307
•
If a match is found but the receiving port is not in the forwarding entry, the switch directly
discards the MLD done message.
•
If a match is found and the receiving port is in the forwarding entry, the switch forwards the done
message to all router ports in the native VLAN. Without knowing whether any other hosts
attached to the port are still listening to that IPv6 multicast group address, the switch does not
immediately remove the port from the forwarding entry for that group. Instead, it restarts the
aging timer for the port.
After receiving the MLD done message, the MLD querier resolves the IPv6 multicast group address
in the message. Then, it sends an MLD multicast-address-specific query to that IPv6 multicast group
through the port that received the MLD done message.
After receiving the MLD multicast-address-specific query, the switch forwards it through all its router
ports in the VLAN and all member ports of the IPv6 multicast group. Then, it waits for the responding
MLD reports from the directly connected hosts to check for the existence of members for the IPv6
multicast group. For the port that receives the done message (assuming that it is a dynamic member
port), the Layer 2 device also performs one of the following actions:
•
If the port receives an MLD report before the aging timer expires, the switch restarts the aging
timer for the port.
•
If the port does not receives any MLD report when the aging timer expires, the switch removes
the port from the forwarding entry for the IPv6 multicast group.
MLD snooping proxying
You can configure the MLD snooping proxying function on an edge device to reduce the number of
MLD reports and done messages sent to its upstream device. The device configured with MLD
snooping proxying is called an MLD snooping proxy. It is a host from the perspective of its upstream
device.
NOTE:
Even though an MLD snooping proxy is a host from the perspective of its upstream device, the MLD
report suppression mechanism for hosts does not take effect on it. For more information about the
MLD report suppression mechanism for hosts, see "
Figure 91 Network diagram
As shown in
, Switch A works as an MLD snooping proxy. As a host from the perspective of
the querier Router A, Switch A represents its attached hosts to send their membership reports and
done messages to Router A.
