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Defining Multicast Global Parameters
Layer 2 switching forwards Multicast packets to all relevant VLAN ports by default, treating the packet as a
Multicast transmission. While this is functional, in the sense that all relevant ports/nodes receive a copy of
the frame, it is potentially wasteful as ports/nodes may receive irrelevant frames only needed by a subset of
the ports of that VLAN. Multicast forwarding filters enable forwarding of Layer 2 packets to port subsets,
defined in the Multicast filter database.
When IGMP snooping is enabled globally, the switching ASIC is programmed to forward all IGMP packets
to the CPU. The CPU analyzes the incoming packets and determines which ports are to join which Multicast
groups, which ports have Multicast routers generating IGMP queries, and what routing protocols are
forwarding packets and Multicast traffic. Ports requesting to join a specific Multicast group issues an IGMP
report specifying that Multicast group. This results in the creation of the Multicast filtering database.
The Multicast Global Parameters page contains fields for enabling IGMP Snooping on the device. To
open the Multicast Global Parameters page, click Switch→ Multicast Support→ Global Parameters in
the tree view.
Figure 7-55. Multicast Global Parameters
•
Bridge Multicast Filtering — Enables or disables bridge Multicast filtering. Disabled is the default
value. IGMP Snooping can be enabled only if Bridge Multicast Filtering is enabled.
•
IGMP Snooping Status — Enables or disables IGMP Snooping on the device. Disabled is the default
value.
Enabling Bridge Multicast Filtering on the Device
1 Open the Multicast Global Parameters page.
2 Select Enable in the Bridge Multicast Filtering field.
3 Click Apply Changes.
Bridge Multicast is enabled on the device.
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Configuring Device Information
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