As mentioned in the Introduction, you have two choices for review questions. The questions that follow next give you a more difficult challenge than the exam itself by using an open-ended question format. By reviewing now with this more difficult question format, you can exercise your memory better, and prove your conceptual and factual knowledge of this chapter. You can find the answers to these questions in Appendix A.
The second option for practice questions is to use the CD included with this book. It includes a testing engine and more than 200 multiple-choice questions. You should use this CD nearer to the end of your preparation, for practice with the actual exam format.
| 1. | Describe the benefits of having a single FIFO output queue.
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| 2. | Explain the effects of changing a single FIFO queue's length to twice its original value. Include comments about how the change affects bandwidth, delay, jitter, and loss.
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| 3. | Explain the purpose of a TX Ring and TX Queue in a Cisco router.
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| 4. | Explain how a long TX Ring might affect the behavior of a queuing tool.
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| 5. | Describe the command output that identifies the length of the TX Ring or TX Queue, and whether the length was automatically lowered by IOS.
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| 6. | Explain under what circumstances the TX Ring, interface output queues, and subinterface output queues both fill and drain, and to where they drain.
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| 7. | Assume a queuing tool has been enabled on interface S0/0. Describe the circumstances under which the queuing tool would actually be used.
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| 8. | Explain the circumstances under which it would be useful to enable a queuing tool on a subinterface.
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| 12. | WFQ classifies packets based on their flow. Other than a typical flow from an end user device, identify the other two types of flows recognized by WFQ.
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| 13. | Characterize the effect the WFQ scheduler has on different types of flows.
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| 14. | Describe the WFQ scheduler process. Include at least the concept behind any formulas, if not the specific formula.
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| 15. | You previously disabled WFQ on interface S0/0. List the minimum number of commands required to enable WFQ on S0/0.
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| 16. | What commands list statistical information about the performance of WFQ?
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| 17. | Define what comprises a flow in relation to WFQ.
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| 18. | You just bought and installed a new 3600 series router. Before adding any configuration to the router, you go ahead and plug in the new T1 Frame Relay access link to interface S0/0. List the minimum number of commands required to enable WFQ on S0/0.
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| 19. | Describe the CBWFQ scheduler process, both inside a single queue and among all queues.
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| 20. | Describe how LLQ allows for low latency while still giving good service to other queues.
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| 21. | Compare and contrast the CBWFQ command that configures the guaranteed bandwidth for a class with the command that enables LLQ for a class.
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| 22. | Describe the CBWFQ classification options. List at least five fields that can be matched without using an ACL.
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| 23. | Name the two CBWFQ global configuration commands that define classification options, and then the per-hop behaviors, respectively. Also list the command that enables CBWFQ on an interface.
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| 24. | Examine the following configuration (Example 5-10). Which of the five policy maps would certainly enable LLQ for voice payload traffic, based only of the information in the configuration?
Example 5-10. Exhibit for CBWFQ Configuration Questions
!
class-map match-all class1
match ip rtp 16384 16383
class-map match-all class2
match access-group 101
class-map match-all class3
match ip rtp 16384 32767
class-map match-all class4
match ip dscp ef
class-map match-all class5
match access-group 102
!
policy-map pmap1
class class1
priority 60
policy-map pmap2
class class2
priority 60
policy-map pmap3
class class3
priority 60
policy-map pmap4
class class4
priority 60
policy-map pmap5
class class5
priority 60
!
interface Serial0/0
service-policy output ?????
!
access-list 101 permit udp any gt 16383 any gt 16383
access-list 102 permit udp any range 16383 32767 any range 16383 32767
!
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| 25. | Using the same exhibit as in the preceding example, describe what must also be true for pmap4 to queue voice payload traffic successfully, and only voice payload traffic, in a low-latency queue.
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| 26. | Which of the following queuing tools can always service a particular queue first, even when other queues have packets waiting? First-In, First-Out Queuing (FIFO); Priority Queuing (PQ); Custom Queuing (CQ); Weighted Fair Queuing (WFQ); Class-Based WFQ (CBWFQ); Low Latency Queuing (LLQ).
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| 27. | Which of the following queuing tools allows for a percentage bandwidth to be assigned to each queue? First-In, First-Out Queuing (FIFO); Priority Queuing (PQ); Custom Queuing (CQ); Weighted Fair Queuing (WFQ); Class-Based WFQ (CBWFQ); Low Latency Queuing (LLQ).
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| 28. | Which queuing tools could be configured to provide the lowest possible latency for voice traffic? Of these, which does Cisco recommend as the best option for voice queuing today?
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| 29. | Which of the following queuing tools can use flow-based classification? First-In, First-Out Queuing (FIFO); Priority Queuing (PQ); Custom Queuing (CQ); Weighted Fair Queuing (WFQ); Class-Based WFQ (CBWFQ); Low Latency Queuing (LLQ).
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| 30. | Which of the following queuing tools uses the Modular QoS CLI? First-In, First-Out Queuing (FIFO); Priority Queuing (PQ); Custom Queuing (CQ); Weighted Fair Queuing (WFQ); Class-Based WFQ (CBWFQ); Low Latency Queuing (LLQ).
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| 31. | Which of the following queuing tools allows for a value to be configured, which then results in a specific number of bytes being taken from each queue during a round-robin pass through the queues? First-In, First-Out Queuing (FIFO); Priority Queuing (PQ); Custom Queuing (CQ); Weighted Fair Queuing (WFQ); Class-Based WFQ (CBWFQ); Low Latency Queuing (LLQ).
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| 32. | What model of Cisco router supports WFQ inside CBWFQ classes other than class-default?
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| 33. | Give an explanation for the following comment: "WFQ can become too fair when it has a large number of active flows"?
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| 34. | Imagine the following commands in Example 5-11 were typed in configuration mode, in order. Also assume that class maps class1, class2, and class3 have already been correctly defined. How much bandwidth will class class3 be assigned on interface S0/0?
Example 5-11. Exhibit for CBWFQ Configuration Questions
!
policy-map pmap1
class class1
priority 60
class class2
bandwidth percent 30
class class3
bandwidth percent 45
!
policy-map pmap2
class class1
priority percent 20
class class2
bandwidth remaining percent 30
class class3
bandwidth remaining percent 70
!
policy-map pmap3
class class1
priority percent 20
class class2
bandwidth 30
class class3
bandwidth percent 30
!
interface Serial0/0
service-policy output pmap1
!
interface Serial0/1
bandwidth 512
service-policy output pmap2
!
interface Serial0/2
bandwidth 256
service-policy output pmap3
!
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| 35. | In the same example, what could be done so that the service-policy output pmap1 command would be accepted under interface serial0/0without changing the policy map? Assuming that was done, what actual bandwidth could be assigned to class3?
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| 36. | In the same example, how much bandwidth would class1 be assigned on interface serial 0/1?
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| 37. | In the same example, how much bandwidth would class2 and class3 be assigned on interface serial 0/1?
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| 38. | In the same example, how much bandwidth would class2 and class3 be assigned on interface serial 0/2?
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