The answer is that the description statement under an interface configuration sets the interface description visible in the output of the show interfaces description command. This is correct because in Junos, the description statement is a simple text string—often used to label the interface with a human-readable name like “Link to Core Router A”—that is stored in the configuration and displayed exclusively by that specific show command. On the JNCIA-Junos exam, this concept tests your understanding of basic interface configuration and operational commands, and it often appears as a trap where candidates confuse it with SNMP sysContact, administrative comments, or syslog tags. A common memory tip is to think of “description” as a sticky note on the interface: it’s only for your eyes when you run show interfaces description, not for any automated system.
JNCIA-JUNOS User Interfaces Practice Question
This JNCIA-JUNOS practice question tests your understanding of user interfaces. Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. 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.
Exhibit
interfaces {
ge-0/0/0 {
description "Link to Core-1";
unit 0 {
family inet {
address 10.0.0.1/30;
}
}
}
}
Refer to the exhibit. An administrator sees the following configuration output. What is the purpose of the 'description' statement in this context?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
It sets the interface description visible in 'show interfaces description'.
In Junos, the 'description' statement under an interface configuration sets a text string that is displayed in the output of 'show interfaces description'. This is the standard way to provide a human-readable label for the interface, such as 'Link to Core Router A'. It does not affect SNMP, administrative comments, or syslog tags.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
It sets the SNMP ifAlias to the interface's MAC address.
Why it's wrong here
The ifAlias is set to the description text, not the MAC address.
✗
It sets the administrative comment visible in the config.
Why it's wrong here
The description is not merely a comment; it affects the interface's operational display.
✓
It sets the interface description visible in 'show interfaces description'.
Why this is correct
Correct; the description appears in the output of 'show interfaces description' and sets the ifAlias SNMP object.
Related concept
Read the scenario before looking for a memorised answer.
✗
It sets the interface's syslog tag.
Why it's wrong here
Syslog tags are configured elsewhere under 'system syslog'.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the 'description' statement with the SNMP ifAlias or administrative comments, assuming they serve the same purpose as in other vendors' syntax, but Junos explicitly separates these functions.
Detailed technical explanation
How to think about this question
The 'description' statement is a standard interface configuration parameter defined in RFC 2863 (ifAlias) but in Junos it is stored separately from the SNMP MIB-II ifAlias object. The 'show interfaces description' command displays only the description field, making it useful for quickly identifying interface purposes in large networks. A subtle behavior: if you configure a description on a logical unit (e.g., ge-0/0/0.0), it applies only to that unit, not the physical interface.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
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
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
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. 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
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
User Interfaces — This question tests User Interfaces — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: It sets the interface description visible in 'show interfaces description'. — In Junos, the 'description' statement under an interface configuration sets a text string that is displayed in the output of 'show interfaces description'. This is the standard way to provide a human-readable label for the interface, such as 'Link to Core Router A'. It does not affect SNMP, administrative comments, or syslog tags.
What should I do if I get this JNCIA-JUNOS question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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