54
Figure 22 Network diagram for MLD snooping proxying
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.
Table 9 MLD message processing on an MLD snooping proxy
MLD
message
Actions
General query
When receiving an MLD general query, the proxy forwards it to all ports but the receiving
port. In addition, the proxy generates a report according to the group memberships it
maintains and sends the report out all router ports.
Multicast-addre
ss-specific
query
In response to the MLD group-specific query for a certain IPv6 multicast group, the proxy
sends the report to the group out all router ports if the forwarding entry for the group still
contains a member port.
Report
When receiving a report for an IPv6 multicast group, the proxy looks up the multicast
forwarding table for the entry for the multicast group. If the forwarding entry is found with
the receiving port contained as a dynamic port in the outgoing port list, the proxy resets
the aging timer for the entry. If the forwarding entry is found but the outgoing port list
does not include the receiving port, the proxy adds the port to the outgoing port list as a
dynamic member port and starts an aging timer for it. If no forwarding entry is found, the
proxy creates the entry, adds the receiving port to the outgoing port list as a dynamic
member port and starts an aging timer for the port, and then, sends a report to the group
out all router ports.
Done
In response to a done message for an IPv6 multicast group, the proxy sends a
multicast-address-specific query for the group out the receiving port. After making sure
that no member port is contained in the forwarding entry for the IPv6 multicast group, the
proxy sends a done message for the group out all router ports.
Protocols and standards
•
RFC 4541,
Considerations for Internet Group Management Protocol (IGMP) and Multicast
Listener Discovery (MLD) Snooping Switches
MLD snooping configuration task list
Complete these tasks to configure MLD snooping: