User Guide
139
the member port that corresponds to the host expires, the switch immediately deletes its forwarding entry
from the forwarding table.
When an IGMPv2 or IGMPv3 host leaves a multicast group, it sends an IGMP leave message to the
multicast router to inform of such leave.
When receiving an IGMP leave message from the last member port, the switch forwards it through all
router ports in the VLAN and resets the aging timer on the receiving port (the port that received the IGMP
leave message) instead of immediately deleting its corresponding forwarding entry from the forwarding
table as it cannot know whether there are still other members of that multicast group attached to such
port.
After receiving the IGMP leave message from a host, the IGMP querier resolves the multicast group
address in the message and sends an IGMP group-specific query to that multicast group through the port
that received the leave message. After receiving the IGMP group-specific query, the switch forwards it
through all its router ports in the VLAN and all member ports for that multicast group.
The switch also performs the following actions on the port that received the IGMP leave message: If the
port receives any IGMP membership report in response to the group-specific query before the aging timer
expires, the switch considers that some host attached to the port is receiving or expecting to receive
multicast data from that multicast group and will reset the aging timer on the port.
If the port receives no IGMP membership report in response to the group-specific query before its aging
timer expires, the switch considers that no hosts attached to the port are still members of that multicast
group address and thus removes the multicast forwarding entry that the port corresponds to from the
forwarding table when the aging timer expires.
IGMP Snooping
To config IGMP Snooping settings, click Device Management -> IGSP -> IGMP Snooping.
Fields on the screen are described below:
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