Summit WM3000 Series Controller System Reference Guide 231
IGMP snooping allows the controller to manage multicast traffic based on groups of IGMP hosts on a
per-portal basis. IGMP snooping keeps track of hosts interested in a multicast group and on the portal it
is associated and forwards multicast packets to portal on which the host is connected.
In the case of IP multicast traffic, an IGMP supported controller provides the benefit of conserving
bandwidth on those network segments where no node has expressed interest in receiving packets
addressed to the group address. This is in contrast to normal controller behavior, where multicast traffic
is typically forwarded on all interfaces.
IGMP basically operates as follows:
● One router periodically broadcasts IGMP query messages onto a link
● Hosts respond to the query messages by sending IGMP report messages indicating their group
memberships
● All routers receive the report messages and note the memberships of hosts on the link
● If a router doesn't receive a report message for a particular group for a period of time, the router
assumes there are no more members of the group on the link
The IGMP Snooping screen is partitioned into two tabs supporting the following activities:
● IGMP Snooping Configuration
● IGMP Snoop Querier Configuration
IGMP Snooping Configuration
To view and configure IGMP snooping:
1 Select Network > IGMP Snooping from the main menu tree.
2 Select the IGMP Snoop Config tab.
3 Optionally select the Snoop Enable option.
When IGMP snooping is enabled, the controller analyses all the IGMP packets between hosts
connected to the controller and multicast routers. When a controller hears an IGMP report from a
host for a given multicast group, the controller adds the host's port number to the multicast list for
that group. When the controller hears an IGMP leave, it removes the host's port from the table entry.
When enabled, a green checkmark displays as opposed to a red “X” designating the snoop as
disabled.
4 Optionally select the Unknown Multicast Forward option.
This will allow the broadcast of multicast traffic to all the ports in a broadcast domain (LANs),
regardless of whether the hosts were interested in that traffic or not.
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