Configuring the fast leave processing removes the interface from the forwarding table as soon as the switch receives a leave message from the interface (that is, the switch refrains from sending MAC-based general queries over the interface). The VLAN interface is pruned from the multicast tree for the multicast group specified in the original leave message. Configuring the immediate-leave processing ensures optimal bandwidth management for all of the hosts on a switched network, even when multiple multicast groups are simultaneously in use. You can use the same instructions to enable or disable the leave process to immediate. Before you can configure IGS features, you must configure your network environment, as described in Topology Example.