JN0-106 Junos Configuration Basics Practice Question
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?
⚠ Common exam trap
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.
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
✓
The interface will support both IPv4 and IPv6 traffic.
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.
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
Junos elects a single primary IPv4 address and a single primary IPv6 address independently; there is no concept of multiple primary addresses within the same address family. Adding an IPv6 address under family inet6 does not create a second primary for family inet because each family has its own primary election mechanism, typically selecting the first configured address unless the 'primary' statement is explicitly used. Therefore, the interface will have one primary for IPv4 and one for IPv6, not two primaries.
- ✗
The configuration will fail because inet and inet6 cannot coexist.
Why it's wrong here
Junos supports dual-stack interfaces natively, allowing both family inet and family inet6 to be configured concurrently on the same logical interface. There is no conflict or commit failure when both address families are present because they are processed by separate protocol stacks within the same data path. In fact, this is the standard method for enabling IPv4 and IPv6 together on a Junos device, so the configuration will commit successfully.
- ✓
The interface will support both IPv4 and IPv6 traffic.
Why this is correct
Configuring both family inet and family inet6 on an interface makes it dual-stacked, meaning it can forward IPv4 packets using the inet stack and IPv6 packets using the inet6 stack simultaneously. Each family has its own address, routing table entries, and protocol behavior, and both are active after the configuration is committed. This allows the interface to carry both IPv4 and IPv6 traffic without the need for tunneling or translation.
- ✗
Only the family inet will be applied.
Why it's wrong here
Junos does not apply protocol families on a precedence basis; all configured families under an interface are activated when the configuration is committed. The inet and inet6 families are independent configuration blocks, and omitting or failing one does not disable the other unless there is an explicit 'disable' statement. Since both are correctly configured, the interface will forward traffic for IPv4 and IPv6 alike, so claiming only inet will be applied is incorrect.
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Same concept, more angles
1 more way this is tested on JN0-106
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.
JA
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.