Easily To Pass New Juniper JN0-281 Dumps with 197 Questions
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Juniper JN0-281 Exam Syllabus Topics:
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NEW QUESTION # 72
In a Spine/Leaf IP-Fabric architecture, what is the primary role of the leaf switches?
- A. To manage the overall data center network.
- B. To interconnect different data centers.
- C. To provide direct connectivity to servers.
- D. To perform deep packet inspection.
Answer: C
NEW QUESTION # 73
Referring to the exhibit, which statement is correct?
- A. The default VLAN is a user defined VLAN name.
- B. The ge-0/0/0 interface has been explicitly assigned to a VLAN named default.
- C. The ge-0/0/12 interfaces is an access port.
- D. The asterisk indicates that the interface is active.
Answer: D
NEW QUESTION # 74
Referring to the exhibit, why are the BGP routes hidden?
- A. There are too many hops to the destination.
- B. The BGP next hop is unreachable.
- C. Load balancing is not enabled.
- D. Other routes are selected because of better metrics.
Answer: B
Explanation:
In the exhibit, the BGP routes are marked as hidden. This typically happens when the routes are not considered valid for use, but they remain in the routing table for reference. One common reason for BGP routes being hidden is that the next hop for these routes is unreachable.
Step-by-Step Breakdown:
BGP Next Hop:
In BGP, when a route is received from a neighbor, the next hop is the IP address that must be reachable for the route to be used. If the next hop is unreachable (i.e., the router cannot find a path to the next-hop IP), the route is marked as hidden. Analyzing the Exhibit:
The exhibit shows that the BGP next hop for all hidden routes is 10.4.4.4. If this IP is unreachable, the BGP routes from that neighbor will not be considered valid, even though they appear in the routing table.
Verification:
Use the command show route 10.4.4.4 to check if the next-hop IP is reachable.
If the next-hop is not reachable, the BGP routes will be hidden. Resolving the next-hop reachability issue (e.g., fixing an IGP route or an interface) will allow the BGP routes to become active. Juniper Reference: Junos Command: show route hidden displays routes that are not considered for forwarding. Troubleshooting: Check the next hop reachability for hidden BGP routes using show route <next-hop>.
NEW QUESTION # 75
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 order of the AS path is not significant.
- C. The local AS number is added to the end of the AS path.
- D. The local AS number is added to the beginning of the AS path.
Answer: D
Explanation:
The BGP AS (Autonomous System) path attribute is crucial in path selection and loop prevention.
Each BGP router appends its local AS number to 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 # 76
Which statement is correct about the OSPF link-state database?
- A. Each router within the OSPF domain must maintain an identical copy of the link-state database.
- B. Each router within the same area must maintain a unique copy of the link-state database.
- C. Each router within the same area must maintain an identical copy of the link-state database.
- D. Each router within the OSPF domain must maintain a unique copy of the link-state database.
Answer: C
NEW QUESTION # 77
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, the default export policy for OSPF is to reject all routes from being exported.
Step-by-Step Breakdown:
Default Export Policy:
By default, OSPF in 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 custom export policy that 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 # 78
Which statement is correct about OSPF?
- A. OSPF is a path-vector protocol
- B. OSPF is link-state protocol
- C. OSPF is a distance-vector protocol
- D. OSPF is a device-state protocol
Answer: B
NEW QUESTION # 79
What is the primary purpose of an IRB Layer 3 interface?
- A. to provide load balancing
- B. to provide a default VLAN ID
- C. to provide port security
- D. to provide inter-VLAN routing
Answer: D
Explanation:
The primary purpose of an IRB (Integrated Routing and Bridging) interface is to enable inter-VLAN routing in a Layer 3 environment. An IRB interface in Junos combines the functionality of both Layer 2 bridging (switching) and Layer 3 routing, allowing devices in different VLANs to communicate with each other.
Step-by-Step Breakdown:
VLANs and Layer 2 Switching:
Devices within the same VLAN can communicate directly through Layer 2 switching. However, communication between devices in different VLANs requires Layer 3 routing.
IRB Interface for Inter-VLAN Routing:
The IRB interface provides a Layer 3 gateway for each VLAN, enabling routing between VLANs. Without an IRB interface, devices in different VLANs would not be able to communicate.
Configuration:
In Juniper devices, the IRB interface is configured by assigning Layer 3 IP addresses to it. These IP addresses serve as the default gateway for devices in different VLANs. Example configuration:
set interfaces irb unit 0 family inet address 192.168.1.1/24 set vlans vlan-10 l3-interface irb.0 This allows VLAN 10 to use the IRB interface for routing.
Juniper
Reference: IRB Use Case: Inter-VLAN routing is essential in data centers where multiple VLANs are deployed, and Juniper's EX and QFX series switches support IRB configurations for this purpose.
NEW QUESTION # 80
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 spine devices must use the same router I
- B. All leaf devices must be configured in separate OSPF areas.
- C. All leaf and spine devices must be the same model to ensure the proper load-balancing behavior.
- D. Interface speeds should be the same throughout the fabric to ensure that all links are utilized.
Answer: D
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.
NEW QUESTION # 81
Which of the following is an important consideration when configuring BFD?
- A. Setting a very high multiplier to avoid false positives
- B. Using the same BFD interval on all devices in the network
- C. Adjusting the BFD interval and multiplier according to network needs
- D. Disabling all other failure detection mechanisms
Answer: C
NEW QUESTION # 82
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. An encapsulation of the original packet is required to transport the packet across the network.
- C. BGP provides the control plane within the overlay network.
- D. OSPF provides the control plane within the overlay network.
Answer: 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.
NEW QUESTION # 83
What statement is true about load-balancing?
- A. Load balancing is only supported after applying an advanced license.
- B. Load balancing is only supported by dynamic routing protocols.
- C. Load balancing on Juniper devices is processed per-packet.
- D. Load balancing on Juniper devices is processed per-flow.
Answer: D
NEW QUESTION # 84
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 # 85
Exhibit:
Referring to the exhibit, which next hop will be preferred in the routing table?
- A. Both next hops will be preferred.
- B. Next hop IP address 172.25.20.254 will be preferred.
- C. Neither next hop will be preferred.
- D. Next hop IP address 172.25.20.200 will be preferred.
Answer: D
Explanation:
In the exhibit, we see a static route configuration with two possible next hops for the default route (0.0.0.0/0):
next-hop 172.25.20.254 with the default preference of 7.
qualified-next-hop 172.25.20.200 with a preference of 6.
Step-by-Step Breakdown:
Preference Value:
In Junos OS, the preference value is used to determine which route should be preferred in the routing table. The lower the preference value, the higher the priority for the route.
Comparison:
In this case:
The next hop 172.25.20.254 has a preference of 7.
The qualified-next-hop 172.25.20.200 has a preference of 6.
Preferred Next Hop:
Since 172.25.20.200 has a lower preference (6) compared to 172.25.20.254 (7), it will be the preferred next hop in the routing table, assuming both next hops are reachable. Juniper Reference: Qualified Next Hop: In Junos, static routes with multiple next-hop options are selected based on the preference value, with the lower value being preferred.
NEW QUESTION # 86
What is the definition of a trunk interface on a switch?
- A. An interface that carries high bandwidth.
- B. An interface that connects directly to powerful servers.
- C. An interface that carries multiple VLANs.
- D. An interface that carries excess traffic.
Answer: C
Explanation:
A trunk interface on a switch is used to carry traffic for multiple VLANs between switches or between a switch and another network device, like a router. Trunk interfaces use 802.1Q tagging to identify which VLAN the traffic belongs to.
Step-by-Step Breakdown:
Trunk Ports:
Trunk ports are typically used for inter-switch links or switch-to-router links where multiple VLANs need to be carried over the same physical connection.
VLAN traffic is tagged with a VLAN ID to ensure that it is properly identified as it crosses the trunk link.
802.1Q VLAN Tagging:
Trunk ports use 802.1Q to tag Ethernet frames with the VLAN ID. This ensures that frames are correctly forwarded to the appropriate VLANs on the other side of the trunk. Juniper Reference: Trunk Interface Configuration: In Juniper switches, trunk ports are configured to carry tagged traffic for multiple VLANs, which is essential for interconnecting multiple network segments.
NEW QUESTION # 87
Which statement is correct about an IP fabric?
- A. The entire IP fabric is one large broadcast domain.
- B. Loop prevention is provided by the underlying spanning tree protocol used.
- C. Load sharing is provided by the routing protocol used.
- D. Transit traffic is passed through the network based on the original frame's destination MAC address.
Answer: C
NEW QUESTION # 88
What is the primary role of an IRB interface in a VLAN configuration?
- A. To encrypt VLAN traffic.
- B. To filter VLAN traffic based on MAC addresses.
- C. To provide a gateway for VLAN traffic.
- D. To prioritize VLAN traffic.
Answer: C
NEW QUESTION # 89
What is the primary function of a VLAN?
- A. To encrypt network traffic.
- B. To provide a routing mechanism between different networks.
- C. To segment a network into multiple broadcast domains.
- D. To control network traffic based on MAC addresses.
Answer: C
NEW QUESTION # 90
Referring to the exhibit, how many stages are in this IP fabric?
- A. 0
- B. 1
- C. 2
- D. 3
Answer: C
NEW QUESTION # 91
Which statement about switches is correct?
- A. Each port is in a unique broadcast domain by default.
- B. Each port is a member of VLAN 2 by default.
- C. All ports reside in the same collision domain.
- D. Every port is in a unique collision domain.
Answer: D
Explanation:
Each port on a modern switch creates a separate collision domain. This allows multiple devices to communicate simultaneously without collisions on different ports.
Step-by-Step Breakdown:
Collision Domain:
A collision domain is a network segment where data packets can collide if two devices send packets simultaneously.
On a switch, each port creates a separate collision domain, so collisions only occur if two devices connected to the same port (through a hub, for instance) try to send data at the same time.
Switches vs Hubs:
Unlike hubs, which have one large collision domain, switches isolate collisions to individual ports, improving performance.
Juniper Reference:
Switch Port Behavior: In Juniper switches, each port operates in its own collision domain, enhancing network efficiency by reducing the chances of packet collisions.
NEW QUESTION # 92
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 source MAC address of frames traversing the network.
- D. It stores the destination MAC address of frames traversing the network.
Answer: C
NEW QUESTION # 93
What information in the Ethernet header is used to populate the bridging table?
- A. destination address
- B. type
- C. source address
- D. protocol
Answer: C
Explanation:
The source MAC address in the Ethernet header is used to populate the bridging table (also called the MAC address table) on a switch. When a frame arrives at a switch, the switch examines the source MAC address and records it along with the ingress port in its MAC address table.
Step-by-Step Breakdown:
Learning Process:
When an Ethernet frame arrives on a switch port, the switch looks at the source MAC address and adds this MAC address to the MAC table along with the port it was received on. This process is called MAC learning.
Purpose:
The switch uses this information to determine the correct port to send frames destined for that MAC address in future transmissions, thus ensuring efficient Layer 2 forwarding. Juniper Reference: Ethernet Switching: Juniper switches use source MAC addresses to build and maintain the MAC address table, which is essential for Layer 2 switching.
NEW QUESTION # 94
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 import policy within OSPF.
- B. Apply the policy as an export policy within BGP.
- C. Apply the policy as an import policy within BGP.
- D. Apply the policy as an export policy within OSPF.
Answer: B
Explanation:
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 <group-name> 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.
NEW QUESTION # 95
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