Enabling Fast Leave for IGMP V2

When a device receives an IGMP V2 leave message, it sends out multiple group-specific queries. If no other client replies within the waiting period, the device stops forwarding traffic. When fast leave version 2 is configured, and when the device receives a leave message, it immediately stops forwarding to that port. The device does not send group-specific queries. When fast leave version 2 is configured on a VLAN, you must not have multiple clients on any port that is part of the VLAN. In a scenario where two devices connect, the querier device should not be configured for fast leave version 2 because the port might have multiple clients through the non-querier. The number of queries, and the waiting period (in seconds) can be configured.

  1. Enter global configuration mode.
    device# configure terminal
  2. Configure a VLAN.
    device(config)# vlan 20
  3. Enable fast leave version 2 for IGMP.
    device(config-vlan-20)# multicast fast-leave-v2
  4. Configure the leave message waiting period, in seconds.
    device(config-vlan-20)# ip multicast leave-wait-time 4
    The default waiting period is 2 seconds.

The following example enables fast leave for IGMP with a leave message waiting period of 4 seconds.

device# configure terminal
device(config)# vlan 20
device(config-vlan-20)# multicast fast-leave-v2
device(config-vlan-20)# ip multicast leave-wait-time 4