JN0-106 Networking Fundamentals Practice Question
A host in VLAN 10 can ping a host in VLAN 20 without a default gateway configured. What feature is likely enabled on the router that interconnects the VLANs?
⚠ Common exam trap
Watch out — candidates often assume IP routing alone is sufficient for inter-VLAN communication, forgetting that hosts must have a default gateway or use proxy ARP to send traffic outside their local subnet.
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
✓
Proxy ARP
Proxy ARP allows a router to respond to ARP requests on behalf of hosts in different subnets. When a host in VLAN 10 sends an ARP request for a host in VLAN 20, the router responds with its own MAC address if it has a route to the destination. This enables the host to send traffic to the router, which then forwards it to the destination VLAN, even without a default gateway configured on the host.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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VLAN translation is configured on the trunk
Why it's wrong here
VLAN translation remaps the 802.1Q tag on a trunk link, but it operates strictly at Layer 2 and only changes which VLAN a frame belongs to. The host in VLAN 10 still has no route to the 20 subnet and no default gateway, so it will not forward the packet to the router. Even if the router received the frame, the host must first make the decision to send it there, and VLAN translation cannot influence that Layer 3 decision.
- ✓
Proxy ARP
Why this is correct
Proxy ARP enables the router to reply to ARP requests for IP addresses that are actually in other subnets, providing its own MAC address as the next hop. This makes the host believe the remote host is directly reachable, so it sends frames to the router, which then routes them to VLAN 20. This gives the host a path to the remote subnet without requiring a default gateway configuration, which is exactly why it works here.
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IP routing is enabled on the router
Why it's wrong here
Enabling IP routing on the router turns on its Layer 3 forwarding capabilities, but it does nothing to address the host's missing default gateway. When the host determines the destination is off-subnet, it checks for a gateway; without one, it cannot generate a frame to reach the router. The router never sees the packet, so its routing table is irrelevant to this problem.
- ✗
Dynamic ARP Inspection
Why it's wrong here
Dynamic ARP Inspection (DAI) is a switch security feature that validates ARP packets against DHCP snooping bindings to block spoofing attacks. It only inspects and filters ARP messages; it does not influence a host's forwarding decision or provide any Layer 3 reachability. DAI cannot cause the host to send packets to the router, nor can it make a remote host appear local, so it has no bearing on inter-VLAN communication.
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 |
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About these practice questions
Courseiva writes every JN0-106 question from scratch — 156 in total, each with an explanation and a wrong-answer breakdown. None are copied from real exams or dumps. Learn why practice questions differ from exam dumps →
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.