JN0-281試験問題集を使って一日でJNCIA-DC試験合格目指す（最新の197解答) [Q70-Q89]

JN0-281試験問題集を使って一日でJNCIA-DC試験合格目指す（最新の197解答)

JN0-281試験正確な問題集、学習ノートと理論

Juniper JN0-281 認定試験の出題範囲：

トピック	出題範囲
トピック 1	データセンタールーティングプロトコル BGP OSPF：このセクションでは、ネットワーク運用スペシャリストのスキルを評価し、OSPFプロトコルの動作と主要概念を網羅します。リンクステートデータベース、OSPFパケットタイプ、ルータIDなどの要素に加え、エリア内での隣接関係と指定ルータの動作についても解説します。次にBGPについて説明し、その基本動作、メッセージタイプ、属性、パス選択プロセスの概要を説明します。また、IBGPとEBGPの両方の役割についても解説します。最後に、ルーティングポリシーと各種ツールを使用してOSPFとBGPを設定、監視、トラブルシューティングする方法を復習します。
トピック 2	データセンターアーキテクチャ：このセクションでは、データセンターアーキテクトのスキルを評価し、様々なデータセンター設計に関する基礎知識を網羅します。従来の多層アーキテクチャに加え、スパインリーフ型トポロジを用いた最新のIPファブリックアーキテクチャも対象としています。また、トラフィック転送におけるレイヤー2およびレイヤー3の戦略、オーバーレイネットワークとアンダーレイネットワークの違いについても触れ、Ethernet VPN-Virtual Extensible LAN（EVPN-VXLAN）の概要と、データセンター環境におけるその基本的な目的と役割について説明します。
トピック 3	プロトコル非依存ルーティング：このセクションでは、ルーティングエンジニアのスキルを評価し、特定のプロトコルに依存しないルーティング機能を網羅します。スタティックルート、集約ルート、生成ルートに加え、Martianアドレスの概念も扱います。ルーティングインスタンスとルーティング情報ベース（RIB）グループに加え、ロードバランシングやフィルタベース転送といった技術についても解説します。これらのルーティングコンポーネントの設定、監視、トラブルシューティングについてもこのセクションで解説します。
トピック 4	レイヤー2スイッチングとVLAN：このセクションでは、ネットワークサポートエンジニアのスキルを評価し、Junos OSにおけるレイヤー2スイッチング操作の基本概念を網羅します。イーサネットスイッチングとブリッジングの概要を網羅し、レイヤー2ネットワークの機能について理解を深めます。また、ポートモード、VLANタグ付け方式、IRB（Integrated Routing and Bridging）の目的に焦点を当て、VLANの概念についても解説します。さらに、レイヤー2スイッチングとVLANの設定、監視、トラブルシューティングの方法を解説することで、実践的な側面も探求します。
トピック 5	高可用性：このセクションでは、データセンター信頼性エンジニアのスキルを評価し、ネットワークの継続的な可用性を確保するための戦略を網羅します。リンクアグリゲーショングループ（LAG）、グレースフルリスタート（GR）、双方向フォワーディング検出（BFD）、バーチャルシャーシといった機能が含まれます。また、これらの高可用性コンポーネントをそれぞれ設定、監視、トラブルシューティングし、耐障害性の高いネットワークパフォーマンスを維持する方法についての基本的な理解も求められます。

質問 # 70
Referring to the exhibit, which two statements are true? (Choose two.)

A. The BGP group is configured to attempt an EBGP peering session with 192.168.100.1.
B. The configuration will pass the commit check.
C. The configuration will not pass the commit check.
D. The BGP group is configured to attempt an EBGP peering session with 192.168.100.2.

正解：C、D

質問 # 71
What is an advantage of using BFD?

A. BFD built to handle the routing table of the entire Internet, and can safely redistribute it into OSPF.
B. BFD is so lightweight that each protocol will generate its own unique BFD session by default, to replace its own hello messages.
C. One BFD monitoring session can be used by multiple protocols.
D. BFD is built to handle the routing table of the entire Internet, unlike IGPS.

正解：C

質問 # 72
You want to enable a Junos device to support aggregated Ethernet interfaces. In this scenario, which configuration hierarchy would you use?

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

正解：D

解説：
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 <number>
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.

質問 # 73
You are troubleshooting a downed BGP session.

Referring to the exhibit, what is the cause of the problem?

A. The local peer has sent an Open message but not received one from the remote peer.
B. The local peer has sent an Update message but not received one from the remote peer.
C. The TCP session between the peers has not been established.
D. The UDP session between the peers has not been established.

正解：C

解説：
The BGP session in the exhibit shows the state as Connect, which indicates that the TCP session between the BGP peers has not been fully established.
Step-by-Step Breakdown:
BGP State "Connect":
The Connect state is the second stage in the BGP finite state machine (FSM). At this stage, BGP is trying to establish a TCP session with the peer, but the session has not yet been successfully established.
A successful TCP three-way handshake (SYN, SYN-ACK, ACK) is required before BGP can progress to the OpenSent state, where the peers exchange BGP Open messages.
Possible Causes:
A firewall blocking TCP port 179.
Incorrect IP addresses or network connectivity issues between the BGP peers.
Juniper Reference:
BGP Troubleshooting: In Junos, if a BGP session is stuck in the Connect state, the issue is likely due to a failure in establishing the underlying TCP connection.

質問 # 74
What is the primary purpose of using static routes in a network?

A. To aggregate multiple routes into one
B. To provide a manually configured routing entry
C. To automatically adjust routes based on network traffic
D. To generate routing entries dynamically

正解：B

質問 # 75
When configuring MAC address filtering on a Junos switch, which feature is primarily used?

A. Port security
B. RADIUS
C. Firewall filters
D. Access Control Lists (ACLs)

正解：A

質問 # 76
Which of the following are true about Layer 2 and Layer 3 strategies in data center architectures? (Choose two)

A. Layer 3 strategies cannot be used in conjunction with Layer 2 environments.
B. Layer 2 strategies are primarily used for inter-data center connectivity.
C. Layer 2 strategies are typically used for creating large, flat networks.
D. Layer 3 strategies help in reducing broadcast domains.

正解：C、D

質問 # 77
Which signaling protocol is used for EVPN?

A. OSPF
B. BGP
C. IS-IS
D. PIM

正解：B

解説：
EVPN (Ethernet Virtual Private Network) is a standard protocol used for building Layer 2 and Layer 3 VPNs over an IP or MPLS network. The signaling protocol used for EVPN is BGP (Border Gateway Protocol).
Step-by-Step Breakdown:
BGP as the EVPN Signaling Protocol:
EVPN uses BGP to exchange MAC address reachability information between routers (PE devices). This enables devices to learn which MAC addresses are reachable through which PE devices, facilitating Layer 2 forwarding across an IP or MPLS core.
BGP Extensions for EVPN:
BGP is extended with new address families (e.g., EVPN NLRI) to carry both MAC and IP address information, allowing for scalable and efficient multi-tenant network solutions.
Juniper Reference:
Junos EVPN Configuration: Juniper uses BGP as the control plane for EVPN to exchange MAC and IP route information between different data center devices.

質問 # 78
Under which Junos hierarchy is a static route configured?

A. system
B. routing-instances
C. protocols
D. routing-options

正解：D

質問 # 79
What is the primary purpose of OSPF in network routing?

A. To encrypt data traffic between different networks.
B. To provide path vector routing within an autonomous system.
C. To offer dynamic routing within an autonomous system using link-state information.
D. To redistribute routes between autonomous systems.

正解：C

質問 # 80
What does filter-based forwarding in networking typically allow?

A. Routing decisions based on extended criteria like packet headers
B. Aggregation of multiple routes into a single entry
C. Forwarding decisions based on MAC addresses
D. Load balancing across multiple CPUs

正解：A

質問 # 81
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 leaf device can communicate directly with other leaf devices.
C. Every server that connects to a three-stage IP fabric must be multihomed.
D. Every spine device can communicate directly with other spine devices.

正解：A

解説：
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.

質問 # 82
In the context of data center networking, what is the primary purpose of an Underlay Network?

A. To provide a physical infrastructure for an Overlay Network.
B. To facilitate virtual machine migrations.
C. To handle external network connections exclusively.
D. To encrypt data traffic between servers.

正解：A

質問 # 83
Which two statements are correct about rules for EBGP and IBGP? (Choose two.)

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

正解：B、D

解説：
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.

質問 # 84
What are two consequences of having all network devices in a single collision domain? (Choose two.)

A. The amount of network resource consumption is increased.
B. The chance of packet collision is decreased.
C. The chance of packet collision is increased.
D. The amount of network resource consumption does not change.

正解：A、C

解説：
A collision domain is a network segment where data packets can "collide" with one another when being sent on the same network medium.
Step-by-Step Breakdown:
Increased Collision Probability:
If all devices are in a single collision domain, the likelihood of packet collisions increases as more devices attempt to send packets simultaneously, leading to network inefficiencies.
Increased Resource Consumption:
More collisions result in increased network resource consumption as devices need to retransmit packets, causing higher utilization of bandwidth and slowing down network performance.
Juniper Reference:
Collision Domains: Proper network segmentation using switches reduces collision domains, thereby improving network performance and reducing packet collisions.

質問 # 85
How can OSPF be configured to prefer one route over another?

A. By adjusting interface bandwidth.
B. By configuring route redistribution.
C. By setting a higher cost on the preferred route.
D. By setting a lower cost on the preferred route.

正解：D

質問 # 86
Which route is preferred by the Junos OS software routing tables?

A. Aggregate
B. Direct
C. Static
D. BGP

正解：B

解説：
In Junos OS, direct routes are the most preferred routes in the routing table, having the highest priority.
Step-by-Step Breakdown:
Direct Routes:
Direct routes represent networks that are directly connected to the router's interfaces. Since these routes are directly accessible, they are assigned the highest priority and always take precedence over other types of routes.
Preference Values:
Direct routes have a preference of 0, which is the most preferred in Junos. Static routes, OSPF routes, and BGP routes have higher preference values and will only be used if there are no direct routes to the destination.
Juniper
Reference: Direct Route Preference: In Junos, direct routes are always preferred over other routes, ensuring that the router forwards traffic through locally connected networks.

質問 # 87
Which three actions are required to implement filter-based forwarding? (Choose three.)

A. You must create a match filter.
B. You must create a security policy.
C. You must create an instance-type forwarding routing instance.
D. You must create a RIB group.
E. You must create an instance-type vrf routing instance.

正解：A、C、D

解説：
Filter-Based Forwarding (FBF) in Junos OS allows traffic to be routed based on specific criteria such as source address, rather than just the destination address. This is useful in scenarios like policy routing or providing multiple paths for different types of traffic. Step-by-Step Breakdown:
Instance-Type Forwarding:
You must create an instance-type forwarding routing instance. This routing instance allows for different routing tables based on the incoming packet filter.
Command:
set routing-instances FBF-instance instance-type forwarding Match Filter:
You need to create a filter to match the traffic that will be forwarded according to your custom routing policy. This filter is applied to an interface to determine which traffic will use the custom forwarding instance.
Command Example:
set firewall family inet filter FBF-filter term 1 from source-address <address> set firewall family inet filter FBF-filter term 1 then routing-instance FBF-instance RIB Group:
A RIB (Routing Information Base) group is necessary to share routes between the primary routing table and the custom routing instance. This allows FBF traffic to use the routing information from other routing tables.
Command Example:
set routing-options rib-groups FBF-group import-rib inet.0
set routing-instances FBF-instance routing-options rib-group FBF-group
Juniper
Reference: FBF Configuration: Filter-based forwarding requires these specific steps to redirect traffic to a custom routing table based on filter criteria.

質問 # 88
What is the primary use of Martian addresses in network routing?