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Management Guide
3-25
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.