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WAN Availability and QoS

Chapter Description

In this sample chapter from CCNP Enterprise Design ENSLD 300-420 Official Cert Guide: Designing Cisco Enterprise Networks, you will review WAN methodologies and WAN availability with deployment models using MPLS, hybrid, and Internet designs. It also covers backup connectivity, failover designs, QoS strategies, and designing end-to-end QoS policies.


The answers to these questions appear in Appendix A. For more practice with exam format questions, use the exam engine on the companion website.

1. Which of the following is based on the availability of technology as well as the projected traffic patterns, technology performance, constraints, and reliability?

  1. Designing the topology

  2. Assessing the existing network

  3. Identifying the network requirements

  4. Characterize the existing network

2. Which design principle involves redundancy through hardware, software, and connectivity?

  1. Performance

  2. Security

  3. Scalability

  4. High availability

3. Which application requires round-trip times of less than 400 ms with low delay and jitter?

  1. Data file transfer

  2. Real-time voice

  3. Real-time video

  4. Interactive data

4. Which of the following is a measure of a given application’s availability to its users?

  1. Response time

  2. Throughput

  3. Reliability

  4. Performance

5. Which of the following defines the upper limit of frames that can be transmitted without a return acknowledgment?

  1. Throughput

  2. Link efficiency

  3. Window size

  4. Low-latency queuing

6. Which of the following is the availability target range for branch WAN high availability?

  1. 99.9900%

  2. 99.9000%

  3. 99.0000%

  4. 99.9999%

7. Which WAN deployment model provides for the best SLA guarantees?

  1. MPLS WAN with dual routers

  2. Hybrid WAN with MPLS and Internet routers

  3. Internet WAN with dual routers

  4. Internet WAN with a single router

8. Which Internet connectivity option provides for the highest level of resiliency?

  1. Single-router single-homed

  2. Single-router dual-homed

  3. Dual-router dual-homed

  4. GRE tunnels

9. When designing Internet for remote sites, which option provides control for security services such as URL filtering, firewalling, and intrusion prevention?

  1. Centralized Internet

  2. Direct Internet

  3. Direct Internet with split tunnel

  4. IPsec with split tunnel

10. Which design considerations are most important for Internet high availability design? (Choose two.)

  1. Using a public BGP AS number for eBGP connections to ISPs

  2. Using provider-independent IP address space for advertisements to ISPs

  3. Using BGP communities

  4. Using extended ACLs

11. Which WAN backup option provides for redundancy and additional bandwidth?

  1. Backup link

  2. IPsec tunnel

  3. GRE tunnel

  4. NAT-T

12. Which failover option can be used to back up the primary MPLS WAN connection?

  1. BGP

  2. GLBP

  3. HSRP

  4. IPsec tunnel

13. Which of the following is not a model for providing QoS?

  1. Best-effort

  2. DiffServ

  3. IntServ

  4. NSF

14. In QoS markings, what DSCP value is used for VoIP traffic?

  1. AF4

  2. CS2

  3. EF

  4. CS5

15. Which QoS method uses a strict priority queue in addition to modular traffic classes?

  1. CBWFQ

  2. Policing

  3. WFQ

  4. LLQ

16. Within RSVP, what function is used to determine whether the requested flows can be accepted?

  1. Admission control

  2. Classification

  3. Policing

  4. Queuing and scheduling

17. Which of the following slows down the rate at which packets are sent out an interface (egress) by matching certain criteria?

  1. Policing

  2. CAR

  3. Shaping

  4. NBAR

18. What is the buffering process that routers and switches use when they receive traffic faster than it can be transmitted?

  1. Policing

  2. Queuing

  3. NBAR

  4. Shaping

19. What do service providers use to define their service offerings at different levels?

  1. SWAN

  2. WAN tiers

  3. WWAN

  4. SLA

20. Which of the following has mechanisms to handle traffic overflow using a queuing algorithm?

  1. Link-efficiency mechanisms

  2. Classification

  3. Congestion management

  4. Traffic shaping and policing

21. Which QoS category identifies and marks flows?

  1. Congestion management

  2. Traffic shaping and policing

  3. Link-efficiency mechanisms

  4. Classification and marking

22. Which design principle balances the amount of security and technologies with the budget?

  1. Performance

  2. Standards and regulations

  3. Cost

  4. Security

23. Which application type has requirements for low throughput and response time within a second?

  1. Real-time video

  2. Interactive data

  3. Real-time voice

  4. Interactive video

24. Which of the following WAN connectivity options has bandwidth capabilities of 1 Gbps to 10 Gbps?

  1. 802.11a

  2. LTE

  3. LTE Advance Pro

  4. LTE Advanced

25. How many days of downtime per year occur with 99.00000% availability?

  1. 8.76 days

  2. 5.2 days

  3. 3.65 days

  4. 1.2 days

26. With dual-router and dual-path availability models, how much downtime is expected per year?

  1. 4 to 9 hours per year

  2. 26 hours per year

  3. 5 hours per year

  4. 5 minutes per year

27. Which deployment model for WAN connectivity has a single router or dual routers and uses both MPLS and an Internet VPN?

  1. Hybrid WAN

  2. Internet WAN



28. When designing the Internet with high availability, which of the following is a design consideration ?

  1. Use public address space for internal addressing

  2. Use private address space for route advertising to the ISPs

  3. Block all Internet routes

  4. Use HSRP/GLBP or an IGP internally

29. Which of the following is an important design consideration when using IPsec over GRE tunnels?

  1. QoS classification

  2. MTU size

  3. Header type

  4. Payload length

30. When using DSCP to classify traffic, which of the following is prioritized the most?

  1. Signaling

  2. Transactional data

  3. Real-time interaction

  4. VoIP

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