Practice Free JN0-280 Exam Online Questions
Question #1
When evaluating BGP routes, what will be evaluated first?
- A . The local preference value
- B . The AS path
- C . The MED value
- D . The origin value
Correct Answer: A
A
Explanation:
In BGP (Border Gateway Protocol), when evaluating multiple routes to the same destination, the first attribute that is considered is the local preference value. The local preference is a BGP attribute used to influence outbound routing decisions within an Autonomous System (AS).
Step-by-Step Breakdown:
Local Preference:
The local preference attribute is used to determine which path is preferred for traffic leaving the AS.
The higher the local preference value, the more preferred the route.
BGP Path Selection:
The BGP path selection process evaluates the following attributes in this order:
Local Preference (higher is preferred)
AS Path (shorter is preferred)
Origin (IGP > EGP > incomplete)
MED (Multi-Exit Discriminator) (lower is preferred)
Juniper
Reference: BGP Path Selection: In Junos, the local preference attribute is the first to be evaluated when determining the best path for outbound traffic.
A
Explanation:
In BGP (Border Gateway Protocol), when evaluating multiple routes to the same destination, the first attribute that is considered is the local preference value. The local preference is a BGP attribute used to influence outbound routing decisions within an Autonomous System (AS).
Step-by-Step Breakdown:
Local Preference:
The local preference attribute is used to determine which path is preferred for traffic leaving the AS.
The higher the local preference value, the more preferred the route.
BGP Path Selection:
The BGP path selection process evaluates the following attributes in this order:
Local Preference (higher is preferred)
AS Path (shorter is preferred)
Origin (IGP > EGP > incomplete)
MED (Multi-Exit Discriminator) (lower is preferred)
Juniper
Reference: BGP Path Selection: In Junos, the local preference attribute is the first to be evaluated when determining the best path for outbound traffic.
Question #2
What is a key characteristic of traditional multi-tier data center architectures?
- A . They primarily use a flat network design.
- B . They consist of a modular, scalable design.
- C . They are organized in a hierarchical model with distinct layers.
- D . They exclusively use Layer 3 routing.
Correct Answer: C
Question #3
In OSPF, what is the function of the Link-State Database (LSDB)?
- A . To store OSPF routing tables.
- B . To maintain a list of OSPF neighbors.
- C . To keep the topology structure of the network.
- D . To log changes in network topology.
Correct Answer: C
Question #4
What are two requirements for an IP fabric? (Choose two.)
- A . a Layer 3 routing protocol
- B . a single connection between each spine and leaf
- C . a single connection between each leaf
- D . a Layer 2 switching protocol
Correct Answer: A, B
A, B
Explanation:
An IP fabric is a network architecture commonly used in data centers to provide scalable, high-throughput connectivity using a spine-leaf topology.
Step-by-Step Breakdown:
Layer 3 Routing Protocol:
An IP fabric relies on a Layer 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 to every spine switch with 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.
A, B
Explanation:
An IP fabric is a network architecture commonly used in data centers to provide scalable, high-throughput connectivity using a spine-leaf topology.
Step-by-Step Breakdown:
Layer 3 Routing Protocol:
An IP fabric relies on a Layer 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 to every spine switch with 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.
Question #5
Generated routes in a network are mainly used to:
- A . Reduce the overall size of the routing table.
- B . Manually configure specific network routes.
- C . Automatically create a route when a specified condition is met.
- D . Summarize external routes into the network.
Correct Answer: C
Question #6
When configuring OSPF, what is the purpose of defining areas?
- A . To specify different encryption methods.
- B . To control route advertisement and manage traffic.
- C . To assign different IP address ranges.
- D . To provide network redundancy.
Correct Answer: B
Question #7
Which statement is correct about the OSPF link-state database?
- A . Each router within the same area must maintain a unique copy of the link-state database.
- B . Each router within the same area must maintain an identical copy of the link-state database.
- C . Each router within the OSPF domain must maintain a unique copy of the link-state database.
- D . Each router within the OSPF domain must maintain an identical copy of the link-state database.
Correct Answer: B
Question #8
A switch receives a frame with a MAC address of FF-FF-FF-FF-FF-FF.
Which action will the switch take on this frame?
- A . It will flood it out of all interfaces, except for the ingress interface.
- B . It will flood it out of all interfaces, except for the directly connected VLAN.
- C . It will flood it out of all interfaces, except for the next-hop interface.
- D . It will flood it out of all interfaces.
Correct Answer: A
A
Explanation:
A MAC address of FF-FF-FF-FF-FF-FF is the Ethernet broadcast address. When a switch receives a frame with this destination MAC address, it is required to forward the frame to all interfaces except the one it was received on.
Step-by-Step Breakdown: Broadcast Frame Handling:
When a frame with the broadcast MAC address is received, the switch will flood it out of all active ports that belong to the same VLAN as the incoming frame. The broadcast frame is not sent back out of the ingress interface (the interface where the frame was originally received).
Purpose of Flooding:
Broadcasting is used to ensure that the frame reaches all devices within the broadcast domain (all devices within the same VLAN), which may not have a specific entry for the MAC address in their MAC address table.
Juniper
Reference: Layer 2 Frame Forwarding: Juniper switches flood broadcast frames to all ports in the same VLAN, except the port the frame was received on.
A
Explanation:
A MAC address of FF-FF-FF-FF-FF-FF is the Ethernet broadcast address. When a switch receives a frame with this destination MAC address, it is required to forward the frame to all interfaces except the one it was received on.
Step-by-Step Breakdown: Broadcast Frame Handling:
When a frame with the broadcast MAC address is received, the switch will flood it out of all active ports that belong to the same VLAN as the incoming frame. The broadcast frame is not sent back out of the ingress interface (the interface where the frame was originally received).
Purpose of Flooding:
Broadcasting is used to ensure that the frame reaches all devices within the broadcast domain (all devices within the same VLAN), which may not have a specific entry for the MAC address in their MAC address table.
Juniper
Reference: Layer 2 Frame Forwarding: Juniper switches flood broadcast frames to all ports in the same VLAN, except the port the frame was received on.
Question #9
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.
Correct Answer: B, C
B, C
Explanation:
EVPN-VXLAN is 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.
B, C
Explanation:
EVPN-VXLAN is 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 #10
You are creating an IP fabric underlay and want to use OSPF as your routing protocol.
In this scenario, which statement is correct?
- A . All leaf devices must be configured in separate OSPF areas.
- B . All leaf and spine devices must be the same model to ensure the proper load-balancing behavior.
- C . Interface speeds should be the same throughout the fabric to ensure that all links are utilized.
- D . All spine devices must use the same router ID.
Correct Answer: C
C
Explanation:
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:
C
Explanation:
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:
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.