Chapter 19. Configuring Multicast

This chapter covers the following topics:

  • The Central Multicast Problem—Describes the key issue with multicasting—identifying sources.

  • Routing Multicast Traffic—Describes multicast routing protocols.

  • Enabling PIM Sparse-Dense Mode—Describes the commands necessary to implement multicasting.

When configuring multicast routing, the trick is not remembering a large set of commands, but understanding how those simple commands and your environment are supported by the router. The first section of this chapter deals with finding the multicast server. The second section describes how multicast routing and routing protocols work, and the third section covers the required commands to create an IP multicast network.

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

The 14-question quiz, derived from the major sections in the "Foundation Topics" portion of the chapter, helps you determine how to spend your limited study time.

Table 19-1 outlines the major topics discussed in this chapter and the "Do I Know This Already?"quiz questions that correspond to those topics.

Table 19-1. "Do I Know This Already?" Foundation Topics Section-to-Question Mapping
Foundation Topics SectionQuestions Covered in This SectionScore
The Central Multicast Problem1 
Routing Multicast Traffic2–8 
Enabling PIM Sparse-Dense Mode9–14 
Total Score  

Caution

The goal of self-assessment is to gauge your mastery of the topics in this chapter. If you do not know the answer to a question or are only partially sure of the answer, you should mark this question wrong for purposes of the self-assessment. Giving yourself credit for an answer you correctly guess skews your self-assessment results and might provide you with a false sense of security.


1.What common engineering problem must be solved by all multicast implementations?
  1. Identifying multicast servers

  2. Preventing multicast storms

  3. Preventing multicast loops

  4. Multicast TTL

2.Which of the following multicast routing protocols is fully supported on Cisco routers?
  1. Center-Based Trees

  2. Core-Based Trees

  3. DVMRP

  4. Multicast OSPF

  5. PIM

3.If a multicast group has recipients on every subnet, which of the PIM modes should be used?
  1. Dense mode

  2. Sparse mode

  3. Sparse-compress mode

  4. Flood mode

4.Which type of tree structure is built for sparse-mode multicast routing?
  1. Spanning tree

  2. Sparse tree

  3. Shared tree

  4. Simple tree

5.What router maintains the RP-to-group correlation for Auto-RP in PIMv1?
  1. RP agent

  2. PIM root

  3. Mapping agent

  4. RP discovery server

6.Rendezvous points are configured with an access list. What is the purpose of this list?
  1. Restricting users that use the RP

  2. Restricting routers that use the RP

  3. Restricting source addresses that use the RP

  4. Limiting multicast IP addresses that use the RP

7.What router advertises candidate RP routers in PIMv2?
  1. Auto-RP

  2. Mapping agent

  3. Bootstrap router

  4. PIM root

8.TTL is used by multicast for what purpose?
  1. Preventing loops

  2. Limiting scope

  3. Determining path

  4. Determining hops

9.Which command is used to enable multicast routing on an IOS device?
  1. (config)#ip multicast-routing

  2. (config-if)#multicast address {ip-address}

  3. (config-if)#ip pim {dense-mode | sparse-dense-mode | sparse-mode}

  4. (config)#ip pim send-rp-announce {interface type} {scope ttl} {group-list acl}

  5. (config)#ip pim send-rp-discovery {interface type} {scope ttl}

10.Which command enables a multicast routing protocol on an IOS device?
  1. (config)#ip multicast routing

  2. (config-if)#multicast address {IP-address}

  3. (config-if)#ip pim {dense-mode | sparse-dense-mode | sparse-mode}

  4. (config)#ip pim send-rp-announce {interface type} scope {ttl} group-list {acl}

  5. (config)#ip pim send-rp-discovery {interface type} scope {ttl}

11.Which command causes an IOS device to volunteer itself as an RP?
  1. (config)#ip multicast routing

  2. (config-if)#multicast address {IP-address}

  3. (config-if)#ip pim {dense-mode | sparse-dense-mode | sparse-mode}

  4. (config)#ip pim send-rp-announce {interface type} {scope ttl} {group-list acl}

  5. (config)#ip pim send-rp-discovery {interface type} scope {ttl}

12.Which command displays the multicast IP routing table?
  1. show ip mroute

  2. show ip pim interface

  3. show ip pim neighbors

  4. show ip pim rp

  5. show ip rpf

13.Which command displays information about rendezvous points?
  1. show ip mroute

  2. show ip pim interface

  3. show ip pim neighbors

  4. show ip pim rp

  5. show ip rpf

14.Which command utilizes the unicast IP routing table to calculate the interface on which traffic from a source should arrive?
  1. show ip mroute

  2. show ip pim interface

  3. show ip pim neighbors

  4. show ip pim rp

  5. show ip rpf

The answers to the "Do I Know This Already?" quiz are found in Appendix A, "Answers to Chapter '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," "Foundation Summary," and "Q&A" sections.

  • 11 or 12 overall score—Begin with the "Foundation Summary" section and then go to the "Q&A" section at the end of the chapter. If you have trouble with these exercises, read the appropriate sections in "Foundation Topics."

  • 13 or 14 overall score—If you want more review on these topics, skip to the "Foundation Summary" section and then go to the "Q&A" section at the end of the chapter. Otherwise, move to the next chapter.