"Do I Know This Already?" Quiz

The purpose of the "Do I Know This Already?" quiz is to help you decide if you really need to read the entire chapter. If you already intend to read the entire chapter, you do not necessarily need to answer these questions now.

The 12-question quiz, derived from the major sections in "Foundation Topics" portion of the chapter, helps you determine how to spend your limited study time.

Table 5-1 outlines the major topics discussed in this chapter and the "Do I Know This Already?" quiz questions that correspond to those topics.

Table 5-1. "Do I Know This Already?" Foundation Topics Section-to-Question Mapping

Foundation Topics Section Covering These Questions	Questions	Score
Cisco Router Queuing Concepts	13
Scheduling Concepts: FIFO, PQ, CQ, and MDRR	46
Concepts and Configuration: WFQ, CBWFQ, and LLQ	712
Total Score

You can find the answers to the "Do I Know This Already?" quiz in Appendix A, "Answers to the 'Do I Know This Already?' Quizzes and Q&A Sections." The suggested choices for your next step are as follows:

• 10 or less overall score Read the entire chapter. This includes the "Foundation Topics," the "Foundation Summary," and the "Q&A" sections.
  
  
• 11 or 12 overall score If you want more review on these topics, skip to the "Foundation Summary" section and then go to the "Q&A" section. Otherwise, move to the next chapter.
  
  

Cisco Router Queuing Concepts Questions

1.	What is the main benefit of the hardware queue on a Cisco router interface? Prioritizes latency-sensitive packets so that they are always scheduled next Reserves a minimum amount of bandwidth for particular classes of traffic Provides a queue so that as soon as the interface is available to send another packet, the packet can be sent, without requiring an interrupt to the router CPU Allows configuration of a percentage of the remaining link bandwidth, after allocating bandwidth to the LLQ and the class-default queue
2.	A set of queues associated with a physical interface, for the purpose of prioritizing packets exiting the interface, are called which of the following? Hardware queues Software queues Shaping queues TX-queues
3.	Which of the following commands could change the length of a hardware queue? hardware queue-length 10 tx-queue length 10 hardware 10 tx-ring-limit 10

Scheduling Concepts: FIFO, PQ, CQ, and MDRR Questions

4.	What is the main benefit of having FIFO queuing enabled on a Cisco router interface? Prioritizes latency-sensitive packets so that they are always scheduled next Reserves a minimum amount of bandwidth for particular classes of traffic Provides a place to hold packets in RAM until space becomes available in the hardware queue for the interface. Provides a queue so that as soon as the interface is available to send another packet, the packet can be sent, without requiring an interrupt to the router CPU Allows configuration of a percentage of the remaining link bandwidth, after allocating bandwidth to the LLQ and the class-default queue
5.	What are the main benefits of CQ being enabled on a Cisco router interface? Prioritizes latency-sensitive packets so that they are always scheduled next Reserves a minimum amount of bandwidth for particular classes of traffic Provides a place to hold packets in RAM until space becomes available in the hardware queue for the interface. Provides a queue so that as soon as the interface is available to send another packet, the packet can be sent, without requiring an interrupt to the router CPU Allows configuration of a percentage of the remaining link bandwidth, after allocating bandwidth to the LLQ and the class-default queue
6.	What is the main benefit of enabling PQ on a Cisco router interface? Prioritizes latency-sensitive packets so that they are always scheduled next Reserves a minimum amount of bandwidth for particular classes of traffic Provides a place to hold packets in RAM until the interface becomes available for sending the packet Provides a queue so that as soon as the interface is available to send another packet, the packet can be sent, without requiring an interrupt to the router CPU Allows configuration of a percentage of the remaining link bandwidth, after allocating bandwidth to the LLQ and the class-default queue

Concepts and Configuration: WFQ, CBWFQ, and LLQ Questions

7.	Which of the following are reasons why WFQ might discard a packet instead of putting it into the correct queue? The hold-queue limit for all combined WFQ queues has been exceeded. The queue length for the flow has passed the WRED minimum drop threshold. The WFQ queue length for the queue where the newly-arrived packet should be placed has exceeded the CDT ECN feedback has been signaled, requesting that the TCP sender slow down
8.	Which of the following settings cannot be configured for WFQ on the fair-queue interface subcommand? CDT Number of queues Number of RSVP-reserved queues Hold Queue limit WRED thresholds
9.	Examine the following configuration snippet. If a new class, called class3, was added to the policy-map, which of the following commands could be used to reserve 25 kbps of bandwidth for the class? policy-map fred class class1 priority 20 class class2 bandwidth 30 ! interface serial 0/0 bandwidth 100 service-policy output fred priority 25 bandwidth 25 bandwidth percent 25 bandwidth remaining-percent 25
10.	Examine the following configuration snippet. How much bandwidth does IOS assign to class2? policy-map fred class class1 priority percent 20 class class2 bandwidth remaining percent 20 interface serial 0/0 bandwidth 100 service-policy output fred 10 kbps 11 kbps 20 kbps 21 kbps Not enough information to tell
11.	What is the largest number of classes inside a single policy map that can be configured as an LLQ? 1 2 3 more than 3
12.	To prevent non-LLQ queues from being starved, LLQ can police the low-latency queue. Looking at the configuration snippet below, what must be changed or added to cause this policy-map to police traffic in class1? policy-map fred class class1 priority 20 class class2 bandwidth remaining percent 20 interface serial 0/0 bandwidth 100 service-policy output fred Change the priority 20 command to priority 20 500, setting the policing burst size Add the police 20000 command under class1 Nothing the priority command implies that policing will also be performed Add the LLQ-police global configuration command