Designing Cisco Enterprise Networks (ENSLD) practice questions

1. Question 1 of 25

   An engineer must design a solution to connect a customer to the Internet. The solution will include a Layer 3 circuit with a CIR of 50 Mbps from the service provider. The hand-off from the provider's switch to the customer's router is 1Gbps. Which solution should the engineer include to prevent potential issues with choppy voice traffic?

   • AReduce the bandwidth of the connection to the router.
   • BImplement hierarchical QoS with a parent policing policy.
   • CImplement hierarchical QoS with a parent shaping policy.
   • DAdd a bandwidth statement to the router interface.

   Show answer

   Correct answer: C

   How others answered

   • C54%
   • B46%

   Only 54% agreed on this answer — treat it as contested rather than settled.

   Explanation

   The answer is C. Always SHAPE on egress towards a service provider in the parent policy, then use child policies to set priorities as you see fit (in this case VoiP). Generally, shaping = egress (i.e. towards ISP), policing = ingress (this is how ISPs drop traffic that exceed the CIR you are paying them for). Sources: https://www.cisco.com/c/en/us/support/docs/quality-of-service-qos/qos-policing/19645-policevsshape.html#anc17

   Adapted from community discussion by jzzmth · 2023-03-08 · 5 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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   • cisco.com documentation
   • Cisco documentation

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   Question 1 discussion

   These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

   1. J

      jzzmth

      2023-03-08

      Selected C5 upvotes

      The answer is C. Always SHAPE on egress towards a service provider in the parent policy, then use child policies to set priorities as you see fit (in this case VoiP). Generally, shaping = egress (i.e. towards ISP), policing = ingress (this is how ISPs drop traffic that exceed the CIR you are paying them for). Sources: https://www.cisco.com/c/en/us/support/docs/quality-of-service-qos/qos-policing/19645-policevsshape.html#anc17

   2. C

      Clauster

      2023-08-04

      Selected C2 upvotes

      Oh men after analyzing this question i just realized something, they want us to set this QoS on our Router, not the ISP router, and then it clicked, Shaping is using on Egress Interfaces and Policing is configured on Ingress Interfaces, in this case Shaping will be setup on our Router, but we can't do policing because we are not managing traffic into our network, we are managing packets out of our router (Egress) for the voice going out. This is Shaping. Makes sense

   3. A

      andrewChan

      2022-10-26

      3 upvotes

      sorry a bit misunderstand the feature. https://www.cisco.com/c/en/us/support/docs/quality-of-service-qos/qos-policing/19645-policevsshape.html#anc17 in this case the answer should be C, not related to the CIR but if parent policy-map use police, it will override priority of voice service in the child policy-map

   4. C

      cerifyme85

      2023-03-27

      Selected C2 upvotes

      https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_plcshp/configuration/xe-16/qos-plcshp-xe-16-book/qos-plcshp-oview.html#:~:text=in%20the%20bucket.-,Traffic%20Policing,the%20traffic%20to%20the%20speed%20of%20the%20interface%20receiving%20the%20packet.,-Was%20this%20Document

2. Question 2 of 25

   An engineer must propose a solution for a campus network that includes the capability to create multiple Layer 3 virtual networks. Each network must have its own addressing structure and routing table for data forwarding. The solution must be scalable to support hundreds of virtual networks and allow simple configuration and management with minimal administrative overhead. Which solution does the engineer recommend?

   • Ahop-by-hop EVN
   • Bmultihop MPLS core
   • Cmultihop IPsec tunneling
   • Dhop-by-hop VRF-Lite

   Show answer

   Correct answer: B

   How others answered

   • B52%
   • D33%

   Only 52% agreed on this answer — treat it as contested rather than settled.

   Explanation

   I found the Cisco White Papers that talks about EVNs - You are correct when you say we can only use 32VNs, but this is only limited to one IP Infrastructure. Since each Branch will have it's own IP Infrastructure then we can do 32VNs at each branch, so if you have 10 branches x 32VNs that puts you well over hundreds of VNs that can be supported with this feature. - MPLS Core requires tons of Administrative Overhead. - VRF Lite supports up to 8 VNs. - Only Clear answer here is A, keep in mind they also mention Easy to configure, EVN is known for easy configuration.

   Adapted from community discussion by Clauster · 2023-08-13 · 5 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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   Question 2 discussion

   These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

   1. C

      cryptonite

      2022-02-23

      Selected B7 upvotes

      I disagree on EVN because it has a limitation of 32 VNs. The questions says can scale to hundreds of Virtual Network

   2. C

      Clauster

      2023-08-13

      5 upvotes

      I found the Cisco White Papers that talks about EVNs - You are correct when you say we can only use 32VNs, but this is only limited to one IP Infrastructure. Since each Branch will have it's own IP Infrastructure then we can do 32VNs at each branch, so if you have 10 branches x 32VNs that puts you well over hundreds of VNs that can be supported with this feature. - MPLS Core requires tons of Administrative Overhead. - VRF Lite supports up to 8 VNs. - Only Clear answer here is A, keep in mind they also mention Easy to configure, EVN is known for easy configuration.

   3. H

      Hope66

      2021-08-20

      2 upvotes

      I think A: Hop-by-hop easy virtual network (EVN) based: Hop-by-hop VRF-lite is manageable for networks with fewer numbers of virtual networks and fewer numbers of hops in a virtual network path. However, when the number of logical networks (virtual/tenants) increases, there will be a high degree of operational complexity to create and configure the interface or subinterface per VN. EVN provides the same benefits for guaranteeing traffic separation with more simplified operations. In other words, EVN builds on VRF-Lite concepts and capabilities and provides additional benefits, including the following: ■ EVN offers better end-to-end VN scalability compared to the classic hop-by-hop 802.1Q-based solution. ■ EVN offers simplified configuration and management. ■ EVN offers the capability to provision shared services among different logical groups.

   4. P

      PicoOstrava

      2024-11-10

      Selected B1 upvote

      MPLS Core (B): MPLS is designed to scale and can handle the segmentation of hundreds of virtual networks much more effectively than VRF-Lite. MPLS allows for easier management of large-scale environments, especially when multiple virtual networks need to be created and routed independently. MPLS provides both scalability and flexibility, making it a good fit for large deployments with multiple virtual networks. • VRF-Lite (D): While VRF-Lite can work in smaller networks, it doesn’t scale well for hundreds of virtual networks. It can cause administrative overhead and performance degradation as the number of VRFs increases. It is more suited for smaller to medium-sized environments rather than large-scale deployments.

3. Question 3 of 25

   A customer is discussing QoS requirements with a network consultant. The customer has specified that end-to-end path verification is a requirement. Which QoS solution meets this requirement?

   • AIntServ model with RSVP to support the traffic flows
   • BDiffServ model with PHB to support the traffic flows
   • Cmarking traffic at the access layer with DSCP to support the traffic flows
   • Dmarking traffic at the access layer with CoS to support the traffic flows

   Show answer

   Correct answer: A

   How others answered

   • A100%

   Explanation

   "The main difference between integrated services and differentiated services is that >, (while differential services mark the packets with priority and send it to the network without prior reservation.) "

   Adapted from community discussion by Sickcnt · 2023-10-20 · 2 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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   Question 3 discussion

   These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

   1. S

      Sickcnt

      2023-10-20

      Selected A2 upvotes

      "The main difference between integrated services and differentiated services is that >, (while differential services mark the packets with priority and send it to the network without prior reservation.) "

   2. L

      Lungful

      2024-08-18

      Selected A1 upvote

      A is correct. https://learningnetwork.cisco.com/s/question/0D53i00000KsqtXCAR/qos-architecture-models-intserv-vs-diffserv

   3. C

      certstudent2016

      2023-04-26

      1 upvote

      A is correct https://www.cisco.com/en/US/technologies/tk543/tk766/technologies_white_paper09186a00800a3e2f.html

4. Question 4 of 25

   Which QoS feature responds to network congestion by dropping lower priority packets?

   • ACBWFQ
   • Btail drop
   • CWRED
   • Dstrict priority

   Show answer

   Correct answer: C

   How others answered

   • C100%

   Explanation

   I think the answer is C WRED can selectively discard lower priority traffic when the interface begins to get congested and provide differentiated performance characteristics for different classes of service. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_conavd/configuration/15-mt/qos-conavd-15-mt-book/qos-conavd-oview.html#:~:text=WRED%20can%20selectively%20discard%20lower,for%20different%20classes%20of%20service.

   Adapted from community discussion by Benzzyy · 2022-05-13 · 5 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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   • Cisco documentation
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   Question 4 discussion

   These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

   1. B

      Benzzyy

      2022-05-13

      5 upvotes

      I think the answer is C WRED can selectively discard lower priority traffic when the interface begins to get congested and provide differentiated performance characteristics for different classes of service. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_conavd/configuration/15-mt/qos-conavd-15-mt-book/qos-conavd-oview.html#:~:text=WRED%20can%20selectively%20discard%20lower,for%20different%20classes%20of%20service.

   2. D

      danpho123

      2022-12-13

      1 upvote

      CBWFQ is a scheduling mechanism used to provide a minimum bandwidth guarantee to traffic classes during times of network congestion at an interface. Each of the CBWFQ queues is assigned a weight, and the packets are served from the queues based upon the weight of the queue. WRED can selectively discard lower priority traffic when the interface begins to get congested and provide differentiated performance characteristics for different classes of service. https://www.cisco.com/c/en/us/td/docs/ios/qos/configuration/guide/12_2sr/qos_12_2sr_book/congestion_avoidance.html

   3. J

      J2J2J2J

      2024-06-18

      Selected C1 upvote

      WRED makes early detection of congestion possible and provides a means for handling multiple classes of traffic. WRED can selectively discard lower priority traffic when the router begins to experience congestion and provide differentiated performance characteristics for different classes of service.

   4. D

      danieldarq

      2024-07-01

      1 upvote

      is C: Congestion Avoidance monitors network traffic loads in an effort to anticipate and avoid congestion. Congestion Avoidance is achieved through packet dropping. Typically, congestion avoidance is implemented on output interfaces where high-speed links intersect with low speed links. Congestion Avoidance in Cisco products uses Weighted Random Early Detection (WRED) to avoid congestion by dropping low priority packets and allowing high priority packets to continue on their path.

5. Question 5 of 25

   Select 2

   An organization is designing a detailed QoS plan that limits bandwidth to specific rates. Which two parameters are supported by the traffic policing feature? (Choose two.)

   • Aviolating
   • Bmarking
   • Cshaping
   • Dbursting
   • Econforming

   Show answer

   Correct answer: A, E

   How others answered

   • AE100%

   Explanation

   When working with policing there are three categories that we can use to see if a packet conforms the traffic contract or not: Conforming Exceeding Violating

   Adapted from community discussion by [Removed] · 2023-05-15 · 3 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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   • Cisco documentation
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   • Cisco documentation
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   Question 5 discussion

   These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

   1. R

      Ranx01

      2021-08-08

      12 upvotes

      I also think it's A & E, the question is asking for the traffic "policing" feature.

   2. H

      Hamele0n

      2021-08-04

      6 upvotes

      I think it's A and E. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_plcshp/configuration/xe-3s/qos-plcshp-xe-3s-book/qos-plcshp-class-plc.html

   3. C

      certstudent2016

      2022-10-26

      Selected A, E3 upvotes

      A&E Correct https://www.cisco.com/c/en/us/support/docs/quality-of-service-qos/qos-policing/19645-policevsshape.html https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_plcshp/configuration/xe-17/qos-plcshp-xe-17-book/qos-plcshp-trfc-plc.pdf

   4. [

      [Removed]

      2023-05-15

      Selected A, E3 upvotes

      When working with policing there are three categories that we can use to see if a packet conforms the traffic contract or not: Conforming Exceeding Violating

6. Question 6 of 25

   An engineer is designing a multicast network for a financial application. Most of the multicast sources also receive multicast traffic (many-to-many deployment model). To better scale routing tables, the design must not use source trees. Which multicast protocol satisfies these requirements?

   • APIM-SSM
   • BPIM-SM
   • CMSDP
   • DBIDIR-PIM

   Show answer

   Correct answer: D

   How others answered

   • D100%

   Explanation

   Bidir-PIM is designed to be used for many-to-many applications within individual PIM domains. Multicast groups in bidirectional PIM mode can scale to an arbitrary number of sources without incurring overhead due to the number of sources. So answer is D -> BIDIR PIM

   Adapted from community discussion by Xavi07 · 2023-07-08 · 3 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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   Question 6 discussion

   These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

   1. L

      luisjuradoledesma

      2023-01-30

      4 upvotes

      In support of the use of BIDIR-PIM in financial applications: https://www.cisco.com/c/dam/en/us/products/collateral/ios-nx-os-software/multicast-enterprise/prod_white_paper0900aecd80310db2.pdf

   2. K

      Kakat

      2023-07-31

      4 upvotes

      https://www.cisco.com/c/dam/en/us/products/collateral/ios-nx-os-software/multicast-enterprise/prod_white_paper0900aecd80310db2.pdf BIDIR PIM uses shared tree.

   3. X

      Xavi07

      2023-07-08

      3 upvotes

      Bidir-PIM is designed to be used for many-to-many applications within individual PIM domains. Multicast groups in bidirectional PIM mode can scale to an arbitrary number of sources without incurring overhead due to the number of sources. So answer is D -> BIDIR PIM

   4. L

      luisjuradoledesma

      2023-01-29

      2 upvotes

      D - Actually PIM-SM creates shared trees (not source trees). However, BDIR-PIM eliminates the need for a first-hop route to encapsulate data packets being sent to the RP - then scales better in a "many-to-many" deployment

7. Question 7 of 25

   The customer solution requires QoS to support streaming multimedia over a WAN. An architect chooses to use Per-Hop Behavior. Which solution should the engineer use to classify and mark traffic traveling between branch sites?

   • ACBWFQ with DSCP AF2
   • BLLQ with DSCP EF
   • CCBWFQ with DSCP AF3
   • DLLQ with DSCP AF4

   Show answer

   Correct answer: C

   How others answered

   • C100%

   Explanation

   LLQ with EF seems way too strict for STREAMING multimedia (where one can actually take advantage of buffering). Judging by the various Cisco QoS baseline docs (even though the ones below are quite old), streaming video should be somewhere at AF3x/CS4. So I would go with C. https://www.cisco.com/en/US/technologies/tk543/tk759/technologies_white_paper0900aecd80295a9b.pdf https://community.cisco.com/t5/collaboration-voice-and-video/cisco-qos-baseline-classification-and-marking-and-mapping/ta-p/3108355

   Adapted from community discussion by bogd · 2022-08-22 · 2 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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   Question 7 discussion

   These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

   1. B

      bogd

      2022-08-22

      Selected C2 upvotes

      LLQ with EF seems way too strict for STREAMING multimedia (where one can actually take advantage of buffering). Judging by the various Cisco QoS baseline docs (even though the ones below are quite old), streaming video should be somewhere at AF3x/CS4. So I would go with C. https://www.cisco.com/en/US/technologies/tk543/tk759/technologies_white_paper0900aecd80295a9b.pdf https://community.cisco.com/t5/collaboration-voice-and-video/cisco-qos-baseline-classification-and-marking-and-mapping/ta-p/3108355

   2. N

      namibdigger

      2023-02-01

      Selected C2 upvotes

      i go for 'C' - Official Cert Guide states 'Multimedia Streaming = AF3' (p. 311) and LLQ is too strong for Multimedia to implement (only for 'real time' like Voice or videoconferencing)

   3. [

      [Removed]

      2023-05-17

      Selected C2 upvotes

      https://www.ciscopress.com/articles/article.asp?p=2159353&seqNum=3

   4. C

      cwoolie

      2022-09-28

      1 upvote

      I think answer is correct....Low Latency Queuing (LLQ) is the preferred queuing policy for VoIP audio. Given the stringent delay/jitter sensitive requirements of TP and the need to synchronize audio and video for CUVA, priority (LLQ) queuing is the recommended for all video traffic as well. Note that, for video, priority bandwidth is generally fudged up by 20% to account for the overhead.

8. Question 8 of 25

   An engineer needs a standards-driven YANG model to manage a multivendor network environment. Which model should the engineer choose?

   • ANative
   • BOpenConfig
   • CIETF
   • DIEEE NETCONF

   Show answer

   Correct answer: B

   How others answered

   • B62%
   • C38%

   Only 62% agreed on this answer — treat it as contested rather than settled.

   Explanation

   Answer is 100% B Page 387 OCG Book: OpenConfig is a group of network operators working on developing programmable interfaces and tools for managing networks in a vendor-neutral way using software-defined networking concepts and model-driven management and operations. OpenConfig focuses on building consistent sets of vendor-neutral data models written in YANG to support operational needs and requirements from various network operators

   Adapted from community discussion by Clauster · 2023-08-04 · 2 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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   Question 8 discussion

   These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

   1. C

      Clauster

      2023-08-04

      Selected B2 upvotes

      Answer is 100% B Page 387 OCG Book: OpenConfig is a group of network operators working on developing programmable interfaces and tools for managing networks in a vendor-neutral way using software-defined networking concepts and model-driven management and operations. OpenConfig focuses on building consistent sets of vendor-neutral data models written in YANG to support operational needs and requirements from various network operators

   2. E

      electro165

      2023-08-23

      1 upvote

      The correct answer is B: OpenConfig For managing a multivendor network environment with a standards-driven YANG model, the engineer should choose the "OpenConfig" model. OpenConfig is an industry initiative that aims to provide a vendor-neutral and standardized YANG data model for network device configuration and monitoring. It's designed to work across different vendors' equipment and to promote interoperability in a heterogeneous network environment.

   3. N

      namibdigger

      2022-08-01

      2 upvotes

      According to Student learning guide and Cert Guide C is correct - where it's stating that IETF is developing and updating several YANG models - which means they are vendor independant. So C seems right.

   4. E

      Emily23

      2023-06-13

      1 upvote

      The YANG Model Coordination Group, for example, has been spending time on the inventory of YANG models in the industry, tooling aspects, training and education of NETCONF, YANG, pyang, and the model coordination for the IETF. OpenConfig focuses on building consistent sets of vendor-neutral data models written in YANG to support operational needs and requirements from various network operators.

9. Question 9 of 25

   A router running ISIS is showing high CPU and bandwidth utilization. An engineer discovers that the router is configured as L1/L2 and has L1 and L2 neighbors. Which step optimizes the design to address the issue?

   • AMake this router a DIS for each of the interfaces
   • BDisable the default behavior of advertising the default route on the L1/L2 router
   • CConfigure the router to be either L1 or L2
   • DConfigure each interface as either L1 or L2 circuit type

   Show answer

   Correct answer: D

   How others answered

   • D86%

   Explanation

   You have an IS-IS router that is performing both L1 and L2 routing and has both L1 and L2 neighbors. How would you optimize the router's operation to conserve bandwidth and router resources? Configure each interface as either L1 or L2 circuit type, depending on the type of adjacency needed out that interface. The command to do this is, at the interface configuration mode, isis circuit-type [level-1 | level-1-2 | level-2-only]. This prevents unnecessary hellos from being sent out interfaces, which uses bandwidth and router resources. https://www.ciscopress.com/articles/article.asp?p=101756

   Adapted from community discussion by MaryGalanP · 2021-10-25 · 11 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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   Question 9 discussion

   These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

   1. M

      MaryGalanP

      2021-10-25

      11 upvotes

      You have an IS-IS router that is performing both L1 and L2 routing and has both L1 and L2 neighbors. How would you optimize the router's operation to conserve bandwidth and router resources? Configure each interface as either L1 or L2 circuit type, depending on the type of adjacency needed out that interface. The command to do this is, at the interface configuration mode, isis circuit-type [level-1 | level-1-2 | level-2-only]. This prevents unnecessary hellos from being sent out interfaces, which uses bandwidth and router resources. https://www.ciscopress.com/articles/article.asp?p=101756

   2. A

      andrewChan

      2022-10-31

      Selected D2 upvotes

      https://www.cisco.com/c/en/us/td/docs/ios/iproute_isis/command/reference/irs_book/irs_is1.html "You have an IS-IS router that is performing both L1 and L2 routing and has both L1 and L2 neighbors. How would you optimize the router's operation to conserve bandwidth and router resources? Configure each interface as either L1 or L2 circuit type, depending on the type of adjacency needed out that interface. The command to do this is, at the interface configuration mode, isis circuit-type [level-1 | level-1-2 | level-2-only]. This prevents unnecessary hellos from being sent out interfaces, which uses bandwidth and router resources."

   3. C

      Clauster

      2023-06-03

      Selected D2 upvotes

      I was finally able to find the answer We all know that answers A and B make no sense. C: This answer is incorrect, it states that the router is L1/L2 and it's got L1 Neighbor and an L2 Neighbor, If you set the router to L1 it will make an adjacency with L1 but not L2, L1 Routers will become adjacent with L1 and L1/L2s but not with L2s only: https://www.cisco.com/c/en/us/support/docs/ip/integrated-intermediate-system-to-intermediate-system-is-is/200293-IS-IS-Adjacency-and-Area-Types.html The Answer is D: You can configure an interface as L1 or L2, this will reduce the amount of Hellos it's sent therefor improves performance.

   4. I

      iLikeHamburgers

      2022-12-07

      Selected D1 upvote

      I feel the answer is D. Answer C would actually be the best answer, because running 2 databases would consume the most resources. However this is making the assumption that we have the option of changing this particular router to a Level 1, or Level 2. The question doesn't state that this is an option. If the question stated, "What is the best possible way to cut down on router resources.." and left it at that, I would be inclined to say C is the answer. However since it doesn't, and we have to work with that we have (A router running both L1/L2), answer D is the best choice given the circumstances. In a real world scenario, we would apply option D. If that didn't fix the issue we would resort to option C.

10. Question 10 of 25

    A client is moving to Model-Driven Telemetry and requires periodic updates. What must the network architect consider with this design?

    • AUpdates that contain changes within the data are sent only when changes occur.
    • BEmpty data subscriptions do not generate empty update notifications.
    • CPeriodic updates include a full copy of the data that is subscribed to.
    • DThe primary push update is sent immediately and cannot be delayed.

    Show answer

    Correct answer: C

    How others answered

    • C100%

    Explanation

    Agree - C is correct - Periodic updates contain a full copy of the subscribed data element or table for all supported transport protocols https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/prog/configuration/166/b_166_programmability_cg/model_driven_telemetry.html

    Adapted from community discussion by luisjuradoledesma · 2022-01-30 · 4 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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    Question 10 discussion

    These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

    1. L

       luisjuradoledesma

       2022-01-30

       4 upvotes

       Agree - C is correct - Periodic updates contain a full copy of the subscribed data element or table for all supported transport protocols https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/prog/configuration/166/b_166_programmability_cg/model_driven_telemetry.html

    2. N

       namibdigger

       2023-08-01

       Selected C2 upvotes

       I Agree on C but find it difficult to see the difference in A (ENSLD Cert Guide p 390: on-change subscription streams out data only when a change in the data has occured' -differnce may be in 'Periodic subscription' which is not the usual approach for A

    3. C

       Clauster

       2024-08-09

       Selected C1 upvote

       Answer is C I was able to find the documentation on Cisco WhitePages https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/prog/configuration/173/b_173_programmability_cg/model_driven_telemetry.html

    4. [

       [Removed]

       2023-05-15

       Selected C1 upvote

       With periodic publications, the network device continuously sends data for the lifetime of that configured subscription. ENSLD book pg 389

11. Question 11 of 25

    An infrastructure team is concerned about the shared memory utilization of a device, and for this reason, they need to monitor the device state. Which solution limits impact on the device and provides the required data?

    • AIPFIX
    • Bstatic telemetry
    • Con-change subscription
    • Dperiodic subscription

    Show answer

    Correct answer: D

    How others answered

    • D75%
    • C25%

    Explanation

    Memory usage is measured in bytes and changes very frequently. On-change subscription will send data almost non-stop. In this case periodic change is more suitable.

    Adapted from community discussion by zzmejce · 2022-12-20 · 7 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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    Question 11 discussion

    These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

    1. Z

       zzmejce

       2022-12-20

       Selected D7 upvotes

       Memory usage is measured in bytes and changes very frequently. On-change subscription will send data almost non-stop. In this case periodic change is more suitable.

    2. G

       goku2020

       2020-12-01

       8 upvotes

       C is correct Change-on subscription have less impact, more specific to obtain information.

    3. L

       luisjuradoledesma

       2021-01-30

       3 upvotes

       C (change-on subscription) looks correct There are two types of subscriptions: periodic and on-change. With periodic subscription, data is streamed out to the destination at the configured interval. It continuously sends data for the lifetime of that subscription. With on-change, data is published only when a change in the data occurs such as when an interface or OSPF neighbor goes down. https://developer.cisco.com/docs/ios-xe/#!streaming-telemetry-quick-start-guide/streaming-telemetry

    4. C

       CKL_SG

       2023-05-29

       Selected D2 upvotes

       concerned about the shared memory utilization of a device, and for this reason, they need to monitor the device state question mention they are concerned and need to monitor, thus i believe D which is periodic subscription more suitable as they want to know memory utilization from time to time and For periodic subscriptions the update trigger is specified by time interval and an time for the report to be sent. rather than on-change subscription an update trigger occurs whenever a change in the subscribed information is detected

12. Question 12 of 25

    An engineer is designing a network for a customer running a wireless network with a common VLAN for all APs. The customer is experiencing unicast flooding in the Layer 2 network between the aggregation and access layers. The customer wants to reduce the flooding and improve convergence time. Which solution meets these requirements?

    • AMigrate all APs to a common Layer 2 access layer switch and run Layer 3 from the aggregation layer to all remaining access layer switches.
    • BAlign HSRP primary and STP root bridges and reduce ARP timers to match CAM timers on the aggregation layer switches.
    • CMigrate to a Layer 3 access campus design if the APs can run on separate VLANs.
    • DAlign HSRP primary and STP root bridges if the APs cannot run on separate VLANs.

    Show answer

    Correct answer: B

    How others answered

    • B57%
    • C43%

    Only 57% agreed on this answer — treat it as contested rather than settled.

    Explanation

    I think B The default ARP table aging time is 4 hours while the CAM holds the entries for only 5 minutes. The switch sends out a frame to all forwarding ports within the respective VLAN when the destination MAC address is aged out from the CAM table. You need a CAM aging timer greater or equal to the ARP timeout in order to prevent unicast flooding. https://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/71079-arp-cam-tableissues.html#:~:text=The%20default%20ARP%20table%20aging%20time%20is%204,ARP%20timeout%20in%20order%20to%20prevent%20unicast%20flooding.

    Adapted from community discussion by Hope66 · 2022-09-23 · 15 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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    Question 12 discussion

    These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

    1. H

       Hope66

       2022-09-23

       15 upvotes

       I think B The default ARP table aging time is 4 hours while the CAM holds the entries for only 5 minutes. The switch sends out a frame to all forwarding ports within the respective VLAN when the destination MAC address is aged out from the CAM table. You need a CAM aging timer greater or equal to the ARP timeout in order to prevent unicast flooding. https://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/71079-arp-cam-tableissues.html#:~:text=The%20default%20ARP%20table%20aging%20time%20is%204,ARP%20timeout%20in%20order%20to%20prevent%20unicast%20flooding.

    2. C

       CKL_SG

       2023-05-29

       Selected B1 upvote

       Spanning-tree protocol looping behavior, including blocked links, slow convergence, asymmetric forwarding, and switch CAM and ARP table tuning to address unicast flooding https://www.cisco.com/c/en/us/td/docs/solutions/CVD/Campus/cisco-campus-lan-wlan-design-guide.html

    3. R

       rted

       2024-07-03

       2 upvotes

       But B says "reduce ARP timers to match CAM timers". The flooding will still happen at same interval.

    4. X

       XalaGyan

       2023-02-04

       Selected B1 upvote

       Answer B is correct based on explanations provided by Hope66

13. Question 13 of 25

    Select 2

    A network engineer must design a multicast solution to prevent the spoofing of multicast streams and ensure efficient bandwidth utilization. The network will be merged with another multicast domain in the future, and the merge must require minimum effort. Which two solutions meet the customer requirements? (Choose two.)

    • APIM-SSM
    • BIGMPv3
    • CIGMPv2
    • DPIM-SM
    • EMSDP

    Show answer

    Correct answer: A, B

    How others answered

    • AB53%
    • DE40%

    Only 53% agreed on this answer — treat it as contested rather than settled.

    Explanation

    I too think it's A and B: "The ease of installation and operation of SSM makes it ideal for network operators, especially in those cases where content needs to be forwarded between multiple independent PIM domains (because there is no need to manage MSDP for SSM between PIM domains)." https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipmulti_pim/configuration/xe-16/imc-pim-xe-16-book/imc-ssm.html And without IGMPv3 you can't setup PIM-SSM

    Adapted from community discussion by jzzmth · 2023-09-22 · 5 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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    Question 13 discussion

    These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

    1. J

       jzzmth

       2023-09-22

       Selected A, B5 upvotes

       I too think it's A and B: "The ease of installation and operation of SSM makes it ideal for network operators, especially in those cases where content needs to be forwarded between multiple independent PIM domains (because there is no need to manage MSDP for SSM between PIM domains)." https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipmulti_pim/configuration/xe-16/imc-pim-xe-16-book/imc-ssm.html And without IGMPv3 you can't setup PIM-SSM

    2. T

       Tasabgd90

       2023-08-06

       Selected A, B3 upvotes

       I think it's A and B. Referring to this: https://www.cisco.com/c/en/us/td/docs/ios/solutions_docs/ip_multicast/Phase_2/mcst_p2.html https://www.researchgate.net/publication/221081564_IGMPv3-Based_Method_for_Avoiding_DoS_Attacks_in_Multicast-Enabled_Networks

    3. N

       neiker45

       2024-06-27

       1 upvote

       Nevermind, as per Jzzmth's documentation there is no need to manage MSDP for SSM between PIM domains.

    4. S

       SirPeter

       2024-03-03

       1 upvote

       YES, IGMPv3 supports SSM, whitch is source specific and thus prevent spoofing of source IP address.

14. Question 14 of 25

    

    Refer to the exhibit. An architect is designing a network for a customer supporting a Wake-on-LAN application. Which solution must the architect choose?

    • AIP directed-broadcasts on R1
    • Bspanning-tree uplinkfast on SW1
    • Cspanning-tree uplinkfast on SW2
    • DIP directed-broadcasts on R2

    Show answer

    Correct answer: D

    How others answered

    • D70%
    • A30%

    Only 70% agreed on this answer — treat it as contested rather than settled.

    Explanation

    As I understand "IP directed broadcast" must be supported on the last router to the destination subnet. Since the sleeping PC's dont have IP adresses, the machines must be calles awake by broadcast that behaves like an unicast untill they reach the destination network. There the directed broadcast is handled like a proper broadcast to wake all WOL machines. https://www.cisco.com/c/en/us/support/docs/switches/catalyst-3750-series-switches/91672-catl3-wol-vlans.html

    Adapted from community discussion by Reinier_veen · 2023-04-14 · 3 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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    Question 14 discussion

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    1. R

       Reinier_veen

       2023-04-14

       Selected D3 upvotes

       As I understand "IP directed broadcast" must be supported on the last router to the destination subnet. Since the sleeping PC's dont have IP adresses, the machines must be calles awake by broadcast that behaves like an unicast untill they reach the destination network. There the directed broadcast is handled like a proper broadcast to wake all WOL machines. https://www.cisco.com/c/en/us/support/docs/switches/catalyst-3750-series-switches/91672-catl3-wol-vlans.html

    2. D

       dgonzalezexamtopics

       2023-10-14

       4 upvotes

       From my point of view, it depends on which has to be the awake device/s. If Server, then should be A, because of being R1 on same subnet and then can redirect the IP broadcast directly. If are the PCs, as Reinier says, then should be D. I think that could make more sense to wake up the server, but with Cisco...who knows.

    3. E

       Eards

       2023-04-19

       Selected D3 upvotes

       Looking this up IP helper addresses are configured on R1 and Directed broadcasts on R2. So I think D is correct

    4. J

       jahax

       2024-07-13

       2 upvotes

       "supporting a Wake-on-LAN application". WoL is mostly for endpoints, and we have application server on drawing. It seems to be that we have applicaiton server that hosts WoL App and awake devices in LAN > thats why we need directed broadcast on R2 (D)

15. Question 15 of 25

    An engineer is designing a PIM Anycast RP solution between two data centers. The design must ensure that RP1 in DC1 and RP2 in DC2 inform each other about specific sources that have joined locally. Which solution must the engineer choose?

    • AProvision the RPs on the same IP subnet and extend the subnet at Layer 2 between data centers
    • BEnable MSDP between RPs using separate unique loopback interfaces
    • CEnable MSDP between RPs using the configured Anycast RP address
    • DNo action is required because PIM registers from the source will, by default, reach each RP

    Show answer

    Correct answer: B

    How others answered

    • B83%
    • C17%

    Explanation

    In Anycast RP, two or more RPs are configured with the same IP address on loopback interfaces. The Anycast RP loopback address should be configured with a 32-bit mask, making it a host address. All the downstream routers should be configured to "know" that the Anycast RP loopback address is the IP address of their local RP. IP routing automatically will select the topologically closest RP for each source and receiver. MSDP used for Anycast RP is an intradomain feature that provides redundancy and load-sharing capabilities. Enterprise customers typically use Anycast RP for configuring a Protocol Independent Multicast sparse mode (PIM-SM) network to meet fault tolerance requirements within a single multicast domain. https://www.cisco.com/c/en/us/td/docs/ios/solutions_docs/ip_multicast/White_papers/anycast.html#wp1029118

    Adapted from community discussion by andrewChan · 2023-04-27 · 4 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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    Question 15 discussion

    These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

    1. A

       andrewChan

       2023-04-27

       Selected B4 upvotes

       In Anycast RP, two or more RPs are configured with the same IP address on loopback interfaces. The Anycast RP loopback address should be configured with a 32-bit mask, making it a host address. All the downstream routers should be configured to "know" that the Anycast RP loopback address is the IP address of their local RP. IP routing automatically will select the topologically closest RP for each source and receiver. MSDP used for Anycast RP is an intradomain feature that provides redundancy and load-sharing capabilities. Enterprise customers typically use Anycast RP for configuring a Protocol Independent Multicast sparse mode (PIM-SM) network to meet fault tolerance requirements within a single multicast domain. https://www.cisco.com/c/en/us/td/docs/ios/solutions_docs/ip_multicast/White_papers/anycast.html#wp1029118

    2. N

       neiker45

       2024-07-02

       2 upvotes

       So you have the anycast address which will be separate from the address that MSDP is going to use. One might trip on that and think it's C because of it. It is B because it won't be using the anycast RP address.

    3. R

       Reinier_veen

       2023-04-18

       Selected B1 upvote

       https://www.cisco.com/c/en/us/support/docs/ip/ip-multicast/115011-anycast-pim.html " You need to have a loopback on each prospective RP router, which is different than the loopback that is being used as the RP address."

    4. A

       andrewChan

       2023-04-27

       1 upvote

       to configure MSDP / anycast RP 2 loopback address required, a share RP address on all Anycast RP routers a unique loopback address on each MSDP router, for peering

16. Question 16 of 25

    Which design achieves SD-WAN control plane redundancy?

    • AConfiguring BFD on the WAN Edge routers
    • BUsing multiple instances of vManage in clusters
    • CDeploying using a virtual platform like UCS or CSP
    • DManaging the underlay network with OMP

    Show answer

    Correct answer: D

    How others answered

    • D50%
    • B43%

    Only 50% agreed on this answer — treat it as contested rather than settled.

    Explanation

    Also going for "D" based on the link provided by Hope66. "To provide a resilient control plane, the Cisco SD-WAN Overlay Management Protocol (OMP) regularly monitors..." --> Control plane "For data plane resiliency, the Cisco SD-WAN software implements standard protocol mechanisms, specifically Bidirectional Forwarding Detection (BFD)..." --> Data plane

    Adapted from community discussion by johnu329 · 2022-10-11 · 3 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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    Question 16 discussion

    These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

    1. J

       johnu329

       2022-10-11

       Selected D3 upvotes

       Also going for "D" based on the link provided by Hope66. "To provide a resilient control plane, the Cisco SD-WAN Overlay Management Protocol (OMP) regularly monitors..." --> Control plane "For data plane resiliency, the Cisco SD-WAN software implements standard protocol mechanisms, specifically Bidirectional Forwarding Detection (BFD)..." --> Data plane

    2. A

       andrewChan

       2022-10-27

       Selected D1 upvote

       https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/ha-scaling/ios-xe-17/high-availability-book-xe/m-high-availability-and-scaling.html Software mechanisms ensure rapid recovery from a failure. To provide a resilient control plane, the Cisco SD-WAN Overlay Management Protocol (OMP) regularly monitors the status of all Cisco IOS XE SD-WAN devices in the network and automatically adjusts to changes in the topology as devices join and leave the network. For data plane resiliency, the Cisco SD-WAN software implements standard protocol mechanisms, specifically Bidirectional Forwarding Detection (BFD), which runs on the secure IPsec tunnels between routers. - A. BFD used for data plane resilience - D. OMP also monitors devices and adjust the network topology (network devcies are belong to underlay)

    3. C

       Clauster

       2023-08-06

       1 upvote

       I really need to be careful, the correct answer is D, thank god i came back and revisit. Here i found the answer: Software mechanisms ensure rapid recovery from a failure. To provide a resilient control plane, the Cisco SD-WAN Overlay Management Protocol (OMP) regularly monitors the status of all Cisco vEdge devices in the network and automatically adjusts to changes in the topology as devices join and leave the network. For data plane resiliency, the Cisco SD-WAN software implements standard protocol mechanisms, specifically Bidirectional Forwarding Detection (BFD), which runs on the secure IPsec tunnels between routers. https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/optimization-ha/vedge/network-optimization-high-availability-book/high-availability.html

    4. H

       Hope66

       2022-09-04

       3 upvotes

       I think D : https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/optimization-ha/vedge/network-optimization-high-availability-book/high-availability.html

17. Question 17 of 25

    A network engineer must design an MSDP multicast solution to provide RP resilience in a network with two separate domains. Also, multicast sources and receivers must register with the local RP. Which solution must the engineer choose?

    • AConfigure the RP has value to 0, and traffic will route to the closest RP
    • BConfigure the RP loopback interface with the same IP address/32, and traffic will route to the closest RP
    • CConfigure the RP group ranges to split the multicast traffic, and traffic will route to the longest match
    • DConfigure the RP priority with the same value, and traffic will route to the closest RP

    Show answer

    Correct answer: B

    How others answered

    • B100%

    Explanation

    I think D Two or more RPs are configured with the same IP address (for example, 10.0.0.1) on loopback interfaces. The loopback address should be configured with a 32-bit mask. All the downstream routers are configured so that they know that 10.0.0.1 is the IP address of their local RP. IP routing automatically selects the topologically closest RP for each source and receiver. https://www.cisco.com/c/en/us/td/docs/ios/solutions_docs/ip_multicast/Phase_1/mcstmsdp/mcst_p1.html

    Adapted from community discussion by Hope66 · 2023-10-16 · 2 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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    Question 17 discussion

    These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

    1. S

       Sickcnt

       2023-10-22

       Selected B1 upvote

       Both can be true and correct because if you check the link: https://www.cisco.com/c/en/us/support/docs/ip/ip-multicast/115011-anycast-pim.html Relevant running configurations Nexus 1 relevant configuration: ip pim rp-address 10.1.1.1 group-list 224.0.0.0/4 ip pim anycast-rp 10.1.1.1 192.168.1.1 ip pim anycast-rp 10.1.1.1 192.168.2.2 interface loopback1 ip address 192.168.1.1/32 ip router ospf 1 area 0.0.0.0 ip pim sparse-mode interface loopback7 ip address 10.1.1.1/32 ip router ospf 1 area 0.0.0.0 ip pim sparse-mode interface Ethernet9/2 ip address 10.7.7.1/24 ip router ospf 1 area 0.0.0.0 ip pim sparse-mode interface Ethernet9/3 ip address 172.16.1.2/24 ip router ospf 1 area 0.0.0.0 ip pim sparse-mode

    2. S

       SpicyMochi

       2024-04-27

       Selected B2 upvotes

       Option B is the correct answer because Anycast RP is a technique that allows multiple RPs to share the same IP address. By configuring the RP loopback interface with the same IP address/32 in both domains, multicast traffic can be forwarded to the closest RP in each domain. This allows for RP redundancy and load sharing, ensuring that multicast traffic continues to flow even if one of the RPs fails.

    3. S

       Sickcnt

       2023-10-22

       1 upvote

       Nexus 2 relevant configuration: ip pim rp-address 10.1.1.1 group-list 224.0.0.0/4 ip pim ssm range 232.0.0.0/8 ip pim anycast-rp 10.1.1.1 192.168.1.1 ip pim anycast-rp 10.1.1.1 192.168.2.2 interface loopback1 ip address 192.168.2.2/32 ip router ospf 1 area 0.0.0.0 ip pim sparse-mode interface loopback7 ip address 10.1.1.1/32 ip router ospf 1 area 0.0.0.0 ip pim sparse-mode interface Ethernet9/2 ip address 10.7.7.2/24 ip router ospf 1 area 0.0.0.0 ip pim sparse-mode ----------------------------- This is exactly what we need here: ip pim anycast-rp 10.1.1.1 192.168.1.1 ip pim anycast-rp 10.1.1.1 192.168.2.2 (10.1.1.1 is the "loopback 7" for both of the devices -> Which is the same -> Question 174) (192.168.1.1 / 192.168.2.2 is their "Loopback 1" which should be a diverse loopback address for each RP -> Question 181)

    4. H

       Hope66

       2023-10-16

       2 upvotes

       I think D Two or more RPs are configured with the same IP address (for example, 10.0.0.1) on loopback interfaces. The loopback address should be configured with a 32-bit mask. All the downstream routers are configured so that they know that 10.0.0.1 is the IP address of their local RP. IP routing automatically selects the topologically closest RP for each source and receiver. https://www.cisco.com/c/en/us/td/docs/ios/solutions_docs/ip_multicast/Phase_1/mcstmsdp/mcst_p1.html

18. Question 18 of 25

    Which queuing structure is used on SD-WAN Edge routers?

    • AFIFO
    • BLLQ+WFQ
    • C1P-4Q-2T
    • DPriority

    Show answer

    Correct answer: B

    How others answered

    • B83%
    • C17%

    Explanation

    https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/qos/vEdge-20-x/qos-book/forwarding-qos.html On Cisco vEdge devices and Cisco IOS XE SD-WAN devices, each interface has eight queues, which are numbered 0 to 7. Queue 0 is reserved, and is used for both control traffic and low-latency queuing (LLQ) traffic. For LLQ, any class that is mapped to queue 0 must also be configured to use LLQ. Queues 1 to 7 are available for data traffic, and the default scheduling for these seven queues is weighted round-robin (WRR). For these queues, you can define the weighting according to the needs of your network. When QoS is not configured for data traffic, queue 2 is the default queue. LLQ+WRR - but no such option.

    Adapted from community discussion by [Removed] · 2023-09-26 · 6 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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    Question 18 discussion

    These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

    1. [

       [Removed]

       2023-09-26

       6 upvotes

       https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/qos/vEdge-20-x/qos-book/forwarding-qos.html On Cisco vEdge devices and Cisco IOS XE SD-WAN devices, each interface has eight queues, which are numbered 0 to 7. Queue 0 is reserved, and is used for both control traffic and low-latency queuing (LLQ) traffic. For LLQ, any class that is mapped to queue 0 must also be configured to use LLQ. Queues 1 to 7 are available for data traffic, and the default scheduling for these seven queues is weighted round-robin (WRR). For these queues, you can define the weighting according to the needs of your network. When QoS is not configured for data traffic, queue 2 is the default queue. LLQ+WRR - but no such option.

    2. J

       J2J2J2J

       2024-06-24

       Selected B2 upvotes

       On Cisco vEdge devices and Cisco IOS XE SD-WAN devices, each interface has eight queues, which are numbered 0 to 7. Queue 0 is reserved, and is used for both control traffic and low-latency queuing (LLQ) traffic. For LLQ, any class that is mapped to queue 0 must also be configured to use LLQ. Queues 1 to 7 are available for data traffic, and the default scheduling for these seven queues is weighted round-robin (WRR). For these queues, you can define the weighting according to the needs of your network. When QoS is not configured for data traffic, queue 2 is the default queue.

    3. A

       Abdulmw

       2024-10-28

       Selected B1 upvote

       The question is for the Queue schedule. On Cisco vEdge devices and Cisco IOS XE Catalyst SD-WAN devices, each interface has eight queues, which are numbered 0 to 7. Queue 0 is reserved, and is used for both control traffic and low-latency queuing (LLQ) traffic. For LLQ, any class that is mapped to queue 0 must also be configured to use LLQ. Queues 1 to 7 are available for data traffic, and the default scheduling for these seven queues is weighted round-robin (WRR). For these queues, you can define the weighting according to the needs of your network. When QoS is not configured for data traffic, queue 2 is the default queue. https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/qos/ios-xe-17/qos-book-xe/forwarding-qos.html

    4. [

       [Removed]

       2023-11-15

       4 upvotes

       WFQ uses weighted round robin scheduling and allows you to configure the weighting as a percentage of the bandwidth.. So LLQ+WFQ ? "B" looks ok to me.

19. Question 19 of 25

    

    Refer to the exhibit. Which method must an architect use to provide connectivity between the mail servers?

    • AISATAP
    • B6to4
    • C6rd
    • DIPv4 compatible

    Show answer

    Correct answer: B

    How others answered

    • B56%
    • A38%

    Only 56% agreed on this answer — treat it as contested rather than settled.

    Explanation

    B. 6to4 In this scenario, an architect should use the 6to4 method to provide connectivity between the mail servers. 6to4 is an IPv6 transition mechanism that allows IPv6 hosts to communicate with each other over an IPv4 network using a dual-stack router. The dual-stack routers automatically encapsulate IPv6 packets inside IPv4 packets for transmission over the IPv4 network and then decapsulate them when they reach the destination IPv6 network.

    Adapted from community discussion by SpicyMochi · 2023-04-28 · 5 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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    • cisco.com documentation
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    Candidate context

    Question 19 discussion

    These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

    1. S

       SpicyMochi

       2023-04-28

       Selected B5 upvotes

       B. 6to4 In this scenario, an architect should use the 6to4 method to provide connectivity between the mail servers. 6to4 is an IPv6 transition mechanism that allows IPv6 hosts to communicate with each other over an IPv4 network using a dual-stack router. The dual-stack routers automatically encapsulate IPv6 packets inside IPv4 packets for transmission over the IPv4 network and then decapsulate them when they reach the destination IPv6 network.

    2. L

       Lungful

       2023-08-21

       Selected B2 upvotes

       B is correct. 6to4 is for tunneling across a IPv4 network to connect two IPv6 networks while ISATAP is for connecting stand alone IPv4 devices with IPv6 devices and vice versa. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/interface/configuration/xe-16-12/ir-xe-16-12-book/ip6-isatap-xe.html https://www.admin-magazine.com/Archive/2013/13/IPv6-tunnel-technologies/(offset)/6

    3. N

       neiker45

       2024-01-11

       Selected B1 upvote

       https://community.cisco.com/t5/networking-knowledge-base/ipv6-isatap-configuration-example/ta-p/3152483 "he main difference between automatic 6to4 tunnels and ISATAP tunnels is that the automatic 6to4 is Inter-site tunnel that allows IPv6 traffic between different sites where as ISATAP as the name specifies is for Intra-site which can be used for transporting IPv6 packets within a site, but not between sites."

    4. S

       Seb82

       2024-09-13

       1 upvote

       if they would have put two PCs/clients, it would have been logic it's the same site, but they used mail servers. Logic says that the mail servers would be in two different sites, case in which 6to4 should be used.

20. Question 20 of 25

    An engineer is creating a design to enable IPv6 to run on an existing IPv4 IS-IS network. The IPv4 and IPv6 topologies will match exactly, and the engineer plans to use the same IS-IS router levels for each protocol per interface. Which IS-IS design is required?

    • Amulti topology without enabling transition feature
    • Bmulti topology with transition feature enabled
    • Csingle topology without enabling transition feature
    • Dsingle topology with transition feature enabled

    Show answer

    Correct answer: C

    How others answered

    • C78%

    Explanation

    I would say C as both IPV4 and IPV6 are sharing the exact same topology. No need of multipology nor transition mode: https://www.ws.afnog.org/afnog2011/are/ipv6-presentations/4-isis-for-ipv6.pdf

    Adapted from community discussion by Gabi512 · 2022-06-09 · 11 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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    Question 20 discussion

    These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

    1. G

       Gabi512

       2022-06-09

       Selected C11 upvotes

       I would say C as both IPV4 and IPV6 are sharing the exact same topology. No need of multipology nor transition mode: https://www.ws.afnog.org/afnog2011/are/ipv6-presentations/4-isis-for-ipv6.pdf

    2. I

       iLikeHamburgers

       2023-03-28

       2 upvotes

       The key thing here is that it states there is a currently deployed IPV4 network. Once you configure IPv6 on an interface that is currently running IPv4, you break the requirement that states "all interfaces on which IS-IS is configured must support the identical set of network address families." There is also a requirement that states "all routers in the IS-IS area (for Level 1 routing) or domain (for Level 2 routing) must support the identical set of network layer address families." I don't have the ability to lab this at the moment, however I would be curious to see if you had a network running single topology IPv4 only, and then started configuring IPv6 on the interfaces, would it break anything. I would question whether C is correct or not. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_isis/configuration/xe-3s/irs-xe-3s-book/ip6-route-mult-isis-xe.html#GUID-EA369F57-430A-4F30-B467-4529140CB0B6

    3. S

       SpicyMochi

       2023-10-28

       Selected C2 upvotes

       C. single topology without enabling transition feature In a single topology design, both IPv4 and IPv6 addresses can be carried within the same IS-IS domain without creating separate topologies. IS-IS, being a Layer 2 protocol, can natively support both IPv4 and IPv6. By utilizing a single topology design without any transition feature, the engineer can enable IPv6 on the existing IPv4 IS-IS network with the same router levels for each protocol per interface, while still maintaining a single, integrated topology.

    4. A

       andrewChan

       2023-04-30

       1 upvote

       yes it would break adjanency when address familty is different during transition, according to cisco doc: For single-topology IS-IS IPv6, routers must be configured to run the same set of address families. IS-IS performs consistency checks on hello packets and will reject hello packets that do not have the same set of configured address families. For example, a router running IS-IS for both IPv4 and IPv6 will not form an adjacency with a router running IS-IS for IPv4 or IPv6 only. In order to allow adjacency to be formed in mismatched address-families network, the adjacency-check command in IPv6 address family configuration mode must be disabled. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_isis/configuration/xe-3s/irs-xe-3s-book/ip6-route-isis-xe.html#GUID-04990BCF-8228-459E-AFAA-9FAF1E2136E9

21. Question 21 of 25

    Which consideration must be taken into account when using the DHCP relay feature in a Cisco SD-Access Architecture?

    • ADHCP-relay must be enabled on fabric edge nodes to provide the correct mapping of DHCP scope to the local anycast gateway.
    • BA DHCP server must be enabled on the border nodes to allow subnets to span multiple fabric edges.
    • CDHCP servers must support Cisco SD-Access extensions to correctly assign IPs to endpoints in an SD-Access fabric with anycast gateway.
    • DDHCP Option-82 must be enabled to map the circuit IP option to the access fabric node where the DHCP discover originated.

    Show answer

    Correct answer: D

    How others answered

    • D75%
    • A25%

    Explanation

    I think "A" is corret, Is true that OPTION 82 is used, however its a feature that is and should be automatically added by the FENs. Therefore the Relay-agent has to be the FEN Fabric Edge Node.

    Adapted from community discussion by kakito · 2022-05-03 · 3 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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    Question 21 discussion

    These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

    1. [

       [Removed]

       2022-03-14

       11 upvotes

       i think correct answer is d https://www.cisco.com/c/en/us/td/docs/solutions/CVD/Campus/cisco-sda-design-guide.html#FabricDHCPOverviewandDesign

    2. I

       iLikeHamburgers

       2023-12-29

       Selected D1 upvote

       Answer A is partially correct, because there is a need to have a the DHCP Discover packet relayed to the DHCP server, however the mapping of the client to the correct DHCP scope is not done with the anycast gateway, it is done within the DHCP Option82 sub options.This is needed because every edge device in the fabric has the same anycast gateway. There would be no way for the DHCP server to get the request back to the originating requestor with out the sub options from Option 82, specifically the source RLOC. Look under “Fabric DHCP Packet Flow” in the link below https://www.cisco.com/c/en/us/td/docs/solutions/CVD/Campus/cisco-sda-design-guide.html

    3. C

       CCNPWILL

       2022-06-30

       4 upvotes

       I read through the doc in regards to DHCP relay Option 82. I also believe D is the best choice here.

    4. K

       kakito

       2022-05-03

       3 upvotes

       I think "A" is corret, Is true that OPTION 82 is used, however its a feature that is and should be automatically added by the FENs. Therefore the Relay-agent has to be the FEN Fabric Edge Node.

22. Question 22 of 25

    How do endpoints inside an SD-Access network reach resources outside the fabric?

    • Aa VRF fusion router is used to map resources in one VN to another VN
    • BFabric borders use VRFs to map VNs to VRFs
    • CSD-Access transit links are used to transport encapsulated traffic from one fabric to another
    • DA fabric edge is used to de-encapsulate VXLAN traffic to normal IP traffic then transported over the outside network

    Show answer

    Correct answer: B

    How others answered

    • B58%
    • D33%

    Only 58% agreed on this answer — treat it as contested rather than settled.

    Explanation

    I think it's B. Not A; VN to another VN is not external to the fabric, so this is not what we need here. Could be B; your VN will be mapped to a VRF, and so providing access to networks outside the SDA. Not C; fabric to fabric; nope. Not D; fabric edge is device connecting clients, not providing external access (that's a border node's job).

    Adapted from community discussion by aai5548 · 2022-01-28 · 16 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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    Question 22 discussion

    These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

    1. A

       aai5548

       2022-01-28

       16 upvotes

       I think it's B. Not A; VN to another VN is not external to the fabric, so this is not what we need here. Could be B; your VN will be mapped to a VRF, and so providing access to networks outside the SDA. Not C; fabric to fabric; nope. Not D; fabric edge is device connecting clients, not providing external access (that's a border node's job).

    2. R

       Ranx01

       2022-01-24

       13 upvotes

       I think the answer is B - "Fabric border routers handle the ingress & egress traffic for the SD-Access fabric, they are responsible for translating the policy, VRF & SGT information between the SD-Access fabric and the external networks." Boson ExSim-Max for Cisco 350-401 ENCOR. Reference Cisco SD-Access Solutions Design Guide (CVD): SD-Access Solutions Components.

    3. M

       Mardouk

       2021-12-15

       4 upvotes

       it could be A, yes : https://www.cisco.com/c/en/us/td/docs/solutions/CVD/Campus/cisco-sda-design-guide.html - VRF-Aware Peer Design "The generic term fusion router comes from MPLS Layer 3 VPN. The basic concept is that the fusion router is aware of the prefixes available inside each VPN (VRF), generally through dynamic routing, and can therefore fuse these routes together"

    4. [

       [Removed]

       2023-11-16

       Selected B2 upvotes

       https://www.cisco.com/c/en/us/td/docs/solutions/CVD/Campus/cisco-sda-design-guide.html#Border_Node ● Network virtualization extension to the external world—The border node can extend network virtualization from inside the fabric to outside the fabric by using VRF-lite and VRF-aware routing protocols to preserve the segmentation.

23. Question 23 of 25

    Which component of Cisco SD-Access integrates with Cisco DNA Center to perform policy segmentation and enforcement through the use of security group access control lists and security group tags?

    • ACisco Application Policy Infrastructure Controller Enterprise Module
    • BCisco Network Data Platform
    • CCisco Identity Services Engine
    • DCisco TrustSec

    Show answer

    Correct answer: C

    How others answered

    • C100%

    Explanation

    Effectively, it's Cisco TrustSec - ISE is for identity context, authentication, posture validation, etc Cisco TrustSec - Security provided by Cisco TrustSec ® infrastructure (Security Group Tags [SGT], SGACLs) and Cisco segmentation capabilities (Cisco Locator/ID Separation Protocol [LISP], VXLAN, and Virtual Routing and Forwarding [VRF]). Identity context for users and devices, including authentication, posture validation, and device profiling, provided by the Cisco ISE. https://www.cisco.com/c/en/us/solutions/collateral/enterprise-networks/software-defined-access/nb-09-sda-faq-cte-en.html

    Adapted from community discussion by luisjuradoledesma · 2022-07-31 · 4 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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    Question 23 discussion

    These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

    1. L

       luisjuradoledesma

       2022-07-31

       4 upvotes

       Effectively, it's Cisco TrustSec - ISE is for identity context, authentication, posture validation, etc Cisco TrustSec - Security provided by Cisco TrustSec ® infrastructure (Security Group Tags [SGT], SGACLs) and Cisco segmentation capabilities (Cisco Locator/ID Separation Protocol [LISP], VXLAN, and Virtual Routing and Forwarding [VRF]). Identity context for users and devices, including authentication, posture validation, and device profiling, provided by the Cisco ISE. https://www.cisco.com/c/en/us/solutions/collateral/enterprise-networks/software-defined-access/nb-09-sda-faq-cte-en.html

    2. S

       SpicyMochi

       2024-10-28

       Selected C2 upvotes

       The correct answer is C. Cisco Identity Services Engine (ISE). Cisco ISE integrates with Cisco DNA Center to perform policy segmentation and enforcement in an SD-Access network. It uses security group access control lists (SGACLs) and security group tags (SGTs) to enforce policies based on user and device profiles. ISE enables the creation and management of these security policies, ensuring that proper access is granted based on user and device identity.

    3. C

       cerifyme85

       2024-10-19

       1 upvote

       SGT ==> DNAC + ISE While SGTs are administered by Cisco ISE through the tightly integrated REST APIs, Cisco DNA Center is used as the pane of glass to manage and create SGTs and define their policies. TrustSec--> Just a term Cisco TrustSec is an umbrella term for security improvements to Cisco network devices based on the capability to strongly identify users, hosts and network devices within a network. TrustSec provides topology independent and scalable access controls by uniquely classifying data traffic for a particular role. TrustSec ensures data confidentiality and integrity by establishing trust among authenticated peers and encrypting links with those peers. The key component of Cisco TrustSec is the Cisco Identity Services Engine. It is typical for the Cisco ISE to provision switches with TrustSec Identities and Security Group ACLs (SGACLs), though these may be configured manually.

    4. K

       Kamran202034

       2024-01-28

       Selected C2 upvotes

       C is correct. Policy management with identity services is enabled in an SD-Access network using ISE integrated with Cisco DNA Center for dynamic mapping of users and devices to scalable groups. https://www.cisco.com/c/en/us/td/docs/solutions/CVD/Campus/cisco-sda-design-guide.html#CiscoDNACenterSoftware

24. Question 24 of 25

    Which feature is required for graceful restart to recover from a processor failure?

    • ACisco Express Forwarding
    • BVirtual Switch System
    • CStateful Switchover
    • DBidirectional Forwarding Detection

    Show answer

    Correct answer: C

    How others answered

    • C91%

    Explanation

    I think it is A. Cisco Nonstop Forwarding does not maintain a continuously active control plane during switchover. Instead, the forwarding plane uses known routes while the routing protocol information is being restored after switchover. In Cisco networking devices, packet forwarding is provided by Cisco Express Forwarding. Cisco Express Forwarding maintains the FIB and uses the FIB information that was current at the time of the switchover to continue forwarding packets during a switchover. The ability to continue packet forwarding eliminates downtime during the switchover. Each protocol depends on Cisco Express Forwarding to continue forwarding packets during switchover, while the routing protocols rebuild the Routing Information Base (RIB). https://www.cisco.com/en/US/technologies/tk869/tk769/technologies_white_paper0900aecd801dc5e2.html

    Adapted from community discussion by aai5548 · 2022-01-28 · 2 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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    Question 24 discussion

    These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

    1. A

       aai5548

       2022-01-28

       2 upvotes

       I think it is A. Cisco Nonstop Forwarding does not maintain a continuously active control plane during switchover. Instead, the forwarding plane uses known routes while the routing protocol information is being restored after switchover. In Cisco networking devices, packet forwarding is provided by Cisco Express Forwarding. Cisco Express Forwarding maintains the FIB and uses the FIB information that was current at the time of the switchover to continue forwarding packets during a switchover. The ability to continue packet forwarding eliminates downtime during the switchover. Each protocol depends on Cisco Express Forwarding to continue forwarding packets during switchover, while the routing protocols rebuild the Routing Information Base (RIB). https://www.cisco.com/en/US/technologies/tk869/tk769/technologies_white_paper0900aecd801dc5e2.html

    2. S

       SpicyMochi

       2024-04-28

       Selected C2 upvotes

       The correct answer is C. Stateful Switchover (SSO). Stateful Switchover (SSO) is a feature that allows graceful restart to recover from a processor failure in a network device. SSO enables a device to maintain its forwarding capability while recovering from a processor failure, minimizing the impact on network traffic. This is accomplished by synchronizing the control plane information between the active and standby processors in the device. In the event of a processor failure, the standby processor takes over the control plane functions without causing any disruption to the forwarding plane.

    3. K

       kudasay

       2021-12-06

       4 upvotes

       C is correct! - GR is the only feature that interacts with peer network devices, all other features (SSO/NSF/NSR) are internal to the router and therefore don’t require standards. Source: https://archive.nanog.org/meetings/nanog42/presentations/Weissner_SSO.pdf

    4. I

       iLikeHamburgers

       2023-12-29

       Selected C2 upvotes

       This is a tricky question. In the OCG pg 168 it states "Graceful Restart (GR), also known as Non-Stop Forwarding..." So Graceful Restart and Non-Stop Forwarding are one in the same. Now looking at the this site https://www.cisco.com/en/US/docs/ios/12_2t/12_2t15/feature/guide/ftbgpnsf.html it states "SSO is a prerequisite of NSF". So going by what the OCG said above, and after reading the link above, what we can conclude is SSO is a prerequisite of Graceful Restart.

25. Question 25 of 25

    An existing network solution is using BFD in echo mode. Several network devices are experiencing high CPU utilization, which an engineer has determined is related to the BFD feature. Which solution should the engineer leverage to reduce the CPU load?

    • AImplement slow timers between peers with low CPU resources.
    • BImplement BFD asynchronous mode between peers with low CPU resources.
    • CEnable BFD multi-hop on the devices with low CPU resources.
    • DUtilize carrier delay on all routers in the network.

    Show answer

    Correct answer: A

    How others answered

    • A80%
    • B20%

    Explanation

    SLow timers is correct. https://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/5_x/nx-os/interfaces/configuration/guide/if_cli/if_bfd.html Unde BFD echo function " BFD can use the slow timer to slow down the asycnhronous session when the echo function is enabled and reduce the number of BFD control packets that are sent between two BFD neighbors. "

    Adapted from community discussion by zlimvos · 2022-06-09 · 4 community upvotes. Third-party contribution; reviewed by our quality filter, not independently verified.

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    Question 25 discussion

    These are quality-filtered excerpts from third-party community discussion. They can be useful reasoning signals, but they are not official answers and have not been independently verified by 300-420 or CertExamHQ.

    1. S

       Sickcnt

       2022-10-19

       Selected A4 upvotes

       "...Finally, “BFD can use the slow timer to slow down the asycnhronous session when the echo function is enabled and reduce the number of BFD control packets that are sent between two BFD neighbors.” That is, BFD echo can go fast without interrupting the CPU, and since that will detect an outage, you don’t need BFD control packets running as often, since the control packets aren’t being used for the rapid detection function. That in turn lightens the CPU load and allows more use of BFD. Clever!" Source: https://netcraftsmen.com/clarifying-bfd-and-bfd-echo/

    2. Z

       zlimvos

       2022-06-09

       Selected A4 upvotes

       SLow timers is correct. https://www.cisco.com/c/en/us/td/docs/switches/datacenter/sw/5_x/nx-os/interfaces/configuration/guide/if_cli/if_bfd.html Unde BFD echo function " BFD can use the slow timer to slow down the asycnhronous session when the echo function is enabled and reduce the number of BFD control packets that are sent between two BFD neighbors. "

    3. C

       Clauster

       2023-08-03

       1 upvote

       The BFD feature that uses less CPU usage is BFD asynchronous mode. In asynchronous mode, BFD sessions are initiated independently by each router in a BFD adjacency. This means that each router sends BFD packets periodically, regardless of whether or not it has received any BFD packets from its neighbor. In contrast, BFD synchronous mode requires both routers in a BFD adjacency to agree on the interval at which BFD packets are sent. This means that both routers must be synchronized, which can require more CPU resources. Additionally, BFD asynchronous mode does not require BFD packets to be acknowledged. This means that BFD packets can be sent and received more quickly, which can also reduce CPU usage.

    4. E

       Emily23

       2023-06-13

       3 upvotes

       When echo mode, the BFD packet loops back through the interface of the peer without processing. What you are saying is not logic. If you invoke control plane, than it's deffinetly using CPU.

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