Dell PowerSwitch S4820T Configuration Guide for the S4820T System 9.14.1.0 - Page 374

still receives no response, the querier removes the group from the list associated with forwarding port and stops forwarding traffic for that group to the subnet. IGMP Version 3 Conceptually, IGMP version 3 behaves the same as version 2. However, there are differences. • Version 3 adds the ability to filter by multicast source, which helps multicast routing protocols avoid forwarding traffic to subnets where there are no interested receivers. • To enable filtering, routers must keep track of more state information, that is, the list of sources that must be filtered. An additional query type, the Group-and-Source-Specific Query, keeps track of state changes, while the Group-Specific and General queries still refresh the existing state. • Reporting is more efficient and robust: hosts do not suppress query responses (non-suppression helps track state and enables the immediate-leave and IGMP snooping features), state-change reports are retransmitted to insure delivery, and a single membership report bundles multiple statements from a single host, rather than sending an individual packet for each statement. The version 3 packet structure is different from version 2 to accommodate these protocol enhancements. Queries are still sent to the allsystems address 224.0.0.1, as shown in the following illustration, but reports are sent to the all IGMP version 3-capable multicast routers address 244.0.0.22, as shown in the second illustration. Figure 46. IGMP Version 3 Packet Structure 374 Internet Group Management Protocol (IGMP)