Juniper JN0-280 Online Practice Questions and Exam Preparation

Juniper JN0-280 Online Questions & Answers

• Question 31:

  Referring to the exhibit, which two statements are correct about default BGP advertisements? (Choose two.)

  

  A. When routes advertised by router2 are received by the SP router, they will contain the next-hop address of router2.
  B. When routes advertised by router2 are received by the SP router, they will contain the next-hop address of router1.
  C. When routes advertised by the SP router are received by router2, they will contain the next-hop address of the SP router.
  D. When routes advertised by the SP router are received by router2, they will contain the next-hop address of router1.
  B. When routes advertised by router2 are received by the SP router, they will contain the next-hop address of router1.
  D. When routes advertised by the SP router are received by router2, they will contain the next-hop address of router1.

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  Explanation/Reference:

  The exhibit shows a BGP peering scenario between three routers: router1 and router2 are part of the same AS (AS65000), while the SP router is in a different AS (AS65101). This indicates an EBGP (External BGP) peering between the SP

  router and router1, and IBGP between router1 androuter2.

  Step-by-Step Breakdown:

  Next-Hop Behavior in BGP:

  IBGP: In IBGP, the next-hop address is not modified when advertising routes within the same AS. Thus, when router1 advertises routes learned from router2 to the SP router, it will keep the next-hop address of router1, not router2. EBGP: In

  EBGP, the next-hop address is modified. When router1 receives routes from the SP router, it will advertise them to router2 with the next-hop address of router1.

  Route Propagation:

  Routes received by router1 from router2 will be advertised to the SP router with router1 as the next hop.

  Similarly, routes advertised by the SP router will be passed on to router2, with router1 remaining as the next hop.

  Juniper Reference:

  BGP Next-Hop: Juniper's BGP implementations follow standard BGP next-hop behavior, where the next-hop is modified in EBGP but not in IBGP, ensuring proper route advertisement across autonomous systems.

• Question 32:

  What roles do the Designated Router (DR) and Backup Designated Router (BDR) play in OSPF?

  A. They redistribute routes between OSPF and non-OSPF networks.
  B. They are responsible for generating LSAs for external routes.
  C. They reduce the number of adjacencies on broadcast networks.
  D. They determine the shortest path first algorithm.
  C. They reduce the number of adjacencies on broadcast networks.

• Question 33:

  Which statement is about OSPF?

  A. OSPF is link-state protocol
  B. OSPF is a path-vector protocol
  C. OSPF is a distance-vector protocol
  D. OSPF is a device-state protocol
  A. OSPF is link-state protocol

• Question 34:

  Which statement is correct about a three-stage IP fabric underlay?

  A. Every ingress interface into the fabric is only two hops away from the egress interface.
  B. Every spine device can communicate directly with other spine devices.
  C. Every leaf device can communicate directly with other leaf devices.
  D. Every server that connects to a three-stage IP fabric must be multihomed.
  A. Every ingress interface into the fabric is only two hops away from the egress interface.

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  Explanation/Reference:

  In a three-stage IP fabric (also known as a Clos fabric), traffic between any two points (ingress to egress) in the fabric is only two hops away .

  Step-by-Step Breakdown:

  Three-Stage IP Fabric:

  Leaf Layer: Leaf switches connect directly to servers and edge devices.

  Spine Layer: Spine switches provide connectivity between leaf switches but do not connect to each other directly.

  Two-Hop Communication:In this architecture, every leaf switch is connected to every spine switch. Therefore, when a packet enters the fabric via an ingress leaf switch, it is forwarded to a spine switch, which then directs the packet to the

  correct egress leaf switch. This path always involves exactly two hops:

  Ingress leaf # Spine # Egress leaf.

  Benefits:This consistent two-hop path ensures predictable latency and makes the network highly scalable while maintaining low complexity.

  Juniper Reference:

  IP Fabric Architecture: This two-hop property of Clos fabrics is a hallmark of spine-leaf designs, as supported by Juniper's QFX and EX switches in data centers.

• Question 35:

  Which two statements are correct about EVPN-VXLAN overlay networking? (Choose two.)

  A. It is the only option to provide reachability between servers that reside in the same network segment in a data center.
  B. BGP provides the control plane within the overlay network.
  C. An encapsulation of the original packet is required to transport the packet across the network.
  D. OSPF provides the control plane within the overlay network.
  B. BGP provides the control plane within the overlay network.
  C. An encapsulation of the original packet is required to transport the packet across the network.

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  Explanation/Reference:

  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.

• Question 36:

  A routing policy has been created to advertise OSPF routes in BGP. Which statement is correct in this scenario?

  A. Apply the policy as an export policy within BGP.
  B. Apply the policy as an export policy within OSPF.
  C. Apply the policy as an import policy within BGP.
  D. Apply the policy as an import policy within OSPF.
  A. Apply the policy as an export policy within BGP.

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  Explanation/Reference:

  When advertising OSPF routes into BGP , the appropriate routing policy should be applied as an export policy in BGP.

  Step-by-Step Breakdown:

  OSPF to BGP Route Advertisement:Routes learned via OSPF (a dynamic IGP) need to be exported into BGP to be advertised to external BGP peers. In Junos OS, this is done using export policies . Export Policies in BGP:An export policy

  controls which routes are advertised out of a BGP session. In this scenario, the routing policy must be applied to BGP as an export policy to export the OSPF-learned routes to external BGP peers.

  Policy Configuration:Example configuration:

  set policy-options policy-statement EXPORT_OSPF term 1 from protocol ospf

  set policy-options policy-statement EXPORT_OSPF term 1 then accept

  set protocols bgp group export EXPORT_OSPF

  This policy ensures that only OSPF routes are exported into BGP.

  Juniper Reference:

  Routing Policy: Export policies are used in BGP to control route advertisements to peers, including those learned via OSPF.

• Question 37:

  In the Junos OS, which feature is used to create an alternate next hop with a unique preference for a static route?

  A. Preference
  B. Resolve
  C. Next-hop
  D. Qualified-next-hop
  D. Qualified-next-hop

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  Explanation/Reference:

  In Junos OS, the qualified-next-hop feature is used to specify an alternate next hop for a static route, along with a unique preference value.

  Step-by-Step Breakdown:

  Qualified-Next-Hop:A qualified-next-hop allows you to define multiple next hops for a static route, each with its own preference. This provides flexibility by allowing the router to choose the best available next hop based on reachability and

  preference.

  Use Case:If the primary next hop becomes unreachable, the router can automatically switch to the alternate next hop defined by the qualified-next-hop with a higher preference value.

  Command Example:

  set routing-options static route 10.10.10.0/24 qualified-next-hop 192.168.1.1 preference 5

  set routing-options static route 10.10.10.0/24 qualified-next-hop 192.168.1.2 preference 10

  Preference:The next hop with the lowest preference is chosen first. If it becomes unavailable, the router will use the higher preference next hop.

  Juniper Reference:

  Qualified-Next-Hop: This feature is used to configure backup or alternate next hops for static routes in Juniper devices.

• Question 38:

  When using spine and leaf fabric architectures, what is the role of each device? (Choose two.)

  A. Spine nodes are used for host connectivity.
  B. Spine nodes are used for transit to other leaf nodes.
  C. Leaf nodes are used for traffic to other leafs.
  D. Leaf nodes are used for host connectivity.
  B. Spine nodes are used for transit to other leaf nodes.
  D. Leaf nodes are used for host connectivity.

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  Explanation/Reference:

  In a spine-leaf fabric architecture , which is commonly used in data center designs, each device has a distinct role to ensure efficient and scalable network traffic flow.

  Step-by-Step Breakdown:

  Spine Nodes:

  The spine nodes form the backbone of the fabric and are responsible for transit traffic between leaf nodes . They connect to every leaf switch and provide multiple paths for traffic between leaf nodes, ensuring redundancy and load balancing.

  Leaf Nodes:

  The leaf nodes are used for host connectivity . These switches connect to servers, storage, or edge routers. They also connect to the spine switches to reach other leaf switches.

  Juniper Reference:

  Spine-Leaf Architecture: In Juniper's IP fabric designs, spine switches handle inter-leaf communication, while leaf switches manage host and endpoint connectivity.

• Question 39:

  What is the primary purpose of MAC address filtering on a switch?

  A. To control the flow of encrypted data.
  B. To limit the rate of incoming packets.
  C. To prevent unauthorized devices from accessing the network.
  D. To distribute traffic evenly across multiple links.
  C. To prevent unauthorized devices from accessing the network.

• Question 40:

  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. No traffic is traversing the LAG interfaces.
  C. The LAG interfaces are in a passive state.
  D. The LAG interfaces are in aggressive mode.
  A. No operational interfaces have been added to the LAG interfaces.

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  Explanation/Reference:

  In the exhibit, the ae0 and ae1 interfaces are in a link down state. This occurs when no physical interfaces (member interfaces) have been added to the LAG (Link Aggregation Group) interfaces, or the member interfaces are not operational.

  Step-by-Step Breakdown:

  LAG Configuration:A LAG interface (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 a down state, 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.