Free JN0-280: Data Center Associate (JNCIA-DC) Exam Questions and Answers
35 verified practice questions for JN0-280.
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Last updated: September 19, 2026
- Exam code
- JN0-280
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- Juniper
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Question #1
You are creating an IP fabric underlay and want to use OSPF as your routing protocol. In this scenario, which statement is correct?
Please select an optionIncorrectCorrect answer: C
When creating an IP fabric underlay using OSPF as the routing protocol, consistent interface speeds are important to ensure optimal traffic distribution and utilization of all links. Step-by-Step Breakdown: OSPF and Interface Speeds: OSPF calculates the cost of a link based on its bandwidth. The default cost calculation in OSPF is: Cost = Reference Bandwidth / Interface Bandwidth. If interface speeds vary significantly, OSPF may choose paths with lower cost (higher bandwidth), resulting in some links being underutilized. Equal Utilization: To ensure that all links are equally utilized in an IP fabric, it is recommended to maintain uniform interface speeds across the fabric. This ensures balanced load sharing across all available paths. Juniper Reference: IP Fabric with OSPF: Juniper recommends consistent interface speeds to maintain even traffic distribution and optimal link utilization in IP fabric underlay designs.
Was this answer correct?Question #2
Which statement is correct about aggregate routes?
Please select an optionIncorrectCorrect answer: D
An aggregate route is a summarized route that is created by combining multiple specific routes into a single, broader route. In Junos OS, when an aggregate route is configured, its default next hop is set toreject. Step-by-Step Explanation:: Aggregate Route:Aggregate routes are used to reduce the size of routing tables by representing a collection of more specific routes with a single summary route. They help improve routing efficiency and scalability, especially in large networks. Default Next Hop Behavior: When you configure an aggregate route in Junos OS, it has arejectnext hop by default. Therejectnext hop means that if a packet matches the aggregate route but there is no more specific route in the routing table for that destination, the packet will be discarded, and an ICMP "destination unreachable" message is sent to the source. This behavior helps to prevent routing loops and ensures that traffic isn't forwarded to destinations for which there is no valid route. Modifying Next Hop:If needed, the next hop behavior of an aggregate route can be changed todiscard (which silently drops the packet) or to another specific next hop. However, by default, the next hop is set toreject. Juniper Reference: Junos Command: set routing-options aggregate route <route> reject to configure an aggregate route with a reject next hop. Verification: Use show route to verify the presence and behavior of aggregate routes.
Was this answer correct?Question #3
What are two requirements for an IP fabric? (Choose two.)
Select 2 answers.
Please select an optionIncorrectCorrect answer: A, B
AnIP fabricis a network architecture commonly used in data centers to provide scalable, high-throughput connectivity using aspine-leaf topology. Step-by-Step Breakdown: Layer 3 Routing Protocol:An IP fabric relies on aLayer 3 routing protocol, typically BGP or OSPF, to provide routing between the leaf and spine switches. This ensures efficient traffic forwarding across the network. Single Connection Between Spine and Leaf:In an IP fabric, each leaf switch connects toevery spine switchwith a single connection. This ensures that traffic between any two leaf switches can travel through the spine layer in just two hops. Juniper Reference: Spine-Leaf Design: Juniper's IP fabric implementations are designed for scalability and low-latency routing, often using protocols like BGP for Layer 3 control.
Was this answer correct?Question #4
Which two statements about IBGP are correct? (Choose two.)
Select 2 answers.
Please select an optionIncorrectCorrect answer: C, D
: IBGP (Internal Border Gateway Protocol)is used to exchange routing information betweenrouters within the same AS (Autonomous System). Step-by-Step Breakdown: TTL of 255: By default, IBGP sessions are established with aTTL (Time to Live)value of255. This allows IBGP neighbors to communicate over multiple hops within the AS without requiring any additional configuration. Full Mesh Requirement: IBGP requires alogical full meshbetween all IBGP routers to ensure that routing information is fully distributed within the AS. Since IBGP does not propagate routes learned from one IBGP peer to another by default, a full mesh topology is needed unlessroute reflectorsorBGP confederationsare used. Juniper Reference: IBGP Full Mesh: Juniper recommends using route reflectors in large networks to simplify IBGP full-mesh requirements.
Was this answer correct?Question #5
What is the default route preference of a static route in the Junos OS?
Please select an optionIncorrectCorrect answer: C
In Junos OS, the default route preference for a static route is 5. Route preference values are used to determine which route should be installed in the routing table when multiple routes to the same destination are available. Step-by-Step Breakdown: Static Route Preference: A static route, by default, has a preference of 5, making it a highly preferred route. Lower preference values are more preferred in Junos, meaning static routes take precedence over most dynamic routing protocol routes, such as OSPF (preference 10) or BGP (preference 170). Route Preference: Route preference is a key factor in the Junos routing decision process. Routes with lower preference values are preferred and installed in the forwarding table. Juniper Reference: Static Routes: In Junos, the default preference for static routes is 5, making them more preferred than most dynamic routes.
Was this answer correct?Question #6
Exhibit: Referring to the exhibit, which statement is correct?
Please select an optionIncorrectCorrect answer: B
In the exhibit, BGP is configured with local AS 65101 and a neighbor at 172.16.1.1 in peer AS 65201. This setup involves two different Autonomous Systems (AS), indicating an External BGP (EBGP) configuration. Step-by-Step Breakdown: EBGP vs. IBGP: EBGP is used between routers in different ASes. In this case, the local AS is 65101 and the peer AS is 65201, meaning the BGP session is EBGP. IBGP is used between routers within the same AS, which is not applicable here as the AS numbers are different. BGP Group Configuration: The configuration does not require a type external parameter because Junos OS automatically recognizes the session as EBGP when the local and peer AS numbers are different. The BGP session will operate as EBGP, and the configuration will commit successfully. Juniper Reference: BGP Configuration: In Juniper, EBGP is automatically recognized when the local and peer AS numbers differ, without needing to specify type external.
Was this answer correct?Question #7
Which two statements are correct about EVPN-VXLAN overlay networking? (Choose two.)
Select 2 answers.
Please select an optionIncorrectCorrect answer: B, C
EVPN-VXLANis an overlay technology used in data center networks to extend Layer 2 services over a Layer 3 network. Step-by-Step Breakdown: BGP Control Plane:BGP (Border Gateway Protocol)is used as the control plane for EVPN-VXLAN. BGP advertises MAC addresses and IP address reachability information across the VXLAN network, enabling efficient multi-tenant Layer 2 connectivity over a Layer 3 infrastructure. Encapsulation:VXLAN (Virtual Extensible LAN)encapsulates Layer 2 frames into Layer 3 packets. This encapsulation allows Layer 2 traffic to be transported across a Layer 3 network, effectively creating a tunnel for Ethernet frames. Juniper Reference: EVPN-VXLAN Configuration: Juniper supports EVPN-VXLAN with BGP as the control plane, allowing scalable Layer 2 connectivity over a routed infrastructure in modern data centers.
Was this answer correct?Question #8
Which statement is correct about per-flow load balancing?
Please select an optionIncorrectCorrect answer: C
Per-flow load balancingensures that packets within the same flow are always forwarded over the same path, ensuring that packet order is preserved. Step-by-Step Breakdown: Flow Definition:A flow is typically defined by a combination of packet attributes like source/destination IP, source/destination port, and protocol type. Packets that belong to the same flow are routed over the same path to avoid reordering. Per-Flow Behavior:Inper-flow load balancing, the hashing algorithm ensures that all packets in a particular flow use thesame egress port, maintaining order across the network. Juniper Reference: Load Balancing in Juniper: This method ensures that flows are balanced across multiple paths while preventing packet reordering within a single flow.
Was this answer correct?Question #9
You want to enable a Junos device to support aggregated Ethernet interfaces. In this scenario, which configuration hierarchy would you use?
Please select an optionIncorrectCorrect answer: D
To configureaggregated Ethernet (AE) interfaceson a Junos device, the configuration is done under the[edit chassis]hierarchy. Step-by-Step Breakdown: Chassis Configuration:Thechassisconfiguration is responsible for enabling the hardware to supportLink Aggregation Groups (LAGs), allowing multiple physical interfaces to be bundled into a single logical interface for load balancing and redundancy. Command Example: set chassis aggregated-devices ethernet device-count This command enables a specific number of aggregated Ethernet interfaces on the device. Juniper Reference: LAG Configuration in Junos: Thechassishierarchy is used to allocate and manage hardware resources for aggregated Ethernet interfaces in Juniper devices.
Was this answer correct?Question #10
What are two reasons why you would deploy an IP fabric instead of a traditional Layer 2 network in a data center? (Choose two.)
Select 2 answers.
Please select an optionIncorrectCorrect answer: C, D
Layer 3 IP fabrics use ECMP to load-balance traffic across multiple equal paths, and they avoid the loops that Layer 2 networks are prone to without STP. Layer 2 networks support multiple broadcast domains via VLANs, and IP fabrics are built for large scale.
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