MLD snooping proxying

As shown in Figure 84, to reduce the number of MLD report and done messages received by the upstream device, you can enable MLD snooping proxying on the edge device. With MLD snooping proxying enabled, the edge device acts as a host for the upstream MLD snooping querier to send MLD report and done messages to Device A. The host MLD report suppression mechanism on the edge device does not take effect. For more information about the MLD report suppression mechanism, see "Configuring MLD."

The MLD snooping proxy device processes different MLD messages as follows:

• General query.

  After receiving an MLD general query, the device forwards the query to all ports in the VLAN except the receiving port. The device also generates an MLD report based on the local membership information and sends the report to all router ports.

• Multicast-address-specific query or multicast-address-and-source-specific query.

  After receiving an MLD multicast-address-specific query or multicast-address-and-source-specific query, the device forwards the query to all ports in the VLAN except the receiving port. If the forwarding entry has a member port, the device sends a response to all router ports in the VLAN.

• Report.

  After receiving an MLD report from a host, the device looks up the forwarding table for a matching entry as follows:

  • If a match is found and the matching forwarding entry contains the receiving port, the device resets the aging timer for the port.

  • If a match is found but the matching forwarding entry does not contain the receiving port, the device adds the receiving port to the outgoing interface list. It also marks the receiving port as a dynamic member port and starts an aging timer for the port.

  • If no match is found, the device creates a forwarding entry with the receiving port as an outgoing interface. It also marks the receiving port as a dynamic member port and starts an aging timer for the port. Then it sends the report to all router ports.

• Done message.

  After receiving the MLD done message on a port, the device sends an MLD multicast-address-specific query through the receiving port. The device sends the MLD done message to all router ports only when the last member port is removed from the forwarding entry.