Accton Technology 4508, CheetahSwitch Workgroup manual Igmp Multicast Filtering, Configuring Igmp

Management Guide

IGMP Multicast Filtering

Multicasting is used to support real-time applications such as video conferencing or streaming audio. A multicast server does not have to establish a separate connection with each client. It merely broadcasts its service to the network, and any hosts which want to receive the multicast register with their local multicast switch/router. Although this approach reduces the network overhead required by a multicast server, the broadcast traffic must be carefully pruned at every multicast switch/router it passes through to ensure that traffic is only passed on the hosts which subscribed to this service.

This switch uses IGMP (Internet Group Management Protocol) to query for any attached hosts who want to receive a specific multicast service. The switch looks up the IP Multicast Group used for this service and adds any port which received a similar request to that group. It then propagates the service request on to any neighboring multicast switch/router to ensure that it will continue to receive the multicast service. (For more information, see “IGMP Snooping and IP Multicast Filtering” in Chapter 4.)

Configuring IGMP

This protocol allows a host to inform its local switch/router that it wants to receive transmissions addressed to a specific multicast address group. Use the IGMP Configuration screen to set key parameters for multicast filtering as shown below.

Parameter	Description
IGMP Status	If enabled, the switch will monitor network traffic to determine which
	hosts want to receive multicast traffic.
Act as IGMP Querier	If enabled, the switch can serve as the “querier,” which is responsible
	for asking hosts is they want to receive multicast traffic. (Not available
	for the current firmware release.)
IGMP Query Count	The maximum number of queries issued for which there has been no
	response before the switch takes action to solicit reports.
IGMP Report Delay	The time (in minutes) between receiving an IGMP Report for an IP
	multicast address on a port before the switch sends an IGMP Query
	out that port and removes the entry from its list.

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