Jul 08,2008 00:00
With IGMP fastleave enabled, the switch removes the port from the multicast forwarding table without sending a MAC-based query to the port. The purpose behind fastleave is to quickly transition the port or VLAN off the multicast stream. Most customers have not deployed fastleave today. Fastleave should not be enabled on ports that have hubs connected to them. For example, two hosts are off the same hub, which is connected to a port on a Catalyst switch with IGMP fastleave enabled. If one host leaves, the switch immediately takes the port off the multicast forwarding table. As a result, the second host on the hub will lose its multicast traffic. IGMP fastleave is disabled on trunk ports.