MLD Snooping Configuration

introduction introduction mld snooping (multicast listener discovery snooping) is an ipv6 layer 2 multicast protocol in an ipv6 network, to avoid wasting bandwidth by broadcasting multicast packets within a local area network (lan), mld snooping can be deployed in the layer 2 network to achieve precise forwarding of multicast packets similar to an ipv4 multicast network, layer 2 multicast devices can listen to and analyze mld messages between multicast users and upstream routers based on this information, the devices establish layer 2 multicast forwarding entries to control the forwarding of multicast data packets explanation of principles explanation of principles the specific handling of different mld actions by switches running mld snooping is as follows general group query messages when the switch receives mld general group query messages, it forwards them out through all ports in the vlan except the receiving port for the receiving port, the switch handles it as follows if the dynamic router port is already included in the router port list, its aging timer is reset if the dynamic router port is not yet included in the router port list, it is added to the router port list, and its aging timer is started mld report messages a host will send an mld report message to the mld querier in the following two situations when a member host of a multicast group receives an mld query message, it responds with an mld membership report message if a host wants to join a multicast group, it proactively sends an mld membership report message to the mld querier to declare its membership in the multicast group when the switch receives an mld membership report message, it forwards the message through all router ports within the vlan, parses the multicast group address that the host wants to join from the message, and processes the receiving port as follows if there is no forwarding entry corresponding to the multicast group, it creates a forwarding entry, adds the port as a dynamic member port to the outgoing port list, and starts its aging timer if there is an existing forwarding entry for the multicast group, but the outgoing port list does not include the port, it adds the port as a dynamic member port to the outgoing port list and starts its aging timer if there is an existing forwarding entry for the multicast group and the outgoing port list already includes the dynamic member port, it resets the aging timer leaving multicast groups when a host leaves a multicast group, it sends an mld leave group message to inform the multicast router that it has left a specific multicast group if the switch does not have a forwarding entry for the multicast group, or if the outgoing port list for the multicast group does not include the port, the switch will not forward the message to any port and will discard it if there is a forwarding entry for the multicast group and the outgoing port list for the multicast group includes the port, the switch will forward the message through all router ports within the vlan since the switch does not know whether there are other members of the multicast group on the receiving port, it will not immediately remove the port from the outgoing port list of the forwarding entry for the multicast group but will reset its aging timer mld snooping configuration mld snooping configuration configuring basic mld snooping functionality configuring basic mld snooping functionality operation command description enter the vlan view vlan id enable mld snooping function mld snooping enable enable mld snooping querier mld snooping querier enable configure the source address for mld queries mld snooping querier ip ip address configuring mld snooping port aging time configuring mld snooping port aging time after receiving different mld protocol messages, the device starts aging timers for member ports with different durations when member ports of the device receive report messages from downstream hosts, the port aging time is set to robustness factor × general query interval + maximum response time when member ports of the device receive leave messages from downstream hosts, the port aging time is set to specific query interval × robustness factor operation command description enter the vlan view vlan id configure the mld snooping general query interval mld snooping query interval value configure the mld snooping maximum response time mld snooping query max response time value configure the mld snooping specific query interval mld snooping last member query interval value configure the mld snooping robustness factor mld snooping robustness value enabling fast leave on member interfaces enabling fast leave on member interfaces fast leave on a port means that when the switch receives an mld leave message from a host indicating it is leaving a multicast group, the switch immediately removes that port from the outgoing port list for the corresponding forwarding table entry subsequently, when the switch receives a specific mld query message for that multicast group, it will no longer forward it out of that port operation command description enter the interface view interface ethernet id enable fast leave on member interface prompt leave enable enabling mld snooping proxy function enabling mld snooping proxy function when there are numerous member hosts in the network or when member hosts frequently join/leave multicast groups, a large number of mld join/leave messages may be generated, resulting in significant processing pressure on the access devices to reduce the number of mld join and leave messages received by upstream devices, mld snooping proxy functionality can be configured on edge devices to allow them to act as proxies for downstream hosts to send join and leave messages to upstream devices handling of join messages upon receiving a join message for a multicast group on a port, if a forwarding table entry exists for that group and its outgoing port list already includes the dynamic member port, reset the aging timer for that entry if a forwarding table entry exists for the multicast group but its outgoing port list does not include the port, add the port as a dynamic member port to the outgoing port list and start its aging timer if no forwarding table entry exists for the multicast group on the device, create one, add the port as a dynamic member port to the outgoing port list, start its aging timer, and send a report message for that group to all router ports handling of leave messages upon receiving a leave message for a multicast group on a port, send a specific query message for that group to the port only send a leave message for the group to all router ports when removing the last member port from the corresponding forwarding table entry for that multicast group handling of general group query messages upon receiving a general group query message, forward it to all ports in the vlan except the receiving port generate report messages based on locally maintained group membership relationships and forward them to all router ports simultaneously operation command description enter the vlan view vlan id enable mld snooping function mld snooping enable enable mld snooping proxy function mld snooping proxy enable