Leaving A Multicast Group - Cisco Catalyst 3650 Configuration Manual

IGMP Snooping
table directs IGMP messages only to the CPU, the message is not flooded to other ports on the device. Any
known multicast traffic is forwarded to the group and not to the CPU.
Figure 2: Second Host Joining a Multicast Group
Table 6: Updated IGMP Snooping Forwarding Table
Destination Address
224.1.2.3
Related Topics
Configuring the Device as a Member of a Group (CLI), on page 34
Example: Configuring the Device as a Member of a Multicast Group, on page 81

Leaving a Multicast Group

The router sends periodic multicast general queries, and the device forwards these queries through all ports
in the VLAN. Interested hosts respond to the queries. If at least one host in the VLAN wants to receive
multicast traffic, the router continues forwarding the multicast traffic to the VLAN. The device forwards
multicast group traffic only to those hosts listed in the forwarding table for that IP multicast group maintained
by IGMP snooping.
When hosts want to leave a multicast group, they can silently leave, or they can send a leave message. When
the device receives a leave message from a host, it sends a group-specific query to learn if any other devices
connected to that interface are interested in traffic for the specific multicast group. The device then updates
the forwarding table for that MAC group so that only those hosts interested in receiving multicast traffic for
the group are listed in the forwarding table. If the router receives no reports from a VLAN, it removes the
group for the VLAN from its IGMP cache.
IP Multicast Routing Configuration Guide, Cisco IOS XE Release 3SE (Catalyst 3650 Switches)
30
Type of Packet
IGMP
Configuring IGMP
Ports
1, 2, 5
OL-29890-01