JN0-280 Exam Dumps, JN0-280 Practice Test Questions
PDF (New 2025) Actual Juniper JN0-280 Exam Questions
The JN0-280 exam covers a wide range of topics related to data center networking, including virtualization, storage networking, data center architecture, and Juniper Networks products such as EX Series Ethernet Switches, QFX Series Ethernet Switches, and SRX Series Services Gateways. Candidates must demonstrate a thorough understanding of these topics in order to pass the exam and earn the JNCIA-DC certification.
Juniper JN0-280 (Data Center, Associate (JNCIA-DC)) Certification Exam is designed to test the skills and knowledge of individuals who are interested in working with Juniper Networks' data center solutions. Data Center, Associate (JNCIA-DC) certification exam covers key topics such as data center fundamentals, data center architecture, Ethernet switching, virtualization, and more. The JNCIA-DC certification is ideal for individuals who are looking to start a career in data center networking or those who are already working in the field and are looking to enhance their knowledge and skills.
NEW QUESTION # 62
In OSPF, which term refers to routers that have interfaces in multiple areas?
- A. Area Border Routers (ABRs)
- B. Backbone Routers
- C. Autonomous System Boundary Routers (ASBRs)
- D. Internal Routers
Answer: A
NEW QUESTION # 63
Referring to the exhibit, you notice that after committing the configuration, the ae0 and ae1 interfaces appear in a link down state.
Which statement is correct in this scenario?
- A. No operational interfaces have been added to the LAG interfaces.
- B. The LAG interfaces are in a passive state.
- C. The LAG interfaces are in aggressive mode.
- D. No traffic is traversing the LAG interfaces.
Answer: A
Explanation:
In the exhibit, theae0andae1interfaces are in alink downstate. This occurs when no physical interfaces (member interfaces) have been added to theLAG (Link Aggregation Group)interfaces, or the member interfaces are not operational.
Step-by-Step Breakdown:
* LAG Configuration:ALAGinterface (aggregated Ethernet interface) is a logical interface that combines multiple physical interfaces for redundancy and increased bandwidth. The LAG will only be operational if at least one member interface is active and configured correctly.
* No Operational Member Interfaces:If no member interfaces are added or if the member interfaces are down, the LAG will remain in adownstate, as shown in the exhibit for ae0 and ae1.
* Resolution:Verify that physical interfaces have been added to the LAG using commands like:
LAG Interface Status: In Juniper, the link status of the LAG depends on its member interfaces, which must be operational for the LAG to function.
NEW QUESTION # 64
EVPN/VXLAN is primarily used in modern data centers to:
- A. Enhance the physical security of the data center.
- B. Provide Layer 2 connectivity over a Layer 3 network.
- C. Replace traditional routing protocols.
- D. Increase the physical distance between data centers.
Answer: B
NEW QUESTION # 65
What are the different OSPF area types? (Choose two)
- A. Virtual Link Area
- B. Stub Area
- C. Not-So-Stubby Area (NSSA)
- D. Default-Free Zone
Answer: B,C
NEW QUESTION # 66
In the Junos OS, what is the default behavior of a switch when it receives a frame with an unknown destination MAC address?
- A. It floods the frame out of all ports except the one it was received on.
- B. It sends the frame to its default gateway.
- C. It buffers the frame until the MAC address can be learned.
- D. It discards the frame.
Answer: A
NEW QUESTION # 67
Which of the following is a key benefit of implementing High Availability (HA) in a network?
- A. Reduced network security
- B. Slower data recovery
- C. Increased network downtime
- D. Enhanced data redundancy
Answer: D
NEW QUESTION # 68
Which signaling protocol is used for EVPN?
- A. BGP
- B. OSPF
- C. IS-IS
- D. PIM
Answer: A
Explanation:
EVPN (Ethernet Virtual Private Network)is a standard protocol used for building Layer 2 and Layer 3 VPNs over an IP or MPLS network. Thesignaling protocolused for EVPN isBGP(Border Gateway Protocol).
Step-by-Step Breakdown:
* BGP as the EVPN Signaling Protocol:EVPN uses BGP to exchange MAC address reachability information between routers (PE devices). This enables devices to learn which MAC addresses are reachable through which PE devices, facilitating Layer 2 forwarding across an IP or MPLS core.
* BGP Extensions for EVPN:BGP is extended with new address families (e.g., EVPN NLRI) to carry both MAC and IP address information, allowing for scalable and efficient multi-tenant network solutions.
Juniper Reference:
* Junos EVPN Configuration: Juniper uses BGP as the control plane for EVPN to exchange MAC and IP route information between different data center devices.
NEW QUESTION # 69
In OSPF, what is the function of the Link-State Database (LSDB)?
- A. To log changes in network topology.
- B. To store OSPF routing tables.
- C. To keep the topology structure of the network.
- D. To maintain a list of OSPF neighbors.
Answer: C
NEW QUESTION # 70
What is the primary use of Martian addresses in network routing?
- A. To identify addresses that should be excluded from routing.
- B. To create a backup routing plan.
- C. To configure virtual IP addresses for load balancing.
- D. To define addresses used for multicasting.
Answer: A
NEW QUESTION # 71
During a BGP Graceful Restart, what happens to the routes learned from the restarting neighbor?
- A. Their metric is increased to prevent their use.
- B. They are immediately removed from the routing table.
- C. They are advertised to other BGP neighbors.
- D. They are marked as stale but kept in the routing table.
Answer: D
NEW QUESTION # 72
What are three correct layer names used in legacy hierarchical network design? (Choose three.)
- A. Function layer
- B. Modular layer
- C. Core layer
- D. Access layer
- E. Aggregation layer
Answer: C,D,E
Explanation:
Inlegacy hierarchical network design, three key layers are used to create a scalable and structured network:
Step-by-Step Breakdown:
* Access Layer:
* The access layer is where end devices, such as computers and IP phones, connect to the network.
It typically involves switches that provide connectivity for devices at the edge of the network.
* Aggregation Layer (Distribution Layer):
* The aggregation layer (also called the distribution layer) aggregates traffic from multiple access layer devices and applies policies such as filtering and QoS. It also provides redundancy and load balancing.
* Core Layer:
* The core layer provides high-speed connectivity between aggregation layer devices and facilitates traffic within the data center or between different network segments.
Juniper Reference:
* Legacy Hierarchical Design: Juniper networks often follow the traditional three-layer design (Access, Aggregation, and Core) to ensure scalability and high performance.
NEW QUESTION # 73
What is the main advantage of using MACsec?
- A. It allows for the use of longer cable runs.
- B. It provides Layer 2 encryption for data confidentiality and integrity.
- C. It increases the speed of the network.
- D. It creates multiple virtual networks over a single physical infrastructure.
Answer: B
NEW QUESTION # 74
A generated route is configured under which hierarchy?
- A. [edit policy-options]
- B. [edit routing-options]
- C. [edit protocols]
- D. [edit routing-instance]
Answer: B
Explanation:
Agenerated routein Junos OS is configured under the[edit routing-options]hierarchy.
Step-by-Step Breakdown:
* Generated Routes:A generated route is created based on the presence of more specific routes in the routing table. It acts as a summary route and is generated when any of its contributing routes are active.
This is commonly used to create aggregate routes in OSPF, BGP, or other protocols.
* Configuration Hierarchy:The configuration for generated routes is placed under[edit routing-options]
, where other static and routing policies are also defined.
* Command Example:
set routing-options generate route 10.10.0.0/16
Juniper Reference:
* Routing Options: Juniper routers use the routing-options hierarchy to configure generated routes and other static routing behaviors.
NEW QUESTION # 75
What is the primary purpose of MAC address filtering on a switch?
- A. To distribute traffic evenly across multiple links.
- B. To prevent unauthorized devices from accessing the network.
- C. To limit the rate of incoming packets.
- D. To control the flow of encrypted data.
Answer: B
NEW QUESTION # 76
What is the behavior of the default export policy for OSPF?
- A. Forward all routes.
- B. Redistribute all routes.
- C. Reject all routes.
- D. Accept all routes.
Answer: C
Explanation:
In Junos, thedefault export policyforOSPFis toreject all routesfrom being exported.
Step-by-Step Breakdown:
* Default Export Policy:By default,OSPFin Junos does not export any routes to other routing protocols or neighbors. This is a safety mechanism to prevent unintended route advertisements.
* Custom Export Policies:
* If you need to export routes, you must create a customexport policythat explicitly defines which routes to advertise.
* Example: You can create an export policy to redistribute static or connected routes into OSPF.
Juniper Reference:
* OSPF Export Behavior: In Juniper devices, the default policy for OSPF is to reject route advertisements unless explicitly configured otherwise through custom policies.
NEW QUESTION # 77
What does filter-based forwarding in networking typically allow?
- A. Forwarding decisions based on MAC addresses
- B. Load balancing across multiple CPUs
- C. Aggregation of multiple routes into a single entry
- D. Routing decisions based on extended criteria like packet headers
Answer: D
NEW QUESTION # 78
In configuring load balancing on a network router, which aspect is most crucial?
- A. The encryption protocol used
- B. The use of aggregate routes
- C. The selection of multiple equal-cost paths
- D. The number of routing tables
Answer: C
NEW QUESTION # 79
Exhibit:
Referring to the exhibit, at which interval will the interface be considered down if no hello packets are received?
- A. 2000 milliseconds
- B. 400 seconds
- C. 400 milliseconds
- D. 2000 seconds
Answer: A
Explanation:
The exhibit shows the configuration ofBidirectional Forwarding Detection (BFD)for OSPF on interface xe-
0/0/4.0, with the following parameters:
* minimum-interval: 400 milliseconds
* multiplier: 5
Step-by-Step Breakdown:
* BFD Liveness Detection:BFD is used to detect link failures at sub-second intervals, providing faster convergence times for routing protocols like OSPF. Theminimum-intervalis the time between BFD control packets (in milliseconds), and themultiplierindicates how many missed BFD packets trigger a failure.
* Calculating Failure Detection Time:The failure detection interval is calculated as:
Failure Interval=minimum-interval×multiplier\text{Failure Interval} = \text{minimum-interval} \times \text
{multiplier}Failure Interval=minimum-interval×multiplier
In this case:
400 milliseconds×5=2000 milliseconds(2seconds)400 \, \text{milliseconds} \times 5 = 2000 \, \text
{milliseconds} (2 seconds)400milliseconds×5=2000milliseconds(2seconds)
* Conclusion:If no BFD control packets are received within2000 milliseconds (2 seconds), the interface will be considered down, triggering OSPF to recalculate routes.
Juniper Reference:
* BFD Configuration: BFD parameters such as minimum-interval and multiplier are used to fine-tune the failure detection time for faster convergence.
NEW QUESTION # 80
What statement is true about load-balancing?
- A. Load balancing on Juniper devices is processed per-flow.
- B. Load balancing on Juniper devices is processed per-packet.
- C. Load balancing is only supported by dynamic routing protocols.
- D. Load balancing is only supported after applying an advanced license.
Answer: A
NEW QUESTION # 81
When troubleshooting an OSPF neighborship, you notice that the router stopped at the ExStart state. What is the cause of this result?
- A. There is an area ID mismatch.
- B. The priority is set to 255.
- C. There is an interval timing mismatch.
- D. There is an MTU mismatch.
Answer: D
Explanation:
When an OSPF (Open Shortest Path First) neighborship is stuck in the ExStart state, it usually points to a mismatch in Maximum Transmission Unit (MTU) settings between two routers trying to establish the adjacency. The ExStart state is where OSPF routers negotiate the master-slave relationship and exchange DBD (Database Description) packets.
Step-by-Step Breakdown:
* OSPF Neighbor States: OSPF goes through several states to establish an adjacency with a neighbor:
* Down: No hello packets have been received.
* Init: Hello packets are received, but bidirectional communication isn't confirmed.
* 2-Way: Bidirectional communication is established.
* ExStart: The routers are negotiating who will be the master and who will be the slave, and begin to exchange DBD packets.
* Exchange: The routers start exchanging the database information.
* Loading: The routers process the Link-State Advertisements (LSAs).
* Full: The adjacency is fully established.
* MTU Mismatch Issue:During the ExStart state, both OSPF routers must agree on their MTU values. If there is an MTU mismatch between the two routers, OSPF neighbors will fail to move from the ExStart to the Exchange state. The router with the larger MTU setting will not accept DBD packets from the router with a smaller MTU because the packets may exceed the smaller MTU size.
In Juniper devices, this behavior can be identified by examining the MTU settings using the show interfaces command and ensuring both routers have matching MTU configurations. To resolve this issue, either match the MTU settings on both routers or configure OSPF to ignore MTU mismatches using the command set protocols ospf ignore-mtu.
Juniper Reference:
* Junos Command: show ospf neighbor helps diagnose neighbor states.
* MTU Adjustment: set interfaces <interface-name> mtu <size> can be used to set the MTU values correctly.
NEW QUESTION # 82
Which two statements are correct about BGP? (Choose two.)
- A. EBGP sessions are typically established between router loopback interfaces.
- B. IBGP peers do not advertise routes learned from IBGP peers to other IBGP peers.
- C. IBGP sessions are typically established between physical router interfaces.
- D. EBGP uses the AS path to avoid loops.
Answer: B,D
NEW QUESTION # 83
Which statement is correct about the BGP AS path when advertising routes?
- A. The order of the AS path is only significant in IBGP.
- B. The local AS number is added to the beginning of the AS path.
- C. The order of the AS path is not significant.
- D. The local AS number is added to the end of the AS path.
Answer: B
Explanation:
The BGPAS (Autonomous System) pathattribute is crucial in path selection and loop prevention. Each BGP router appends itslocal AS numberto the beginning of the AS path when it advertises a route to an external BGP (eBGP) peer.
Step-by-Step Breakdown:
* AS Path Attribute:The AS path is a sequence of AS numbers that a route has traversed to reach a destination. Each AS adds its number to the front of the path, allowing BGP to track the route's history.
* Why the Local AS is Added at the Beginning:When advertising a route to an eBGP neighbor, a BGP router adds its own AS number to the beginning of the AS path. This ensures that the AS path reflects the route's journey accurately from the origin to the destination, and prevents loops in BGP. If the route returns to the same AS, the router will detect its AS number in the path and reject the route, preventing routing loops.
* Order of the AS Path:The order is significant because BGP uses it to select the best path. A shorter AS path is preferred, as it indicates fewer hops between the source and destination.
Juniper Reference:
* AS Path Attribute: Junos devices append the local AS at the start of the AS path before advertising the route to an external peer.
NEW QUESTION # 84
What is a common issue to check for when troubleshooting a LAG not forming correctly?
- A. Overutilization of CPU resources
- B. Excessive broadcast traffic
- C. Identical IP addresses on all LAG interfaces
- D. Mismatched VLAN configurations
Answer: D
NEW QUESTION # 85
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