[2023年11月]更新のJN0-664問題集PDFでJN0-664リアル試験問題解答 [Q17-Q42]

[2023年11月]更新のJN0-664問題集PDFでJN0-664リアル試験問題解答

JN0-664問題集で100%合格保証と最新のお試しサンプル

Juniper JN0-664試験は、Juniper Networksサービスプロバイダーテクノロジーの徹底的な理解が必要な厳しい認定試験です。この認定を取得することで、ITプロフェッショナルはキャリアの見通しを向上させ、収益性を高め、自分たちの分野での専門家として認識されることができます。

JN0-664試験に合格することは、認定されたジュニパーネットワークの専門家になるための重要なステップです。候補者は、Juniper Networks Technologyを使用して複雑なサービスプロバイダーネットワークを設計、構成、およびトラブルシューティングするための知識とスキルを持っていることを雇用主とクライアントに示しています。

質問 # 17
Which two statements are correct about IS-IS interfaces? (Choose two.)

A. If a point-to-point interface is in both L1 and L2, one combined hello message is sent for both levels.
B. If a point-to-point interface is in both L1 and L2, separate hello messages are sent for each level.
C. If a broadcast interface is in both L1 and L2, separate hello messages are sent for each level
D. If a broadcast interface is in both L1 and L2, one combined hello message is sent for both levels.

正解：B、C

解説：
Explanation
IS-IS supports two levels of routing: Level 1 (intra-area) and Level 2 (interarea). An IS-IS router can be either Level 1 only, Level 2 only, or both Level 1 and Level 2. A router that is both Level 1 and Level 2 is called a Level 1-2 router. A Level 1-2 router sends separate hello messages for each level on both point-to-point and broadcast interfaces1. A point-to-point interface provides a connection between a single source and a single destination. A broadcast interface behaves as if the router is connected to a LAN.

質問 # 18
Exhibit

CE-1 and CE-2 are part of a VPLS called Customer1 No connectivity exists between CE-1 and CE-2. In the process of troubleshooting, you notice PE-1 is not learning any routes for this VPLS from PE-2, and PE-2 is not learning any routes for this VPLS from PE-1.

A. The instance type should be changed to I2vpn.
B. The route target must match on PE-1 and PE-2.
C. The route distinguisher must match on PE-1 and PE-2.
D. The no-tunnel-services statement should be deleted on both PEs.

正解：B

解説：
Explanation
VPLS is a technology that provides Layer 2 VPN services over an MPLS network. VPLS uses BGP as its control protocol to exchange VPN membership information between PE routers. The route target is a BGP extended community attribute that identifies which VPN a route belongs to. The route target must match on PE routers that participate in the same VPLS instance, otherwise they will not accept or advertise routes for that VPLS.

質問 # 19
Exhibit

Referring to the exhibit, CE-1 is providing NAT services for the hosts at Site 1 and you must provide Internet access for those hosts Which two statements are correct in this scenario? (Choose two.)

A. You must configure a static route in the main routing instance for the 10 1 2.0/24 prefix that uses the VPN-A.inet.0 table as the next hop
B. You must configure a static route in the main routing instance for the 203.0.113.1/32 prefix that uses the VPN-A.inet.0 table as the next hop.
C. You must configure a RIB group on PE-1 to leak a default route from the inet.0 table to the VPN-A.inet.0 table.
D. You must configure a RIB group on PE-1 to leak the 10 1 2.0/24 prefix from the VPN-A.inet.0 table to the inet.0 table.

正解：A、B

解説：
Explanation
To provide Internet access for the hosts at Site 1, you need to configure static routes in the main routing instance on PE-1 that point to the VPN-A.inet.0 table as the next hop. This allows PE-1 to forward traffic from the Internet to CE-1 using MPLS labels and vice versa. You need to configure two static routes: one for the
10.1.2.0/24 prefix that represents the private network of Site 1, and one for the 203.0.113.1/32 prefix that represents the public IP address of CE-1.

質問 # 20
What is the correct order of packet flow through configurable components in the Junos OS CoS features?

A. Multifield Classifier -> Behavior Aggregate Classifier -> Input Policer -> Forwarding Policy Options -> Fabric Scheduler -> Output Policer -> Rewrite Marker -> Scheduler/Shaper/RED
B. Behavior Aggregate Classifier -> Multifield Classifier -> Input Policer -> Forwarding Policy Options -> Fabric Scheduler -> Scheduler/Shaper/RED -> Output Policer -> Rewrite Marker
C. Behavior Aggregate Classifier -> Input Policer -> Multifield Classifier -> Forwarding Policy Options -> Fabric Scheduler -> Output Policer -> Scheduler/Shaper/RED -> Rewrite Marker
D. Behavior Aggregate Classifier -> Multifield Classifier -> Input Policer -> Forwarding Policy Options -> Fabric Scheduler -> Output Policer -> Scheduler/Shaper/RED -> Rewrite Marker

正解：C

解説：
Explanation
The correct order of packet flow through configurable components in the Junos OS CoS features is as follows:
* Behavior Aggregate Classifier: This component uses a single field in a packet header to classify traffic into different forwarding classes and loss priorities based on predefined or user-defined values.
* Input Policer: This component applies rate-limiting and marking actions to incoming traffic based on the forwarding class and loss priority assigned by the classifier.
* Multifield Classifier: This component uses multiple fields in a packet header to classify traffic into different forwarding classes and loss priorities based on user-defined values and filters.
* Forwarding Policy Options: This component applies actions such as load balancing, filtering, or routing to traffic based on the forwarding class and loss priority assigned by the classifier.
* Fabric Scheduler: This component schedules traffic across the switch fabric based on the forwarding class and loss priority assigned by the classifier.
* Output Policer: This component applies rate-limiting and marking actions to outgoing traffic based on the forwarding class and loss priority assigned by the classifier.
* Scheduler/Shaper/RED: This component schedules, shapes, and drops traffic at the egress interface based on the forwarding class and loss priority assigned by the classifier.
* Rewrite Marker: This component rewrites the code-point bits of packets leaving an interface based on the forwarding class and loss priority assigned by the classifier.

質問 # 21
Which statement is correct about IS-IS when it performs the Dijkstra algorithm?

A. When a new neighbor ID in the tree database matches a router ID in the LSDB, the neighbor ID is moved to the candidate database
B. Tuples with the lowest cost are moved from the tree database to the LSDB.
C. The algorithm will stop processing once the tree database is empty.
D. The local router moves its own local tuples into the candidate database

正解：D

解説：
Explanation
IS-IS is a link-state routing protocol that uses the Dijkstra algorithm to compute the shortest paths between nodes in a network. The Dijkstra algorithm maintains three data structures: a tree database, a candidate database, and a link-state database (LSDB). The tree database contains the nodes that have been visited and their shortest distances from the source node. The candidate database contains the nodes that have not been visited yet and their tentative distances from the source node. The LSDB contains the topology information of the network, such as the links and their costs.
The Dijkstra algorithm works as follows:
* The local router moves its own local tuples into the tree database. A tuple consists of a node ID, a distance, and a parent node ID. The local router's tuple has a distance of zero and no parent node.
* The local router moves its neighbors' tuples into the candidate database. The neighbors' tuples have distances equal to the costs of the links to them and parent node IDs equal to the local router's node ID.
* The local router selects the tuple with the lowest distance from the candidate database and moves it to the tree database. This tuple becomes the current node.
* The local router updates the distances of the current node's neighbors in the candidate database by adding the current node's distance to the link costs. If a shorter distance is found, the parent node ID is also updated.
* The algorithm repeats steps 3 and 4 until either the destination node is reached or the candidate database is empty.

質問 # 22
Which two statements are correct about reflecting inet-vpn unicast prefixes in BGP route reflection? (Choose two.)

A. Clients add their originator ID when advertising routes to their route reflector
B. Route reflectors add their cluster ID to the AS path when readvertising client routes.
C. Route reflectors do not change any existing BGP attributes by default when advertising routes.
D. A BGP peer does not require any configuration changes to become a route reflector client.

正解：C、D

解説：
Explanation
Route reflection is a BGP feature that allows a router to reflect routes learned from one IBGP peer to another IBGP peer, without requiring a full-mesh IBGP topology. Route reflectors do not change any existing BGP attributes by default when advertising routes, unless explicitly configured to do so. A BGP peer does not require any configuration changes to become a route reflector client, only the route reflector needs to be configured with the client parameter under [edit protocols bgp group group-name neighbor neighbor-address] hierarchy level.

質問 # 23
Which two statements are correct about a sham link? (Choose two.)

A. The PEs exchange Type 3 OSPF LSAs instead of Type 1 OSPF LSAs for the L3VPN routes.
B. It creates a BGP multihop neighborship between two PE routers.
C. The PEs exchange Type 1 OSPF LSAs instead of Type 3 OSPF LSAs for the L3VPN routes
D. It creates an OSPF multihop neighborship between two PE routers.

正解：C、D

解説：
Explanation
A sham link is a logical link between two PE routers that belong to the same OSPF area but are connected through an L3VPN. A sham link makes the PE routers appear as if they are directly connected, and prevents OSPF from preferring an intra-area back door link over the VPN backbone. A sham link creates an OSPF multihop neighborship between the PE routers using TCP port 646. The PEs exchange Type 1 OSPF LSAs instead of Type 3 OSPF LSAs for the L3VPN routes, which allows OSPF to use the correct metric for route selection1.

質問 # 24
Exhibit

You want to use both links between R1 and R2 Because of the bandwidth difference between the two links, you must ensure that the links are used as much as possible.
Which action will accomplish this goal?

A. Define a policy to tag routes with the appropriate bandwidth community.
B. Ensure that the metric-out parameter on the Gigabit Ethernet interface is higher than the 10 Gigibit Ethernet interface.
C. Enable per-prefix load balancing.
D. Disable multipath.

正解：C

解説：
Explanation
VPLS is a Layer 2 VPN technology that allows multiple sites to connect over a shared IP/MPLS network as if they were on the same LAN. VPLS tunnels can be signaled using either Label Distribution Protocol (LDP) or Border Gateway Protocol (BGP). In this question, we have two links between R1 and R2 with different bandwidths (10 Gbps and 1 Gbps). We want to use both links as much as possible for VPLS traffic. To achieve this, we need to enable per-prefix load balancing on both routers. Per-prefix load balancing is a feature that allows a router to distribute traffic across multiple equal-cost or unequal-cost paths based on the destination prefix of each packet. This improves the utilization of multiple links and provides better load sharing than per-flow load balancing, which distributes traffic based on a hash of source and destination addresses4. Per-prefix load balancing can be enabled globally or per interface using the load-balance per-packet command.

質問 # 25
When building an interprovider VPN, you notice on the PE router that you have hidden routes which are received from your BGP peer with family inet labeled-unica3t configured.
Which parameter must you configure to solve this problem?

A. Under the family inet labeled-unicast hierarchy, add the resolve-vpn parameter.
B. Under the protocols ospf hierarchy, add the traffic-engineering parameter.
C. Under the family inet labeled-unicast hierarchy, add the explicit null parameter.
D. Under the protocols mpls hierarchy, add the traffic-engineering parameter

正解：A

解説：
Explanation
The resolve-vpn parameter is a BGP option that allows a router to resolve labeled VPN-IPv4 routes using unlabeled IPv4 routes received from another BGP peer with family inet labeled-unicast configured. This option enables interprovider VPNs without requiring MPLS labels between ASBRs or using VRF tables on ASBRs. In this scenario, you need to configure the resolve-vpn parameter under [edit protocols bgp group external family inet labeled-unicast] hierarchy level on both ASBRs.

質問 # 26
When using OSPFv3 for an IPv4 environment, which statement is correct?

A. OSPFv3 only supports IPv4.
B. OSPFv3 supports both IPv6 and IPv4, but not in the same routing instance.
C. OSPFv3 is not backward compatible with IPv4
D. OSPFv3 supports IPv4 only on interfaces with family inet6 defined

正解：C

解説：
Explanation
OSPFv3 is an extension of OSPFv2 that supports IPv6 routing and addressing. OSPFv3 is not backward compatible with IPv4 because it uses a different packet format and a different link-state advertisement (LSA) structure than OSPFv2. OSPFv3 also uses IPv6 link-local addresses as router IDs and neighbor addresses, instead of IPv4 addresses. To use OSPFv3 for an IPv4 environment, you need to enable the IPv4 unicast address family under [edit protocols ospf3] hierarchy level and configure IPv4 addresses on the interfaces.

質問 # 27
Exhibit.

Referring to the exhib.t, what must be changed to establish a Level 1 adjacency between routers R1 and R2?

A. Change the level 1 disable parameter under the R2 protocols isis interface ge-1/2/3 .0 hierarchy to the level 2 disable parameter
B. Change the level l disable parameter under the R1 protocols isis interface lo0.0 hierarchy to the level 2 disable parameter.
C. Add IP addresses to the interface ge-l/2/3 unit 0 family iso hierarchy on both R1 and R2.
D. Remove the level i disable parameter under the R2 protocols isis interface loo . 0 configuration hierarchy.

正解：D

解説：
Explanation
IS-IS routers can form Level 1 or Level 2 adjacencies depending on their configuration and network topology.
Level 1 routers are intra-area routers that share the same area address with their neighbors. Level 2 routers are inter-area routers that can connect different areas. Level 1-2 routers are both intra-area and inter-area routers that can form adjacencies with any other router.
In the exhibit, R1 and R2 are in different areas (49.0001 and 49.0002), so they cannot form a Level 1 adjacency. However, they can form a Level 2 adjacency if they are both configured as Level 1-2 routers. R1 is already configured as a Level 1-2 router, but R2 is configured as a Level 1 router only, because of the level 1 disable command under the lo0.0 interface. This command disables Level 2 routing on the loopback interface, which is used as the router ID for IS-IS.
Therefore, to establish a Level 1 adjacency between R1 and R2, the level 1 disable command under the R2 protocols isis interface lo0.0 hierarchy must be removed. This will enable Level 2 routing on R2 and allow it to form a Level 2 adjacency with R1.

質問 # 28
Which two statements are correct about the customer interface in an LDP-signaled pseudowire? (Choose two)

A. When the encapsulation is vlan-ccc or extended-vlan-ccc, the configured VLAN tag is not included in the control plane LDP advertisement
B. When the encapsulation is ethernet-ccc, only frames without a VLAN tag are accepted in the data plane
C. When the encapsulation is vLan-ccc or extended-vlan-ccc, the configured VLAN tag is included in the control plane LDP advertisement
D. When the encapsulation is ethemet-ccc, tagged and untagged frames are both accepted in the data plane.

正解：C、D

解説：
Explanation
The customer interface in an LDP-signaled pseudowire is the interface on the PE router that connects to the CE device. An LDP-signaled pseudowire is a type of Layer 2 circuit that uses LDP to establish a point-to-point connection between two PE routers over an MPLS network. The customer interface can have different encapsulation types depending on the type of traffic that is carried over the pseudowire. The encapsulation types are ethernet-ccc, vlan-ccc, extended-vlan-ccc, atm-ccc, frame-relay-ccc, ppp-ccc, cisco-hdlc-ccc, and tcc-ccc. Depending on the encapsulation type, the customer interface can accept or reject tagged or untagged frames in the data plane, and include or exclude VLAN tags in the control plane LDP advertisement. The following table summarizes the behavior of different encapsulation types:

質問 # 29
You are asked to protect your company's customers from amplification attacks. In this scenario, what is Juniper's recommended protection method?

A. unicast Reverse Path Forwarding
B. ASN prepending
C. destination-based Remote Triggered Black Hole
D. BGP FlowSpec

正解：C

解説：
Explanation
amplification attacks are a type of distributed denial-of-service (DDoS) attack that exploit the characteristics of certain protocols to amplify the traffic sent to a victim. For example, an attacker can send a small DNS query with a spoofed source IP address to a DNS server, which will reply with a much larger response to the victim. This way, the attacker can generate a large amount of traffic with minimal resources.
One of the methods to protect against amplification attacks is destination-based Remote Triggered Black Hole (RTBH) filtering. This technique allows a network operator to drop traffic destined to a specific IP address or prefix at the edge of the network, thus preventing it from reaching the victim and consuming bandwidth and resources. RTBH filtering can be implemented using BGP to propagate a special route with a next hop of
192.0.2.1 (a reserved address) to the edge routers. Any traffic matching this route will be discarded by the edge routers.

質問 # 30
Exhibit

Based on the configuration contents shown in the exhibit, which statement is true?

A. Joins for any group are accepted if the group count value is less than 25.
B. Joins for group 224.7.7.7 are rejected if the source address is 192.168.100.10
C. Joins for group 224.7.7.7 are accepted if the group count is less than 25
D. Joins for group 224.7.7.7 are always rejected, regardless of the group count.

正解：C

解説：
Explanation
BGP policy framework is a set of tools that allows you to control the flow of routing information and apply routing policies based on various criteria. BGP policy framework consists of several components, such as route maps, prefix lists, community lists, AS path lists, and route filters. Route maps are used to define routing policies by matching certain conditions and applying certain actions. Prefix lists are used to filter routes based on their prefixes. Community lists are used to filter routes based on their community attributes. AS path lists are used to filter routes based on their AS path attributes. Route filters are used to filter routes based on their prefix length or range3. In this question, we have a route map named ISP-A that has two clauses: clause 10 and clause 20. Clause 10 matches any route with a prefix length between 8 and 24 bits and sets the local preference to 200. Clause 20 matches any route with a prefix of 224.7.7.7/32 and rejects it. The route map is applied inbound on the BGP neighborship with ISP-A. Based on this configuration, the correct statement is that joins for group 224.7.7.7 are always rejected, regardless of the group count. This is because clause 20 explicitly denies any route with a prefix of 224.7.7.7/32, which corresponds to the multicast group 224.7.7.7.

質問 # 31
Exhibit
user@Rl show configuration interpolated-profile { interpolate {
fill-level [ 50 75 drop-probability [ > }
class-of-service drop-profiles
];
20 60 ];
Which two statements are correct about the class-of-service configuration shown in the exhibit? (Choose two.)

A. To use this drop profile, you reference it in a scheduler.
B. The drop probability gradually increases from 20% to 60% as the queue level increases from 50% full to
75% full
C. To use this drop profile, you apply it directly to an interface.
D. The drop probability jumps immediately from 20% to 60% when the queue level reaches 75% full.

正解：A、B

解説：
Explanation
class-of-service (CoS) is a feature that allows you to prioritize and manage network traffic based on various criteria, such as application type, user group, or packet loss priority. CoS uses different components to classify, mark, queue, schedule, shape, and drop traffic according to the configured policies.
One of the components of CoS is drop profiles, which define how packets are dropped when a queue is congested. Drop profiles use random early detection (RED) algorithm to drop packets randomly before the queue is full, which helps to avoid global synchronization and improve network performance. Drop profiles can be discrete or interpolated. A discrete drop profile maps a specific fill level of a queue to a specific drop probability. An interpolated drop profile maps a range of fill levels of a queue to a range of drop probabilities and interpolates the values in between.
In the exhibit, we can see that the class-of-service configuration shows an interpolated drop profile with two fill levels (50 and 75) and two drop probabilities (20 and 60). Based on this configuration, we can infer the following statements:
* The drop probability jumps immediately from 20% to 60% when the queue level reaches 75% full. This is not correct because the drop profile is interpolated, not discrete. This means that the drop probability gradually increases from 20% to 60% as the queue level increases from 50% full to 75% full. The drop probability for any fill level between 50% and 75% can be calculated by using linear interpolation formula.
* The drop probability gradually increases from 20% to 60% as the queue level increases from 50% full to
75% full. This is correct because the drop profile is interpolated and uses linear interpolation formula to calculate the drop probability for any fill level between 50% and 75%. For example, if the fill level is
60%, the drop probability is 28%, which is calculated by using the formula: (60 - 50) / (75 - 50) * (60 -
20) + 20 = 28.
* To use this drop profile, you reference it in a scheduler. This is correct because a scheduler is a component of CoS that determines how packets are dequeued from different queues and transmitted on an interface. A scheduler can reference a drop profile by using the random-detect statement under the
[edit class-of-service schedulers] hierarchy level. For example: scheduler test { transmit-rate percent 10; buffer-size percent 10; random-detect test-profile; }
* To use this drop profile, you apply it directly to an interface. This is not correct because a drop profile cannot be applied directly to an interface. A drop profile can only be referenced by a scheduler, which can be applied to an interface by using the scheduler-map statement under the [edit class-of-service interfaces] hierarchy level. For example: interfaces ge-0/0/0 { unit 0 { scheduler-map test-map; } }

質問 # 32
Exhibit

Referring to the exhibit, PE-1 and PE-2 are getting route updates for VPN-B when neither of them service that VPN Which two actions would optimize this process? (Choose two.)

A. Configure the family route-target statement on the RR
B. Configure the resolution rib bgp.l3vpn.O resolution-ribs inet. 0 Statement on the RR
C. Configure the resolution rib bgp . 13vpn . 0 resolution-ribs inet. 0 Statement on the PEs.
D. Configure the family route-target statement on the PEs.

正解：A、B

解説：
Explanation
BGP route target filtering is a technique that reduces the number of routers that receive VPN routes and route updates, helping to limit the amount of overhead associated with running a VPN. BGP route target filtering is based on the exchange of the route-target address family, which contains information about the VPN membership of each PE device. Based on this information, a PE device can decide whether to accept or reject VPN routes from another PE device.
BGP route target filtering can be configured on PE devices or on route reflectors (RRs). Configuring BGP route target filtering on RRs is more efficient and scalable, as it reduces the number of BGP sessions and updates between PE devices. To configure BGP route target filtering on RRs, the following steps are required:
* Configure the family route-target statement under the BGP group or neighbor configuration on the RRs.
This enables the exchange of the route-target address family between the RRs and their clients (PE devices).
* Configure the resolution rib bgp.l3vpn.0 resolution-ribs inet.0 statement under the routing-options configuration on the RRs. This enables the RRs to resolve next hops for VPN routes using the inet.0 routing table.
* Configure an export policy for BGP route target filtering under the routing-options configuration on the RRs. This policy controls which route targets are advertised to each PE device based on their VPN membership.

質問 # 33
Exhibit

Referring to the exhibit, PIM-SM is configured on all routers, and Anycast-RP with Anycast-PIM is used for the discovery mechanism on RP1 and RP2. The interface metric values are shown for the OSPF area.
In this scenario, which two statements are correct about which RP is used? (Choose two.)

A. Source1 will use RP1 and Receiver1 will use RP1 for group 224.1.1.1.
B. Source2 will use RP1 and Receiver2 will use RP1 for group 224.2.2.2.
C. Source1 will use RP1 and Receiver1 will use RP2 for group 224.1 1 1
D. Source2 will use RP2 and Received will use RP2 for group 224.2.2.2.

正解：A、D

質問 # 34
Which two statements are correct about VPLS tunnels? (Choose two.)

A. LDP-signaled VPLS tunnels use auto-discovery to provision sites
B. LDP-signaled VPLS tunnels only support control bit 0.
C. BGP-signaled VPLS tunnels require manual provisioning of sites.
D. BGP-signaled VPLS tunnels can use either RSVP or LDP between the PE routers.

正解：A、D

解説：
Explanation
VPLS is a Layer 2 VPN technology that allows multiple sites to connect over a shared IP/MPLS network as if they were on the same LAN. VPLS tunnels can be signaled using either Label Distribution Protocol (LDP) or Border Gateway Protocol (BGP). LDP-signaled VPLS tunnels use auto-discovery to provision sites, meaning that PE routers can automatically discover other PE routers that belong to the same VPLS instance

質問 # 35
Exhibit

Referring to the exhibit, what do the brackets [ ] in the AS path identify?

A. They identify an AS set, which are groups of AS numbers in which the order does not matter
B. They identify that a BGP confederation is being used to ensure that there are no routing loops.
C. They identify the local AS number associated with the AS path if configured on the router, or if AS path prepending is configured
D. They identify that the autonomous system number is incomplete and awaiting more information from the BGP protocol.

正解：A

解説：
Explanation
The brackets [ ] in the AS path identify an AS set, which are groups of AS numbers in which the order does not matter. An AS set is used when BGP aggregates routes from different ASs into a single prefix. For example, if BGP aggregates routes 10.0.0.0/16 and 10.1.0.0/16 from AS 100 and AS 200, respectively, into a single prefix 10.0.0.0/15, then the AS path for this prefix will be [100 200]. An AS set reduces the length of the AS path and prevents routing loops.

質問 # 36
Which statement is true regarding BGP FlowSpec?

A. It uses a remote triggered black hole to protect a network from a denial-of-service attack.
B. It uses dynamically created routing policies to protect a network from denial-of-service attacks
C. It verifies that the source IP of the incoming packet has a resolvable route in the routing table
D. It is used to protect a network from denial-of-service attacks dynamically

正解：B

解説：
Explanation
BGP FlowSpec is a feature that extends the Border Gateway Protocol (BGP) to enable routers to exchange traffic flow specifications, allowing for more precise control of network traffic. The BGP FlowSpec feature enables routers to advertise and receive information about specific flows in the network, such as those originating from a particular source or destined for a particular destination. Routers can then use this information to construct traffic filters that allow or deny packets of a certain type, rate limit flows, or perform other actions1. BGP FlowSpec can also help in filtering traffic and taking action against distributed denial of service (DDoS) attacks by dropping the DDoS traffic or diverting it to an analyzer2. BGP FlowSpec rules are internally converted to equivalent Cisco Common Classification Policy Language (C3PL) representing corresponding match and action parameters2. Therefore, BGP FlowSpec uses dynamically created routing policies to protect a network from denial-of-service attacks.
References: 1: https://www.networkingsignal.com/what-is-bgp-flowspec/ 2:
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_bgp/configuration/xe-16/irg-xe-16-book/bgp-flowspe

質問 # 37
In IS-IS, which two statements are correct about the designated intermediate system (DIS) on a multi-access network segment? (Choose two)

A. A router with a priority of 10 wins the DIS election over a router with a priority of 1.
B. On the multi-access network, each router only forms an adjacency to the DIS.
C. A router with a priority of 1 wins the DIS election over a router with a priority of 10.
D. On the multi-access network, each router forms an adjacency to every other router on the segment

正解：A、B

解説：
Explanation
In IS-IS, a designated intermediate system (DIS) is a router that is elected on a multi-access network segment (such as Ethernet) to perform some functions on behalf of other routers on the same segment. A DIS is responsible for sending network link-state advertisements (LSPs), which describe all the routers attached to the network. These LSPs are flooded throughout a single area. A DIS also generates pseudonode LSPs, which represent the multi-access network as a single node in the link-state database. A DIS election is based on the priority value configured on each router's interface connected to the multi-access network. The priority value ranges from 0 to 127, with higher values indicating higher priority. The router with the highest priority becomes the DIS for the area (Level 1, Level 2, or both). If routers have the same priority, then the router with the highest MAC address is elected as the DIS. By default, routers have a priority value of 64. On a multi-access network, each router only forms an adjacency to the DIS, not to every other router on the segment. This reduces the amount of hello packets and LSP

質問 # 38
Which origin code is preferred by BGP?

A. Internal
B. Incomplete
C. Null
D. External

正解：B

解説：
Explanation
BGP uses several attributes to select the best path for a destination prefix. One of these attributes is origin, which indicates how BGP learned about a route. The origin attribute can have one of three values: IGP, EGP, or Incomplete. IGP means that the route was originated by a network or aggregate statement within BGP or by redistribution from an IGP into BGP. EGP means that the route was learned from an external BGP peer (this value is obsolete since BGP version 4). Incomplete means that the route was learned by some other means, such as redistribution from a static route into BGP. BGP prefers routes with lower origin values, so Incomplete is preferred over EGP, which is preferred over IGP.

質問 # 39
Which two EVPN route types are used to advertise a multihomed Ethernet segment? (Choose two )

A. Type 2
B. Type 4
C. Type 1
D. Type 3

正解：B、C

解説：
Explanation
EVPN is a solution that provides Ethernet multipoint services over MPLS networks. EVPN uses BGP to distribute endpoint provisioning information and set up pseudowires between PE devices. EVPN uses different route types to convey different information in the control plane. The following are the main EVPN route types:
* Type 1 - Ethernet Auto-Discovery Route: This route type is used for network-wide messaging and discovery of other PE devices that are part of the same EVPN instance. It also carries information about the redundancy mode and load balancing algorithm of the PE devices.
* Type 2 - MAC/IP Advertisement Route: This route type is used for MAC and IP address learning and advertisement between PE devices. It also carries information about the Ethernet segment identifier (ESI) and the label for forwarding traffic to the MAC or IP address.
* Type 3 - Inclusive Multicast Ethernet Tag Route: This route type is used for broadcast, unknown unicast, and multicast (BUM) traffic forwarding. It also carries information about the multicast group and the label for forwarding BUM traffic.
* Type 4 - Ethernet Segment Route: This route type is used for multihoming scenarios, where a CE device is connected to more than one PE device. It also carries information about the ESI and the designated forwarder (DF) election process.

質問 # 40
In which two ways does OSPF prevent routing loops in multi-area networks? (Choose two.)

A. The SPF algorithm prunes looped paths within an area.
B. All areas are required to connect as a full mesh.
C. The LFA algorithm prunes all looped paths within an area.
D. All areas are required to connect to area 0.

正解：A、D

解説：
Explanation
OSPF is an interior gateway protocol that uses link-state routing to exchange routing information among routers within a single autonomous system. OSPF prevents routing loops in multi-area networks by using two methods: area hierarchy and SPF algorithm. Area hierarchy is the concept of dividing a large OSPF network into smaller areas that are connected to a backbone area (area 0). This reduces the amount of routing information that each router has to store and process, and also limits the scope of link-state updates within each area. All areas are required to connect to area 0 either directly or through virtual links2. SPF algorithm is the method that OSPF uses to calculate the shortest path to each destination in the network based on link-state information. The SPF algorithm runs on each router and builds a shortest-path tree that represents the topology of the network from the router's perspective. The SPF algorithm prunes looped paths within an area by choosing only one best path for each destination3.
References: 2:
https://www.juniper.net/documentation/us/en/software/junos/ospf/topics/concept/ospf-area-overview.html 3:
https://www.juniper.net/documentation/us/en/software/junos/ospf/topics/concept/ospf-spf-algorithm-overview.ht

質問 # 41
Exhibit

Referring to the exhibit, which statement is true?

A. The 10.101.1.0/24 route will be shared if the auto-export parameter is configured
B. The 10.101.1.0/24 route will only be shared if BGP is configured in the routing instance
C. The 10.101.1.0/24 route will be shared if the vrf-table-label parameter is configured.
D. The 10.101.1 0/24 route will be shared if there are other VRFs that use the same route target community

正解：A

解説：
Explanation
The auto-export parameter is a routing option that allows a routing instance to share routes with other routing instances or the master routing table. The auto-export parameter automatically exports routes from one routing instance to another based on the route target communities attached to the routes. In this scenario, the
10.101.1.0/24 route will be shared if the auto-export parameter is configured under [edit routing-options] hierarchy level.

質問 # 42
......

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