Chapter 14
| Multicast Filtering
Layer 2 IGMP (Snooping and Query for IPv4)
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Static IGMP Host Interface – For multicast applications that you need to control
more carefully, you can manually assign a multicast service to specific interfaces on
the switch (page 548).
IGMP Snooping with Proxy Reporting – The switch supports last leave, and query
suppression (as defined in DSL Forum TR-101, April 2006):
◆ When proxy reporting is disabled, all IGMP reports received by the switch are
forwarded natively to the upstream multicast routers.
◆ Last Leave: Intercepts, absorbs and summarizes IGMP leaves coming from IGMP
hosts. IGMP leaves are relayed upstream only when necessary, that is, when the
last user leaves a multicast group.
◆ Query Suppression: Intercepts and processes IGMP queries in such a way that
IGMP specific queries are never sent to client ports.
The only deviation from TR-101 is that the marking of IGMP traffic initiated by the
switch with priority bits as defined in R-250 is not supported.
Note:
IGMP Query (Layer 2 or 3) – IGMP Query can be enabled globally at Layer 2,
but can be enabled for individual VLAN interfaces at Layer 3 (see “Configuring
IGMP Interface Parameters). However, note that Layer 2 query is disabled if Layer 3
query is enabled.
Configuring IGMP
Snooping and Query
Parameters
Use the Multicast > IGMP Snooping > General page to configure the switch to
forward multicast traffic intelligently. Based on the IGMP query and report
messages, the switch forwards multicast traffic only to the ports that request it. This
prevents the switch from broadcasting the traffic to all ports and possibly
disrupting network performance.
Command Usage
◆ IGMP Snooping – This switch can passively snoop on IGMP Query and Report
packets transferred between IP multicast routers/switches and IP multicast host
groups to identify the IP multicast group members. It simply monitors the IGMP
packets passing through it, picks out the group registration information, and
configures the multicast filters accordingly.
Note:
If unknown multicast traffic enters a VLAN which has been configured with a
router port, the traffic is forwarded to that port. However, if no router port exists on
the VLAN, the traffic is dropped if unregistered data flooding is disabled (default
behavior), or flooded throughout the VLAN if unregistered data flooding is enabled
(see “Unregistered Data Flooding” in the Command Attributes section).
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