(Optional) Configuring Rapid Group Member Information Update

Rapid group member information update can be configured to enable devices to quickly update Layer 2 multicast entries generated based on Report/Done messages received from group members, improving the multicast data forwarding efficiency.

Context

After rapid group member information update is configured on a device, the device can quickly respond to a received a Join or Done message, improving user experience. Using this feature, the device implements the following functions:

Setting the aging time of group members: After receiving a Report/Done message for a multicast group from a host, the device creates an entry. The entry ages out after a period of time. The aging time of entries should be properly set so that the device can update Layer 2 multicast entries in time. This improves system performance.
Prompt join: After the prompt join function is enabled on a device, the device applies for resources for multicast groups in advance. When the device receives an MLD Report message for a multicast group, it can immediately forward multicast data for the multicast group, improving the speed at which hosts join the multicast group and shortening the delay for the device to respond to the Report message.
Prompt leave: After prompt leave is enabled on a device and the device receives an MLD Leave for a multicast group, the device will immediately delete the entry of the multicast group without waiting for the age timer to expire.

Prompt leave applies only to a VLAN or VSI in which each interface is attached only to one receiver.

The following functions are optional and can be configured in any order. Default settings are recommended.

Before configuring rapid group member information update, enable IGMP snooping both globally and in a VLAN or VSI view.

Procedure

Run system-view
The system view is displayed.
Perform either of the following operations based on the VLAN or VPLS networking scenario:
- Run the vlan vlan-id command to enter the VLAN view.
- Run the vsi vsi-name [ static ] command to enter the VSI view.

The steps listed in Table 1 can be performed in any order. Complete one or more steps as required.

**Table 1** Configuring rapid group member update
Function	Configuration Procedure	Description
Setting the aging time of group members	Run the mld-snooping query-interval query-interval command to set an interval at which a querier sends general Query messages. Run the mld-snooping robust-count robust-count command to set the number of group-specific Query messages that a querier sends. Run the mld-snooping max-response-time max-response-time command to set the maximum time for a querier to wait for responses from downstream hosts. Run the mld-snooping lastmember-queryinterval lastmember-queryinterval command to set an interval at which a querier sends group-specific Query messages.	After receiving an MLD Report message from a downstream host, the device sets the member interface aging time based on following formula: Member interface aging time = robust-count x query-interval + max-response-time. After receiving an MLD Done message from a downstream host, the device sets the member interface aging time based on the following formula: Member interface aging time = robust-count x lastmember-queryinterval. If the querier receives a Report message for the multicast group from another host within the robust-count x lastmember-queryinterval period, it continues to maintain the member interface information for the group. If the querier does not receive a Report message for the multicast group within this period, the querier considers that there is no member of the group on the network segment, and does not maintain the member interface information for the group. Set the same interface aging parameter values as those specified on its upstream device. Otherwise, multicast data transmission will be interrupted between the Layer 2 and Layer 3 devices.
Prompt join	Run the l2-multicast ipv6 fast-channel [ source-address source-address mask-length ] group-address group-address mask-length command to configure prompt join.	After prompt join is configured, the device will reserve system resources for a specific multicast group. As a result, if there is no member of this multicast group, system performance will be affected.
Prompt leave	Run the mld-snooping prompt-leave [ group-policy { acl6-number \| acl6-name acl6-name } ] command to configure prompt leave in a VLAN or VSI for member interfaces.	group-policy acl6-number or group-policy acl6-name acl6-name specifies the range of multicast groups that prompt leave is enabled. If group-policy acl6-number or group-policy acl6-name acl6-name is set and a Done message is received from the VLAN or VSI, the member interface is immediately deleted from the multicast routing table. Before setting acl6-number or acl6-name acl6-name, configure rules for the ACL to be referenced. Member interfaces in the VLAN/VSI then filter Done messages based on the ACL.

Run commit
The configuration is committed.