Configuring IGMP Fast Leave

Context

In some scenarios, a querier interface connects to only one receiver host. If the host frequently switches between multiple multicast groups, you can configure the fast leave function on the interface so that the interface can quickly respond to Leave messages sent from the host.

After the fast leave function is configured, the querier does not send a Group-Specific Query message after receiving a Leave message from the host. Instead, the querier directly notifies the upstream multicast device that the host has left the multicast group. The fast leave function reduces delay in response to Leave messages and saves network bandwidth.

IGMP fast leave applies only to IGMPv2 and IGMPv3.

The fast leave function can be configured in the IGMP view or interface view.

Configuration in the IGMP view is valid globally, whereas configuration in the interface view is valid only for the specific interface.
If the fast leave function is configured in both the interface view and IGMP view, the configuration in the interface view takes precedence over the configuration in the IGMP view. If the fast leave function is not configured on an interface, the interface uses the configuration in the IGMP view.
If non-default configuration is made in the IGMP view, the default configuration in the interface view does not take effect.

Procedure

Configuring IGMP fast leave globally
1. Run system-view
  The system view is displayed.
2. Run igmp [ vpn-instance vpn-instance-name ]
  The IGMP view is displayed.
3. Run prompt-leave [ group-policy acl-number ]
  Fast leave is configured globally.
  
  By default, the switch sends a Group-Specific Query message after receiving a Leave message.
  
  When configuring an access control list (ACL) for an interface, use the permit parameter to allow the hosts to quickly leave multicast groups with addresses in a specified range. If no rule is configured in the ACL, the hosts cannot fast leave any multicast groups.
Configuring IGMP fast leave on an interface
1. Run system-view
  The system view is displayed.
2. Run interface interface-type interface-number
  The interface view is displayed.
3. (Optional) On an Ethernet interface, run undo portswitch
  The interface is switched to Layer 3 mode.
  
  By default, an Ethernet interface works in Layer 2 mode.
  
  Only the S5720-EI, S5720-HI, S5730-HI, S5731-H, S5731-S, S5731S-H, S5731S-S, S5732-H, S6720-EI, S6720-HI, S6720S-EI, S6730-H, S6730S-H, S6730-S, and S6730S-S support switching between Layer 2 and Layer 3 modes.
4. Run igmp prompt-leave [ group-policy acl-number ]
  Fast leave is configured on the interface.
  
  By default, the switch sends a Group-Specific Query message after receiving a Leave message.