igmp on-demand
Function
The igmp on-demand command enables the IGMP on-demand function on an interface. Then the IGMP multicast groups that the interface dynamically joins never time out.
The undo igmp on-demand command restores the default configuration.
By default, IGMP multicast groups that an interface dynamically joins are aged out when the timeout interval expires.
Usage Guidelines
Usage Scenario
In a standard IGMP working process, a querier sends General Query messages periodically and collects multicast membership information based on received Report and Leave messages. Multicast members respond to every Query message they receive. After IGMP on-demand is configured on the querier, the querier does not send Query messages, reducing IGMP packets exchanged between the querier and member hosts.
The IGMP on-demand function enables a querier to maintain multicast memberships based on requirements of members. The querier does not send Query messages to collect member information, reducing the number of IGMP messages exchanged between the querier and hosts.
IGMP on-demand applies only to IGMPv2 and IGMPv3.
Prerequisites
Multicast routing has been enabled using the multicast routing-enable command.
Configuration Impact
After the igmp on-demand command is executed on an interface (IGMP querier):
The interface does not send IGMP Query messages.
The entries of multicast groups that the interface dynamically joins never time out.
When the interface receives an IGMP Leave message, it deletes the corresponding IGMP entry.
