(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/Leave 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 Leave message, improving the multicast service operating efficiency and user experience.

Setting the aging time for group members: After receiving a Report 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 IGMP 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 if the device receives an IGMP 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 to one receiver host and IGMPv2 packets can be processed.

The following steps are optional and can be performed in any order. Complete one or more steps as required. Default settings are recommended.

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

Procedure

Run system-view
The system view is displayed.
Perform either of the following operations to select VLAN or VPLS networking:
- 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** Rapid group member update
Function	Configuration Procedure	Description
Aging time for group members	Run the igmp-snooping query-interval query-interval command to set an interval at which a querier sends IGMP general query messages. Run the igmp-snooping robust-count robust-count command to set the number of times a querier sends IGMP group-specific query messages. Run the igmp-snooping max-response-time max-response-time command to set the maximum time for a downstream host to respond to a querier. Run the igmp-snooping lastmember-queryinterval lastmember-queryinterval command to set the interval at which a querier sends IGMP group-specific query messages.	After receiving an IGMP Report message from a downstream host, an interface calculates the aging time of a relevant group member based on the following formula: Aging time = robust-count x query-interval + max-response-time. When receiving an IGMP Leave message from a downstream host, an interface calculates the aging time of a relevant group member based on the following formula: robust-count x lastmember-queryinterval. An IGMPv1 host does not send a Leave message when leaving a multicast group. Therefore, the igmp-snooping lastmember-queryinterval command is valid only when IGMPv2 messages can be processed in the VLAN or VSI. If the querier receives a Report message within the robust-value x interval period, it continues to maintain the memberships for the group. Otherwise, the querier considers that there is no member of the group on the network segment and does not maintain the memberships for the group. The setting of robust-count, query-interval, max-response-time, and lastmember-queryinterval must be consistent on the Layer 2 device and its upstream Layer 3 device; otherwise, multicast data fails to be transmitted between Layer 2 and Layer 3 networks.
Prompt join	Run the l2-multicast fast-channel [ source-address source-address { mask \| mask-length } ] group-address group-address { mask \| 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 igmp-snooping prompt-leave [ group-policy { acl-number \| acl-name acl-name } ] command to configure prompt leave on member interfaces. By default, no member port is allowed to promptly leave a multicast group.	group-policy acl-number or group-policy acl-name acl-name specifies the range of multicast groups that member ports are allowed to promptly leave. If group-policy acl-number or group-policy acl-name acl-name is set and a Leave message is received from a member port, the member port is immediately deleted from the multicast routing table. Before setting acl-number or acl-name acl-name, configure an ACL to be referenced. The interface connected to user hosts filters Leave messages based on the ACL in the VLAN/VSI.

Run commit
The configuration is committed.