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Chapter 2

IP Multicast in a Campus Network

Multicast Campus Deployment Recommendations

Multicast Campus Deployment Recommendations

This chapter discusses the recommended and optional configurations for IP multicast campus deployment. The recommended guidelines are summarized below:

Use IP multicast to scale streaming applications, such as MoH and IP/TV. Use administratively scoped addresses to differentiate multicast applications by type and bandwidth. Use Anycast RP when high availability and load balancing are needed. Understand and deploy the correct features to support filtering of non-RPF traffic in the hardware. Understand and correctly deploy HSRP when used with IP multicast deployment.

Select Catalyst switches that have IGMP snooping and use CGMP in low-end switches that do not support IGMP snooping.

Use recommended commands to ensure that the correct RPs and sources are used. Use IP multicast boundaries to control where certain multicast streams go.

Use “show” commands to ensure proper operation of the multicast configurations and enable SNMP traps to log multicast events.

Campus Deployment

This section provides information for deploying the following IP multicast elements in a campus network:

IGMP Snooping and CGMP Non-RPF Traffic HSRP

IGMP Snooping and CGMP

In addition to PIM, IP multicast uses the host signaling protocol IGMP to indicate that there are multicast receivers interested in multicast group traffic.

Internet Group Management Protocol (IGMP) snooping is a multicast constraining mechanism that runs on a Layer 2 LAN switch. IGMP snooping requires the LAN switch to examine some Layer 3 information (IGMP join/leave messages) in the IGMP packets sent between the hosts and the router. When the switch hears the “IGMP host report” message from a host for a multicast group, it adds the port number of the host to the associated multicast table entry. When the switch hears the “IGMP leave group” message from a host, the switch removes the host entry from the table.

Because IGMP control messages are sent as multicast packets, they are indistinguishable from multicast data at Layer 2. A switch running IGMP snooping must examine every multicast data packet to determine if it contains any pertinent IGMP control information. Catalyst switches that support IGMP snooping use special Application Specific Integrated Circuits (ASICs) that can perform the IGMP checks in hardware.

Cisco AVVID Network Infrastructure IP Multicast Design



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