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13
Overview
Multicast Filtering
This chapter describes how to configure the following multicast services:
◆
IGMP Snooping
– Configures snooping and query parameters for IPv4.
◆
Filtering and Throttling
maximum of multicast groups allowed on an interface for IPv4.
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 that 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 to the hosts
which subscribed to this service.
Figure 202: Multicast Filtering Concept
This switch can use Internet Group Management Protocol (IGMP) to filter multicast
traffic. IGMP Snooping can be used to passively monitor or "snoop" on exchanges
between attached hosts and an IGMP-enabled device, most commonly a multicast
router. In this way, the switch can discover the ports that want to join a multicast
group, and set its filters accordingly.
If there is no multicast router attached to the local subnet, multicast traffic and
query messages may not be received by the switch. In this case IGMP Query can be
– Filters specified multicast service, or throttling the
Unicast
Flow
Multicast
Flow
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