20+ practice questions focused on Layer 2 Switching And VLANs — one of the most tested topics on the Juniper Networks Enterprise Routing and Switching, Specialist (JNCIS-ENT, JN0-352) (JNCIS-ENT) exam. Each question includes a detailed explanation so you learn why the right answer is correct.
Start Layer 2 Switching And VLANs PracticeYou are configuring Q-in-Q tunneling on an enterprise EX4600 switch. The customer-facing edge port must encapsulate incoming customer frames with an outer VLAN tag of 200. Which port mode should be configured on the customer-facing interface?
Explanation: For Q-in-Q tunneling on a customer-facing edge port, the port must be configured as 'qinq-access' (also known as 'dot1q-tunnel' in some vendors). This mode encapsulates incoming customer frames with an outer VLAN tag (the S-VLAN) specified by the service provider. The correct configuration is 'set interfaces et-0/0/0 unit 0 family ethernet-switching interface-mode qinq-access'.
While reviewing the MAC address table on an EX Series switch using 'show ethernet-switching table', you notice a specific MAC address has a 'Flags' field showing 'L'. What does the 'L' flag indicate?
Explanation: In Junos OS, the 'L' flag in the ethernet-switching table indicates that the MAC address was learned dynamically on that interface.
An engineer must configure an EX Series switch trunk port to allow all VLANs while explicitly blocking VLAN 50. Which Junos configuration statement accomplishes this behavior?
Explanation: The correct Junos syntax to allow all VLANs except VLAN 50 on a trunk port is 'vlan members all except 50'. This uses the 'all' keyword to include every VLAN and the 'except' keyword to explicitly exclude VLAN 50. This is the standard Junos way to express an exclusion list on a trunk interface.
On an EX Series switch, you have configured private VLANs (PVLANs) where community VLAN ports need to communicate with a designated promiscuous port, but not with ports in other community VLANs. Which hierarchical configuration is mandatory to bind the primary VLAN and secondary VLANs together?
Explanation: On Junos EX Series switches, private VLANs are configured hierarchically under the primary VLAN using the 'private-vlan' statement, which binds secondary VLANs (community or isolated) to the primary VLAN. The correct syntax is 'set vlans <primary> vlan-id <id> private-vlan community [ <secondary-ids> ]', which creates the primary/secondary association required for PVLAN operation.
An engineer configures Selective QinQ on an EX Series switch. Incoming customer frames tagged with VLAN 10 must be mapped to outer VLAN 500, while frames tagged with VLAN 20 must be mapped to outer VLAN 600. Which configuration component is required to achieve this granular mapping?
Explanation: Flexible VLAN Tagging with input-vlan-map allows granular mapping of incoming customer VLAN tags to different outer VLAN tags on a per-VLAN basis. This is exactly what Selective QinQ requires: mapping VLAN 10 to outer VLAN 500 and VLAN 20 to outer VLAN 600. The input-vlan-map configuration specifies the rewrite action for each customer VLAN, enabling this selective encapsulation.
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Practice all Layer 2 Switching And VLANs questions1. Baseline your knowledge
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2. Review every explanation
For each question — right or wrong — read the full explanation. Understanding why an answer is correct is more valuable than knowing the answer itself.
3. Focus on exam traps
Layer 2 Switching And VLANs questions on the JNCIS-ENT frequently use trap wording. Look for subtle differences in answers that test your precision, not just general knowledge.
4. Reach 80% consistently
Do repeated sessions until you score 80%+ three times in a row. Then move to mixed-mode practice to test cross-topic recall under realistic conditions.
The exact number varies per candidate. Layer 2 Switching And VLANs is tested as part of the Juniper Networks Enterprise Routing and Switching, Specialist (JNCIS-ENT, JN0-352) (JNCIS-ENT) blueprint. Practicing with targeted Layer 2 Switching And VLANs questions ensures you can handle any format or difficulty that appears.
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