Practice Free JN0-281 Exam Online Questions
Question #1
What protocol and port does BGP use for control plane communication?
- A . protocol TCP, port 179
- B . protocol UDP, port 179
- C . protocol TCP, port 159
- D . protocol UDP, port 159
Correct Answer: A
Question #2
What statement is true about load-balancing?
- A . Load balancing is only supported after applying an advanced license.
- B . Load balancing on Juniper devices is processed per-packet.
- C . Load balancing on Juniper devices is processed per-flow.
- D . Load balancing is only supported by dynamic routing protocols.
Correct Answer: C
Question #3
What are two device roles in a five-member Virtual Chassis? (Choose two.)
- A . PFE
- B . Control-board
- C . Line card
- D . Routing-engine
Correct Answer: C, D
C, D
Explanation:
In a Virtual Chassis (VC) configuration, multiple Juniper switches are interconnected to form a single logical device. Each member switch in the Virtual Chassis plays a specific role. Step-by-Step Breakdown:
Line Card Role:
Member switches acting as line cards provide additional ports for traffic forwarding but do not perform control or routing functions. These switches depend on the routing engine to handle control-plane tasks.
Routing Engine Role:
A switch in the routing-engine role is responsible for control-plane operations such as routing protocol management and control of the Virtual Chassis.
Virtual Chassis Roles:
Master Routing Engine: Handles control-plane functions and manages the entire Virtual Chassis.
Backup Routing Engine: Takes over if the master fails.
Line Card: Provides additional ports and handles data-plane operations. Juniper
Reference: Virtual Chassis: In a five-member Virtual Chassis, multiple switches act as line cards, while one or more switches are designated as the routing engines (master and backup).
C, D
Explanation:
In a Virtual Chassis (VC) configuration, multiple Juniper switches are interconnected to form a single logical device. Each member switch in the Virtual Chassis plays a specific role. Step-by-Step Breakdown:
Line Card Role:
Member switches acting as line cards provide additional ports for traffic forwarding but do not perform control or routing functions. These switches depend on the routing engine to handle control-plane tasks.
Routing Engine Role:
A switch in the routing-engine role is responsible for control-plane operations such as routing protocol management and control of the Virtual Chassis.
Virtual Chassis Roles:
Master Routing Engine: Handles control-plane functions and manages the entire Virtual Chassis.
Backup Routing Engine: Takes over if the master fails.
Line Card: Provides additional ports and handles data-plane operations. Juniper
Reference: Virtual Chassis: In a five-member Virtual Chassis, multiple switches act as line cards, while one or more switches are designated as the routing engines (master and backup).
Question #4
What is the default Junos behavior of access ports?
- A . Allow only untagged traffic
- B . Allow only tagged traffic
- C . Allow both tagged and untagged traffic
- D . Allow a maximum of 80 percent untagged traffic
Correct Answer: A
Question #5
Exhibit:
Referring to the exhibit, at which interval will the interface be considered down if no hello packets are received?
- A . 2000 seconds
- B . 400 milliseconds
- C . 400 seconds
- D . 2000 milliseconds
Correct Answer: D
D
Explanation:
The exhibit shows the configuration of Bidirectional 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. The minimum-interval is the time between BFD control packets (in milliseconds), and the multiplier indicates how many missed BFD packets trigger a failure.
Calculating Failure Detection Time:
The failure detection interval is calculated as:
Failure Interval=minimum-interval×multipliertext{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 within 2000 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.
D
Explanation:
The exhibit shows the configuration of Bidirectional 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. The minimum-interval is the time between BFD control packets (in milliseconds), and the multiplier indicates how many missed BFD packets trigger a failure.
Calculating Failure Detection Time:
The failure detection interval is calculated as:
Failure Interval=minimum-interval×multipliertext{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 within 2000 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.
Question #6
A generated route is configured under which hierarchy?
- A . [edit policy-options]
- B . [edit routing-instance]
- C . [edit routing-options]
- D . [edit protocols]
Correct Answer: C
C
Explanation:
A generated route in 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.
C
Explanation:
A generated route in 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.
Question #7
Which LSA types are associated with OSPF? (Choose three)
- A . Router LSA (Type 1)
- B . Network LSA (Type 2)
- C . Summary LSA (Type 3)
- D . External LSA (Type 5)
Correct Answer: ABC
Question #8
What are two characteristics of a typical EBGP underlay fabric? (Choose two.)
- A . Each device in an EBGP fabric will be configured in its own unique private AS.
- B . Each device in an EBGP fabric will be configured to be part of the same private AS.
- C . An EBGP fabric relies on an IGP to advertise loopback IPs.
- D . An EBGP fabric does not require an IGP to advertise loopback IPs.
Correct Answer: AD
Question #9
Which statement is correct about areas in OSPF?
- A . An OSPF area is used to segment Layer 2 broadcast domains.
- B . OSPF areas are used to isolate the effects of a broadcast storm.
- C . OSPF areas are used to reduce the size of the link-state database.
- D . An OSPF area is used to signify the autonomous system to which each device belongs.
Correct Answer: C
C
Explanation:
In OSPF (Open Shortest Path First), areas are used to segment a network into smaller, more manageable pieces to improve scalability. By dividing a network into areas, OSPF can reduce the size of the link-state database (LSDB), which helps routers process updates more efficiently.
Step-by-Step Breakdown:
Purpose of OSPF Areas:
OSPF areas allow for hierarchical routing within the OSPF domain. Routers in the same area have identical LSDBs, but routers in different areas do not exchange full link-state information. Instead, they exchange summarized routes, which reduces the LSDB size and CPU/memory usage.
Benefits:
Reducing the LSDB size improves scalability and ensures faster convergence in larger networks. Area 0 is the backbone area, and all other areas must connect to it, forming a hierarchical structure. Juniper
Reference: OSPF Configuration: Areas in OSPF are configured to optimize network performance by limiting the scope of link-state advertisements (LSAs) to within an area.
C
Explanation:
In OSPF (Open Shortest Path First), areas are used to segment a network into smaller, more manageable pieces to improve scalability. By dividing a network into areas, OSPF can reduce the size of the link-state database (LSDB), which helps routers process updates more efficiently.
Step-by-Step Breakdown:
Purpose of OSPF Areas:
OSPF areas allow for hierarchical routing within the OSPF domain. Routers in the same area have identical LSDBs, but routers in different areas do not exchange full link-state information. Instead, they exchange summarized routes, which reduces the LSDB size and CPU/memory usage.
Benefits:
Reducing the LSDB size improves scalability and ensures faster convergence in larger networks. Area 0 is the backbone area, and all other areas must connect to it, forming a hierarchical structure. Juniper
Reference: OSPF Configuration: Areas in OSPF are configured to optimize network performance by limiting the scope of link-state advertisements (LSAs) to within an area.
Question #10
Which two protocols can you use for a data center underlay network? (Choose two)
- A . EBGP
- B . OSPF
- C . VXLAN
- D . EVPN
Correct Answer: AB