Cisco 500 Series Administration Manual page 317

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By default, all Multicast frames are flooded to all ports of the VLAN. It is possible to
selectively forward only to relevant ports and filter (drop) the Multicast on the rest
of the ports by enabling the Bridge Multicast filtering status in the Multicast >
Properties page.
If filtering is enabled, Multicast frames are forwarded to a subset of the ports in the
relevant VLAN as defined in the Multicast Forwarding Data Base (MFDB). Multicast
filtering is enforced on all traffic.
A common way of representing Multicast membership is the (S,G) notation where
S is the (single) source sending a Multicast stream of data, and G is the IPv4 or IPv6
group address. If a Multicast client can receive Multicast traffic from any source of
a specific Multicast group, this is saved as (*,G).
You can configure one of the following ways of forwarding Multicast frames:
• MAC Group Address—Based on the destination MAC address in the
Ethernet frame.
One or more IP Multicast group addresses can be mapped to a
NOTE
MAC group address. Forwarding, based on the MAC group address, can
result in an IP Multicast stream being forwarded to ports that have no
receiver for the stream.
• IP Group Address—Based on the destination IP address of the IP packet
(*,G).
• Source Specific IP Group Address—Based on both the destination IP
address and the source IP address of the IP packet (S,G).
(S,G) is supported by IGMPv3 and MLDv2, while IGMPv1/2 and MLDv1 support
only (*.G), which is just the group ID.
The device supports a maximum of 256 static and dynamic Multicast group
addresses.
Only one of filtering options can be configured per VLAN.
Cisco 500 Series Managed Switch Administration Guide
Multicast
Multicast Forwarding