The correct answer is that the interface will support both IPv4 and IPv6 traffic. This is because the configuration includes both `family inet` for IPv4 and `family inet6` for IPv6 under the same interface, which Junos natively allows as a dual-stack implementation. Junos treats address families as independent protocol stacks, so committing both families on a single interface enables simultaneous processing of IPv4 and IPv6 traffic without conflict or error. On the JNCIA-Junos exam, this concept tests your understanding of Junos interface configuration and the fact that multiple address families can coexist—a common trap is assuming that only one family is allowed per interface, or that a dual-stack configuration requires special flags. The key memory tip is “two families, one interface—dual-stack is the practice,” reinforcing that Junos does not require separate interfaces for IPv4 and IPv6.
JNCIA-JUNOS Junos Configuration Basics Practice Question
This JNCIA-JUNOS practice question tests your understanding of junos configuration basics. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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
[edit interfaces ge-0/0/0]
user@router# show
unit 0 {
family inet {
address 192.168.1.1/24;
}
family inet6 {
address 2001:db8::1/64;
}
}
user@router#
Refer to the exhibit. What will happen if the engineer commits this configuration?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The interface will support both IPv4 and IPv6 traffic.
Option C is correct because the configuration shown includes both `family inet` and `family inet6` under the same interface. Junos allows multiple address families to coexist on a single interface, enabling the interface to process both IPv4 and IPv6 traffic simultaneously. This is a standard feature of Junos, not an error.
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.
✗
The interface will have two primary IP addresses.
Why it's wrong here
Only one address per family, no 'primary' keyword indicates two primaries.
✗
The configuration will fail because inet and inet6 cannot coexist.
Why it's wrong here
Junos supports both families on the same interface.
✓
The interface will support both IPv4 and IPv6 traffic.
Why this is correct
Dual-stack interface with both address families.
Related concept
Read the scenario before looking for a memorised answer.
✗
Only the family inet will be applied.
Why it's wrong here
Both families are configured and will be applied.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may mistakenly think Junos requires separate interfaces for IPv4 and IPv6, or that configuring both families will cause a commit error, when in fact dual-stack is a standard and expected configuration in Junos.
Trap categories for this question
Keyword trap
Only one address per family, no 'primary' keyword indicates two primaries.
Detailed technical explanation
How to think about this question
Junos uses a hierarchical configuration structure where each interface can have multiple address families, each with its own set of addresses. The `family inet` stanza handles IPv4, while `family inet6` handles IPv6, and both can be active simultaneously (dual-stack). This is critical in modern networks where IPv6 adoption is growing, and interfaces must often support both protocols to ensure connectivity during migration.
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.
Junos Configuration Basics — This question tests Junos Configuration Basics — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The interface will support both IPv4 and IPv6 traffic. — Option C is correct because the configuration shown includes both `family inet` and `family inet6` under the same interface. Junos allows multiple address families to coexist on a single interface, enabling the interface to process both IPv4 and IPv6 traffic simultaneously. This is a standard feature of Junos, not an error.
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.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. Refer to the exhibit. What is the purpose of the 'family inet6' configuration on interface ge-0/0/0?
easy
A.To enable both IPv4 and IPv6 on the interface.
✓ B.To assign a global unicast IPv6 address to the interface.
C.To enable IPv6 ARP on the interface.
D.To assign a link-local IPv6 address to the interface.
Why B: The 'family inet6' configuration on interface ge-0/0/0 enables IPv6 processing on that interface. Within the 'family inet6' hierarchy, you can assign a global unicast IPv6 address using the 'address' statement. Without 'family inet6', the interface cannot process IPv6 traffic or hold an IPv6 address, making option B correct.
Last reviewed: Jun 24, 2026
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