JN0-106 Junos OS Fundamentals Practice Question
Exhibit
Refer to the exhibit.
root@router> show configuration interfaces
ge-0/0/0 {
unit 0 {
family inet {
address 192.168.1.1/24;
}
}
}
root@router> show interfaces ge-0/0/0 terse
Interface Admin Link Proto Local Remote
ge-0/0/0 up up inet 192.168.1.1/24Refer to the exhibit. An operator tries to ping 192.168.1.2 from this router and fails. The router can ping itself (192.168.1.1). What is the most likely cause?
⚠ Common exam trap
Test-takers frequently confuse a local connectivity issue (like a down interface or RPF) with a remote host unreachability, but the ability to ping the local interface proves the interface is operational and the problem lies with the destination host or its ARP response.
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 remote host is not reachable or is not responding to ARP requests.
The router can ping its own interface (192.168.1.1), confirming that the interface is up and IP is configured correctly. The failure to ping 192.168.1.2 indicates that the router cannot reach the remote host, most likely because the host is down, not connected, or not responding to ARP requests. ARP resolution is required for the router to map the destination IP to a MAC address on the local subnet; without a successful ARP reply, the router cannot send the echo request.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Reverse path forwarding (RPF) check is dropping the echo request.
Why it's wrong here
RPF checks apply only to transit traffic being forwarded through the router, not to packets that the router itself originates, such as ICMP echo requests generated by a ping command. Even if RPF had been enabled, it would evaluate the source address of incoming packets on an interface against the unicast route table; a locally sourced ping never undergoes that input-interface check. Moreover, nothing in the exhibit suggests RPF is configured, so this cannot be the cause of the failure.
- ✓
The remote host is not reachable or is not responding to ARP requests.
Why this is correct
To ping 192.168.1.2 from a directly connected interface, the router must first resolve that destination IP to a MAC address using an ARP request. If the remote host is down, unreachable at Layer 2, or configured with a different IP, it will not send an ARP reply, and the router will report the ping as failing (e.g., 'Host is down' or an incomplete ARP entry). Since the interface is up and has an IP in the same subnet, ARP resolution failure is the classic and most likely explanation for this symptom.
- ✗
The interface is administratively down.
Why it's wrong here
The exhibit explicitly shows 'Admin: up' in the interface status, meaning the interface has not been administratively disabled with the 'disable' configuration statement. An administratively down interface would display 'Admin: down' and would also remove the connected route from the routing table, causing the ping to fail immediately with a network unreachable or no route error. Because the interface shows both admin and operational up state, this option is not applicable.
- ✗
Proxy ARP is not configured on the interface.
Why it's wrong here
Proxy ARP is a feature where a router replies to ARP requests on behalf of a host that is on a different subnet or network segment, allowing the requesting host to think the router is the owner of the target IP. In this scenario, both the operator and the target 192.168.1.2 reside on the same subnet, so direct ARP (without proxy) is the correct and expected behavior. The absence of proxy ARP would only matter if the target were behind a router on a different L2 domain, which is not the case here.
Visual reference
Quick reference
Access Control Model Comparison
| Model | Acronym | Who Controls Access? | Best For |
|---|---|---|---|
| Discretionary Access Control | DAC | Resource owner | Small teams, file shares |
| Mandatory Access Control | MAC | System / security labels | Classified govt / military |
| Role-Based Access Control | RBAC | Administrator (via roles) | Enterprise environments |
| Attribute-Based Access Control | ABAC | Policy engine (user + resource attributes) | Fine-grained, dynamic policies |
| Rule-Based Access Control | RuBAC | System rules / ACLs | Firewall rules, network ACLs |
Go deeper
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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.