Configuring IGMP Fast Leave
Context
In some scenarios (ADSL dial-up for example), a querier interface connects to only one receiver host. If the host frequently switches between multiple multicast groups (for example, it switches TV channels frequently), 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.
Procedure
- Run system-view
The system view is displayed.
- Run interface interface-type interface-number
The interface view is displayed.
- Run igmp prompt-leave [ group-policy { acl-number | acl-name acl-name } ]
Fast leave is configured on the interface.
By default, the router sends a Group-Specific Query message after receiving a Leave message.
When configuring an ACL rule for an interface, use the permit parameter to allow the hosts connected to the interface to quickly leave multicast groups with addresses in a specified range. If no rule is configured in the ACL, the hosts connected to the interface cannot fast leave any multicast groups.
