Q&A
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. You can even customize the CD exam to include, or not include, the topics that are only on the CCIP QoS.
Traffic Policing and Traffic Shaping Concepts
| 1. | Explain the points during the process of a single router receiving and forwarding traffic at which shaping and policing can be enabled on a router.
| | 2. | Compare and contrast the actions that shaping and policing take when a packet exceeds a traffic contract.
| | 3. | Compare and contrast the effects that shaping and policing have on bandwidth, delay, jitter, and loss.
| | 4. | Describe the typical locations to enable shaping and policing in an internetwork.
| | 5. | Describe the reasons behind egress blocking in a Frame Relay network with a T1 access link at the main site, 128-kbps access links at each of 20 remote sites, with 64-kbps CIR VCs from the main site to each remote site.
| | 6. | If a router has CB Shaping configured, with a shaping rate of 256 kbps, and a Bc of 16,000 bits, what Tc value does the shaping tool use?
| | 7. | If a router has CB Shaping configured, with a shaping rate of 512 kbps, and a Be of 16,000 bits, what Tc value does the shaping tool use?
| | 8. | Define the terms Tc, Bc, Be, and CIR.
| | 9. | Describe the concept of traffic-shaping adaption.
| | 10. | Describe the difference between interface output queues and shaping queues, and explain where the queues could exist on a router with 1 physical interface and 20 subinterfaces.
| | 11. | How many token buckets are used by the CB Shaping internal processes with Be = 0? How big is the bucket(s)?
| | 12. | How many token buckets are used by the CB Shaping internal processes with Be = 8000? How big is the bucket(s)?
| | 13. | How many token buckets are used by the CB Policing internal processes with Be = 0? How big is the bucket(s)?
| | 14. | How many token buckets are used by CB Policing internal processes, configured for single-rate policing, with Be = 8000? How big is the bucket(s)?
| | 15. | How many token buckets are used by CB Policing internal processes, configured for dual-rate policing, with Be = 8000? How big is the bucket(s)?
| | 16. | Imagine a CB Shaping configuration with a rate of 128000, Bc = 8000, and Be = 16000. What is the Tc value, and how many tokens are refilled into the first bucket during each Tc?
| | 17. | Imagine a CB Shaping configuration with a rate of 128000, Bc = 8000, and Be = 16000. At the beginning of the next time interval, the token bucket is full. If the physical clock rate of the interface on which shaping is enabled is 256 kbps, describe how much traffic that will be sent in this next Tc, and why.
| | 18. | If a policer is called a "two color" policer, what does that mean?
| | 19. | If a policer is called a "three color" policer, what does that mean?
| | 20. | With CB Policing, how are tokens refilled into the bucket associated with the CIR policing rate?
| | 21. | With a dual-rate policer, how are tokens refilled into the token bucket associated with PIR?
| | 22. | With a single-rate policer, with Be > 0, how are tokens refilled into the excess token bucket?
| | 23. | With a single-rate policer, with Be = 0, what must be true for the policer to decide that a packet exceeds the traffic contract?
| | 24. | With a single-rate policer, with Be > 0, what must be true for the policer to decide that a packet exceeds the traffic contract?
| | 25. | With a single-rate policer, with Be > 0 what must be true for the policer to decide that a packet violates the traffic contract?
| | 26. | With a single-rate policer, regardless of Be setting, what must be true for the policer to decide that a packet conforms to the traffic contract?
| | 27. | For policing configurations that use two buckets, a packet is classified as conforming, exceeding, or violating the traffic contract. When processing a new packet, in which of these three cases does the policer then also remove or spend the tokens?
| | 28. | Comparing the logic used for a single-rate and dual-rate policer, when both use two token buckets, their logic differs slightly in terms of how the tokens are removed from the buckets when policing a packet. Explain that difference.
| | 29. | Comparing the logic used for a single-rate and dual-rate policer, when both use two token buckets, their logic differs slightly in terms of how the tokens are added to the buckets before policing a newly-arrived packet. Explain that difference.
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Class Based Shaping Configuration
| 30. | Along with the class-map, policy-map, and service-policy commands, CB shaping requires one specific command that actually sets values used for the shaping function. List the command, with the correct syntax, that sets a shaped rate of 128 kbps, a Bc of 8000, and a Be of 8000, when using CB shaping. Do not assume any defaults; explicitly set the values in the command.
| | 31. | Explain the context inside the configuration mode under which the service-policy command can be used to enable LLQ on a CB shaping queue. ("Context" means what part of configuration modefor instance, global-configuration mode, interface configuration mode, and so on.)
| | 32. | CB shaping has been configured under subinterface s0/0.1. What show command lists statistics for CB shaping behavior just for that subinterface?
| | 33. | Which of the traffic-shaping tools can be enabled on each VC on a Frame Relay multipoint subinterface?
| | 34. | At what rate would CB Shaping actually shape traffic when using the command shape peak 64000 8000 16000?
| | 35. | Assume that two class maps have already been defined, called C1 and C2. You decide to add a policy map, and enable it on interface serial 0/1, so that the policy map has both classes C1 and C2 in it. For class C1, you do not use any shaping, but for class C2, you will shape with a rate of 128 kbps. Create the rest of the syntactically-correct configuration commands to meet this requirement.
| | 36. | Assume the same general requirements as the previous question. Create the configuration, defining the shaping rate as a percentage, assuming the interface already has a bandwidth 256 command under it.
| | 37. | Assume the same general requirements as the previous question, except now you want to tune the Tc down to 10ms, and not have any excess burst capability. Create the configuration.
| | 38. | Assume the same general requirements as the previous question, except now you want to keep the default Bc, but make Be equal to twice Bc. Create the configuration.
| | 39. | Assume the same general requirements as the previous question, except now you want to adapt the shaping rate to 50 percent of the originally configured rate upon the receipt of Frame Relay BECNs. Create the configuration.
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Class Based Policing Configuration
| 40. | Assume that two class maps have already been defined, called C1 and C2. You decide to add a policy-map, and enable it on interface serial 0/1, so that the policy-map has both classes C1 and C2 in it. For class C1, will configure policing at a rate of 128 kbps, and for class C2, you will police at a rate of 256 kbps. You want to transmit packets that conform to the contract, and re-mark to DSCP AF13 for those that exceed the contract. Create the rest of the syntactically-correct configuration commands to meet this requirement.
| | 41. | Assume the same general requirements as the previous question, but in this case, you want to create a two-bucket/three-color policer, and drop packets that violate the traffic contract. Create the configuration commands.
| | 42. | Assume that two class maps have already been defined, called C1 and C2. You decide to add a policy map, and enable it on interface serial 0/1, so that the policy map has both classes C1 and C2 in it. For class C1, will configure policing at a rate of 128 kbps, and for class C2, you will police at a rate of 256 kbps. You can configure any actions you like for the three categories. However, you need to change the Bc setting such that the first token bucket's size is equal to 1 second's worth of data. Create the configuration commands.
| | 43. | Assume the same general requirements as the previous question, but now you decide to create a dual-rate policer for class C2, with the PIR set at double the CIR of 256 kbps. Create the configuration commands. Assuming you didn't configure Be, what would CB Policing calculate for the Be setting?
| | 44. | Assume the same general requirements as the previous question, but now configure the police commands assuming that interface serial 0/1 has a bandwidth 512 command configured, and you have to use the percent option in both police commands.
| | 45. | CB Policing has been configured under subinterface s0/0.1. What show command would list statistics for CB Policing behavior just for that subinterface?
| | 46. | List the command, with the correct syntax, that sets a Policed rate of 512 kbps, a Bc of 1 second's worth of traffic, and a Be of an additional .5 seconds worth of traffic, when using CB Policer. Do not assume any defaults; explicitly set the values in the command. You can choose any other settings needed for the command.
| | 47. | Explain the concept behind re-marking policed packets versus discarding the packets.
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