Juniper JN0-280 Online Practice Questions and Exam Preparation

Juniper JN0-280 Online Questions & Answers

• Question 11:

  In OSPF, which term refers to routers that have interfaces in multiple areas?

  A. Internal Routers
  B. Backbone Routers
  C. Area Border Routers (ABRs)
  D. Autonomous System Boundary Routers (ASBRs)
  C. Area Border Routers (ABRs)

• Question 12:

  You want to enable a Junos device to support aggregated Ethernet interfaces. In this scenario, which configuration hierarchy would you use?

  A. [edit switch-options]
  B. [edit system]
  C. [edit interfaces]
  D. [edit chassis]
  D. [edit chassis]

  ---

  Explanation/Reference:

  To configure aggregated Ethernet (AE) interfaces on a Junos device, the configuration is done under the [edit chassis] hierarchy.

  Step-by-Step Breakdown:

  Chassis Configuration:The chassis configuration is responsible for enabling the hardware to support Link 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: The chassis hierarchy is used to allocate and manage hardware resources for aggregated Ethernet interfaces in Juniper devices.

• Question 13:

  Which two statements are correct about aggregate routes and generated routes? (Choose two.)

  A. An aggregate route does not have a forwarding next hop.
  B. An aggregate route has a forwarding next hop.
  C. A generated route has a forwarding next hop.
  D. A generated route does not have a forwarding next hop.
  A. An aggregate route does not have a forwarding next hop.
  C. A generated route has a forwarding next hop.

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  Explanation/Reference:

  Aggregate routesand generated routes are used to create summarized routes in Junos, but they behave differently in terms of forwarding.

  Step-by-Step Breakdown:

  Aggregate Routes:

  An aggregate route summarizes a set of more specific routes, but it does not have a direct forwarding next hop. Instead, it points to the more specific routes for actual packet forwarding.

  Generated Routes:

  A generated route also summarizes specific routes, but it has a forwarding next hop that is determined based on the availability of contributing routes. The generated route can be used to directly forward traffic.

  Juniper Reference:

  Aggregate and Generated Routes: In Junos, aggregate routes rely on more specific routes for forwarding, while generated routes can forward traffic directly based on their next-hop information.

• Question 14:

  In a traditional multi-tier architecture, which layer is responsible for aggregating access layers and providing connectivity to the core layer?

  A. Core Layer
  B. Distribution Layer
  C. Access Layer
  D. Edge Layer
  B. Distribution Layer

• Question 15:

  Leaf and spine data centers are used to better accommodate which type of traffic?

  A. north-east
  B. east-west
  C. north-west
  D. south-east
  B. east-west

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  Explanation/Reference:

  In modern data centers, the shift toward leaf-spine architectures is driven by the need to handle increased east- west traffic, which is traffic between servers within the same data center. Unlike traditional hierarchical data center designs,

  where most traffic was "north-south" (between users and servers), modern applications often involve server-to-server communication (east-west) to enable services like distributed databases, microservices, and virtualized workloads.

  Leaf-Spine Architecture:

  Leaf Layer: This layer consists of switches that connect directly to servers or end-host devices. These switches serve as the access layer. Spine Layer: The spine layer comprises high-performance switches that provide interconnectivity

  between leaf switches. Each leaf switch connects to every spine switch, creating a non-blocking fabric that optimizes traffic flow within the data center.

  East-West Traffic Accommodation:

  In traditional three-tier architectures (core, aggregation, access), traffic had to traverse multiple layers, leading to bottlenecks when servers communicated with each other. Leaf-spine architectures address this by creating multiple equal-cost

  paths between leaf switches and the spine. Since each leaf switch connects directly to every spine switch, the architecture facilitates quick, low-latency communication between servers, which is essential for east-west traffic flows.

  Juniper's Role:Juniper Networks provides a range of solutions that optimize for east-west traffic in a leaf- spine architecture, notably through:

  QFX Series Switches: Juniper's QFX series switches are designed for the leaf and spine architecture, delivering high throughput, low latency, and scalability to accommodate the traffic demands of modern data centers. EVPN-VXLAN: Juniper

  uses EVPN-VXLAN to create a scalable Layer 2 and Layer 3 overlay network across the data center. This overlay helps enhance east-west traffic performance by enabling network segmentation and workload mobility across the entire fabric.

  Key Features That Support East-West Traffic:

  Equal-Cost Multipath (ECMP): ECMP enables the use of multiple paths between leaf and spine switches, balancing the traffic and preventing any one path from becoming a bottleneck. This is crucial in handling the high volume of east-west

  traffic.

  Low Latency: Spine switches are typically high-performance devices that minimize the delay between leaf switches, which improves the efficiency of server-to-server communications. Scalability: As the demand for east-west traffic grows,

  adding more leaf and spine switches is straightforward, maintaining consistent performance without redesigning the entire network.

  In summary, the leaf-spine architecture is primarily designed to handle the increase in east-west traffic within data centers, and Juniper provides robust solutions to enable this architecture through its switch platforms and software solutions

  like EVPN-VXLAN.

• Question 16:

  Which two statements are correct about rules for EBGP and IBGP? (Choose two.)

  A. EBGP peers have a TTL of 1, while IBGP peers have a TTL of 255.
  B. EBGP peers have a TTL of 255, while IBGP peers have a TTL of 1.
  C. EBGP routes are more preferred than IBGP routes.
  D. IBGP routes are more preferred than EBGP routes.
  A. EBGP peers have a TTL of 1, while IBGP peers have a TTL of 255.
  C. EBGP routes are more preferred than IBGP routes.

  ---

  Explanation/Reference:

  EBGP (External BGP)and IBGP (Internal BGP) operate with different rules due to the nature of their relationships.

  Step-by-Step Breakdown:

  TTL Differences:

  EBGP: By default, EBGP peers have a TTL of 1, meaning they must be directly connected, or the TTL needs to be manually increased for multihop EBGP. IBGP: IBGP peers within the same AS have a TTL of 255, as they are expected to

  communicate over multiple hops within the AS.

  Preference for EBGP Routes:

  Routes learned via EBGP are typically preferred over IBGP routes. This is because EBGP routes are considered more reliable since they originate outside the AS, while IBGP routes are internal.

  Juniper Reference:

  BGP Configuration: The different handling of TTL and route preferences between EBGP and IBGP ensures proper route selection and security within Junos-based networks.

• Question 17:

  How does a layer 2 switch populate its bridge table?

  A. It stores the protocol number of frames traversing the network.
  B. It stores both the source and destination MAC addresses of frames traversing the network.
  C. It stores the destination MAC address of frames traversing the network.
  D. It stores the source MAC address of frames traversing the network.
  D. It stores the source MAC address of frames traversing the network.

• Question 18:

  Which statement is correct about a five-stage IP fabric topology?

  A. There is a maximum of five hops between any end-devices
  B. They are commonly referred to as interconnected data centers
  C. There is a maximum of three hops between any end-devices
  D. They are typically deployed in small to medium data centers
  A. There is a maximum of five hops between any end-devices

• Question 19:

  Which two statements about IBGP are correct? (Choose two.)

  A. By default, IBGP has a TTL of 1.
  B. IBGP uses AS path for loop prevention.
  C. By default, IBGP has a TTL of 255.
  D. IBGP uses full mesh for loop prevention.
  C. By default, IBGP has a TTL of 255.
  D. IBGP uses full mesh for loop prevention.

  ---

  Explanation/Reference:

  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 a TTL (Time to Live) value of 255 . This allows IBGP neighbors to communicate over multiple hops within the AS without requiring any additional configuration.

  Full Mesh Requirement:

  IBGP requires a logical full mesh between 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 unless route reflectors BGP or confederations are used.

  Juniper Reference:

  IBGP Full Mesh: Juniper recommends using route reflectors in large networks to simplify IBGP full- mesh requirements.

• Question 20:

  Which statement is correct about an IRB interface?

  A. An IRB interface switches traffic within the same VLAN.
  B. An IRB interface trunks together VLANs on different switches.
  C. An IRB interface is a physical Layer 3 interface that connects VLANs together.
  D. An IRB interface is a Layer 3 interface that can be used to route between VLANs.
  D. An IRB interface is a Layer 3 interface that can be used to route between VLANs.

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  Explanation/Reference:

  An IRB (Integrated Routing and Bridging) interface provides routing functionality between VLANs at Layer 3, allowing devices in different VLANs to communicate with each other.

  Step-by-Step Breakdown:

  IRB Functionality:

  The IRB interface enables routing between different VLANs by acting as a Layer 3 gateway. Traffic within the same VLAN is handled by Layer 2 switching, while traffic between VLANs is routed through the IRB interface.

  Layer 3 Routing Between VLANs:

  Each VLAN can be assigned an IP address on the IRB interface, which allows traffic to flow between VLANs based on Layer 3 IP routing.

  Juniper Reference:

  IRB Interface Configuration: Juniper supports IRB for inter-VLAN routing on devices like the EX and QFX series switches, facilitating Layer 3 communication in data centers.