C
HAPTER
17
| Multicast Filtering
Layer 2 IGMP (Snooping and Query for IPv4)
– 608 –
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 614).
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.
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.
CLI REFERENCES
◆ "IGMP Snooping" on page 1192
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.
N
OTE
:
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).
◆ IGMP Querier – A router, or multicast-enabled switch, can periodically
ask their hosts if they want to receive multicast traffic. If there is more
than one router/switch on the LAN performing IP multicasting, one of
these devices is elected “querier” and assumes the role of querying the
LAN for group members. It then propagates the service requests on to
any upstream multicast switch/router to ensure that it will continue to
receive the multicast service.
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