最適な練習法にはJN0-664問題集で素晴らしいJN0-664試験問題PDF
更新された検証済みの合格させるJN0-664試験リアル問題と解答があります
この認定は、Juniper Networks のサービスプロバイダソリューションの管理とメンテナンスを担当する専門家に最適です。この試験は、少なくとも3年間のプロダクション環境での Juniper Networks サービスプロバイダソリューションの実装経験を持つ個人を対象としています。JN0-664 試験は、サービスプロバイダ技術の分野における候補者の知識、スキル、能力を厳しくテストし、試験に合格することは、どのサービスプロバイダ専門家にとっても重要なマイルストーンです。
JN0-664試験は、OSPF、IS-IS、BGP、MPLS、レイヤー2 VPN、レイヤー3 VPN、マルチキャスト、およびクラスオブサービスを含む広範なトピックをカバーしています。候補者は、これらの技術をエキスパートレベルで構成、監視、およびトラブルシューティングする能力を示さなければなりません。試験は厳しいものであり、カバーされる技術とプロトコルの深い理解が必要です。
質問 # 44
Exhibit
Referring to the exhibit, what do the brackets [ ] in the AS path identify?
- A. They identify that the autonomous system number is incomplete and awaiting more information from the BGP protocol.
- B. They identify the local AS number associated with the AS path if configured on the router, or if AS path prepending is configured
- C. They identify that a BGP confederation is being used to ensure that there are no routing loops.
- D. They identify an AS set, which are groups of AS numbers in which the order does not matter
正解：D
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 # 45
You are responding to an RFP for a new MPLS VPN implementation. The solution must use LDP for signaling and support Layer 2 connectivity without using BGP. The solution must be scalable and support multiple VPN connections over a single MPLS LSP. The customer wants to maintain all routing for their private network.
In this scenario, which solution do you propose?
- A. circuit cross-connect
- B. BGP Layer 2 VPN
- C. LDP Layer 2 circuit
- D. translational cross-connect
正解：C
質問 # 46 
Click the Exhibit button.
PE-1 and PE-2 are configured with LDP-signaled pseudowires to provide connectivity between CE-1 and CE-
2. You notice no connectivity exists between CE-1 and CE-2.
Referring to the exhibit, which two statements describe potential causes for this fault? (Choose two.)
- A. The VC IDs are mismatched.
- B. There is no LSP configured from PE-1 to PE-2.
- C. Interface ge-0/0/0 on PE-1 is down.
- D. There is no LSP configured from PE-2 to PE-1.
正解：A、D
質問 # 47
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 apply it directly to an interface.
- B. The drop probability gradually increases from 20% to 60% as the queue level increases from 50% full to
75% full - C. The drop probability jumps immediately from 20% to 60% when the queue level reaches 75% full.
- D. To use this drop profile, you reference it in a scheduler.
正解：B、D
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 # 48
Exhibit
Referring to the exhibit, which two statements are true? (Choose two.)
- A. This is an EVPN Type-2 route.
- B. The device advertising this route into EVPN is 192.168.101.5.
- C. The devices advertising this route into EVPN are 10 0 2 12 and 10.0.2.22.
- D. This route is learned through EBGP
正解：A、B
解説：
Explanation
This is an EVPN Type-2 route, also called a MAC/IP advertisement route, that is used to advertise host IP and MAC address information to other VTEPs in an EVPN network. The route type field in the EVPN NLRI has a value of 2, indicating a Type-2 route. The device advertising this route into EVPN is 192.168.101.5, which is the IP address of the VTEP that learned the host information from the local CE device. This IP address is carried in the MPLS label field of the route as part of the VXLAN encapsulation.
質問 # 49
Referring to the exhibit, which two statements are correct about BGP routes on R3 that are advertised to R1? (Choose two.)
- A. By default, the next-hop value for these routes is changed by R3 before being sent to R1.
- B. By default, all BGP attributes values must be removed before advertising the routes to R1.
- C. By default, the next-hop value for these routes is not changed by R3 before being sent to R1.
- D. By default, the BGP local-preference value that is assigned on R3 is advertised to R1.
正解：C、D
質問 # 50
After a recent power outage, your manager asks you to investigate ways to automatically reduce the impact caused by suboptimal routing in your OSPF and OSPFv3 network after devices reboot.
Which three configuration statements accomplish this task? (Choose three.)
- A. set protocols ospf overload
- B. set protocols ospf overload timeout 900
- C. set protocols ospf3 realm ipv4-unicast overload timeout 900
- D. set protocols ospf3 overload timeout 900
- E. set protocols ospf3 overload
正解：B、C、D
質問 # 51
Exhibit
You have MAC addresses moving in your EVPN environment
Referring to the exhibit, which two statements are correct about the sequence number? (Choose two)
- A. It helps the local PE to identify the latest advertisement.
- B. It is advertised using a Type 2 message
- C. It identifies MAC addresses that should be discarded.
- D. It resolves conflicting MAC address ownership claims.
正解：A、B
解説：
In an EVPN (Ethernet Virtual Private Network) environment, MAC address mobility is a critical feature that allows devices to move across different locations while ensuring the network consistently tracks their MAC addresses. Let's break down the components in the exhibit and analyze the correct statements.
Understanding MAC Mobility and Sequence Numbers in EVPN
In EVPN, MAC mobility is managed through sequence numbers that are included in Type 2 MAC/IP advertisements.
The sequence number tracks MAC movement events and is used to determine the most recent update when a MAC address appears on different PEs (Provider Edge devices).
When a MAC address moves between locations, the EVPN PEs increment the sequence number and advertise it to resolve conflicts and determine which PE has the most up-to-date information.
Now, Let's Review the Options:
✅ C. It helps the local PE to identify the latest advertisement.
Correct:
The sequence number plays a key role in resolving MAC address conflicts. If multiple PEs advertise the same MAC address, the PE compares the sequence numbers to determine which update is the latest.
A higher sequence number indicates a more recent MAC update.
✅ D. It is advertised using a Type 2 message.
Correct:
EVPN MAC/IP advertisements use BGP EVPN Type 2 messages to carry MAC addresses, IP addresses (optional), and their associated sequence numbers.
Type 2 advertisements are used to track MAC mobility and IP reachability information in the EVPN.
Why the Other Options Are Incorrect:
❌ A. It identifies MAC addresses that should be discarded.
Incorrect:
The sequence number doesn't identify MAC addresses that need to be discarded.
Instead, it resolves conflicts by determining the most recent MAC address advertisement based on the highest sequence number.
❌ B. It resolves conflicting MAC address ownership claims.
Partially true, but misleading:
While it's true that sequence numbers are used in conflict resolution, the sequence number itself doesn't directly resolve ownership claims. It only helps determine which advertisement is more recent. The actual conflict resolution happens through the comparison of the advertisements and sequence numbers.
Final answer:
✅ C. It helps the local PE to identify the latest advertisement.
✅ D. It is advertised using a Type 2 message.
Reference from Juniper Documentation:
Juniper EVPN Configuration Guide:
"In EVPN MAC/IP advertisements, sequence numbers track the mobility of MAC addresses and are used to resolve conflicts when the same MAC address is advertised by multiple PEs. The PE with the higher sequence number has the most recent information." Juniper BGP EVPN Mobility Documentation
質問 # 52
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 route target must match on PE-1 and PE-2.
- B. The no-tunnel-services statement should be deleted on both PEs.
- C. The route distinguisher must match on PE-1 and PE-2.
- D. The instance type should be changed to I2vpn.
正解：A
解説：
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 # 53
Exhibit
Referring to the exhibit, what do the brackets [ ] in the AS path identify?
- A. They identify that the autonomous system number is incomplete and awaiting more information from the BGP protocol.
- B. They identify the local AS number associated with the AS path if configured on the router, or if AS path prepending is configured
- C. They identify that a BGP confederation is being used to ensure that there are no routing loops.
- D. They identify an AS set, which are groups of AS numbers in which the order does not matter
正解：D
解説：
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 # 54
You are using a Layer 3 VPN to connect two customer sites. The VPN routes for the customer networks appear as hidden in the bgp. 13vpn. o routing table on the PE routers.
What is causing this problem?
- A. There is a routing loop in the service provider backbone.
- B. There is not an established MPLS LSP between the two PE routers.
- C. The routes use overlapping IP addresses.
- D. Route targets are not configured.
正解：B
質問 # 55
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 RP2 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 RP1 for group 224.1.1.1.
- D. Source2 will use RP2 and Receiver2 will use RP2 for group 224.2.2.2.
正解：B、C
質問 # 56
Exhibit
You must ensure that the VPN backbone is preferred over the back door intra-area link as long as the VPN is available. Referring to the exhibit, which action will accomplish this task?
- A. Configure the OSPF metric on the backup intra-area link that is higher than the L3VPN link.
- B. Enable OSPF traffic-engineering.
- C. Configure an import routing policy on the CE routers that rejects OSPF routes learned on the backup intra-area link.
- D. Create an OSPF sham link between the PE routers.
正解：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. To create a sham link, you need to configure the local and remote addresses of the PE routers under the [edit protocols ospf area area-id] hierarchy level1.
質問 # 57
Exhibit
R4 is directly connected to both RPs (R2 and R3) R4 is currently sending all ,o,ns upstream to R3 but you want all joins to go to R2 instead Referring to the exhibit, which configuration change will solve this issue?
- A. Change the group-range to be more specific on R2 than R3.
- B. Change the local address on R2 to be higher than R3.
- C. Change the default route in inet.2 on R4 from R3 as the next hop to R2
- D. Change the bootstrap priority on R2 to be higher than R3
正解：A
質問 # 58
You are using a Layer 3 VPN to connect two customer sites. The VPN routes for the customer networks appear as hidden in the bgp. 13vpn. o routing table on the PE routers.
What is causing this problem?
- A. There is a routing loop in the service provider backbone.
- B. There is not an established MPLS LSP between the two PE routers.
- C. The routes use overlapping IP addresses.
- D. Route targets are not configured.
正解：B
解説：
For a Layer 3 VPN to function correctly, an MPLS Label Switched Path (LSP) must be established between the Provider Edge (PE) routers. The MPLS LSP is necessary for the transport of VPN traffic across the service provider's backbone network. If the MPLS LSP is not established, the PE routers cannot forward the VPN traffic properly, causing the routes to be hidden in the BGP routing table.
Here's a breakdown of why the other options are less likely:
A: The routes use overlapping IP addresses.
* Overlapping IP addresses might cause issues with route advertisement and selection, but they would not typically cause routes to be hidden in the bgp.l3vpn.0 table.
C: There is a routing loop in the service provider backbone.
* While routing loops are problematic, they would not specifically cause the routes to be hidden in the bgp.l3vpn.0 table. Routing loops would more likely result in dropped packets or increased latency.
D: Route targets are not configured.
* Incorrect or missing route target configuration would prevent routes from being imported into the correct VRF, but it would not usually result in the routes being hidden. Instead, they would simply not appear in the relevant VRF.
Thus, the absence of an established MPLS LSP is the most plausible cause for the routes being hidden.
質問 # 59
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. BGP FlowSpec
- D. destination-based Remote Triggered Black Hole
正解：D
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 # 60
Exhibit
Referring to the exhibit, a working L3VPN exists that connects VPN-A sites CoS is configured correctly to match on the MPLS EXP bits of the LSP, but when traffic is sent from Site-1 to Site-2, PE-2 is not classifying the traffic correctly What should you do to solve the problem?
- A. Configure the explicit-null statement on PE-1.
- B. Set a static CoS value for the PE-1_to_PE-2 LSP
- C. Configure VPN prefix mapping for the PE-1_to_PE-2 LSP
- D. Configure the explicit-null statement on PE-2
正解：D
解説：
Understanding the Problem in MPLS CoS Classification
How EXP Bits Are Used for CoS in MPLS
Traffic is sent from VPN-A Site-1 → CE-1 → PE-1 → P-1 → PE-2 → CE-2.
The MPLS LSP (Label Switched Path) from PE-1 to PE-2 is expected to carry MPLS EXP bits, which are used for Class of Service (CoS) classification.
PE-2 should classify traffic based on EXP bits received in the MPLS label.
What Happens with PHP (Penultimate Hop Popping)?
By default, the penultimate router (P-1) pops the top MPLS label before sending the packet to PE-2.
Since the EXP bits are in the top MPLS label, they get removed along with the label.
This means that PE-2 no longer sees the correct EXP bits, leading to incorrect traffic classification.
Solution: Configure Explicit-Null on PE-2
Explicit Null (explicit-null) must be configured on PE-2 to ensure that P-1 does NOT remove the MPLS label.
Instead of removing the label, P-1 will send a label of 0 (for IPv4) or 2 (for IPv6) to PE-2.
This preserves the MPLS EXP bits, allowing PE-2 to classify the traffic correctly.
Evaluating the Answer Choices Again
✅ B. Configure the explicit-null statement on PE-2.
Correct, because:
PE-2 is the egress LSR, where Ultimate Hop Popping (UHP) must be enabled.
Configuring explicit-null ensures that P-1 does not remove the label, preserving the EXP bits for CoS classification at PE-2.
Configuration on PE-2:
set protocols mpls explicit-null
Juniper Documentation Reference:
"Explicit-null must be configured on the egress LSR to prevent PHP from removing the top MPLS label, thereby preserving the EXP bits."
❌ A. Configure the explicit-null statement on PE-1.
Incorrect, because:
Explicit-null must be configured on the egress LSR (PE-2), not the ingress LSR (PE-1).
PE-1 only labels the traffic but does not control PHP behavior on P-1.
❌ C. Configure VPN prefix mapping for the PE-1_to_PE-2 LSP.
Incorrect, because:
VPN prefix mapping is used for mapping VPN routes to LSPs but does not solve the EXP bit issue.
The problem here is label removal (PHP), not route mapping.
❌ D. Set a static CoS value for the PE-1_to-PE-2 LSP.
Incorrect, because:
This does not preserve the original EXP bits, it only applies a static CoS value.
It's a workaround, not a fix.
Final answer: ✅ B. Configure the explicit-null statement on PE-2.
Key Takeaways
Penultimate Hop Popping (PHP) removes the outer MPLS label at P-1, which also removes the EXP bits used for CoS classification.
To keep EXP bits intact, configure explicit-null on the egress PE (PE-2).
This forces P-1 to send a label (0 for IPv4, 2 for IPv6) to PE-2, preserving the EXP bits for CoS classification.
Official Juniper Documentation Reference
Juniper MPLS CoS and PHP Behavior Guide
"To retain CoS EXP bits at the egress LSR, configure explicit-null on the egress PE. This prevents PHP from stripping the MPLS label before reaching the final PE router."
質問 # 61
You are configuring schedulers to define the class-of-service properties of output queues. You want to control packet drops during periods of congestion.
In this scenario, which CoS configuration parameter would be used to accomplish this task?
- A. shaping rate
- B. priority
- C. drop profile
- D. buffer size
正解：C
解説：
When configuring Class of Service (CoS) properties for output queues, we need to manage packet drops during periods of congestion. Juniper's CoS framework provides several tools to manage congestion, including drop profiles, buffer sizes, and scheduling mechanisms. Let's break down each option and identify the correct one.
Evaluating the Answer Choices
# D. drop profile (Correct Answer)
* Why?
* A drop profile defines when packets should be dropped based on the queue fill level.
* Random Early Detection (RED) or Tail Drop can be used to manage congestion by discarding lower-priority packets first.
* Drop profiles are configured under the scheduler to determine how aggressive packet dropping should be during congestion.
* Example Juniper Configuration:
schedulers {
best-effort {
drop-profile low-drop;
}
}
drop-profiles {
low-drop {
fill-level 80 drop-probability 50;
}
}
* fill-level 80 # When the queue reaches 80% full, packet drops begin.
* drop-probability 50 # There is a 50% chance of dropping packets once the threshold is reached.
# Official Juniper Documentation Reference:
# Junos Class of Service Configuration Guide
"A drop profile determines how packets are discarded based on the queue fill level, allowing control over congestion behavior." Why the Other Options Are Incorrect?
# A. buffer size (Incorrect)
* Why?
* The buffer size determines how many packets the queue can store before congestion occurs.
* A larger buffer can delay drops, but it does not actively control dropping behavior.
* It affects latency rather than controlling packet drops.
# B. priority (Incorrect)
* Why?
* Priority controls which queue gets serviced first, not how drops are handled.
* Higher priority queues are serviced before lower-priority queues, but this does not prevent congestion-related drops.
# C. shaping rate (Incorrect)
* Why?
* Shaping limits the maximum transmission rate of the queue.
* While shaping helps reduce congestion, it does not control which packets get dropped during congestion.
* Shaping is useful for traffic smoothing, but it does not actively drop packets based on queue fill levels.
# D. drop profile
* Controls packet drops based on queue congestion.
* Defines RED (Random Early Detection) or Tail Drop mechanisms.
* Directly influences drop probability as the queue fills up.
# Official Juniper Reference:
"Drop profiles are used to manage congestion by determining when and how aggressively packets are dropped based on queue fill level."
質問 # 62
You are configuring a BGP signaled Layer 2 VPN across your MPLS enabled core network. Your PE-2 device connects to two sites within the s VPN In this scenario, which statement is correct?
- A. By default on PE-2, the site's local ID is automatically assigned a value of 0 and must be configured to match the total number of attached sites.
- B. You must create a unique Layer 2 VPN routing instance for each site on the PE-2 device.
- C. By default on PE-2, the remote site IDs are automatically assigned based on the order that you add the interfaces to the site configuration.
- D. You must use separate physical interfaces to connect PE-2 to each site.
正解：C
解説：
Explanation
BGP Layer 2 VPNs use BGP to distribute endpoint provisioning information and set up pseudowires between PE devices. BGP uses the Layer 2 VPN (L2VPN) Routing Information Base (RIB) to store endpoint provisioning information, which is updated each time any Layer 2 virtual forwarding instance (VFI) is configured. The prefix and path information is stored in the L2VPN database, which allows BGP to make decisions about the best path.
In BGP Layer 2 VPNs, each site has a unique site ID that identifies it within a VFI. The site ID can be manually configured or automatically assigned by the PE device. By default, the site ID is automatically assigned based on the order that you add the interfaces to the site configuration. The first interface added to a site configuration has a site ID of 1, the second interface added has a site ID of 2, and so on.
Option D is correct because by default on PE-2, the remote site IDs are automatically assigned based on the order that you add the interfaces to the site configuration. Option A is not correct because by default on PE-2, the site's local ID is automatically assigned a value of 0 and does not need to be configured to match the total number of attached sites. Option B is not correct because you do not need to create a unique Layer 2 VPN routing instance for each site on the PE-2 device. You can create one routing instance for all sites within a VFI. Option C is not correct because you do not need to use separate physical interfaces to connect PE-2 to each site. You can use subinterfaces or service instances on a single physical interface.
質問 # 63
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. On the multi-access network, each router forms an adjacency to every other router on the segment
- D. A router with a priority of 1 wins the DIS election over a router with a priority of 10.
正解：A、C
解説：
Option A (Correct):
In IS-IS, the Designated Intermediate System (DIS) is elected based on the highest configured priority (as defined in Junos OS).
If priorities are equal, the router with the highest MAC address becomes the DIS.
A priority value of 10 will always override a lower priority (e.g., 1).
Reference:
Option C (Correct):
On a multi-access network (e.g., Ethernet), all IS-IS routers form adjacencies with every other router on the segment.
Unlike OSPF, IS-IS does not restrict adjacencies to only the DIS.
The DIS is responsible for creating a pseudonode LSP to represent the broadcast network, but full mesh adjacencies are maintained.
Why Other Options Are Incorrect:
Option B: Incorrect. Higher priority always wins the DIS election. A priority of 1 cannot override a priority of 10.
Option D: Incorrect. IS-IS routers form adjacencies with all neighbors, not just the DIS.
Key Takeaways:
DIS Election: Prioritizes highest numerical value (e.g., 10 > 1).
Adjacency Behavior: Full mesh adjacencies are maintained, unlike OSPF.
DIS Role: Primarily for generating pseudonode LSPs and optimizing flooding, not adjacency restriction.
For further details, refer to Juniper's official IS-IS documentation:
Juniper IS-IS Configuration Guide.
https://www.juniper.net/documentation/us/en/software/junos/is-is/topics/concept/routing-protocol-is-is-security-designated-router-understanding.html
質問 # 64
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. On the multi-access network, each router forms an adjacency to every other router on the segment.
- D. A router with a priority of 1 wins the DIS election over a router with a priority of 10.
正解：A、C
質問 # 65
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 RP2 for group 224.1 1 1
- B. Source1 will use RP1 and Receiver1 will use RP1 for group 224.1.1.1.
- C. Source2 will use RP1 and Receiver2 will use RP1 for group 224.2.2.2.
- D. Source2 will use RP2 and Received will use RP2 for group 224.2.2.2.
正解：B、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 # 66
Exhibit
Referring to the exhibit, which two statements are true? (Choose two.)
- A. This is an EVPN Type-2 route.
- B. The device advertising this route into EVPN is 192.168.101.5.
- C. The devices advertising this route into EVPN are 10 0 2 12 and 10.0.2.22.
- D. This route is learned through EBGP
正解：A、B
解説：
This is an EVPN Type-2 route, also called a MAC/IP advertisement route, that is used to advertise host IP and MAC address information to other VTEPs in an EVPN network. The route type field in the EVPN NLRI has a value of 2, indicating a Type-2 route. The device advertising this route into EVPN is 192.168.101.5, which is the IP address of the VTEP that learned the host information from the local CE device. This IP address is carried in the MPLS label field of the route as part of the VXLAN encapsulation.
質問 # 67
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