Configuring Multicast Forwarding
Defining Multicast Properties
Cisco Small Business 200 1.1 Series Smart Switch Administration Guide 197
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Defining Multicast Properties
The Properties page enables you to configure the Bridge Multicast filtering status.
By default, all Multicast frames are flooded to all ports of the VLAN. To selectively
forward only to relevant ports and filter (drop) the Multicast on the rest of the ports,
enable Bridge Multicast filtering status in the 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. Multicast filtering
is enforced on all traffic. By default, such traffic is flooded to all relevant ports, but
you can limit forwarding to a smaller subset.
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 written as (*,G).
The following are ways of forwarding Multicast frames:
• MAC Group Address—Based on the destination MAC address in the
Ethernet frame.
NOTE As mentioned before, one or more IP Multicast group addresses
can be mapped to a 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).
By selecting the forwarding mode, you can define the method used by hardware
to identify Multicast flow by one of the following options: MAC Group Address, IP
Group Address, or Source Specific IP Group Address.
(S,G) is supported by IGMPv3 and MLDv2, while IGMPv1/2 and MLDv1 support
only (*.G), which is just the group ID.
The switch supports a maximum of 256 static and dynamic Multicast group
addresses.
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