The answer is MPLS. This is correct because the exhibit shows the configuration statement ‘family mpls’ explicitly applied under interface ge-0/0/0.0, which enables MPLS on that interface at the protocol family level, allowing it to participate in MPLS label switching. On the JNCIA-Junos exam, this question tests your ability to read Junos configuration output and identify which protocols are enabled on an interface—a common task when verifying MPLS deployments. A frequent trap is confusing the ‘family inet’ or ‘family iso’ statements with MPLS, but remember that MPLS must be explicitly enabled with its own family statement; it is not automatically active even if MPLS is configured globally. To quickly identify an MPLS enabled interface, look for the ‘family mpls’ line under the interface configuration hierarchy. A useful memory tip: “MPLS needs its own family—no family, no labels.”
JNCIA-JUNOS Operational Monitoring and Maintenance Practice Question
This JNCIA-JUNOS practice question tests your understanding of operational monitoring and maintenance. 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
Refer to the exhibit.
user@router> show interfaces ge-0/0/0.0
Logical interface ge-0/0/0.0 (Index 70) (SNMP ifIndex 521)
Flags: Up SNMP-Traps 0x4004000 Encapsulation: ENET2
Input packets : 1500
Output packets: 1200
Security: Zone: Trust
Allowed host-inbound traffic : any-service
Protocols:
inet:
10.0.0.1/24
iso:
mpls:
Maximum labels: 3
multiservice:
encapsulation: ethernet-ccc
Based on the exhibit, which protocol is enabled on interface ge-0/0/0.0?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
MPLS
The exhibit shows that interface ge-0/0/0.0 has the 'family mpls' statement configured under it, which enables MPLS on that interface. MPLS is explicitly enabled at the protocol family level, allowing the interface to participate in MPLS label switching.
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.
✗
IS-IS
Why it's wrong here
Not shown in the exhibit.
✗
BGP
Why it's wrong here
Not shown in the exhibit.
✓
MPLS
Why this is correct
Correct: MPLS is listed under Protocols.
Related concept
Read the scenario before looking for a memorised answer.
✗
OSPF
Why it's wrong here
Not shown in the exhibit.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse 'family mpls' with enabling a routing protocol like OSPF or IS-IS, not realizing that MPLS is a separate protocol family configured directly on the interface, not under the routing protocol hierarchy.
Trap categories for this question
Command / output trap
Not shown in the exhibit.
Detailed technical explanation
How to think about this question
MPLS (Multiprotocol Label Switching) operates at layer 2.5 and requires the 'family mpls' configuration on an interface to enable label switching. In Junos, MPLS can be used for traffic engineering (RSVP-TE) or LDP-based label distribution, and the interface must be explicitly configured to accept MPLS frames. A common real-world scenario is enabling MPLS on core-facing interfaces to build an MPLS LSP for VPN services.
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 network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
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.
Operational Monitoring and Maintenance — This question tests Operational Monitoring and Maintenance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: MPLS — The exhibit shows that interface ge-0/0/0.0 has the 'family mpls' statement configured under it, which enables MPLS on that interface. MPLS is explicitly enabled at the protocol family level, allowing the interface to participate in MPLS label switching.
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 →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.