User's Manual

IGMP Configuration
103
5
an interface if it is connected to only one IGMP-enabled device, either a service
host or a neighbor running IGMP snooping.
This attribute is only effective if IGMP snooping is enabled, and IGMPv2 snooping
is used.
• Router Timeout – This function is used to see if IGMP query packets are arriving
from the WAN side at regular intervals, and indicates the time the Gateway waits
after the querier stops before it considers it to have expired. (Option: 0, 1, 5, 10,
20, 30 minutes; Default: 0 minutes, which means that detection is disabled)
If no queries have been detected for the specified time, the Gateway stops
forwarding multicast traffic to downstream clients.
• IGMP Timeout – The function is used to see the IGMP report (join) packets are
arriving from the LAN side at regular intervals, and indicates the time the Gateway
waits after these messages have stopped before it considers there to be no more
downstream clients. (Options: 0, 1, 5, 10, 20, 30 minutes; Default: 0 minutes, which
means that detection is disabled)
If no report message have been detected for the specified time, the Gateway stops
forwarding multicast traffic to downstream clients.
When an IGMPv2 or v3 multicast host leaves a group, it sends an IGMP leave
message. When the leave message is received by the Gateway, it checks to see
if this host is the last to leave the group by sending out an IGMP group-specific or
group-and-source-specific query message, and starts a timer. If no reports are
received before the timer expires, the group record is deleted, and a report is sent
to the upstream multicast router.
Since IGMPv1 clients do not send leave packets, both Router Timeout and IGMP
Timeout are required to maintain multicast flows to IGMPv1 clients.
This attribute will take effect only if Fast Leave is enabled.