Group Leave

Multicast listeners can opt to voluntarily leave a group by sending an IGMP (Internet Group Management Protocol) Leave message or by not responding to the periodic IGMP queries sent by the multicast router. Upon receiving an IGMP Leave message, the snooping switch sends a group specific query on the received port to solicit IGMP Reports from other interested hosts on the same network segment. The snooping switch waits for the interval specified by the last received query packet (max response time) to receive a response for the Leave query. If there is no response, the port is removed from the Layer 2 multicast forwarding entry. If no querier information is available, a configured value is used. If an IGMP Report is received, the entry remains the same.

Alternatively, the administrator can configure the snooping switch to remove the interface that received the IGMP Leave message from the Layer 2 multicast forwarding entry immediately upon processing the message. No IGMP Leave query is sent in this scenario. Configuring the immediate leave is useful in situations where instantaneous control of group registrations is required, which results in better bandwidth control.