user manual

System Configuration 3-53
From the host point of view, the snooping function listens at a port level for an IGMP report. The switch then
processes the IGMP report and starts forwarding the relevant multicast stream onto the host's port. When the
switch receives an IGMP leave message, it processes the leave message, and if appropriate stops the
multicast stream to that particular port. Basically, customer IGMP messages although processed by the switch
are also sent to the multicast routers.
In order for IGMP snooping to function with IGMP Version 3, it must always track the full source filter state of
each host on each group, as was previously done with Version 2 only when Fast Leave support was enabled.
To configure the IGMP options available in Motorola Netopia
®
Routers, select IGMP (Internet Group
Management Protocol) and press Return.
The IGMP Setup screen appears.
You can set the following options:
• IGMP Snooping – toggling this option to On enables the Motorola Netopia
®
Router to “listen in” to IGMP
traffic. The Router discovers multicast group membership for the purpose of restricting multicast
transmissions to only those ports which have requested them. This helps to reduce overall network traffic
from streaming media and other bandwidth-intensive IP multicast applications.
• Wireless M2U (Wireless Multicast-to-Unicast) – if IGMP Snooping is set to On, toggling this option to On
permits mapping an IP multicast to a wireless unicast. If IGMP Snooping is set to Off, this option does not
appear. Wireless M2U allows a higher wireless transmission rate to be used to "stream" IP multicast
packets. This mapping is limited to a single stream to a single client per group, otherwise the router will
revert to multicasting the stream immediately.
• Robustness – a way of indicating how sensitive to lost packets the network is. IGMP can recover from
robustness minus 1 lost IGMP packet. The default value is 2.
• Query Interval(s) – the amount of time in seconds between IGMP General Query messages sent by the
querier router. The default query interval is 125 seconds.
IGMP Setup
IGMP Snooping: On
Wireless M2U: Off
Robustness: 2
Query Interval(s): 125
Query Response Interval(deci-sec): 100
Unsolicited Report Interval(s): 10
IGMP Querier Version: v3
V2/V3 Settings...
Return/Enter accepts * Tab toggles * ESC cancels.