JN0-106 Networking Fundamentals Practice Question
A company is deploying an EVPN-VXLAN fabric with Juniper QFX switches. To provide inter-subnet routing, which interface type must be configured?
⚠ Common exam trap
Many exam-takers confuse VTEPs (which handle tunneling) with the routing function, mistakenly thinking that configuring a VTEP alone enables inter-subnet routing, when in fact an IRB interface is required to act as the Layer 3 gateway.
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
✓
IRB interface
In an EVPN-VXLAN fabric, Integrated Routing and Bridging (IRB) interfaces are required to provide inter-subnet routing. IRB interfaces act as Layer 3 gateways within the VXLAN overlay, enabling routing between different VLANs/VXLANs by terminating both the bridge domain and the routing instance. Without IRB, traffic cannot be routed between subnets in the EVPN-VXLAN fabric.
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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Physical interface with vlan-tagging
Why it's wrong here
A physical interface configured with vlan-tagging operates at Layer 2, using 802.1Q tags to multiplex multiple VLANs on a single trunk port. While it correctly segments broadcast domains and forwards Ethernet frames within a VLAN, it has no IP routing capability and cannot act as a default gateway. In an EVPN-VXLAN fabric, inter-VLAN routing requires a logical Layer 3 interface, such as an IRB, not a Layer 2 physical port.
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VXLAN tunnel endpoint (VTEP)
Why it's wrong here
A VXLAN tunnel endpoint (VTEP) is the overlay edge device responsible for encapsulating and decapsulating VXLAN frames, mapping a VLAN to a VNI and forwarding traffic over the underlay network. The VTEP's role is strictly Layer 2 transport across the IP fabric; it does not make routing decisions or provide a gateway for hosts. For inter-VLAN routing, an IRB interface must be configured on the leaf switch, which terminates the VXLAN tunnel and performs Layer 3 forwarding.
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IRB interface
Why this is correct
An IRB (Integrated Routing and Bridging) interface is a logical, per-VLAN Layer 3 interface that provides the default gateway for hosts within that VLAN in an EVPN-VXLAN fabric. It bridges frames within the VLAN (via the bridging table) and routes packets between VLANs (via the routing table), enabling local inter-VLAN traffic without hair-pinning to an external router. This is exactly the required function: a Layer 3 gateway that is integrated with the VXLAN overlay, making IRB the correct answer.
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Loopback interface
Why it's wrong here
A loopback interface is a virtual, always-up interface on the device, typically assigned a stable IP address for management, OSPF/BGP peering, and as the source IP for VXLAN tunnels (VTEP address). However, a loopback is not tied to any specific VLAN and does not carry host traffic; it is a device-level identifier, not a per-VLAN gateway. Therefore, it cannot provide Layer 3 routing for VLANs, which is the role of an IRB interface.
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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.