JN0-106 Operational Monitoring and Maintenance Practice Question
Exhibit
Output of 'show interfaces terse': Interface Admin Link Proto Local Remote ge-0/0/0 up up inet 192.168.1.1/24 ge-0/0/1 up down inet ge-0/0/2 down down ge-0/0/3 up up inet 10.0.0.1/30 lo0 up up inet 127.0.0.1
Refer to the exhibit. Which interface has a physical layer connectivity problem?
⚠ Common exam trap
The trap here is that candidates may focus on the 'Admin' status (up/down) rather than the 'Physical link' status, mistakenly assuming an administratively down interface is a physical layer problem, when in fact the physical layer issue is indicated by the link state being down regardless of administrative configuration.
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
✓
ge-0/0/1
Interface ge-0/0/1 shows 'Physical link is Down' in the output, which directly indicates a physical layer connectivity problem. The 'Device present' field is also 'No', confirming that no transceiver or cable is detected, which is a Layer 1 issue.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
ge-0/0/2
Why it's wrong here
ge-0/0/2 is administratively down, meaning the interface has been intentionally disabled in configuration. Even if a cable is connected and a transceiver is present, the link will remain down because the interface is disabled. This is a configuration state, not a physical layer failure; the link would come up only after removing the 'disable' statement.
- ✗
ge-0/0/0
Why it's wrong here
ge-0/0/0 is administratively up and the link is up, indicating that the physical layer is healthy. The interface has successfully negotiated with the peer, and the carrier is detected on the wire. Since both administrative and operational states are up, there is no indication of a physical layer problem on this port.
- ✗
ge-0/0/3
Why it's wrong here
ge-0/0/3 is administratively up and shows link up, so the physical medium is functioning correctly. In Junos, 'show interfaces ge-0/0/3' would display 'Physical link is Up', confirming that light or electrical signal is present. A physical layer issue would manifest as a down condition despite an up administrative state, which is not the case here.
- ✓
ge-0/0/1
Why this is correct
ge-0/0/1 is administratively up (configuration enables the interface) but the link is down, meaning the physical layer is not establishing connectivity. This mismatch—admin up, link down—points to a Layer 1 problem such as a disconnected cable, faulty optics, or an unpowered peer. Unlike an administratively down interface, this is not expected; further troubleshooting like checking the SFP and cable is needed.
Quick reference
OSI Model Reference
| Layer | Name | PDU | Key Protocols / Devices |
|---|---|---|---|
| 7 | Application | Data | HTTP, HTTPS, DNS, SMTP, FTP, SSH |
| 6 | Presentation | Data | TLS / SSL, JPEG, ASCII encoding |
| 5 | Session | Data | NetBIOS, RPC, SIP |
| 4 | Transport | Segment / Datagram | TCP, UDP |
| 3 | Network | Packet | IP, ICMP, OSPF — Routers |
| 2 | Data Link | Frame | Ethernet, Wi-Fi, PPP — Switches, Bridges |
| 1 | Physical | Bits | Cables, NICs, Hubs, Repeaters |
Go deeper
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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.