7.4.6 Configuring a Router to Be a Member of a Group In some cases, it is necessary to configure multicast traffic to go to a segment where there is no group member or when a host on that segment cannot report its group membership using IGMP. You can configure Cisco routers to be members of a multicast group, which is useful for determining multicast reachability in a network. If a device is configured to be a group member and supports the protocol that is being transmitted to the group, it can respond (for example, the ping command). The device responds to IGMP echo request packets addressed to a group of which it is a member. The following are two ways to pull multicast traffic down to a network segment. These commands are often used in lab environments where no multicast servers and receivers are configured. Figure displays a sample configuration of a router joining a multicast group and enabling IGMP by using the ip igmp join-group command in interface configuration mode.
Content 7.4 Multicast Configuration and Verification 7.4.7 Configure a Router as a Statically Connected Member To configure the router to be a statically connected member of a group (and allow fast switching), use the ip igmp static-group command shown in Figure in interface configuration mode. Use the show ip igmp interface command to display the multicast groups that are directly connected to the router and that were learned via IGMP. This command is used to determine the following information: In Figure , the router itself joins these two groups: Use the show ip igmp groups command to display the multicast groups that are directly connected to the router and that were learned via IGMP. In Figure , the router recognizes these two multicast groups:
Content 7.4 Multicast Configuration and Verification 7.4.8 Verifying IGMP Snooping When verifying IGMP snooping on a switch, use the show ip igmp snooping command to display the snooping configuration information for all VLANs on the switch or for a specified VLAN. Notice that IGMP snooping is enabled by default globally and on a per-VLAN basis on SW1. In this case, IGMP snooping identifies a switchport as a multicast router port only if it see PIM or DVMRP messages sent towards the switch on that port. Figure provides sample output generated by the show ip igmp snooping on a Catalyst 4000 switch. Therefore, the format of the output will differ depending on the model of Catalyst switch. You can also use the show mac-address-table multicast command to display the entries in the MAC address table for a VLAN that has IGMP snooping enabled.
Content 7.5 Multicast Lab Exercises 7.5.1 Lab 7-1 Implementing IGMP and IGMP Snooping Lab Activity

Lab Exercise: Lab 7-1 Implementing IGMP and IGMP Snooping Configure IGMP to listen to the multicast group 229.7.7.7 on R2 and R3. Send multicast traffic from R1 to the LAN segment. Configure IGMP snooping to efficiently send multicast traffic through the switch. Review IGMP, PIM-DM, and IGMP snooping in your course materials before completing this lab.
Content 7.5 Multicast Lab Exercises 7.5.2 Lab 7-2 Routing IP Multicast with PIM Dense Mode Lab Activity

Lab Exercise: Lab 7-2 Routing IP Multicast with PIM Dense Mode Configure IGMP to listen to the multicast group 229.7.7.7 on R2 and R3. Send multicast traffic from R1 to the LAN segment. Configure IGMP snooping to efficiently send multicast traffic through the switch. Review IGMP, PIM-DM, and IGMP snooping in your course materials before completing this lab.
Content 7.5 Multicast Lab Exercises 7.5.3 Lab 7-3 Routing IP Multicast with PIM Sparse Mode Lab Activity

Lab Exercise: Lab 7-3 Routing IP Multicast with PIM Sparse Mode Your successful assistance in configuring IP multicast routing has allowed CrushASodaCan.com to become a community action organization with a wide base of interested citizens. Because of your help, the organization can now preview their TV commercials via the network before releasing them to the public. CrushASodaCan.com also projects high growth rates in terms of volunteer workers using their network. Unfortunately, the flooding and pruning with PIM-DM that you configured for them cannot handle the new demands being made on the network. So they have hired you again as a consultant to solve this. You decide to implement PIM Sparse Mode (PIM-SM) to create a subscription-based multicast topology in CrushASodaCan.com’s network.
Content 7.5 Multicast Lab Exercises 7.5.4 Lab 7-4 Routing IP Multicast with PIM Sparse-Dense Mode Lab Activity

Lab Exercise: Lab 7-4 Routing IP Multicast with PIM Sparse-Dense Mode After the incredible community response to CrushASodaCan.com TV spots, a skeptical citizen began questioning the usefulness of crushing aluminum cans before recycling them. After conducting a thorough case study, he founded the organization JustRecycleTheCan.org, and began producing TV announcements encouraging citizens to recycle but informing them that it is unnecessary to crush cans before committing them to the safe care of a recycle bin.

The founder of JustRecycleTheCan.org has contracted you to implement multicast on his network so that he can also preview TV spots before releasing them to the public. However, he requests that you implement PIM in a more redundant, scalable manner than you did for CrushASodaCan.com.

Fully configure multicast routing on his network according to the requests of the founder of the organization. Verify that if the route to the rendezvous point (RP) is lost, multicast receivers on remote networks can still receive multicast streams.