'show interfaces terse' does not show encapsulation type; it only shows a brief status summary.
Detailed technical explanation
How to think about this question
In Junos, encapsulation types such as 'ppp', 'hdlc', 'ethernet-ccc', or 'vlan-ccc' are configured under the 'encapsulation' statement at the [edit interfaces <name>] hierarchy level. When two directly connected routers have mismatched encapsulations, the interface may still show 'up' at the physical layer (carrier detect) but will drop incoming frames because the framing or protocol identifier does not match expectations. The 'show interfaces terse' command outputs the encapsulation type in the 'Proto' column for each interface, making it a quick first step in isolating such mismatches.
KKey Concepts to Remember
- encapsulation type
- show interfaces extensive
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
encapsulation type
Real-world example
How this comes up in practice
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. encapsulation type Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Review encapsulation type, then practise related JNCIA-JUNOS questions on the same topic to reinforce the concept.
- →
Networking Fundamentals — study guide chapter
Learn the concepts, then practise the questions
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FAQ
Questions learners often ask
What does this JNCIA-JUNOS question test?
Networking Fundamentals — This question tests Networking Fundamentals — encapsulation type.
What is the correct answer to this question?
The correct answer is: show interfaces extensive — Option A is correct because the 'show interfaces extensive' command displays detailed interface information, including the encapsulation type configured on the interface. If Router A expects a specific encapsulation (e.g., PPP, HDLC, or Ethernet) that does not match what Router B is sending, the interface will show 'up' but will not receive packets. This command allows the engineer to verify the configured encapsulation type. Option B is incorrect because 'show interfaces terse' provides a concise summary (name, status, protocol, and address) but does not include encapsulation details.
What should I do if I get this JNCIA-JUNOS question wrong?
Review encapsulation type, then practise related JNCIA-JUNOS questions on the same topic to reinforce the concept.
Are there clue words in this question I should notice?
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.
What is the key concept behind this question?
encapsulation type
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Last reviewed: Jun 11, 2026
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